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February 13

Post-It Note adhesive Thickness

I just got back from a trade show, and one of the bits 'o swag was a "brick" of Post-It Notes, about 2-3/4 inch (70cm) thick.

All the notes have the adhesive on one edge. It's a continuous strip of adhesive on each sheet, about 3/4 inch wide, and the paper is about 2-3/4 x 2-3/4 inch, making the brick almost a perfect cube.

I would have expected the thickness of the adhesive to be obvious along the adheded (is that a word?) edge. However, the cube looked flat. So I got out my Mitutoyo CD-6"P calipers, and took some measurements. 10 sheets measured .0415", making each sheet 4.15 mils thick. The thickness of the brick was 2.7815", meaning that (rounding off here) there were 670 sheets in the brick.

Now I admit that the caliper measurements aren't perfectly repeatable, since I can't calibrate the force I use use when making a measurement. But I was unable to detect any difference between the thickness of the adheded (there it is again) edge, and the plain edge.

If we assume that the thickness of the adhesive was a millionth of an inch, that would make a difference of .67 mils over the thickness of the brick, which would be just detectable using this crude instrument.

I find it hard to believe that such a thin coating is possible, but I hold the evidence in my hand. I checked the Wikipedia article and Googled around trying to find out the thickness of the adhesive layer with no luck. Any of y'all have an idea where I can get that information? Thanks. Bunthorne (talk) 00:03, 13 February 2009 (UTC)

oh my god do I envy the kind of time you seem to have!!! 82.120.236.246 (talk) 00:20, 13 February 2009 (UTC)

Well, you know, I don't think this took him more than five minutes with the calipers. -- Captain Disdain (talk) 02:37, 13 February 2009 (UTC)

and writing the above? and rumination ? —Preceding unsigned comment added by 82.120.236.246 (talk) 03:53, 13 February 2009 (UTC)

You're right, it was a downright Herculean effort. How did he find the time?! -- Captain Disdain (talk) 08:56, 13 February 2009 (UTC)

It helps to schedule some ruminatin' time every day. (Read, 'rite, ruminate!) —Tamfang (talk) 02:41, 21 February 2009 (UTC)

Once you start looking at scales of a millionth of an inch, the surface of a piece of paper is anything but flat. --Carnildo (talk) 01:44, 13 February 2009 (UTC)

Does the micro-weight of the sticky area vs non-sticky come into it? Julia Rossi (talk) 01:58, 13 February 2009 (UTC)

Micro weight maybe not, but macro weight they flatten the block under while producing (cutting) it. You can buy this Postit type adhesive in a spray can. Other than glue or the sticky stuff on the back of Duct tape, this type of adhesive doesn't add much if any bulk. The material will try to "even out" when pressed and so the fibers sticking out of the non adhesive part will not be depressed as much by comparison as the part with the sticky layers. 76.97.245.5 (talk) 04:09, 13 February 2009 (UTC)

Here's a side issue on this topic. The chemist at 3M who invented the Post-It adhesive was trying to develop a powerful new glue. When he came up with a weak adhesive, his cohorts laughed at him and made him the butt of jokes. However, he had the last laugh. – GlowWorm —Preceding unsigned comment added by 98.17.32.201 (talk) 18:17, 13 February 2009 (UTC)

It's interesting to note that the post-it 'brick' that I have has alternate sheets glued at alternate ends to form a 'zig zag' of sheets. I wonder whether they did that specifically to circumvent the theoretical difficulty that our OP mentions when (possibly) using less absorbant paper or something? SteveBaker (talk) 21:20, 13 February 2009 (UTC)

The alternating post-it brick is used for a post-it dispenser. If all the sheets are glued on the same side, when you pull one out the top, it will lift the whole brick, come loose, and then you'll have to hand-feed the next sheet through the slot on top. If they alternate, pulling one will lift the next sheet through the slot at the top before separating from it. -- kainaw™ 21:27, 13 February 2009 (UTC)

It's probable that the adhesive and paper are sufficiently compressible so that the "adheded" edge is of the same thickness as the uncompressed, paper-only parts of the block. As the OP mentions, "compression" force resulted in a slightly non-repeatable measurement by calipers. Though it's hard to imagine, the individual sheet of paper probably squeezes into a perfect little rectangular prism of fairly uniform thickness (height?), even though there is more material on the "adheded" edge. (Alternatively, there could be slightly thinner paper on the "adheded" side, but this would be really hard to manufacture).

Now, to verify my original assumption, you could probably perform an experiment to slice the cube into only-paper and paper-plus-adhesive blocks. Measure the mass of these, and calculate the excess mass which must be due to the adhesive. I think that there will be a serious signal-to-noise problem, bordering on the un-measurable, but for the sake of science... we must try. Nimur (talk) 18:51, 14 February 2009 (UTC)

I'd love to try Nimur's idea, which borders on genius, but the only instrument I have to measure mass is a bathroom scale. I could probably weigh myself holding the subjects, but I'm afraid the closest reliable reading is +/- 2 pounds, so I'd have to get either a somewhat better scale, or a massive number of bricks. Thanks for the ideas. Bunthorne (talk) 05:24, 15 February 2009 (UTC)

It's not the language desk, but I believe the correct word is adhered. My money is on the manufacturing process. Compressing the sticky edge with an industrial machine in a way that can't be matched by your measuring caliper. -- MacAddct1984 ^{(talk • contribs)} 21:12, 17 February 2009 (UTC)

If counting thru a 2 inch brick of post-it notes takes time on one's hands, look at some of the post-it animations on www.eepybird.com and imagine what that must have taken. 207.241.239.70 (talk) 08:14, 18 February 2009 (UTC)

Sorry if it sounds like I'm nitpicking, but 2 3/4 inches does NOT equal 70 cm . . . maybe 70 mm??

Tesla, Edison, Einstein and Asperger syndrome.

Just out of curiosity, did Tesla, Edison and Einstein all had Asperger syndrome? I read that somewhere and I was wondering if it's true. Thanks in advance. ― Ann _{( user | talk )} 00:41, 13 February 2009 (UTC)

Well, Hans Asperger first described what has since become known as Asperger syndrome in 1944, a year after Tesla died and 13 years after Edison died. Einstein died 11 years after that first description, but still well before the term "Asperger syndrome" was first popularised in 1981, and even longer before it become a common diagnosis. So, anyone saying any of them had Asperger syndrome is making, at best, an educated guess based on historical accounts. To get any kind of reliable diagnosis requires an intentional assessment of a wide variety of qualities. --Tango (talk) 00:52, 13 February 2009 (UTC)

I've read a couple of biographies of Einstein and he does have a lot of the attributes of an Asperger sufferer. Comparing his story to the criteria in DSM IV, he pretty clearly could be diagnosed that way on the basis of the information in his bio's. I don't know enough about Edison or Tesla. It wouldn't surprise me if Tesla was and Edison wasn't...but I really don't have enough information. SteveBaker (talk) 03:55, 13 February 2009 (UTC)

It's tough to apply diagnoses backwards in time—heck, it's not even easy to apply them to real, living people! Einstein's a tough nut to crack in particular because everyone sees him as what they want to see him as... --98.217.14.211 (talk) 16:52, 13 February 2009 (UTC)

I agree. But from the DSM IV description, I think Einstein can easily be shown to have had:

• A2) Failure to develop peer relationships appropriate to developmental level.
• A3) Lack of social or emotional reciprocity.
• B1) Encompassing preoccupation with one or more stereotyped and restricted patterns of interest that is abnormal either in intensity or focus.
• C) Significant impairment in social, occupational or other important areas of functioning.
• D) No delay in aquisition of language as a child.
• E) No delay in cognitive development.
• F) Criteria for Pervasive Developmental Disorder or Schizophrenia NOT present.

A2—the man had plenty of friends, lovers, etc., throughout his life. A3—the man was a life-long activist for the suffering, wrote passionately on the subject, got denounced by the Nazis and a 1,000 page FBI file for his troubles. B1—how exactly where his patterns of interest restricted? Patent examiner, theoretical physicist, social activist, violinist, writer, lecturer, etc.? C—what was so impaired? Are we just using the "Einstein was a weirdo" stereotype here, or are we basing this on his actual life and interactions? D,E,F—a lack of something abnormal seems hardly relevant here?

As with anybody as "iconic" as Einstein there is an elaborate mythology and stereotypes of his behavior that have percolated throughout culture. The idea that Einstein had his "head in the clouds" and thought of nothing but physics is plainly false (it is easy enough to see if one reads his collected essays—the man had tons of interests, was extremely cultured, was very "down to earth" on a wide variety of things).

My point in being contrarian here is not to make strong statements about Einstein, but to point out that each of those criteria are extremely subjective. Even in a living, breathing, non-famous person they can be quite ambiguous in everything but the outlier, extreme cases. With a historical figure around which an expansive mythology has been built—one that is demonstrably not even close to being accurate, like the one of Einstein as being a spaced out mystic old grandpa—it seems rather impossible to me to make a retrospective analyses unless of course they are one of the outlier cases (and Einstein doesn't seem to be one of those). For example, the fact that Einstein was a subversive civil rights activist and an unapologetic socialist is something that has long been underemphasized, as it for decades made people politically uncomfortable (even today, while his civil rights work is now much more paid attention to, his socialism is downplayed, though it is clear it was important to him for most of his life). He's not as simple as the caricature of him makes out. --98.217.14.211 (talk) 19:23, 13 February 2009 (UTC)

Where do people get this idea that Einstein had Asperger's? Never mind a detailed look through a list of symptoms, who would ever come up with this idea in the first place? It seems to be based on nothing more than the idea that smart people must be "different from the rest of us". People seem shocked that a smart person might go to clubs or be a surfer or womanize. The perception of intelligence as a kind of mental abnormality is a threat to the future of the human race. We should be fighting these nonsense diagnoses, not entertaining them. -- BenRG (talk) 13:56, 14 February 2009 (UTC)

Indeed. Asperger's is a very fashionable diagnosis at the moment, and it's common for people (not doctors, so much, they know a little better) to diagnose every smart person that has difficulty making friends as having it. I'm a smart person that has difficulty making friends, I do not have Asperger's (I was tested for it). I put my difficulty making friends down to two things, difficulty finding people I have something in common with (that gotten easier as I've moved up through education, there are plenty of smart people around once you get to Uni), and the fact that I was bullied in school because of my intelligence and as a result I tend to be quite closed off emotionally (a couple of pints helps with that!). I expect those reasons apply to a large number of smart people. (I should make it clear, I do have plenty of friends, it's just difficult to form that initial bond.) --Tango (talk) 14:20, 14 February 2009 (UTC)

The initial bond thing is key here. If someone struggles to make friends, but once made, can chat away easily with them, then the person probably has trust issues _{(awaits big pharma companies to start pushing oxytocin reuptake inhibitors or the like).} If the person just cannot empathise with people and doesn't chat to those they know well, then it is more likely Asperger's. --Mark PEA (talk) 12:40, 15 February 2009 (UTC)

• I have never seen strong indications that Thomas Edison had Asperger's syndrome. He was a personable and charismatic leader of a research group, able to impress financiers, writers and the general public. He always had a group of close friends, contra-indicating Asperger's. He could be quite manipulative, indicating an understanding of the inner thoughts of supporters and competitors. He liked to experiment as a child with chemicals, but was not the overly verbal "little professor." An Aspie would not have been able to set up a business selling treats and self-published newspapers on a train as did the young Edison. "The wizard who spat on the floor" was one characterization.He was a deaf gadgeteer and his one great emphasis in life was inventing for the sake of inventing. Tesla, on the other hand seemed obsessive-compulsive and psychotic/delusional more than Aspie. Einstein was pretty odd in his lack of interpersonal loyalty towards spouse or offspring,and had some oddities in his childhood, but I have no strong opinion as to whether he had Asperger's. It does seem a bit grasping for Aspies or their family members to try and claim historical figures as fellow non-neurotypicals. Edison (talk) 02:08, 17 February 2009 (UTC)

comb attracting little pieces of paper

Classic physics example: A comb that's been rubbed can attract little pieces of paper. The explanation I've read is that the comb becomes charged, and it causes the neutral paper's atoms to be polarized. The positive ends of the atoms in the paper are attracted to the negatively charged comb. But that doesn't seem to make sense, because the negative ends of the atoms would equally be repelled by the paper. Since there are equal #s of negative and positive on the paper, shouldn't there be zero movement (no attraction/repulsion)? Also, the paper sometimes are repelled? Why? Thanks in advance. 128.163.224.222 (talk) 03:38, 13 February 2009 (UTC)

I can't really recommend our pages Static electricity and Triboelectric effect. The simple Wikipedua version is shorter, but I can't say I find it more enlightening [1]. Nevertheless you might find them useful. 76.97.245.5 (talk) 04:25, 13 February 2009 (UTC)

Similarly to the recent question about Saturn's gravity, the answer lies in the fact that the electric charge is only one of the factors governing the strength of the electic force. The other factor is the distance. As the negatively charged comb atracts the positive charges in the paper and repells the negative ones, those charges separate and the positive charges come closer to the comb. That way the atractive force becomes stronger than the repulsive force and the paper ends up being atracted. Dauto (talk) 05:52, 13 February 2009 (UTC)

I think something like that would be good on our pages. Would s.o. have the time to write it up? 76.97.245.5 (talk) 08:29, 13 February 2009 (UTC)

That doesn't make sense to me. If the comb attracts the positives, it should repel the negatives an equal amount for a net of zero. I thought that the presence of the electrons on the comb (or absence, I don't know which) would make it have a net charge with respect to, well, the rest of the universe, basically. Let's say the comb has excess electrons (it doesn't matter); the paper bits would have a positive charge with respect to the comb and would be attracted. A pile of lead shot would be equally attracted to the comb but would be too heavy to be lifted or even moved by the feeble forces involved. --Milkbreath (talk) 13:21, 13 February 2009 (UTC)

If the comb has excess electrons, they will repel the electrons (it's the electrons that are mobile) in each bit of paper. So the electron cloud around each atomic nucleus in the paper is very slightly displaced - it is no longer centred on the nucleus. The net effect over the whole piece of paper is that there is a slight deficiency of electrons nearest the comb and a slight excess furthest away. Force dimishes as the square of the distance, so the attraction of the positive end of the dipole is greater than the repulsion of the negative end. Philip Trueman (talk) 13:31, 13 February 2009 (UTC)

If I remember correctly, it's called electrostatic induction. (Just giving a name to Philip's explanation) --Bennybp (talk) 13:57, 13 February 2009 (UTC)

Further proof that I'm seriously stupid. If the comb is pushing the electrons in the paper away, that force is pushing the paper away, or those electrons would go right back where they were. The reason that that force doesn't make the paper move away is that the now-exposed positive charges attract the comb, for a net force of zero. I must be thick as a brick. --Milkbreath (talk) 14:31, 13 February 2009 (UTC)

The comb will now actually attract the paper, since now the positive charge is closer to the comb, and the negative charge is farther away (Coulomb's Law). I've never seen it done with a comb and paper, but balloons (one charged will actually attract a neutral one). --Bennybp (talk) 16:22, 13 February 2009 (UTC)

Paper is (very) slightly conductive. When the comb becomes charged, the difference in charge between it and the bit of paper causes the paper to be attracted to the comb. When the charge on the paper becomes equal to the charge on the comb, it is strongly repelled. Try this with a bit od cereal(slightly conductive) suspended from a silk or polyester thread(insulator), and a rubber (insulator) comb or PVC pipe rubbed with wool or silk or whatever. The bit of cereal will be strongly attracted to the comb until it gains charge, then strongly repelled. It is not necessarily a matter of polarization. It is a matter of different charges attracting, and transfer of charge. For a polarization demo, bring the charged comb near, but not touching, an insulated piece of metal. The far end of the metal object will then repel a Cheerio charged from the same comb. This is just stuff Steven Gray discovered in the early 18th century. Electroscopes work nicely by induction.Edison (talk) 02:17, 17 February 2009 (UTC)

Syndrome or Disorder?

