:<small>Your FACE is a crappy answer. :-P -<b><font color="black">[[User:Runningonbrains|Running]]</font><font color="blue">[[WP:METEO|On]]</font><font color="green">[[User talk: Runningonbrains|Brains]]</font></b> 19:00, 23 February 2009 (UTC)</small>
:<small>Your FACE is a crappy answer. :-P -<b><font color="black">[[User:Runningonbrains|Running]]</font><font color="blue">[[WP:METEO|On]]</font><font color="green">[[User talk: Runningonbrains|Brains]]</font></b> 19:00, 23 February 2009 (UTC)</small>
::: [[Wikipedia:No Ignoring Helpful Emoticons Indicating That Someone Is Using Humour To Point Out Where You Have Been Unnecessarily Harsh|WP:NIHEITSIUHTPOWYHBUH]] please. [[Special:Contributions/79.66.56.21|79.66.56.21]] ([[User talk:79.66.56.21|talk]]) 16:54, 25 February 2009 (UTC)
== derivation of e = mc squared ==
== derivation of e = mc squared ==
Revision as of 16:54, 25 February 2009
Welcome to the science section of the Wikipedia reference desk.
The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
After reading 12-hour clock#Confusion at noon and midnight, I was quite surprised to find that the US Government Printing Office defines 12 a.m. as noon. (See this document and scroll down to section 12.9 or search for "noon".) I know that going back to the Latin, noon is neither ante- nor post- meridiem. But it seems when it is used, common modern interpretation is that 12 a.m. is midnight and 12 p.m. is noon. Is there any historic precedence for the GPO definition? Is there any other entity in this world that uses this convention? -- Tcncv (talk) 07:43, 16 February 2009 (UTC)[reply]
I'm more used to 24 hour time but the US GPO actually makes sense to me, since it goes 1am - 10am then 11am, it only follows that next is 12am followed by 1pm. Vespine (talk) 08:40, 16 February 2009 (UTC)[reply]
If you wish to communicate clearly and logically, say 12 noon and 12 midnight. Use of a.m. & p.m. after 12 is ambiguous and needs context to assist a correct interpretation. Even those who know the modern convention often get it wrong! Dbfirs09:11, 16 February 2009 (UTC)[reply]
The problem with your definition is 12:00:00.00000000000000000000000000000000000000000000000000000000000001 p.m. is clearly intended and logically can only be 0.00000000000000000000000000000000000000000000000000000000000001 seconds after noon. If you use 12 am to mean 12 noon then you have the oddity of suddenly changing to pm with the smallest measurable time interval afterwards which IMHO makes no sense. As I've remarked before when this came up, 12 pm as noon therefore makes a lot more sense and it seems to me outside of the US there is little ambiguity or confusion. Definitely when I searched, by and large the vast majority of sites used 12 pm to mean noon and 12 am to mean midnight. Google searches are of course hardly scientificly compelling but given the evidence, I see little reason to presume there is any real common misconception. Of course, I'm not denying that strictly speaking, the terms are ambigious or just plain wrong but then again, this is hardly uncommon with a lot of the English language. After all, most of us can survive when we say 'the weight is 80kg' even though they're really talking about mass. For that matter, as I've remarked before elsewhere on wikipedia, I personally don't care if people say their timezone is -5 GMT or -5 UTC. The fact that GMT is ambigious and they probably mean UTC but could mean UT1 is no concern of mine. I don't need that level of precision. I just don't want to have to work out or remember WTF EST is. This doesn't mean of course there aren't cases when you need to be completely unambigious or that even in general, it may not make more sense be accurate and avoid unambigious terms. Simply that it isn't really IMHO that big a deal. P.S. I originally had a lot more zeroes but for the sake of the reference desk, I reduced it Nil Einne (talk) 10:40, 16 February 2009 (UTC)[reply]
If it's 0.0 seconds after noon, it's equally 0.0 seconds before noon. I don't see any compelling reason that it's more reasonable for AM to be a half-open interval closed on the left, than a half-open interval closed on the right. The only correct (and only safe) approach is to say "12 noon" or "12 midnight", and we ought to insist on these terms.
Except of course that a general switch to 24-hour time would be even better. I made the switch long ago because I was irritated at having to get up at 7 AM (or whatever) and sleeping through it because I'd set my alarm for 7 PM. --Trovatore (talk) 10:48, 16 February 2009 (UTC)[reply]
I usually use 24 hour alarm clocks for that reason. However I have never really found the need to use 24 hours clocks in general usage. It's not that hard to use both, as it suits you. P.S. You haven't explained what happens at 12:00:00.00000000000000000000000000000000000000000000000000000000000001. Clearly 12:00:00.00000000000000000000000000000000000000000000000000000000000001 noon or midnight make little sense. P.P.S. Again I don't deny that a general switch to 24 hours may be better, simply that it doesn't really cause that many problems using both. Of all the confusing problems we have in the world, there are far bigger ones like the way some people insist on using customary units in everday life when most of the world has moved on Nil Einne (talk) 10:53, 16 February 2009 (UTC)[reply]
I missed this because of the anon intervention. Sure, epsilon after noon is PM. Just like epsilon before noon is AM. And noon itself is neither, just like 0 is neither negative nor positive. --Trovatore (talk) 11:56, 16 February 2009 (UTC)[reply]
Nil Enne has a point. It makes sense for pm to start 1 second after 11:59.59. Rather than 1 second+some arbitrary infintesimely small unit of time. The fact is the minute where the clock read 12:00.xx is in the pm, why not make the whole minute in the pm, rather than all of it except one infintesimal instant? —Preceding unsigned comment added by 129.67.37.225 (talk) 11:36, 16 February 2009 (UTC)[reply]
Assuming (and it's actually quite an assumption) that time is modeled by the real numbers, then the "1 second+infinitesimal" is not an option. The boundary point of AM, and the boundary point of PM, are both noon; the only question is which set noon actually belongs to, if either.
But there is no truly standard convention. The only safe course is not to depend on how the phrases "12 am" or "12 pm" will be understood (which means not using them at all). These locutions should simply not appear; they should be considered incorrect. --Trovatore (talk) 11:44, 16 February 2009 (UTC)[reply]
I think you're overcomplicating things. I'm personally not trying to argue from a strictly mathematical sense and as I've said before, I'm not denying at 12 noon and 12 midnight may be the only tecnically correct terms. My question is from a human POV, which one is more logical and simpler? Should 12pm be 12 noon or 12 midnight? Since most people other then SB accept that 12:00:00.0000000000000000000000000001 pm (or whatever) is 0.0000000000000000000000000001 seconds after noon it makes a lot more sense for 12pm to be 12 noon. Again let me repeat the fact this may not be entirely technically accurate or that you can make a legitimate argument that it should be midnight doesn't change the fact it's a lot simpler and more logical then suddenly changing at some underdefined interval which depends on what kind of mathematics we use and perhaps what kind of precision or accuracy we count time with. Let's not forget the whole idea from a scientific viewpoint of 12 noon actually being noon is bunkum anyway in basically every location of the world given the nicities of time zones, daylight saving time and astronomical realities particularly when we start to get to such a high level of accuracy. The whole thing is completely arbitary anyway that's why people prefer the simpler notion of 12:xx pm being 12 noon/afternoon then 12:xx pm being 12 midnight if it's precisely that and not even the tiniest measurable time interval after and if it is a measurable interval after then 12 it's 12 afternoon. If you still don't accept it then good luck I guess, meanwhile most of the world gets by fine accepting 12pm as 12 noon and 12am as midnight and trying to tell them they're wrong or it doesn't make sense isn't getting anywhere since for reasons I've tried to explain, it makes a lot of sense to most people who don't get into the overtly complicated mathematics and definition side of things which for reasons I've already explained seems a bit pointless. 14:18, 18 February 2009 (UTC)
Nobody can ever agree on what 12am means, so just use 12 noon or 12 midnight as appropriate. There is also confusion about when "midnight on Sunday" is. Is it the end of Sunday or the beginning? This confusion is so great that it's very common to see events advertised as being at either 11:59pm or 12:01am so there isn't any doubt. --Tango (talk) 11:51, 16 February 2009 (UTC)[reply]
Why doesn't the whole world go onto UTC and be done with it. That will not only eliminate the a.m./p.m. ambiguity, it will eliminate time zone confusion as well. After all, the US is moving to metric measurements. While we're at it, let's eliminate the 50 -States- State governments of the US, each with its own legislature and set of laws - it's clumsy, expensive, and confusing (though it's a lawyer's paradise in disentangling inter-State affairs. - GlowWorm. —Preceding unsigned comment added by 98.17.32.201 (talk) 14:53, 16 February 2009 (UTC)[reply]
I don't believe that 12:01am is confusing - you simply have to think for a moment. The number indicates the number of hours that have elapsed ante-meridiem. Hence 12:01am and 00:01pm are simply two different expressions of the same moment. The 24 hour clock is just a system where all hours are conventionally expressed ante-meridiem. Treating 12:01am as being shortly after midnight is silly. SteveBaker (talk) 15:10, 16 February 2009 (UTC)[reply]
What does "number of hours that have elapsed ante meridiem" mean? "Ante meridiem" means "before noon", "hours elapsed before noon" doesn't make sense. The only way I can see to interpret it is as "hours until noon", in which case 12:01am should mean one minute before midnight, which is certainly doesn't. --Tango (talk) 17:17, 16 February 2009 (UTC)[reply]
The way I see it is this: We divide the daylight hours into morning and afternoon, but we don't divide the night-time hours. There are no words for "before midnight" and "after midnight"; both before and after midnight are still parts of "night" - except that the date changes, but it's still "night" at 12:05 am. The morning ends and the afternoon begins at noon. The precise point of noon (if such a thing even exists; it's gone as soon as it arrives, not a second later, not a milli-micro second later, but instantenously) is probably in neither camp, but noon is when the afternoon begins. We start books on page 1; we start months on the 1st; so if noon is when the afternoon starts, then it makes sense to consider it part of the afternoon, rather than the very end of morning. It has intuitive sense, but may not appeal to scientists. -- JackofOz (talk) 23:12, 16 February 2009 (UTC)[reply]
But the start of a book isn't the end of something else. The hour from 12 noon to 1pm is certainly part of the afternoon, just as the 1st of March is part of March (the fact that we say 1st March, not 1 March is relevant here, and there's lots of interesting stuff about how time was measured and referred to in the past, but I won't get into it), but the instant of 12 noon and the instant at the beginning of 1st March are boundary points and it's completely arbitrary to assign them to either interval. It's far better just to leave them as separate points, hence "12 noon" rather than either "12 am" or "12 pm". --Tango (talk) 14:42, 17 February 2009 (UTC)[reply]
It seems to me that the 24 hour clock begins at 0.000000000000001 and continues to 24.000000000000000000000. By contrast the 12 x 2 hour clock talks of 12.02 am/pm instead of 00.02. I still think of noon as 12.00pm. Kittybrewster ☎14:56, 17 February 2009 (UTC)[reply]
The point is though that arbitary or not, it's a lot simpler for 12 pm to be 12 noon then for it to be 12 midnight particularly since the instant is basically just that, an instant which can be as small as we measure time. The problem with books is they are not a continuum since words or letters are discrete elements which is something that doesn't exist for time. Therefore you can easily say what the end of Harry Potter 1 is and what the beginning of Harry Potter 2. I've tried to avoid getting too complicated until now but if you get into the complicated side of things, but you have to really ask what do you mean by an instant when you are talking about a continuum anyway? It seems to me we're talking about something as meaningless as 'when does life start'. Since as I mentioned, even the 'instant' we would call noon isn't even noon nearly everywhere it becomes even more meaningless. This isn't uncommon in life. So if we are going to use something so meaningless, why not choose simplicity and not complicate things with 12:XX pm being the noon/afternoon period (i.e. during the daylight hours for most places) rather then the overtly complicated 12:xx pm being the afternoon period (during the daylight hours) unless it so happens it's the exact instant (00 precisely) we call 'noon' in which case 12:xx pm is 12 midnight. P.S. This will be my last posting on the subject in this thread and I'll probably just link here if it comes up again. P.P.S. Simplicity is the primary reason why I prefer metric over customary units, the complication of having two unit systems is bad enough but the overt complexity of a a system which doesn't fit in with our decimal numerical system or for that matter makes even less sense in other areas (seriously 0 degrees being a temperature with no meaning to anything we experience in real life nor any scientific meaning and where our universal solvent on earth boils at 212 degrees?). On the other hand, I do continue to use 1KB=1024 bytes so :-P Nil Einne (talk) 14:18, 18 February 2009 (UTC)[reply]
Academia at present
How could anyone be so complacently content with how the education system is today honestly? It's become more closed than actually being uneducated, as it seems. First of all, isn't there clearly a monopoly in nations? How could you monopolize knowledge? (That, of course, depends on whether 'education' still cares about knowledge nowadays.) How could you necessitate huge fines just for these bureaucratically-sanctioned 'educators' to 'teach' you? (Which mostly means shoving their own opinions on theories and whatnot down throats.) How could it be so tense? All of this wasn't founded like this though, was it? 94.196.67.254 (talk) 12:17, 16 February 2009 (UTC)[reply]
No... I'm talking about something deeper than that. A monopoly on knowledge itself that the education system as a whole creates that makes it seem like knowledge couldn't possibly exist outside it. —Preceding unsigned comment added by 94.196.67.254 (talk) 12:43, 16 February 2009 (UTC)[reply]
Perhaps you could be more specific in your question. What for instance would I be able to see that was different if things were the way you wish they were? Dmcq (talk) 13:36, 16 February 2009 (UTC)[reply]
It is possible that the OP refers to fringe areas of knowledge (spiritual, esoteric, psychoceramics, etc) which are excluded from mainstream education. There are, after all, folks who think that creationism should be part of the curriculum in physics and biology. If so, the question may be better placed at the humanities desk. --Cookatoo.ergo.ZooM (talk) 13:40, 16 February 2009 (UTC)[reply]
The education system certainly doesn't have a monopoly on knowledge - after all, there are public libraries, Wikipedia, the Internet - all of those are sources of knowledge that lie outside of the education system. If as Cookatoo suggests you are asking why the people in control of the education system act to limit what knowledge they teach - then that also is true, simply because there is more knowledge in the world than one person could possibly ever learn - and someone has to decide what subset of all knowledge is most important for people to know. Hence (for example) we teach basic algebra in schools - but we do not teach the proof of the three color map theorem. The reason for this should be self-evident - algebra is useful to everyone (eg I know my car just travelled 300 miles on 10 gallons of gasoline - how good is my mpg this week?) - but knowing WHY the three color map theorem is true is pretty much useless for every day life - and only a very few mathematicians really need to know it. So yeah - they limit what is taught to a reasonable set of things that the average person has time to learn and will find useful later in life. SteveBaker (talk) 15:03, 16 February 2009 (UTC)[reply]
Teaching the only known proof of the four-color theorem would be like teaching the phone book — it has a huge section of tedious, mechanical checking of an enormous number of cases; thus far, AFAIK, no human has ever gone through the whole thing — it's been verified only by computer. Of course arguably the "real" proof, from the perspective of a human mathematician, is the part that reduces the problem to those machine-checkable cases, and that could possibly be taught. I don't know whether it would be an undergrad or grad level course, as I don't know how difficult that part of it is. --Trovatore (talk) 21:56, 16 February 2009 (UTC)[reply]
I believe it's still way beyond the lecture-course level, in terms of size if nothing else. The five colour theorem, on the other hand, was on my undergrad course, and takes about half a lecture. Algebraist22:02, 16 February 2009 (UTC)[reply]
Academia as we know it in western culture arose from the Medieval university system of Europe. The OP's assertion that academia "wasn't founded like this..." is astonishing, considering that the medieval university was intended as the exclusive mechanism for passing literacy and historical knowledge to the next era of monks, selectively excluding the masses. As the system progressed, (a few revolutions later), academic institutions changed focus pretty significantly, and the philosophy of education changed dramatically. "The role of religion in research universities decreased in the 19th century, and by the end of the 19th century, the German university model had spread around the world." That is to say, students participated in four years of focused "undergraduate" curriculum with a major specialization, instead of five or seven years of religious, liturgical, and philosophy training in Greek and Latin, with the occasional mathematical theory course. Most prestigious American universities did not switch to the "German" model until around the first World War (Academic major attributes this to Harvard in 1910, but I have heard differently). In any case, it has been a fight uphill for centuries against the "establishment", with effort to liberalize the system. In my experience, the more rigorous scientific disciplines suffer less from the "shoving of theories and opinions", because most of science is pretty self-evident if you know where to look for evidence. Nimur (talk) 17:24, 16 February 2009 (UTC)[reply]
Just as an addendum, the first university in the US to really emulate a German model in terms of an undergraduate/graduate division was Johns Hopkins University. (There is more to the European model than just academic majors.) It's also of note that America was a considered largely a scientific backwater until the 1920s or so. --98.217.14.211 (talk) 01:54, 17 February 2009 (UTC)[reply]
Hmm, the US was a scientific backwater but at the forefront of technological (in things like engine design, flight, the work of Edison...). Sounds like the way we thought of Japan in until the 1990s. Seems like there is a story there.--OMCV (talk) 04:16, 18 February 2009 (UTC)[reply]
You say "either direction", does that mean you are talking about a 1D box? If the scenario is symmetric, then the solution will be. I don't know what you mean by "disscation", do you mean "dissertation"? If so, we're not going to write your dissertation for you. --Tango (talk) 14:07, 16 February 2009 (UTC)[reply]
Try google with your question title "quantum mechanics(a particle in box)" and and one of the first entries it comes up with is the wikipedia article Particle in a box. It is worthwhile learning how to use search engines like this. Dmcq (talk) 14:14, 16 February 2009 (UTC)[reply]
It is almost certain that your particle in a box is equally likely to be moving in both directions. If not then it will be drifting in one direction and ending up at one side of the box. Graeme Bartlett (talk) 20:25, 16 February 2009 (UTC)[reply]
It all depends on the Terpene you mean. Isoprene will neither be acidic or basic nor will it be solid at 25°C as the article states. Of course a long enough Polymer of Isoprene units will turn solid at room temperature, as will substituted Isoprenes. For all other Information see Terpenes or ask a more specific question. --91.6.7.232 (talk) 17:38, 16 February 2009 (UTC)[reply]
Vision, light pollution, and the Milky Way
Hi. Let's say someone had 20/1 vision. Now let's say that another person with 20/40 vision, after dark-adapting their eyes away from as many streetlights as possible, at a given location, at night, can see objects up to a limiting magnitude of +4.5, without wearing glasses. Now let's say that the subject with 20/1 vision looks at the sky under the same conditions, would the subject be able to see the Milky Way (the subject with 20/40 vision cannot see the Milky Way under these conditions, but is able to from a location with less glare and light pollution)? Thanks. ~AH1(TCU)16:50, 16 February 2009 (UTC)[reply]
I don't visual acuity is the right measure of quality of eyesight for this. Visual acuity is about how well you can resolve small things, you're talking about how well you can see dim things, they are completely different abilities. Also, does anyone actually have 20/1 vision? That would be extremely impressive. --Tango (talk) 17:07, 16 February 2009 (UTC)[reply]
On second thought, probably not. The size parameter is dictated by the angular area of a single pixel; the dimness is more of a signal-noise question or quantization size per-pixel. Nimur (talk) 17:33, 16 February 2009 (UTC)[reply]
Sensitivity comes from the number of rods & cones, resolution from that too, but mostly from lens shape (i. e. I have 20/30 vision because my lenses are a little deformed). It is possible that the pixelation from a finite number of rods/cones could start to blur images at 20/1 vision (certainly it would before you got to 20/0.00001, for instance). As above, I don't think there are likely to be many people with 20/1 vision (although it may be possible - one must remember that people exist who are nine standard deviations from the mean). WilyD18:03, 16 February 2009 (UTC)[reply]
According to our article on visual acuity, 20/10 or possibly 20/8 is about the limit for humans. I'm not sure visual acuity follows a bell curve (I believe there are more people with worse than 20/20 vision than there are with better - 20/400 (uncorrected, which is what we're talking about) isn't very uncommon, the equivalent in the other direction would be 20/1, which is unheard of), so the 9SD thing doesn't necessarily apply. --Tango (talk) 18:09, 16 February 2009 (UTC)[reply]
It should be noted that the Earth is part of the Milky Way Galaxy. Just about everywhere you look, you're looking at the Milky Way. Now if you want to look at the rest of the Milky Way Galaxy, that's a different question. Sorry to be anal, but it always bugs me when I hear people say things such as "I can't see the Milky Way Galaxy". I always want to say back, "You're looking at it right now.". Whew! That felt good to get off my chest. :) A Quest For Knowledge (talk) 18:17, 16 February 2009 (UTC)[reply]
"Milky Way" in this context (which is the original context) refers to the disk of the galaxy, which appears from our perspective to be a band of densely packed stars going all the way around the sky. --Tango (talk) 18:38, 16 February 2009 (UTC)[reply]
Well, the thing is, I have relatively poor vision, and wearing glasses allows me to see more stars in the night sky. For example, just today, I was able to see Venus in glasses 1 minute before sunset, but not without glasses until about 2 mintues after sunset. Maybe visual acuity is a measure of myopia or non-myopia-ness? Or, would someone with 20/1 vision see objects 20 times "closer" than people with 20/20 vision, meaning that astronomical objects seem "closer", and thus brighter as well? I came up with this (hypopthetical) question after a friend claimed he had 20/1 vision (being able to see the entire eye testing chart as well as all the copyrights), and he also claimed that he has never looked up at the night sky (I don't know if either one is true or not). I find that a limiting magnitude of about +5.5 is sufficient to glimpse the Milky Way. Would people with a higher-than-average visual acuity be able to see down to a better limiting magnitude under identical conditions? Thanks. ~AH1(TCU)23:30, 16 February 2009 (UTC)[reply]
First, visual acuity is how small of an object, in terms of angular size, that you can see. So yes, myopia directly decreases visual acuity by preventing the lens from focusing correctly. People with better vision certainly don't see objects as if they were closer; all objects appear to be of the same size to you and your friend. If he has 20/1 vision (I doubt it; why not test him?), he can see something of a certain size, say 1 mm, from roughly 20 times the distance somebody with 20/20 vision can. But that's just because his eyes can focus more accurately, not because of anything mysterious.
Second, it makes sense that you can see more stars with your glasses than without. Stars are point sources, and the better the eye focuses, the smaller the area it takes up on retina. A small circle of confusion is good because more light is being focused on fewer rod cells, so the star needs not be as bright to be detected. A large circle of confusion has the opposite effect. For an extreme case, imagine finding a star using a telescope and throwing the instrument way out of focus. You won't see a thing.
The Milky Way, however, is anything but a point source. Blurred vision should not be much of an impediment to seeing it because it's always "blurred" in the sense that it has no sharp edges. Smoothening out the transition from the Milky Way to the rest of the sky by a tiny bit can't have much of an effect. --Bowlhover (talk) 02:27, 17 February 2009 (UTC)[reply]
i noticed that some times that while opening abottle of water (in liquid state) after take it out from afreezer it suddenly start to freez , do this have some thing to do with pressure ,,, ? —Preceding unsigned comment added by 86.108.53.185 (talk) 18:32, 16 February 2009 (UTC)[reply]
Supercooling is a possibility, but the more likely explanation is the one you came up with, that the water is pressurized and that it is therefore able to stay liquid at a colder temp. Releasing the pressure allows it to freeze quickly. StuRat (talk) 19:03, 16 February 2009 (UTC)[reply]
(edit conflict)Well, I guess supercooling can be a factor as well, but if it's a pressurized container -- say, a can of soda -- that's not the reason. Rather, that'd be the CO2 in carbonated drinks. You don't mention if the water is carbonated, 86.108.53.185, but you do mention pressure, so I'm going to assume that that it is -- and you're correct, it does have something to do with the pressure. When you open the bottle, the CO2 gas suspended in the liquid expands and the pressure between the contents of the bottle and the atmosphere outside is equalized... and when gases expand, their temperature drops. Since you've kept the bottle in the freezer, the temperature of the water is already very close to its freezing point; when you open it and release the pressure, it cools down a little bit more, and that's enough to make a difference: it freezes. You don't get a solid block of ice, of course; it's more like a bottle filled with slush, because the temperature drop isn't that dramatic... but ice is ice. -- Captain Disdain (talk) 19:15, 16 February 2009 (UTC)[reply]
Water freezing up in an ice cube tray
I've noticed something strange a couple times when I made ice cubes. Normally, when you freeze water in an ice cube tray, I would expect that the surface of the ice cubes to be (more or less) flat. However, a couple of times, towards the centers of the several of each ice cubes' surfaces, water had apparently frozen up. They sort of looked like inverted icicles. I'm using a standard ice cube tray and a plain old refrigerator. How is this possible? A Quest For Knowledge (talk) 19:00, 16 February 2009 (UTC)[reply]
Water has many unusual and mysterious properties, some mysterious even to science. I've read that one experiment suggested water to be H1.5O! ~AH1(TCU)23:21, 16 February 2009 (UTC)[reply]
Percent of people infected by the "common cold" each year in US
About what percentage of people are infected with the common cold each year in the US? I'm looking for an authoritative source -- a peer-reviewed journal or NIH website, for instance, would be great. I was able to find one here that said 90%, but I also found another (can't locate it at the moment) that said 35%.
The CDC page links to a huge number of academic and medical sources. "HPIVs are ubiquitous and infect most people during childhood. The highest rates of serious HPIV illnesses occur among young children. Serologic surveys have shown that 90% to 100% of children aged 5 years and older have antibodies to HPIV- 3, and about 75% have antibodies to HPIV-1 and -2." The difficulty is in defining the "common cold" - depending on how widely you categorize ailments as "common cold", you will get incidence estimates that vary by orders of magnitude. Nimur (talk) 21:12, 16 February 2009 (UTC)[reply]
Hmmm... the 90-100% figure would appear to be the total number of children exposed to the viruses at some point in their lives, not the total number of infections per year. But thanks for the sources. If anyone sees anything else, it would also be helpful. Thanks, Sam 146.115.120.108 (talk) 23:51, 16 February 2009 (UTC)[reply]
As soon as I read this question, I wonder what do you mean by 'infected'? Does the person have to show symptoms, or just come in contact with the virus? I don't know if refining the question like this will get you a better answer (maybe scientific journals all define infected the same way), but it might help (and I'm curious). -Pete5x5 (talk) 05:59, 17 February 2009 (UTC)[reply]
Sex hormones in ham?
Does ham sold in Canadian markets naturally or artificially contain human sex hormones or any substances with similar effects on humans? NeonMerlin21:27, 16 February 2009 (UTC)[reply]
I would seriously doubt it. This sounds to me like an urban myth. That said, I believe that some plastics can degrade into chemicals similar to oestrogen. That may not be true, however -It's only half-remembered.--NeoNerd21:36, 16 February 2009 (UTC)[reply]
NeoNerdi you're probably thinking of Bisphenol A We haven't had a question mentioning that for a while. Waiting for Benzyl butyl phthalate to take off. Use of growth hormones in pork production is prohibited in the US and Europe AFAIK. I found this study which you might find helpful [1]. You might also have found [2] or [3]. Estrogens naturally occur in pigs. We need industrialized agriculture to feed our masses. Unfortunately that comes at the price of sometimes having undetermined health effects. I's good to be vigilant, but the media scare waves based on some poorly represented study are rarely helping. 76.97.245.5 (talk) 23:41, 16 February 2009 (UTC)[reply]
Tangential to the urban myth: If male pigs are not castrated, the meat may take on a on an unpleasant odour that 40% of the human population is able to detect. This is due to skatol and androstenon, especially the latter which is a pheromone. EverGreg (talk) 19:16, 18 February 2009 (UTC)[reply]
Just a guess, but I'm going to have to say no. Every 'colour' in the sense we think of (the visible spectrum) is dependent upon wavelength, and I'm guessing we know all the individual wavelengths which produce different shades of different colours. The only way you could alter this is by going outside the visible spectrum, and then the product wouldn't be defined as a colour, per se. —Cyclonenim (talk · contribs · email) 22:29, 16 February 2009 (UTC)[reply]
Any combination of waves from the set of possible wavelenghts superpose to make another wave which is already in the set of possible wavelengths, so by considering all possible wavelengths all possible combinations are already considered.
You could make new colours be fiddling with how the human eye works, but I think that's it. Pretty much all the colours possible are shown in the CIE 1931 color space chromaticity diagram (pictured here, but it won't be displayed correctly by your monitor). It doesn't correspond to precisely how the human eye sees colours, but it's designed to be pretty close (it's meant to be the "chromatic response of the average human viewing through a 2° angle" - what "average" means in that context, I don't know). --Tango (talk) 22:38, 16 February 2009 (UTC)[reply]
(ec) Human perception of colors correspond with how our visual and neural hardware perceive wavelengths of light. It's a finite range of possible perceptions—with the "standard hardware". There are some people who apparently have non-standard visual hardware who can see more colors than the majority of us can (see tetrachromacy), and of course there are those with non-standard visual hardware who perceive less colors than the majority of us (see color blindness). Other than those possibilities, there's no way for humans to experience more colors than the standard "visual spectrum". --98.217.14.211 (talk) 22:40, 16 February 2009 (UTC)[reply]
On the other hand, not all colours appear in the spectrum. Brown, for example. We perceive this as a colour separate to anything else, even though we know it's some combination of spectral colours. The spectrum would have infinite gradations (not all discernible to the human eye, admittedly), so theoretically there's an infinite number of ways of combining two or more spectral colours to come up with a complex colour (again, not all separately discernible to the human eye). Have all of these possible combinations been recorded and named? I very much doubt it. -- JackofOz (talk) 22:54, 16 February 2009 (UTC)[reply]
Not named, but we do know all the colors people are capable of seeing; they're all on that diagram, except that it doesn't show different brightnesses (and ordinary display screens are incapable of showing it correctly). -- BenRG (talk) 01:56, 19 February 2009 (UTC)[reply]
I could imagine that evolution or genetic engineering may expand the sensitivity of human eyes, say, into the infrared spectrum. There may be significant benefits if folks could see a warm (edible) rat in some post-acocalyptic scenario in the middle of the night.
There may also be significant advantages if humans could "see" ultrasound or gravity waves or whatever. It would make sense to invent terms of pseudo colours for these new sensations. If you can visually interprete the bits and bytes generated by the graphic card of your PC you have already saved €250 for a useless monitor. --Cookatoo.ergo.ZooM (talk) 22:57, 16 February 2009 (UTC)[reply]
Also, as Steve alluded to recently (though I don't recall that he brought up this specific aspect), certain wavelengths in the near UV are invisible not because the retina doesn't respond to them, but because the lens filters them out. If your natural lens is removed (e.g. for cataracts) you will be able to see this light, and as it has a different mix of responses from the three sorts of cones than any other wavelength, you may perceive a color that no one with normal eyes can see.
The IR emitted by a rat is very distant IR. About 10µm, I think, compared to the limit of human vision of about 700nm, so that's more than a ten-fold increase, whereas the current range of human vision is less than a factor of two from one end to the other. So engineering human eyes to see those wavelengths would be very difficult. Other animals can do it, though, see Infrared sensing in snakes. I guess we could try and add some snake DNA to our genome... --Tango (talk) 23:08, 16 February 2009 (UTC)[reply]
It's quite complicated - there are at least four ways to answer this question:
There are colors we can't perceive because our retina is not sensitive to them (eg InfraRed). You can see infrared using night-vision equipment - but that works by turning the IR into shades of green. You aren't 'seeing' the colors as different (it's just plain old green) - but you can see things that you wouldn't ordinarily be able to see like that a car has recently been driven because the engine bay is hot and therefore emitting IR "light". Without this extra 'sense' we can't tell the difference between a car with a hot engine and a car with a cold engine - they look EXACTLY the same.
There are colors in the near UltraViolet that we can't perceive with normal eyesight because there is a protective sun-screen over our eyes that protects the retina from sunburn. However, some people have that protective layer removed as a result of cateract surgery. After surgery they can see light in the near ultra-violet - but it just looks blue. However, you can see blue-ish spots and stripes on flowers - which are really ultraviolet spots and stripes that the flower has evolved to attract bees (which can see into the UV). But just as with night-vision - it doesn't seem to be anything amazing - just shades of blue.
We only have three kinds of 'cone' sensors in our eyes - so we see all colors as if they were mixtures of red, green and blue. But in the real world, there are (for example) 'kinds' of yellow that are mixtures of red and green and 'kinds' of yellow that look absolutely identical to us - but which are really pure frequencies of yellow light with no trace of red or green. If we had the eyes of certain species of freshwater shrimp - we'd have as many as twelve different cone types and the world of color would be VASTLY richer and different than we can actually see. In that sense, there are vast ranges of color that exist physically - but we just can't tell the difference. It's like we're all somewhat colorblind. So there are "more" colors out there - but to see them, you've somehow got to become a shrimp...unless...
There are very, very few women who are 'tetrochromats' who have a fourth kind of green sensor - they see colors in a richer way than we do - and they could distinguish colors that we consider to be identical as if they were very different indeed. Just two such people have been identified as a result of genetic studies. They have to have both parents who are colorblind in very specific ways. But they TRULY see colors that we can't even imagine.
It's not at all true that "we see all colors as if they were mixtures of red, green and blue"—see my response below the divider. -- BenRG (talk) 01:56, 19 February 2009 (UTC)[reply]
When you say you see more brown, what that means is you can't distinguish between brown and certain other colours (red and green?). That doesn't mean brown is any different to any other colour, it just happens to be the one you have difficulty with. Basically, you see all combinations of red and green as the same thing, brown is one of those combinations. Why you describe it as seeing lots of things as brown, rather than lots of things as red, or lots of things as green, I don't know... convention, maybe? Or is there some underlying reason? Anyone? --Tango (talk) 14:12, 17 February 2009 (UTC)[reply]
Not exactly, I have problems generally with any mixed colours that involve red or green, e.g. mauve looks blue to me, but all 'muddy' reds and greens look brown to me, if I can't see a distinct colour, I call it brown. Mikenorton (talk) 16:43, 17 February 2009 (UTC)[reply]
It sounds like your response to red and green are the same as each other and significantly reduced from normal (you can't distinguish brightness of the colours you see as the same colour). The fact that they're the same is why anything that's just made up of red and green looks the same, and the reduction from normal levels is why it looks brown (rather than yellow, say - I'm assuming you see yellow as brown, yes? Whereas someone with normal colour vision sees bright yellow and yellow and dark yellow as brown (ish)). --Tango (talk) 18:01, 17 February 2009 (UTC)[reply]
Just to clarify, I see pure red as red, pure green as green and indeed bright yellow as yellow. I have the most common red-green colour blindness with a reduced sensitivity to red and green. It's worth remembering that, just like everyone else, I learned to call colours by particular names, whether I actually 'see' red as other people see red is impossible to tell. Mikenorton (talk) 18:11, 17 February 2009 (UTC)[reply]
So it's when red and green are mixed that you can't tell how much of each there is? So essentially you can't distinguish different shades of brown - reddish-brown, greenish-brown, yellowish-brown and anything inbetween all looks the same? And you call them all brown because that's what the rest of us call them - we just use the word to describe lots of colours which to you are just one colour. If my understanding is right (scientific method: Make observations, form theory, make prediction, test prediction!) you should have difficulty distinguishing bright orange and bright yellow, is that correct? --Tango (talk) 18:20, 17 February 2009 (UTC)[reply]
Better finish this off now, I'm having trouble counting the colons. Yes I have problems with that pair (more with yellowish orange and yellow) and similarly yellow and yellowish green. Otherwise your description seems about right. Mikenorton (talk) 18:35, 17 February 2009 (UTC)[reply]
My theory stands up to empirical testing (to an acceptable margin of error), fantastic! Thanks for helping me get my head round this. --Tango (talk) 19:07, 17 February 2009 (UTC)[reply]
@Mikenorton: It's quite rare to have both 'weak red' and 'weak green' colorblindness - much more common is 'weak red' on it's own or 'weak green' on it's own (which is what my son has). It's overwhelmingly likely that you have either one or the other but not both...and it would be valuable for you to find out which. What this does is to tend to make shades of orange, yellow and 'lime green' (yellowish-green) harder to distinguish - but it doesn't make it impossible. We discovered that my son is colorblind at age 16 when he got told off for not turning off his Wii videogame console. It has a tri-color LED that shows red, orange or green. Orange is 'standby' and Red is 'off' - and it rapidly became obvious that he couldn't distinguish the orange from the red because they differ only by a small amount of green - and with less sensitive green receptors, he can't tell the difference. But his handicap is very minor. In fact, the ONLY time it shows up seems to be with tricolor LED's and the fact that he fails the standard colorblindness test. The rest of the time, his color perception seems OK. FWIW, we were able to help him with the Wii problem by taping a piece of green-tinted candy-wrapper over the Wii's LED. This shut out most of the red light so that he's now able to see whether the LED is very dimly green or off altogether. Experimenting with colored filters may well help you in similar situations. SteveBaker (talk) 14:26, 18 February 2009 (UTC)[reply]
Steve: I thought I had read somewhere that the UV color was at least a little outside of normal experience. It certainly seems possible a priori — say, if a certain near-UV wavelength produced a larger ratio between the blue-cone response and the green-cone response than any normally visible wavelength, then you wouldn't be able to reproduce that signal by any combination of normally visible light. (I suppose people could see it if you shined that wavelength at them at such high intensity that enough of it came through the protective layer — good luck getting that past the ethics committee!) --Trovatore (talk) 02:02, 17 February 2009 (UTC)[reply]
The problem is that you only have three color sensations (Red,Green,Blue) - and all color perception is mixtures of those sensations. Ultraviolet light (for people who have had cataract surgery) stimulates the blue sensor and does not stimulate either of the other two - so the sensation is no different from a rather pure blue. My mother had cataract surgery and she wasn't aware of having seen amazing "new" colors - but rather she sees blue in places where she didn't before. She's an avid gardener and was somewhat surprised at how formerly uniformly colored blooms now had spots or stripes or other markings. But sadly (and predictably) no 'new' colors. Presumably objects with large amounts of UV reflectivity would also change hue slightly - but still, she's unable to perceive 'new' colors. That's not possible without having more color sensors - and for that to happen, you'd have to be born as a tetrachromat or a freshwater shrimp. SteveBaker (talk) 03:18, 17 February 2009 (UTC)[reply]
Well, you seem to have skipped over my point, though. It may be true that your mother doesn't see any new colors; I don't know. But if it were the case that one of these wavelengths she now perceives could get a higher ratio of blue-to-green, or blue-to-red, or blue-to-(0.3*green+0.7*red), or something like that, than any normally-visible light — then she theoretically could, because no linear combination with positive coefficents of normally-visible light could get you that ratio.
Note that just because she hasn't seen any such colors doesn't refute the idea, because she presumably has not been exposed to pure light of such a wavelength.
Indeed - she should be able to distinguish things as being different colours when we see them as the same colour, that's seeing new colours. The new colours will just be new shades of blue/violet, since it's only pretty near UV so isn't that different from blue, but it's still new colours. It will be rather difficult to distinguish them, since the human eye isn't very sensitive to differences in wavelength towards the ends of our usual range, but it will distinguish them a little. --Tango (talk) 13:34, 17 February 2009 (UTC)[reply]
That isn't the point. Being able to distinguish things that we see as the same color is not perceiving new colors — you might be able to distinguish A and B even though a person with normal lenses couldn't, but you'd maybe see A the way you used to see C and B the way you used to see D, so there's no new color being perceived.
The point is that maybe, for every wavelength that you and I can see, whenever the blue cones are firing at 100%, the green cones or the red cones are also firing, say at at least 5% and least 7% (these are just made up numbers).
Whereas maybe when Steve's mom looks at this new light, when it fires her blue cones at 100%, it's only firing her green cones at 2% and her red ones at 8% (again, made up).
In that case she would have a mixture of signals from the cones that is not possible, with any light, for a person with natural lenses. --Trovatore (talk) 19:25, 17 February 2009 (UTC)[reply]
But if you distinguish colours by seeing them as other colours then you lose the ability to distinguish those colours, so that doesn't help - that's just seeing different colours, not new colours. Someone without the filtering lens can distinguish between, say, "blue+UV" and "blue", two colours which the typical human can't distinguish between. (Perhaps I'm using the word "colour" slightly differently to its standard definition.) --Tango (talk) 19:45, 17 February 2009 (UTC)[reply]
I read it. That's distinguishing new colours. If it was monochromatic UV, then it would be distinguishing UV from black, if it's UV+something visible then it would be distinguishing that from just the visible part. When you see extra strips on petals, that's distinguishing the colour of the strip from the colour of the rest of the petal, which the human eye can't usually do. --Tango (talk) 21:43, 17 February 2009 (UTC)[reply]
I read it too - and I didn't reply immediately because I wanted to check my sources to be absolutely sure. I don't think there is a 'new' color there. UV light starts at 400nm. When I look at higher resolution plots similar to the diagram above I find that the red receptor doesn't function to any measureable degree at 400nm. Green and blue are both tailing off - but green hasn't completely gone away the ratio of green and blue at 400nm is not a whole lot different than in the "indigo" blue region right next to the 400nm cutoff. It's possible that the precise shade of blue you'd see wouldn't be identical to any 'normal' shade of blue - but the difference is right down in the noise. I don't think there is a noticably new color there - although I'll admit that it's mathematically possible. Most important of all - LOTS of people have had this surgery and I can find no references to anyone seeing anything stunningly novel - they mostly report seeing new patterns and that some 'normal' objects seem to have shifted color - but not one (that I could find) report anything "new". SteveBaker (talk) 22:50, 17 February 2009 (UTC)[reply]
No, what I'm talking about is actually seeing new colors (or at least, new ratios of signals from the cones, that are not possible for a person with natuarl lenses). What you were talking about, in the 13:34 17 Feb post, was only making different color distinctions, which is not the same thing. --Trovatore (talk) 21:49, 17 February 2009 (UTC)[reply]
Well, it's just going to look like a slightly different shade of violet (as Steve says), you're not going to notice it as being new if you're just looking at it in isolation. You'll only realise it's new when you compare it to existing shades of violet. --Tango (talk) 22:54, 17 February 2009 (UTC)[reply]
Well, those graphs are obviously wrong (or, let's say, "incomplete") because they don't show the response of the red cones to violet light. The red line should start turning upwards again towards the left edge — that's why you see violet light as "purple". --Trovatore (talk) 23:05, 17 February 2009 (UTC)[reply]
Yes - the graph that's attached to this thread is wrong on several levels - it does miss out the little 'bump' at the end of the red curve - but worse still, someone has 'normalised' the responses to some arbitary 0..1 scale - when in reality, our eyes are rather insensitive to blue compared to red and especially green. I have a much more accurate plot which makes this rather clearer. The red 'bump' actually confuses matters still further because there are places where a mixture of red and blue light can produce a 'magenta' shade that produces the exact same response as true 'violet' light on the visible side of the 400nm cutoff. There is pretty much guaranteed to be some mixture of plain old red and blue light that produces the exact same response as near-UV light does in these post-cataract-surgery people. And as I said before - if people started to see "new" colors after surgery - surely at least a few of them would have written about it - or it would be mentioned in the literature...and it isn't - so that is really the bottom-line proof we need. All that is ever reported is seeing 'old' colors in 'new' places. SteveBaker (talk) 14:11, 18 February 2009 (UTC)[reply]
(outdent) Ah, thanks, Steve — I was getting concerned that I might have misheard the thing about the red response at the violet end. Actually I'm a little disappointed I didn't, as that would have meant there were something interestingly complicated going on.
Anyway, I'd be interested in seeing this more accurate plot, if you have sufficient rights to upload it, or if you can supply an external link. --Trovatore (talk) 20:52, 18 February 2009 (UTC)[reply]
If people are interested, after a little Google Scholaring I found this paper about an experiment from 1980 finding the response curves. Page 5 shows the (normalised) curves they found, however for some reason that doesn't seem to be explained the curves for all except the "blue" cones are truncated at 400nm, and just the blue line continues to 350nm (which the description of the methodology suggests they were all tested to). You can clearly see that the green and red lines are both increasing again towards shorter wavelengths, and that the red curve has climbed back above the green one by 400nm and will presumably continue to climb above it (I can only guess). The graph shows that the response of the red and green cones to violet light (at about 400nm) is approximately the same as that to a combination of equal parts (assuming everything works linearly, which I think it does, at least approximately) blue light (at about 470nm) and red light (at about 650nm). The blue cone's response to violet light is significantly greater than its response to blue light, however - that may be less relevant due to the greater overall sensitivity of the red and green cones (according to Steve - this paper doesn't discuss that, at least not simply). This all seems to be consistent with the idea that violet looks like a mixture of red and blue due to the "bump" (the graph only shows an increase, but there is almost surely a decrease again at some point) in the red cone's response curve (or, more accurately, due to a greater bump in the red curve than the green). --Tango (talk) 17:00, 18 February 2009 (UTC)[reply]
See "List_of_colors#Fictional_colors". The article describes ulfire and jale as shades of ultraviolet, but in reality (in fiction, actually) they are two more primary colors that can be seen by a race whose eyes can see well into infrared and ultraviolet (a very good sci-fi book, by the way, that). Carlos Castaneda reports an indefinable color in one, I forget which, of his hallucinatory tours-de-force; a monster guarding a path shows him its colored back. --Milkbreath (talk) 02:25, 17 February 2009 (UTC)[reply]
It may be possible to stimulate the cones in different ways, for example the green cone absorption spectrum overlaps the red substantially and the blue somewhat, so there is not normally a pure green cone stimulation. If a pattern of light could illuminate the retina so that only green cones were stimulated you would get some form of ultra green colour sensation. Graeme Bartlett (talk) 03:23, 17 February 2009 (UTC)[reply]
Yes, you could (theoretically) connect electrodes to the retina/optic nerve and make all kinds of weird things happen, but you couldn't do it by shining light into the eye (which is what we usually mean by "seeing"). --Tango (talk) 13:34, 17 February 2009 (UTC)[reply]
Another idea for ultragreen is to bleach the red and blue cones with bright deep red and violet light, and then look at green spectral colour and see what it appears like. Graeme Bartlett (talk) 20:42, 17 February 2009 (UTC)[reply]
Argh. I wish I'd noticed this thread sooner. Listen up, folks:
We do not see the world in red, green, and blue.
Our three cone types are not red, green, and blue, despite the misleading coloring on that diagram above, which I changed a few months ago for this very reason but it got reverted. Here's my version; the colors aren't any more sensible but at least they aren't the exact three colors that are most likely to mislead people.
To the best of my knowledge the L (long-wavelength) cone does not have a secondary peak in the violet. The diagram I just linked, which shows no such peak, is correct as far as I know. More importantly, though, there's no reason to expect any such peak, once you understand how color vision actually works. If you think that the three cones are red, green, and blue then you might expect such a peak, but they aren't, not in any way, shape, or form, so that whole line of reasoning is irrelevant.
It's easy to understand how color vision actually works, you just have to wipe your mind of this nonsense about red, green, and blue. Ready? Okay. There are three cone types in the eye, each with a different response curve. This means that the infinitely many different wavelengths that make up a physical color spectrum are projected down to just three nonnegative numbers by the cones. What wavelengths is each cone sensitive to? It hardly matters at all, for reasons that I hope will be clear in a minute (though I'd like to again emphasize that the answer is not red, green, and blue). The important thing is that there are three dimensions. One of those three dimensions is just overall brightness. If you divide out by that you're left with two dimensions. One popular coordinate system for that two-dimensional space was standardized by CIE and is imaginatively called the "xy" coordinate system. The diagram at the start of this thread is plotted in xy coordinates.
The following is not understood by the brain's visual system—it is a modern scientific discovery: If you plot the responses of the cones to monochromatic light in xy coordinates, you get the Λ-shaped curve that forms most of the boundary of that diagram. The cone responses are linear (twice the incoming energy with the same frequency distribution → twice the response from each cone type). The xy coordinates are a perspective projection of the linear cone-response space (just like in 3D graphics, with the "eye" at (0,0,0), i.e. perfect blackness). Therefore, given two physical colors (that is, spectra) which map to (x1,y1) and (x2,y2), any linear combination of the two colors will map to a point on the line joining (x1,y1) and (x2,y2). Any linear combination with nonnegative coefficients will map to a point on the line segment with (x1,y1) and (x2,y2) as endpoints. This means that the only (x,y) coordinates you can reach with physical spectra are those in the convex closure of the Λ-shaped curve, which is why that part is colored.
Here's what the brain understands: There's a two-dimensional space of colors with a distinguished white point in the middle. Different directions from the white point are interpreted as different hues, and different distances from the white point are interpreted as different saturations. The brain doesn't know anything about monochromatic light, and it has no reason to care: it can't see the physical spectrum, all it gets is these two coordinates (plus brightness).
So why does violet look like a combination of red and blue? Because it's between red and blue in the only color space the brain knows about. Frequency has nothing to do with it. There's no highest or lowest in the brain's notion of hue—it's a circle.
Getting back to the original question, if you stimulated the cones in a way that's impossible with physical light, what would you see? I can only guess, but presumably you would see supersaturated versions of the same old hues. It would be a new visual experience, but not a new hue, which is what people probably mean by "color" in this context.
Red, green, and blue are used for color reproduction. With three colored phosphors on a display monitor you can reproduce any color in the triangle with the (x,y) coordinates of those phosphors as its vertices. If you look back at the CIE diagram it's pretty clear that the largest triangle you can fit in there will have vertices at red, green, and blue/violet. So those are the phosphors used on real displays—except that they aren't because nothing ever makes sense. For practical reasons real displays use phosphors that cover a rather small triangle on the diagram, but they're still red, green, and blue and they still cover the whole circle of hues, just not the whole range of saturations. These days the primaries are usually sRGB, shown here. That image itself uses sRGB (as does the one at the top of this thread) and your monitor is probably calibrated in sRGB, which means only the colors inside that triangle are correct; the others are not saturated enough. (They're also the wrong hue because whoever made these diagrams clamped the RGB channels individually to [0,1] instead of clamping in the direction of the white point, which makes the green portion look a fair bit larger than it should.) -- BenRG (talk) 01:27, 19 February 2009 (UTC)[reply]
BenRG loves to cut in at the end of a long (and largely correct) explanation and claim that everything that's preceeds his remark is stupidly wrong...however, more than 50% of the time that's not true. This time doubly so. OK - so let's take his points individually:
There is no green sensor. Well - kinda. The actual center frequency of the 'mid-range' sensor is more towards yellow - and the PERCEPTION of green and yellow is much confused by the large amount of overlap with the red sensor. But we CALL it the green sensor...and you aren't going to change that. Green is the color seen by the green sensor...by definition.
Hence we do see the world in Red, "Green" and Blue...by definition.
You aren't aware of the 'red bump' up in the middle of blue. Well, yes, it's a relatively new finding (compared to the ancient nature of the original set of curves). However it's the thing that explains the human tendancy to position a color called 'violet' or 'purple' or even 'magenta' between blue and red on a "color wheel" - even though physics tells us that red and blue are the ends of the spectrum. Weird - but true.
One of the three color 'axes' is intensity - well, we're talking about a 3D 'color' space - and elementary math says that you can represent any point in a 3D volume by three numbers - and you can map the space with spherical polar coordinates, cylindrical polar coordinates, axes at right angles, axes that aren't at right angles...lots of possibilities. Hence, yes, you could (say) divide red and green by blue and come up with some other set of axes - which is close to what the standard chromaticity diagram does - but there is no "correct" choice - there is merely "convenient" choices. So you come swooping in and implying to our poor OP that everything he's already been told is wrong - for what reason? To make you seem 'smart'? Well, trust me - it doesn't. We commonly use RGB axes because that's closest to the biological truth (for daylight viewing conditions in the center of your field of view). We could get into MUCH more complexity by talking about vision at the periphery of your visual field - and in near-darkness and so forth - but we're trying to keep it simple and answer the question. So we're all answering the question using three perpendicular axes labelled "red", "green" and "blue" - and that's convenient and comprehensible. You are not making yourself sound at all "clever" by picking some wierd-assed coordinate system and then loudly proclaiming that everyone else is wrong. That doesn't fly - OK?
Your explanation for the perception of violet is wrong. The high frequency 'bump' in the red curve is the reason.
"Red green and blue are used for color reproduction" - not always. A color inkjet printer (for example) uses cyan, magenta, yellow and black for example. The color gamut of ink, CRT's, LED's, DLP's, color photographic emulsions, fabric dyes, etc are all different - but that's irrelevent because we're asking what humans can see - not what we're able to display in various media.
So: Your post doesn't advance answering the question in any meaningful way - it simply introduces confusion just for the sake of it...which I find annoyingly typical of several of your recent posts. SteveBaker (talk) 03:15, 19 February 2009 (UTC)[reply]
I think everyone involved in this discussion understands all of that. Whether you like it or not, the three cones are frequently referred to as "red", "green" and "blue". Even the paper I linked to above uses those names. It makes sense, too - red light stimulates primarily the red cones, blue light stimulates primarily the blue cones and green light is, well, somewhere inbetween. Those colours don't correspond to the peaks in the response curves, but that doesn't means they aren't useful names. Violet is between red and blue when viewed in terms of polar coordinates centred at the white point in xy-space because of the response curves. It's those response curves which determine the xy-space (as I explained above, the xy-space is defined in terms of colour matching functions that were determined using human response curves - those functions are the ones shown in this plot and you can clearly see a bump in the red curve). If you had different response curves, the curve corresponding to monochromatic light would be somewhere else, in a different shape and violet could be in a completely different place relative to blue and red. I don't know if it is necessarily the red bump that arranges the curve like that (the red bump in the paper I linked to is far less pronounced than the one in the CIE1931 colour matching functions, and there is also a lesser bump in green which isn't shown in CIE1931 - I'm not sure exactly what they did with the response curves to generate the colour matching functions), but it is to do with the response curves. --Tango (talk) 02:04, 19 February 2009 (UTC)[reply]
Hooray, I've offended everybody. This is depressing. I shouldn't have written in that for-dummies way, it was insulting. Please take it as having been meant for someone else, someone who really is a complete beginner in this. I'll try to be less annoying in the future.
But... I still can't see where you're coming from with a lot of this stuff.
The XYZ coordinates don't approximate the LMS cone responses and weren't intended to—that wasn't one of the design criteria. (The design criteria were all coordinates nonnegative for real colors, efficient use of the space of nonnegative coordinates, and Y approximating luminance.) has two peaks because it's a linear combination of and . This doesn't help answer the question of whether has a second peak. There exist linear combinations of the XYZ CMFs that are everywhere positive and don't have that peak, for example the combination given by the matrix at LMS Color Space#RLAB, so the XYZ CMFs are consistent with there being no secondary peak.
"Violet is between red and blue when viewed in terms of polar coordinates centred at the white point in xy-space because of the response curves"—sure, but that's a very broad statement. Practically any set of three cone types will lead to a U-shaped curve, and white will always be somewhere in the middle of the disc formed by the convex closure since it's a combination of all the colors, so you will always be able to define a color wheel around white, and in any such color wheel the highest perceivable frequencies will appear to be intermediate in hue between the lowest frequencies and the not-quite-highest frequencies. There's almost nothing you can conclude about the cone responses from this wrapping-around behavior. The only thing substantially different that could happen would be if the curve doubled back in such a way that parts of it weren't on the convex boundary. I think that would be sufficient to prove the existence of a secondary peak in one of the cones. But the XYZ CMFs don't wrap around that way. Anyway, the perceptual effect of that would be different—it would mean something like high frequency light looking blue, higher frequency light looking violet, and even higher frequency light looking blue again.
"Green is the color seen by the green sensor...by definition." I know some people call it the green cone, but I don't think even those people would say that it sees green by definition. Green means perceptual green or light with a wavelength around 550nm. If it were possible to stimulate the M cone alone, the visual appearance would be similar to supersaturated 500nm light, i.e. cyan, if the hues extend in the way one would expect. An LMS color system would be kind of a violet-cyan-magenta color system, with the violet right at the end of the spectral locus, the magenta at around (0.84,0.16), and the cyan literally off the chart (no xy coordinates because X+Y+Z < 0). It's fine as a color space but I have a hard time believing anyone would refer to it as RGB (does anyone have a source that does?).
"The high frequency 'bump' in the red curve is the reason [for the perception of violet]." You're going to have to explain your reasoning, because I don't get it. If there's an extra bump in the L response then suppressing it would presumably change the curvature of the violet end of the boundary in xy coordinates. Maybe it would be straighter without the bump. But violet would still be violet. It would be a little more saturated but still pretty much the same hue—unless the end was shorter in which case it would be bluer, or longer in which case it would be purpler, but changing the curvature doesn't matter much. Let's do something more concrete and zero out the second peak in , even though that's much larger than any extra peak in L would be. That causes the cyan-blue-violet side of the boundary to become vertical, approaching (0,0) instead of (0.17,0) in the revised coordinates. Sky blue is also going to move toward the left, but the line from white through sky blue is still going to hit the boundary somewhere short of the very highest frequencies. So the frequencies higher than that will still have some red in them, assuming that blue is primary because of the sky. For that matter, look at the other edge of the spectrum. Psychological primary red isn't all the way at the end, so you might expect even lower frequencies to look a little bit like magenta, and in fact they do, at least in plausibly clamped spectra like this. That's definitely not due to a second peak in the S cone—the response of the S cone at those frequencies is indistinguishable from zero.
There are four psychological primary hues, red, yellow, green, and blue. Stimulation of one cone type in isolation doesn't produce any of these hues—M alone gives you something between green and blue and S and L alone give you something between blue and red, and none of those hues looks primary. So I shouldn't have said that red, green and blue are irrelevant to color perception, since they're three-fourths of that RGBY system, but they're not any more primary than the other fourth of that system and they shouldn't be confused with either the cone outputs or the various systems of 3D RGB coordinates. Of course RGBY and sRGB and LMS are all fine as color systems. I'm not saying that any color system is good or bad, I just want to use distinct names for them since they are all different. In particular I don't want to use the name RGB for the LMS system, because it demonstrably confuses people. (Trovatore at least was confused by it, and Steve, I'm still not completely convinced you aren't confused by it also.) "Red, green and blue cones" is not quite as bad since it's unambiguous, but it's still very confusing to beginners (I think). A lot of people think that the cones directly measure coordinates in RGB space, and I want to make it as clear as possible that that's not true. Not because it's going to matter in most people's lives, but because telling people things they don't need to know is what the Ref Desk is all about. If the original poster did need to know the answer to this question, we probably would have deleted it since it would be a request for medical advice.
Did you take a look at the paper I linked to? You can clearly see an increase in the responses of the L and M cones towards shorter wavelengths. I don't know the significance of them, but they're clearly there. You say pretty much any cone response curves will yield a U-shape, can you explain that? What's stopping there being a W-shape or even a straight line (which would make Steve's lecture title accurate - purple really would be a shade of green!)? --Tango (talk) 23:57, 19 February 2009 (UTC)[reply]
Actually, having given it some more thought, I can partially answer my own question. You would only get a straight line if the three cones were linearly dependant, which would be a very inefficient way of making an eye. --Tango (talk) 00:10, 20 February 2009 (UTC)[reply]
I think you can only get a W shape if at least one CMF has two big bumps in it. If they broadly respond to "high", "medium" and "low" wavelengths then you'll get a U. Even if it's a W the convex closure still looks like a "disc" and white is somewhere in the middle.
I just looked at the 1980 paper you linked. They're measuring absorbance of the photopigments, which is not quite the same as the cone fundamentals. I think the difference is that the cone fundamentals also take into account absorption by the lens and the macula. The photopigment spectra from here, which are based on papers from 1999 and 2000 (according to the site), also show an upswing, but it's at around 420nm, which is already well into the violet. The 1980 paper's results seem to show the upswing at around 450nm. I don't know the reason for that difference. The cone fundamentals from the same site (based on the same papers) show no upswing, since most of that light never reaches the cones anyway. It's not clear to me what should and shouldn't be interpreted as a peak, when it comes right down to it. I'd rather the peak not exist since that would show without a doubt that the argument for its existence is incorrect, but I still don't believe the argument even if the peak is there... -- BenRG (talk) 22:10, 20 February 2009 (UTC)[reply]
A W-shape would give a disc with white in the middle, but the hues would be in a different order. I think you would get red-yellow-blue-green-red (sticking with the same primaries as you were using above), with violet a bluey-green. (I'm working this out by visualising the colour space and kinda guessing - I should probably get to grips with the maths a little better and work it out properly...) --Tango (talk) 23:02, 20 February 2009 (UTC)[reply]
CIE 1931 color space chromaticity diagram equivalent tending towards black
The color question above made me think that there should be a triangle - analogous to the one above - with black at the center. Is there such a thing and what is it called. The two together should come closer to covering all colors visible to humans. I didn't want to stick this on to the above question because the two are only related. 76.97.245.5 (talk) 00:13, 17 February 2009 (UTC)[reply]
Provided you'd consider no light as black wouldn't different intensities of colored light give different results. The triangle seems to be all with the same intentity. (Oops there's two. Don't know in a hurry which one I should link.) 76.97.245.5 (talk) 01:19, 17 February 2009 (UTC)[reply]
The chromaticity diagram covers only 'chrominance' (ie 'color') and doesn't include 'intensity' or 'brightness'. To show all of the colors that humans can see you need a three-dimensional diagram with red, green and blue as the three axes. I have one of these on my desk at work - it's a perfect demonstration of 3D color space. You could certainly produce other diagrams as 2D slices through that cube at different angles. SteveBaker (talk) 01:28, 17 February 2009 (UTC)[reply]
When matter is created from energy, is the outcome randomly determined (of it being matter or anti-matter)? And if so, would this explain the predominance of matter over anti-matter in this universe? 70.171.16.131 (talk) 06:19, 17 February 2009 (UTC)OP[reply]
As far as I know, which isn't much compared to some refdeskers, energy can ONLY be converted to matter if the corresponding antiparticles are created at the same time. You can't pick one or the other; that would violate conservation of charge, etc. (Please correct where necessary.) -- Aeluwas (talk) 09:41, 17 February 2009 (UTC)[reply]
When matter is created from energy, such as in the photon-photon collisions or from matter particles colliding at high speed at CERN and elsewhere, conservation laws specify that some quantities stay the same before and after the collision. Importantly, the number of particles minus the number of antiparticles must stay constant, so if 2 particles collide, you could for instance get 8 particles and 6 antiparticles out of that collision. Known violations of these laws are heavily studied but so far noone has been able to fully explain the predominance of matter over antimatter in the universe, it's one of the big questions in physics today. If you want to learn more, CPT symmetry or books on quantum mechanics may help. EverGreg (talk) 11:32, 17 February 2009 (UTC)[reply]
protein to build muscle mass
Hello Wikipedia,
In order to comply with current gay body-fascist requirements, i'm looking to build muscle-mass so would like to know what i should eat. The supplements people say about 1g of protein per pound of body weight but others suggest that this is cobblers and i should just eat sufficient calories so that i'm rarely hungry. My problem is that these people have an agenda to either sell me supplements or magazines and i don't know who i should believe. Does anyone know any objective figures? (ideally based on good ol' fashioned peer-reviewed science?)
The gays have created a body-fascist movement? Or the body-fascist movement itself is inherently homosexual? Or perhaps it's just disdained? Maybe the fascists just like gay bodies? This is all very confusing...
Regardless, "objective" advice (of which there is effectively none -- I doubt that peer-reviewed science is in agreement on this one) is likely to stray into medical advice. If you don't trust the subjective advice of magazines, I suggest you try the subjective advice of a doctor, physical therapist, and/or other health professional who can take your personal circumstances into account. — Lomn14:19, 17 February 2009 (UTC)[reply]
The gay mafia must be behind the gay fascists. :-) But seriously, you need to exercise to build muscles. This will make you eat more and possibly crave protein (if you aren't already getting enough). You don't have to take any supplements or force yourself to eat more of any item to gain muscle mass, just eating what you want to eat will be sufficient. The exercise is the key. Eating more or taking protein/carb supplements without exercise will only make you fat. Unless you're going for the bear look, that probably won't help. StuRat (talk) 14:37, 17 February 2009 (UTC)[reply]
Do you go to a gym? If so, you can probably book a few sessions with a personal trainer and they will be able to give you nutrition advice (or, perhaps, refer you to a nutritionist) - they will be able to tailor it to your current diet, build, weight and your planed training routine and desired results. We can't do that. --Tango (talk) 14:45, 17 February 2009 (UTC)[reply]
When I researched this a few years ago, I didn't find much if any reliable scientific evidence in support of protein supplementation or even high protein diets. There seemed to be a minimal amount of scientific evidence in support of creatine supplementation. A Quest For Knowledge (talk) 17:10, 17 February 2009 (UTC)[reply]
Ah, see I read an article like this and wonder why we can't theorize about medical treatment. I would think there is at least as much legal trouble in store by recommending creatine. I realize you didn't really recommend it and this isn't directed so much at the former user as it is at maintenance of a general principle. As far as this forum goes, please talk to a doctor and not a GNC representative about supplements for building muscle. Seriously, a MD. You wouldn't believe what they have found in weight gain supplements. About your other question, what you should eat, I would say you definitely need to run a caloric excess to build muscle. That simply means you eat more calories than you burn in a day. Remember that working out and running burn a lot of calories. Here is a website that automatically calculates your basal metabolic rate(BMR) using a popular equation. On top of your BMR you have to add any calories lost through exercise to get a good estimate. A protein rich diet is a common paradigm of building muscle as well. Basically the goal is to daily store protein as muscle. Now, this won't make you look that good, but it will make you strong. Professional body builders usually rotate evry 3-4 months between a caloric excess to a caloric deficit. The result in the long run is loss of fat and large well defined muscles.
The complex ones are boring, it's the simple ones that are interesting. You can get as complicated a formula as you like by just coming up with a really complicated problem to solve. --Tango (talk) 13:49, 17 February 2009 (UTC)[reply]
Yeah, you can make arbitrarily complex equations for whatever you want. However, you asked which is the most complex equation in physics that I know, so I'll tell you the most complex equation that I remember actually using. It is as follows:
Magnetohydrodynamics will rank high on many people's lists because it has a lot of terms, effectively building up from "F=ma" for a single particle, accounting for all the forces involved. Plasmas encompass the many different domains of electromagnetism and Newtonian statistical mechanics, encompassing half of the fundamental forces recognized by the Standard Model. In some extra-special space-plasma cases, there can even be relativistic magnetohydrodynamics, adding another few terms. Other disciplines, such as subatomic physics, often introduce new conceptual ideas rather than adding additional terms to an equation. "Complexity" of a formula is sort of tough to decide; for example, if you wanted to solve the simple ballistic trajectories for thousands of catapults, the individual equations would be trivial but the implementation details to solve the equations simultaneously could be quite complex. At a certain point, physical equations cease to be represented as closed-form expressions, and will probably be represented as a computational physics simulation, numerical solver, or computer program. The complexity of such a representation can range in to tens of thousands of lines of computer code for numerical processing, data management, and user interface. Nimur (talk) 16:16, 17 February 2009 (UTC)[reply]
I don't know anything about the subject myself, but I've heard that workers in quantum chromodynamics routinely use computers to crunch formulas with millions of terms. They are sort of like Feynman diagram calculations in QED, except in QED the higher order terms become negligible quickly enough to make pencil and paper calculation tractable, but in QCD they need those huge computer calculations to get any actual numbers out. 207.241.239.70 (talk) 07:55, 18 February 2009 (UTC)[reply]
How can this problem be solved:
A mass of a liquid of density ρ is thoroughly mixed with an equal mass of another liquid of density 2ρ. No change of the total volume occurs. What is the density of the liquid mixture?
Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. SteveBaker (talk) 16:53, 17 February 2009 (UTC)[reply]
The Reference Desk will not do your homework for you. That said, I'll offer some pointers: Consider the volume of the first liquid to be x. What is the mass of the first liquid (there is a density-volume-mass relationship)? What is the mass of the second liquid? What is the mass of the mixed liquid? Now solve for density. — Lomn14:14, 17 February 2009 (UTC)[reply]
Event horizon and neutron star crushing question
A recent Scientific American article about the possible existence of naked singularities got me wondering about neutron stars and event horizons. Specifically, there is a certain amount of gravitational force across the spherical boundary of an object needed to overcome the nuclear forces that keep a neutron star from collapsing into a singularity. There is also a certain amount of gravitational force to bring a sphere's surface area escape velocity to the speed of light, turning the sphere's boundary into an event horizon.
What's not clear to me is that those two levels of gravitational force are equal. So my question, then, is how much gravitational force is needed to start the process of crushing a neutron star into a singularity, and how much gravitational force is needed to create an event horizon around the surface of a collapsing object? And if those two numbers aren't equal, could it be possible to have an object that is, at least temporarily, significantly denser than a neutron star but whose escape velocity is less than the speed of light and thus is not a black hole? (A naked singularity is presumably one such object.) 63.95.36.13 (talk) 15:19, 17 February 2009 (UTC)[reply]
You may find Quark star interesting, but it's not entirely relevant to your question. For a object of a given mass you have something called the Schwarzschild radius. This depends only on mass, so for the neutron star/black hole in your scenario, it is constant. Once the neutron star collapses to smaller than its Schwarzschild radius, it is a black hole and has an event horizon, before then it isn't and doesn't. The gravity of a black hole isn't any stronger than the gravity of anyone else of the same mass, the only difference is that you can get closer it its centre of gravity. Therefore, it is meaningless to ask how much gravity is needed to create an event horizon, the correct question is how small does an object of a given mass need to be to form one. If the gravity is great enough to overcome degeneracy pressure and collapse the star, then sooner or later it will get small enough to form an event horizon and become a black hole. Its density will continue to increase until it passes that point (after which it becomes rather meaningless to talk about density). --Tango (talk) 15:30, 17 February 2009 (UTC)[reply]
Thanks for the tip about Quark Stars; that's the first I've heard of them, and it's actually related to my question in that it sort of shows an example of a star that is in an intermediate phase matter (at least at its core) between that of a neutron star and a singularity. As far as whether all singularities are black holes, though, that's precisely what the naked singularity article in SciAm was discussing (ie scenarios in which a singularity for one reason or another is not within an event horizon). Interesting stuff. 63.95.36.13 (talk) 18:30, 17 February 2009 (UTC)[reply]
Tango: The gravity of a black hole isn't any stronger than the gravity of anyone else of the same mass, the only difference is that you can get closer it its centre of gravity — not strictly true, it matters where the mass is: shell theorem. —Tamfang (talk) 07:49, 20 February 2009 (UTC)[reply]
What could actually happen if two nuclear-powered and nuclear-armed submarines crashed into each other way beneath the sea? On the one hand we have PR flaks saying, oh, nothing to worry about, the tea sloshed out of the mugs and we'll have to re-paint, that's all. At the other extreme we have ... nuclear war, possibly? (Worst case scenario: If one of the bombs were accidentally activated, and then another nation felt called on to respond.) Or the in-between possibility, of the vehicle being totalled, shades of Texas road crashes. BrainyBabe (talk) 16:40, 17 February 2009 (UTC)[reply]
I'm just surprised there was not a need for a major rescue. When Kursk (submarine) hit a rock (or blew a dud torpedo, as the current consensus seems to hold), everyone perished despite best efforts to send help. To me the most amazing thing about such a scenario is the total information-vacuum. The capacity for a submerged submarine to communicate with the surface is limited (exact data rates are probably classified), but I suspect we are talking about a few hundred bits per second as an absolute maximum. This is barely enough to even send a distress call, let alone a full explanation of the scenario. And to imagine that these guys must have a special bit-sequence to initiate second strike! Let's all hope their bit-error rate is REALLY low. Between the highly-classified nature of submarines and simple logistics which limit the number of witnesses, I think the truth of any submarine accident is always pretty elusive. Nimur (talk) 17:20, 17 February 2009 (UTC)[reply]
The chance of a nuke detonating accidentally is close enough to zero as makes no odds. Smashing them, shooting them, blowing them up, whatever, won't have any effect, you have to fire neutrons into a critical mass of fissile material - that just doesn't happen unless someone makes it happen. The real risks (to the world - obviously there are risks to the submariners) are leakage of radioactive material (pretty unlikely) and loss of nukes which could then be recovered by terrorists or rogue nations (everything is so top-secret that they would have to have spies in just the right places to find out where to look, so this is a pretty low risk too). There is also a risk that one side may not believe that it was an accident and retaliate, but they wouldn't retaliate with nukes (loss of a submarine does not warrant mutually assured destruction), so you're just looking at a regular war, at worst. --Tango (talk) 17:55, 17 February 2009 (UTC)[reply]
Delving away from the scientific aspects of this question into the political aspects, it should be noted that France and UK are allies and have been for quite some time. It is unlikely a war would erupt between these two nations even if a nuke were detonated. Had this occurred between the US and the Russia, the situation might be quite different. I suspect a war would not break out, but there would be accusations and counter-accusations. Of course, if this had happened during the middle of Cuban Missile Crisis, all bets are off. A Quest For Knowledge (talk) 18:18, 17 February 2009 (UTC)[reply]
It was only after the collision and reports started coming in that it was worked out what had happened - neither knew who or what they had crashed into at first. If a nuke had gone off, there would never have been any reports and the UK and France would each have simply seen a nuclear detonation at the approximate location of one of their nuclear subs. What conclusions they would have drawn from that, I don't know, but they might well have acted before letting the other know they had a nuclear sub in the area, so before anyone could work out what had happened. --Tango (talk) 18:28, 17 February 2009 (UTC)[reply]
You may be amused/terrified to learn that deliberate provocations along these lines *did* occur during the Cuban Missile Crisis, including forcing Soviet missile subs to surface, and actually test-firing an ICBM! That's what you get with the Buck Turgidsons of the world running the show. --Sean21:59, 17 February 2009 (UTC)[reply]
OK, so far so good, but I posted on the science desk deliberately. What happens when a sub hits something (another sub, or a mountain for that matter), at various velocities? What would it take to knock a hole in one? What sorts of damage could an undersea collision cause? Could it become "stuck" down there, without massive other damage? BrainyBabe (talk) 19:05, 17 February 2009 (UTC)[reply]
I heard on the BBC Radio 4 this morning some submarine walla talking about a submarine that several years ago crashed into an undersea pinnacle at 30 knots. A crew member was killed and several others received serious injuries but the shell of the submarine remained intact and there was no damage to the nuclear fuel cell on board. Funny that we didn't hear about it. Richard Avery (talk) 19:50, 17 February 2009 (UTC)[reply]
the sea-hull is damaged, and/or control surfaces are damaged and function improperly: the sub must limp to its home port; if the damage is bad, it must surface and call for a tender
the prop is damaged, the driveshaft or its bushings bent or damaged, or the gearbox damaged - mild gearbox damage may be reparable or patchable at sea, for everything else the sub cannot make way and must call for a tender (it can remain submerged while it waits)
the sea hull is deformed to an extent that the hatches to the pressure hull (man hatches, torpedo tube hatches, missile tube hatches) leak, seals for the prop shaft leak, and/or the ballast system piping and its valves are damaged and leak - pumps can handle small leaks (if the sub remains at shallow depth); for more serious leaks the affected compartments must be evacuated and sealed, and the sub must surface
large scale damage to the pressure hull, or major damage to the ballast system - compartments flood and must be quickly sealed off to prevent the sub sinking. With more than a few areas waterlogged, or if the balast system is badly damaged or inoperable, the sub cannot surface. Crew must be rescued (the US Navy uses a DSRV, I don't know what arrangements if any the British and French navies have). 12-36 hours pass before rescue begins, and as the DSRV has a capacity of ~8 people, rescue of the boat's 100+ compliment takes some time. If the electrical systems have failed the air is not reprocessed and becomes rich in exhaled CO2; the crew resort to breathing apparatus with wearable scrubbers. If these become exhausted, or if insufficient are available (particularly if many crew are trapped in a small compartment) crewmembers begin to die from CO2 poisoning (it's my understanding that you die from CO2 poisoning before the hypoxia kills you).
damage to the pressure hull affects many compartments; too much of the boat floods for the ballast system to lift, and the boat sinks to the bottom of the ocean. In sufficiently deep water the remaining pressure hull fails under the pressure and the crew is killed.
Submarines are always very sturdily constructed to withstand the pressures they must face; military submarines (which must also withstand violent maneuvers and near-misses from depth charges) particularly so. Naturally they don't publish crash-test results, so we can't say which of the above scenarios are likely to result from collisions of a given speed. As noted above, it is very unlikely that a nuclear warhead will explode. There is a larger chance that the solid rocket motors of an SLBM will explode, or that the reactor encapsulation would be torn open to the sea, but it's difficult to imagine a non-explosive impact that could trigger either of those without also shattering the pressure hull and killing the crew anyway.
The film Gray Lady Down gives a fictional account of the rescue of the crew from a striken US attack submarine; despite being a "disaster movie", it's probably rather optimistic. Some of the crew of Kursk were alive for days after she was damaged; it would appear the Soviet->Russian Navy did not have an effective rescue technology (a DSRV sounds great on paper, but if the sub's hatches are damaged, or if she is lying at a funny angle, or if she's taking on water faster than the rescue equipment can arrive, then things are more complex). 87.115.43.168 (talk) 20:28, 17 February 2009 (UTC)[reply]
Per documentaries, it is the responsibility of the sub personnel to monitor the sound generated by other vessels to know what sort of subs or surface vessels are near them. A nuke sub is basically pretty loud and distinctive. Even without using active sonar, which would give away your position, you should know when another sub is on a collision course, and emit a sonar blip, or use underwater audio communications to warn off a friendly nation's sub or take evasive action so as not to hit an unfriendly nation's sub. Some skippers' careers are likely to have passed their zeniths. A collision of subs is apt to be a disaster, and smacks of negligence, like a collision of airplanes. Edison (talk) 05:58, 18 February 2009 (UTC)[reply]
French Defense Minister Herve Morin claimed " "These submarines are undetectable, they make less noise than a shrimp." His claim seems highly suspect. A large group of shrimp all snapping is actually quite noisy. A shrimp can produce a reported 218 db noise. "As quiet as possible" still leaves them with the Russian Sierra class at a http://forum.nationmaster.com/forums/viewtopic.php?f=7&t=740 reported] 120 decibels and the U.S. Los Angeles class at 110 decibels. By comparison, a loud rock concert is reported to be about 115 decibels, a power saw at 3 feet 110 db, and a motorcycle 100 db. There is a lot of heavy equipment operating on a submarine while it is in motion. Another source on the noise levels of various nations' subs, both diesel, battery and nuke, is at [4]. Why can't a sonarman or equivalent detect the equivalent of an approaching noise source of this magnitude? Edison (talk) 20:02, 18 February 2009 (UTC)[reply]
I guess there could be some chance of damaged reactors making a radioactive mess. As for bombs going off, the permissive action links should prevent that. (Update: Um, except on looking at that article, urk, the Brits apparently don't use them. This is technology that the US deliberately disclosed to the USSR in the 1960's to decrease the chance of accidental war, so I thought everyone used them.) 207.241.239.70 (talk) 08:01, 18 February 2009 (UTC)[reply]
The dark rift is nothing more than gas and dust obscuring our view of the lens-shaped galaxy. Because we're on the outer edge of the galaxy - we're seeing all of this 'stuff' edge-on and we're looking through a lot of it. Just as humans have often discerned patterns in stars ('constellations' - the 'signs of the zodiac', etc) - we also see shapes in the clouds (it's ALWAYS a "bunny"!), in the pattern of marias on the moon, faces on Mars - and so it's no surprise that people have seen (and named) patterns in these gigantic dust clouds. It's an example of pareidolia. SteveBaker (talk) 22:35, 17 February 2009 (UTC)[reply]
I was thinking more specifically. Xibalba is a Mayan mythology, and the Dark cloud constellation article mentions the Incas, whose mythology appears to contain some concepts common to the Mayans. I was considering adding mention of the Mayans to the Dark cloud constellation article. Astronaut (talk) 09:54, 18 February 2009 (UTC)[reply]
Well, if you are planning on changing one of our articles - you'll need some suitable references that state this fact explicitly. IMHO, yes, this is a reasonable example of that...but that's not good enough - you need a solid reference. SteveBaker (talk) 13:59, 18 February 2009 (UTC)[reply]
I've been drinking green tea recently. In the teapot, after a while the dry tealeaves swell up and can be clearly seen to be parts of a leaf. I'm wondering if there is anything special about the tea plant: would infusing or even eating the same amount of eg cabbage leaves be as good for you as green tea is supposed to be? 78.151.117.148 (talk) 19:07, 17 February 2009 (UTC)[reply]
I can't directly answer your question, but I went to school with our local swimming champion, who drank a litre of cabbage water every lunchtime: the school dinner ladies saved it for him! When I asked him why, he told me that the vitamins from the cabbage were actually in the water rather than in the cooked cabbage, and it was better for you than eating the cooked cabbage!--TammyMoet (talk) 21:25, 17 February 2009 (UTC)[reply]
Green tea provides ECGC, a powerful antioxidant. ECGC may protect against diabetes. Green tea has a reputation for increasing metabolism and reducing the risk of obesity. Cabbage is a cruciferous vegetable; cruciferous vegetables such as broccoli and cabbage are associated with a lower risk of cancer. Green tea and cabbage might both be considered superfoods.151.213.161.26 (talk) 23:37, 20 February 2009 (UTC)[reply]
Gold in volcano
I recall reading about an active volcano in Antarctica that has a large amount of gold in the volcanic ash. Is this just a tall tale, or does such a volcano exist? If so, which volcano is it? 65.167.146.130 (talk) 20:04, 17 February 2009 (UTC)[reply]
Ok, the ancient alchemists dreamed about turning lead into gold. I have heard that this is now possible using a particle accelerator or something and bombarding lead to break off protons and neutrons. Is the gold created in this manner a stable isotope, or will it be radioactive? 65.167.146.130 (talk) 20:13, 17 February 2009 (UTC)[reply]
Why is there a high concentration of catalase in the liver?
What specific purpose does the liver serve by having a high concentration of the enzyme catalase? Does the body pump most of the waste hydrogen peroxide produced to the liver to be treated there? Or is there another reason?