In order to respond to our previous question about Asperger syndrome and Einstein - I looked up the precise symptoms in the 'DSM IV' (which is the 'bible' of psychiatric diagnosis).

Why is it that DSM IV describes Asperger's as "Asperger's Disorder" and not "Asperger's Syndrome" as everyone else seems to do? Is there some important difference between a "Disorder" and a "Syndrome" in psych terminology?

SteveBaker (talk) 04:01, 13 February 2009 (UTC)

In technical discussions, a "disorder" or "disease" refers to the underlying condition or malfunction, while a "syndrome" refers to a collection of co-occurring symptoms or signs. A syndrome need not have unique cause, as the same constellation of symptoms might be caused in multiple different ways. In practice, the distinction may be abused or ignored, especially since many syndromes actually do only point to one unique cause. Dragons flight (talk) 04:16, 13 February 2009 (UTC)

So DSM is saying that Asperger's has a single underlying cause? Interesting. SteveBaker (talk) 04:50, 13 February 2009 (UTC)

Not quite, it's thought to have seveal underlying causes. We're just not entirely sure what they are yet, most likely genetics. —Cyclonenim (talk · contribs · email) 07:39, 13 February 2009 (UTC)

Well, that's what I thought - so back to the original question: Why 'disorder' and not 'syndrome'? In fact - a quick skim of the DSM IV index suggests that they never call anything a 'syndrome'. On the other hand we have 'AIDS' which is a syndrome (that's what the 'S' stands for). SteveBaker (talk) 08:05, 13 February 2009 (UTC)

I was doing a project for a client that had me read up on a medical topic. I then started work on a related wikipedia page and after a while was happy if I had a term where there were not at least 2 different versions describing the same thing with factions warring whose term was the better one. (First prize went to 5 varieties for one item.) Mental disorder and Classification of mental disorders say there are two accepted systems ICD and DSM. So maybe they are using different terms to reflect different views. Or they're just defending their turf. 76.97.245.5 (talk) 08:47, 13 February 2009 (UTC)

There's a desire in the community at large to "de-perjorify" language in an imprecise way. The word "disorder" implies a negative thing, that there is a normal (i.e. order) way to be, and that if you have a condition, that condition represents a "dis"-order, i.e. not normal, i.e. you are broken. Over time, there has been a trend in society to change the terms to remove distinctions that imply "brokenness" or "less than normalcy" for all sorts of conditions. Consider the spectrum of terms: mentally retarded-slow-mentally handicapped-mentally challenged-mentally different-exceptional. Over the past 30 years or so, these terms have been used to describe the exact same set of conditions in an individual. Look at the early end of the spectrum compared to the modern term, "exceptional". Exceptional even sounds like its a benefit. Does little Joey have a learning disability? No, he's "exceptional". Same deal with disorder vs. syndrome. A disorder implies that something is broken that requires modification in order to work. A syndrome merely sounds like a set of differences that requires no intervention. We need to fix a disorder. You need to learn to live with a syndrome. The medical professionals who wrote the DSM IV sound like they aren't necessarily caving to political pressures to use imprecise or cuddly language. These are real problems, and require real interventions in order to help people cope with them. Asperger's is not like being left handed; it's not a neutral condition with regards to how people interact socially in the world, and it requires serious minded people who are willing to approach it in a way that helps people who have it integrate in the world in a meaningful way. Changing its name does not change the need to deal with it properly. --Jayron32.talk.contribs 17:24, 13 February 2009 (UTC)

Hmmm. Somehow I doubt that all (or even most) people with Asperger's would agree that their condition is something that "needs to be fixed". Gandalf61 (talk)

Indeed no! I'd be violently opposed to anyone trying to 'fix' my Asperger's - for me, the benefits outweigh the losses. Not all aspies feel that way though. I wouldn't object to 'disorder' though - there is definitely something wrong with my brain - it's just that the consequences of that 'wrongness' are a mixed bag of benefits and down-sides. What I would wish for is MUCH earlier detection - and proper training to help aspies know what their limitations are and how to work around them. I didn't find out until maybe 10 years ago - and knowing what I know now, I just cringe at some of the things I totally screwed up as a kid and young adult. SteveBaker (talk) 17:56, 13 February 2009 (UTC)

Is there anybody without a 'disorder' at that rate? Just because a greater percentage of people do a thing doesn't mean it is the better way. For instance it is quite normal to get in a huff when criticized and ignore any practical lessons that there might be. It is quite normal to follow a leader and do what they do even if it is wrong and bad. Yes normal is a whole mixed bag of contrary ways of doing things, social anthropology may be a bit unscientific but appealing to the behaviour of bunches of ape men in caves seems about the best explanation. I wonder though what types of people the future belongs to. Dmcq (talk) 10:06, 14 February 2009 (UTC)

asexual reproduction

is it possible (for women) to reproduce asexually using the power of the mind alone? If so, are there any documented cases? If not, what physical constraints in the human body would prevent this effect? Thank you. —Preceding unsigned comment added by 82.120.236.246 (talk) 05:34, 13 February 2009 (UTC)

Short answer: NO. A woman's body cannot produce the sperm necessary to fertilize one of her eggs in order to create a diploid cell. Other dipoid cells of the woman's body do not have the right genes activated in order to start a new embrio. Dauto (talk) 05:58, 13 February 2009 (UTC)

Not in humans (although I'm not sure if it's technically impossible) and definitely not related to the power of the mind, but see parthenogenesis. Zain Ebrahim (talk) 09:07, 13 February 2009 (UTC)

Also see the section Wikipedia:Reference_desk/Science#Same-sex_gametes_combining_to_form_a_zygote.3F. Mammals take two to tango. Even those genetically modifed mice that let you make a viable embryo out of two eggs doesn't make asexual mammals possible. Someguy1221 (talk) 09:18, 13 February 2009 (UTC)

Fingerprints

i always had doubts about this ..is it an absolute truth that finger prints are unique for each one , isnt been recoreded even for once that two indivisiuals has the same finger print , and when was the first time this finger print thing was mintioned ..??????? —Preceding unsigned comment added by Mjaafreh2008 (talk • contribs) 11:20, 13 February 2009 (UTC)

Have you read Fingerprint#Validity_of_fingerprinting_for_identification? 130.88.151.87 (talk) 11:31, 13 February 2009 (UTC)

It depends on what level of accuracy you look at. Have there ever been two fingerprints from different people which were exactly alike ? Probably not. Have there been two different prints which were close enough to be mistakenly taken to be the same print ? Absolutely. This is especially true if fingerprints are smudged or partial, as they frequently are at crime scenes.

Another factor that comes into play is use of fingerprint databases. Let's say that a match can be found with only a 1 in a million rate of misidentification of the wrong person. If fingerprints are used to compare a crime scene print with a suspect seen leaving the premises around the time of the murder, then it's very unlikely the print will be found to match if it doesn't. So, that's a good usage. But now let's imagine that nobody was seen leaving the scene, and instead they run the print against a database that contains millions of fingerprints. With that 1 in a million failure rate, you'd expect one or more to match, just based on chance. Arresting such a person, based solely on their fingerprint, would not serve justice. Investigating people further who match might make sense, though. If one of them was an acquaintance of the murder victim, and has a record of performing similar murders, then an arrest would make sense. StuRat (talk) 15:52, 13 February 2009 (UTC)

WILL ... mabey op should look in the link he listed beforehttp://www.metacafe.com/watch/98111/miracles_of_the_quran_12/ i dont think this is a coincidence too , dont you think —Preceding unsigned comment added by 94.249.98.74 (talk) 19:36, 13 February 2009 (UTC)

The article cited above on validity and reliability of the method noted that the FBI incorrectly said there was a match between the prints of an innocent man (as later determined) and prints left by a terrorist bomber. The validation of the methodology has apparently been mostly by handwaving assertions rather than scientific and objective testing. Edison (talk) 01:00, 14 February 2009 (UTC)

Note that many of the failings of fingerprints can also apply to DNA testing. That is, while both prints and DNA are supposedly always unique (although, in the case of identical twin DNA, you'd need to look in great detail to find mutations, etc.), they can both still fail to identify, with either false positives or negatives, for similar reasons:

1) Poor quality prints or degraded DNA can both result in people declaring a match, when they really don't have enough data to say with any certainty.

2) Both are subject to simple human error, like accidentally submitting the same sample as if were both prints/DNA samples, resulting in a false match.

3) Both are subject to the expert lying on the stand about there being a match, due to bribes, pressure from the prosecution, threats from the defense, etc. Prints aren't quite as bad, in this respect, though, as jurors are more able to judge for themselves whether a match exists (provided they are actually shown the correct samples). StuRat (talk) 14:46, 14 February 2009 (UTC)

Snowflake symmetry

Why are snowflakes symmetrical? How does one leg know to become exactly like the others? --Milkbreath (talk) 12:04, 13 February 2009 (UTC)

I think the answer (i.e. I read it somewhere once - but here's a link) is that in general they aren't: it's just that the pretty symmetrical ones are those whose photos get into the books. AndrewWTaylor (talk) 13:02, 13 February 2009 (UTC)

Indeed. Our article on snow says "The most common snow particles are visibly irregular, although near-perfect snowflakes may be more common in pictures because they are more visually appealing". Gandalf61 (talk) 13:18, 13 February 2009 (UTC)

I've looked at a lot of snowflakes over the course of a life lived mostly at 40 North. When you do get individual snowflakes, they are quite regular. I don't know what those articles are talking about. But, leaving that aside for the moment, let me rephrase the question: In the not uncommon snowflake that in gross structure is radially symmetrical, what forces are at work in creating the symmetry? How can one leg know what the others are doing, so to speak? --Milkbreath (talk) 13:28, 13 February 2009 (UTC)

See http://www.sciam.com/article.cfm?id=why-are-snowflakes-symmet Cheers.--Fuhghettaboutit (talk) 13:42, 13 February 2009 (UTC)

Good link. So, nobody knows. I can live with that. --Milkbreath (talk) 14:37, 13 February 2009 (UTC)

I don't think there is any mystery here. The six branches of the snow flake presumably grow radially outwards at the same rate, and the length and breadth of side branches or plates depends on the temperature and humidity that the snowflake is experiencing at a given point in time, so it is not surprising if all branches show similar sequences and patterns of side branches. Observer bias then makes us focus on the symmetries and ignore the imperfections. If you look closely at the photographs here or here or even in the iconic Wilson Bentley photographs, you see that the symmetry is far from perfect. Gandalf61 (talk) 15:20, 13 February 2009 (UTC)

I think we know. The core ice crystal is hexagonal - as the crystal is swirled around inside the cloud, it accretes more ice until it becomes too heavy to stay inside the cloud and then falls to earth. In general, whatever humidity/temperature/pressure changes happen to one face of the crystal happen identically to the other five faces - so however one side grows, the other sides tend to grow the exact same way. What makes them slightly asymmetrical is that the conditions may not be PRECISELY the same on all six arms and also, sometimes they are damaged by collisions with other snowflakes. SteveBaker (talk) 15:30, 13 February 2009 (UTC)

(ECx2) They gave a good explanation, the same one I thought of:

1) Different temp/humidity combos result in many different types of branching.

2) Since the conditions are likely to be identical on all sides of the flake, the branching is likely to be the same on all sides.

3) When temp or humidity do change, during snowflake formation, the type of branching changes on all sides of the flake. The result is a complex, yet symmetrical, formation.

4) So, then why are so many not symmetrical ? I suspect that collisions are the main culprit, allowing flakes to break or stick together.

It also seems to me that this is part of a larger question: Why do crystals, under ideal conditions, tend to form symmetrical shapes ? The explanation would be similar to that for snowflakes. StuRat (talk) 15:33, 13 February 2009 (UTC)

Why are snowflakes flat? Most crystals have substantial amounts of material in three dimensions. Does the thickness vary in different snowflakes? Are there bumps or other extrusions on the flatness that vary in size and placement in different snowflakes? If there are bumps, do they form a pattern, perhaps hexagonal? Has anyone photographed, or even examined, snow flakes viewed on edge? – GlowWorm —Preceding unsigned comment added by 98.17.32.201 (talk) 17:08, 13 February 2009 (UTC)

One of the links Gandalf61 posted lists a variety of snowflake types, many of which are far from flat. Depending on the temperature the snowflake forms at, it may grow primarily along the c-axis ("vertical"), and come out as something like a thin needle; or it may grow primarily along the a-axes, and come out flat. Take a look at the morphology diagram here. Also, snowflakes generally don't form at constant humidity and temperature — so for instance if one starts forming at a temperature that drives c-axis growth, then (because of a temperature change) switches to a-axis growth, you'll get something like a capped column. -- Speaker to Lampposts (talk) 08:07, 14 February 2009 (UTC)

I missed that link. I'll order a couple of those books. – GlowWorm. —Preceding unsigned comment added by 98.17.32.201 (talk) 10:16, 14 February 2009 (UTC)

Was Banting really the first to discover insulin?

People in Romania believe otherwise !They say it was Palescu!(Ramanathan) —Preceding unsigned comment added by 212.247.70.129 (talk) 13:22, 13 February 2009 (UTC)

And was it Best or MacLeod who should be credited as his partner in discovery?(Ramanathan) —Preceding unsigned comment added by 212.247.70.129 (talk) 13:24, 13 February 2009 (UTC)

Our article insulin says that Nicolae Paulescu was the first to isolate insulin, both those articles, and the references cited in them, should be of interest to you. DuncanHill (talk) 18:06, 13 February 2009 (UTC)

Freemartin

What does the term freemartin mean relating tocattle prodution and what causes this condition ? —Preceding unsigned comment added by 66.244.104.243 (talk) 16:26, 13 February 2009 (UTC)

Have you found our article freemartin yet? DuncanHill (talk) 18:03, 13 February 2009 (UTC)

Faster-than-light communication idea

I believe physicists that nothing can travel faster than light, c, at 300,000 m/sec. But what nothing actually had to move for something meaningful to be transmitted superluminally?

Here's my idea: (see picture here) A giant rigid cylinder made of super-strong material extends between two points in space that are one light-year apart, A and B. (Disregard the engineering infeasibility, gravitational influence of stars, galaxies, dark matter, etc.) At each end of the light-year long cylinder is a wheel with a peg to turn it. Initially, the peg at A is exactly at A and the peg at B is exactly at B. If I turn the peg from A to A', how long does it take for B to go to B'?