I can't find a definitive answer, but I believe, essentially, what Clockwork says. Peroxisomes are responsible (in whole or in part) for some functions that take place mainly in the liver (gluconeogenesis and fatty acid metabolism). I suspect this means the liver needs more peroxisomes, and also more catalase (many of the reactions involved in those processes are oxidative, and so could create free radicals and superoxides that would also lead to peroxide). Someguy1221 (talk) 23:14, 17 February 2009 (UTC)[reply]
February 18
Hodgkin's lymphoma and GHB?
While searching on the internet about Hodgkin's lymphoma I found on wikipedia an article saying that one of the risk factors is "Prolonged use of human growth hormone". I kept searching clicking on "human growth hormone" and found maybe a relation between GHB abuse and lymphoma. Why isn´t this mentioned? Am I wrong, has someone studied about this?
When I heard about GHB, 10 years ago, it was said that there were still no known long-term secondary effects of it´s use. But if now it´s getting clearer, please inform people. My friend suffers from Hodgkin's lymphoma and he used regularly GHB but he also has Aids. So, where´s the connection? Is the lymphoma related to Aids or the abuse of GHB? Are we blaming AIDS for it forgetting the risks of using GHB? and because both diseases have the fact of being gay (aids & lymphome) or a man (lymphome) as one of the risk factors (although to say this is politically incorrect, I apologise, but it´s true) aren´t we mixing up things and making people believe that GHB has no long term severe secondary effects. Every website I found about GHB doesn´t mention this relation, but it mentions it´s use as rape drug. I know many cases of lymphome and a few of rape. Are we not making patients irresponsible? In the process of living with a cancer and facing it´s treatment it´s important not to blame yourself but at least know that your behaviour can deeply affect your health - a change of behaviour will help to cure. I wish I could say all this to everyone with the same problem in order to motivate a behaviour change to a healthy lifestyle and the strong belief in a cure, especially with withdrawing toxins and cancer agents and bringing in anti-oxidants through food. (we are what we eat/consume). I would much appreciate scientific answer/ explanation about this matter. And if there is a relation between and no one found out, I should get a prize.
217.22.90.231 (talk) 00:15, 18 February 2009 (UTC)[reply]
First thing, human growth hormone is completely different from and unrelated toGHB (Trovatore pointed out that GHB is used by bodybuilders), which is a can be used as a date rape drug. The acronym used for human growth hormone is HGH, not GHB. The following scientific articles I found address the issue of HGH and leukemias and lymphomas.
I found the following medical case report which requires a subscription to read. Nicola Magnavita, Luciana Teofili, Giuseppe Leone: Hodgkin's lymphoma in a cyclist treated with growth hormone. American Journal of Hematology, Volume 52 Issue 1, Pages 65 - 66. One quote is "The suspected relationship between GH use and hematological malignancies represents a further, strong reason to discourage this [doping using HGH] practice."
This paper found that HGH stimulated the growth of fresh patient-derived lymphoblastic leukemia and myelogenous leukemia cell lines. This paper and papers citing it seemed to conclude leukemia and lymphoma patients on an HGH treatment should be closely monitored, and that giving HGH to patients in remission is probably not a good idea since relapse risk increases.
This well cited paper collects various leukemia cases that have occurred in people treated with growth hormones. I can't read it so I'm not sure what it concludes.
Finally this commentary evaluates the scholarly writing and information available since 2004 and concludes the following:"There are no data to prove that the intrinsic risk of leukemia is further exacerbated by GH treatment, particularly if the dose of GH is at the level of physiologic replacement. Never-theless, this possibility requires serious consideration by the physicians and the families involved, and absence of data should not necessarily be construed to mean absence of an effect."' (Blanche P. Alter: COMMENTARY: Growth Hormone and the Risk of Malignancy. Pediatric Blood & Cancer, Volume 43, Issue 5 (p 534-535) )
I personally liked number 5 on my list of papers. From the limited exposure I have had to this topic from researching your question it seems like there is reasonable evidence that human growth hormone use (what level of use?) may increase the risk of relapse among leukemia/lymphoma patients. There is less than conclusive evidence that HGH use (what level of use?) may increase leukemia/lymphoma development risk in predisposed people but not enough research has been done to nail down whether this is true and to what extent if it is. I get the feeling that the most endocrine researchers do not think that human growth hormone increases the risk of leukemia/lymphoma development in healthy unpredisposed people. Concerning diet, you should look at Diet and cancer. Barring obesity, eating a well balanced diet at best only slightly reduces cancer risk. Other factors are more important in the development of various cancers than diet. 152.16.253.109 (talk) 03:53, 18 February 2009 (UTC)[reply]
A side note here: GHB is an extremely important pharmaceutical in the management of narcolepsy and cataplexy. It is very unfair to stigmatize it as a "date rape drug"; this tends to result in onerous regulation that makes it difficult for sufferers to get the medicine they need. --Trovatore (talk) 04:47, 18 February 2009 (UTC)[reply]
I'm sorry that I phrased my response poorly in case that is what bothered you; I didn't go any further than the disambiguation page while trying to figure out how the questioner had managed to associate human growth hormone with date rape drugs. I struck out the offending part of my answer. Thanks for pointing that out. 152.16.253.109 (talk) 05:07, 18 February 2009 (UTC)[reply]
Sure. I'm a little sensitive about this because a dear friend of mine ran into this issue back in the 90s.
As to the connection — according to our article, one of the uses (some will say abuses) of GHB is by athletes who use it to stimulate the in vivo production of HGH. So that part of it, at least, has some foundation. The rest of his contribution seems extremely speculative. --Trovatore (talk) 05:33, 18 February 2009 (UTC)[reply]
I'm doubtful the onerous regulation has anything to do with the stigmitisation. The onerous regulation has to do with the fact it is commonly used as a date rape drug. This is unfortunate for those who have a medical reason to us GHB I'm sure but is little different from the fact that pseudoephedrine is heavily regulated in many countries because it's commonly used to make methamphetamine. Now whether those regulations are really necessary or effective is a valid question but clearly not one for the RD Nil Einne (talk) 09:12, 18 February 2009 (UTC)[reply]
Do you have any references that it is "commonly" used as a date rape drug, other than tabloid newspapers? According to this paper [5], 46% of claimed date-rape victims had ethanol in their blood stream, compared to 2% with either a sedative or "disinhibiting" drug which includes MDMA and benzodiazepines, aswell as GHB. I don't have access to the full paper, maybe in there it states the exact number of claimed date-rape cases where GHB is involved. --Mark PEA (talk) 15:36, 18 February 2009 (UTC)[reply]
I'm a bit surprised that GHB says next to nothing about its subjective effects. A bit of OR if anyone's interested: I tried it once circa 1996 (before it got a bad name) and got a buzz resembling that of alcohol yet without feeling stupid; I spoke fluently and more rapidly than usual. —Tamfang (talk) 08:10, 20 February 2009 (UTC)[reply]
- Thanks for explanations. On the Wikipedia article about GHB says: "Some athletes and bodybuilders also use GHB, as GHB has been shown to elevate human growth hormone in vivo." Doesn´t this mean that GHB stimulates HGH? And if it stimulates HGH it might increase the risk of developing Lymphome especially on predisposed people, for example, patients with AIDS? So besides the relation between AIDS and the Lymphone is it or not possible that consuming GHB, by estimulating HGH, in predisposed individuals increases the riskof Lymphome?
- With regards to the fact (or not) of being used as a date-rape, as far as I know, GHB disappears from the body very quickly so it makes it difficult to be traced after a rape. What I know is that if someone is overdosed with GHB especially if mixed with alcohol gets into a complete unconscious state. GHB is easy to find among the recreational users and because it´s commonly associated with other drugs it might trigger unplanned rapes. Of course there are exceptions and all rapes are condemnable. And All this doesn´t mean that GHB shouldn´t be used to treat certain conditions. My friend that has Lymphome started to smoke cannabis to get rid of the horrible pain that results of the treatment, and it surely works.
217.22.90.231 (talk) 19:06, 19 February 2009 (UTC)[reply]
Ionic Strength: am I doing it right?
I'm trying to figure out the ionic strength of a solution used for inducing insect flight muscle contraction. My PI couldn't help me with this, so I'm asking here. In short, my question is am I doing this ionic strength calculation right? The formula for ionic strength is given here. The components of the solution with concentrations are listed below. I included relevant pKas for the weak acids/bases. I can't figure out if pKa matters in this context since pKas are affected by ionic strength.
15mM Na4ATP (ATP pKa = 6.5)
15mM Mg(OAc)2 (acetic acid pKa = 4.76)
5mM CaCl2
20mM NaMOPS (Mops pKa = 7.20)
5mM EGTA (EGTA pKa = 6.91) (I have no clue whether or to what extent a chelator of calcium will affect the ionic strength contribution of calcium present)
5mM NaN3
Below I have separated the above into ions assuming complete dissociation for the salts and that the concentration of dissociated EGTA is negligible.
species
concentration
charge
ionic strength
Na
85mM†
+1
42.5 *10-3
ATP
15mM
-4
120 *10-3
Ca
5mM
+2
10 *10-3
Cl
10mM
-1
5 *10-3
MOPS
20mM
-1
10 *10-3
Mg
15mM
+2
30 *10-3
OAc
30mM
-1
15 *10-3
EGTA
5mM
0
0
N3
5mM
-1
2.5 *10-3
† That 85 mM is from 4*15mM + 20mM +5mM
The sum of all of those is 235 *10-3. Did I do the calculation right? If it helps, I know from experience the pH winds up being between 5.3 and 5.8 (I think 5.6?) and if I replace the 5mM CaCl2 with 10mM NaCl (a sum of 230 *10-3) the pH winds up being between 6 and 6.5 (I think 6.3?). I pH the solutions to 6.8 using sodium hydroxide afterwards, but I'm not going to worry about this yet because I want to make sure that I am doing the ionic strength calculations correctly in the first place. And a bonus question: If I have an enzyme that is in the form of a disodium hydrated salt, is it safe to assume for the purposes of ionic strength calculation that the enzyme will act as a divalent anion when in solution? 152.16.253.109 (talk) 02:42, 18 February 2009 (UTC)[reply]
My math agrees with yours, but I don't have much experience with ionic strength per se. I would expect EGTA to chelate the Ca++, but will "donate" an equivalent amount of cation in doing so, so this should not have much effect. Do you think your enzyme will be in a high enough molar concentration to have an impact? Others here may have more specific feedback. --Scray (talk) 04:57, 18 February 2009 (UTC)[reply]
I'm thinking about using creatine kinase at 300 units per mL. It is 185 units/mg. If 42 kilodaltons is the molecular weight, 1 unit per mL works out to be 1/7700 mols/L 1.29*10-7 mols/L so 300 units/mL is ~39mM 0.039mM which if divalent will add an extra ~117*10-3 0.117*10-3: a 50% 0.05% increase in ionic strength. (edit. redid those calculations and found I was off by a factor of 1000... I think that I am not going to need to worry now...21:33, 19 February 2009 (UTC)) 152.16.253.109 (talk) 05:39, 18 February 2009 (UTC)[reply]
Are you confident that 185 units/mg represents a direct conversion of enzyme units to mg of pure enzyme? I'm not. Using Google I see preparations with at least 1000 units/mg, which results in a more than 5-fold decrease in the estimate of enzyme molarity at 300 units/mL. Depending on the ionic strength of impurities, the other stuff in the prep has unpredictable effects. You might want to look for a really pure prep, or at least talk to the vendor about what they might know about ionic strength - the scientists at some of these labs are quite knowledgeable and accessible. I'll go back to my earlier point - it seems unlikely to me that an enzyme would be present at a high enough concentration to affect things like osmolarity, ionic strength, etc. Also, be careful about Dimensional analysis - I think you assumed that the "mg" in "185 units/mg" was "mg of enzyme", when it's actually "mg of fairly pure enzyme". --Scray (talk) 12:13, 18 February 2009 (UTC)[reply]
Same person, different IP. 185 units/mg is what the little plastic bottle says. I'm going to trust it. This is rabbit muscle derived creatine kinase by the way and an ... older batch at that. You are right about the prep being only fairly pure, but the contaminants are at most 5 percent by dry weight so their impact is (hopefully) reduced. It's better just to go ahead and try it out than to get mired down by trying to account for everything. If things go pear shaped, I'll give the makers a call, but as long as I have done the calculations above right I will go ahead and salt the solution to match the predicted ionic strength. I will also run a control using an "normal" solution batch too. I appreciate your advice so far, Scray! 65.190.207.110 (talk) 01:37, 19 February 2009 (UTC)[reply]
You have not said why you think contaminants are less than 5% by dry weight, but I wish you the best. I urge you to sign in using a username - the benefits are substantial, and I don't know of a substantial downside. --Scray (talk) 03:54, 19 February 2009 (UTC)[reply]
Voltaic pile chemistry
I have to teach a grade school science class in a few days. If anyone can provide the answer to these questions, thanks. Otherwise it is dustbowl empiricism. I plan to make a Voltaic pile and electrochemical cells. 1)How many grams of salt should be added per kilogram of water to make a saturated solution? 2)If zinc and copper are the electrodes used, would saturated saline solution or 4% acetic acid (vinegar) produce higher voltage and higher current? 3)Would a combination of vinegar and saline produce more voltage\current than either separately? 4)Would dilute sulfuric acid (perhaps one part battery acid to 10 parts water, such as was used in the early 19th century)) produce more voltage/current with zinc and copper electrodes than vinegar and/or saline? Thanks. Edison (talk) 05:46, 18 February 2009 (UTC)[reply]
That source says "35.9 g/100 mL (25 °C)" for solubilty of salt. Presumably the conductivity and output current of a copper/zinc cell would be maximum with that amount of dissolved salt in a Voltaic pile or electrochemical cell. Sounds good. How does that compare to vinegar or a vinegar/salt mixture, or dilute sulfuric acid for output current? I am looking for maximum short-term power, not long term output, which might involve adding nitric acid to dilute sulphuric, or which might require amalgamating the zinc plates with mercury (currently a big no-no, but common 19th century practice). I hate science fairs which have "potato batteries" with tiny zinc and copper electrodes and which can barely power an LED light or a wristwatch. Real batteries in the first decade of the 19th century produced substantial current and voltage, such as the 2000 volt, 1.5 amp battery Davy built at the Royal Society circa 1808. Edison (talk) 06:39, 18 February 2009 (UTC)[reply]
The easiest way to make a saturated salt solution is to get warm water and heap salt into it and shake it up, adding more salt until no more goes into solution. Then pour off the supernate. Unless you need to know how much salt goes into the solution don't bother. 152.16.253.109 (talk) 07:20, 18 February 2009 (UTC)[reply]
This google result seemed especially useful. I'm afraid the rest of this answer will fall under "dustbowl empiricism". I know from experience that leaving copper in a saturated salt in vinegar solution for more than an hour will tend to brown/pit the surface of the copper and may corrode the zinc. If you go with something like this and don't intend to replace the electrodes after every use, add the solutions just before starting, and wash off the electrodes with distilled water afterwards if you intend to reuse it. I've done a lot of chemistry demonstrations for schools and it is vital that you try out your cells beforehand, so you can sort out "irregularities" and are sure of what behavior to expect from the device. I would avoid bringing a sulfuric acid mixture if something else would work. If something spills it is more psychologically reassuring to the school, the teacher, and the kids' parents to know that it was just salt and vinegar or a little ammonia and salt rather than sulfuric acid or dilute battery acid. I'm sorry these are not the specific answers you wanted. 152.16.253.109 (talk) 07:12, 18 February 2009 (UTC)[reply]
If you are going to have the kids do the experiment - why not make it a proper experiment. Have some kids use saline and others use vinegar and see which ones get the best results. I agree that you should probably avoid sulphuric acid - even in 10:1 dilution it's not very nice stuff. This experiment is kinda messy because you have to stack these cells together to get a reasonable voltage out of them - so the possibility of getting dilute sulphuric acid on hands and/or clothes is high. SteveBaker (talk) 13:56, 18 February 2009 (UTC)[reply]
Probably will use brine and blotting paper for the Voltaic pile. I was considering making up one "state of the art 1808" cell with the dilute acid typical for the period we are covering, in addition to the usual wimpy potato battery. to show that an amp or so could be obtained for a short while until bubbles on the plates increased the internal resistance, in contrast to the milliamp or so from little dissimilar metal pieces stuck in a lemon or potato. I will forge ahead and test it out ahead of time. Is it to be expected that closely spaced electrodes in an electrochemical cell will produce higher current? Edison (talk) 18:14, 18 February 2009 (UTC)[reply]
In short: It's true. Many infections come in common "packs", so having an infection with one pathogen makes it much more likely to have a very specific secondary infection. For example: The common cold is caused by a viral infection, but this viral infection paves the ground for secondary bacterial infection. Such "combinations" of pathogens are rather common and can be regarded as a kind of symbiosis from the side of the infectious agents: they combine their abilities to be better able to infect the host. As for a very simplisitic functional explaination: Most infections interfere with our immune system, and in doing so they make it easier for other pathogens to proliferate in the infected region. Wikipedia does not really have much content for this topic, as most articles like superinfection and coinfection are very narrow and miss the biological point. TheMaster17 (talk) 10:32, 18 February 2009 (UTC)[reply]
When those in the advanced health professions study bacteria, they learn that there are a whole bunch of bacteria than normally live in and on the body. When you get a bacterial infection, it is usually because you are exposed to a virulent bacteria (one that has a well developed ability to cause infection). These bacteria usually secrete sticky substances that allow them to grow easily in large groups, like streptococcus growing in your sinuses. The other bacteria that normally live there without causing symptoms are then provided a great place to thrive and thus grow in much larger amounts than usual. Normally all you have to treat in these cases is the causative agent. However, most of the drugs that are prescribed in these cases are "shotguns" in the sense that they will probably kill all of the culprits anyway.
I won't go so far as to contradict him directly. I think he is referring to the fact that when our normal defenses against pathogens are compromised, the normal bacteria that live in and on us cause infection and they cause it all at once. The statistics about how common that and other mixed infections are is a doctor's field and I would say he knows what he is talking about. For a straight answer you would probably have to turn to epidemiology. Most epidemiologist are physicians and study things exactly like what you are talking about. I would think that bacterial infections would be among the most studied subjects within, but they tend to vary widely depending on your location within a state, not to mention your country or the world.
I would disagree with the assertion that "most epidemiologists are physicians". At least in the US, training in epidemiology is a separate Master's or PhD level pathway that does not necessarily involve medical training. While it is true that some physicians do obtain extra training in epidemiology, they do not make up the majority of epidemiologists. --- Medical geneticist (talk) 21:16, 18 February 2009 (UTC)[reply]
Neither would I openly contradict a doctor: they are in possession of our bodies and our health. I will have a look at epidemiology- Thank you so far. 93.132.168.56 (talk) 20:48, 18 February 2009 (UTC)[reply]
I'm currently studying this topic, so I decided to do some extra reading. I have referenced enough creditable sources to say that most bacterial infections are the result of exposure to a specific virulent bacteria. Diagnosis and subsequent treatment is based on identifying an exact bacteria to treat. However, I still won't say your doctor is wrong. I think what he meant was what I said in my initial response. After one infectious strain invades, it does provide a suitable environment for the overgrowth of others that were there to begin with. I will say he could have used a better word than "cause." ;) Also you could interpret that statement to mean something entirely different than what you did. He could have just meant that not all bacterial illnesses are caused by the same bacteria. So I would say to fault our own perception before faulting his intention.--Mrdeath5493 (talk) 21:56, 18 February 2009 (UTC)[reply]
Funny, my original question to the doctor was why couldn't we have a specific analysis of the infecting bacteria and have a specialized treatment for just that kind instead of broadband antibiotics. 93.132.168.56 (talk) 22:13, 18 February 2009 (UTC)[reply]
Perhaps there is a misunderstanding of what your doctor told you. For any given episode of infection, there is probably one main culprit at that given time and place. However, for any classes of infections, say ear infections or bacterial pneumonia or bacterial meningitis or urinary tract infections, there are a few "most commonly causing" organisms followed by a long list of "also can cause" organisms. This could be the explanation that your doctor was trying to give, when s/he told you that "bacterial illnesses are mostly caused by more than one kind of bacteria" as opposed to the explanations about superinfection and coinfection. --- Medical geneticist (talk) 22:45, 18 February 2009 (UTC)[reply]
With regard to antibiotic selection, the physician might start empirically based on the most likely pathogenic organism, or treat with a broad-spectrum antibiotic to get most of the likely culprits, or simply go by published guidelines (such as the AAP Red Book) that indicate how to treat a particular infection. There are certainly some cases where a bacterial culture and sensitivity will be performed to identify the pathogenic organism and treatment options, but not in every case. Keep in mind also that your own immune system is fighting the infection at the same time, so even a suboptimal antibiotic regimen may be enough to help you fight off the infection sooner. It is even argued that for certain types of infections we should avoid treating with antibiotics (thus reducing antibiotic resistance) and simply let the body take care of its own business. It sounds like you already have a good dialogue going with your physician and should continue to ask good questions! --- Medical geneticist (talk) 22:45, 18 February 2009 (UTC)[reply]
Ok, judging by your original question User:Medical geneticist has the answer I believe. It would require too much time, effort, and money to identify the exact bacteria in most cases. When your doc said many different bacteria cause infections he meant it could be any one of a number of possibilities. Just as an example I remember the normal flora and likely causes of infection in the sinuses with the acronym HAPPEN
H. influenzae
Aureus (referring to staph)
Pnemococcus (S. pneumoniae)
Pyogenes (referring to strep)
Epidermitis (referring to staph)
Neisseria
Of all those Strep. pneumoniea is by far the most likely. We know that it is overwhelmingly (~97% of strains) resistant to Penincillin, so we have to go with an Aminopenicillin like Amoxicillin or even skip that step and go with a Z-pack (very common). However, herein lies the flaw. Over half of people that present with symptoms of a sinus infection have a viral infection (which antibiotics will do nothing about.) Anyway before I get to far off the subject, when you doctor said more than one bacteria cause infection he was referring to situations like the list above (it could be any of them!). Your doctor knows what he is talking about.--Mrdeath5493 (talk) 23:42, 18 February 2009 (UTC)[reply]
So if any one infection is caused by a main culprit, why don't we have a PCR analysis to know what it is and subsequently treat that special one, avoiding to use antibiotics on viral infections or resistant strains? Is it too expensive yet? I imagine an analysis chip, produced in huge numbers with costs of few dollars, later even cents, that does a PCR and is sensitive to a few dozen of the most common critters. 95.112.165.196 (talk) 08:30, 19 February 2009 (UTC)[reply]
There are plenty of analytic methods that can determine the culprit, including PCR, it just depends on the situation whether or not your doctor goes to the trouble of finding out. Some things to consider in the equation: 1) the ease with which a sample can be obtained and the specificity of the culture results, 2) the utility of determining the exact organism (will it change your management?), 3) the severity of the consequences for the patient (this will also take into account the age and general health of the patient).
Examples:
Meningitis - somewhat difficult to get a sample (you have to perform a lumbar puncture), but critical in terms of knowing whether the patient has viral or bacterial meningitis. You absolutely don't want to let a person go untreated who has bacterial meningitis (in fact, most of the time the patient is treated empirically with broad spectrum antibiotics until the culture results come back after ~48 hours). The balance therefore almost always goes toward testing.
Urinary tract infection - easy to obtain a urine sample and perform a standard culture, useful in guiding therapy (there are a wide variety of bugs that can cause UTI), UTI is generally not immediately threatening to the patient but you certainly don't want it to progress to a kidney infection if not treated properly. The balance usually goes toward testing.
Otitis media - usually caused by a few different bacteria that can be treated similarly. It's impractical to obtain a sample of the pus for testing (by performing a myringotomy) and the typical ear infection will resolve on its own even if untreated. Hence, the balance goes toward empiric treatment using expert guidelines that have been developed.
Pneumonia - also caused by quite a few different organisms including viruses and bacteria. If the patient is coughing you can get a sputum sample but it will contain all sorts of bugs and therefore the specificity of the test is a little questionable. You could go further and get a bronchoalveolar lavage but this is a pretty invasive thing to do to someone for a routine case of pneumonia. In the end, the balance depends a lot on the overall health of the individual. Some cases will be treated empirically with a broad-spectrum antibiotic and other cases will be tested to determine the specific culprit and treated accordingly.
The bottom line is that the course taken for any given patient depends entirely on the circumstances and doesn't really boil down to a universal "lab-on-a-chip" test that instantly spits out information. This is why physicians go through as much training as they do, to be able to grasp all the uncertainties and come up with the right course of action. --- Medical geneticist (talk) 15:02, 19 February 2009 (UTC)[reply]
Al Jazir, Ancient Engineer?
I'm looking for a Wikipedia article on an early engineer by (what I think is) the name of Al Jazir. I believe he would have been alive in the same time as Archimedes, but that guess is a shot in the dark. I know The Discovery Channel did a few documentaries on the subject. His work was in elaborate timepieces and other scientific devices; perhaps in the vein of the Antikythera mechanism and other such devices. Also possible to been alive in the same time as the peak of Alexandria. Again, I'm almost certain the name was Al Jazir, but having searched all over I must have the spelling incorrect. Any help is much appreciated!
Doing a google search on "al jazir" and "mechanic" quickly brought up the name "al jazira" and/or "al jazari". We have a page, but he is not even close to contemporary to Archimedes. But he was a mechanic and has build time keeping mechanisms. TheMaster17 (talk) 10:16, 18 February 2009 (UTC)[reply]
All I wanted to do was increase my knowledge of the cubit stick, the first unit of length. But what was stated is a bit of a joke. suggest some-one tries watching the TV programme by the BBC (UK).
To even think it was invented by an Egyptian Pharoah would be pushing the realms of commonsense.
The cubit stick was invented by the person in charge of designing a building, and not a pyramid as stated here. The pyramids were built using precise measurements, so how could one have been built before units of measurement were invented?
The cubit incidentally, as described in our article was a unit of measurement (actually different ones were used by different people) so it clearly can't predate the invention of units of measurements Nil Einne (talk) 13:28, 18 February 2009 (UTC)[reply]
I don't see what's wrong with the article. The unit of length known as 'the cubit' has changed over time - different civilisations used different measurements. So when the Egyptians were building their pyramids, they would have chosen a standard for the cubit and stuck to using that exact measure for all of their work and everything would have come out OK. But the ancient Greeks used a different standard - yet they still called it 'the cubit'. The ancient Romans had yet a different measure with the same name. That wasn't at all confusing for them because each civilisation picked some distance and stuck by that - but it's VERY confusing for us looking back. To give you a concrete example - I spent some time a few years ago doing pro-bono computer graphics work for the guys who built a very carefully researched replica of a Greek Trireme (a kind of war-ship, rowed by a bunch of oarsmen) - it's called "Olympias". (I wrote a trireme battle simulation: [6] based on the performance data from the Olympias and was able to prove that some previous assertions about the way they fought could not possibly be true.) The guys who were figuring this out had the problem that no trireme has ever been found - not even the smallest part of these huge wooden structures has survived. But they knew how long the ship should be (in modern units) because they found remains of a shipyard where these vessels were built and stored - but when they came to figure out how the rowing benches were laid out, all they had was a written account that described the dimensions in cubits. Sadly - the account was written by someone who was not a native Greek and who used the 'wrong' distance for a Greek cubit. As a direct consequence of this, the rowing benches on the Olympias are just a couple of inches too tightly bunched and the people who have manned this modern replica don't have enough space to row efficiently. (It doesn't help that modern humans are on average a little taller than the ancient Greeks - but that's not the main reason). So the cubit article (as far as I can tell) is perfectly OK. Do you have a specific problem with it? SteveBaker (talk) 13:44, 18 February 2009 (UTC)[reply]
Does Radio Shack sell any weather stations that can hook up to your computer for data upload? If so, what is the cheapest but most reliable.Nick (talk) 15:27, 18 February 2009 (UTC)[reply]
I don't think that I got it at Radio Shack, but I have a little clock/weather station thing. It has a clock, internal temp/humidity sensor, outside (linked by radio) temp/pressure sensor, and it tunes into some AM-frequency (I think) national weather service. It has a USB connector to connect it to a PC to dump the history of readings. Looking at it, I'm rather surprised that it doesn't have a make/model. It is mainly a see-through LCD display with a small black plastic base. From memory, it was made by La Cross. Checking http://www.lacrosstechnologies.com/ will likely find something similar to what you want. -- kainaw™17:19, 18 February 2009 (UTC)[reply]
Following EC: Yes. [7][8]. If you are looking for what a particular retailer has to offer, it's best to go to their web site and search there. Alternatively you can use search terms with ".." in google (like "Radio shack", "weather station", USB, PC) That will narrow down results. You can then google for reviews of a model you like. These people [9] might be willing to share their opinions. [10]--76.97.245.5 (talk) 17:31, 18 February 2009 (UTC)[reply]
"The Scientific Community" at large cannot possibly comment on "conspiracy theories at large," you will really have to handle these on a case-by-case basis. For example, there was a lot of talk early on about the melting-point / breaking point of structural steel; I think a lot of construction engineering sources will be able to specifically comment on the structural integrity. But there are a lot of conspiracy-theories ranging from very minor political intrigues to very extreme, space-alien-interventions. It will be much easier to evaluate specific claims scientifically, rather than trying to lump all claims together. Nimur (talk) 16:04, 18 February 2009 (UTC)[reply]
There will be all kinds of reliable scientific sources that support the individual arguments of conspiracy theorists, but generally only when taken out of context and with lots of unlikely assumptions. I doubt you'll find any peer reviewed papers explicitly saying that there is a conspiracy regarding 9/11 (not in legitimate science journals, anyway - there are plenty of less legitimate journals that will publish anything), it's not really a scientific question - scientists may address individual points in the theories, but not the theory as a whole. --Tango (talk) 16:20, 18 February 2009 (UTC)[reply]
Well, me be blunt. I doubt that there are many if any reliable scientific sources that explicitly support 9/11 conspiracy theories. I suspect that the answer to my question is zero. Nevertheless, I still want to go through the excercise of actually trying to find out. Tango, you mentioned "There will be all kinds of reliable scientific sources that support the individual arguments of conspiracy theorists, but generally only when taken out of context". For the purposes of my question, the sources should specifically mention 9/11 conspiracy theories. As far I undestand the policy, to do otherwise violates the WP:SYN clause of WP:NOR, correct? A Quest For Knowledge (talk) 16:41, 18 February 2009 (UTC)[reply]
Well, if the sources are referenced by the conspiracy theorists then you can mention them without it being OR. If you want to try and find some reliable sources, take a look through these search results. I've looked at the first couple of pages and see a few things debunking the theories, most of the rest looks irrelevant. (You may be able to come up with better search terms - that was just my first attempt.) --Tango (talk) 17:25, 18 February 2009 (UTC)[reply]
Popular Mechanics did a well recieved debunking of the most popular conspiracy theories concerning 9/11.
One oddity (not necessarily due to a conspiracy: failures in design and operation (diesel fuel stored throughout on occupied floors)or in firefighting could doubtless equal the effects of a diabolical conspiracy) is that 7 World Trade Center, a modern highrise building which was NOT hit directly by an airplane, but set on fire by debris from the collisions, is the only modern high rise to collapse due to a fire. There was a recent case where a high rise in China was completely involved in flames due to fireworks and basically destroyed, yet did not suffer collapse. There is more than one kind of conspiracy. Besides terrorist conspiracies, more often one finds conspiracies to coverup poor decisions. The emergency power needs of tenants in a high rise should be supplied via cables from emergency generators and automatic throwovers to alternate utility feeders, rather than by having fuel storage tanks and fuel pipelines running through occupied floors. Another coverup (no media attention) has been the fact that after the NY Police Department helicopter rescued people from the roof of one of the World Trade Center building after the bomb blast in the 1993, the NY Fire Department asserted that rescue was their sole right, and insisted on automatically and securely locked exit doors from the restaurant to the roof, which could be opened only electrically from the command center in the middle of the building. This center was knocked out by the airplane hit, dooming any hopes of rescue from above. Yeah, I know the investigation said such rescue was impossible. The securely locked doors prevented anyone getting out on the roof to test the abilities of chopper pilots to lower a cable. In 1993 the Emergency Services Unit (police) had the ability to rappel from a twin-engine rescue chopper hovering at 1500 feet and chopping down obstructions so the copter could land. The north tower had a smoke-free area from which some of the trapped people could have been rescued, but for the fire department (which had no helicopters) insisting on rescue only by walking down the destroyed and impassible stairs. Face-saving assertions in investigatory reports also constitute conspiracy. Other post-attack conspiracies might involve denial of the danger from the dust that workers had to breathe. Edison (talk) 18:05, 18 February 2009 (UTC)[reply]
If anyone had asked my advice on how to provide emergency power to an office high up in a building, I would have strongly criticized in advance the notion of storing fuel at various locations in an office building. It is contrary to common and recommended practice. Ditto for making it impossible to get out to the roof of a highrise, when the possibility of air rescue had been demonstrated. "Everyone can always walk down the stars" is faith-based evacuation. The 20/20 hindsight quibble usually applies to things no one could have foreseen. Edison (talk) 00:28, 19 February 2009 (UTC)[reply]
Put it this way: so far as the issue of scattering generators around with fuel storage tanks on occupied floors: I installed emergency power prior to 9/11 in numerous places and did not do it that way, because it is idiotic per se. Put the fuel far away from office space and bring in electrical cables. This is a giant "DUH" factor, not really an either/or question so far as safety is concerned. Not "2020 hindsight" quibbling to defend the indefensible. People in NY City likely wanted vanity stroking generators after the outage of the 1960's and had the illusion that they were better off with the generator next door, and never mind the fire hazard. A careful search of the files would likely find objections by qualified electrical engineers and fire safety experts which were overridden by executive know-it-alls. Edison (talk) 04:39, 21 February 2009 (UTC)[reply]
I think the other question is whether sources will actually say such a theory happened - they are far more likely to show that it could have happened (i.e. "there's no reason why the government didn't have this involvement") which is far short of a sources suggesting it did. - Jarry1250(t, c)21:11, 18 February 2009 (UTC)[reply]
As I mentioned above, I believe that the articles relating to 9/11 conspiracy theories are giving undue weight to fringe theories. But right now, I am focusing on researching the topic. In the coming days/weeks (depending on the amount of my free time) I will probably raise a NPOV issue with the NPOV Noticeboard. If any rational skeptics (and I am sure that there are plenty on this board) would like to assist me in my efforts, your help would be greatly appreciated. However, before I raise the NPOV issue, I want to do more research so I am prepared to present a thorough case. For now, my initial thoughts can be found on main article's discussion page, [14]. If you'd like to help, feel free to add this page to your watchlist. A Quest For Knowledge (talk) 03:41, 19 February 2009 (UTC)[reply]
Has any there been any research to determine if there might be any connection between Herpes simplex virus type 1 (HSV-1) (cold sores) and glaucoma?
1. From http://en.wikipedia.org/wiki/Glaucoma it's clear that "Raised intraocular pressure is a significant risk factor for developing glaucoma" but is not the exact cause. It's clear because "in some populations only 50% of patients with primary open angle glaucoma actually have elevated ocular pressure.", there is an "inconsistent relationship of glaucomatous optic neuropathy with ocular hypertension", and "another person may have high eye pressure for years and yet never develop damage".
2. "Glaucoma is a group of diseases of the optic nerve involving loss of retinal ganglion cells". OK, now have a look at http://en.wikipedia.org/wiki/Herpes_simplex. "After initial infection, the viruses move to sensory nerves, where they reside as life-long, latent viruses" and "Following a primary infection, the virus enters the nerves at the site of primary infection, migrates to the cell body of the neuron, and becomes latent in the ganglion."
Do the latent viruses damage the ganglion? Do frequent recurrences or outbreaks damage the sensory nerves? Does it only migrate to the primary site of infection or could it migrate to the optical ganglion?
3. There is currently a new drug under development for glaucoma; "Peripherally selective 5-HT2A agonists such as the indazole derivative AL-34662 are currently under development and show significant promise in the treatment of glaucoma." and from http://en.wikipedia.org/wiki/5-HT2A_receptor "5-HT2A also happens to be a necessary receptor for the spread of the human polyoma virus called JC virus."
Is this just coincidence as the author implies by the phrase also happens to be? Is the polyoma virus related to HSV in any way? Both can cause latent infections. Could the 5-HT2A receptor also be a factor in HSV infection?
"Scientists discovered a link between HSV-1 and Alzheimer’s disease in 1979" and "Recent research supports the previously obscure theory that Herpes simplex virus type 1 plays a role as a possible cause of AD in people carrying the susceptible versions of the apoE gene".
In some people Herpes simplex 1 causes Alzheimer's disease and brain damage!? That's extremely interesting in itself, but back to conjecture; could HSV damage the optic nerve?
Think about it !!!!!!!!
Just kidding, and I don't expect any prizes either. Also I'm asking about the common "Orofacial herpes", not "Ocular herpes ... a special case of facial herpes infection, known as herpes keratitis", although I find it interesting that there is an ocular form of the disease. Feline herpesvirus http://en.wikipedia.org/wiki/Feline_herpesvirus_1 herpes also has ocular symptoms. Poor Bertie, he was such a handsome cat.
Finally I've read this over several times and can't see any way in which it could be interpreted as a request for medical advice.
Well you might love this then: "Herpes simplex virus: an important etiology for secondary glaucoma." Jones R 3rd, Pasquale LR, Pavan-Langston D. Int Ophthalmol Clin. 2007 Spring;47(2):99-107. Review. I can't even find an abstract for it, let alone the entire paper. Someguy1221 (talk) 18:29, 18 February 2009 (UTC)[reply]
My university has access to this paper (which doesn't seem to have an abstract). I'm not supposed to be forwarding these things out, so if you don't email me then I won't email you back reasonably quickly with the paper as a PDF attachment. Honest. – ClockworkSoul21:37, 18 February 2009 (UTC)[reply]
This is the last of these questions I'm going to answer, and only briefly - I won't be posting any follow-up. I still don't think you're really listening to what we say anyway. "Peg" is a very vague word, and not one I would use to describe the shapes in the diagrams in that article. The shape of a mountain above the rest of the surface could be better described as a peg (upside-down) - it's wide at one end and narrow at the other, which most pegs I've seen are. I'm not sure I've ever seen a peg that was wide in the middle and narrow at both ends. As for the stability thing, I've never heard of mountains stabilising the Earth, but if they do then I guess it's just a coincidence, yes. --Tango (talk) 17:19, 18 February 2009 (UTC)[reply]
After edit conflict - Is 'what a coincidence? You provided no textual explanation of what subject your talking about, let alone what the actual question is. I shouldn't have to click an off-site link just to find out what your question is. A Quest For Knowledge (talk) 17:21, 18 February 2009 (UTC)[reply]
I'm not answering these piecemeal from now until eternity. As I offered before - if our OP will make ONE question containing a list of all of these claims in a neat little numbered list, I'll be happy to answer them all in one go. But we don't need these long threads every time one of these questions comes up because each time we have the same set of replies about the question being too vague or whatever. It starts to look trollish - and we don't feed trolls here. So - please make a complete list of all of these 'The Quran claims...' questions and ask them all at once in one question - then we can answer that and call it a day. Thanks! SteveBaker (talk) 18:50, 18 February 2009 (UTC)[reply]
How you'd really get anybody here to sit up and take notice is if you can find somebody who was inspired by a passage in the Koran to look for evidence showing that what people thought was wrong. For instance if before tectonic drift was accepted someone said their holy book says the earth is split apart in the middle of the oceans and they went ahead and found the mid Atlantic ridge, then you'd get a few converts maybe. I don't suppose you'd find such evidence compelling but, trust me, it really is he sort of thing which would excite a scientist. They can be quite gullable with just a little real evidence. Dmcq (talk) 20:06, 18 February 2009 (UTC)[reply]
The simple answer to this, and any other related questions, is that the author of the website is taking what is clearly intended to be a piece of metaphorical writing, finding a correspondence in science, and trying to make a point from it. I've seen plenty of the same thing done with the Bible. Typically you will find there are other similar metaphorical statements that happen not to be scientifically true; if you ask the website's author about them he will say "they are just metaphors". DJ Clayworth (talk) 21:54, 18 February 2009 (UTC)[reply]
Exactly - in the very same place where it discusses mountains as 'pegs', it says (18:47): "On that day we shall remove the mountains, and thou wilt see the earth as a level stretch"...in other words, the Quran says that the earth is flat. It says this not just once but in many places: 13:3, 15:19, 18:7, 19:6, 21:30, 35:40, 41:10, 43:10, 50:7, 51:48, 55:10, 78:6, 79:30 and 88:20. One or two of those might be intended figuratively - but all of them? If you can pick and choose between hundreds of statements - you're bound to find one or two true ones amongst many, many false ones. The question is whether it would have made predictive statements that people could use. Clearly it cannot because it's saying so many things that are clearly false. But this isn't unique to the Quran - it's true of every other religious book you might come across. The christian bible says (Matt 4:8) "Again, the devil taketh him up into an exceeding high mountain, and sheweth him all the kingdoms of the world, and the glory of them."...something that's only possible if the world is flat. The Torah kinda-sorta says the Earth is round - but it still says things like (Psachim, p.94b), the Gemara states that fountain waters at night are warmer than by day because the sun warms up the water during the night from underneath the earth. SteveBaker (talk) 23:08, 18 February 2009 (UTC)[reply]
A perfect sphere is, from the spheres perspective, a perfectly two dimensional (flat) area. Gravity operates on a two dimensional plane. The difficult one is magnetism which operates on a one dimensional plane. The Bhagavad Gita and the Śrīmad Bhāgavatam were describing spiritual theories on Anti matter thousands of years before Abraham was around. It is strange coincidence that such works always prove the more popular. ~ R.T.G05:35, 19 February 2009 (UTC)[reply]
The problem with all of that is none of it is science. Look, to bring back the analogy I made last time this came up, a blindfolded man may hit a bullseye in a game of darts once in a while; it doesn't mean that darts should properly be played blindfolded. Merely because ancient texts propose ideas which, if read liberally and with lots of squinting, could possibly maybe refer to modern scientific concepts; it does not mean that such texts are "scientific" in any way. Science is not a collection of facts or statements about the world; its a process that leads to an understanding of the world. If a conclusion is reached that one did not arrive at by science, then the conclusion is not scientific, even if scientific processes eventually reached a similar sounding conclusion later. The Bhagavad Gita did not describe anti-matter. The Bhagavad Gita described stuff that, after physicists discovered what anti-matter was, could kinda-sorta be seen to have some parallels to actual anti-matter. It doesn't mean that the Bhagavad Gita is a scientific text!!! --Jayron32.talk.contribs06:41, 19 February 2009 (UTC)[reply]
I love how some people trust the ravings of a lunatic 1000-2000 years ago who thought he heard God/an angel, and choose to distrust the decades or centuries of observation, experimentation, and logical reasoning by well-educated people using advanced equipment that has lead to modern science. Our OP may be a little better because he may not think science is crap, but still, to think the Quran and real evidence are equal shows a degree of irrationality I cannot comprehend. --Bowlhover (talk) 07:12, 19 February 2009 (UTC)[reply]
will ,, its all been said before, but , why dont we take the quraan as an exception , assuming it could be true,without comparing it to other books.
first ... assuming its just coincedences , this could be true if you find one or two but it will be more that acoincedence if you find alot more . but first make sure that you do understand it completely .
after all ... its your search to do .. some will say its just crap and others will look for the truth ...
after all this argument , i think the result will be nothing ,,, theres alot to talk about ... and theres alot of ides .
so ... this link will be my last contribution in this subject
Not many years ago, someone found a lot of surprising 'predictions' hidden in the Torah, and wrote The Bible Code. People scoffed that you can find anything you like by the approach he used, if you look cleverly enough. The author challenged skeptics to find, by the same approach, a prediction of the assassination of a prime minister in Moby-Dick. They did, abundantly. To ask us to consider whether the Quraan is special, without comparing it to other books, is unscientific: to measure specialness, we need to know what is normal. —Tamfang (talk) 08:35, 20 February 2009 (UTC)[reply]
Questions which are vague and just say "Look at this web site and tell me what you think" do not seem like legitimate material for the Reference Desk. "Tell me what you think" is not a legitimate question. Such questions should be removed in the future. If the questioner has a question, he should ask the question, and not direct us to click on some web site. Edison (talk) 04:45, 21 February 2009 (UTC)[reply]
conservation of energy
suppose we have two capacitors charged accordingly and then the positive terminal of one is joined to the negative terminal of the other & vice versa then there occurs a loss in electrostatic energy,i.e. the initial electrostatic energy that was stored in the two capacitors was more than it is after short circuiting the two.
WHERE DOES THE ENERGY GO?? {note:the loss occurs even if we use resistanceless wires}--scoobydoo (talk) 17:38, 18 February 2009 (UTC)[reply]
There will be an electrostatic attraction between the terminals before they connect, that would involve a loss of energy. Whether it accounts for all the energy or not, I don't know...
Anything that doesn't dissipate in the resistance will be radiated as an electromagnetic wave as the charge bounces back and forth. The wire forming he loop will have a small inductance. Dmcq (talk) 18:30, 18 February 2009 (UTC)[reply]
>>the whole problem comes from a physics book i found which says that two capacitors 5microF & 6microF were charged across 24V and 12V resp and then connected with reistanceless wires the +ve terminal of first one with the -ve terminal of the second and asks about this loss. I calculated the initial energies as 1.44mJ and 0.432mJ {applying E=1/2cv^2} and the loss comes out to be 1.77mJ upon redistribution of charge.If the attracion is responsible as you say then the work done by these forces will be stored as electrostatic potential energy which should be accounted for by the eqn.Another notable thing is that if the +ve plates are joined together than also there is loss but it is less than the previuos one which also remains unexplained.
One useful analogy for this problem is a mass-spring system, but with the Spring constant replaced with capacitance and deflection replaced with voltage. With such substitutions, the equations for stored energy and total series capacitance are preserved. Then with the values given, it is more intuitive to see that when the two "springs" are coupled together, they will begin oscillating. Someone42 (talk) 10:40, 20 February 2009 (UTC)[reply]
Adenoidectomy
So my brother is getting his adenoids (Pharyngeal tonsil) out and I was doing some research to see what the procedure is, side-effects, etc. when I came across this line near the end of the Adenoidectomy article: "Adenoidectomy is often performed on children aged 1-6, as adenoids help the body's immune system." This makes absolutely no sense to me; if they help the body's immune system, wouldn't it be useful to have them during your childhood years? Also, if anyone has had this procedure done / knows about it and wishes to give me some info, it would be much appreciated. The article is a little sparse.
Thanks! -Pete5x5 (talk) 19:36, 18 February 2009 (UTC)[reply]
P.S. Just in case anyone was wondering, I'm not requesting medical advice; my brother has already spoken to the appropriate medical professionals and is getting the procedure done regardless of how much I know about it. ;) -Pete5x5 (talk) 19:39, 18 February 2009 (UTC)[reply]
This procedure is very common because some small children have recurrent infections affecting their tonsils. Although it sounds bad, removing them is almost always done in an effort to prevent infection. Check out the Tonsillectomy article.
Following EC: I'm not anywhere near an expert. I assume that the sentence means that the operation helps the body fights an infection like Streptococcal pharyngitis and Tonsillitis. The fewer repositories for pathogens are in the body the less work the immune system has to do. It doesn't say anything about it being done as a prophylactic measure. The phrase should probably we reworded. 76.97.245.5 (talk) 20:32, 18 February 2009 (UTC)[reply]
Seems like some undue confusion and a poorly written article here. The adenoids and tonsils are part of the immune system, somewhat like lymph nodes, that are involved in the immune surveillance of the nasopharynx and oropharynx. These tissues can get inflamed, swollen and painful when a person gets an acute infection (either with a virus or bacteria) -- it's like a battleground where your immune cells are fighting, killing, and dying. Having the adenoids or tonsils removed does NOTHING to help the body fight off infection. They aren't typically "repositories" for pathogens. The entire human body (including the nose and mouth) is essentially a microbial culture chamber (it's just that most of the "bugs" we live with don't cause problems most of the time). While removal of the tonsils and/or adenoids may prevent them from becoming infected in the future, this isn't why they are removed. Some reasons given for surgery include chronic infections such as an abcess or symptomatic enlargement that leads to difficulty breathing (sleep apnea) or feeding. --- Medical geneticist (talk) 21:36, 18 February 2009 (UTC)[reply]
OK, for my own curiosity then: why do the adenoids and tonsils get inflamed? Presumably they are not the primary targets of infection, so what brings the battlefront to them? Macrophages that can't keep their meal down? Dendritic cells that get infected with an intracellular pathogen and then migrate? What exactly is the mechanism that causes inflammation in those tissues? Franamax (talk) 01:13, 19 February 2009 (UTC)[reply]
Inflammation is not the same thing as infection. Secondary lymphoid tissues (tonsils, adenoids, other gut-associated lymphoid tissue [GALT], in addition to lymph nodes and spleen) can become inflamed in the process of generating specific immune responses (B and T cells) for antigens delivered by blood (to spleen), lymphatics (lymph nodes), or the mucosal surface (tonsils, adenoids, other GALT). Sometimes these tissues do become infected, but I just want to emphasize that inflammation does not mean infection. That being said, the processes that bring antigens to these tissues can also bring the pathogens (floating free or contained within phagocytic cells). --Scray (talk) 04:09, 19 February 2009 (UTC)[reply]
It would be great if we understood "macro" elements of the immune system that well, but we don't. I can speculate about why the Waldeyer ring is important, and have read quite a bit about it, but systems biology is in its infancy. --Scray (talk) 05:31, 21 February 2009 (UTC)[reply]
The tip of a laser beam
A Klingon bird of war drops out of the Star-trek universe and finds itself in our Einstein universe. Furious to be deprived of all those fictional technologies, they fire all their weapon systems to see which still work. A debate starts as the laser gun doesn't produce the well-known and picturesque streak of light. The captain says the laser could not work in this universe because, the laser beam as all electromagnetic waves has to obey the Maxwell equations. On the other hand the speed of light is limited, so the beam has a "tip" in front of which nature has no chance of knowing that the beam will arrive in an epsilon of a second. Space there has to be absolutely undisturbed by the not yet arrived beam, and this would contradict with any solution of the Maxwell equations.
Why does that contradict the Maxwell Equations? If you solve the equations the speed of light just appears naturally, it's fully part of the solution, it isn't something that Einstein added on later. --Tango (talk) 20:59, 18 February 2009 (UTC)[reply]
Well, obviously it doesn't. But it's strange that a continuous and differentiable field should have a "tip" where it gets constantly zero. So how does the tip look like? 93.132.168.56 (talk) 21:11, 18 February 2009 (UTC)[reply]
It looks like the frontier of a wave, because that's what it is. I guess it will be gradual - the laser won't turn on in an instant, it will take a certain (very small) amount of time to get from zero to full power. --Tango (talk) 21:17, 18 February 2009 (UTC)[reply]
I assume you mean "look like" metaphorically? You obviously can't see the tip unless it is on your retina, in which case it looks like a point of light. --Tango (talk) 21:18, 18 February 2009 (UTC)[reply]
Since the laser is question was from a Klingon Warbird I'm guessing your retina had better register it pretty quickly before it, along with the rest of you, is fried. DJ Clayworth (talk) 21:46, 18 February 2009 (UTC)[reply]
With "look like" I mean what does the field equation look like. And I will also be satisfied if someone can point me to what the wave front (field equation in a neighborhood) of a spherical electromagneticale wave looks like, because it's there but it doesn't exist further away than c times t from its origin. 93.132.168.56 (talk) 21:28, 18 February 2009 (UTC)[reply]
Nor could it - if it did, that would imply that some aspect of the field was travelling faster than light - and that's a "no no". Information can't travel faster than light - so if some kind of field disturbance arrived ahead of the light itself then you could (in theory) know that the Klingons fired the laser before the beam itself arrived - which would imply that the information travelled faster than light. SteveBaker (talk) 23:35, 18 February 2009 (UTC)[reply]
Causality occurs only within the light cone that describes temporal evolution. Within it, you use the standard equations. Outside of it, you have no idea that the events in question have happened yet, so you don't care. I don't understand the confusion though - everyone knows that Star Trek was a documentary. :) Franamax (talk) 00:19, 19 February 2009 (UTC)[reply]
For the sake of illustration, let's assume spherical symmetry, so this reduces to:
It is straightforward to demonstrate that any solution of the form:
Will satisfy the wave equation, where f is absolutely any twice differentiable function of one variable. The condition that the wave originates at r = 0 and time t = t0 is simply the constraint that f(a) = 0 for all a ≤ c t0. Otherwise Maxwell's equations allows the traveling wave to have absolutely any twice differentiable pulse shape. Dragons flight (talk) 01:01, 19 February 2009 (UTC)[reply]
Why did doctors administer calomel and bleeding in the 18th and 19th century?
Calomel is a mercury compound which doctors in many countries routinely administered to anyone who was sick or injured in the 18th and 19th century. "Calomel" redirects to Mercury(I) chloride. That article says it was given as a "purgative" until the patient salivated, but [[Purgative} redirects to Laxative. Which end of the patient was the doctor trying to get something from? Benjamin Rush used it in the 1790's to "remove poisons from the body" although the calomel was itself known to be poisonous and ancient medical writers had said as much. Did no one in the medical colleges try a series of patients with and without administration of that poison and bleeding? A surgeon of the 1840's administered calomel and bleeding to patients with severe head wounds, and cites 4 cases of patients recovering from penetrating head trauma, sometimes with brain tissue exposed (he might not be mentioning those who died). Mercury compounds and bleeding along with other likely lethal treatments were given to President Harrison ([15] Botanico-Medical Recorder, 1841,Vol X, No. 2, page 22). That publication charged (1841, Vol X, No 1., pagepage 23) that calomel and bleeding had likewise killed former President Washington. I find botanical doctors to be the ones criticizing mercury as the standard cureall of the 19th century medical establishment ([16] Vol X, No. 1, Oct 16, 1841, pages 13-15), along with bleeding. Only around 1910 do books seem to cite data showing calomel was ineffective and detrimental to health. Can we be confident today that the bleeding and calomel were in every instance detrimental to the patients' recovery (Definitely not seeking medical advice)? Edison (talk) 20:49, 18 February 2009 (UTC)[reply]
Not quite sure what is up with calomel, but if you haven't already you might want to check out bloodletting. I'm pretty sure in the 18th century a lot of medicine was based in religion and superstition, so who knows why they did what they did. Something I find interesting is the medieval use of leeches in medical treatment has somewhat returned (European Medical Leech).
I can't imagine either calomel or bloodletting being beneficial in any way. I think it would be safe to say that, in general, they were detrimental. Think about your response if a doctor told you that they were about to just let you bleed as a treatment for anything. Now, as an antibacterial safety mechanism, bleeding does flush out a wound; but intentional cutting is another story.
There is (as far as I know, exactly) one disease in which the modern primary treatment is periodic bloodletting, that being polycythemia rubra vera. Bloodletting is used occasionally for a few other diseases in the present, though generally not as the primary treatment. So we can be assured that nearly all 19th century bloodletting was detrimental, but not all. - Nunh-huh00:05, 19 February 2009 (UTC)[reply]
The practice of medicine in the 18th and 19th centuries bears little resemblance to today's medicine. In general, practitioners of that era probably did not systematically study the efficacy of their remedies. The concepts of randomized controlled trials (or as you put it, "a series of patients with and without administration of that poison and bleeding") are a modern phenomenon. See epidemiology and various links within evidence-based medicine. See also patent medicine for other examples of quackery promoted as "medicine". At least in the USA, regulation of medicines is a 20th century phenomenon. --- Medical geneticist (talk) 21:13, 18 February 2009 (UTC)[reply]
In History of medicine#Modern medicine the 18th and 19th and even early 20th century doctors get a total pass from any criticism of their fanatical devotion to bloodletting and calomel. The discussion of "modern medicine" just claims that in the 19th century there were all these great advances in chemistry and bacteriology. The section appears to be in serious need of balanced historic coverage of actual medical practice, and the harm likely done to many patients by bloodletting and the administration of heavy metals, in efforts to "remove poisons." Edison (talk) 22:38, 18 February 2009 (UTC)[reply]
Looking here, vomiting is mentioned so it seems that mercury chloride causes pretty general upset. "Saliva" could be a generic term that covers esophageal reflux / mini-pukes, i.e. when stuff comes out of the patient's mouth, you know you've given them enough "medicine".
As far as help/hinder, well at least it's not methylmercury (the really bad kind) and it seems pretty obvious that the body has a vested interest in getting rid of it. This could actually have some beneficial effects, such as dramatically reducing the population of intestinal parasites; and in general, system challenges can have a stimulating effect if they don't kill you outright.
I'd imagine that any beneficial effects would be totally random though, and selection bias would lead people to only report the ones that "worked". You are talking about a period of history when the concept of statistical analysis had not yet been dreamed up. Until that concept came along, it's fair to issue a free pass.
And anecdotally in re the early-20th century, in the 1910's and 20's there was a brief craze to use thorium as a general curative. It did seem to work in small doses, possibly because of the stimulative effect of toxins very low on the dose-response curve (but I've been shot down on the hormesis idea here before :). Then, people who used more of it had to get parts of their jaw removed because of tumours &c and it kind of died off after that... I don't have a link for that and I gave away the history magazine I read it in long ago, but it did happen! Franamax (talk) 00:49, 19 February 2009 (UTC)[reply]
Let's not be too judgmental of those who went before us. I'm sure that most practitioners of the art were well-meaning, even if they were ignorant of the ways things really work. We too could be subject to harsh criticism by Wikipedians of the 22nd century... ("Can you believe they used to use surgery to take out the appendix??? How barbaric!" or "What about the chemotherapy and radiation therapy they were using -- how much harm did they do to people with those supposed therapies?") --- Medical geneticist (talk) 00:31, 19 February 2009 (UTC)[reply]
While we're indicting the old medical establishment, remember that good old-fashioned lobotomys, administered basically with an icepick through your tear duct, were still being given as late as the 1950's. Rosemary Kennedy had her brain scrambled in 1941; it was considered a "cutting edge" procedure then... --Jayron32.talk.contribs04:43, 19 February 2009 (UTC)[reply]
One book I found noted that when the "allopath" or "real doctor" from a medical school came in say the 1850's he did venisection (bloodletting) with his lancet first thing, as surely as his present counterpart would listen to the heart and lungs with his stethoscope. This immediately caused the patient to settle down and stop raving and thrashing around, decreased the fever and flushing. Of course it also put them one foot in the grave from loss of blood, but to family members it may have seemed an improvement. If Gramps died after the doctor dosed him and bled him, it was "God's will." Then the calomel and other harsh drugs caused vomiting and bowel movements, which had some face validity as "flushing out the poisons." A downside of calomel was loss of teeth and of pieces of the jawbone. Other "alternative" practitioners likely did no more good with their herbal remedies, but usually did less harm. The typical 19th century doctor's visit with the typical bloodletting, calomel and emetic, apparently caused about as much trauma as present day chemotherapy, with no benefit whatsoever. They likely caused greatly increased morbidity and mortality compared to the control condition of no doctor visit, until doctors understood the germ theory and had treatments for bacterial infections. This does not deny the effectiveness of surgery to suture wounds and set broken bones: patients often benefitted even though the surgeons were unaware of germs. Edison (talk) 05:06, 21 February 2009 (UTC)[reply]
I was looking through some old xkcd comics (I was bored, and you know, there's worse ways to spend your internet-time), and came upon this this comic that contains a science reference I've never heard of. It talks about some hypothesized supermassive object outside the visible universe that's pulling a bunch of galaxies towards it.
Hmm, aside from my disappointment at seeing an xkcd I've already read and enjoyed, my first thought was actually the Great Attractor. Are "Great Attractor" and "dark flow" about the same thing? Franamax (talk) 00:56, 19 February 2009 (UTC)[reply]
Well, it points towards some of the odder theories that have been used to explain the anomalous behavior of the Pioneer probes - which includes stuff like 'dark flow'. SteveBaker (talk) 03:34, 19 February 2009 (UTC)[reply]
Oh-mi-god. Like reahl-ii! - Now I have to review every single xkcd to see the tooltips! Never tried that before. :)
And what is the deal with the Pioneer satellites (beyond the fact that they are still working)? Should I frame that as a separate question thread? I just know that things aren't working out as expected beyond the heliopause... Franamax (talk) 03:44, 19 February 2009 (UTC)[reply]
How about an inflatable arm chair? When you sit on it (increasing the pressure) it sinks down (decreasing the volume) and goes back again when you stand up. (You can replace the arm chair with a lilo, an inflatable mattress, or any other non-elastic inflatable thing - elastic things, like balloons, work a little differently.) --Tango (talk) 02:34, 19 February 2009 (UTC)[reply]
For that matter, the same applies to car tires when the car is lifted off the ground for maintenance. When the car's on the ground and its weight is on the tires (increasing the pressure), the bottom of each tire flattens (reducing the volume of the air inside). Also in the realm of tires, consider a bicycle pump: the manual air pump you might use for inflating bicycle tires. Each time you stroke you handle in, you reduce the volume inside and this raises the pressure. --Anonymous, 04:31, February 19, 2009.
Thanks! Anything that goes the other way? Increase the volume to decrease the pressure, or decrease the volume to increase the pressure. Reywas92Talk02:42, 19 February 2009 (UTC)[reply]
Not exactly everyday but... a syringe without a needle is usually available from a veterinary office to administer liquid meds to your pet. Fill part way with room temperature water, seal the opening with your thumb, withdraw the plunger and watch the water boil at room temperature due to the decreased pressure resulting from the increased volume. -hydnjotalk03:48, 19 February 2009 (UTC)[reply]
Nothing tempers feelings of being smart like fielding questions from an inquisitive child. This evening, my daughter asked me what keeps your eyes shut while you sleep. My first thought was that having the lids shut was the neutral position, but that's not so; when I relax my facial muscles, my lids go to half mast and dead people don't close their eyes either. Googling around gives answers to some related topics, but generally miss the mark. So, what's the deal? Are certain muscles kept taught during the sleeping hours (excepting the usual flutters, etc.) Don't the muscles become fatigued? Matt Deres (talk) 04:34, 19 February 2009 (UTC)[reply]
I've taken care of quite a few critically-ill patients, some of whom required deep sedation and neuromuscular blockade. Uniformly, those people need ointment and often mechanical closure (tape is often used) to prevent exposure keratitis (I am amazed that WP has no actual content on exposure keratitis). Of course, my experience is just OR, so here's a quote from an article on exposure keratitis in the intensive care unit:
Thus, it is an active process. There are plenty of important things we do in our sleep. If we did not keep our eyes closed, we would be at significantly greater risk of blindness. Certainly, some people have their eyes partly open during sleep; this is mitigated somewhat by of upward rotation of the globe during sleep. HTH --Scray (talk) 05:51, 19 February 2009 (UTC)[reply]
...and some people have their eyes completely open during sleep, or at least sometimes during sleep. Anecdote time: my father, for one. My parents are divorced, and my brother and I used to spend every other weekend at my dad's place. When I was really young -- pre-school age, I guess -- we all slept in the same bed, and I remember several times when I woke up in the middle of the night to find him staring at me, or the ceiling, or something else, depending on what position his head happened to be in. It spooked the crap out of me, because there was no recognition, no movement, no comprehension in his eyes; they were just completely empty. No wonder, 'cause he was asleep -- it's not as if he was in the driver's seat at the time. When I got used to it, it was just funny, but those first few times, it was really creepy and, well, alien. It just wasn't something that jibed with my experience of how humans interact, at all. -- Captain Disdain (talk) 07:02, 19 February 2009 (UTC)[reply]
I'd say it takes a muscle contraction to either open or close the eye lids, but they will normally stay at their current position, otherwise. Note that the eye lids of the dead stay however they are left. It's quite possible for muscles to contract during sleep, though, as heart beats and breathing both require this. StuRat (talk) 14:01, 19 February 2009 (UTC)[reply]
As I said above, neuromuscular blockade leaves the eyes open. I provided a quote from a reliable source above, stating that it is an active process. Rigor mortis can leave the eyes open or closed, but that's an active process (involving muscle contraction), hence the "rigor" part in the name. The OP asked whether keeping the eyes closed during sleep requires muscle contraction, and the answer is yes. --Scray (talk) 00:13, 20 February 2009 (UTC)[reply]
When I read that quote, that "Eyelid closure is an active process...", it sounds like they refer to closing the eyes, not keeping them closed. If your interpretation was correct, all dead people would have their eyes open until rigor mortis sets in, right ? This doesn't seem to be the case. StuRat (talk) 04:45, 20 February 2009 (UTC)[reply]
Fully opening the eyes is an active process. Closing them is active (and was the OP's question). Midpoint seems to be the neutral position, and that's where I've seen the eyes of people under pharmacologic paralysis. In people who have just died peacefully, I've seen the eyes closed and slightly open - but I have not made a study of the time course, or changes in this. --Scray (talk) 05:54, 20 February 2009 (UTC)[reply]
The original question was "what keeps your eyes shut while you sleep" not "what causes your eyes to shut initially". The fact that any dead people keep their eyes fully closed before rigor mortis implies that no muscle contraction is required to maintain this state. StuRat (talk) 13:36, 20 February 2009 (UTC)[reply]
As for dead people, their eyes tended to be open. It was common in olden times to place coins on the eyes to keep them closed. Embalmers now use cement to keep the eyelids closed.[17][18]. Edison (talk) 05:16, 21 February 2009 (UTC)[reply]
Weight Scales
Hey, everyone. I have a question refering to the weight scales that you use to measure lightweight things. I only recall the act of figuring out the weight: first, you must calibrate it; then, you have to move the dials, and it would either even out, get heavier, or get lighter. I have completely forgot the name of this weight measurer! Help, and thanks.--Miss Hollister (talk) 06:32, 19 February 2009 (UTC)[reply]
The description ("calibrate via dial, add the weight to be measured, adjust to cancel it out") sounds like a torsion balance (which is actually a type of spring scale not a "balance"). Useful for measuring very small forces, and not listed on the Weighing scales page. DMacks (talk) 06:51, 19 February 2009 (UTC)[reply]
Aristotelian perfect heavens and Galileo
I've repeatedly read that Galileo used his telescope to prove that the Moon was not a uniform, unblemished body, shattering the Aristotelian view of perfect crystal spheres. But the lunar maria are quite visible with the unaided eye -- how could a view of perfect unblemished moon be held? Or is this one of those common but incorrect beliefs like 'Columbus proved the earth was round to Queen Isabella'?
Also, I've repeatedly heard that there are no European records of the Crab Nebula supernova, but there were in other cultures: this is supposedly attributed to the Church's influence, but in the 1050s much of Europe (especially the Scandinavian parts), while maybe Christian, definitely weren't dogmatic. Could it simply be that the records didn't survive? 128.194.250.39 (talk) 07:06, 19 February 2009 (UTC)[reply]
Galileo/Moon - The point was not the dark maria, which anyone can see, but the mountains. In any event, the person who banished the notion of crystal spheres wasn't Galileo, but Johannes Kepler.
Crab Nebula - From what we can tell, nobody in Europe noticed Sn1054. In the middle of the Dark Ages, astronomy was not a major concern. One would have to be quite familiar with the night sky to know that one particular star hadn't been there last week. Altogether, in order for us to have records, four things would have to have happened: (1) someone noticed the star, (2) they reognized that it had not been there before, (3) they made a record of it. and (4) the record survived. All four are low probability. So while the problem might be point 4, more likely it's 1, 2, or 3. +
SN 1054 says it was bright enough to see during the day for about 23 days, but I don't know if it was as bright as the full moon. Bear in mind it would still have been a lot smaller then the moon. It's also suggested it may have been referred to in Irish monastic annals. Edit: Sorry I didn't look at the article properly. The peak magnitude has been estimated as -6 which while brighter then Venus and an ISS flare, is no where near as bright as the moon and isn't even as bright as an Iridium flare. Nil Einne (talk) 10:48, 19 February 2009 (UTC)[reply]
OK, that makes a lot more sense. It would still have been noticeable, but it wouldn't have been as likely to have been recorded and remembered. (I'm still rather surprised it wasn't taken as some sort of omen, though, as comets were.) 165.91.80.170 (talk) 19:42, 19 February 2009 (UTC)[reply]
I would think a more likely explanation for why it wasn't noticed in Europe was bad weather when the event occurred. Perhaps they had rain/clouds/overcast skies on those days, while there were clear skies elsewhere. StuRat (talk) 13:56, 19 February 2009 (UTC)[reply]
The supernova was apparently recorded in early July 1054. It would have been relatively close to the Sun in the sky hence not so easy to observe during the day due to Sun glare and mostly below the horizon during the night, pretty low on the horizon in the late hours / early morning (along with a sunrise) at European latitudes. In other words, it was probably not as easy to spot as its alleged brightness would have you think. At latitudes closer to the tropic the supernova would have been somewhat higher on the horizon in the late hours of the night, so maybe a little easier to spot (which may or may not explain why the Chinese recorded it and not Europeans).
I would not dismiss weather out of hands either, I expect the supernova wasn't a magnitude -6 throughout the whole of July, a few days of clouds *might* just have hidden it from sight when it was most obvious, though I'm just guessing here.
Anyhow, it would have appeared in the sky as a bright Venus, which would not have been particularly shocking to anyone but someone keeping track of the planets and preferably awake late in the night. EquendilTalk03:07, 20 February 2009 (UTC)[reply]
The article on grooves said that the initial theory about grooves found carved into rock was that they were used for sharpening swords, but this has been disputed because (among other reasons) some of them are the wrong shape for sharpening swords.
Leaving aside the other reasons, if someone carved a groove for sharpening a sword hundreds or thousands of years ago, wouldn't the shape have been widened or altered by weathering in the present day, thus making it unsuitable? Or does weathering not work quickly enough? --86.159.223.93 (talk) 08:17, 19 February 2009 (UTC)[reply]
The article says that many of the grooves are in limestone, it's difficult to see how you could use such a relatively soft material (made of calcite, hardness=3) to sharpen a sword, even a bronze one. As to the weathering, some modification of the grooves in the limestone would be expected over periods of thousands of years, but probably not for the other rock types. Mikenorton (talk) 13:46, 19 February 2009 (UTC)[reply]
I had the same thoughts. Why wouldn't they use a harder mineral for sharpening swords ? Note that weak acids can also dissolve limestone, such as acid rain after a volcanic eruption. StuRat (talk) 13:47, 19 February 2009 (UTC)[reply]
Lemon juice might work, but would of course also change the flavor. Why do you need to prevent oxidation ? It will just cause the juice to turn darker brown, like cider, right ? What's wrong with that ? StuRat (talk) 13:40, 19 February 2009 (UTC)[reply]
Perhaps ascorbic acid (aka. Vitamin C)? I'm pretty sure it helps prevent oxidation on split fruits, so I suppose it'd work in apple juice as well. Adding too much will no doubt make it taste (more) sour, though. -- Aeluwas (talk) 14:54, 19 February 2009 (UTC)[reply]
Cover it up so that no air can get to the surface, or as little as possible. (Cling film is good.) Put the container in a cool dark place until ready to drink. (Pantry or fridge is good.) BrainyBabe (talk) 15:01, 19 February 2009 (UTC)[reply]
BTW searching for "oxidation" leads to Redox, which sounds like a brand of sneakers or band or punks, take your choice. Or a literary term. Or a Landseer painting. I digress.... The article has nothing on oxidation in food preparation, which is a lacuna, though it does have a section for biology. BrainyBabe (talk) 15:05, 19 February 2009 (UTC)[reply]
I know cut apples oxidize, but I did not know that apple juice did. The strategy seems simple though, keep it cold and keep it from being sloshed around. A layer of lemon juice on the top would help as mentioned above. Just remember for oxidation, you need oxygen. So, keeping it from moving keeps oxygen from diffusing any more than necessary into the liquid. Keeping it cold lowers the ambient energy and thus makes chemical reactions, in general, less likely. So, fridge + plastic on top (as already said) sounds like the answer to me.--Mrdeath5493 (talk) 18:50, 19 February 2009 (UTC)[reply]
A layer of lemon juice? Does lemon juice float on apple juice? They're both mostly water, surely they just mix... A layer of oil on top would certainly work, but you may not want to drink the apple juice afterwards...--Tango (talk) 23:36, 19 February 2009 (UTC)[reply]
here is a random recipe for making homemade apple juice from teh iterrwebz. I used this google search to find it. Oxidation isn't a big deal here. Oxidation makes whole apples mushy and brown, which some people find unpalatble, but it isn't harmful in any way. Considering that if you are making homemade apple juice, you are masserating and mushing up the apples anyways, all the oxidation that is going to happen will have already happened by the time you get to bottling the juice. The juice is perfectly safe from further oxidation at that point, though some ascorbic acid or citric acid, as mentioned above, may have a mild preservative effect, extending the shelf-life of the homemade apple juice. --Jayron32.talk.contribs02:35, 20 February 2009 (UTC)[reply]
Coffee and brain
How does coffee affect our brain? Is it like a soft cocaine, that inhibits the serotonin re uptake or is it like an amphetamine that makes us release serotonin? —Preceding unsigned comment added by Mr.K. (talk • contribs) 13:24, 19 February 2009
Wow, wikipedia's english article on caffeine is pretty extensive. It does leave one thing kind of vague, why does consumption of this substance result in arousal? I would first consider the reticular activating system. This is an area of the brain that serves to maintain consciousness. It does this by diffusely stimulating the brain. The neuronal pathways coming from this area go to all parts of the brain. While you are awake there is constant excitatory stimulation traveling from the RAS to the rest of the brain. More excitatory stimulation leads to nerve communication being easier to establish which leads to more nerve activity. The more nerve activity there is, the less likely it is you can ignore it (your surroundings, your thoughts, noises, etc.) and go to sleep. As an analogy I would say that the RAS is like a volume knob to all sensory input. If you ever undergo anesthesia for a surgical operation, the drugs they give you basically mute the RAS, thus you go unconscious. Anyway...
So, what does that have to do with caffeine? Caffeine has a "disinhibitory" effect which means it subdues a system that normally is inhibitory or works in a way that opposes the RAS. The result is an essentially diffuse excitation and thus increased awareness/wakefulness. The brain is so complicated we still can't fully explain how it works. What I understand about it is that it contains a complex system of excitatory processes balanced against inhibitory processes. No matter if you increase an excitatory process or subdue an inhibitory process, the end result is the same....more excitation>more awareness>more going on inside your head. --Mrdeath5493 (talk) 18:37, 19 February 2009 (UTC)[reply]
Imagine you were to travel back in time to, say, the Permian, and you had to stay and live there for a year. You know you're traveling back 275 million years ago but you don't know on which part of the Earth you're going to appear, only that you'll appear on dry land.
If you were only allowed to bring five (5) modern objects with you, what would be the best choice? I thought about the following:
Water purifier (drinking water is essential for life)
Storm-proof lighter (fire keeps you warm and helps you cook)
Swiss knife (comes handy in many situations)
Net (for catching food)
A medical kit (for treating injuries and diseases)
Don't worry about a water purifier - you can boil water to make it safe to drink. A Swiss Army knife probably isn't particularly useful, I'd prefer a simpler, lighter, more reliable knife. For a lighter I would probably go with flint and striker or similar - the simpler the better. You can make a net fairly easily from plants, snare wire would probably be a better tool to bring. If you're allowed a whole first aid kid as one object, then are you allowed a whole survival tin? If so, that has pretty much everything you need. A survival tin, a first aid kit and a decent knife - if you have all of those, you stand a good chance of surviving wherever and whenever you get dumped. --Tango (talk) 16:03, 19 February 2009 (UTC)[reply]
This is no different than "If you were stranded in xxxxx what would you need to survive?" There are thousands of survival books and now we have plenty of survival TV shows. Just read the books or watch the shows and decide what you think you will need. -- kainaw™16:21, 19 February 2009 (UTC)[reply]
There are many interesting and (potentially) unanswerables here. What would the human digestive and immune systems feel about the biology of the Permian? Do you have to worry about purifying water or getting infections at all - none of the bacteria/viruses of the time has ever encountered a modern human immune system. Is there actually ANYTHING you can eat there? Perhaps there are trace elements or vitamins that you need that are simply not present in animals or plants in the Permian? I don't think there were any grasses or flowers in the permian (I could be wrong about that) - so no grains in your diet. Getting dietary fibre could be hard. If you tried to live on meat alone, you'd pretty soon get in trouble. I agree that a swiss army knife is probably better than a simple knife - but I'd want a customised one...I see no point in taking a philips screwdriver, a USB thumbdrive or a corkscrew to the Permian - but the magnifying glass, tweezers and such could be invaluable. Your lighter will run out of fuel - so you'll want something more like a steel rasp that you can strike rocks against to make sparks. I'd want to take something like a cooking pot - so I can actually boil water (you didn't take anything to boil it in!) and make soup from whatever critters I catch, melt snow for drinking water in the winter. Most of the land in the permian was one gigantic desert - so if you're going to be dropped on land at random - you're going to die for sure! The CO2 content in the air (around 1000ppm) is at the upper limit of what is recommended for outdoor air quality - you're going to stand a good chance of suffering from headaches and nausea. If you make your home in a cave or someplace else with limited airflow - you could get into deep trouble. SteveBaker (talk) 16:31, 19 February 2009 (UTC)[reply]
There's a hard decision to make, between providing for immediate-needs vs. long-term needs. This largely depends on personal preference and estimation of the environment you will encounter. Often, the most critical items of the first few days turn out to be consumable and non-permanent (things like the very first meal, first blanket/clothing, toilet paper). Without those items, you will find life very uncomfortable and possibly even be unable to pursue longer-term solutions (for example, will you really be able to weave yourself a blanket out of ... Permian insect silk... if you die of hypothermia after the first two nights?) On the other hand, there is a strong inclination to only bring things you know you cannot re-build in any reasonable amount of time (like a nice forged-steel knife or ground-glass optical magnifier or some aspirin), with the hope of getting multiple uses out of each of those sorts of items. How often will you need a magnifier (rarely, for starting fires and so forth)? But when you DO need it, it will not be remotely possible to build one on short notice. As I mentioned, a blanket is probably easy enough to make, but you are going to want that on day 1 (environmentally dependent, of course). Steve brings up some very interesting points about Permian Earth, which will be an awfully foreign place (from the perspective of molecular biology). Nimur (talk) 18:13, 19 February 2009 (UTC)[reply]
I would have thought the human immune system encountering a virus it had never met before would be a bigger problem for the immune system than vice versa.
Anyway, I'll take as my 5 items: the machine that brought me there, the manual that explains how to use it to go back, a canister of time machine fuel or whatever it needs to go back, and in the event that I'll have time to kill while it recharges or whatever, a ham sandwich and a porn mag.
Don't tell me "you can't take the time machine, it's not modern, it's futuristic". In order to take me back it has to be in the same point in time as me. So regardless of where or when it came from, at the point I have to go in it, it's modern. --86.159.223.93 (talk) 18:13, 19 February 2009 (UTC)[reply]
Sadly, the rules say you have to stay there for a year. By then you'll definitely be reduced to reading the porn mag "for the articles" - assuming you didn't already need it to start a fire. You don't need the time machine - the you-in-your-future can pop back with a spare machine in a year from now - assuming you survive that long! ;-) 18:19, 19 February 2009 (UTC)
You have to pick yourself up once the year is up? That's an impressive paradox! It can be done consistently, though - took me a few attempts, but I got there! --Tango (talk) 18:42, 19 February 2009 (UTC)[reply]
Oh sure! For time travellers, it's the only way to go. Firstly, you can be sure the future-you will know exactly where permian-you will be on the pickup day - secondly, they know to come early if you're about to be eaten by a rampaging...erm...therocephalian (OK - I had to look that one up...but I'm pretty sure they rampage!) - fourthly, if for some reason you don't survive for the entire year, your family can avoid wasting the outragious cost of a time trip to fetch you. Of course if you screwed up and somehow accidentally changed the future...not so good. SteveBaker (talk) 18:50, 19 February 2009 (UTC)[reply]
I'm thinking you need better shelter to survive for a year.
I thought the Permian was much hotter than nowadays, so shouldn't it be warm enough to keep you from freezing to death? And, regarding the high carbon dioxide content of the atmosphere, couldn't it be solved by not exercising too hard, and therefore taking full advantage of what little oxygen you've got? --83.56.184.105 (talk) 20:06, 19 February 2009 (UTC)[reply]
I'd say:
-a good survival knife
-A pack full of food and water for the first few days
-A good sleeping bag
-Some means of making fire
-A very sturdy pot with a well-fitting lid, both for cooking and for storing water
Water will be a problem, but finding it (which I can't think of anything to bring that would help with that), not purifying it. I *severely* doubt any Permian waterborne disease could affect humans -- this was before any mammals.
275 mya is a little colder than modern Earth, so some nighttime shelter would be necessary. It's unlikely to be cold enough during the day to need a parka or anything -- ordinary
One big advantage is that this is before 275 million years of evolutionary arms race, so Permian animals would probably seem slow and stupid to us. (Most Permian creatures are sprawlers, so though they may be fairly fast over short distances, they could easily be run down and killed with a hefty rock. The same would allow me to escape predators, even if any of them recognized me as food -- humans often look scarily large to other animals because of our height. Permian animal meat should still be edible -- humans can eat reptiles as well as mammals, so there's no reason to think Permian reptiles or protomammals would be inedible.
Hmm, assuming my assumptions about diseases not affecting humans are correct, then a non-desert location in the Permian might be easier to survive in than almost any modern wilderness...