I see two possible outcomes:

1. Holy cow it's the answer to superluminal communication! (unlikely)

2. The rotation from the A end of the cylinder will "travel" across to point B over time, probably taking a little more than a year.

What do you folks think? —Preceding unsigned comment added by Marskid2 (talk • contribs) 16:57, 13 February 2009 (UTC)

Sorry. -- Coneslayer (talk) 17:03, 13 February 2009 (UTC)

(EC with coneslayer. I will assume his answer was similar to this). In any real material (i.e., one made of atoms which obey the laws of physics in this known universe) there is no such thing as a "rigid" cylinder. Rigid is only relative, and at the sizes you describe, there will be some deformation along the rod. When you turn A towards A', the rod in the middle begins to twist torsionally. Think if you had a piece of clay in your hands, and held one end steady while the other end you twisted. The rod will do the same thing. Now, over time, the "twist" will travel down the rod towards B, however this obviously will occur at some rate slower than the speed of light, the movement of A towards A' will not occur at the B side until the "twist" arives there. Thus, the laws of the universe are safe from giant imaginary rods. --Jayron32.talk.contribs 17:12, 13 February 2009 (UTC)

Ah that makes sense now. I definitely didn't realize how big of an assumption "rigid" was. Thanks for the quick answers! =) marskid2 (talk) 17:15, 13 February 2009 (UTC)

To elaborate a bit further: Your rod's stiffness is caused by chemical bonds, i.e. electromagnetic forces. These are communicated via photons. So any disturbance of the rod can at most travel down it at the speed of photons (i.e. the speed of light). --Stephan Schulz (talk) 17:26, 13 February 2009 (UTC)

Is anyone collecting these? In the past few years, I've seen suggestions that we use long ropes, metal bars, crystal rods, long nano-tubes... etc. I'm waiting for "What if we used a really long fish?" -- kainaw™ 19:07, 13 February 2009 (UTC)

We already know the whole idea is fishy, these are just specific variations. DMacks (talk) 19:21, 13 February 2009 (UTC)

Here [2] is a fish-powered perpetual motion machine. You have to scroll through dozens and dozens of other ideas but eventually:

"If we made a fishing rod with a tiny motor-battery combo, and it would cast out til it caught a fish, and the fish when caught was pulling against the motor til it ran backwards and recharged the battery for the next cast, we would have made another perpetual activity er motion. It would, of course, have to sense the battery charged up & generate a lure-release."

(You can tell it's a crackpot site because it's using LOTS of color/italics/underlining)

SteveBaker (talk) 21:06, 13 February 2009 (UTC)

To give him credit I think it lost something in translation from the original schizophrenia. --98.217.14.211 (talk) 04:53, 14 February 2009 (UTC)

I had a tube full of marbles yesterday. --Carnildo (talk) 00:51, 14 February 2009 (UTC)

I thought I had one also, but everyone says I lost mine years ago... DMacks (talk) 01:52, 14 February 2009 (UTC)

Just for the record, the speed of light is about 1000 times faster than what you said. :) -- Aeluwas (talk) 16:55, 14 February 2009 (UTC)

Indeed. I expect the OP meant km/s. --Tango (talk) 17:38, 14 February 2009 (UTC)

Just to answer Marskid2s original scenario, the torque on the cylinder will travel along its length at the rate of shear waves in the material, which is a little less than the rate of (longitudinal) sound waves. Assuming the cylinder is made of steel, for which the speed of sound is about 5930 m/s, the twist will travel from one end of the light-year long cylinder to the other in a little more than 50,600 years. --Chetvorno^TALK 07:10, 15 February 2009 (UTC)

PROPELLER ENGINE VS JET ENGINE AT HIGHER ALTITUDE

IS THERE MATHEMATICAL PROVE FOR DECREASE IN PROPELLER ENGINE EFFICIENCY AT HIGHER ALTITUDE IN COMPARISION TO JET ENGINE —Preceding unsigned comment added by 114.31.179.11 (talk) 18:34, 13 February 2009 (UTC)

First, typing in all caps is the equivalent of screaming at everyone. Would you walk into a library's reference desk and immediately start screaming at the poor woman behind the counter?

Second, check Newton's laws of motion. How does a propeller work? It forces air in one direction, causing the propeller to move in the opposite direction. If there is less air, there is less are to move. How does a jet engine work? Fuel is placed into a confined area. Combustion causes thrust to escape. The thrust is channelled in a specific direction, causing the engine to go in the opposite direction. The air is not used, fuel combustion is. If you take oxygen with you, you can continue using a jet engine at any altitude you like, but a propeller engine will fail at rather low altitudes for aircraft flight. -- kainaw™ 19:04, 13 February 2009 (UTC)

Forces on an aerofoil

Well, that's not the full story, as the illustration of a wingform shows. Rotate that illustration 90 deg anticlockwise and you get a propellor blade, and the lift becomes the thrust. Also, your explanation of how a jet engine works is a bit off too. The thrust created in a jet engine is not just the escaping gases rushing out the back. Remember when you were a kid you blew up a balloon, then let it go and it flew crazily around the room? That same balloon will behave in exactly the same way if you let it go in a vacuum where the escaping air has absolutely nothing to push against. The pressure inside the balloon creates the thrust, not the air being expended, and the balloon moves away from the point of low pressure (where the air is escaping). If that didn't happen we couldn't steer/guide vehicles in outer space which is a vacuum.

I don't think it is necessary to be quite so sniffy with people who type in all caps. Its not really the same as shouting in a library and their typing skills may not be as good as yours. SpinningSpark

Most people mean by jet engine a turbofan engine as used on commercial aircraft. These engines require an air intake for the compressor and have a definite altitude limit. Although technically the term includes rockets which carry their own oxidizer I think the OP probably meant turbofan. You can find a comparison of the altitude records for both types of aircraft at Flight altitude record. Both types will lose efficiency as air density decreases but I don't think you are going to find a simple formula to compare them as it depends on many aircraft design factors. SpinningSpark 22:47, 13 February 2009 (UTC)

2009 satellite collision relative velocities

Hi guys. I'm trying to add some detail to 2009 satellite collision and I'm looking for reliable sources on the relative velocities of these satellites. I've found a few sites [3] but these are "amateur" estimates fraught with speculation. Has anyone got any good sources for the relative velocity of the strike? Nimur (talk) 19:47, 13 February 2009 (UTC)

This forum seems to use more rigorous math to ge 3.4 km/s. Still hardly a reliable source. Nimur (talk) 19:57, 13 February 2009 (UTC)

I do not understand why the relative velocity would be so high (26,000 mph per the article, or een the 3.4 km/sec estimate above). If they were in circular orbits at the same height, and in the same orientation, the relative velocity should be zero. In a given orbit, satellites could be placed at the same height and orientation, spaced around the earth. Eccentricity of orbit would introduce some relative velocity. Orbits at different orientation would introduce additional velocity. Why would the launching countries place satellites in conflict orbits, where high speed collisions are likely? If a satellite is defunct, shouldn't the launching country be responsible for controlled de-orbiting (by retrorocket on board or by their or others' robotic deorbiting mission? Isn't there some coordination of orbits, to avoid the proliferation of long lasting space junk in valuable orbits, like airliners do not fly around willy-nilly ? Is there the likelihood of this debris hitting other satellites and causing even more hazardous space junk? These orbits are high enough that the junk might not reenter for a very long time. Edison (talk) 00:56, 14 February 2009 (UTC)

All of these are very valid points. When I first heard of the collision, I presumed the satellites must have been in the same orbit, with a slight separation of distance; and I assumed that the relative velocity must have been a "slow drift" on the order of meters per second that never got noticed until the two collided. However, this diagram seems to show that the two orbits were quite different ("so they cross paths at a 12 degree angle" of orbital inclination). (The map doesn't look like 12 degrees to me, but I'm not so sure the math was done right). As you say, how could this conflict of orbits have been overlooked when deciding the orbit for the launch planning for the Iridium satellite? Nimur (talk) 04:37, 14 February 2009 (UTC)

The orbits of spacecraft are affected by a multitude of factors which are very difficult to model. The satellites aren't traveling in perfect circles, the orbits change due to the effect of maneuvers, solar radiation pressure, atmospheric drag, effects of a non-spherical earth, third body effects from the moon and sun, etc. This means that orbits cannot be predicted with a high level of accuracy for long periods of time, and certainly not 12 years. Simply put, the two orbits didn't intersect when Iridium 33 was launched (in 1997), and it's likely no orbit could be chosen such that it doesn't intersect with some known object. Orbits are chosen to meet a large number of requirements, and like everything in engineering there is a trade involved. An orbit with very low risk of collision could be chosen at the expense of other requirements, or a higher risk orbit could be used and other requirements met.

It is difficult to predict when a conjunction will occur, and even then it is still probabilistic (a 1 in 25 chance of collision, for example). According to Space Debris, there are around 13,000 cataloged objects in orbit, and collision with almost any of them would be at high relative velocity, and thus catastrophic. To foresee any possible collision, conjunction analysis must be performed for every object which passes through the same altitude as Iridium 33 (or any other object you're interested in protecting), and there are probably thousands in this subset. Since the orbit of any object cannot be reliably predicted for a long period of time, this analysis has to be performed often, which is computationally intensive. When you run the analysis, all you get is probability; it isn't yes or no.

Suppose there is a conjunction with some probability of collision (1 in 25, for example). Do you maneuver to avoid the debris? A maneuver has costs, both in consumables (fuel) and potentially downtime for the satellite (a maneuver might require pointing antennas away from their targets, or some other interruption to service). The line has to be drawn somewhere, and perhaps they chose wrong.

Predicting events like this isn't cut and dried. It is a tradeoff between the risk and the cost of mitigating that risk. Perhaps Iridium didn't find it worthwhile to go through all of this, and mitigated the risk in other ways (on-orbit spare satellites). Perhaps their analysis was insufficient, or perhaps they chose to take their chances and the dice came up snake eyes.

Of course there was little Russian Space Forces could have done since Kosmos-2251 was not functioning at the time. A spacecraft can stop functioning for many reasons, either predictably or unpredictably. Thus it is not always possible to deorbit a non-functioning satellite since it may stop working without warning. To foresee a collision is difficult, as illustrated above, and it's unlikely they would undergo all of the required analysis for a non-functioning spacecraft.

As for the original poster's question, here is a picture showing the orbits of the two spacecraft. Unfortunately I can't find a good source on the relative velocity. My back-of-the-envelope number is about 10,600 m/s, or about 24,000 mph. To arrive at this I assumed two circular orbits at 776 km altitude, which gives an orbital velocity of about 7,500 m/s. The picture shows approximately 90 degrees between the two velocity vectors, making the relative velocity around 10,600 m/s. anonymous6494 07:08, 14 February 2009 (UTC)

Wow - at those speeds, the odds of a collision with 90 degree orbital inclination is astoundingly small. The circumpherence of those orbits is around 40 million meters - if the spacecraft are (say) 10 meters long - then the odds of them colliding - even if their orbits do intersect is about 8 million to one against per orbit. At 8,000 m/s orbital speeds - each orbit takes a couple of hours - so you'd expect a collision like this about once every 400 to 500 years - even if they were both at the exact same altitude! SteveBaker (talk) 23:56, 14 February 2009 (UTC)

This is exactly what I was thinking, with similar back-of-envelope probability calculation. That's why I assumed the satellites were in an almost identical orbit, with much slower relative velocity - hence my original question. Of course, the slower the relative velocity, the more time would have been available to all parties to notice an impending collision and possibly avert it. But, the more I dig in to the actual orbits, I find a lot of different orbit diagrams and a wide variety of parameters described. Hopefully a post-incident press release will come out in a while with some more reliable numbers. Nimur (talk) 14:35, 16 February 2009 (UTC)

Well, you might expect a collision between these two specific spacecraft to take place after 400-500 years. But a collision between any pair of satellites would have been reported on the news, and if we take 6000 as the number of satellites orbiting Earth, the number of pairs would be 5999+5998+...+1=18 million. Obviously it is much more likely than not for two randomly-picked satellites to have orbits that never intersect, but when the number of chances for failure is in the millions, one would expect something to happen pretty often. --Bowlhover (talk) 04:04, 15 February 2009 (UTC)

It would happen pretty often if measures weren't taken to avoid it. I'm not sure how often collision avoidance manoeuvres are made, but I know they certainly happen. --Tango (talk) 14:57, 15 February 2009 (UTC)

As I suggested above, there could be an international convention that any country or group launching a satellite is liable for any collisions it causes with preexisting and still functioning satellites. A defunct satellite could be seized and deorbitted by a robotic retrieval satellite, at the expense of the party launching the dud, to avoid the proliferation of space junk. So it is not correct that "There is little Russian Space Forces could have done." The U.S has discussed robotic deorbitting of the Hubble Space Telescope, for instance. Edison (talk) 14:47, 15 February 2009 (UTC)

Such a deorbitting mission would be very expensive and would take significant time to plan. It seems that these satellites were in polar orbits - it would be next to impossible to arrange polar orbiting satellites in such a way that their orbits never intersected any other satellite. Better tracking of satellites seems to be the answer - the commercial satellite was operational and should have been able to avoid the collision if it had been predicted. At those speeds a tiny course correction just a hour or so before the collision would probably be enough. --Tango (talk) 14:57, 15 February 2009 (UTC)

Have scientists tried mixing every combination of chemicals, elements, etc. together?