I think Permian diseases could affect humans - bacteria and viruses evolve to suit their host by making sure they don't kill the host too soon and they can effectively get passed on to new hosts. Permian diseases would probably not be able to pass from human to human (but you're alone, so that's irrelevant), but I expect they could still kill you - probably quite quickly. Compare this with Avian flu - a human can catch it and it can be pretty nasty, but it can't pass from human to human. Birds are probably about as different from us genetically as Permian animals, so it's a good comparison. --Tango (talk) 21:55, 19 February 2009 (UTC)[reply]
Given the high carbon dioxide et al, wouldn't you become a sprawler too? And would that affect fire for cooking that thing you killed with a rock? Julia Rossi (talk) 22:34, 19 February 2009 (UTC)[reply]
I'm not sure about you, but the fire would be fine. Fire just depends on oxygen levels, which I think were actually very slightly higher then (making it easier to light, I guess). --Tango (talk) 23:30, 19 February 2009 (UTC)[reply]
I'm pretty sure there were no grasses or flowers in the Permian: if I remember correctly, flowers didn't exist until the late Jurassic and grasses not until the Cenzoic. Maybe eat some ginkgo, perhaps? You might have to watch out for the large reptile/proto-mammals. ~AH1(TCU)23:34, 19 February 2009 (UTC)[reply]
This is exactly the kind of thing that makes me doubtful of your survival chances. You can't survive by only eating meat. (See, for example, Rabbit starvation). There are no grasses - and hence no grains and there are no flowers. So most - if not all - of the plant-based foods we're used to finding won't be there at all. Most of the plants are things like ferns which don't make up a part of our normal diet. Without plants, you won't get enough fiber and roughage - and that's going to be pretty bad on a timescale of months to a year. Lack of vitamin C in your diet would also make you likely to suffer from Scurvy...you can find vitamin C in oysters - but who knows what Permian shellfish have? I think it would be pretty tough to find enough of the right kinds of foods to keep you alive. Everything you'd experiment with is a potential poisonous plant. There are all sorts of complicated field guides you can get for modern day earth to tell you what's safe and what isn't...but in the Permian? All bets are off. The only things we really know about plants from that time are fossils - and you can't tell whether something is poisonous from a fossil! SteveBaker (talk) 01:48, 20 February 2009 (UTC)[reply]
A very big CD! You would need to narrow down which articles are likely to be useful if you want to get it down to a reasonable size. And how do you intend to power your laptop? I think printing the articles off would be better. --Tango (talk) 10:38, 20 February 2009 (UTC)[reply]
You can actually buy (or download for free and burn) Wikipedia on CD-ROM. The trouble is that you can't fit it all on one CD. There are several Wikipedia projects who are trying to pick a suitable subset for CD and/or DVD. I did download the CD version a year or two ago and it's very sad. Almost all of the cross-links are gone - and only the most significant articles are there. Also all of the photos are stored only at their thumbnail size. SteveBaker (talk) 04:34, 21 February 2009 (UTC)[reply]
Maybe an extra person could bring five extra things for the list. You'd have to know your ferns and maybe have a video chip implant in your head because when you get back and tell us, we'll need proof. :) Julia Rossi (talk) 22:25, 20 February 2009 (UTC)[reply]
Object 1:Swiss Army knife (largest and most complete version). 2:Firemaking kit. 3:Sleeping bag. 4:tent. 5:Messkit(small pot, skillet, cup, fork & spoon). In addition, you'd better know how to hunt and fish with equipment you can make from sticks and flint tools you make yourself, and you'd better know how to make clothes etc from hides and fiber. If a 6th object is possible, bring the Rae Dawn Chong character from "Quest for Fire (film)." Or just substitute her for items 1 through 5. Edison (talk) 05:30, 21 February 2009 (UTC)[reply]
I have a very large and complete penknife, it's mostly screwdrivers. A screwdriver is completely useless when you are a few hundred million years before the invention of the screw. I really think a simple, good quality knife would be better. --Tango (talk) 13:53, 21 February 2009 (UTC)[reply]
A Swiss-type knife might have tools other than screwdrivers, wire strippers and other items useless in the ancient past. I have seen other brands with a knife and fork. I have seen them with an excellent saw, extremely helpful in woodworking. They also may have an awl/needle, highly useful for sewing sinews through hides. The scissors would also be useful for making garments or shoes out of hides The tweezers are helpful for getting splinters out, and don't discount the toothpick as a comfort item. Extra knife blades are useful when you break one. If you can afford to time-travel, you can afford to create a custom Swissknife with sewing awl, 2 knife blades, saw, pliers, drill, tweezers, compass, and solar charged LED light. Count the assembly as one item., Whatever is not explicitly forbidden by the rules is permissible. Edison (talk) 01:37, 22 February 2009 (UTC)[reply]
If you're allowed a custom made Swiss Army knife, you're allowed the survival tin I mentioned above. My survival tin contains a spare knife, a sewing kit, a wire saw, a compass, a candle, some water proof matches, flint and striker, water purification tablets (that expired Sept 05... I should replace those!), a whistle (not particularly useful when on your own, I guess), fishing gear, some snare wire, safety pins and a mini survival guide. Admittedly, no tweezers, you'll have to dig the splinter out with one of the safety pins. --Tango (talk) 02:05, 22 February 2009 (UTC)[reply]
Let's assume you don't end up in the desert. If you end up in an area with cycads you can leech and process those make flour. Unfortunately some of the animals you hunt may have eaten the toxins and have become unsafe for human consumption. Since cyanobacteria are generally considered to be very early representatives of the group it would be too much to hope that the Cycads did not yet contain the toxin back then. Cycads would also be useful because their palm fronds can be made in to lots of things. {{Ginko]] nuts can be eaten. To the poster who'd like to produce hides and use sticks. Very few if any plants in that period produced usable wood AFAIK. Most were soft, gnarled and stringy. Producing hides from reptiles is a difficult process that requires specialized vats and chemicals. One of the most common sources for tanning materials in earlier times were oaks and similar trees. They weren't available in the era our traveler is headed for. So you'd have to make do with processing plant fibers. Flint might also not yet be available in a usable form. A saw wouldn't do a good job cutting stringy plants. I'd take a machete, a whetstone, a first aid foil blanket [20] (We don't have a page??), a cooking pot, a water desalination device and a halberd, pike (weapon) or lance. You'd have to learn how to make fire using friction and make a hammock in a hurry, otherwise you might want to take those. Douse yourself in tons of bug repellent before you go and hope it'll work on cockroaches. Be very sure you have the means to return to the present should the need arise. If one of the local pathogens or critters turns out to be lethal there's not that much you can do about it. The good news is that they found that the human genome contains sections that used to belong to bacteria once. Bon voyage. 76.97.245.5 (talk) 07:48, 22 February 2009 (UTC)[reply]
Assuming you could find a salt water source, this device might provide a source of salt (could be very useful). Not sure if such devices actually produce the salt in a useful form, though. --Scray (talk) 00:35, 23 February 2009 (UTC)[reply]
You could just drink the salt water, though. (You would generally want to dilute it with fresh water first, although I'm not sure what the salinity of Permian oceans was.) --Tango (talk) 00:44, 23 February 2009 (UTC)[reply]
What for? And if you just want the salt you can get it the same way people have got salt for millennia - just collect some sea water and let it evaporate. --Tango (talk) 12:04, 23 February 2009 (UTC)[reply]
IMHO, you cannot beat The Feynman Lectures on Physics. There are three large books - he teaches at a basic level but he doesn't start with boring topics like most physics books do. There aren't many basic books written by Nobel prize winners - this is a good one! SteveBaker (talk) 18:43, 19 February 2009 (UTC)[reply]
I've found that the conceptual richness of Feynman's basic physics takes precedence over fundamental, basic quantitative skills. As such, they are a great review for a well-versed expert in the field; and a great conceptual overview for somebody who is just dabbling; but they're a terrible way to start learning with intent to solve quantitative physics problems. Nimur (talk) 18:47, 19 February 2009 (UTC)[reply]
I agree to a point. I don't think I'd necessarily recommend Feynman to someone who wanted to learn equations and such - but to our OP who wants an easy-going 'concept' book - these get my vote. SteveBaker (talk) 01:10, 20 February 2009 (UTC)[reply]
will ... evry one has the right to learn , knowledge is as important as food , and you can't blame the theif for stealing food ,can you ,knowledge is right for evry one even for the poor , i can't afford it ... so what ...??
People who write and publish books for a living have the right to feed their families and put roofs over their children's head just as much as you do. Stealing the works of their effort is as much crime against them as is stealing any other object. Spend the money, buy the book. this link shows copies availible used for as little as $34.00. Likewise, you are likely within reasonable distance of a lending library where you can get books for free. If your local library does not carry the book, you can probably get it via interlibrary loan. --Jayron32.talk.contribs02:28, 20 February 2009 (UTC)[reply]
It's ILLEGAL - period. If you can't afford to buy a copy - you can check out a copy for free from your local public library. There is no justification for infringing copyrights. SteveBaker (talk) 02:29, 20 February 2009 (UTC)[reply]
Actually the 'period' shouldn't be there. There are countries without criminal penalties for copyright violations particularly when we are talking about for personal use. (For example, according to Spanish copyright law it is only a crime if there is an intent to make profit and if I understand [21] it's the same in Israel.) The copyright holder could usually still sue for infringement but saying something is illegal usually implies it is in violation of criminal law. Also there are countries which don't recognise American copyright (and for which the US doesn't recognise their copyright), therefore the book would likely not be copyrighted in those countries so you couldn't even sue for infringement. The OP's IP looks up to Jordan and Jordan is party to WIPO and according to Jordanian copyright law it is illegal in Jordan and it sounds like this is even in personal use case, but that doesn't change the fact it's misleading to claim it's always illegal. As for the comments on libraries, do either of you know what Jordanian libraries are like? While there are public libraries in Jordan [22], i have no idea what they're like, I'm doubtful either of you do either. Nor is it likely we know that there is one where the OP lives... (Coming from Malaysia I know that libraries are not always that ubiqutious nor that well stocked in developing countries.) Note that even if public libraries exist, they may not be free so unless the OP is already a member, buying a copy of the book if that's all he/she wants may or may not be cheaper. IMHO there's a very good chance even if they exist, they don't carry the book. Getting it via interloan may or may not be possible but could take a long while and add to the cost. I'm not of course going to help the OP get a copyright violating copy of the book but this doesn't mean it's fair to the OP to presume to know what the OP can or cannot do without considering his/her local circumstances or to provide misleading information like claiming it's illegal period when in reality the situation is often far more complicated then that. Nil Einne (talk) 10:45, 20 February 2009 (UTC)[reply]
That's a strange definition of "illegal". Civil law is still law. It may not be a criminal offence, but it's still illegal if it is against civil law. --Tango (talk) 12:28, 20 February 2009 (UTC)[reply]
If the OP wants freefree information, then Physics is the place to start. As much as I am a zealot of Free Information, I recommended a book which is copyrighted and expensive (neither free nor free) because the quality of the content is so very high. I'm sure that is the same reason Steve Baker recommended the Feynman lectures. If the purveyor can not afford expensive resources, and does not want to be bound by legal restrictions on copyrighted materials (philosophical arguments notwithstanding), there is fortunately an excellent alternative right here. Nimur (talk) 23:18, 20 February 2009 (UTC)[reply]
It's perfectly legal in Colombia where I used to live. They have a "for educational purposes" fair use clause. Don't be so US centric. —Preceding unsigned comment added by 144.82.194.103 (talk • contribs) 22:51, 23 February 2009
That's not a U.S.-centric view, it's international copyright law, which according to this is respected by the Colombian government. If that's the case, then taking entire copyrighted books without paying for them is no more legal in Colombia than it is in the U.S. Do you have a reliable source to the contrary? --Scray (talk) 05:28, 24 February 2009 (UTC)[reply]
Linear Variable Differential Transformer
In LVDT when we draw the graph between displacement & output voltage the graph does not start with zero & the graph is not completly linear . Why?
Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. Nimur (talk) 18:43, 19 February 2009 (UTC)[reply]
While we don't normally answer homework questions, we can point you in the right direction. The three places where you are MOST likely to find the answer, in order, are:
In your lecture notes that you wrote in your notebook the day that your teacher told you the answer to this question.
In your textbook that your teacher gave you at the beginning of class, probably in the chapter which closely matches the lecture note that you have.
Turn off the spam filters on your email account and you'll find PLENTY of people who will be happy to offer help. Make sure you reply to thank them all. :-) SteveBaker (talk) 01:03, 20 February 2009 (UTC)[reply]
Is blue supergiant a main sequence star? Does it eventually swells up and become a orange hypergiant/supergiant? Does orange dwarf swells up and become a orange giant, actually what's a blue dwarf?--216.100.95.90 (talk) 21:03, 19 February 2009 (UTC)[reply]
See blue supergiant and supergiant - they aren't main sequence stars. I've neverhttp://en.wikipedia.org/w/index.php?title=Wikipedia:Reference_desk/Science&action=edit§ion=59 heard of "orange" stars, do you mean red? Stars can change between red and blue supergiants, sometimes multiple times - they usually die in a supernova eventually. Red dwarfs are theorised to just slowly collapse into white dwarfs, although they live so long that hasn't happened yet so we can't really tell. I've never heard of a blue dwarf. --Tango (talk) 21:21, 19 February 2009 (UTC)[reply]
Yes, I've heard of orange stars, but not "orange" stars - I was referring to "orange" as a name, rather than just an adjective, by putting quotes around it. With hindsight, this was not at all clear! --Tango (talk) 21:49, 19 February 2009 (UTC)[reply]
Does shaking bus indicate particular type of drive train?
Recently I was on an older charter bus whose rear end shaked up and down so violently that several of my friends in the last two rows were unable to type text messages on their cellphones. The front end did not shake. I was told the reason for this was that the bus was designed for an evenly distributed weight of passengers, but that most of the passengers were in the front half. Does this indicate that the bus had a particular type of drive train, and would a different type of drive train have eliminated the problem? NeonMerlin22:00, 19 February 2009 (UTC)[reply]
Only when moving. I don't think the speed made much difference (although the speed changed so rarely that I'd have to have had measurement instruments recording to know for sure). NeonMerlin04:01, 20 February 2009 (UTC)[reply]
All I can think of that matches the description is a rear-wheel drive bus with front engine which has most of the weight on the front axle. If most of the passengers also rode up front, the rear wheels might tend to bounce off the ground going over bumps. This could happen with front-wheel drive, too, but wouldn't be as noticeable because you wouldn't have the drive wheels alternating between engaging and spinning. If we ignore what you were told, then one or more unbalanced rear wheels could also be the cause, or perhaps the rear suspension is shot. StuRat (talk) 04:32, 20 February 2009 (UTC)[reply]
Yep - that would be my diagnosis too - something amiss with the rear shock absorbers would make it do that. The shocks should damp out low frequency vibrations and stop them from building up like that. I rather doubt the weight of the passengers counts for much though. A standard US schoolbus weighs about 13 metric tonnes...about the same as 180 'typical' adults. SteveBaker (talk) 02:45, 21 February 2009 (UTC)[reply]
February 20
Bouyancy
On "How Things Work" on the Discovery channel, it was just stated that everything floats on molten lead except uranium. I didn't think that sounded right so I looked up a few heavy metals right quick. Plutonium, gold, and uranium all have higher densities than lead, so how could that float on it? TIA, Ζρς ι'β'¡hábleme!02:10, 20 February 2009 (UTC)[reply]
They all have higher densities than solid lead; molten lead will definately have a different density, solid gold may possibly float upon it. It may have also been contextual; it could be possible that everything in uranium ore except the uranium floats, so molten lead may be useful as a sepration techinique for extracting uranium from its ore. Without the exact context of the statement, it is hard to tell what they were talking about. --Jayron32.talk.contribs02:19, 20 February 2009 (UTC)[reply]
I agree - it seems pretty unlikely. Molten lead is around 10g/cm3 - Gold and Uranium are both up at 19g/cm3...it doesn't make sense. Is it possible that in the context of that show - they were saying something like "Nothing in this mixture of substances we're talking about right now floats on molten lead except for the uranium that is present in that mixture." ? What was the context of this comment? SteveBaker (talk) 02:25, 20 February 2009 (UTC)[reply]
True, but the actual object that is floating is a combination of steel and air, the average density is less than that of water. --Tango (talk) 19:47, 20 February 2009 (UTC)[reply]
Energy transfere
Using asystem of ( man hanged to aflying object ) , at the moment the man drop him self off ,getting hanged , how many changing in energy type and way will happen , what type of energy stop the man from hitting the floor , the energy trnsfered from and to the man through the rop ... as detailed as possible ... ? —Preceding unsigned comment added by Mjaafreh2008 (talk • contribs) 02:30, 20 February 2009 (UTC)[reply]
Your question is difficult to understand as written, so it is hard to give relevant pointers. If you would like help here, you'll need to word it more clearly. --Scray (talk) 05:42, 20 February 2009 (UTC)[reply]
I agree that your question needs clarification. However, if you are discussing a man hanging from a rope on a flying object, and the energy types involved, then I believe the change in energy will be from gravitational potential to kinetic energy to heat. That said, I can't be sure unless you clarify things a bit better. —Cyclonenim (talk · contribs · email) 09:39, 20 February 2009 (UTC)[reply]
at moment 0.0 ... evry object of this system had its potentioal energy with the value x,y,...etc...............................
at moment 1.0 ... the man through him self changing his altitude making the energy to change from potentioal to kinetic to heat to ... ??? I need a plan describe how this energy will transfer from form to anthor . —Preceding unsigned comment added by 94.249.105.235 (talk) 18:30, 20 February 2009 (UTC)[reply]
While many energy transfers do occur, in this situation it is not straightforward or well-defined. If this is a homework question and you want an energy-transfer scenario, you might consider a simpler case, like releasing an un-tied balloon and letting it blow across a room, or something.
The person will probably behave as a pendulum, so in addition to gravitational potential, there will probably be angular momentum in the swinging body, "storing" and exchanging some linear and rotational kinetic energy and some gravitational potential energy in the swing upstrokes and downstrokes. There will probably be tension on the rope, which may have a spring-constant (albeit a stiff one); so potential energy will be stored in the fibers of the rope; there will likely be deformations (large and small) of the various materials involved, including anatomical injuries. The situation may induce the man to undergo a series of physiological responses, indirectly causing chemical (food) energy to convert to kinetic and heat energy via metabolic processes. (This list is not meant to be complete)... Nimur (talk) 23:27, 20 February 2009 (UTC)[reply]
I don't know about "instantly", I imagine there's a speed of light delay, but that will only be a tiny fraction of a second, which can safely be ignored. Individual electrons do have a mass, and thus an inertia, but it's extremely small. StuRat (talk) 04:22, 20 February 2009 (UTC)[reply]
It is not even remotely true. If you take a course in electronics, you will likely be required to do what everyone hates: calculate the current at time t after a circuit is opened or closed. Current cannot go from, say 10amps to 0amps instantly. It will decrease from 10 to 9 to 8... to 0 over time. The time is very short - about as long as takes for a spark to jump the gap just after the circuit opens or just before the circuit closes. -- kainaw™05:05, 20 February 2009 (UTC)[reply]
So while the mass of the electron does make a (very small) contribution, the key effect is actually inductance. Moving charge induces a magnetic field, which stores energy. When you remove the external voltage source, the magnetic field begins to collapse; in collapsing, it creates a voltage in the same direction as the one that was there before. This is very much like inertia, but it isn't (or at least isn't mostly) due to the mass of the charge carriers. --Trovatore (talk) 05:34, 20 February 2009 (UTC)[reply]
That is correct. I didn't mean to imply that the continuing current was due to inertia. I was simply pointing out that the current stopping instantly was not correct. -- kainaw™05:38, 20 February 2009 (UTC)[reply]
StuRat brought up the electron mass, so I incorporated that into my response. However my response, though trying not to duplicate correct remarks made earlier, was actually to the original poster (that's why I indented only once). --Trovatore (talk) 05:44, 20 February 2009 (UTC)[reply]
When considering voltage rise/fall time at the end of two wires connected to a voltage source, resistance and distributed capacitance must be taken into consideration, as well as inductance and electron mass. (See "RC Time Constant" in Wikepedia.) Distributed capacitance, inductance, and resistance will have only a very slight affect when all the following apply:
§ The voltage is carried by two straight wires (no coiling).
§ The wires have relatively slight resistance.
§ The voltage source has relatively slight internal resistance.
The resistance of the wires and resistance of the voltage source affect the charge time of the distributed capacitance. Discharge time will be much longer than charge time because there is only leakage current (through very high resistance) to discharge the capacitance. – GlowWorm. —Preceding unsigned comment added by 174.130.249.1 (talk) 08:00, 20 February 2009 (UTC)[reply]
One more word about my last post. The capacitance of two short wires is very small. The resistance of the two short wires is also very low. Similarly, the self-inductance of each wire is small. But when talking about the tiny inertia of electrons, every slight influence should be taken into acoount. – GlowWorm. —Preceding unsigned comment added by 98.21.109.186 (talk) 22:15, 20 February 2009 (UTC)[reply]
A Few ?s...
I've got a ? - Why is ozone an important form of oxygen? Oh, and I have another one - How are you able to mantain the nitrogen your body needs? I believe I know the answer to the second question... but I am not sure. Help is appreciated. Thanks! ILY. --69.178.20.243 (talk) 06:41, 20 February 2009 (UTC)[reply]
This is an encyclopedia with articles on many topics. If you type "ozone" into the search box on the left, you can find articles about it. This is not a free homework answers service, but if you tell us what you think, we can help you decide if your answer is reasonable. DMacks (talk) 06:49, 20 February 2009 (UTC)[reply]
Measure the side of the cube of wood. Multiply this number by itself twice. This will give you the volume of the cube. Place the cube on a scale. This will give you the weight of the cube. Weight divided by volume is density. The density of water is 1 gram per cubic centiment (or 1 gram per milliliter, equivalent measurement). Specific gravity is the density of the object divided by the density of water. So take the number you got, and divide it by 1. I don't think you'd need a calculator for that calculation... --Jayron32.talk.contribs12:24, 20 February 2009 (UTC)[reply]
While that is how to determine density with scale and ruler, it has very little to do with Archimedes' principle. The second paragraph you see after following that link should provide what you need, it is very readable. If after reading that you have a specific question, please follow up here and I'm sure we'll be able to help. --Scray (talk) 14:17, 20 February 2009 (UTC)[reply]
(after ec) To the original questioner: If you meant cube and not cuboid, Jayron's instructions should be ok for calculating the specific gravity, but they don't use Archimedes' law. From our article Buoyancy:
For a lighter-than-water object, I suppose "apparent immersed weight" would be a negative value - the force needed to keep the object from floating to the surface. You could use a spring scale that was attached both to the bottom of the container and to the wooden object, and raise the water level until the object was underwater. If you use the readout (with a negative sign) in the formula quoted, I think it should work. --NorwegianBluetalk14:29, 20 February 2009 (UTC)[reply]
The weights of displaced water and the object have to be equal. (Archimedes' principle = "Any object, wholly or partly immersed in a fluid, is buoyed up by a force equal to the weight of the fluid displaced by the object.")
Weight = density * volume.
Given #1, (density of water) * (displaced volume of water) = (density of object) * (total volume of object).
From this, we derive
Displaced volume of water = area (length * width) * submerged height
Total object volume = area (length * width) * total height
Simplifying:
Specific gravity = (density of object) / (density of water)
And therefore specific gravity = submerged height / total height. The area need not be a perfect square, which is why it can be a cuboid rather than a cube. arimareiji (talk) 17:34, 21 February 2009 (UTC)[reply]
Both East London, South Africa (26-10) and San Francisco, USA (23-7) have only a 16°C difference between highest month average high - lowest month average low. Anyone know example of a smaller difference [with a Mediterranean climate]? San Diego is 17°C. (This question has been asked about the USA before, I'd like to know of cities in other countries also.) -- Jeandré, 2009-02-20t14:18z, -- Jeandré, 2009-02-20t16:09z
Yeah, and I found tropical Medellín at 11°C (28-17)[23]. An important part is a Mediterranean (temperate) climate. By that measure East London's 26 is already a bit high. -- Jeandré, 2009-02-20t16:09z
I agree with the smallest temp change occurring in the tropics, and would add that I'd expect it to be on a small island, where the water has a moderating effect on the temp. Honolulu, for example, has a 5°C variation. A small island, closer to the equator, might have even less variation. For example, the Galapagos Islands only have a 3°C variation, although there's no big city there. StuRat (talk) 16:35, 20 February 2009 (UTC)[reply]
Dates Before Christ?
How were dates recorded before the knowledge of Christ's existence?
It would depend on the reigning monarch. I suspect you got more people saying, "In year 15 of King 'X's reign," for isntance; so you had to add backwards to get how many years ago something was. (Which made it confusing if there were regents, etc.)Somebody or his brother (talk) 14:39, 20 February 2009 (UTC)[reply]
If you're talking about not too long before, and in the same area of the world, I'm guessing the system associated with the dominant power was AUC, ab urbe condita, which means "from the time they put salad dressing on the city" :-) --Trovatore (talk) 19:06, 20 February 2009 (UTC)[reply]
Well, for one, the AD system was only invented in 525 CE, and that very likely is not 525 years after the birth (or conception) of Jesus. The salad dressing system was not widely used at that time, either, even in Rome. Romans counted mostly by consuls ("The year mario and kong became consuls"). Other cultures used various local system, often based on local rulers. --Stephan Schulz (talk) 22:08, 20 February 2009 (UTC)[reply]
Why did more colds develop into pneumonia in years past?
My mom was telling me on the phone she's getting over the common cold, and said thankfully, "at least it's just a cold." That got me to thinking about the fact that, in bygone years, it seemed like more colds did develop into pneumonia. She recalled that, too, and also said it was younger people who got it from colds.
As I told her, there were two things I could think of that could be the result: 1. In the early Industrial Revolution until recently, a lot of pollutants got into the lungs that just happened to coincide with a cold to cause it; and, 2. Before central heating, a lot of homes were draftier and damper, so ther places where people could recupterate had lots of mold and such to make things worse. (I read where some castles were chillier inside than the weather outside)
But, we weren't really sure why it was. So, are one or both of my guesses right? Or, is it another reason? Or, is this just a fallacy, and about the same percent of colds as centuries before developed into pneumonia?Somebody or his brother (talk) 14:33, 20 February 2009 (UTC)[reply]
I can think of several possible reasons:
1) Improved diets mean we are less likely to have a compromised immune system which might provide an opportunity for pneumonia to develop. In particular, nutritional deficiencies are less likely. (While modern diets can lead to obesity, diabetes, high blood pressure, heart disease, etc., they do at least typically provide the necessary minimum of all nutrients.)
2) People are now more able to take off work when sick to avoid worsening the problem.
3) Less time is spent outside, exposed to the elements, now. This is due mainly to most people working indoors and to enclosed transportation, like cars.
4) People work shorter hours now, so have more time to tend to themselves and less exposure to stress factors.
Aggressive recognition and treatment of the common cold may also contribute to the fact that pnemonia is on the decline. Although, pnemonia still impacts people with comprimised immune systems (either by an autoimmune disease or some other sort of illness), the elderly and the very young. Livewireo (talk) 20:50, 20 February 2009 (UTC)[reply]
Pneumonia is also a secondary infection, like a sinus infection, whereby the symptoms of the cold, such as mucus production, may provide a medium for the infection. When you have a cold, you make lots of mucus (snot). Mucus is an excellent medium for secondary bacterial infections. So modern medicines which decrease mucus accumulation, such as Guaifenesin, may help decrease the onset of these sorts of secondary infections. --Jayron32.talk.contribs21:07, 20 February 2009 (UTC)[reply]
"Mucus is an excellent medium for secondary bacterial infections." Really? Have a look at the second sentence of Mucus. Or, this article from Pubmed. There are many antibacterial properties of mucus - and that makes perfect sense. --Scray (talk) 00:57, 21 February 2009 (UTC)[reply]
Secondary infections set in after a virus kills the cells which protectively line the respiratory tract. When a protective lining of mucus is no longer there to constantly wash bacteria out of the respiratory tract, up to the mouth (to be spat out or swallowed into the acid bath of the stomach), it makes it much easier for the nasty little buggers to set up shop. Think of the film clips you've seen where fire hoses are used on demonstrators - only this time the "good guys" are your body's defenses, the ones wielding the fire hoses. In its normal role, mucus is good. arimareiji (talk) 17:58, 21 February 2009 (UTC)[reply]
To the original poster - look up the 1918 flu pandemic, which killed tens (possibly hundreds) of millions with a horribly-virulent form of pneumonia. Then if you really want to be disturbed, look up the WHO's reports on the emergence of H5N1, a close relative of the H1N1 strain that caused the 1918 pandemic. There's a reason they keep slaughtering millions of birds in SE Asia - it's because we've made very little progress against viruses from 1918 to 2009. Bacteria yes, viruses no. arimareiji (talk) 18:10, 21 February 2009 (UTC)[reply]
(If anything, we've become much less conscious of basic health precautions like washing your hands and covering your mouth and nose when you sneeze. Contrast this with many parts of Asia, where it's considered to be somewhere between rude and disgusting to be sick with a respiratory illness and refuse to wear a mask.) arimareiji (talk) 18:16, 21 February 2009 (UTC)[reply]
Lancet reputation
How much of an effect did the surveys of Iraq War casualties have on the reputation of the Lancet? A lot of what I read about the peer review process of the 2004 and 2006 reports makes me wonder about the objectivity of the journal. Is there much concern amongst the scientific community about the Lancet's misjudgment of publishing those papers? —Preceding unsigned comment added by ExitRight (talk • contribs) 14:37, 20 February 2009 (UTC)[reply]
As far as I can tell, the scientific community regards those studies as valid and as good as can be expected under such challenging circumstances. I'm not aware of any major problems that have been reported. As such, it had no negative influence on the Lancet's reputation, at least not among scientists. --Stephan Schulz (talk) 18:32, 20 February 2009 (UTC)[reply]
Really ? Our article seems to say there were all sorts of problems with it, and that it overestimated the numbers by around 6 times compared with every other major survey. The most obvious problem I saw was their claim that 90% of those asked were able to produce death certificates. That would mean 550,000 death certificates, when there were actually only 50,000. That's what I call "junk science". Publishing something like that certainly does diminish respect for any scientific journal. StuRat (talk) 18:41, 20 February 2009 (UTC)[reply]
You should look at the quality of the sources, and about what is claimed by the different surveys. The Lancet studies count excess dead, i.e. they include all causes, from malnutrition to cluster bombs. The IBC, for example, counts only violent civilian death reported in the English language press. A factor of 6 between violent civilian deaths reported in the English language press and all excess deaths seems entirely plausible to me. Moreover, for the first study, IBC and Lancet are entirely compatible, and for the second the factor is only about 4, not 6, if you take the 95% confidence interval into account. --Stephan Schulz (talk) 18:58, 20 February 2009 (UTC)[reply]
I don't give much about the opinion of people who "went batshit insane". I have found only fairly mild criticism of the study in the academic literature, and a lot of support of the core findings and the methodology. Sure, the right-wing blogosphere went berzerk. But that is entirely irrelevant to the original question. The Lancet's current impact factor is 28.600. In 2004 it was 21.713. So it seems that it's reputation, at least among academics, has not suffered. --Stephan Schulz (talk) 00:31, 21 February 2009 (UTC)[reply]
I largely agree with Stephen Schulz and would point out two things. One, the authors have been willing to discussion and engage in rational debate about resonable issues that were raised about the study, something we would expect from good scientists and this is reflected in the wikipedia article. I would suggest you read it if you haven't already since it's a decent article. Two, one of the most interesting things (to me) is the timing issue raised by numerous sources. Rather then re-invent the wheel, I'll just mention again that our article covers this well. A final comment quoting from the article which is apt in this discussion "The Chronicle of Higher Education also wrote an article discussing the differences in the survey's reception in the popular press over how it was received in the scientific community". P.S. A perhaps more relevant study on Iraq with regards to recent events is the one which raised what seems to me are valid questions on whether the surge really worked [24][25] published in Environment and Planning and mentioned in our Iraq War troop surge of 2007. I didn't see much criticism of this perhaps because by that time everyone had forgotten about Iraq since the world economy had taken centre, heck left & right, top & bottom, stage. Nil Einne (talk) 12:45, 22 February 2009 (UTC)[reply]
The Lancet has been known to publish somewhat controversial topics, and sometimes those with poor evidence. However, it's still the World's leading medical journal and the benefits from its existence far outway some of the bad efforts they've made. That's most likely why it's reputation hasn't suffered that badly. —Cyclonenim (talk · contribs · email) 10:15, 21 February 2009 (UTC)[reply]
I know that human knowledge or understanding of concepts has finite limits in many respects - there are limits to how fast we can think or how many different things we can learn. What I'd like to know - is there any reason to believe that there are TYPES of things that humans simply don't have the capacity to understand? I'm not talking about things that are literally unknowable, I'm talking about things that, say, a superior alien intelligence could understand, that we humans could never hope to? If so, what types of things might fit this category? ike9898 (talk) 19:09, 20 February 2009 (UTC)[reply]
Oooh! A chance to use my favourite quote: "My own suspicion is that the universe is not only queerer than we suppose, but queerer than we can suppose." J B S Haldane (otherwise known as Haldane's Law). It's a bit like Rumsfeld's "unknown unknowns" - I suspect your question is literally unanswerable. --88.108.231.179 (talk) 20:24, 20 February 2009 (UTC)[reply]
At an individual level, there are things that I cannot understand, such as string theory, but it's not hard for me to understand that it exists and in the broadest, simplest sense, what it is about. I'm thinking of something like this, replacing the individual with the human race. ike9898 (talk) 20:30, 20 February 2009 (UTC)[reply]
We've used computers to analyse all possible chess endings with certain combinations of pieces like 2 knights vs knight and bishop, but it would be impossible for me to remember all possible positions at the sme time even though given enough time I could enumerate them. Is this, the case of limited memory, an example such as is desired? RJFJR (talk) 20:39, 20 February 2009 (UTC)[reply]
No, that's not really what I'm thinking of. A human could probably understand any individual chess ending, so this is a TYPE of thing humans can understand. I'm looking for a type of thing that we can't understand. Also, if we can build tools (computers) to help us analyze something, as far as I'm concerned, that counts as being understood by humans. ike9898 (talk) 20:47, 20 February 2009 (UTC)[reply]
For the record... unknown unknowns are common ways of thinking about military contracting—the concept existed a long time before Rummy and it's too bad it has gotten associated with him in such a silly way, because it is actually quite sensible (as was his original exposition, which was quite clear). --98.217.14.211 (talk) 02:15, 21 February 2009 (UTC)[reply]
But there would be things to complex to understand, say with more than 8 things all happening at once. But once you factor in computers you are looking at the limits to computability. Once you have a universal computer it is basically equivalent to any other computer, and can compute the same things. Graeme Bartlett (talk) 21:32, 20 February 2009 (UTC)[reply]
I'm sure the answer is 'yes'. We had a long thread the other day about whether there are 'new' colors out there that we haven't seen yet. We know that humans see (basically) red, green and blue and mixtures of those 'primary' colors. But we can't tell the difference between 'yellow' and 'red+green'. We can't even concieve of a color that we haven't seen yet. But there are some animals out there (I believe that goldfish and freshwater shrimp are two of them) that see in as many as 12 'primary' colors. We can't understand what the world would look like to them. However, there are at least two people in the world who we know can see four 'primary' colors (they are tetrachromats). They can understand something that the rest of the world can't. That's not a limitation of the brain so much as a total failure of imagination. SteveBaker (talk) 21:43, 20 February 2009 (UTC)[reply]
On further thought - the human brain is a 'turing complete' computer. There is a theory called "The Church–Turing thesis" that says that all turing-complete computational systems are equivalent. That means that (in principle) any calculation that your brain can do could (in principle - if you had enough time and memory) be done by any computer. What I think that means is that our brains are CAPABLE of understanding anything - the fact that we can't imagine what it would be to see in four primary colors is not a failure of the computational systems in our skulls - it's a failure of imagination. The two ladies who see four primary colors have no problem 'imagining' four primaries - yet we can't even begin to do that. However, their brains are (presumably) pretty much the same as ours - and they are certainly 'equivalent' per Church-Turing. So a failure to understand may well be simply a failure to imagine. That's a very deep thought. SteveBaker (talk) 21:49, 20 February 2009 (UTC)[reply]
And another one - imagining a 4 dimensional world. We can do the math and we can predict what happens - but we really can't "understand" it. SteveBaker (talk) 21:53, 20 February 2009 (UTC)[reply]
That is interesting, but is there any reason to believe that some sort of intelligence superior to ours could understand it any better? Or is it hard for any real intelligence to understand because none will ever experience it? ike9898 (talk) 22:10, 20 February 2009 (UTC)[reply]
Isn't time the fourth dimension? That way 4 dimensional would be doable, but some of the other higher dimensions that they think up to make things fit in the upper reaches of physics I'd agree are really like a dust-mite trying to grasp cosmic background radiation. Imagining an alien who could handle that kind of thing is equally out there, though. I wonder if we'll be able to get a handle on dark matter once we have a bit more data. 76.97.245.5 (talk) 22:09, 20 February 2009 (UTC)[reply]
I guess it depends on your definition of "understand". I understand n-dimensional space on an abstract level. Some people even claim to be able to visualise higher dimensional spaces (some of them are even people I would be tempted to believe - one of them told me the trick is to do it in the pitch black so there is no 3D Euclidean space to confused you). A Turing complete computer can run any program that can be run on a Turing machine, that doesn't mean if can run any program. Oh, and I'm not sure about your use of the word "primary" - I think the word is too vague to be useful without clarification, so probably best avoided entirely. --Tango (talk) 22:54, 20 February 2009 (UTC)[reply]
Forgetting for a moment that some people want to call time "the 4th dimension" (which never makes any sense to me) - let's talk about understanding 4 spatial dimensions plus one of time. I too have heard some people claim to be able to visualise 4 dimensions - but I'm not convinced. The idea of tying a knot in a 3D volume much as we can tie a knot in a 1D piece of string - really hurts my head...I really doubt anyone can truly visualise that kind of thing...and if they can, I'll just demand that they do it in 14 dimensions. There is a limit. But certainly there is no problem in doing math in more dimensions. I work in computer graphics - and I frequently have cause to do tests to see if a quadrilateral is 'planar' in 14-space. I can do the math - but I can't even begin to visualise it. As for turing machines - you REALLY need to read what Church-Turing thesis says. It's talking about computable functions...and there is zero evidence that the brain does anything more or less than that. There is little doubt that with a big enough & fast enough computer, we could accurately simulate a human brain. I used the word 'primary' to avoid getting mired up in the whole human visual system question all over again - basically we perceive color as three more or less independent variables - the 'color space' is three dimensional. Terachromats have a 4D color space - and the good old freshwater shrimp has a 12D color space. We can no more imagine those 'extra' colors than we can imagine two distinct kinds of yellow (as the tetrachromat ladies do) or 4D or 12D space. SteveBaker (talk) 02:30, 21 February 2009 (UTC)[reply]
Wandering further offtopic, thinking of (or indeed, calling) time "the 4th dimension" allows you to visualise events as existing in 4D space-time. Which is relatively useful. I can half do it, the half coming from not all of the 'visualisation' being strictly visual. And then, of course, you can abstract that mathematically for certain areas of physics. (Have you never had an astrophysics jag? I'd recommend it as good fun) 79.66.56.21 (talk) 02:19, 23 February 2009 (UTC)[reply]
I'm certainly not claiming that. Quite the opposite. There is no way a cat could do what it does without a turing-complete brain. Hence church-turing applies. However, church-turing contains the rider that the two computational units are only equivalent providing there is sufficient time and memory to perform the same calculations. Clearly cat's brains don't have as much storage space as human brains do. SteveBaker (talk) 02:30, 21 February 2009 (UTC)[reply]
We might have hit the wall already. How would we know? In our quest to understand the universe we've gone from Newton's simple laws to E=mc2 to the gawdawful mess we have now that I don't believe even its proponents understand. What good is an answer nobody can read? We seem to have come unraveled, and the beauty of simplicity has given way to myopic intricacy. That's not to say that the answer isn't intricate, but it's always been a bad sign before. It could be that the true nature of reality is beyond our ken. --Milkbreath (talk) 22:25, 20 February 2009 (UTC)[reply]
Yes - it's kinda sad. The Victorians were so happy in their 'clockwork universe' where everything could be known and predicted with equations that had about four terms in them. Sadly, nature is as nature is - and if it really is complicated, random and chaotic - there isn't much we can do about that. SteveBaker (talk) 02:30, 21 February 2009 (UTC)[reply]
I guess I just think it's strange - For every other type of intelligent creature we know about, there are clearly things they can understand and things they literally can't (ever, no matter how hard they try or how much training they are given). A bird can understand many things, I think, but I don't a bird could ever understand The effects of Hollywood movies on the Soviet stereotype of Americans.
I usually don't think that humans are particularly "special", that our differences from animals of differences of degrees. But that would imply that we have limits on what we can understand, just like a bird does. ike9898 (talk) 22:57, 20 February 2009 (UTC)[reply]
Clarifying using another animal example - - A cat can watch people riding bicycles and be confused about what is going on; maybe he can get the gist of it, but he'll never understand why people shift gears. So I think the cat can look at something like this and be aware that he doesn't understand what is going on. I think it is possible for a brain to be aware of things it will never, ever be able to understand. ike9898 (talk) 23:05, 20 February 2009 (UTC)[reply]
How many human cyclists understand why they change gears? I think it is dangerous to generalise across an entire species. --Tango (talk) 23:12, 20 February 2009 (UTC)[reply]
I'm not talking really about any individual. It's clear that a smart human brain can comprehend gearing if it is taught well; a smart cat brain probably cannot (maybe they can, if so, replace cat with flea). ike9898 (talk) 03:21, 21 February 2009 (UTC)[reply]
Take a look at Jean Piaget's stages of development. He theorizes that children of certain ages cannot understand certain things; for example, young children cannot understand where an object goes when you put it behind your back, until they grow into the next 'stage' and gain the ability to realize that it hasn't just disappeared. Now imagine that all human beings are like children 'stuck' at a certain stage, unable to understand, for example, 5 dimensions. If an alien was the equivalent of an adult in this scenario, it would be able to understand this concept and we wouldn't. Seems very possible to me. Maybe there's a stage that, from an evolutionary perspective, we haven't reached yet. -Pete5x5 (talk) 06:57, 21 February 2009 (UTC)[reply]
I imagine that even now a group of adolescent male lions are lounging under a tree pondering "could there exist a wildebeest so tough, even our inestimable teeth could not bite it?". Silly lions! Your teeth evolved until they were sharp enough, and there's no reason to think that they are the ultimate in teeth when that was evolutionarily unnecessary. --Sean23:21, 21 February 2009 (UTC)[reply]
economy crises
I was listening to the news trying to understand what is happening , what is the source of this crises , what is the cause
how could it infect the whole wide world .
economy is based on trading , material vs material ... oil for cars ,,, cash is just a way to easy thing thats all
so .. as we know ... oil is still there ... factories still have the abillity to produce ... farms still producing food
Our article on the Global financial crisis of 2008–2009 is also very comprehensive. What it boils down to is that the global econmoic market is not as simple as you think. We don't just trade Good A for Good B or Good C for Service Z. There are a great many of factors that impact economic systems and the failure of one or two (namely the bankruptcy of a number of huge American banks and other financial services thanks to subprime lending) send ripples through nearly every single market. Livewireo (talk) 21:06, 20 February 2009 (UTC)[reply]
Following EC: Agreed, that PBS report is good. OP your statements are only correct if you'd assume that purchase decisions are logical. They aren't. Most of the stuff we buy, we buy on a whim and based on our impression of it's worth. You don't really say this car is worth 10,000 gallons of milk. You say it's comfortable. You may say it's fuel efficient. (Compared to taking the bus, really?) But mostly you'll buy it because that's the one you want. If you think there might be a chance that you'll need those gallons or milk more urgently than a Hummer (or any other car) you'll keep driving your old clunker for another few years longer. So the Hummer factory can still produce Hummers, but no one wants them. The Mc Mansions that got built in the housing bubble are still there, but people find they'd rather not get that expensive a house (even the ones who could afford to.) They stand empty, fall into disrepair and the houses nearby all of a sudden also lose value. That is because the neighborhood has changed from "upscale" to "undesirable". So if you go to your bank for that second mortgage the (newly prudent) banker will look at the current market value of your house and tell you it's only worth half as much as it was before half the street was under foreclosure. To that you'll have to add some odd market things like insurance and pensions. They basically rely on the fact that the next generation will earn/produce/pay-in as much or more than the current employees. On top of that you get "gold rush" mentality investment cycles (stock market run, third world market exploitation, .com bubble, technology bubble, mortgage backed securities, etc.) as mentioned in the podcast and you no longer wonder why the economy fails. You rather wonder how it works as well for as long as it does between downturns. 76.97.245.5 (talk) 21:41, 20 February 2009 (UTC)[reply]
Instead of thinking of everything as going down, think of it as correcting itself. Scroll to the bottom of this BBC News article and read upwards, http://news.bbc.co.uk/1/hi/business/7096845.stm. The 12th March 2007 article about New Century Financial has a good quote:
Sub-prime lenders provide money to clients with a poor credit history, charging higher rates of interest because of the greater risks involved. New Century has been hit by a number of problems, including an increase in default rates in the sub-prime sector.
Some people may be too young to remember Savings and loan crisis. It's not as though the current mess is something utterly new and unheard of. BTW. Lots of effects are getting swept under the subprime lending rug. Because the economy is in the pits the oil price has conveniently dropped off the radar. But some of the idustries' troubles are probably to blame on 2000s energy crisis. That was so uttlery unanticipated because these never happened and were long forgotten: 1973 oil crisis1979 energy crisis -76.97.245.5 (talk) 01:07, 21 February 2009 (UTC)[reply]
Would an organic solvent like hexane be good for cleaning silicone oil off of something? I don't know anything more about the oil (it is a standard for a viscometer). ike9898 (talk) 21:13, 20 February 2009 (UTC)[reply]
Wouldn't you know what our OP is trying to clean the oil from first? If DMSO dissolves nearly everything - then whatever is covered in oil may also dissolve! SteveBaker (talk) 21:36, 20 February 2009 (UTC)[reply]
Picky picky picky. Yeah, if the silicone oil is adhered to some sort of rubber tubing or plastic, you'll end up with a sticky goopy mess if you use DMSO. If the oil is on glass or metal, you're probably OK. That's part of the problem with things like plastic and rubber; anything that would clean them would also do a pretty good job of dissolveing them... --Jayron32.talk.contribs21:41, 20 February 2009 (UTC)[reply]
Whoah, whoah, whoah…using DMSO right out of the gate is very much akin to using a tactical nuclear device to get rid of a moderately large ant hill in your lawn. Strong white vinegar (i.e., ~18% to 20% acetic acid by volume), perhaps with a small amount of detergent added, will usually do a fine job of cutting the silicone oil. Exact cleaning and after-rinse technique will depend on the substrate from which the oil is to be removed. —ScheinwerfermannT·C21:49, 20 February 2009 (UTC)[reply]
OP here. The surface to be cleaned is metal, possibly stainless steel. Although I can take the piece off to clean it and move it to a sink or fume hood, I'd rather clean it in place - rinse it with something that will thin the oil and not be super toxic (for my purposes, something like hexane is acceptable to use in this situation). ike9898 (talk) 22:02, 20 February 2009 (UTC)[reply]
Acetone and hexane would be my first tries. Methylene chloride might work similar/better/worse but is more toxic. Which of those common solvents is "best" depends on the nature of the oil..."silicone oil" comes in many flavors. Any of those three would be hella-preferable to DMSO, since they're volatile whereas with DMSO...then you've got the whole instrument covered in DMSO. DMacks (talk) 22:16, 20 February 2009 (UTC)[reply]
This page seems to indicate that hexane, methyl ethyl ketone, acetone, and diethyl ether will all do a fine job (Table 1) — though you'll probably want to stay away from ether for safety reasons. TenOfAllTrades(talk) 23:43, 20 February 2009 (UTC)[reply]
While we're on cleaning things. We had an antifreeze leak in one of our cars the other day. Since it is toxic (to our cats and other critters) I didn't want to keep the puddle on the concrete. My cleaning agent of choice is usually baking soda. It soaked up the puddle and I could sweep it onto a pan an toss it in the trash. Is there something better that one would find in a household moderately well stocked with ordinary chemicals? 76.97.245.5 (talk) 21:58, 20 February 2009 (UTC)[reply]
It's water soluble, so a few buckets of water or a hosepipe. As long as you use enough water, you'll dilute it to safe levels. (I doubt the total quantity was enough that you need to worry about general damage to the environment.) --Tango (talk) 22:02, 20 February 2009 (UTC)[reply]
Thanks. That would be nice, but we have water rationing. No outdoor water use, unless it's watering your veggies or your house is on fire. (I've been waiting for ages for it to be lifted so that I can power wash our entryway before re-grouting.)76.97.245.5 (talk) 22:15, 20 February 2009 (UTC)[reply]
Yes - I agree. Ethylene glycol is extremely nasty stuff - just one little taste of the stuff is enough to kill a young child or a dog. It's also very sweet - which attracts all sorts of animals (and when it's in a bottle - it looks exactly like gatorade - so kids think it's OK too). Diluting it is really the only safe way that I know of. I use sawdust to absorb as much as I can - then I hose down the driveway afterwards. If you have a hosepipe ban - can you use a bucket of bath water or something? Once you've got most of it soaked up, even just a single bucket of water should dilute it 100-fold - and that's probably enough. FWIW, here in Texas where it never really gets cold enough for long enough to freeze up a car - I've stopped using glycol in favor of water with 'water-wetter' and corrosion inhibitor. Pure water is more thermally conductive that water with glycol in it - so it actually cools your engine more effectively which generally gets you better gas mileage. However, you need some corrosion inhibitor - which is available at most auto parts stores as "water-wetter". Sadly, if you live in the snowy wastelands north of Dallas County - you should probably stick with regular antifreeze. SteveBaker (talk) 02:02, 21 February 2009 (UTC)[reply]
There are much less toxic antifreezes, based on propylene glycol. The principal reason ethylene glycol is toxic is that, in the body, it is first dehyodrogenated to glyoxal and then oxygenated to oxalic acid -- ironically (in the Alanis sense) this is, I believe, the pathway that the body uses to detoxify ethanol. Oxalic acid is the bad player here, largely because it forms crystals (or maybe its calcium salt does) in the kidneys, potentially destroying them.
Ah, looks like I oversimplified this a bit — according to our article on ethylene glycol poisoning, the main toxicity to the kidneys is from glycolic acid, an intermediate metabolite on the way to oxalic acid. So oxalates are maybe not quite as dangerous as one might calculate from antifreeze toxicity (go ahead and have that rhubarb pie! one of my favorites). --Trovatore (talk) 09:06, 21 February 2009 (UTC)[reply]
Thanks yall. I'll try using a bucket if it should happen again. Atlanta occasionally does get quite chilly. The antifreeze is refilled in the shop and I don't think we get a lot of say as to what goes in there. 76.97.245.5 (talk) 08:59, 21 February 2009 (UTC)[reply]
I'm sure they'll use propylene-glycol-based antifreeze if you ask. It's a little more expensive, but not terribly so — if someone else is changing your antifreeze then you're paying mostly for labor anyway. --Trovatore (talk) 09:06, 21 February 2009 (UTC)[reply]
←Ethylene glycol poisoning is the one I always remember due to it's somewhat fun treatment. First aid treatment consists of drinking a couple of beers. This acts as an antidotal therapy, helping to block receptors with comparatively harmless ethanol instead of ethylene glycol. —Cyclonenim (talk · contribs · email) 10:10, 21 February 2009 (UTC)[reply]
The principle is the same, I think — the ethanol competes for alcohol dehydrogenase, which is the enzyme that starts you down the road to the bad metabolites (glycolic acid and oxalic acid in the case of ethylene glycol; formaldehyde and formic acid in the case of methanol.
But people, seriously, if you've somehow ingested one of these things, don't screw around with a nice leisurely cocktail. Get to the hospital pronto. (Whether a shot or two of hard liquor would count as first aid, assuming someone else is driving you to the hospital, I don't know; it's an interesting question and one I'm not qualified to comment on.) --Trovatore (talk) 20:52, 21 February 2009 (UTC)[reply]
I would call an ambulance rather than get myself to the hospital. A nice gin and tonic (hold the tonic) while you wait for it to arrive might keep things from getting worse while you wait. I guess whether it's worth it depends on timing - if you're in the middle of nowhere and it's going to take a couple of hours for help to arrive, you should almost certainly down the gin. If it's a matter of a few minutes, maybe not - I believe it takes a few hours for the ADH to metabolise a significant amount (you don't have much ADH, so it can only process it so fast - that's why you are often still drunk the morning after a night out Well, I'm not, but I don't go out - I stay in and discuss the metabolic pathways of ethylene glycol with random people on the internet...). I also have absolutely no idea what the dosage would be... (my interpretation of a paper I read on the subject puts the necessary dosage at 20 times the lethal dose, so I think I got that wrong...) --Tango (talk) 23:36, 21 February 2009 (UTC)[reply]
I'll keep that in mind the next time I drink some antifreeze. ;-) More seriously, I'd be wary of feeding gin to a small child, who would be the most likely human victim of such poisoning. arimareiji (talk) 00:05, 22 February 2009 (UTC)[reply]
Indeed, that's where not knowing the right dosage becomes a real problem. With an adult I would just get them totally wasted and it would probably all work out fine. With a child, you have to get it just right, too much and they die of ethanol poisoning, too little and they die of ethylene glycol poisoning. That's why Fomepizole is the preferred treatment, unfortunately I don't keep any in my drinks cabinet... --Tango (talk) 00:32, 22 February 2009 (UTC)[reply]
@ Cyclonenim are you sure it's the alcohol in the beer that is the active ingredient here? I remember they had a couple of poisonings when some wine was mixed with ethylene glycol in Europe (quite a few years back). Ordinary beer doesn't have that much more alcohol I should think. It does contain a plethora of other things (like e.g. enzymes) that you might not find in wine. 76.97.245.5 (talk) 08:19, 22 February 2009 (UTC)[reply]
A little hooch along with your antifreeze isn't going to help much (though it might delay the damage for a time). Basically you have to stay drunk (I don't know exactly how drunk, but I have the vague notion that it's pretty damn drunk) until such time as your kidneys can cleanse out the glycol. That's going to take longer than the wine is going to last you. --Trovatore (talk) 08:42, 22 February 2009 (UTC)[reply]
It's definitely the ethanol. Putting anti-freeze is wine doesn't stop it being toxic - wine is generally only 10-15% ethanol, so even a fairly small amount of anti-freeze added will result in a similar amount of ethanol to ethylene glycol. You need a lot of ethanol to keep your alcohol dehydrogenase busy until the ethylene glycol has time to leave your body. --Tango (talk) 15:26, 22 February 2009 (UTC)[reply]
February 21
moving charges
Do accelerating charges produce magnetic field ?? I thought any moving charge would do {biot-savart law} but a man tells me that only charges that move with uniform velocity produce magnetic field. Is it true ? --scoobydoo (talk) 05:43, 21 February 2009 (UTC)[reply]
No, it's not true. As our article on magnetic fields points out, all moving charges produce a magnetic field. A charge that is accelerating is moving and so produces a magnetic field. The gentleman you were speaking to may having been referring to the fact that the Biot-Savart law covers the case of a charge which is moving with a uniform velocity, i.e. one that is not accelerating. - EronTalk05:58, 21 February 2009 (UTC)[reply]
Then,i suppose, the accelerating particle should produce time varying magnetic field?Do you know any such example ?? i've searched but can't find any example/application of a magnetic field produced by accelerating charges.
Also i wanted to know whether biotSavart Law has any limitations,ie whether it can be applied in all situations.{like newton's laws of motion in inertial frames only}--scoobydoo (talk) 10:00, 21 February 2009 (UTC)[reply]
The article, Liénard–Wiechert potential, explains in horrible detail all the mathematics you need to calculate the the electric and magnetic potentials and fields due to a single moving charge with arbitrary velocity. These formulations are essentially representations of the conceptual bridge between Maxwell's equations and special relativity. For any charge q with vector velocity v(t), you can derive an analytic expression for electric and magnetic potentials at all points in space at all times t. The equations dictate the propagation of those fields through time, and implicitly contain a relative velocity with respect to the source particle. Noting that the speed of light is constant, the speed of propagation of the fields is also constant; and this must be seen from all inertial reference frames via the concept of retarded time. Nimur (talk) 13:46, 21 February 2009 (UTC)[reply]
We cannot answer "When's it gonna happen?" because the Reference Desk is not a crystal ball. We do not foretell the future. Go find some gypsy for fortune teller willing to take your money and ask him or her.
It may not happen at all because some areas may be kept as nature reserves or parks, and it may also recover before it's destroyed. More likely for it's complete destruction would be by something like climate change: too much heat or a severe ice age. Looking at the figures from the source of the above article, the mean average annual loss in Brazil from 1988/2006 was 18 122 km2 (344 317 2 / 19). In 2006 there was about 340 0254 km2 left, so at the average rate it would take about 188 more years, or in the year 2194 - tho that's not a good way of estimating because the unknown variables are too many. -- Jeandré, 2009-02-21t08:43z
Collapsed content not directly related to the question
Uh, I've restored the parts of Kainaw's post that you saw fit to censor, Jeandré. That was pretty uncool. You got a problem with him, I recommend you use his talk page or open a discussion on the Ref Desk talk page instead. -- Captain Disdain (talk) 09:48, 21 February 2009 (UTC)[reply]
In my opinion, the reference desk is a hybrid - but it's much more of an interactive Mainspace than it is a Talk page. We don't censor each other's comments in Talk, true - but neither do we leave derogatory commentary up in Mainspace. This seems to fall more under the latter than the former. arimareiji (talk) 14:47, 21 February 2009 (UTC)[reply]
And yet, if I were to modify your comment above, I doubt that'd be very constructive or useful. I'm sure I could come up with a reason, too. Would it be complete crap? Absolutely! Could I still take up a lot of time and energy by disingenuously debating it and drawing everyone into the resulting crapfest? You bet -- and that'd be without you even having to say something I actually found to be offensive. If someone says something you find derogatory, feel free to object, but don't start messing with their words, because it's a can of worms, and no good will come of it. None. -- Captain Disdain (talk) 15:22, 21 February 2009 (UTC)[reply]
On a gut level, I find it hard to disagree with you since I'm very fresh off of dealing with a %!#@$%#% who kept editing and deleting my Talk posts about an article because he didn't like them. But on an intellectual level, this was and is rapidly becoming moreso a matter of open poo-slinging in what is much more of a public space than it is a talk space, and thus not protected by "freedom of speech". arimareiji (talk) 16:23, 21 February 2009 (UTC)[reply]
A couple problems with just taking the current rate of deforestation and extrapolating that to determine when all the forest will be gone:
1) As forest becomes more rare, it becomes more valuable, say as a tourist attraction, and thus there will be more incentive to keep it.
2) A deforested are can become forested again. This can happen naturally to an area which is abandoned (let's say it was deforested during mining, then the mines all played out and everybody left). Trees can also be intentionally replanted for future logging, to make a place more attractive to tourists, to stop soil erosion, etc. StuRat (talk) 19:34, 21 February 2009 (UTC)[reply]
And from the opposite side:
The "critical mass" aspect - surely no one would argue that a few square meters of "rainforest" can survive very long. The trouble is, no one knows where the dividing line lies between survivability and eventual extinction. See Population bottleneck.
Technology - Villagers getting firewood don't do nearly as much damage as a farmer clearing land don't do nearly as much damage as an airplane spraying defoliants. Which will predominate is variable, especially in the age of genetically-engineered crops.
A computer model prediction of global warming and regional temperature rise, assuming a rise in global temperatures of 3C by about 2070 - 2100.
Actually, the Amazon rainforest is widely predicted by computer models on global warming to collapse if global temperatures rise more than 2C (3.6F), and such a temperature rise is likely before 2100. Temperature and vegetation models both predict this, and some of this extra temperature rise in maps is depicted in our article, global warming. In at least one book I've read on GW (and I've read about a dozen by now), the prediction is that once global temperature rise exceeds 2C, a "firestorm", literally a wall of fire, would sweep across the Amazon basin from the northeast inwards, turning the region into desert. In another book, it depicted three possible scenarios in the 21st century: a) the collapse of the Gulf Stream; b) the collapse of the Amazon rainforest; or c) the release of methane clathrates from the seabed. The book claimed that "c)" was the least likely to occur this century, but if peliminary results from the AGU are correct, then the clathrates are already being released. I don't think deforestation will be quick enough to destroy the Amazon rainforest before that potentially happens. ~AH1(TCU)00:27, 22 February 2009 (UTC)[reply]
Dadgummit, why'd you have to not provide an explanatory link to AGU? :-) arimareiji (talk)
"Widely predicted" is too strong. Some models show a catastrophic collapse of the rainforest this century (including the one pictured), but a majority of current models have it continuing to be present through 2100. Eventually climate change may make that biome unsustainable, but there isn't a lot of agreement on how much warming must occur before that happens. Dragons flight (talk) 19:35, 22 February 2009 (UTC)[reply]
Did Ross actually deserve his Nobel in 1902?
Grassi challenged the Nobel awarded to Ross,the India born doctor claiming he had a better claim!Does the wiki community agree?(Ramanathan) —Preceding unsigned comment added by 212.247.70.129 (talk • contribs) 06:57, 21 February 2009
From the top of the page: "The reference desk does not answer requests for opinions..." There are other internet sites that are appropriate for discussing personal opinions. The Reference Desk is for answering factual questions. You may be interested in searching for internet forums where topics such as Nobel prizes or scientific claims are discussed. 152.16.59.190 (talk) 04:52, 22 February 2009 (UTC)[reply]
You might want to try your luck posting this question on the entertainment RD, here. Not only would you probably get a better answer, but the entertainment desk looks a little sparse; it could use an extra post or two. -Pete5x5 (talk) 06:41, 22 February 2009 (UTC)[reply]
Scientists with distinguished contribution to literature
Apart from Bertrand Russell who won teh Nobel in literature are ther any other scientists who have distinguished themselves in this manner?(Ramanathan) —Preceding unsigned comment added by 212.247.70.129 (talk • contribs) 07:01, 21 February 2009
In what manner? As far as I know, no other scientist has won the Nobel Prize in Literature. But many scientists have also been successful popular writers. Richard Feynman has written two widely read collections of autobiographic sketches. Stephen Hawking has popularized his research very successfully, and so has Richard Dawkins. Vernor Vinge, probably best known for his acclaimed science fiction, is a computer scientist. Isaac Asimov was a biochemist and held a professorship, and E. E. Smith was a practicing food scientist. John Norman is a professor of philosophy (if you call this a science, and if you consider his writings literature). These are just some examples from my bookshelf (and this may give away too much about my reading habits ;-). --Stephan Schulz (talk) 11:20, 21 February 2009 (UTC)[reply]
Well Bertrand Russell did.and he was a scientist that is why I asked the question.And my colleagues tell me Omar Khayyam was another(Ramanathan)
Though I would hesitate to call much of the above "literature"... being a popular science writer, or able to write a witty autobiography, is not at all in the same class as a Nobel Prize in Literature... Ernst Mach, by contrast, was both a famous physicist, but perhaps an even more famous philosopher/author during his day, not writing up popular accounts of science, but making strong arguments about the nature of science and experience, to the point where none other than Lenin himself decided to denounce his work. Gould, Feynman, Dawkins—good writers, all, but their literary works are not exactly world-shaking... --98.217.14.211 (talk) 20:11, 22 February 2009 (UTC)[reply]
Hybrid eclipse: both annular and total at the same place?
"A hybrid eclipse (also called annular/total eclipse) transitions between a total and annular eclipse. At some points on the surface of the Earth it is visible as a total eclipse, whereas at others it is annular." -- Solar eclipse.
Is it possible to, from one specific place on Earth, see an annular eclipse become a total eclipse (or the other way) if standing at the correct place during a hybrid? -- Jeandré, 2009-02-21t11:14z
The answer is yes, and in situations much more common than that proposed by Cookatoo. There will be a very narrow region in the path of a hybrid eclipse where it transitions from total to annular (or vice versa). At the midpoint of that region, two minutes of totality would be one minute of an actual total eclipse and one minute of an annular. — Lomn14:42, 21 February 2009 (UTC)[reply]
The answer is "No." During an eclipse, at any one point on Earth, the Moon covers up a certain percentage of the Sun. Let us suppose the Moon is covering 99% of it, thus presenting an annular eclipse. In order for the eclipse to become total, one of four things (or a combination of them) would have to happen: (1) the Moon suddenly grew larger, (2) the Sun got smaller, (3) the Moon got closer to the Earth, or (4) the Sun got farther from the Earth. Since all four are impossible to the extent needed in the few minutes of an eclipse, it can't happen. B00P (talk) 11:20, 22 February 2009 (UTC)[reply]
Well, yes, I did think of that knife-edge case - note that I specified 99%, not 99.9999% - but then where does one draw the line between annular and total? So, I'll grant that RunningOnBrains is correct, but still maintain that the answer is "no" in any meaningful way. B00P (talk) 06:03, 23 February 2009 (UTC)[reply]
Oh Jeez - what a lot of crappy answers! No, no, NO!! Think about the reason that some eclipses are annular and some are total. It is because the earth's orbit around the sun is not a circle. It's an ellipse. Hence at some times of year the earth/moon system is closer to the sun and at other times we're further away. Hence the sun appears to be slightly larger or smaller. Hence the moon sometimes completely covers the sun at the moment of 'totality' and at other times of the year doesn't completely cover it. It has absolutely nothing to do with where you are on the surface of the earth. It might seem that the moment just before or just after a total eclipse is "annular" - or if you are not quite in the path of 'totality' that it might seem to be 'annular' but in those cases, the ring of sunlight around the moon won't be a complete circle which is the defining feature of an annular eclipse. A true annular eclipse cannot precede or follow a total eclipse because the distance the earth travels around it's orbit is negligable over the few minutes of totality or annularity. QED. SteveBaker (talk) 14:08, 23 February 2009 (UTC)[reply]
the e = mc2 has been derived in a very easy way. But my doubt is that the 'm' in the derived equation is actually the mass of the photon. It means that photons and hence, energy has mass. But how can you say that any mass has energy equal mc2? 1kg of gold costs a lot. But 1kg of any mass doesn't cost that much. A photon may have some mass equal to E/c2 . But anything with mass m may not have energy equal to mc2. Please correct me if i am wrong anywhere. I have understood the derivation but i got this doubt. I also know that matter reacting with antimatter produces energy equal to mc2. Please explain my doubt.Also I am just 14 years old and so, please explain in a nice way.
--Harnithish (talk) 11:31, 21 February 2009 (UTC)[reply]
Actually, E=m*c^2 only holds for non-moving objects (that is, objects that aren't moving in the reference frame of the person who calculates E=m*c^2 ).
The more general formula is E=gamma*m*c^2, where gamma is the Lorentz factor gamma=1/sqrt(1-v^2/c^2).
Another formula, directly applicable to photons is
E^2=m^2*c^4+p^2*c^2
where p is the momentum of the particle
p=gamma*m*v
In other words, the energy of the photon is not due to its mass (m=0) but due to its momentum.
(Some physicists consider mass to be velocity-dependent and define the relativistic mass
m=gamma*m0
where m0 is the rest mass, the mass an object has according to an observer in whose reference frame the mass is at rest. Photons then, have zero rest mass but not zero relativistic mass.)
Summary : no, you can't apply E=m*c^2 to a photon, because the photon is not at rest in your frame. —Preceding unsigned comment added by 81.11.173.78 (talk • contribs) 09:50, 21 February 2009
In answer to the other question (if it is a question), equal masses of substances can have different values despite having the same energy because we can't convert between them. For example, an apple's worth of energy could power vast parts of the world, and therefore be worth a lot. however, we can't convert the apple to energy (yet), so it's not worth that much. - Jarry1250(t, c)13:57, 21 February 2009 (UTC)[reply]
We talk about the photon as though it were a little ball that someone could catch in a butterfly net and look at. In fact it is only a conceptual model that has been constructed to satisfy the need to explain how electromagnetic energy propagates seemingly without any mass transfer. Cuddlyable3 (talk) 14:00, 21 February 2009 (UTC)[reply]
what is "Vital fluorescent staining" ?
Google give plenty of search results for "Vital fluorescent staining", but they're all "Application of a Vital Fluorescent Staining...", "Development of a vital fluorescent staining...".
I can more-or-less figure out what it should be from the context in which I read it, and from this wikipedia article:
http://en.wikipedia.org/wiki/Staining
Presumably it's some kind of indicator that can be added to bacteria cultures and differentiates between living (vital) and dead bacteria? —Preceding unsigned comment added by 81.11.173.78 (talk • contribs) 09:41, 21 February 2009
Your sense is correct, but this is not limited to bacteria. You'll find a lot of useful information using Google (or other search engine, even Pubmed) with the example of Acridine orange and "vital". I must agree, though, that our content on WP is either hard to locate or lacking. --Scray (talk) 16:12, 21 February 2009 (UTC)[reply]
Vital staining (vital in this case referring to vita, Latin for life/living) of any type is that which is done on live (as opposed to fixed tissue. It can involve chemicals, like acridine orange mentioned above, or the addition of markers (like fluorescently labelled antibodies or tagged proteins, e.g. for FAC sorting) to the outside of the cell. -- Flyguy649talk20:59, 23 February 2009 (UTC)[reply]
Hypothetical lifeforms on earth
What might life be like on earth if earth was orbiting a blue giant star instead of the sun? (that is if the earth was far enough away from the blue giant to prevent it from being too hot for life)? Also what might the landscape (aside from the earth having no moon) and life be like on earth (and possibly thea) be like if they never collided 4.4 billion years ago? —Preceding unsigned comment added by 99.146.124.35 (talk • contribs) 10:14, 21 February 2009
Blue giant is just one short stage during the death of a star. Only very massive stars become blue giants and such large stars don't live as long as our Sun. There probably wouldn't be time for life to evolve, at least not complex life. There has been a lot of discussion about what the Earth would be like without the Moon - basically it would less stable (the axis of rotation would move around more) and there would be much weaker tides (there would still be some due to the Sun). It's impossible to say what Theia would be like, it would have to have been thrown out of Earth's orbit somehow and what would happen to it depends on where it ended up. I don't think the Earth would be much different otherwise, it would be slightly smaller, but probably not sufficiently smaller to make a great deal of difference (gravity wouldn't be very different, since its smaller mass would be partially offset by the surface being closer to the centre). The length of a day would be very different (it's difficult to guess what), and the axis might be in a very different place (although it would be moving quite a bit anyway, without the Moon). --Tango (talk) 14:37, 21 February 2009 (UTC)[reply]
The last episode of The Future is Wild, The Tentacled Forest left off at 200 million years later. What might the next lifeforms and landscapes on earth be (assuming that the shows predictions about the first 200 years were correct) after the time when the show left off?--99.146.124.35 (talk) 14:58, 22 February 2009 (UTC) Perhaps 250 million 300 million 400 million years 1 billion years in the future?--99.146.124.35 (talk) 15:02, 22 February 2009 (UTC)[reply]
As to the first question, life would have to adapt to the higher percentage of UV radiation, so you'll see less life in the open and more animals digging themselves in, probably thicker skins and more eye protection. --Ayacop (talk) 16:03, 22 February 2009 (UTC)[reply]
I'm wondering why the human iris has a colour. Not so much from a physical standpoint (the wikipedia article on iris colour is quite thorough on that part) but rather from an evolutionary standpoint. Why isn't the iris just white like the sclera? What function do all those colours have? PvT (talk) 16:10, 21 February 2009 (UTC)[reply]
My guess is that it's the same reason as hair color: complex, somewhat linked to other pigments (e.g. skin) and ethnic history/climate, and especially subject to conjecture and junk science. --Scray (talk) 16:40, 21 February 2009 (UTC)[reply]
I realized that answer to part of your question is that the iris is part of the uvea, the pigmented layer between the sclera and the retina. This helps to understand that the iris is part of a pigmented layer of the eye, but precisely why the iris appears the way it does is more complex than that. --Scray (talk) 16:47, 21 February 2009 (UTC)[reply]
I understand that the iris is there to regulate the amount of incoming light. However why specifically does the iris have a colour as opposed to being white like the neighbouring tissue. I think Scray helped me out quite a bit. If the iris is an extension of the uvea then it makes sense that it would appear different from the sclera (it's a different type of tissue afteral). What puzzles me is that if the iris is only there to regulate the size of the pupil than why does it need any specific colour. To me it seems that to fulfill this job the iris doesn't need to have any specific colour, as long as it's not translucent. PvT (talk) 17:54, 21 February 2009 (UTC)[reply]
Precisely. It's also fascinating to note how variegated iris color is (just look at the image on that page, or take a close look at a loved one's). Is that beneficial or an accident of embryology? I have a feeling that this could lead into the field of psychology, etc - very complex and currently unanswerable in any concrete way. But certainly worth asking! --Scray (talk) 18:12, 21 February 2009 (UTC)[reply]
The trouble with using albinism as an illustration is that it's not isolated to the iris. The entire pigment layer is important to normal eye development, probably because light bouncing around inside the globe is as (or more) problematic as light passing through the iris. Without separating the effects of light transmission through the iris and light reflection within the eye, the benefits of iris pigmentation cannot be assessed at all. --Scray (talk) 17:49, 21 February 2009 (UTC)[reply]
I'd say that eye color, among many other features, is used to identify individuals. This is important to any social animal, as identifying different individuals is key to survival ("stay away from the one with the dark brown eyes, he's overly aggressive"). And, since humans use visual cues far more than smells or other senses, it would make sense that we would have more visual cues to distinguish one another than other animals that doesn't rely so heavily upon the visual. StuRat (talk) 19:14, 21 February 2009 (UTC)[reply]
Genes that influence eye colour are involved in other processes. Consider, for example, HERC2 and OCA2. They are also involved in regulating - among other things - skin colour. So its entirely possible that different eye colours are a selective side effect of pressures on the genes in other functional contexts. Sexual selection may also have driven variation. Note also the the variation in eye colour is largely due to physical, schemochromatic effects. So light bouncing around off structural, protein fibres and a few melanosomes gives eyes a blue colour. These fibres and melanosomes have other biological roles, so it could simply be that their colour is a subsequence of that. Rockpocket00:59, 22 February 2009 (UTC)[reply]
Dysfunction in the instinct of nature
So I assume that all species have instincts to protect and nurture their young etc. but was there ever any natural deviant in which any living being seemingly didn't work instinctually and did the opposite? Like instead of nurturing, hindering. If there was how could they naturally bear offspring in the first place if apparently their instincts malfunction? 94.196.9.90 (talk) 17:25, 21 February 2009 (UTC)[reply]
Every animal is capable of it in conditions of high stress and overcrowding, from what I've heard. Any relationship between this and Jerry Springer modern human society is purely coincidental. ;-) arimareiji (talk) 18:23, 21 February 2009 (UTC)[reply]
One could also claim that the instincts of self-preservation and species-preservation can come into conflict. After all, in times of scarcity, self-preservation may take over. After all, I can always have sex again. But if I don't live through this winter, maybe not... Just a WAG... --Jayron32.talk.contribs19:32, 21 February 2009 (UTC)[reply]
The goal is always to have as many of your offspring as possible reproduce, but it doesn't matter which ones. If your current young aren't likely to survive that long whatever you do, caring for them is a waste of resources that would be better spent making sure you survive long enough to try again. I think that's the principle behind infanticide in animals. --Tango (talk) 20:53, 21 February 2009 (UTC)[reply]
I recall reading that a relatively large percentage of giant panda mothers either don't know how to care for their young or aren't interested in doing so. I'm not sure if this only applies to those born in captivity, but it's a challenge to increasing their numbers. StuRat (talk) 12:31, 22 February 2009 (UTC)[reply]
Are you asking about species that tend to eat their young, or specific animals that somehow don't have the nurturing instincts shared by the rest of their species? — DanielLC17:22, 23 February 2009 (UTC)[reply]
Burns
Why is it exactly that the medical community (and, subsequently, the media) expresses burn injuries in terms of percentages? I have read the Wikipedia articles on Burn and on Total body surface area. But, they did not really address my question. When we read a newspaper report of a burn injury, it will invariably state something along the lines of "The victim suffered burns on 78% of his body" (or something like that). Why exactly is this important? Any insights? Thanks. (Joseph A. Spadaro (talk) 22:03, 21 February 2009 (UTC))[reply]
The medical community is probably, for the most part, more concerned with the degree of the burn. But a burn is essentially a wound, an opening in the skin through which infection can travel. So a larger percentage burn means a larger surface area that's open to infection, and a concomitantly greater burden on the immune system to defend. As the burn article notes, "Infection is a major complication of burns". The burn article, and the Servitt article linked from it, indicates that the burn affects the body's fluid regulation systems - bigger burn->greater disruption. 87.112.17.229 (talk) 22:57, 21 February 2009 (UTC)[reply]
The immune system can't the only one that's burdened either. I don't know specifics, but there must be other body systems that are hugely impacted by having to heal such a large amount of skin and other tissues. --Anonymous, edited 00:24 UTC, February 22, 2009.
The reason the percentage is reported is quite simple: prognosis. The larger the area, the less likely that the patient will survive. One formula, for example, where TBSA = total burn surface area is: percentage chance of survival = (100 - (age in years + TBSA)). So a 60 year old with a 30% TBSA has a 10% chance of survival, and a 20 year old with a 30% TBSA has a 50% chance of survival. A 25 years old with a 78% TBSA would by this calculation have a -3% chance of survival - that is, his death would be expected. Obviously these are estimates. To a certain extent, the prognosis will influence treatment by indicating who will be most likely to benefit from intensive specialized burn treatment at a dedicated burn center facility. - Nunh-huh00:35, 22 February 2009 (UTC)[reply]
That formula says that a 60 year old person with no burns whatever has only a 40% chance of survival, so it seems pretty absurd. Survival for how long? 30 years? Who sits around making up such formulas? Are they based on empirical data or intuition? Edison (talk) 01:22, 22 February 2009 (UTC)[reply]
Obviously formulas for predicting the likelihood of surviving a burn are going to produce absurd results when applied to people without burns. The "survival" in question is survival of the acute burn episode - that is, recovery sufficient to eventually die of something else. Clearly the formulas are based on empiric data - no one would publish a formula based on intuition. For some people involved in using TBSA to predict survival, have a look at "Health Watch; Predicting Burn Survival". New York Times. New York Times. 10 February 1998. Retrieved 22 February 2009. {{cite news}}: Cite has empty unknown parameter: |coauthors= (help), or have a go with the editorial: Saffle, J.R. (5 Feb 1998). "Predicting Outcomes of Burns". New England Journal of Medicine vol 338. pp. 387–388. {{cite news}}: |access-date= requires |url= (help); Cite has empty unknown parameter: |coauthors= (help). Medline searching will also return various papers. - Nunh-huh01:41, 22 February 2009 (UTC)[reply]
The formula is clearly a first-order approximation of the real formula. It's only going to be accurate near whatever point it was approximated about (which will have been a significant burn area and a non-elderly person - exactly where they approximated, I have no way to know). --Tango (talk) 02:17, 22 February 2009 (UTC)[reply]
Hmmmmmmmmmmm. Maybe I mis-spoke when I worded my original question. I agree with all of the above. And it makes sense that the more burn area (percentage), the more danger to the patient/victim. But, isn't this all of interest and concern to the doctors and medical treatment staff only? Why is this of concern to journalists and the news media (and their audiences)? When I watch or read the news, I never hear anything like: "The victim required 28 stitches" ... or ... "The victim required 7 pints of blood" (etc.). Those details are important to the medical treatment staff, but not important to the television or newspaper audience. So, why is the burn percentage treated differently? Yes, it's important to the doctors and treatment staff to know the burn percentage. But, why is it so important to the general news media audience that it is nearly always reported? That was really what my original question was getting at. Thanks. (Joseph A. Spadaro (talk) 02:42, 22 February 2009 (UTC))[reply]
The number of stitches is of only passing interest medically. Same for units of blood transfused (sometimes, but not consistently of major concern). In contrast, burn area is always important when burn is the primary injury, it is mentioned every time clinicians present a burn patient to one another, and burn centers report it (along with survival rates) to the entities that fund them. So, it's almost always known to the person being interviewed by media. People being creatures of habit, they report it to the media, and the media pass it on. --Scray (talk) 03:40, 22 February 2009 (UTC)[reply]
And since the area burned affects the probability of survival, it is of interest to the news media's audience. Well, maybe not you, but to some of the audience. --Anonymous, 06:53 UTC, February 22, 2009.
Also, even if the audience isn't aware of the relationship between the burn area and survivability, it's still pretty informative: "78%? Geez, that's a lot, that's bad." -- Captain Disdain (talk) 08:07, 22 February 2009 (UTC)[reply]
What the media want is to concisely quote a single, supposedly empirical, value which conveys degree of injury. They really want to say someone was burned 30% to death, or the car crash reduced their life to 25%. Of course you can't really reduce complex medical conditions and their prognoses to a single statistic, which is why it's nearly meaningless; it's just like a report of a fire being "3 alarm" or a report of the "bodycount" of a military operation. And I don't agree that news outlets don't use the stitches count as another false statistic: [29], [30], [31]. or pints of blood transfused [32], [33], [34]. It's the same for the number of bones broken (or in how many places a given bone was broken) during an incident. 87.112.17.229 (talk) 11:44, 22 February 2009 (UTC)[reply]
I still say the formula is extremely silly and could not be based on data. A 50 year old person with no burns, or burns over .0000000000001% of the body has only a 50 % survival rate? Utter nonsense. As for the percentage of body burned, it is not a literal measurement. There are tables stating what percent the legs, arms, back face, or hands are, and it is just added up. There is no literal measurement of square centimeters burned, by careful measurement of irregular burned areas, versus total square centimeters. Edison (talk) 03:18, 23 February 2009 (UTC)[reply]
Here is the original study in the New England Journal. Alternatively, you could use this formula: logit = -7.37 + 0.05(age) - 0.15(year) + 0.11(% body-surface area) - 6.61 x 10-4(% body-surface area - mean % body-surface area)2 + 1.04 x 10-3(age - mean age)2Axl ¤ [Talk]16:45, 23 February 2009 (UTC)[reply]
As I explained above, the formula is quite clearly a first-order approximation (you can tell because it's all linear and the true formula obviously can't be since it is bounded). If you try and apply a first-order approximation significantly away from the point it was approximated about, you will get nonsense. --Tango (talk) 16:52, 23 February 2009 (UTC)[reply]
February 22
Cardinal repeatedly flies into window
A male Cardinal is repeatedly flying into my windows, from dawn until evening. There is the fire escape and bamboo outside the windows for the cardinal to sit on. I assume it sees its reflection and thinks its another bird (competition) and tries to attack it. Apparently it's not hurting itself, since this has been going on for months.