Or do they work this out mathematically, because of the obvious dangers? Maybe this sounds impractical. I just figured that most scientists felt they had a duty to uncover and report every secret that nature has tucked away in it's emergent property quantum realm. And to find out what blows up and shit.TinyTonyyy (talk) 22:11, 13 February 2009 (UTC)

I just love how the question ends with "..and shit.". -Pete5x5 (talk) 00:42, 15 February 2009 (UTC)

No to both questions. First off, over 40 million CAS registry numbers have been assigned to known compounds, so combining any two all possible pairs (without even considering such variables as temperature and pressure) would be an daunting task. And I'm fairly certain that modeling reactions computationally is quite difficult (otherwise drug companies would have a much easier job). Clarityfiend (talk) 23:05, 13 February 2009 (UTC)

There is often more to producing compounds than just mixing chemicals. There are certainly new compounds being discovered all the time (check out a Chemistry journal sometime), so they can't have got them all yet! --Tango (talk) 23:17, 13 February 2009 (UTC)

Two more things to consider why it's an emphatic no. Even things that have been combined before sometimes create different compounds under different conditions. Think of temperature, distribution, pressure, agitation and the like. Even computer modeling doesn't help getting things down to size. Folding@home uses huge amounts of computer resources donated from all over the world and they aren't even combining anything. They are modeling at what proteins look like when they are folded in different ways. Depending on what's sticking out where they behave quite differently. 76.97.245.5 (talk) 00:24, 14 February 2009 (UTC)

Imagine if you merely tried that with just a chemistry set containing 32 chemicals. How many mixtures would be required, ignoring order (with 1 to 32 components)? http://en.wikipedia.org/wiki/File:1940s_Gilbert_chemistry_set_04.jpgEdison (talk) 00:43, 14 February 2009 (UTC)

Like 32 with one chemical, 601,080,390 with 16 chemicals, etc. Edison (talk) 02:04, 14 February 2009 (UTC)

In chemistry, atoms of elements combine to form moleculess. Depending on the type anbd position of th ebonds between the atoms, the same bunch of atoms can create completely differnt molecules ("chemicals") with completely different properties. Furthermore, there is no upper bound on the size of a molecule, so there are infinitely many different "chemicals." For example, there are zillions of different moleculres that are composed exclusively of atoms of carbon and hydrogen, and they have have radically different properties. These include gasses (methane, acetelene) liquids, (pentane, hexane, benzene) and solids (Paraffin.) So there are an infinite number of different molecular combinations of just these two elements. No, we have not yet discovered tehm all. -Arch dude (talk) 02:31, 14 February 2009 (UTC)

For a simple explanation of scale, say you have everyone in the world working to combine every pair in the CAS registry. There's 40 million of them, so that's 800 trillion. There are about 6.5 billion people, so that's over 100,000 pairs per person. If each person lives 70 years, that's about 25,000 days, so you'd have to have everyone in the world mix four chemicals a day for their entire lives. That's just every pair. If you want to mix every combination, that's 2^40 million, or about 10^12 million. For comparison, there's about 10^80 to 10^85 particles in the universe. — DanielLC 19:19, 14 February 2009 (UTC)

That's only scratching the surface though - many chemicals require three ingredients in order to react - or special temperature/pressure/agitation - some require specialized catalysts. Then you get things like polymers and proteins that form bit by bit rather than all at once. Truly, the number of possibilities is beyond measurement. Then you have isomers and isotopes. Isomers are chemicals with the exact same 'ingredients' - but different shapes. Something as simple as a benzene molecule can have several 'foldings' ("chair" and "boat" forms of the benzene ring) - others exist in left and right-handed forms - one of which will be biologically active and the other not. With proteins, this 'folding' is absolutely critical. There could be hundreds, thousands, maybe millions of "different" proteins that have identical formulae but are simply folded up differently and therefore have quite different properties. Then most elements have several stable isotopes (ie larger or fewer numbers of neutrons). These have very similar (but not identical) properties - so you might well find that to try everything, there would be a few odd versions of compounds that have the same formula but are built from unusual combinations of isotopes. So doing chemistry by making some of everything and testing it is a dead end. SteveBaker (talk) 03:08, 15 February 2009 (UTC)

Imagination "like becoming someone else" to some people?

My friend has Asperger's Syndrome, so I think I understand why he said this, but he recently remarked to me that when he tries to put himself in another person's shoes, he literally feels like he becomes that person, in a way. Even if it's someone in the past.

Is this because of the autism spectrum rendering normal imaginative play in children - and hence imagination in adults, I presume - hard if not impossible? So that a person with an ASD must practically feel like they become someone else to "imagine themselves" like that?

I'll note that I looked at the imagination article, and it's a little complex, but it almost seems like it's saying that is possible, since imagination is a created world.

Of course, I'll also grant that I probably shouldn't presume that he's using words in the same way I do, either.209.244.30.221 (talk) 22:12, 13 February 2009 (UTC)

Somehow when I read your post I was immediately reminded of the writings of physicist Richard Feynman. Although certainly not in a field you'd think of in this regard he studied and described his ability to multitask. He compared that to what others described/displayed in that regard. People differ in their ability to e.g. listen and read at the same time. Some can write and speak at the same time. You can do your own experiments and compare your and your friend's results with Feynman's. While some people when reading a book hear the text read to them in their head, others see the words float off the page. So there is already a lot of variation in people not described as having any "syndrom" (or "disorder" :). If I'm not mixing things up I think I read that "Aspies" have a very visual memory. So your friend is probably creating a visual picture of the things he reads about in a book. Another thing usually described is the ability to "focus" excessively. So just the opposite of muuti-tasking. So your friend's brain may just not be able to process the information of the imaginary world and the real world at the same time. Empathy may interest you. I must say though that some of the things on that page rubbed me the wrong way. Our resident expert SteveBaker will probably be able to shed a lot more light on things. 76.97.245.5 (talk) 00:07, 14 February 2009 (UTC)

My understanding is that the underlying cause of Aspergers and Autism (and other things along that spectrum) is most likely to be due to a failure or some kind of inadequacy of the mirror neurons. These neurons are the ones that let normal humans understand how other people are thinking by literally modelling a simplified version of their thought processes in your own head. I have Aspergers - and it seems almost like everyone else has some kind of telepathy that lets them all know what each other are feeling! This seems like magic to me! Kinda like the empathic Deanna Troi on Star Trek.

The response your friend gives seems almost completely opposite to how I feel - which is that I'm simply unable to think about how someone else thinks or feels. I would speculate that perhaps your friend has discovered a way around not having a decent set of mirror neurons with which to model the other person's mental processes - but instead literally has to imagine that he is the other person and thereby use his regular neural capacity to model the other person's mental state. So for as long as he does this, he IS the other person. That's a very strange and interesting thing. If that is indeed what is going on, it would definitely be a neat trick...one that I'd very much like to learn. (Presuming it is learnable...not everything is).

I suppose it's also possible that his diagnosis as an Asperger syndrome victim is incorrect.

SteveBaker (talk) 00:45, 14 February 2009 (UTC)

I'm autistic. I have put myself in people's shoes by pretty much imagining I was them, though I'm perfectly capable of empathy without that. I don't know if it works better, but it presumably varies how well it works with the person, so it's possible that your friend finds that it works much better, and does that a lot. When I read, I imagine what it sounds like, so there's at least one Aspie with auditory memory, though I don't see how that's relevant. Also, I don't have any problem imagining things. In fact, I commonly have a problem of getting lost in my thoughts, and imagining stuff when I should be doing something. — DanielLC 19:08, 14 February 2009 (UTC)

Error measurement question

The manual for the equipment says "Accuracy specifications are given as: ±([% of reading] + [number of least significant digits])". Then it gives, for example for one measurement, "0.5% +/- 1". Does that mean I have to multiply 0.5% by my measurement, then add 1? But where does the number of least significant digit come into the calculation?128.163.224.240 (talk) 22:30, 13 February 2009 (UTC)

That kind of expression is usually found on instruments that have a digital readout and is due to an uncertainty in the last digit which is present no matter what the size of the reading. For instance, consider a frequency counter with a six-digit display reading 173.624 MHz. An error of ±0.5% is ±86,812 Hz. To this must be added the uncertainty of the last digit, which in this case represents kHz (1000 Hz) so a ±1 uncertainty corresponds to ±1000 Hz making the total accuracy limits ±87,812 Hz. We can round this to ±88 kHz since the instrument on its current range is only measuring to a resolution of 1 kHz, making the limits for the measurement 173.536-173.712 MHz. SpinningSpark 23:31, 13 February 2009 (UTC)

Isaac Asimov quote on the fractal nature of discovery

Can anyone point me to the quote of Asimov's in which he talks about how every discovery opens a whole new series of questions - he compares the process to the recursive nature of fractals.

Thanks Adambrowne666 (talk) 22:55, 13 February 2009 (UTC)

I believe that scientific knowledge has fractal properties; that no matter how much we learn; whatever is left, however small it may seem, is just as infinitely complex as the whole was to start with. That, I think, is the secret of the Universe.

- Autobiography I, Asimov: A Memoir (pub. post. 1994) - Azi Like a Fox (talk) 23:51, 13 February 2009 (UTC)

Wonderful. Thank you. Adambrowne666 (talk) 02:45, 14 February 2009 (UTC)

Resolved

-Pete5x5 (talk) 00:46, 15 February 2009 (UTC)

February 14

Questions about catnip

1. Is catnip an addictive substance (for cats)?

2. Is it possible for a cat to OD on catnip?

3. What recreational drug, when taken by a person would most closely mimic the psychoactive/physical effects of catnip on cats?

Just curious after watching videos of cats getting high on the stuff on YouTube. Thanks. --84.68.107.30 (talk) 00:27, 14 February 2009 (UTC)

1. catnip is not addictive

2. not by rolling in it or smelling it. If the cat eats too much catnip (some cats like to eat fresh catnip, mine does), it may become ill.

refs for these two answers: [4], [5]

3. hard to say, catnip affects different cats differently. Some get loopy, some get aggressive, some get a little sexual. I'd say marijuana, for its euphoric effect, but I don't know a lot of marijuana users that get hyper or aggressive. There's probably not a really analogous human drug. Alcohol is euphoric, but its effect lasts longer and it's addictive. - Nunh-huh 00:49, 14 February 2009 (UTC)

1 How would you define "addictive" in cats. I have had cats do serious damage to containers or cabinets to get at the stuff.

2 Some cats become over excited and can "conk out" from catnip. Others just get extremely tired in a hurry and wander off for a cat-nap. Reactions vary greatly between different cats. Lots of kittens and some older cats aren't affercted at all. BTW: I've seen several cats get the same reaction from elderberry.

3 Androstadienone and/or Musk probably come closest, although not in intensity. We haven't discovered a pheromone for humans that has that strong an effect (thank goodness). Maybe it's just that cats don't care about indulging. After all they are not the ones who have to go out and earn for the tuna cans. Mrrow. Also see [6] - 76.97.245.5 (talk) 02:26, 14 February 2009 (UTC)

Why do cats need a special definition of addiction? I suppose because of the muddled popular meaning of the word, we should specify that we're talking about physical dependency manifested by withdrawal symptoms or increased drug tolerance, and that catnip doesn't cause either. - Nunh-huh 03:17, 14 February 2009 (UTC)

Well caught I was thinking of the other use for psychological addiction. 76.97.245.5 (talk) 07:32, 14 February 2009 (UTC)

According to the second link above, "It is possible for cats to become immune to its effects if exposed too often". Or could it be the case that the regular dose just isn't enough to cause a high any more? How on earth do you determine if a cat is jonesing or not anyway? --Kurt Shaped Box (talk) 09:03, 14 February 2009 (UTC)

Reading a little about the effects of catnip and the short-lived - but seemingly intense high, it reminds me somewhat of the effect that freebasing crack has on a human... --Kurt Shaped Box (talk) 09:11, 14 February 2009 (UTC)

Neanderthals, Humans and Chimps

I was just reading the artical on the Neanderthal genome project. In the artical, there is reference to the Chimp's DNA being 18.77%98.77% identical to modern human DNA. What is it about the remaining 1.23% of the chimp's DNA that makes it impossible for humans and chimps to interbreed (aside from the ethical objections we may hae)? Could modern humans and neandertha;s inter-breed? —Preceding unsigned comment added by 209.161.215.58 (talk) 04:23, 14 February 2009 (UTC)

I'm not sure it's true that chimps and humans can't interbreed. It's not easy because we have one less chromosome than chimps. Two of the great-ape chromosomes are fused together in humans. So while most of the DNA is identical - the way it's glued together isn't. But that doesn't make it completely impossible. Humanzee explains all of the horrible details. It's widely assumed that humans and Neanderthals would have been able to interbreed. SteveBaker (talk) 04:33, 14 February 2009 (UTC)

The degree of identity between human and chimpanzee genomes is not easy to estimate. Figures like the one to which you refer ("98.77%") are fraught with serious problems, as discussed in many papers including this one [7]. The differences go much deeper. --Scray (talk) 05:03, 14 February 2009 (UTC)

Representing the similarity of genomes in term of percentages is very, very misleading. Yes, we share about 98.4% of our genome with chimps, but we also share about 90% with mice and 50% with bananas[8]. First, as mentioned above, percentages don't take into account structural chromosomal differences (fusions, inversions, and the like) that may exist, making interbreeding difficult or impossible even between otherwise closely related species. Second, there is a great deal more information in a genome than just the genes themselves. One major example would be how the genes themselves are regulated: how strongly they are expressed, in which tissues they are expressed, and when. Complicating things further, altering a single base may result in a major change in how the gene product itself functions. One gene often given credit for providing humans the ability of language is FOXP2, which contains 3633 bases in its coding regions. The human and chimp versions differ by only 3 (0.008%) of those bases. Clearly, when it comes to genetics, a little difference can go a long way. – ClockworkSoul 06:26, 14 February 2009 (UTC)

Despite what SteveBaker said, the question of wheather Humans and Neanderthals could interbreed is still an open one and the lack of evidence that any interbreeding took place may indicate that interbreeding was not possible. The only honest answer is that we don't really know yet. Dauto (talk) 18:42, 14 February 2009 (UTC)

Regardless of whether "modern" humans tens of thousands of years ago and neanderthals had viable offspring, there is no reason to believe they did not have sex. Modern humans have been known to have sex with sheep, cows, donkeys, horses, dogs, geese and chickens. Kinsey found that 8% of men and 3.6% of women reported such sexual relations with animals. It strains credulity that early humans and neanderthals never danced the horizontal bop. Edison (talk) 14:39, 15 February 2009 (UTC)

And goats. Don't forget the goat. Very important. BrainyBabe (talk) 15:47, 16 February 2009 (UTC)

So did the Sudanese man and his goat-wife have any kids? Edison (talk) 16:43, 17 February 2009 (UTC)

From what I've heard (which may be very incomplete), the only attempt to find surviving Neander genes was to look for N. mitochondria in a sample of modern humans. The negative result suggests that interbreeding was rare, but doesn't establish that it never happened: the female-line descendants could have died out by chance. (Many family names, i.e. someone's male-line descendants, have died out in the few centuries since they were adopted.) —Tamfang (talk) 18:17, 18 February 2009 (UTC)

Or not died out, but just become rare enough that none were present in the sample. (If only a few dozen or a few hundred existed, they would be unlikely to be found...) 128.194.250.39 (talk) 06:53, 19 February 2009 (UTC)

Scientific name

Does the scientific name Cacops aspidephorus mean "bad-face shield-bearer", or is there a more subtle meaning I may have missed? And, if so, why did Williston call this animal "bad-face"? Thanks a lot to anyone who can help. --83.57.77.67 (talk) 07:41, 14 February 2009 (UTC)

Our article on Dissorophidae (which is the family from which Cacops comes) says that all dissorophidae had armored plates over their spines...which explains "shield bearer"...and it says that Cacops is specifically known for having a "relatively huge head". I'm not sure that "bad-face" applies - but I wonder whether "big-face" might not be a better translation? (I long ago forgot any latin I might ever have been taught). It's also possible that the discoverer found this dissorophidae and found that it fitted in with other species in that family - except that the head didn't fit the pattern of the other species. I suppose it's then possible that the head/face was considered "bad" because of that failure to match the other species in that family. SteveBaker (talk) 02:42, 15 February 2009 (UTC)

Your Latin wouldn't help even if you could remember it Steve, I do believe that is Greek. Aspis=shield. The Latin for shield is scutum. SpinningSpark 15:08, 15 February 2009 (UTC)

Mental illness and "colorful" writing

A few questions ago, SteveBaker wrote "(You can tell it's a crackpot site because it's using LOTS of color/italics/underlining)", and I knew (even before I followed the link) exactly what he meant. I've noticed the phenomenon in web pages, I've noticed similar things in flat-text fora (e.g. Robert E. McElwaine's tendency to RANDOMLY capitalize WORDS...) and my father once told me that the American Institute of Physics used to have a special category for crackpot letters they received written with a variety of different-colored pens. My question is: is this writing quirk associated with any particular mental illness? I'd think it would be a symptom of schizophrenia and/or thought disorder, but I haven't seen it actually listed as such. -- Speaker to Lampposts (talk) 09:12, 14 February 2009 (UTC)

I guess emphasis ("shout when argument is weak") takes all forms but you might be interested in the article about green inkers. Another tic is to pad out a erm, "certain articles" with excessive C-quotes. Julia Rossi (talk) 09:16, 14 February 2009 (UTC)

It seems to be quite common on Usenet for the crackpots to pad out their posts (often several, one after the other, crossposted, saying pretty much the same thing, as is the custom) with weblinks and random cut+pasted excerpts from websites which are seemingly unrelated to the topic of the screed. --Kurt Shaped Box (talk) 09:32, 14 February 2009 (UTC)

The best crackpot site of all time has to be Time Cube. A Quest For Knowledge (talk) 11:19, 14 February 2009 (UTC)

I second that. -Pete5x5 (talk) 01:16, 15 February 2009 (UTC)

Closely followed, of course, by stopabductions.com, a website claiming that telepathic aliens can be thwarted through the use of a telepathy-blocking helmet... *ahem* this is a quote from their testimonials section:

“I am happy to report that the Thought Screen Helmet has been performing beautifully! It’s been over six months now and NOT ONE INCIDENT! Aside from some of the naive neighborhood kids and their taunting it’s been a blissful period.”

This. Is. Insane. Also: see aliensandchildren.org , another (equally ridiculous) site run by the same person. Ilikefood (talk) 23:01, 20 February 2009 (UTC)

Alex Chiu and the 'Anus 100' guy deserve honourable mentions for their incomprehensibility and sheer dogged determination to defend their theories in the face of overwhelming criticism and ridicule. --Kurt Shaped Box (talk) 11:58, 14 February 2009 (UTC)

At first I thought you meant Frank Chu, with whom I've futilely attempted conversation. —Tamfang (talk) 18:22, 18 February 2009 (UTC)

Immortality devices! LOL. I love it! (Those are sentences that deserve exclamation points.) A Quest For Knowledge (talk) 17:37, 14 February 2009 (UTC)

I remembered the anus guy's name now, FWIW. Hiroyuki Nishigaki. Check out some of his musings/ramblings if you can find them online (his website seems to have gone now). His main theory (from what I could understand of it) combined 100-times-daily anal constriction with various other religious, spiritual, alien, pseudo-scientific or downright crackpot concepts to produce a truly (sometimes literally) incoherent wholeness. IIRC, he was also trying to encourage mentally ill people to stop taking their meds on Usenet - which would've been dangerous, if the guy didn't come across as *more* insane than everyone else there present. --Kurt Shaped Box (talk) 22:21, 14 February 2009 (UTC)

Children also tend to randomly write in multiple colors, so I associate that with "immaturity". There are places where color is used to actually mean something, though, like Bibles which use red text for supposed quotes from Jesus. StuRat (talk) 14:27, 14 February 2009 (UTC)

Ding! Ding! We have our explanation! --Kurt Shaped Box (talk) 22:07, 14 February 2009 (UTC)

And don't forget about exclamation marks ! Every sentence should end in at least one, no matter how dull ! It is now 9:30 AM ! And, when the reader gets used to every sentence ending in an exclamation mark, it's time to escalate to several !!!!!!!!! StuRat (talk) 14:31, 14 February 2009 (UTC)

When I was a lad, many of the newspaper comic strips ended every sentence (except questions) with a bang. Is that still true of any? —Tamfang (talk) 18:34, 18 February 2009 (UTC)

This will go way over your head as my research into this area is decades past general scientific understanding (let alone that of lay people) but here goes: the reason crackpots write with different colors is because they are approaching science with their right brain hemisphere. It is also the reason they fixate on the intuitive meaning of scientific terms (i.e. the impression the term would make before you ever learn what it means), with a seeming inability to internalize the technical definition. This is a style of thinking -- its more useful in some areas of life and science and less useful in others. That's all I will say, because my research on this subject is so far ahead of science that trying to explain it to you in a Reference Desk response would be hopelessly quixotic. —Preceding unsigned comment added by 82.120.236.246 (talk) 15:22, 14 February 2009 (UTC)

Come on, everyone knows any sentence containing the phrase "far ahead of science" HAS to end with an exclamation mark! --Tango (talk) 15:39, 14 February 2009 (UTC)

Then I would have had to say "the reason crackpots write with different colors is because we are approaching science with..." —Preceding unsigned comment added by 82.120.236.246 (talk) 15:53, 14 February 2009 (UTC)

I don't know why they do this - but it's a dead giveaway when you open a web page that looks like that. As for excessive exclamation marks, it helps to pretend that each "!" is really a "?". I doubt that this is a mental illness per-se - but there is certainly a correlation between crackpot theories and tasteless web sites. However - correlation is not causation. SteveBaker (talk) 19:22, 14 February 2009 (UTC)

I guess that depends on whether you count being a complete idiot as a form of mental illness. I've never been quite sure how you distinguish between "learning difficulties" and "stupidity". In cases where there is a definite cause for the learning difficulties, it's pretty simple, but in other cases I'm not sure there actually is a distinction. --Tango (talk) 20:07, 14 February 2009 (UTC)

Another common 'red flag' for these quacksites seems to be the overuse of mid-90s-web-style animated gifs and stock clipart. Has anyone else ever noticed that? --Kurt Shaped Box (talk) 22:38, 14 February 2009 (UTC)

Pretty much everything about their webpages boils down to them being stuck in the mid-90s (you forget to mention <blink> and <marquee> tags!). I have no idea why... --Tango (talk) 23:25, 14 February 2009 (UTC)

They like <center> tags too. SteveBaker (talk) 23:45, 14 February 2009 (UTC)

The use of several different fonts, bold/italic styles and text sizes within the same paragraph/block of text too. I wonder if they're deliberately trying to give the impression to their readers that they were chewing the keyboard when working on the site? --Kurt Shaped Box (talk) 00:44, 15 February 2009 (UTC)

Another dead giveaway to me for a crackpot letter is its ending. It's usually "Think about it!"

Think about it!. Bunthorne (talk) 21:48, 14 February 2009 (UTC)

Thought-terminating cliché#Non-political examples. Most of these websites will also have a colourful array of fallacies within them (no pun intended). --Mark PEA (talk) 12:29, 15 February 2009 (UTC)

Yes, such as circular logic. The reason that circular logic tells us these sites are run by crackpots is that, as previously established, circular logic tells us these sites are run by crackpots. StuRat (talk) 17:31, 15 February 2009 (UTC)

I guess you are arguing that there is no evidence that the sites are run by crackpots, but the definition of crackpot could be "someone who uses colourful writing and talks crap", which would mean it is not circular logic. Although hasty generalization is still possible. --Mark PEA (talk) 18:28, 15 February 2009 (UTC)

Is there any way to repair a cracked DVD?

I have a dual-layer DVD-Video disc with a full-thickness crack running from the centre, to about 1cm into the data area. Is there any possible way that I could either fix the disc, or even just render it readable for long enough for me to make a copy?

I guess that the answer's going to be 'no' - but hey, it's worth a try if it saves me having to buy the movie again... ;) --Kurt Shaped Box (talk) 13:04, 14 February 2009 (UTC)

If it's full-thickness, then probably not (surface scratches are another matter). Almost certainly not easily (you might be able to pay a specialist company lots of money to get the data off, like you can with broken hard drives, but I doubt that's worth it). You might be able to get the DVD replaced for free (or maybe for a small admin/p&p fee) from the manufacturer, though - if all the DRM and EULA stuff is to be believed, what you bought wasn't the DVD but rather a license to the content that is on the DVD, so it makes absolutely no sense for them to charge you for the content again just to replace the DVD (of course, sense doesn't really come into it!). Try asking at wherever you bought it. --Tango (talk) 13:12, 14 February 2009 (UTC)

I wouldn't count on them replacing it for free. They conveniently either say you are buying the disc or the content on it, whichever way will get them the most money. Can we get free DVDs by turning in old VHS tapes ? I doubt it. StuRat (talk) 14:22, 14 February 2009 (UTC)

DVDs usually contain additional content that wasn't on the VHS version, so almost certainly not. --Tango (talk) 15:45, 14 February 2009 (UTC)

Even if it isn't, the idea that the content and the medium are totally separable is certainly not part of the EULAs. --98.217.14.211 (talk) 00:39, 15 February 2009 (UTC)

As for the original Q, I'd guess that there is some way you could "fix" the DVD. By this I mean glue it together so it won't fall apart when played. However, the data in the vicinity of the crack will still be lost. This is merely annoying for music and video, but will make any program on the disk completely unusable. StuRat (talk) 14:22, 14 February 2009 (UTC)

It may be worth writing to the publisher. I did this once with a similarly damaged CD and they replaced it for the cost of postage after I had sent them the damaged original. -- SGBailey (talk) 18:41, 14 February 2009 (UTC)

There's some stuff you can buy to repair plastic eyeglass lenses that might work to repair the plastic part. The data as Stu said is another matter. Try opticians for the chemical (comes in a very small tube.) I came across it once and stocked up. I haven't seen it since. 76.97.245.5 (talk) 22:36, 14 February 2009 (UTC)

Have you tried playing it? DVDs have a lot of error correction and it may still be playable. In that case (if you can break the copy protection, which is possible) you could copy it to a new disc. --Chetvorno^TALK 07:49, 15 February 2009 (UTC)

Let me say right off that there is no way you'll be able to 'repair' the disk. Forget it - it's not gonna happen. Even if it did work, the extra weight of the glue on one side and not the other would unbalance the drive and either prevent it from playing or damage the bearings in the DVD drive. However, I would expect the error correction systems to be able to recover data from the DVD so it should play OK providing that's the only damage. If it also has some fine scratches, dust or fingerprints then there may just be too many errors for it to recover from. But there is another problem. A crack that goes all the way through the disk will have a very good chance of spreading and eventually causing the DVD to shatter while it's spinning. I would STRONGLY advise against playing it in a computer DVD drive because those can spin a lot faster than a Video-only DVD player and if a DVD comes apart at high RPM, it can do some serious damage. (I refer you to a Mythbusters episode where they tried playing various optical disks to make them fly apart). The trouble is that the other advice I'd like to offer would be to suggest 'ripping' the movie off of the DVD and writing it onto a blank disk using your computer...but with the risk of the disk shattering when you do that...I'm beginning to think that this is actually a bad idea. IMHO, you should first contact the company that made the disk and ask for a replacement. I think they'll probably give it to you - although they might want to charge for shipping & handling. SteveBaker (talk) 17:00, 15 February 2009 (UTC)

so cola is TERRIBLE for your teeth. Does swishing with water immediately afterwards help?

I heard cola is terrible, horrible for your teeth. Drinking thru a straw helps, but I wonder: would swishing your mouth thoroughly with clear water immediately afterwards also help any? I am not asking for medical advice! —Preceding unsigned comment added by 82.120.236.246 (talk) 15:09, 14 February 2009 (UTC)

Saying "I am not asking for medical advice" doesn't make it true. This is quite obviously a request for medical advice. Ask a dentist. --Tango (talk) 15:43, 14 February 2009 (UTC)

Yes, actually, it does -- saying, in bold, "I'm not asking for medical advice" means I'm not asking for medical advice. —Preceding unsigned comment added by 82.120.236.246 (talk) 15:53, 14 February 2009 (UTC)

No, it doesn't. You're asking for something which requires expert medical understanding and could easily lead you to behaviors which are not safe. Appending a contradictory statement to the end of it doesn't change that fact. It just makes your bolded statement false. --98.217.14.211 (talk) 00:42, 15 February 2009 (UTC)

Cola is no worse for your teeth than other soft drinks. For healthy teeth it's best to avoid drinks with added sugar. Rinsing your mouth thoroughly might remove some of the sugar.--Shantavira|^{feed me} 16:03, 14 February 2009 (UTC)

The carbonic acid, citric acid and phosphoric acid isn't good for them. There are plenty of soft drinks that aren't anywhere near as acidic. There are also plenty of soft drinks that aren't high in sugar. --Tango (talk) 16:30, 14 February 2009 (UTC)

Then what are you doing? --Tango (talk) 16:26, 14 February 2009 (UTC)

This possibly? SpinningSpark 16:33, 14 February 2009 (UTC)

Aside from everything else: Drinking through a straw WILL NOT AFFECT chemical or biochemical behaviour of a substance! That is a very frequent misinformation. (Assuming you arent drinking harzardous chemicals which actually react with the plastic) --91.6.7.232 (talk) 17:58, 16 February 2009 (UTC)

Don't be silly. Drinking through the straw isn't supposed to chemically change the drink. No one in the world believes that. The point is to stop the soda from repeatedly eroding your front teeth.