I'm thinking of putting up window clings, such as the Halloween decoration ones that might be scary to the bird. But, it's not halloween, so Halloween decorations are probably not available now :( What type of window clings can I get this time of year (in the Maryland/DC/Virginia area) that would scare the bird? and what stores would sell them? Would a craft store (e.g. Michaels) have them? or would Home Depot have something to help solve my problem?
I have a window sticker in the shape of a raptor, which I got from a pet store (in the same department that sells wild bird feeders and food). It has successfully dissuaded similar bird attacks. 87.112.17.229 (talk) 15:42, 22 February 2009 (UTC)[reply]
I have to assume the bird suffered from brain damage the first time, which might explain why it never learns. :-) How about cat-shaped stickers ? Also, if you have lights on behind the window it will make the reflection less noticeable relative to the light. A more expensive option would be to install louvered window shutters. If you don't care about the bird you could also poison it. StuRat (talk) 16:13, 22 February 2009 (UTC)[reply]
It doesn't matter what you stick on the windows, as long as there is something there. In Switzerland I believe it is required by law to put such stickers on any glass larger than a certain size (they almost all use silhouettes of birds). --Tango (talk) 16:21, 22 February 2009 (UTC)[reply]
Gold
I have always ask this question ,,, why would any one buy gold ,,,
what's the point ,,, its not usefull ,,, there's no god reason to buy this metal
with that big amount of money .
and the most confusing ,,, why countries take the gold as auniversal coin ,,,???
from my opinion gold worth nothing ... as amatter of fact even iron could be more
usefull than gold.
That's not true - gold is used pretty extensively in electronics manufacturing - all of the connectors on circuit boards have a thin layer of gold plated on them. The tiny chip of silicon inside a the plastic or ceramic packaging of an integrated circuit is connected to the pins on the outside of the package with thin gold wires. Gold has practical uses. SteveBaker (talk) 19:15, 22 February 2009 (UTC)[reply]
See gold. You will find that there are applications for which gold is useful and for which creates value. If you are wondering why certain metals are precious, you might try reading precious metals. -- kainaw™18:52, 22 February 2009 (UTC)[reply]
Gold:
Does not corrode. Ever.
Is an excellent conductor of heat and electricity.
Has an unusual and generally desirable appearence.
Is relatively rare.
I'm sure there are more reasons, but these qualities alone make gold in high demand for electronics, medical applications, and jewelry. Thus, a high cost. -RunningOnBrains18:53, 22 February 2009 (UTC)[reply]
Although what the above posters have said is true, Gold is still probably not worth $1000 an ounce. The desirable appearance that RunningoOnBrains mentioned is probably what emotionally influences people enough to want to buy it as a safe haven. I personally would buy honey or something else widely useful which has a very long expiry date and low (or preferably negative) depreciation. See also: diamond-water paradox. This is what the richest man in the world has to say about gold:
Buffett emphasized the non-productive aspect of gold in 1998 at Harvard: "It gets dug out of the ground in Africa, or someplace. Then we melt it down, dig another hole, bury it again and pay people to stand around guarding it. It has no utility. Anyone watching from Mars would be scratching their head."
To fully understand the value of gold, we should dig back in time to the era before stock markets and internet banking. Creating a universal currency boosted the trade and economy (it's easier to trade with gold, than barter two cows for five sheep, for example) It was rare enough for a small quantity of it to have a good value. If money would be made out of stones, everyone would gather tons of it, leading to an inflation where you needed a wagonload of it to buy a chicken. (With most of our money being created by banks and not having any physical form, this scenario could be not that far from being reached :P ) --131.188.3.20 (talk) 23:22, 22 February 2009 (UTC)[reply]
We just had this question a few days ago on the Miscellaneous reference desk.
You will want to read the thread over there. --Anonymous, 00:21 UTC, February 23, 2009.
Actually, the non-utility of Gold is exactly what makes it a good medium for money. If gold had a use, then its utility value may someday exceed its monetary value, which would be bad indeed for the economy. Look at other materials once used for money: Salt was used by the Roman Empire as a means of exchange (hence, "salary"). However, salt is inherently useful in preserving and seasoning foods, and other applications. So if your money is salt, either a) you have to let food rot, because its too valuable to waste salt when you could be spending the salt to buy other things; OR the salt is needed to be used as a preservative, at which point it must be pretty worthless as money, since if it HAD monetary value, you wouldn't want to waste it. Good money has some common properties: 1) It is rare and hard to counterfeit 2) It is otherwise useless. You need both in order to have good money. Salt failed on both counts. Look at wampum as an example of of money. When made by hand, it had both properties, being hard to make, and it also had no use except as money. When the Europeans came along and figured out how to mass produce wampum in factories, it very quickly lost its rarety, and then just became worthless trinkets. Gold, silver, and copper in the ancient world were far to soft to be useful for what you would normally want metal to do, and they were all relatively rare compared to other metals. Thus, they made excellent metals to make money out of. --Jayron32.talk.contribs03:28, 23 February 2009 (UTC)[reply]
The article you linked clearly names them i-doser. Notice, that link is blue. That means that if you were to type it in the search box on the left and click Go, you would find an article on the topic. -- kainaw™18:48, 22 February 2009 (UTC)[reply]
So... it means that some kids decided to take something that is well over 100 years old, give it a new name, and hype it up to be something it isn't. It isn't all that surprising, is it? -- kainaw™21:24, 22 February 2009 (UTC)[reply]
Without doubt, certain music and audio can create a psychological effect. But unless it creates a psychoactive effect with measurable neurological effects, I don't think it can be classified as "drug-like." Lots of behaviors can create feelings of euphoria or elevated perception without being "drug-like" ... From our article drug,
“
A drug, broadly speaking, is any chemical substance that, when absorbed into the body of a living organism, alters normal bodily function. There is no single, precise definition, as there are different meanings in drug control law, government regulations, medicine, and colloquial usage.
”
Evidently, until a reliable medical, legal, or pharmacological source makes a specific mention of audio-induced psychoactive response, these sorts of things will not be widely considered "drug-like." Nimur (talk) 15:37, 23 February 2009 (UTC)[reply]
Do you have an infinite believe in human intelligence? Would people use a tried-and-true way of predicting bubbles or would they believe that they use an-even-better-tried-and-true way of predicting bubbles? Anyway, I want to know what are the signs of bubble forming, not necessarily how to predict when it will explode. --Mr.K.(talk)20:00, 22 February 2009 (UTC)[reply]
If you could predict whether something was a bubble, you could make an awful lot of money. There was a very big and rapid one last summer. A certain Mr. Soros claimed oil was a bubble at $135 a barrel [35], it peaked at $147 per barrel (pb) and is currently at $39pb. I think the low since $147pb is about $30pb, so had Soros sold short 10,000 barrels at $135pb and bought back at $35pb, he would have made $100 * 10,000 = $10,000,000. I don't know whether he did, and if he did, what quantity (probably alot more than 10,000 as $10m profit is kinda small change to someone worth $9 billion). --Mark PEA (talk) 20:42, 22 February 2009 (UTC)[reply]
You can tell a bubble situation when the price is well above what it is worth, and it is purchased because of the belief that the price will rise. It is harder to notice then the pop will happen. But a good clue is when the item become unaffordable for those that have to buy it. Graeme Bartlett (talk) 20:50, 22 February 2009 (UTC)[reply]
Indeed, something that is supposed to serve a purpose being traded more by speculators than by consumers is generally a good sign of a bubble. --Tango (talk) 22:00, 22 February 2009 (UTC)[reply]
I disagree with your logic. Saying "a price is well above what it is worth" is impossible to know. No one can estimate the price consistently better than the market can. Otherwise they'd be filthy rich. So the best estimate most people (like the OP) can use for the price of a good is simply the market price. Thus the price is never more than what it is worth. Speculators aren't dumb. They buy when they think prices are going to rise. Often the speculators are right (or else they would have lost all their money long ago). Despite the portrayal of oil speculators recently by the media, speculators don't "artificially" increase the price. They increase the price based on uncertain factors which could potentially make the stock worth quite a bit more. When google offered their IPO, if I buy it because I think they'll do well their first year, that is speculation, but it also moves the price to where it SHOULD be, I'm not artificially increasing the price.
To answer the OP's question, you can't always tell by the price if something is a permanent change or temporary change no matter how much it changes. The best way to see a bubble coming is to look for factors that would shift a price from what it would be in a fair market. In a true free market there would not be bubbles. Most bubbles are caused by politians trying to manipulate the economy. Both President Bush and President Clinton made speeches, especially when addressing hispanic audiences, about trying to make it easier to get low income and minorities into affordable homes. By the Federal Reserve artificially adjusting the interest rates and passing laws to incentivize first time home buyers they caused the price to increase far above what market value would have otherwise been. Now that President Obama has passed the bailout which gives a $8,000 tax credit to any first time home buyers during calendar year 2009, again it is pushing the price far from the market value and as such is a very dangerous move.Anythingapplied (talk) 07:29, 23 February 2009 (UTC)[reply]
If you buy Google stock because you think Google will do well next year (fundamental analysis), that corrects the price. If you buy it because you think the stock price will go up, with no regard to the company, (technical analysis) then that "artificially" changes the price and results in bubbles. Saying "price greater than worth" doesn't make much sense without clarification. To calculate worth, in this context, you need to look at what the item is useful for and compare it to possible replacements. If genetically engineered blue rice is 1000 times the price of regular rice, despite it going just as well with a Chicken Korma, then that's a clear sign that there is a bubble on blue rice. People aren't buying it because they think it's worth that amount of money, they're buying it just so they can sell it later after the price has gone up. --Tango (talk) 12:12, 23 February 2009 (UTC)[reply]
The trouble is that it's a self-non-fulfilling prophesy. If you have an equation that predicts the moment when the bubble will burst, investors will buy stock knowing that the bubble is still growing and that they can safely sell on the trading day immediately before the equation says it'll burst. However, if the equation is sufficiently widely known that people would tell you about it on the Wikipedia reference desk then you can bet that all serious investors will know it. Hence they'll all sell their holdings on the day before the bubble bursts - the stock price will tank because every big investor dropped their holdings in the stock at once - and the bubble bursts a day before the equation says so (and if everyone knows that - then two days before - or a month before...) - and the equation is thereby proven useless. So not only is there no such equation - but there cannot ever BE such an equation so long as investors are aware of it and are able to take advantage of it. SteveBaker (talk) 23:29, 23 February 2009 (UTC)[reply]
OK, there is no way of predicting when it will burst. However, a partial question is how can we know the market is building a bubble? (if we can at all know that a bubble is growing).--Mr.K.(talk)09:20, 24 February 2009 (UTC)[reply]
@Mr.K.: You can't know. You are effectively asking the question "What will the price of X be in the future?", but in an indirect fashion. If anyone can figure out that something is a bubble, but not know when it bursts, you can short sell it. However this assumes that when the bubble bursts, the price will be less than that you shorted it at. --82.21.28.65 (talk) 18:04, 24 February 2009 (UTC)[reply]
(Which is perhaps the only paradox that really seems paradoxical to me...the others seem entirely trivial to dispel. The only halfway reasonable way to explain it away is to assert that 'unexpectedness' is not a binary thing - there are degrees of unexpectedness. However, one would expect an equation to produce a definite answer. But you're right - and it could be that a 'when will the bubble burst' equation would be possible if it only predicted a statistical likelyhood of the bubble bursting at any given moment. As the predicted probability of the 'bust' happening increases (per the equation) - the risk-averse investors would pull out first with fewer and fewer of the high-risk-tolerant people staying around...that would allow the equation to predict the probability of a bust on any given day - despite all of the investors knowing about it.) SteveBaker (talk) 21:14, 24 February 2009 (UTC)[reply]
It's easier to spot a bubble from outside, rather than being inside the bubble. eg Most people working in McDonalds etc would be fairly aware that profitting by buying and selling commodities without adding any value to the commodity cannot continue forever. In other words look for the price of something increasing for no good reason beyond that explained by common or garden inflation. —Preceding unsigned comment added by 213.249.232.187 (talk) 15:51, 24 February 2009 (UTC)[reply]
electrical conductivity
I would like to measure the electrical conductivity of distilled water versus ionized water (for my sister's science fair). How would you do this with a voltmetre? I tried sticking a copper penny to one end of the voltmetre and a zinc nail to the other and putting this into the solution. Would this work? —Preceding unsigned comment added by 70.52.47.166 (talk • contribs) 15:25, 22 February 2009
No, that measures (approximately) the amount of voltage generated (you are creating a battery), not the amount of voltage blocked (the conductivity/resistance). to measure resistance, you need an external source of power and then measure how much of it is lost/blocked by the liquid you are testing. DMacks (talk) 20:36, 22 February 2009 (UTC)[reply]
You are measuring the voltage from a small cell. However since you want resistance, you need to use an Ohmmeter not a voltmeter. Your two electrodes should be the same as each other and not easily reacting. Two copper or two gold electrodes could be the way to go. The conductivity will depend on the geometry of electrodes and temperature, so record these. Graeme Bartlett (talk) 20:43, 22 February 2009 (UTC)[reply]
(ec) I'd say no without knowing what you mean by "ionized water" (Our article "Water ionizer" looks like voodoo baloney to me.). Electrical conductivity is the inverse of electrical resistance (ohms). With your dissimilar metals, you would be demonstrating something else, the galvanic cell. To measure conductivity, you could measure the resistance with the multimeter and divide that into 1, maybe using two long pieces of tubing, one for each water. If you really do have a voltmeter, you could measure the voltage across a resistor in series with a battery and the water, then use Ohm's Law. Two things: distilled water will insulate like glass, and salt water will have practically no resistance (extremely low conductivity and extremely high, respectively). Oh, one more thing: you can't get anything at all in the distilled water, not dust, not your finger, not a drop of tap water, not a probe that has any salt water on it. --Milkbreath (talk) 20:59, 22 February 2009 (UTC)[reply]
I suspect that the original questioner meant Deionized water, since ionized water doesn't make much sense. edit: Unless the purpose is debunking the aforementioned water ionizers. I'd expect the conductivity of distilled and deionized water to be very similar. --NorwegianBluetalk22:02, 22 February 2009 (UTC)[reply]
There are special things called Conductivity cells. From memory, they comprise a cylindrical vessel that has 2 conducting metal rings on the inside surface a small distance apart (could be 1cm but don't quote me). It has 2 terminals on the outside to which you connect an ohmmeter. I think the cell is rigged to give a direct reading of conductivity in Siemens.
Thank you very much. BTW, by ionized water I just meant water with salt in it.
February 23
Red Hot Ice Cube
Here is an interesting found on the internet. Since there are lots of people smarter than me here, I'd like your thoughts. It is supposedly a video of an ice cube glowing red hot due to induction heating. For now I will withhold my thoughts, since I'm not particularly familiar with inductive heating. Thanks :) --Bennybp (talk) 03:56, 23 February 2009 (UTC)[reply]
Induction heating affects metal objects - not ice. I've seen demo's of inductive kitchen ranges where someone can put their hand on the range top with it turned on - and a pot held an inch or so above the hand would still heat up. So I'm not even slightly surprised that the ice doesn't melt. However, the red glow and the flames must be coming from something ELSE inside the inductive loop. SteveBaker (talk) 04:24, 23 February 2009 (UTC)[reply]
I'm surprised the ice didn't melt - if something in the system is getting hot enough to glow bright red and flame, there should be enough heat around to melt the ice. Ice on its own wouldn't melt, but that looks like ice in contact with (or, at least, very close to) metal - the metal would be heated by induction and it would then heat the ice. --Tango (talk) 13:24, 23 February 2009 (UTC)[reply]
Ice doesn't conduct heat very well - so the surface of the block is obviously going to melt - but s-l-o-w-l-y because it's a big block. This is why it's so important to defrost your thanksgiving turkey before you cook it - even though the oven is set at hundreds of degrees the ice inside won't melt quickly enough. In this case, little or none of the induction heaters' energy will be transferred into the ice because induction cookers rely on heating up the metal pot rather than heating the food directly as a microwave oven would. So the ice obviously does melt - but (evidently) slowly enough to not be noticeable over the few seconds it takes an induction heater to get red hot in the video clip. At any rate - production of light due to heat follows a fairly simple relationship between temperature and color. For the ice to be glowing red hot, it would have to be up at several hundred degrees - which would (of course) mean that it would have to be steam. Since it's clearly still ice, it is DEFINITELY not glowing. It's simply refracting the red light from whatever is glowing beneath and off to the sides. There is nothing weird or special going on here - it's just another typical bullshit-faked-science fraud that you see on YouTube all the time. Please - everyone - IGNORE "SCIENCE" VIDEOS ON YOU-TUBE - they are almost all stupid people out to trick you and spread disinformation. SteveBaker (talk) 13:56, 23 February 2009 (UTC)[reply]
Yes, of course the ice isn't glowing red hot, but if it is that close to something that is growing red hot I would expect it to melt faster than that. That kind of bright red hot corresponds to about 1500C, if memory serves - far hotter than an oven (unless you were right up close to the heating element). Is it possible the whole thing is faked and there is just a red LED under there? --Tango (talk) 15:58, 23 February 2009 (UTC)[reply]
Microwave ovens heat by induction, don't they? And they heat nonmetallic objects. Maybe the difference is a matter of frequency. There is a freuency allocation in the rf spectrum for microwave ovens.-— Preceding unsigned comment added by 98.21.104.187 (talk • contribs)
No - microwave ovens use the dielectric effect to heat water - not induction. The dielectric effect doesn't work well on ice either - although it's highly effective on liquid water...which is why 'defrost' mode on your microwave turns the oven on and off repeatedly so it can heat the surface layer of water WITHOUT boiling it - then let that heat melt some of the ice into cold water - then it turns on again to heat that water and thereby slowly melt the ice. So no - that doesn't help the case for this crappy video (Also - where do the flames come from? Water doesn't/cannot-possibly burn!! There MUST be something else in there doing that). SteveBaker (talk) 14:55, 23 February 2009 (UTC)[reply]
I noticed the "burning" too, but thought it might just be a little bit of steam being colored by the red hot "ice." Of course, where does the steam come from? I agree that it is likely some metal in the ice. A one point, it seems like maybe the ice cracked somewhere, letting the steam out.
The demonstration might have been honest enough (showing how inductive heating can heat metal, even through ice) with some cool effect in the ice. But likely the person uploading the video misinterpreted. I agree about the science videos on YouTube - The only thing worse than the videos are the comments on science videos, but I digress --Bennybp (talk) 15:59, 23 February 2009 (UTC)[reply]
Collapsed content not directly related to the question
(Julia: Please don't edit the OP's question - even to add links because it might imply a particular meaning of some terms that the OP did not intend...or suggest to some respondants that the OP already understood those terms or read the articles. Just place the links in your own reply. Thanks! SteveBaker (talk) 13:42, 23 February 2009 (UTC))[reply]
Thanks for your pov Steve, but I did it in good faith, after much consideration as someone who doesn't make a habit of it. It has been done by others and also seemed gentler than something like the reprimands people go in for when homework questions are treated like some kind of affront to the desks. If the links were lost on the OP or totally misleading, then it's my mistake. Julia Rossi (talk) 22:24, 23 February 2009 (UTC)[reply]
I agree it's good to do that and mostly I do, but this time I wanted to vary it. I'm not comfortable with "might imply" which sounds speculative, and prefer not to be corrected on a speculation. Julia Rossi (talk) 22:55, 24 February 2009 (UTC)[reply]
I got told by a stranger in the library today that if my laptop was plugged in, it is better for the battery if it is taken out. Anyway, for those who know more about these things than i do, is this likely to be true? My battery is a recharable Li-Ion (for a samsung Q310) if it makes any difference... thanks81.140.37.58 (talk) 11:23, 23 February 2009 (UTC)[reply]
Essentially the answer is...no. Modern Lithium-ion battery batteries don't have to have the full-drain-recharge cycle that older batteries do, so you don't need to worry about your laptop battery being connected when you are using the mains-supply. Someone will explain the science behind why i'm sure. Maybe try Lithium-ion battery for starters. 194.221.133.226 (talk) 11:58, 23 February 2009 (UTC)[reply]
update: though a link in the article suggests that by removing the battery when using the power-supply it can help keep the battery cool which will reduce the degredation of the battery. 194.221.133.226 (talk) 12:02, 23 February 2009 (UTC)[reply]
My laptop manual similarly suggests that it is better not to leave it on continuous charge. I have ignored this advice, but I notice that the battery capacity has reduced by 70% over 18 months. Could I have extended the battery life by fitting it only when I needed to either use or recharge it? Dbfirs13:18, 23 February 2009 (UTC)[reply]
(That's probably using a SpeedStep technology to slow the processor based on a reading of "low battery voltage" - but if the battery is removed, it is not clear why the sensor would be active, nor why the measured voltage would be isolated from the AC-DC power-supply's standard voltage. Complex systems fail in complex ways. Nimur (talk) 15:58, 23 February 2009 (UTC)[reply]
Edison,Tesla spat cost them a Nobel !!!
Isaac Asimov has calimed that bioth Edison and Tesla were supposed to share the Nobel in 1915 but niether was willing to shar the award with teh other hence it was awarded to Braggs -father and son duo who never came close to the two in terms of their acievement.Is this true?(Ramanathan)
Likely not true. The nobel is usually awarded for novel discoveries, and neither was much of a scientist. True, they both improved existing technologies, but that isn't what the Nobel is normally awarded for. They were successful entrepreneurs and "inventors," but scientists they were not. --Jayron32.talk.contribs12:29, 23 February 2009 (UTC)[reply]
Actually, the physics prize is also awarded for technical work, and was in particular during the early years (e.g. Gustaf Dalén). And Tesla did in fact do important theoretical work. --Pykk (talk) 12:36, 23 February 2009 (UTC)[reply]
This is mentioned in Nobel Prize controversies. However, I spot several issues here. Number one is that the prize winners are simply never consulted about sharing an award, or indeed consulted at all, before they win the Nobel. The second issue is that sources seem to be contemporary rumors in the press. That's a bad source. The Nobel committee work is kept secret for 30 years (IIRC), so if Tesla and Edison were under real consideration, it'd be relatively easy to come up with real documentation of it. Also, it's worth noting that Tesla and Edison were big celebrities in the USA - whereas the Nobel committee in Sweden would be more aware of European innovators in the area, such as Mikhail Dolivo-Dobrovolsky and their own Jonas Wenström, both of whom independently developed three-phase AC systems within months of Tesla's work. Finally, Bragg was indeed deserving of the prize. --Pykk (talk) 12:34, 23 February 2009 (UTC)[reply]
Lest you underestimate the value of the Braggs' prize, note that it was for a technique that has been of immense value for physics, chemistry, and biology since then (the discovery of the structure of DNA hinged on it as well). Whether you think Tesla/Edison should have gotten a prize does not distract from the importance of the Braggs' work. --98.217.14.211 (talk) 13:52, 23 February 2009 (UTC)[reply]
The 1915 Nobel prize being offered to Tesla and Edison claim has been debunked by someone with access to all the Nobel Committee files. The talk page archives for the Nikola Tesla article say: Talk:Nikola Tesla/Archive 6#Nobel claims
"Another verifiable site for the initial incorrect report is the New York Times, Nov 6, 1915, p1: "Edison and Tesla to get Nobel Prizes" which based their statement on the Copenhagen correspondent of the Daily Telegraph. Also see Nov 7, 1915, p12, "Tesla's discovery Nobel prize winner". The article said "Nikola Tesla, who, with Thomas Edison is to share the Nobel Prize in physics, according to a dispatch from London, said last night he had not yet been officially notified of the honor. His only information on the matter was the dispatch in the New York Times." Tesla thought the honor was for the transmission of energy without wires. He said he thought Edison was worthy of a dozen Nobel Prizes. He had often expressed his friendship with and admiration for Edison, and gave no hint he would refuse the honor if Edison was also getting it. The reported antipathy toward Edison only showed up when he was elderly. Finally Dec 28, 1915, p83 the NY Times reported that the initial report was incorrect. It had also given an incorrect report for the person to receive the chemistry award, further disproving the claim that Tesal refused the prize because Edison was also getting one. Also disproof of any great antipathy between them causing them to refuse the 1915 Nobel Prize is that in 1916 Tesla accepted the Edison Medal'For meritorious achievement in his early original work in polyphase and high-frequency electrical currents.' This often repeated claim that Tesla refused a Nobel prize needs something like a rejection letter from the Nobel files, or a memoir by someone involved with the Nobel award, or papers from Tesla's files. In other words, something more than someone writing a book or creating a webpage and stating it is so without a good source. Edison 23:48, 17 July 2006 (UTC)
There is not much room for controversy. Seifer in "Wizard" pp378-380 has obtained detailed info from the Nobel people. Tesla never received a Nobel nomination in 1915, so he did not refuse it. Neither did Edison. Out of 38 nominations for the prize in physics, Edison received one and Tesla zero. The winners were the Braggs, father and son. There was an erroneous press report as listed above. Tesla also received one bid out of 38 in 1937, again not enough for him to win the prize. No nomination, no controversy, other than perhaps that he might have deserved one.I am removing refrence to the 1915 Nobel Prize and Tesla.Edison 22:56, 22 July 2006 (UTC).
To the original poster: I would be very surprised if Isaac Asimov made any such claim. Where did you see this? --Anonymous, 05:29 UTC, February 24, 2009.
Manual gear
I drive amanual gear car ,,, it's annoying how you should reach that balance
between the clutch and fuel at start of movment , specially at crowded streets,
i'am wondering , was it to difficult for them to make a medium gear which can
transfer the power from the engine to the gear to the tires smoothly at movement
starting without that precious driving actions ... its Twinty-one century ,,, ???
Smooth transfer of power by manual gear-change improves with practice. Perhaps you would prefer a car with automatic gear change, where twenty-first century technology helps you to transfer power smoothly. I recall a continuous gear on some Daf vehicles in the mid-twentieth century which achieved the smooth transfer using a belt drive without separate gears, but I presume it had significant disadvantages. Does anyone know what happened to that technology? Dbfirs13:14, 23 February 2009 (UTC)[reply]
The problem with what the OP is requesting is that a 'clutch-less' transmission relies on a kind of 'sloppy' coupling between engine and gears or between gears and drive-shaft. In an automatic (or semi-auto) gearbox, that's typically handled with a 'fluid clutch'. The problem with fluid clutches is that they are the precisely the reason you didn't want a fully automatic in the first place - they take a while to 'catch up' and that means that you have less acceleration and you waste fuel compared to a manual transmission being driven by a competent human.
Going to semi-automatic doesn't help. Essentially, a semi-automatic transmission is just a fully automatic transmission where you give hints to the on-board computer about when you'd like it to shift. My wife's MINI Cooper has that and if you try to over-rev the engine or stall out or lug the engine due to too few revs, the computer just quietly takes back control from the driver and sneaks back into fully-automatic until you get it right! Semi-automatic is the worst of both worlds in that a poor human driver can persuade the car to be in the wrong gear for much of the time - yet you still suffer all of the losses of a fluid clutch.
The idea that I love is currently (I believe) only available on the MINI Cooper - but for some entirely arbitrary and stupid legal reason - not in the USA. The UK version of the MINI turns off the engine when you come to a stop. When you start to move off the line, it uses the starter motor to get the car rolling again - and doesn't restart the engine unless you stomp on the gas - or until you are going faster than about 10mph (or if the battery voltage starts to get low). This means in annoyingly slow stop-start traffic, the car almost becomes an electric car - turning back into a gas-powered vehicle only once you need the speed and/or acceleration. That's such a simple trick - requiring almost zero additional parts in the car (it's mostly a software trick in the engine management computer) - I can't believe that all modern small cars don't have that.
Sadly - in other cases - the alternatives are to become better 'in tune' with your car so that you can get the clutch control just right - or to give up and drive an automatic.
A semi-automatic does have some advantages over a fully-automatic - in particular, you can anticipate the need to change gear (just before you pull out to overtake, say). You don't get the fuel savings, though, you're right. --Tango (talk) 13:53, 23 February 2009 (UTC)[reply]
Yes - I agree. And in really top-notch cars the paddle-shifters can shift gears faster than you could in a stick-shift car, so there are some benefits to be had there in terms of not using engine power to uselessly spin the engine in the brief moment when you have the clutch pedal on the floor. I haven't driven semi-automatics much - but in playing around with my wife's new MINI over the weekend, I found that putting it in full automatic mode and just hitting the paddle shifter to drop a gear when you want to overtake or something was a pretty neat compromise. It has three modes - full automatic (with paddle shifter 'override'), semi-automatic-for-morons (where you shift with the paddles - but if you try to push the revs too high or too low it takes over and shifts for you) and semi-automatic-for-real-men (where you shift with the paddles and the car does what you tell it no matter what). But I'm a stick-shift enthusiast - my car is manual. SteveBaker (talk) 14:47, 23 February 2009 (UTC)[reply]
On my first driving lesson the instructor took me to an up-going hill. He made me hold the car stationary on the hill without using brakes, just sliding the clutch. At first I was clumsy, either over-revving the engine or stalling it. Finally I mastered the "feel" of the clutch and could even drift the car up or down at will. After that practice, smooth start-ups become instinctive and you have better control than any automatic transmission. But start a different car, such as a hired car, and it takes a little while to feel out the unfamiliar clutch.
Yes - you are quite likely to wear out the clutch while you're learning. If you can find a driving instructor with a stick-shift car who'll give you a couple of lessons - that's the best way to learn. I haven't seen stick-shift rental cars for a very long time - but if you can find one - that's better still. SteveBaker (talk) 22:36, 23 February 2009 (UTC)[reply]
The reason few cars have SteveBaker's electric start aid is that it would quickly wear out a conventional starter coupling gear and motor. The starting cycle is predetermined so I wonder how well it works in all conditions of hills and battery charge. These problems are worse for heavier cars and/or larger engines that need more torque to crank.Cuddlyable3 (talk) 19:06, 23 February 2009 (UTC)[reply]
It's not 'mine' - it's BMW's - and it's not hypothetical - it actually exists in real production cars. Of course the MINI is indeed one of the smaller/lighter cars available in the USA - but it's pretty normal by European standards. But bigger cars have bigger engines and therefore bigger startermotors and bigger gears - so there need not be a problem for larger vehicles. I suspect the reason most other cars don't have it is that without the MINI's Gasoline direct injection gizmo there is a risk of flooding the engine or something. The amount of gas you save on in-town driving by doing this is pretty spectacular - so even if a slightly meatier starter and coupling gear is required - it's still a pretty good deal. I presume the car can measure whether it's on a slope and whether the battery is getting low - and in those cases, it can simply start the engine as a number of cars that turn the engine off while idling do. I'm pretty sure the MINI knows when it's stationary on a hill because it knows to hold the foot-brake on for three seconds after you take your foot off of it so you can do easy hill starts without messing around with the hand-brake. Sensors for things like tilt and rotation are becoming very cheap these days - compared to tens of thousands of dollars for the car - a $5 sensor is nothing. The MINI already has yaw rate sensors and all manner of other stuff for figuring out what's going on. SteveBaker (talk) 22:36, 23 February 2009 (UTC)[reply]
I don't know if (or why) that's true in Europe in general - but there is a REALLY good reason why it is so in the UK. In the UK, there are two different drivers licenses - one that permits you to drive any kind of car - and a lesser license that only allows you to drive automatics. In order to get the 'any-car' license, you have to pass your driver's test in a stick-shift car. Since hardly anyone wants to be limited as to what they could drive in the future - or to have to take a second drivers test later in life, nearly everyone learns to drive stick and passes their test in a stick-shift car. Almost the only people who have the automatic-only license are disabled people who for whatever reason are physically incapable of driving stick. I don't think I know anyone in the UK who has the automatic-only license. Since new drivers are generally a little nervous, the first car they buy tends to be a stick-shift car because that's what they are used to. This then becomes the habit of a lifetime. That in turn means that there is a much higher demand to manual transmission cars - there are more manual transmission cars on the used car market and so forth. Because car manufacturers have to go to some extra trouble to make cars with the steering wheel on the right hand side for the UK market - they make relatively few automatics - and the price of automatics is generally considerably higher than manuals. This feeds back still more because now you have a community of drivers who almost all are quite happy driving stick - and a car market where automatics are a lot more costly. Another factor is that gasoline prices in the UK have always been VASTLY higher than in (say) the USA - since automatics get worse MPG than a properly driven manual gearbox car, this is further pressure to drive stick. SteveBaker (talk) 13:14, 24 February 2009 (UTC)[reply]
Not in Europe obviously but NZ also has quite a lot of manuals. In NZ you can only drive an automatic if you pass the test under one while you have your probationary license. But once you have a full license you can drive either car no matter what you pass your full license test under. A bigger factor may be that NZ's car fleet is very old with an extensive used car market (many coming from Japan, Singapore and other countries with strict regulations and probably left hand drive where people don't keep their cars long). Manual cars tend to last longer and are cheap to maintain with fewer things that can go wrong. Of course we're ultimately also somewhat limited by what is available on the world market. Nil Einne (talk) 14:20, 24 February 2009 (UTC)[reply]
increase of relative mass
I have understood the time dilation and length contraction in special relativity. But i don't understand the mass increase.can someone explain why the mass of a body increases relatively when it is moving and why only by the formula in special theory of relativity? i am a ninth grade student. please explain accordingly.--harish (talk) 15:34, 23 February 2009 (UTC)[reply]
Short answer: When an object is moving it has kinetic energy, energy and mass are just different ways of looking at the same thing (E=mc2), so when you increase the energy you increase the mass. (It's worth noting, most of time when we talk about mass we mean "rest mass", which is the mass when the object isn't moving - that is constant. The concept of "relativistic mass" isn't actually very useful when doing calculations, etc., so it isn't used much.) --Tango (talk) 15:53, 23 February 2009 (UTC)[reply]
I have a feeling that you are referring to the common note that a person cannot reach the speed of light because as energy is added to increase speed, the mass increases. More energy is needed to make it go faster because there is more mass. If that is what you are referring to, the energy itself is adding to the mass based on e=mc2, which can be rewritten as m=e/c2. The mass increase for a little energy is very small, but when you are talking about the amount of energy required to get something up to the speed of light, the mass increase becomes huge. -- kainaw™15:57, 23 February 2009 (UTC)[reply]
There really isn't much special to say - if you have gotten your head around time and length changes due to fast motion with respect to some observer - then just apply the exact same principles to the object's mass...the equations are the same, the cause is the same, the sheer cosmic wierdness of it all is exactly the same. When an object moves rapidly past some observer, that observer judges the mass of the object to have increased. The closer the object gets to the speed of light, the more its' mass increases...just as time and length change when that happens. If you have your head around length and time changing - mass should be easy to imagine! SteveBaker (talk) 16:34, 23 February 2009 (UTC)[reply]
As Tango said, physicists do not like the concept of a varying mass. That is because it does not add anything to our understanding. Length and time changing is enough to explain everything, including the speed limit of the speed of light. You do not actually need a varying mass to explain that! Essentially, "relativistic mass" is just short-hand for E/c2. The really important concept of mass is rest mass, which is E/c2 for a particle that is at rest. Still, for a lay person it is apparently easier to accept a varying mass, and it's probably easier to "understand" the speed limit as being due to increasing inertia than to the structure of Minkowski space-time, and therefore it is probably okay to use the concept in popular presentations. --Wrongfilter (talk) 17:55, 23 February 2009 (UTC)[reply]
wood - properties
is wood an isotropic solid. please qualify your answer.
"please qualify your answer" sounds like something from a homework question, we won't do your homework for you. Do you have a textbook that you can look up what "isotropic" means? I think once you understand the definition the answer should be fairly obvious (if you've ever done any woodwork, at least!) --Tango (talk) 15:53, 23 February 2009 (UTC)[reply]
Please do your own homework.
Welcome to the Wikipedia Help desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems.
Please attempt to solve the problem yourself first. You can search Wikipedia or search the Web. If you need help with a specific part of your homework, the Reference desk can help you grasp the concept. Do not ask knowledge questions here, just those about using Wikipedia. —ScheinwerfermannT·C16:24, 23 February 2009 (UTC)[reply]
Which Pre-Columbian diseases spread from America to the Old World, from the 15th Century and on? I know Syphilis is assumed to have spread from America to Europe ([36]), but other subspecies of Treponema pallidum already existed in Asia and Africa. Which pathogens were endemic to America before they spread to the rest of the world? Thanks, ליאור (talk) 17:39, 23 February 2009 (UTC)[reply]
Well, the H1N1 strain causing the Spanish Flu is just a subtype of a globally common virus, that happenned to mutate in Kansas. And potatoes were cultivated in the Andes, so one clearly needs potatoes to have potato blight. Is there a pathogen that was once only found in America and is now also found in Europe\Africa\Asia\Australia, affecting local hosts? ליאור (talk) 20:11, 23 February 2009 (UTC)[reply]
Tobacco smoking originated in the Americas and has probably killed more Europeans than all the other health risks originating there. Edison (talk) 20:15, 23 February 2009 (UTC)[reply]
"... Irradiated the world's supply of steel"? Clarify?
I was reading the article on the Scuttling of the German fleet in Scapa Flow, and came across this line: "Minor salvage is still carried out to recover small pieces of steel that can be used in radiation sensitive devices, such as Geiger counters, as the ships sank before nuclear weapons and tests irradiated the world's supply of steel." Now, I can understand that atmospheric tests would leave residual radiation, even very small amounts, but wouldn't steel that has yet to be mined be similarly clean? Or is it that the steel in the ground has been irradiated, but the steel under Scapa Flow is somehow radiation free? Can someone elaborate on the meaning of the above quote? Thanks — Preceding unsigned comment added by 38.118.48.5 (talk • contribs)
That seems odd to me. Being irradiated shouldn't make the steel radioactive. It might have radioactive substances on the surface that need to be cleaned off, but that isn't too difficult. Even if it has been, all steel is going to be slightly radioactive since it contains carbon, some of which will be carbon-14, which is radioactive (only slightly, but still). That means a Geiger counter is always going to need to be calibrated to take into account the radiation of the counter itself, so you just have to calibrated it differently if it is made with irradiated steel. And even that seems pointless since background radiation from everything from uranium in the bedrock to people's smoke detectors probably results in a significantly higher order of error. --Tango (talk) 19:37, 23 February 2009 (UTC)[reply]
Iron ore mining does not take place in a "clean room," so any surface or subsurface dust naturally gets mixed in and is tin the resulting steel. Back in the late 1950's and early 1960's there was atmospheric nuke weapon testing by the various nuclear powers, and children were warned not to eat snow because of the Strontium 90. There was also concern about radioactivity in milk. There was no atomic bomb detonation before 1945, so the older steel has less radiation in it than post 1945 steel. When scientists want to use steel to shield nuclear testing instruments, there is apparently a meaningful difference in the radiation levels of the two vintages of steel. In i=other words, the modern level may be low so far as health risks are concerned, but they want the lowest possible level. Edison (talk) 20:13, 23 February 2009 (UTC)[reply]
In the production of steel, oxygen produced from air is bubbled through molten iron. That removes impurities by oxidizing them. The oxides appear as slag on the surface of the molten metal, or are passed off as a gas. It is possible that strontium 90 left in the oxygen, and other nuclear-explosion products from the air, remain in the molten metal. One of the chief materials removed from the iron ore is carbon. But perhaps some of the carbon 14 from the air also remains in the molten metal. The OP will get a good homework grade for this. – GlowWorm.
There's no need to do expensive diving to get old steel. Structural steel (I beans, channel iron) from old buildings and bridges will do as well. – GlowWorm.
One would think if that were the case then nobody would bother with the diving. Either the divers and their customers are idiots or it's harder than RefDeskers think. --98.217.14.211 (talk) 00:28, 24 February 2009 (UTC)[reply]
If anyone finds out, let me know (I'm personally curious). T'only ref I saw supporting this contention was an offline one. arimareiji (talk)
Is it not possible that steel present on the surface of the earth (structural) collects enough residual radiation over time to make it less useful, and that old steel wouldn't have been subject to such levels of residual radiation at the time, and is thus "cleaner"? Diving for steel is certainly more cost effective than mining, so there must be something less desirable about modern scrap (used) steel.
Perhaps the problem with , say steel columns and rebar from 1944 skyscrapers its that the steel cannot be machined down to make the required shielding members for nuclear instruments, while 16 inch thich armor can be used as raw materials and cut to shape and used more economically. Still, one would think that pre 1945 steel columns and beams from demolished buildings could be ground free of surface contamination, then melted and used to cast the required shielding members. Edison (talk) 02:38, 24 February 2009 (UTC)[reply]
Perhaps induced radioactivity is involved. This might be produced in the iron in the steel, or in some other element in the steel. (There are various kinds of steel, produced by adding other elements to it.) The induced radioactivity may be produced by nuclear-explosion products in the air, and the radioactivity may not be able to penetrate depths of the ocean. (How deep is Scapa Flow? The German ships there are popular diving sites, which would indicate the depth.) But if the induced radioactivity is only at the surface of old structural steel, it could be ground off, sandblasted off, or milled off. – GlowWorm. —Preceding unsigned comment added by 98.21.104.187 (talk) 06:00, 24 February 2009 (UTC)[reply]
How can I depigment hair extensions??