Who knows how much difference that makes, but some dentists seem to believe that it is significant. 21:10, 17 February 2009 (UTC)

Verifying that a CO detector works

Is there an easy and safe way to verify the correct functioning of a CO detector? --173.49.17.152 (talk) 19:33, 14 February 2009 (UTC)

Does it have a "test" button? That will verify that the batteries aren't flat. As for verifying that it actually detects CO, I'm not sure... you could try holding it up to your car's exhaust pipe while it's running (outside, otherwise you'll end up giving yourself CO poisoning while testing your CO detector, and that would just be silly!). But really, I think if you have reason to doubt your CO detector is working, you should just get a new one. It's not worth the risk. --Tango (talk) 20:05, 14 February 2009 (UTC)

That, of course, would be the easy answer. From what I understand, CO detectors have a finite lifetime, but some fail earlier than others. Although early replacement would be a (somewhat expensive) solution, it would still be nice to be able to verify that a CO detector is actually working even when its age suggests that it should. Like you pointed out, the test button merely tells you that the battery is not dead. With a smoke detector, you can use a smoke pencil to verify that it does detect smoke. I was hoping that there's a similar solution for CO detectors. --173.49.17.152 (talk) 20:23, 14 February 2009 (UTC)

Some CO detectors have self-diagnostic modes which give a more detailed test than simply "is the battery ok". For example, some have a test involving lighting a cigarette near to it, while in the test mode. The instructions supplied with the detector will have further information. DuncanHill (talk) 20:34, 14 February 2009 (UTC)

If you have cigarettes around, you probably don't need the detector to know you're getting too much CO. What are normal people supposed to do? Run out and buy cigarettes just to test the detector? --Trovatore (talk) 21:35, 14 February 2009 (UTC)

Normal people already have cigarettes available, we just prefer not to waste them testing electronic equipment! DuncanHill (talk) 21:38, 14 February 2009 (UTC)

Ah, read the manual... Can we pretend that my first recommendation? --Tango (talk) 20:36, 14 February 2009 (UTC)

(ec) There may well be, I don't really know how CO detectors work (although, knowing me, I will now compulsively find out!). I do, however, know how nasty CO poisoning is, which I why in the absence of a definite answer to a contrary my advice is to risk wasting money rather than risk wasting your haemoglobin. --Tango (talk) 20:36, 14 February 2009 (UTC)

I could be wrong but I'm doubtful that any manufacturer (at least in any country with strong and enforced consumer protections) would give device intended to be life-saving a lifespan that's likely to result in a substanial number of devices 'expiring' before then. In other words, if the manufacturer says you should replace the device in 6 years (random guess) only a tiny number of devices are likely to fail before then (and it not be detected by the self diagnostics). So it's not so much replacing the device early as on time Nil Einne (talk) 05:08, 15 February 2009 (UTC)

Try a smoldering incense stick. This will work for smoke detectors too. If it sounds the alarm, OK. If it doesn't, the stick is either not emitting enough CO or the detector is not working. A smoldering incense stick is also useful for revealing drafts, and does not leave the unpleasant smell of a cigarette. Check ebay for sources of incense. – GlowWorm. —Preceding unsigned comment added by 98.17.32.201 (talk) 23:46, 14 February 2009 (UTC)

Or ask your friendly neighborhood pyromaniac for assorted substances of ambiguous legality :-P Ilikefood (talk) 23:03, 20 February 2009 (UTC)

Mysterious Dead

Recently someone, who in turn got it from anonymous source, sent me a photograph of a dead animal that seems to be something between a bear and a dog. I could not find any refernece on Wiki. I have verified that actually the picture comes from a blog, but that damned blog has only pic and no explanation. Since I do not have the copyright and don't know who the author is, I cannot put it on Wiki. Instead I am putting it on my website : http://www.khurmi.com/sqyy.jpg. Courageous Wikipedias are urged to have a look at it and tell me what the hell it is. Please reply on my talk page.  Jon Ascton  (talk) 21:45, 14 February 2009 (UTC)

We'll reply here, we always do. --Tango (talk) 21:47, 14 February 2009 (UTC)

It's not a great picture, most of the nose is covered by grass, which doesn't help. It looks like a dog to me, though (probably an unusual crossbreed). --Tango (talk) 21:48, 14 February 2009 (UTC)

Looks like a black Chow-Chow mix. Compare [9]. Poor dog. 76.97.245.5 (talk) 22:25, 14 February 2009 (UTC)

(For some reason, the OP deleted this question and all of it's answers. Please don't do that.) SteveBaker (talk) 23:40, 14 February 2009 (UTC)

Whatever it is, it's been photoshopped pretty significantly. If you zoom in on the thin blades of grass over the animal's head, you can see that quite clearly. All bets are off. It could be anything - or nothing. SteveBaker (talk) 23:33, 14 February 2009 (UTC)

I don't see it... what am I looking for? --Tango (talk) 00:07, 15 February 2009 (UTC)

I don't see anything like canine teeth. And it's blue?? Cuddlyable3 (talk) 00:12, 15 February 2009 (UTC)

It's not just that - but look at the 'specular' highlight on the animals' black nose...the reflection is blue...it should be white. If you blow up the region around the grass blades, there are whole pixels of green and whole pixels of blue - and other than the color bloom that's caused by JPEG encoding, there is no soft average of grass-color and fur-color. There is no camera data in the EXIF data. It's eyes are blue too...it's a crappy photoshop job - it just screams it. SteveBaker (talk) 01:49, 15 February 2009 (UTC)

That's not a crappy Photoshop job. This is a crappy Photoshop job. The image under discussion is either a pretty good Photoshop job or real. The blue tint is presumably due to poor color balance in the camera, which has no analogue in computer graphics—and anyway, the light on the nose looks more diffuse than specular to me. The image was clearly cropped and probably resized (I don't think any digital camera takes photos in that aspect ratio), which would explain the lack of EXIF data. The green-blue boundaries don't look suspicious to me. Read the story of the Lumber Car as a cautionary tale. It looks implausible on the face of it, so people pore over the image for evidence of Photoshopping, and they find it, because most images of this (rather poor) quality have features that can be ambiguously interpreted as Photoshopped. That way lies conspiracy-theorist madness. -- BenRG (talk) 15:23, 15 February 2009 (UTC)

I've seen the 'lumber car' pictures before - they didn't strike me as photoshopped at the time - and it's good to hear that they were genuine. In order to discover whether an image might have been tampered with, you have to look at the subtle signs of color, lighting, shadows, etc. Those are all as they should be in the lumber car picture - but they most certainly AREN'T right in this one. SteveBaker (talk) 16:48, 15 February 2009 (UTC)

Diffuse light takes on the color of the object (which in the case of the nose - is black) and reflects more or less equally in all directions - specular light is constrained to a region where the angle of the incident light is roughly the same as the angle of the camera to the object. In this case, the parts of the nose that are angled away from us are black - so there is little if any diffuse reflection going on - the bright spot is therefore a SPECULAR glint. Specular reflections take on the color of the light source (which would have to be blue in order to make a blue splotch on a black object). The only way a 'shiney' spot on a black object could be blue would be if the photograph was taken in blue light - or if the camera was not registering red and green very well. However, the grass is green and there are other white things in the scene - ergo neither the light nor the camera was favoring green. It WAS tampered with. If there was excessive blue balance in the camera then you'd wouldn't have such bright green grass. I have some considerable experience with computer graphics, lighting and coloring and I can assure you that image was messed around with by someone who didn't know how to do it well. As for conspiracy theories - which is more likely - that someone (inexpertly) messed with the photo - or that there really are blue dog-bear hybrids running around loose unknown to modern science? SteveBaker (talk) 16:43, 15 February 2009 (UTC)

NOW you're really extrapolating, Steve. The only evidence we have is of blue dog-bear hybrids lying on the ground looking dead. Did I miss the photo or other evidence of one running around? You really should stick to the 'facts'. ;-) --Scray (talk) 17:23, 15 February 2009 (UTC)

I realize that specular highlights in computer graphics are usually independent of the color of the object, but as our specular highlight article mentions, in real life it depends on the material—it's true of colored plastics but not colored metals. Whether it's true of rhinariums I don't know, but anyway it makes no difference because that's obviously not the origin of the blue tint here. Surely you've noticed before that black objects in photographs very commonly have a blue tint. Here's a great example from the rhinarium article—would you say that image was photoshopped to make the monkey look blue? I don't think the blue tint in this image was even an issue until you and Cuddlyable3 brought it up. The original poster wasn't asking about a mysterious blue animal, but about a mysterious seeming hybrid of different species. I assume that he interpreted the blue tint the same way I did, as a color-balance problem. It is, as I said, very common and I'm amazed you haven't noticed it before. This is the most similar image I could find in a quick search of the Commons. Does that also have the sudden green-blue transition that you were talking about (look at the forelegs)? Here's another example of a blue nasal highlight (although I admit I'm linking it more because it's friggin' adorable than because I think another example is needed).

Maybe I'm missing something, but your suggestion that a blue tint might mean that "the camera was not registering red and green very well" makes me think you don't understand real-world color at all. In computer graphics white is just an equal combination of red, green and blue, but in real-world imaging it's a considerably more complicated concept. The world isn't sRGB, and our eyes don't see in sRGB. There've been a bunch of good color-vision threads in the Ref Desk—they're worth a(nother) look. Also see color balance, white point, CIE 1931 color space, etc. -- BenRG (talk) 22:18, 15 February 2009 (UTC)

How fair is a coin?

How fair is a physical coin? I mean, what by percentage does it favor heads or tails, when flipped in the standard way -- it must by SOME amount, since there must be more material on one side than the other. Also, how many standard deviations away from the average would this favor be? Thanks! —Preceding unsigned comment added by 82.120.236.246 (talk) 21:57, 14 February 2009 (UTC)

Slightly different, I know, but careful analysis suggests that a coin will land the same way it started about 51 percent of the time. In reality, this probably favours heads. The weighting issue - which would differ based on the coin used - pales in comparison to human jitteriness (which is what actually introduces the randomness), I'm afraid. - Jarry1250 ^{(t, c)} 22:18, 14 February 2009 (UTC)

Is there really a standard way to flip a coin? It can't be completely standardised or the result would be predictable. Cuddlyable3 (talk) 00:10, 15 February 2009 (UTC)

The coin will always favour the side which it was flipped from. This is because the spin is unbiased only if the coin rotates about an axis that is orthogonal to its normal. Otherwise it favours the face starting on top. There are a lot of recent studies that suggest this bias is indeed close to 1%. (Too lazy to find any links). —Preceding unsigned comment added by 99.255.228.5 (talk) 00:44, 15 February 2009 (UTC)

Assuming that each coin flip has the same bias and is independent of all other coin flips, you can correct the bias using some unbiasing procedure. Here's one way to do that:

1. Starting with the head side up, flip the coin once.
2. Starting with the head side up (again), flip the coin a second time.
3. If the two coin flips come out different, take the result of the first coin flip.
4. Otherwise, start over.

This will work so long as the coin flips don't come out the same way 100% of the time. --173.49.17.152 (talk) 17:18, 15 February 2009 (UTC)

You don't even need that many steps - just one:

1. flip twice until you get different results then use the first

Tested like this

C:\>perl -we "$numHeads = 0; $numTails = 0;
   for (1..1000000) {
      while (
         ($first_is_heads = (int rand 10? 1:0)) ==
         (int rand 10? 1:0)
      ){};
   if ($first_is_heads){$numHeads++} else {$numTails++}
   }
   print qq/$numHeads heads - $numTails tails\n/"
500014 heads - 499986 tails

-- good enough for me!

Bias reduces the probability of getting two different results in succession from the ideal 50%. However the bias that affects every individual flip still affects the coin (first) that you choose. A way of reducing the bias is to toss a second coin to choose whether to take the first or second flip of the first coin. Cuddlyable3 (talk) 18:34, 15 February 2009 (UTC)

Actually most coins are heavier on one side than the other.--GreenSpigot (talk) 00:03, 16 February 2009 (UTC)

I'm not so sure I like this "bias preconditioning." I'm not an expert in statistics, but the way I read these prior responses goes something like this: "We have a (semi) non-random set of numbers. We perform a conditioning algorithm. The result is a more-random set of numbers." That would be fine (pseudo-random number?) except it sounds like the algorithm suggested above (only accept the toss if the value changed since last time...) is just a high pass filter. This won't eliminate all bias, it will just eliminate low-frequency biases. Maybe I'm mistaken, maybe the definition of randomness, pseudorandomness, and unpredictability are all worth checking again... Nimur (talk) 16:10, 16 February 2009 (UTC)

Here's an explanation of why the unbiasing procedure doesn't work, not using the concept of frequency. Consider our biased (to fall "heads", say) coin is tossed many times in its lifetime and our first toss is an entry into the stream of results. The bias means we are more likely to enter into a string of recurring heads ...HHHHH... than of tails. Therefore as we repeat tosses, the first time the algorithm finds two different successive results will be at the end of this string i.e. ...HHHT. Encountering TTTTH is less likely. Therefore the first toss selected by the algorithm is still more likely H than T, due to the bias.

Using a second coin as I described reduces but does not eliminate the bias. Tossing an infinite number of times would be the only way to eliminate bias. Cuddlyable3 (talk) 13:21, 18 February 2009 (UTC)

No, using the approach described above ("always flip twice in the same manner, repeat until the results are unequal, then pick the first") will produce heads and tails with exactly 50%. That is a well-known result from probability theory, and it holds for any biased coin as long as the results of the two coin tosses are independent. Note that you have 4 possible results, HH, HT, TH, TT. You throw out HH and TT, leaving you with TH and HT. The probability for the first sequence is P(H)*P(T), the one for the second P(T)*P(H), and since * is commutative, they come out the same. Note also that you do not throw until you detect a change - you always throw pairs. --Stephan Schulz (talk) 15:57, 22 February 2009 (UTC)

Energy vs mass

Does something have energy because it has mass? Or does something have mass because it has energy? Or do the two exist because of some higher attribute?128.163.224.222 (talk) 23:02, 14 February 2009 (UTC)

Both, the two are really just different manifestations of the same thing. Einstein's famous equation, E=mc², tells us how they are related. The c² part is really just there to convert the units - from kilograms to joules or whatever (just like you have to multiply by 2.54 to convert inches to centimetres, you have to multiply by 3x10⁸ to convert kilograms to joules). Essentially, energy and mass are equal. We often talk of rest mass, which is the mass something has when it doesn't have any other energy (what gives things their rest mass is something of an open question, see Higgs mechanism if you want the technical details of the most popular theory). When you move an object you give it kinetic energy, that results in it having a greater mass (we call it relativistic mass). It's that greater mass that makes it impossible to accelerate something to the speed of light - as it gets faster and faster and gets heavier and heavier and takes more and more energy to accelerate it, it would take an infinite amount of energy to get it all the way to the speed of light. Does that help at all? --Tango (talk) 23:22, 14 February 2009 (UTC)

In ordinary experience mass and energy are independent properties that co-exist. Only extreme cases such as nuclear fusion or fission, such as in the sun or A- and H-bombs, demonstrate that one can convert into the other. Whether there is some higher attribute than these in the universe sounds like a religous question. Cuddlyable3 (talk) 00:06, 15 February 2009 (UTC)

It's a perfectly reasonable scientific question - if two things are related, it's sensible to ask if perhaps they have a common cause. --Tango (talk) 00:16, 15 February 2009 (UTC)

Electric fields and magnetic fields can be converted into one another—because they are basic components of a single electromagnetic force. Asking the underlying connections between related quantities is one of the fundamental physics questions, nothing to do with religion. --98.217.14.211 (talk) 04:02, 15 February 2009 (UTC)

The illustration I like is that a hot cup of coffee is slightly heavier than it is when it has cooled off. --Chetvorno^TALK 07:57, 15 February 2009 (UTC)

Just because we can write down an equation which relates two quantities by nothing but a constant of nature does not mean that these two quantities are the same. In fact, energy and mass are two different things, in relativistic as in Newtonian physics. That's relatively easy to see mathematically (energy is the time-component of a particle's four-momentum, mass is the four-momentum's invariant length, hence the full connection is $E^{2}-p^{2}=m^{2}$, where I have set c=1), and somewhat harder to describe in words. I like to put it as follows: Energy (along with its companion, momentum p) describes how a particle is moving. This should make it obvious that the energy of a particle depends on the reference frame in which it is measured, as is the case for kinetic energy in Newtonian mechanics. The mass of a particle puts constraints on the motion that is possible for that particle (because the relation $E^{2}-p^{2}=m^{2}$ has to be fulfilled). Famously, particles with zero mass always travel at the speed of light, particles with mass have to travel at less than the speed of light. $E=mc^{2}$ is a special case of the relation quoted above, and is valid in the particle's rest frame. It says that even when a particle is at rest, we have to attribute an energy (numerically equal to its mass, multiplied by c², although that's just a matter of the units we use) to it, something that is not the case in Newtonian mechanics. --Wrongfilter (talk) 12:42, 15 February 2009 (UTC)

That's rest mass, of course. The now unfashionable relativistic mass is just the same thing as energy. Algebraist 13:58, 15 February 2009 (UTC)

Indeed. It's unfashionable because it isn't actually very useful when doing calculations, and whatever. It is, however, quite a good way of thinking about it when you are trying to get your head around why the speed of light takes infinite energy, and related concepts - that's why I answered the OP's question in terms of it. --Tango (talk) 15:01, 15 February 2009 (UTC)

Above, it was mentioned that "Only extreme cases such as nuclear fusion or fission, such as in the sun or A- and H-bombs, demonstrate that one can convert into the other". This is a common fallacy! A 25 keV cathode ray such as the one in your old cathode ray tube television could easily impart enough potential energy to introduce a mass artifact on the electrons as it hurtles through the unit. This can and does introduce a noticeable shift in the trajectory of the beam, which must be compensated for by the controlling electronics, else the raster scan doesn't work properly. (Reference: Cathode Ray Tubes, R. Casanova Alig, Sarnoff Corporation, 1999). "The electrons leave the gun at speeds of 5% or more of the speed of light. This speed is high enough for the theory of relativity to change the electron path perceptibly from that expected from Newtonian physics. The CRT is unusual, perhaps unique, among household objects, in that relativistic effects are significant." Perhaps mass-energy equivalence is not such an extreme case after all! Nimur (talk) 16:18, 16 February 2009 (UTC)

Runaway propeller

I am listening to A Case for Dr Morelle on the BBC iPlayer, and an aeroplane in the story suffers from a "runaway propeller". What might this be? DuncanHill (talk) 23:52, 14 February 2009 (UTC)

If the governor associated with a constant-speed propeller fails, the propeller blades may feather to an extremely fine pitch. This will sharply reduce the load on the engine, and – unless corrective action is taken immediately – the engine may redline. Damage can occur to the overspeed prop itself, to the engine, or both. (A rough analogy from the driving world — imagine driving at highway speed and suddenly shifting down into first gear.) TenOfAllTrades(talk) 04:05, 15 February 2009 (UTC)

If the engine speed is constant and the pitch is automatically controlled, what is left for the pilot to control? How does he adjust the thrust? —Bromskloss (talk) 12:26, 15 February 2009 (UTC)

The name 'constant-speed prop' is a tad misleading. It shouldn't be read to mean that the prop maintains a constant speed at all times during the flight; as you've quite correctly surmised, that would leave no obvious way to control thrust. Instead, the pilot has a second control in the cockpit (usually adjacent to the throttle) which allows for selection of the target engine speed (RPM). On takeoff and climb, the pilot will choose a high speed, corresponding to finer prop pitch and greater power. During level flight, the pilot will move to a lower speed, corresponding to greater prop pitch, lower engine speed, and better fuel economy.

Here are a couple of links that go into a bit more detail: [10], [11]. TenOfAllTrades(talk) 14:16, 15 February 2009 (UTC)

Aha! Thank you. —Bromskloss (talk) 10:58, 16 February 2009 (UTC)

• Excellent, many thanks! DuncanHill (talk) 15:46, 15 February 2009 (UTC)

Can we create giant insects like those that lived during the Carboniferous period?

During the Carboniferous period, insects could grow much larger than today due to the high oxygen levels. So, why can't we breed insects under high oxygen conditions and select for size, or use genetic manipulation techniques to create large insects? Count Iblis (talk) 23:57, 14 February 2009 (UTC)

We probably could if we really wanted to. I'm not sure selective breeding would get us anywhere near those sizes in a reasonable amount of time, but genetic engineering might be able to. --Tango (talk) 00:04, 15 February 2009 (UTC)

The American cockroach can grow to amazing size. (Not quite big enough to saddle, despite the common saying.) Which leads to the question what you'd do with your giant bug and what would it feed on? There may be some use in the entertainment industry (Godzilla vs Ibis bug). Our next problem, though, is going to feed the steadily growing human population, not entertaining them. If your bugs were edible, could be fed on something that would not have a negative net food value it might be worth the resources expended to create and maintain it. All that would be left to do would be to train humans not to get the creeps when they find out what's in that hot dog. But then there are cultures who eat bugs.76.97.245.5 (talk) 02:24, 15 February 2009 (UTC)

There is a perfectly extant and very large terrestrial arthropod, the Coconut crab. It's not an insect, and its respiratory system is quite different from that of the modern insects; but it is still an arthropod (so same basic body arrangement, exoskeleton, open circulatory system, etc...). Does it fit your bill? Or are you rather asking about "breeding back" Meganeura and such? --Dr Dima (talk) 03:54, 15 February 2009 (UTC)

Probably a major reason those insects were able to grow bigger was because there was more oxygen in the air. Which is good for the rest if us as you'll have to keep them in a special enclosure. I've seen the effects when such creatures are released.:) Dmcq (talk) 12:25, 15 February 2009 (UTC)

Yes, I think that is understood to be the primary reason they were bigger. The OP said as much. --Tango (talk) 15:03, 15 February 2009 (UTC)

We still have a few moster flying insects around: Attacus atlas the Atlas Moth for instance, and Ornithoptera alexandrae the Queen Alexandra's Birdwing butterfly. Although neither of them comes anywhere near Meganeura's 30 inch wingspan. SpinningSpark 16:13, 15 February 2009 (UTC)

February 15

How do I genetically engineer the world's best sports team?

I was thinking thru cloning. Like chip some skin off our top baseball and football players and thier offspring's genetic code would be the same, right? So they would have an excellent chance of being athletic in a superior way, I take it? Then in about 20 years,-"And now,- presenting the only 162-0 baseball team in history,-". They would then take the field proudly and win another 27-0 shutout. Is this dream possible?Baseball and and and Popcorn Fanatic (talk) 00:17, 15 February 2009 (UTC)

How do you genetically engineer the world's best sports team? You begin by getting a degree in genetic engineering and hope that by the time cloning techniques are advanced enough to allow such a thing, that it is legal to do so in whatever country you plan on cloning your humans. In addition, you also need to make sure that for whatever sport you plan on having your players compete in, that cloned humans aren't banned similar to doping. There's also the question of whether your human clones will actually want to play for you and not other teams. Finally, if you plan on having your players compete in a professional league, you may find it useful to buy a franchise. But be forewarned that such franchises are cost-prohibitive. The Chicago Cubs, for example, are currently being sold for $900 million. A Quest For Knowledge (talk) 01:18, 15 February 2009 (UTC)

You may also wish to consider what makes you enjoy watching your team win. Is it the elegance of each batter's swing and the movements of the catchers (sort of like ballet?) or is it the uncertainty of the outcome of the game? A majority of spectators would abandon the game if your team so far outperforms other teams that the outcome is a given. So your franchise would go broke and your perfect players would have to go work in jobs they weren't engineered for. 76.97.245.5 (talk) 02:04, 15 February 2009 (UTC)

Your clone breeding project comprises a violation of Equal opportunity that not even eugenicists contemplate, and which would raise issues of medical ethics and legality in athleticsCuddlyable3 (talk) 18:17, 15 February 2009 (UTC)

speeding up human gestitation

is there any way to speed up the 9 months? how about in non-humans? —Preceding unsigned comment added by 82.120.236.246 (talk) 00:52, 15 February 2009 (UTC)

It seems very unlikely. Any effort to mess around with the cell division rates would likely screw up the development in one way or another. Perhaps you could do it in VERY primitive organisms - but not in 'higher animals'. SteveBaker (talk) 01:44, 15 February 2009 (UTC)

That's only if you want the newborn to be normally developed, of course. It's easy enough to induce birth early if you don't mind an underdeveloped baby. Algebraist 02:53, 15 February 2009 (UTC)

You could always have nine women work on one baby, they should be able to get it done in about a month.--OMCV (talk) 02:56, 15 February 2009 (UTC)

You, sir, should work in management. You would go far. -- Captain Disdain (talk) 09:06, 15 February 2009 (UTC)

As far as non-humans go, in viviparous reptiles it is possible to reduce the gestation length by increasing the ambient temperature, up to some point. For mammals, esp. placental mammals - I doubt it. --Dr Dima (talk) 04:18, 15 February 2009 (UTC)

Travel in a spaceship and come back. You will notice time dilation. But don't go too far or too fast or you'll miss a birthday or few.Cuddlyable3 (talk) 17:51, 15 February 2009 (UTC)

Most non-humans already gestate in fewer or more than 9 months, presumably for their own good reasons. Cuddlyable3 (talk) 17:54, 15 February 2009 (UTC)

An unfortunately serious answer follows. By definition, a human baby that is born early is a preterm birth and will probably suffer from a large number of mild to serious medical complications, mostly relating to underdeveloped systems. Low birth weight is already a problem, and accelerating the birth to an even younger gestational age would severely increase the numerous accompanying conditions, infant mortality, and long-term problems like cerebral palsy, mental retardation, and other developmental disorders. Speeding up a human birth would have serious medical ramifications. Nimur (talk) 16:37, 16 February 2009 (UTC)

Yellow Sodium Light

Hello. Why is yellow sodium light the reference point in determining refractive indices? Thanks in advance. --Mayfare (talk) 05:13, 15 February 2009 (UTC)

Until an expert comes along, all you'll have is an educated guess. Yellow is kinda in the middle of the optical spectrum, the sodium output is very bright and unambiguous, and a yellow sodium light emitter should be readily available to any researcher (if nothing else, salt sprinkled in a Bunsen burner flame). Bunthorne (talk) 05:46, 15 February 2009 (UTC)

Sodium has a bit of info on the history. Also see Fraunhofer lines 76.97.245.5 (talk) 06:04, 15 February 2009 (UTC)

(EC) note by unambigious a key point may be it's fairly monochromatic Nil Einne (talk) 06:09, 15 February 2009 (UTC)

Indeed, the key point is that it emits light at one very specific and precisely known frequency. --Tango (talk) 12:39, 15 February 2009 (UTC)

Think about white light (eg sunlight). If you shine white light through a narrow slit and into a triangular slab of glass (a 'prism') it spreads out into a broad rainbow-like spectrum. It's hopeless to try to measure the angle the light was bent by because each of the colours got bent by a different amount. When you measure refractive indices, you are measuring that angle - and you get a different answer for different frequencies of light - so if you want to express it as a single number, you need a very pure light source. Sodium emits an almost pure yellow light - there are actually two frequencies but they are very close together. When you shine sodium light through a slit and into a prism, it doesn't split up - you get just two bright yellow lines (which are very close together) instead of a rainbow. It's easy then to measure the angle between the incoming and outgoing light and calculate a simple refractive index. If you used white light, you'd have to guesstimate (say) the middle of the fuzzy red/orange/yellow/green area and that would produce hopelessly inaccurate results. SteveBaker (talk) 15:25, 15 February 2009 (UTC)

For those who are interested, our article on sodium vapor lamps has a pretty picture of the low-pressure sodium emission spectrum. Check out the article or jump directly to the image: File:Low-pressure sodium lamp 700-350nm.jpg. (The image has been somewhat overexposed to make the other emission lines visible; this also causes the sodium D line to 'bloom' out a bit.) TenOfAllTrades(talk) 16:59, 15 February 2009 (UTC)

science/geology---tides!!!

If moon's attraction causes tides during nighttime,,, but why they not occur during daytime,, even if moon is present at that time? —Preceding unsigned comment added by Nilesh raj (talk • contribs) 06:39, 15 February 2009 (UTC)

Who says they don't? See the graph or the daytime pictures of the Bay of Fundy in the Tide article. Also, surfers don't go out only at night. Clarityfiend (talk) 07:35, 15 February 2009 (UTC)

There are definitely tides during the day. You usually get one high tide about every 12 hours (it's not exactly 12 hours since the Moon is orbiting as well as the Earth rotating - that's what causes the tides to be at different times each day). --Tango (talk) 15:11, 15 February 2009 (UTC)

Oh cool! I can use the word! Can I say 'syzygy'? Can I please? ... Oh good - thanks!

The tide is at it's highest when there is a syzygy - which is when the sun, moon and earth are all in a straight line. That happens during the day and during the night when there is either a total solar eclipse or a total lunar eclipse.

SteveBaker (talk) 18:40, 15 February 2009 (UTC)

How long have you been waiting to use that word? I think that was rather a stretch - the OP didn't ask about the maximum tides, just tides in general. --Tango (talk) 18:56, 15 February 2009 (UTC)

I was pointing out that not only do tides occur during the day - but the highest tides happen at midday during a...a...well, I'm just not going to say it now...you've taken ALL of the fun out of it. SteveBaker (talk)

Don't worry, Steve. He's just jealous because he didn't get to say 'syzygy'. — DanielLC 21:05, 15 February 2009 (UTC)

Lies, lies! --Tango (talk) 21:29, 15 February 2009 (UTC)

Oh, stop being such a syzy (gy whiz). Clarityfiend (talk) 02:00, 16 February 2009 (UTC)

At least you got to say it. I'm still waiting for my chance with Gegenschein. Algebraist 21:43, 15 February 2009 (UTC)

ENGINEER'S HELP NEEDED

HI FRIENDS

I AM RESIDING ON GROUND FLOOR OF A 3 STOREY APARTMENT.

THE PERSON RESIDING ON 1ST FLOOR ABOVE MY HOUSE HAS GOT HIS BATHROOM LEAKING IN MY HOUSE.

I TRIED HARD TO PURSUE HIM BUT HE IS NOT WILLING TO MAKE REPAIRS & ALSO IS NOT ALLOWING ME TO DO SO.

WHAT SHGOULD I DO?

I HAVE HEARD OF CHEMICALS(FOSROC HYDROPROOF)WHICH CAN HELP IN THIS BUT DONT KNOW MUCH.

ALL THAT CAN I DO IS TO MAKE REPAIRS FROM MY HOUSE ONLY, THAT IS, FROM THE BOTTOM ONLY.

IS THIS POSSIBLE?

PLEASE SUGGEST. —Preceding unsigned comment added by Saurabh85 (talk • contribs) 10:31, 15 February 2009 (UTC)

PS: On the user page of user:Milkbrath the OP mentions that he ad his / she and her neighbour are owners the apartments. --Cookatoo.ergo.ZooM (talk) 16:04, 15 February 2009 (UTC)

First of all, I suggest you turn off your caps lock key.

Secondly, to begin with, I suggest you contact the owner (or owners) of the building, or the building's manager, or some comparable party. Water damage can get very expensive if the problem isn't addressed, and it's likely to affect a lot of people other than just the people who live in the apartments in question. You don't mention whether you own the apartment or are renting; if you're renting, contact your landlord. The Wikipedia Ref Desk is probably not a good place to get help with this; you really should notify the building's owner or owner's.

Thirdly, I very much doubt that any chemical could fix this problem. I guess it might keep the water from your apartment, but it's not going to make the water go away: it's still going to be up there, leaking and doing damage. It will rot wood, rust steel, cause molds to grow, etc. You really need to move on this now; the longer you leave this, the more damage there will be. The leak needs to be fixed.

Fourthly, your neighbor is not only an asshole, but -- depending on where you leave -- probably also in a bad position legally; if he's aware of the problem but refuses to do anything about it, he's probably going to end up with a pretty hefty bill. We don't do legal advice, but let me put it this way: it's probably not a good idea for you to be aware of it and not report it to anyone, either. -- Captain Disdain (talk) 11:32, 15 February 2009 (UTC)

You state that you both are the owners of your respective apartments. As such, there must be an occasional meeting of owners to agree on communal matters where this problem should be discussed. Alternatively, as CD points out, there must be an appointed manager who looks after groundkeeping / general repairs / lift maintenance / etc.