I am looking for a way to depigment my hair extensions without harmful bleaching. Is there some agent I could soak the hair in for a period of time (even days) to slowly remove pigment from the hair extensions?? —Preceding unsigned comment added by 76.110.2.85 (talk • contribs) 19:34, 23 February 2009
Not only that. See Artificial hair integrations. We'd also need to know how the extensions were attached. Your hairdresser is probably the better source for information. They should have the manufacturer's directions for your product. Your goal of lightening your extensions while protecting them may not be realistic though. AFAIK most/all decolorizing agents are oxidative. That damages hair by definition. The best you could probably hope for is to find a product with a conditioner that will coat some of the damage. Google coughed up this patent [37]. 76.97.245.5 (talk) 22:55, 23 February 2009 (UTC)[reply]
February 24
Measuring digits
Is there an easy way to measure the length of ones digits accurately? My left thumb is noticably (to me, not so much to other people) stumpier than my right, and I think it's because of the length of my first and second digit, as opposed to the position/length of the nail (which is also short, I believe as a result of the short digits), but I can't figure out a way to measure the lengths accurately to within 1mm or so, because I don't have any expensive measuring equipment. Any ideas? Thanks! 219.102.220.90 (talk) 00:40, 24 February 2009 (UTC)[reply]
A clear plastic tube, such as a coin tube, should do the trick. Insert your finger in as far as possible and mark the depth. Repeat and compare. -- Tcncv (talk) 01:21, 24 February 2009 (UTC)[reply]
The other option is tracing round your hands onto a piece of paper, then you can measure with a ruler. You would need to trace very carefully, though - keep the pencil vertical the whole time. --Tango (talk) 15:06, 24 February 2009 (UTC)[reply]
One biometric security device for confirming identity uses the lengths of the fingers. It was pretty good at distinguishing the hand of the person being checked from other random hands, and far faster than fingerprint or retinal scan. I believe some early ones used pegs which fit between the fingers and position sensors for the length, but now they seem to use electrical conduction. See [38]. A flatplate scanner can also be used [39]. Edison (talk) 00:02, 25 February 2009 (UTC)[reply]
The atmosphere on comet Lulin
This article on the comet states: Lulin has a greenish cast because sunlight illuminates two gases — cyanogen and diatomic carbon — in its Jupiter-sized atmosphere.
Am I supposed to believe that the comet has a big enough gravity field to hold gas at a range equivalent to the radius of Jupiter?? I can't find a source that states the estimated size of the comet, but I find it hard to believe it has enough mass to support such a size. 219.102.220.90 (talk) 01:39, 24 February 2009 (UTC)[reply]
Unfortunately, that news article is correctly quoting a NASA press release. In other NASA press releases, it is called a coma. In the one being quoted, it is called an atmosphere. -- kainaw™15:08, 24 February 2009 (UTC)[reply]
Well I guess they can be arbitrarily large/long can't they, assuming gas is being pumped out constantly. Either way that settles it, thanks everyone! 219.102.220.90 (talk) 00:15, 25 February 2009 (UTC)[reply]
Yes, it really depends on how you define the edge. There is no clear end to the coma, it just gets thinner and thinner. Of course, similarly, there is no clear end to Jupiter or the Sun, so as long as you use the same definition you can get meaningful comparisons. --Tango (talk) 14:23, 25 February 2009 (UTC)[reply]
Requirements for being published in Science Mag: Policy Forum
What are the requirements for having a piece published in the "Policy Forum" section of Science (journal)? The WP article says that research articles are peer reviewed, but what about the Policy Forum section? What is the scope of this section? Thanks, NJGW (talk) 02:06, 24 February 2009 (UTC)[reply]
Have you tried contacting them directly? Their website is linked from our article, and if you click the "feedback" link on their homepage, they have a means to contact the editors and ask a question directly of them. --Jayron32.talk.contribs02:10, 24 February 2009 (UTC)[reply]
The "Informational URL" listed in our article points to the "Information for Authors" webpage, from which you can find information about the submission process, selection criteria, etc. DMacks (talk) 02:13, 24 February 2009 (UTC)[reply]
Editorial articles (signed or unsigned) for science journals are generally not peer-reviewed. (They are, as the name suggests, provided at the pleasure of the editor.) --98.217.14.211 (talk) 02:14, 24 February 2009 (UTC) nevermind, the Policy Forum articles don't seem to be editorials. I suspect they are peer-reviewed in one way or another, based on the way they are presented (identical to the research articles). --98.217.14.211 (talk) 02:17, 24 February 2009 (UTC)[reply]
Thanks for the tips. All that the info for authors states is that the "broadly accessible commentary... presents issues related to the intersections between science and society that have policy implications." NJGW (talk) 02:46, 24 February 2009 (UTC)[reply]
The authors'-info page has a link to "Contributors FAQ", on which "What kinds of manuscripts does Science consider?" which notes: "A variety of material under the general heading of Commentary -- including Editorials, Book Reviews, Education Forums, Policy Forums, Perspectives, and Reviews -- is usually solicited by Science editors, although on occasion the editors will consider unsolicited manuscripts of these types." So it's not clear there whether it's peer-reviewed, but it's definitely not open-submission. DMacks (talk) 02:59, 24 February 2009 (UTC)[reply]
Amoebas and White Blood Cells
We all know that amoebas and white blood cells send out pseudopodia to engulf their prey or pathogens (respectively). Here's a picture of a mouse macrophage sending out pseudopodia to engulf two bacteria.
My question is: without a nervous system, eyes, or any kind of control system, how do amoebas and white blood cells have the coordination to know how to engulf something, much less reach out long "arms" like in that picture? To my understanding, cells are basically just little bubbles floating around, and it boggles my mind to think they can do such coordinated tasks. Inasilentway (talk) 02:43, 24 February 2009 (UTC)[reply]
(e/c) I hope you don't mind, but I reduced the size of your picture to assist those people viewing this page with restricted bandwidth. A basic answer to your question can be found at Pseudopod. Unicellular locomotion is a fascinating subject, and involves a co-ordinated process of protein interactions at the lamellipodium. It includes microfilamental structural elements and lots of other proteins (such as the Rho family of small Ras-related GTPases) that regulate the actinpolymerization/depolymerization. This process essentially creates a cytoskeletal "treadmill" on which the cell can extend processes or move itself.
As mentioned, macrophage has receptors that bind to bacterial surface. Bacterial surface has unique signatures, or common molecular patterns, that the macrophage are able to recognize. Also, when there's an infection, we produce antibodies (proteins that bind to the invaders). The antibody-bacteria complexes are like extra glue, making it easier for macrophages to attach and eat up the bacteria. The receptor make-up of the macrophage is very complex as to be able to recognize invaders. Check out http://www.ncbi.nlm.nih.gov/books/bv.fcgi?highlight=macrophage&rid=imm.figgrp.157199.76.164.202 (talk) 03:39, 25 February 2009 (UTC)[reply]
Photosynthesis
if u were to feed a plant sugar through the roots, would the plant need leavs(or photosynthesis)?
Only if you would consider fungi to be plants and their mycelium to be roots. They are generally considered to be different. For "ordinary plants there's a problem because the sugar is transported in the Phloem from the leaves to the roots, the xylem transports salts and water from the roots to the leaves. AFAIK it doesn't work in reverse.--76.97.245.5 (talk) 08:01, 24 February 2009 (UTC)[reply]
would low levels of radiaton from a red laser pointer help of harm light loving plants?
Your Question is quite difficult to understand, but as far as i know, a laser Pointer does not produce what is commonly called radiation (its actually ionizing radiation). Also the wavelength of red light (around 700 nm) is not absorbed by either of the two chlorophylls so it probably wouldn't even give the plant energy... But what do you mean with "help of harm?"--91.6.42.166 (talk) 08:51, 24 February 2009 (UTC)[reply]
I would be very grateful if somebody could explain the terms latent index and manifest index for me in the following sentence that I found in an article:
"Factors represented by circles (e.g., early childhood adversity) constitute latent indexes of primary theoretical constructs (i.e, they are respectively composed of correlated but conceptually distinct elements). Genetic factors constitute a manifest index and are therefore represented by a box (see Bollen, 1989, for conventions relating to path model representation)."
By the way, Bollen 1989 is a book that I haven't read - and do not wish to read :) Lova Falk (talk) 09:06, 24 February 2009 (UTC)[reply]
Ripen my mango
Does anyone know how to ripen a mango? Or do I just have to leave it and wait? My inclination would be to put it on a sunny windowsill, but Moseley is cold and grey at this time of year.--Shantavira|feed me09:50, 24 February 2009 (UTC)[reply]
Ethylene might work. They build countermeasures into fruit containers and warehouses so the fruit will stay fresh longer. Some fruit emit it naturally, so all you have to do is toss one of those into a plastic bag with your mango. 76.97.245.5 (talk) 11:08, 24 February 2009 (UTC)[reply]
You don't really need a bag at all, unless you are in a hurry. Just being in the same fruit bowl as a bunch of ripe bananas will do the job. --Tango (talk) 00:18, 25 February 2009 (UTC)[reply]
adrenal and gonadal androgen
Do I understand correctly from the article on androgens that there exist adrenal androgens, produced in the adrenal gland, and gonadal androgens, produced in the testes?
And, next question, do females produce just as much adrenal androgens as males? Lova Falk (talk) 10:06, 24 February 2009 (UTC)[reply]
You understand correctly. The adrenal glands produce three main types of hormones: glucocorticoids that have a role in the stress response and glucose homeostasis, mineralocorticoids that help regulate the salt/water balance, and androgens that are involved in the process of adrenarche (i.e. pre-puberty where pubic hair and body odor begin to develop). I don't know if there are(changing my wording... thanks, 159.14.241.253) specifically what the quantified differences in adrenal androgen output are between females and males, but during puberty the effects are dominated by gonadal production of testosterone in males (testes)and estrogen in females (ovaries). Abnormal adrenal steroid production is a key pathophysiologic mechanism in congenital adrenal hyperplasia. --- Medical geneticist (talk) 15:25, 24 February 2009 (UTC)[reply]
Weizman and Kalam are not scientists, but engineers. Very good engineers, no doubt, but not scientists. I found one, maybe, head-of-state scientist in Wikipedia, Stanislau Shushkevich, "first leader and head of state of independent Belarus after the dissolution of the Soviet Union". What the article means by "scientist" is impossible to tell, since it gives no examples of any discoveries of his, and the references are in Russian. --Milkbreath (talk) 13:14, 24 February 2009 (UTC)[reply]
Adding to the list of female chemists, on a more unpleasant note, Elena Ceauşescu was a polymer chemist. She was only deputy Prime Minister, but was often rumored to have been the brains behind her husband. --Pykk (talk) 18:49, 24 February 2009 (UTC)[reply]
Right, but as the "father of industrial fermentation", I figured Weizmann for a chemical engineer. "Chemist" doesn't necessarily mean "scientist", but the line is blurry, so he can come in for my money. --Milkbreath (talk) 00:34, 25 February 2009 (UTC)[reply]
a pill i found
a friend of mine dropped a round white tablet in my car and now i'm curious what it is. it has a few numbers on it on two rows. 44 and 438 on the second row. —Preceding unsigned comment added by 98.210.135.91 (talk) 13:19, 24 February 2009 (UTC)[reply]
Hi all, I am currently doing a history assignment. I am supposed to gather accounts of people living from the previous generations to give an account of Singapore during their time and suggest the history od modern singapore. Please give me your account of Singapore and how it was like. Thank you very much.(you could help me by helping me find accounts of other people). —Preceding unsigned comment added by Invisiblebug590 (talk • contribs) 13:34, 24 February 2009 (UTC)[reply]
That's not really the kind of references we can help with. I can point you to History of Singapore if you want the facts, but if you want personal accounts you will have to find them yourself, I'm afraid. --Tango (talk) 14:44, 24 February 2009 (UTC)[reply]
I'm having trouble understanding waves. I find wave equation explainations insufficient. I can see how rates of speed in circular motion can translate to expressed different kinds/shapes of waves and appreciate the descriptive graph/animations on the wikipedia pages for waves and trigonometry. But I don't believe it sufficiently explains why concepts of trigonometry like sin,cos which a beginner like myself associates with triangles are brought into describing waves, there is a connection gap. Can anyone elaborate on how sin, sohcahtoa, e.g. opposites divided by hypotenuse (one never sees this process taking place and which parts they correspond to in the waves) relate/interact to aspects of the waves. Thanks in advance for any insight here. —Preceding unsigned comment added by Dbjohn (talk • contribs) 15:15, 24 February 2009 (UTC)[reply]
You associate trigonometry with geometric shapes like triangles, but that mathematics can be applied to a very large set of geometric and other conceptual problems. In many ways, you can think of a wave equation as "some parameter" (such as pressure), traversing around unit-circle. This means that it is repetitive, cyclic, and can be described as a "phase" (angle) parameter and a strength (magnitude) parameter. The conceptual leap from physical space to phase space is a big one - when "pressure" goes through an angle from 0 to 360°, the pressure isn't "moving" anywhere (although the wave may actually propagate as a result). The wave equation, for whichever physical situation you are considering, will describe the relationship between the phase of the parameter and its spatial coordinate (position) as a function of time. Let me know if you need some more clarification; this is conceptually a big leap, but after you can bridge the ideas, things will seem much simpler. Nimur (talk) 17:59, 24 February 2009 (UTC)[reply]
I suggest you look at these two figures[41][42]. In the second figure only the lengths marked sin and cos are of interest. There you have your right triangle where AO is the hypotenuse. Think of the hypotenuse continually rotating anticlockwise so angle theta keeps increasing. The sin and cos values vary over time (angle) as shown in the first figure. In practical terms, either could be the voltage wave produced by a rotating generator. Cuddlyable3 (talk) 18:39, 24 February 2009 (UTC)[reply]
Band-stop filters
I am considering using a digital filter to remove electrical background noise from facial surface EMG data. I have seen a number of different band-stop ranges in the literature to remove 60 Hz (I am in the USA), but there is no particular theoretical justification I can find regarding why one would use a particular range (for example, 59-61 Hz as opposed to 58-62 Hz). Is this an arbitrary decision? Does anyone here know what the standard deviation for 60 Hz mains hum is? Thanks, PotionsMasterSnape (talk) 15:37, 24 February 2009 (UTC)[reply]
Two things come to mind: There might be times when you'll be getting power from a generator that won't have such a tight frequency spec. I looked online, and the specs I saw just said "60 Hz". The lack of an expressed tolerance bodes ill for their accuracy, I think. The other thing might be only in my fevered brain, but I imagine it's possible that line hum could feed some low-Q stray resonance in a circuit close to 60 Hz. --Milkbreath (talk) 16:13, 24 February 2009 (UTC)[reply]
Our article on Utility frequency notes that utilities try to keep quite close to the nominal frequency so that synchronous clocks only deviate a few seconds from actual time. That article says that utilityes may start automatic load shedding when the frequecy drops as much as, say .5 Hz from a nominal 60 Hz. to prevent a widespread blackout due to inadequate generation online to serve the connected load. So +/- .5 Hz should cover extreme frequency deviations, and a somewhat tighter band (+/- .1 Hz?) should cover normal day to day deviations, outside of system instability or overloads. If the power is provided by stand-alone generators, then the frequency deviation could be much wider, perhaps several Hz.Outlet power or even the power on the utility feeders also contains harmonic multiples of the mains frequency, the amount varying greatly depending on transformer balancing and the loads customers have connected. Edison (talk) 17:32, 24 February 2009 (UTC)[reply]
I've spent a lot of time filtering out power-line harmonics (and going to great lengths to avoid power-lines in the first place). Your particular measurements will have to dictate your removal method for power-line harmonics (have you looked at an FFT of your recording? You can probably see the 60Hz hum spike). In many cases, a narrow notch-filter works well; sometimes, I've used noise-fillers or statistical estimators to interpolate in the frequency or time domains to smooth out the final signal. The power-line hum can vary by a large amount from place to place; its mean frequency might not be exactly on 60 Hz; its amplitude fluctuates by extreme amounts (I have seen 100 dB range) based on the actual amount of current in the lines and how well your receiver couples in to it at any given instant). I have seen bandwidths of more than 20Hz on pathological datasets. It will largely be arbitrary; you can make an intelligent nonlinear filter or estimator to automate the estimation of the filter parameters, depending on your needs. (E.g. measure the original signal's frequency spectrum; estimate the f3db width of the spike closest to 60 Hz, and make a new notch-filter based on those). Nimur (talk) 18:06, 24 February 2009 (UTC)[reply]
You may also want to remove harmonics of the 60Hz such as 120 or 180Hz which are also likely to be present, especially if you have mains power supplies nearby. And if you want your system to work in other countries you may want to stop out 50Hz instead. If you make a very narrow bandstop filter it will have a high Q, and a long delay, so as to be more a problem for real time results. You should also look at the side effect on your signals, try to minimize the phase shift near the stop point. This can happen with the Gaussian filter but there will be a trade off with the shape of the stop band. Graeme Bartlett (talk) 22:30, 24 February 2009 (UTC)[reply]
Conservation of mass
The law of conservation of mass states that the sum total of mass in a system remains constant no matter what, right? Visualize the following situation:
A couple (male and female) of animals (cows, dogs, goats, or even humans) is kept in a closed chamber for a year. The chamber is stocked with enough food to last them for quite a while. After a year, the food reserve is finished, and the female has borne a child. Does the law of conservation of mass apply here?? The food is finished, and there is addition of a third organism. How can the sum total of all the masses still be the same?? Thanks in advance. 117.194.230.71 (talk) 15:58, 24 February 2009 (UTC)[reply]
Enough food, water, and air to last a year would be a much larger amount of mass than most people would imagine. It would be many, many times the size of the third organism - the vast majority would be actually converted to waste solid, liquid, and gas. arimareiji (talk) 16:05, 24 February 2009 (UTC)[reply]
And don't forget heat, which hasn't really been discussed in the original scenario. Remember that conservation of mass applies to closed systems, meaning no heat in or out of the chamber, which will introduce all sorts of issues. ArakunemTalk16:11, 24 February 2009 (UTC)[reply]
(EC) Yes. Everything would tally up, assuming you have a way of totalling ALL of the energy in this closed system (i.e. the masses of the people/goats/pink mongooses and all the food, plus the thermal energy "waste", because E=mc²), and I'm assuming you mean properly "closed", as in, say, a hermetically sealed chamber.--Rixxin (talk) 16:09, 24 February 2009 (UTC)[reply]
The heat released from the system is NOT converted to or from mass. It comes from chemical potential energy stored between atoms in chemical bonds and is NOT from mass-to-energy conversion which requires a very specific sort of thing, i.e. nuclear fission. If you have a truly closed system, the mass will not change at all, and there is no need to invoke E=mc2 to make it happen. The existing atoms in the closed system don't disappear, and no new atoms are created out of whole cloth. Since a closed system will have, atom-for-atom, the same exact atoms in it over any length of time, regardless of how those atoms are physically rearranged over time, the entire system will retain a constant mass. QED. --Jayron32.talk.contribs16:36, 24 February 2009 (UTC)[reply]
No, he's right. E=mc2 applies to all forms of energy, including chemical bond energies. It's just that the amount of energy change associated with breaking chemical bonds is so tiny that the mass change is nearly always below the limit of detectability. If you burn and dissipate the heat from 600,000 gallons of gasoline the resulting CO2 + H2O would be about 1 gram lighter than the sum of the initial gasoline + oxygen. Dragons flight (talk) 16:52, 24 February 2009 (UTC)[reply]
Mass-energy equivalence is tossed around a lot these days. In this case, it is correct that energy-changes could result in minute mass changes, but those are truly minuscule and absolutely negligible for the purposes of this scenario. The original poster is probably just underestimating how much food it really takes - maybe some statistics on agriculture will help. A cow can consume 300 pounds of water in a single day. In a year, this will equate to tens of thousands of pounds of water. Does this help put into perspective? Nimur (talk) 18:15, 24 February 2009 (UTC)[reply]
Or even just consider the air: According to Oxygen: "An adult human in rest inhales 1.8 to 2.4 grams of oxygen per minute." We'll call that 2 grams. That's 2g*60*24=2880g per day. That works out to just over 1 tonne of oxygen in a year (which will have been converted into CO2). The newborn baby might have a mass of about 5kg, it's neglibible. --Tango (talk) 18:50, 24 February 2009 (UTC)[reply]
Well conservation of mass mostly applies to chemistry now (where E=mc2 can be safely neglected, as mentioned). And if you view this from a chemical viewpoint, it's not very strange. Humans catalyze the reaction: Food + O2 ---> Excrement + CO2 + Babies. --Pykk (talk) 19:00, 24 February 2009 (UTC)[reply]
Yep. See autocatalysis. There are a number of chemical reactions where one of the products is a catalyst of the reaction; these reactions will start slowly (if at all), and accelerate (as more product/catalyst is generated) until the supply of raw materials is depleted. TenOfAllTrades(talk) 20:03, 24 February 2009 (UTC)[reply]
There's a lot of math here to answer a simple question. Isn't the more obvious answer that the original questioner forgot about poop? APL (talk) 20:10, 24 February 2009 (UTC)[reply]
Yep - this stuff about E=mc2 is really a red herring. That's so negligable - we can ignore it for all practical purposes. So long as the container is absolutely air-tight (gas tight), water-tight and no solids, liquids or gasses come into or out of the container for the whole duration of the experiment - then the contents of the container will weigh exactly the same at the beginning as at the end. SteveBaker (talk) 20:54, 24 February 2009 (UTC)[reply]
By my extremely rough calculations, the energy losses would correspond to about 10kg over a year. That's pretty small compared to the tonnes of food, air and water than would be required, but it is probably measurable if you tried hard enough. However, if energy can be lost from the container, it may be possible for it to be gained as well (sunlight coming in the window, for example), so it's rather more difficult to work out what would happen to the mass. --Tango (talk) 21:10, 24 February 2009 (UTC)[reply]
Of course, I only realise I divided by c and not c^2 immeadiately after clicking "save"... my rough calculations actually come out at about 30μg. Ok, that's negligible! --Tango (talk) 21:13, 24 February 2009 (UTC)[reply]
Ketonuria caused by a high protein diet.
Hi I read the article on ketonuria which states that the condition can be caused by a high protein low carbohydrate diet. My question is why? Say we had a non-diabetic individual who ate nothing but high protein foods such as meat and fish. Would not their bodies be converting the amino acids produced from the digestion of their food to glycogen by the process of gluconeogenesis? Why would their body then need to metabolise fats (it is my understanding that the catabolism of fatty acids produces ketones) for energy if glycogen can be produced from the protein they are eating? Would I be right in thinking that the person's body would not be able to get all the energy it would need from glycogen produced by the gluconeogenesis of amino acids and so fatty acids would need to be broken down to provide additional energy. Hope this makes sense and any suggestions would be great. —Preceding unsigned comment added by 139.222.240.66 (talk) 16:04, 24 February 2009 (UTC)[reply]
It's simplest to answer your second question first, actually.
The body is very efficient at breaking down glucose into smaller particles and energy.
The body is very inefficient at driving the same cycle in reverse to turn small particles into glucose. (gluconeogenesis)
Functionally, the brain will not operate on any fuel other than glucose. If your brain stops, you die.
Gluconeogenesis is a last-ditch emergency effort by the body to keep from dying.
Anything becomes fair game as a matter of survival - fat and muscle included.
Back to the first question:
Remember point #2 above - it's somewhat akin to trying to drive a water wheel backwards.
You get a lot of the components for gluconeogenesis building up / pooling.
Those components are high-energy, i.e. very reactive chemically.
They're almost as happy to start engaging in side-reactions with themselves (condensation) as they are to be driven through gluconeogensis.
The products of those side-reactions are ketones.
As you can imagine, this type of diet is very effective - but it's also a very bad idea if you prefer long-term survival. It plays hell with your liver and glucose regulation, among several other niceties. arimareiji (talk) 17:14, 24 February 2009 (UTC)[reply]
The article on ketogenic diet and particularly the mechanism of action section may be helpful. If your body is in starvation mode (or thinks that it is in starvation mode) then any glucose made via gluconeogenesis will go straight to the blood stream and not be converted back into glycogen, which is the storage form. The hormones that control this process (insulin and glucagon) have opposing roles and once you're in a catabolic state the breakdown of fatty acids will be an integral part of the process. By the way, the above statement that "the brain will not operate on any fuel other than glucose" is incorrect. The brain CAN and DOES utilize energy sources other than glucose, namely the ketone bodies that are produced during starvation. --- Medical geneticist (talk) 17:52, 24 February 2009 (UTC)[reply]
Hello. I think I may wish to acquire tiny springs - 1mm diameter, length >3mm.
Does anyone know where I could get such things (UK), the springs preferably should be slightly compressable, and on the weaker side of spring constant (for their size).
Alternatively (my main question) - how could I turn tiny coils of wire into tiny springs (in real life practice) - what substance should I used, and what are the ways of making wire springy (copper wire as bought makes a coil - but isn't springy)
You'll find a spring of about the size you are looking for inside a leather watch strap pin. You know, that metal tube with a sprung tip at each end that fastens the strap to the watch and to the buckle. --Heron (talk) 19:09, 24 February 2009 (UTC)[reply]
Yes that's the sort of thing - thank you. I might need a few but I guess that if I buy 100 they won't cost much.
By the way I'm still interested in making my own...(I think the watch spring pins might be just over 1mm, .... mmmh - are ladies watch pins smaller?) If anyone can give material hints....FengRail (talk) 21:45, 24 February 2009 (UTC)[reply]
Hop over to your local dollar store and grab a selection of their $ 1 each watches. Some, but not all have a spring like what you are looking for under the battery. If you are lucky you might even find one model that has springs at the "push buttons". You could also contact your local watch repair shop and ask them if they have any. Unless you can talk them out of a couple of irreparable broken movements, the brand name stuff is likely going to cost you an arm and a leg. I tried to find a source online, but there are only a handful of manufacturers that actually make watch movements. So the springs aren't a mainstream item. Your local goldsmith will be able to point you towards a source for fine wire to make your own springs.76.97.245.5 (talk) 01:00, 25 February 2009 (UTC)[reply]
I just had an argument with a friend today who said she believed that our sexuality (ie: gay/straight/transexual/whatever) was decided for us, chemically, before we are born. I argued that there was no evidence for this and that it was much more likely that one of the trillion influences on our development have an effect at some point which eventually determin how we feel about ourselves sexually. I wondered if there is any scientific evidence either way? Is there really (as she claims) a bunch of chromosomes that are instrumental in deciding our sexual fate before we are born? Has there ever been any social studies to explore the possibillity that a certain type of upbringing is more likely to produce a homosexual?
I put this on the science desk to limit the level of 'opinion' that a question like this might generate, so please try and keep answers as factual as possible, thanks.91.111.86.8 (talk) 20:04, 24 February 2009 (UTC)[reply]
In the purest sense, a gene for outright homosexuality would be selected out of the gene pool in a single generation. So we know it can't be as simple as that. Such complex behaviors are highly likely to be a combination of nature and nurture - genes and upbringing. Bisexuality could perhaps be a gene because it wouldn't out and out prevent itself from being passed on to the next generation (although you'd still imagine it would be strongly selected against over a number of generations unless it conferred some other benefits that ultimately (and paradoxically) aided reproduction). SteveBaker (talk) 20:47, 24 February 2009 (UTC)[reply]
A dominant gene for homosexuality would be selected out in a single generation (assuming culture allowed it - plenty of homosexuals have married and had children since that was what was expected of them by society), a recessive gene could last longer, particularly if being a carrier held some advantage (like with sickle cell anaemia). One (very small, perhaps) advantage of being a carrier of the homosexual gene would be that you are likely to have homosexual siblings that wouldn't have children of their own so could help you support yours. (That's more of a mitigation of the disadvantage than an outright advantage, I suppose.) However, I agree, there is clearly something more going on than a single gene. --Tango (talk) 20:58, 24 February 2009 (UTC)[reply]
(See also, kin selection. Note though that it is certainly not the case that 100% of all homosexuals do not reproduce genetically. In fact one can probably make the argument that the history of homosexual oppression in the last few hundred years would have led to more homosexuals reproducing than the current more liberal sentiment, as I suspect those in the closet have kids more often than those out of it do.) --98.217.14.211 (talk) 05:21, 25 February 2009 (UTC)[reply]
It's possible that homosexual individuals who do not have children provide some benefit to their own close family members. If so, then while not themselves reproducing, those with a homosexuality trait may indirectly encourage the propagation of their own genes (via their siblings). I seem to recall reading about such a hypothesis once in a sociobiology class I took many, many moons ago. I'll see if I can find a source when I get home. – ClockworkSoul22:27, 24 February 2009 (UTC)[reply]
The problem with the question in many contexts is that, if one were to say "This is 100% choice" then it many people take this to mean "this is a valid reason to discriminate against someone who is homosexual", and yet we have laws in most western nations that disallow discrimination based BOTH on genetic-based traits (such as gender or skin tone), choice-based traits (such as religion), and environmentally-determined traits (such as historical national origin). The reality is likely that, like every single behavioral trait we experience, there are some combinations of genetics, environment, and choice involved in it, and every individual has a unique melange of these factors determining their own unique personalaties. To isolate one factor of a personality and say "This bit here, this bit must be all genetic" or "This bit here, this bit must be all choice" is wrong for several reasons. First, its never all genetic or all choice or all environment, and secondly, you cannot isolate a single aspect of someone's life in that way and treat its cause in isolation from the rest of their personality. Its just not that simple. --Jayron32.talk.contribs04:59, 25 February 2009 (UTC)[reply]
Clockwork, there may be some benefit to the family of a homosexual but notice that this sort of explanation isn't used for anything else. You don't speak of the (any type of trait that makes him highly unlikely to reproduce, like being infertile or disgustingly unattractive, etc) Uncle being selected for by natural selection because he provides benefits for his kin.--droptone (talk) 13:11, 25 February 2009 (UTC)[reply]
The simplest answer to that is kin selection. Most of what I would say is included or linked in that article. If you treat humans as social creatures that evolved in tribes, rather than individually, a lot of things make more sense; competing tribes try to out-survive each other. 79.66.56.21 (talk) 16:18, 25 February 2009 (UTC)[reply]
DC power supplies in parallel/series
I am building a guitar pedal at the moment and am having trouble with the power supply. I originally designed the pedal to run on 9V batteries (two of), but as I use a powered pedal board, it seemed a better idea to open it and replace the batteries with DC sockets(two of). I have the correct sockets, and have wired them up in sort of "Y" configuration - where the two tips of the Y connnect to a 9V DC socket (either +ve or -ve), and the bottom tip of the Y is the +ve or -ve supply respectively. Upon use, I have found that it does not work as it used to. It was a distortion pedal, based on the fact that op-amps saturate after a certain level of input - so I think the problem lies in the configuration of the DC supply. Right now, they are connected in some kind of pseudo-parallel configuration, and I am wondering if I connect them in series, will it solve my problem. My thinking is that when batteries are connected in parallel (+ve to +ve and -ve to -ve) the overall voltage is the same, but the current is doubled, whereas when they are connected in series (+ve of one to -ve of the other) the voltage doubles, but the current stays the same. In the battery, however, the +ve and -ve poles are connected via the chemicals in the battery - but with my DC socket, the -ve and +ve poles are isolated from each other, and to connect them (in a series fashion) would ground the power, and thus not be able to power any of my pedals. Is there any way around this?
Summary: How do I connect two DC sockets together (bear in mind, the +ve and -ve terminals are isolated from each other) so that the voltage across the two of them is equal to the sum of the two input DC voltages?
You need to know whether the pedal has the two 9 volt batteries driving different parts of the circuit at 9v each - or whether they are in series (to generate an 18 volt supply) or in parallel (to last twice as long or to produce twice as much current as a single battery). I strongly suspect the latter because there aren't many (if any) simple audio circuits that need 18 volts! However, if the two batteries WERE in series - then you just shorted out your power supply because the pedal connected the + of one plug to the - of the other...but they go back to the same power supply via the 'Y' lead! This might have damaged the power supply...or maybe blew a fuze inside - or maybe just caused a thermal trip to trip out...depending on the kind of power supply. If the batteries were in parallel - then there was no point in wiring up two separate jack plugs because they are both going to the same place. In that case the problem might be that your power supply can't produce as much current as two 9v batteries.
At any rate - you cannot double the voltage of a power supply by putting in a 'Y' lead and then connecting the + of one plug to the - of the other. That not only doesn't work - but is highly likely to do damage to the power supply. If you truly need 18 volts (which seems VERY unlikely) then you either have to go back to using 2 batteries - or you need a proper 18 volt power supply.
Many op amps require dual (split) supplies; +V and -V, and I would bet that your two 9V batteries were connected in series so one provides the positive and one the negative voltage, with the remaining two battery terminals tied together and connected to the circuit ground. Yeah, powering it with a single supply in a Y won't fly. To power the pedal you will need two 9V DC supplies, such as a pair of "wall wart" transformers. You can put sockets on your pedal that accept the wall warts' plugs. Just be sure they connect to your circuit with the same polarity as your batteries. As an alternative, at thrift shops you can often find wall warts that provide split supplies. Look for one with terminals marked, +9V and -9V, and GND or COM, then connect the COM line to the two (opposite polarity) battery terminals which were tied to the circuit ground. You can tell which ones these are because they are connected together, or you can use an ohmmeter. Then connect the +9V and -9V lines to the remaining + and - battery connectors. If you can't find ±9V transformers, your op amps will probably work ok with any voltage between ±7V and ±15V, as long as both positive and negative voltages are the same. --ChetvornoTALK22:40, 24 February 2009 (UTC)[reply]
Yes, I am powering an op-amp, and yes, I am using 18V. The op-amp I am using (NE55532) can take a 3V-25V power supply, and so I decided 18V was the most I could feasibly use. Thanks for the tip that I won't be able to generate as much current with two power supplies as with two batteries. I'm just going to revert back to batteries for now. If you can find any kind of information on turning two 9V DC supplies into one 18V DC supply then let me know. Thanks! —Preceding unsigned comment added by 81.158.231.154 (talk) 10:41, 25 February 2009 (UTC)[reply]
But why do you need 18v just to generate a few volts of audio signal? You're putting the signal into an amplifier at the end - and it CERTAINLY doesn't want 18 volts of audio! SteveBaker (talk) 16:43, 25 February 2009 (UTC)[reply]
hydrodynamic and aerodynamic
On the front of large ocean going vessels (and probably other kinds of ships too) there is a bulb shaped thingy (can't remember the name) that aids in the hydrodynamics of the ship. Thus, with this bulb thingy, the ship moves through the water easier (due to a decrease in water resistance). Does this same principle apply to cars, planes and other vehicles as they pass through the air? —Preceding unsigned comment added by 69.77.185.91 (talk) 21:07, 24 February 2009 (UTC)[reply]
A bulbous bow works on ships because they're travelling on the interface between air and water. Nothing else travels on such an interface, so you won't see bulbous bows on submarines or airplanes. --Carnildo (talk) 22:58, 24 February 2009 (UTC)[reply]
When I bought my house, the washing machine was causing bad water hammer, so I installed a water hammer arrestor which solved the problem. Years later, the problem has returned. I think I remember reading something at the time that said that eventually the arrestor fills up with water (or something like that) and something must be done to replenish it.
My question is: What do I need to do to 'replenish' it? Just remove it and shake out the water? Or do I actually need to replace it with a new one?
Drain out the water. An arrester works by creating an air-filled gap in the water line. Since air is compressible while water isn't, it absorbs the shock rather than transmitting it. --Carnildo (talk) 23:00, 24 February 2009 (UTC)[reply]
"Drain out the water" is the correct answer. However, it doesn't explain how to do that. What I did was turn off the water at the main line - so no water would flow into the house. Then, I opened all the taps. This pretty much drained all the water out of the lines. Then, I closed all the taps, turned the water back on, and the arrestor started working again. Obviously, this is limited to an arrestor that is higher than the lowest tap - since you can't drain anything below the lowest tap. -- kainaw™05:04, 25 February 2009 (UTC)[reply]
If I turn on the hot water in my shower with limited flow (not a trickle, but not a gush), within a minute the flow slows to a trickle and it starts making a rapidly-repeating banging noise that doesn't stop until it's turned off or the flow is increased. Cavitation, water hammer, or something else? arimareiji (talk) 00:13, 25 February 2009 (UTC)[reply]
Yes, mine too! A whistle, indeed. What is it? I guess that that particular speed of the flow corresponds to a proper frequency of the tap and make it resonate. --pma (talk) 00:32, 25 February 2009 (UTC)[reply]
Usually, but not always, it's just something stuck in your aerator (faucet) or showerhead. Unscrew that and descale it with some vinegar. See if the noise persists. 76.97.245.5 (talk) 01:03, 25 February 2009 (UTC)[reply]
That jogged my memory. What you describe happens when the screw holding the washer works loose. I've actually seen that, the prohibition against original research be damned. --Milkbreath (talk) 05:09, 25 February 2009 (UTC)[reply]
This little phenomenon occurs to me as well. The banging noise is called Water hammer, and if it starts, you should stop it quickly by turning it off/increasing the flow, whatnot. The signature bang characteristic of water hammer is caused by rapidly increasing pressure in your pipes. If it continues, your pipes could burst from the pressure, so I would remedy this with whatever remedies happen to appear here. Until It Sleeps 05:24, 25 February 2009 (UTC)[reply]
Although it is, as our article says, "relatively stable to light," keeping light out of the containers it's stored in minimizes the breakdown of the compound. Deor (talk) 14:12, 25 February 2009 (UTC)[reply]
Because it is sensitive to light. If it is exposed to too much light it turns into silver (I think). As our article says, it isn't as sensitive as silver halide, but it is still sensitive. --Tango (talk) 14:15, 25 February 2009 (UTC)[reply]
Silver nitrate used to be used for photographic work - so it is indeed sensitive to light. But the main reason it was replaced is because it's not sensitive enough for dim light or short exposures. So it's RELATIVELY insensitive (compared to other photosensitive substances) - but a dark glass jar is good enough. SteveBaker (talk) 16:39, 25 February 2009 (UTC)[reply]
high electric tension
Hello
I heard that when there is very high electric tension (eg 1000000 Walt), there is no longer a risk to humans.
1 Is it true?
2 What is the explanation for this phenomenon?
In the article Electric shock it is written that the danger is primarily in the tensions between 30 and 250 volt, it may be related to the subject.
I think the reason high tension cables aren't dangerous is because they are kept up high out of the way so you can't form a complete circuit to ground. High voltage means lower current, which might make a difference, but as electric shock from a high tension cable will still kill you. --Tango (talk) 14:19, 25 February 2009 (UTC)[reply]
There may be some confusion, as electric tension is a measure of voltage, not wattage (electric power). A high-tension power line will be VERY dangerous - "lower current" does not mean "safe levels". A Van de Graaff generator, on the other hand, is high voltage and very low current, and is generally not harmful (but this is not a guarantee - you can still get a painful shock, depending on what you do with it!) Finally, high frequency electricity will be subject to skin effect and will probably not penetrate deeply into the human, making it "safer" than lower frequency AC current. Again, none of these are guarantees of safety - there are situations where skin-effect is not sufficient to protect you. In the case of very high power (watts), there are other safety issues, including thermal heating, which may be equally dangerous as electrocution. Nimur (talk) 16:06, 25 February 2009 (UTC)[reply]
I think there is a fundamental confusion here. The risk due to touching - or even getting within a few feet of a high tension power cable is most definitely very high indeed. What I think the OP is referring to is that it is (perhaps) no longer considered dangerous to live, work or generally be close to high tension power lines. There has been much controversy over this in the past where people who live or work close to these gigantic pylons have complained of a variety of long-term medical conditions that have been loosely attributed to some aspect of those power lines. There has been more talk of this in the media quite recently because the 'Obama stimulus package' includes a boatload of cash for creating a much improved electrical grid throughout the USA in order to allow far distant wind and solar power plants to distribute their power all across the country - even though they are (by necessity) situated in fairly remote an/or inhospitable places. This huge build-out of new high tension power lines will doubtless upset a great many people - and the debate as to whether they are safe or harmful over the long term has resurfaced. However, there is absolutely no doubt that if you get within some short distance of the cable itself, you could come to a great deal of harm! SteveBaker (talk) 16:36, 25 February 2009 (UTC)[reply]
Could someone with CIPA still die from a chest stab?
(First off, why isn't there a Medical section of the RD?)
There isn't a medical section of the RD because we aren't allowed to answer medical questions. General questions about biology (which you might reasonably describe this one as) belong here - with the other science questions. We generally resist the temptation to add new RD sections because we only have a fairly fixed number of respondants and increasing the number of desks doesn't really change that...if anything, it makes matters worse because someone who is not generally interested in answering 'medical' questions wouldn't see your question because they wouldn't patrol that desk. Putting the question here in science guarantees the most 'eyes' on the problem. SteveBaker (talk) 16:27, 25 February 2009 (UTC)[reply]
Please do your own homework.
Resolved
—Preceding unsigned comment added by TungstenCarbide (talk • contribs) 04:02, 19 February 2009 (UTC)
Please do your own homework.
Welcome to the Wikipedia Help desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems.
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