You may also consider to call a plumber to determine the cause of the problem and to have an expert witness at hand. If nothing else helps, take a few photos of the damp patches / dripping water / mould / whatever and contact a lawyer. Finally, you may consider the benefits of having an apartment with an indoor swimming pool. --Cookatoo.ergo.ZooM (talk) 12:04, 15 February 2009 (UTC)

You don't need an engineer's help. You need legal help. Dmcq (talk) 12:06, 15 February 2009 (UTC)

Maybe it'll help you if you do a little experiment to visualize your problem. You'll need 2 or 3 slices of bread. Spread a good layer of butter or margarine on two of them. Turn your faucet to a slow drip and hold the piece of bread without any spread underneath. The bread will get soaked and sooner or later water will drip from the bottom. That's your ceiling now. Next turn one of the buttered slices upside down so that the side with the spread on it faces away from the faucet. Hold that one under the faucet. That's what you'd get if you tried to seal your ceiling from below. Not satisfactory, is it? The only way to solve your problem is to stop the leak or seal the ceiling from the top. (i.e. your neighbor's floor). If there still was a leak in his bathroom (e.g. from a leaky gasket or runoff from a shower curtain) the water would then collect on his floor and he could mop it up. That is the idea behind the products you read about. They are intended to prevent the water from leaking into the ceiling. Once it's in there it will have to go somewhere. If you'd block the ceiling it would just run into your walls into your closets and under your flooring and damage those, too. It's not that we wouldn't want to help you, it's just that sealing your ceiling from the bottom isn't an idea that would work. Don't know where you are, so I can't tell you what's available in your area. You may qualify for free legal assistance from some organization. Check your condo contract and your insurance policy and follow the advice the others have given. OR We have an occasional leak in our basement and are now into our third expert trying to find and remedy the cause. This kind of thing isn't a job for DIY even if you had better skills and knowledge than you seem to have. 76.97.245.5 (talk) 14:07, 15 February 2009 (UTC)

You don't say where you are from - and you don't say whether you and your neighbour own the apartments or are renting them - so it's hard to guess what legal options might be open to you. For sure there is no technical/engineering solution. That water is landing on your ceiling and that's that. If your ceiling is showing damage - and presuming you have insurance on your apartment - then I would make a claim on your insurance for the damage. They will come and investigate - they'll realise that your neighbour is at fault and will make a claim on him. Then there will be action. If you are renting the apartment - then you need to talk to your landlord. Whatever you do - you need to do it soon because your ceiling will collapse...and you'll also be getting mold growing up there which could have serious effects on your health. You should also talk again to your neighbour - explain clearly that if he doesn't fix the leak - and quickly - he will be responsible for all of the damage AND the leak will have to be fixed. If he fixes the leak now - then he's saving himself money. You might also check whether there is a home-owners' association for your apartment block - they would be able to help you too. SteveBaker (talk) 15:16, 15 February 2009 (UTC)

One comment: Just because there is water leaking from your ceiling doesn't necessarily mean it's coming from the apartment directly above yours. Water can leak from another apartment or even a roof ice dam, travel down the walls until it reaches a barrier, then travel between the upstairs floor and your ceiling until it finds a spot to leak through. StuRat (talk) 17:20, 15 February 2009 (UTC)

THere's some excellent advice above. In your situation I would I would contact your building insurer immediately in the form of a letter, marked Urgent, that states that you observed a water leak start, you believe it originates from Floor #1 and that you have informed (by a copy of the letter) the resident of the danger of damage. The logic here is that if damage and argument do arise, you have proof that you took steps to limit damage, and there is no accusation that provokes the other resident. Good luck. Cuddlyable3 (talk) 17:37, 15 February 2009 (UTC)

Is there any Green Agency at India

There are agencies that help corporates move towards achieving energy efficiency like 1 degree in Australia that helps News Corp. to reduce green house gas emition.

Is their any such service at India? or other parts world wide? —Preceding unsigned comment added by 117.196.164.211 (talk) 16:24, 15 February 2009 (UTC)

This might be a start [12].76.97.245.5 (talk) 23:59, 15 February 2009 (UTC)

Past weather data

Please, is there an internet source for detailed past weather data? I'm looking for specifics (e.g., weather in Wales on a specific date), not long-term weather records. I realize that what I am looking for would require a large database.

Thank you, Wanderer57 (talk) 16:39, 15 February 2009 (UTC)

Try searching newspaper sites. If they've got their archives online, just pick the date you're interested in. B00P (talk) 17:26, 15 February 2009 (UTC)

TuTiempo. I found it a couple of months ago looking for historical weather data for Cape Town. The site is amazing, it has daily weather data for seemingly every city in the world going back decades, and not just temperatures, it has precipitation and cloud cover and everything. Knock yourself out! Zunaid 17:51, 15 February 2009 (UTC)

p.s. you have to click on the "climate" section in the left-hand column. The link for the UK is this. Zunaid 18:45, 15 February 2009 (UTC)

In the U.S. Weather Underground is very similar. I don't know what its like for locations outside the U.S. however. --Jayron32.talk.contribs 18:35, 15 February 2009 (UTC)

For locations (airports) in Canada, The Weather Network has historical weather data for most dates in the current millenium. ~AH1^(TCU) 16:41, 16 February 2009 (UTC)

The National Weather Service provides recent and current archives, and also has an FTP server with long-term archives, for all US locations and many many world-wide locations. They are a little "more official" than WeatherUnderground, but their database requires a bit more technical savvy to access. Nimur (talk) 16:45, 16 February 2009 (UTC)

For specialist only...!

I'am working at construction feild , as asite engineer

now we're filling the spaces between the foundation according to cast the (slab on grade ) , to save time we are using single size aggregate instead of selected natural material , now and according to the plans there is a 15 cm layer of basecoarse under the slab , the question is this ...?

if i execute this layer , and we assume some how water did find its way to this layer , dont you think that the water will carry the fine material contained in basecoarse and move it down ward through the voids between single size agg. particles ,leading to deflection in the slab.

and , is the only purpous of (15 cm layer ) of single size to protect the slab concrete from being in contact with the natural fill material , and why ...?

i know its hard to understand all of this but i hope to get an answer ... ? —Preceding unsigned comment added by 94.249.40.92 (talk) 17:34, 15 February 2009 (UTC)

This is, essentially, a legal question. At least, it is a question which requires knowledge of building regulations in Jordania, knowledge of the plan of the building, the specifics and substrate of the buidling site, the reinforcement of the slab, the aggregate you are using for the fill, data on precipitation / groundwater and a few details more. I can´t imagine that you will get useful answers from a distance, even from static engineers. --Cookatoo.ergo.ZooM (talk) 18:34, 15 February 2009 (UTC)

we are using BS standards , we dont have our own i thought its going to be the same detailes for concrete structures assume , ordinary building use , low water table , warm claimate , crushed stone fill ( course aggregate used in concrete casting ). you will find a very excellent answers at www.contractortalk.com . thanks —Preceding unsigned comment added by 94.249.40.92 (talk) 18:51, 15 February 2009 (UTC)

Do British standards contain a section on earthquake engineering or earthquake construction? I hope we aren't going to get any more of those reports like 1999 İzmit earthquake on bad construction. Cheaper isn't always better. 76.97.245.5 (talk) 07:59, 16 February 2009 (UTC)

is it a coincedence too

I want you to follow this link , after you watch the video , please i need your objective opinion ...http:/www.metacafe.com/watch/98111/miracles_of_the_quran_12/

be objective .... thanks . —Preceding unsigned comment added by 94.249.40.92 (talk) 18:41, 15 February 2009 (UTC)

Many of us do not go to off-WP sites that could be anything. You can help us help you by asking your question, please, and by telling us what the link purports to show. We prefer to deal with facts, not opinions, objective or otherwise. Thanks ៛ BL ៛ (talk) 18:47, 15 February 2009 (UTC)

That's not a coincidence, it's just nothing at all. So the Qur'an mentions the tips of the fingers, who cares? I'm sure people noticed that fingers had tips long before the Qur'an was written. It's just a reference to putting together the whole body, it makes no reference to using fingerprints for identification, or even a mention of fingerprints at all. --Tango (talk) 18:53, 15 February 2009 (UTC)

will ... this link will show avideo talking about finger print and that quraan referred to it and that each person do have a unique finger print from evry one else ... will how do they knew that ... ? —Preceding unsigned comment added by 94.249.40.92 (talk) 18:56, 15 February 2009 (UTC)

The quote from the Qur'an doesn't mention uniqueness at all. It doesn't even mention fingerprints, just the tips of the fingers. --Tango (talk) 19:03, 15 February 2009 (UTC)

And even if it did, the observation that fingerprints are unique is something that anyone who looked at them would be able to figure out. It doesn't require any scientific theory to understand this, so I see no reason why this couldn't be known, even to prehistoric people.. StuRat (talk) 19:46, 15 February 2009 (UTC)

Well, it's of note that it took quite a bit of time before this was really proven to be true. They look superficially similar to one another—you have to really look at them closely to see that they are in many ways very different from one another, and you have to extrapolate a bit further beyond that to think that such is a meaningful observation (why does it matter that fingerprints are unique, vs., say, noses, which are also unique). The modern significance of fingerprints for forensic criminology was not surprisingly only figured out in the 19th century or so—it requires a concept of forensic criminology first. --98.217.14.211 (talk) 20:29, 15 February 2009 (UTC)

Yeah - this is nuts. The whole thing is based upon one line - whose English translation is: "Yes, We are able to put together in perfect order the very tips of his fingers.". This doesn't say - or even imply that "everyone's fingerprints are unique" - it says that fingertips are "in perfect order" - which I would more likely assume to mean that all fingertips are perfectly smooth - or they all have nice regular 'ordered' stripes or concentric circles or something. Fingertip patterns are a result of 'chaos theory' - which is about as mathematically 'unperfect' as you can get. So FAR from assuming that this book says that we all have unique fingerprints, I'd go so far as to say that the existance of totally different fingerprints is yet another thing proving the Quran is wrong (and lest I appear to have a western bias here - let me also point out that the christian Bible and the Tanakh and the Sefer Torah are also filled with just as much nonsense and untruths). Besides - there are many other aspects of humans that are just as unique as fingerprints. Our toeprints are also different. Our retinal patterns are different...pick the ratios of the sizes of any few dozen physical features, round them off to the nearest 1% and you'll have a number that's unique to every human on earth. There are any number of other things that are unique. Why does the Quran not mention that chimpanzees also have unique fingerprints too? Dogs have unique nose-prints. The only reason people find human fingerprints in any way 'notable' is because we leave behind little greasy patterns when we touch things with our hands - and that provides a means to tie a criminal to some place or object. I guess the Quran failed to mention that too. Furthermore - fingerprints were used as identification by the Babylonians around 4,000 years ago. Since the Quran is supposedly only about ~1400 years old - this hardly constitutes a prediction! I'm sorry - but when religious nuts of all kinds come to the science desk in an effort to impress us - they are going to get torn to shreds by actual FACTS. This is no different. SteveBaker (talk) 19:58, 15 February 2009 (UTC)

See Fingerprint#History_and_validity for some very old uses of fingerprints. — DanielLC 20:55, 15 February 2009 (UTC)

See, this is what irks me about people's misunderstanding of science. You can blindfold a man and ask him to throw darts at a dartboard. Every once in a while, he will hit a bullseye. Merely because he does so does not make him a good dart player. Darts is a game which requires a certain set of skills and talents and needs practice to play right, and merely because dumb luck resulted in a blindfolded man hitting a bullseye does not mean that being blindfolded and throwing random darts is a valid way to win the game. Likewise, science is a process and not a collection of facts. Just because someone randomly makes a statement, without going through the scientific process, which happens to match what rigorous scientific study has shown to be true; does not mean they got it right, and more than we can say that playing blindfolded is the "right" way to play darts. --Jayron32.talk.contribs 21:01, 15 February 2009 (UTC)

I kind of doubt that you're interested in our "objective opinion". Essentially, you keep on coming at us with various "amazing" things from the Qur'an -- the development of the fetus, fingerprints, all of that -- and we keep explaining to you why it doesn't mean that the Qur'an is the best science book you could possibly have. It's not hard to identify you, even though your IP address changes, because... you have a very distinctive... style of writing. You keep presenting these things from the Qur'an to us, as if they were proof of something, when, in fact, all you do is either demonstrate your own ignorance (at worst) or misconceptions (at best) of science and history, or misrepresent what the Qar'an actually says.

The ridiculous thing is, you keep doing it, and let me predict something here: if you manage to get one right and come up with an example of the Qur'an coming up with some great scientific discovery, then you'll probably hold that up as some kind of proof. That's a case of counting the hits and ignoring the misses, and frankly, I find it a little sad that you're trying to use the Ref Desk as a tool in this campaign of validation. -- Captain Disdain (talk) 21:46, 15 February 2009 (UTC)

That is harsh and I would grant some WP:AGF to the questioner who I think honestly needed objective input. Cuddlyable3 (talk) 22:11, 15 February 2009 (UTC)

If you read the original poster's comments -- including the one below directly below -- and believe that he has no agenda, okay, that's fine with me. I disagree, and I think his own comments back me up. But please understand that I'm not really assuming bad faith as such, either. I'm not saying he's dishonest here, because that implies some kind of a malevolence... but I don't think he really wants objective opinions or knowledge. I think he wants to present us with something that proves his faith, and that doesn't really go well together with being objective. I can understand why he does that, but the end result is that we jump through hoops. And I wouldn't mind that as such, but when he ignores what he's told and keeps hoping for that hit, it's not a very fair setup -- if he was trying to understand or looking for knowledge, that'd be one thing, but he isn't. He's looking for validation.

I think WP:AGF is a kind of a problematic guideline a lot of the time. It's great when you run across something that makes you angry or looks weird or suspicious for the first time, but it often gets twisted into a free pass. -- Captain Disdain (talk) 08:05, 16 February 2009 (UTC)

iam not trying to press my opinions , its afact its your choise not to belive . when i talked about univers expanding ,some said it was acoincedence , and talking about finger prints some talked about darts game , and steve say it was used 4000 years ago (prove it , put some links at least ). the statment was that god will recreat us that he will even rebuild our finger tips , because they didnt have the term finger print back then , if he say finger print they are'nt going to understand , because simply they didnt have that word . i do have more , alot more and if you can make me belive this all just luck or wrong i will become atheist . and if you say it was used 4000 years ago (please prove it ). about the different addresses , will i use alot of computers ,its not even mine . have faith people ,even if thier's a probabilty about 1/1000000 that your wrong it does worth it,dosent it i dont understand why you are so angry , you should be more tolerance . excuse my english , iam not an english native ,thank you any way ... —Preceding unsigned comment added by 94.249.40.92 (talk) 22:30, 15 February 2009 (UTC)

You seem to be referencing Pascal's wager, a seriously flawed argument. The expanding universe thing was an intentional mistranslation and the fingerprint thing is just reading more into a quote than is actually there. These aren't coincidences, they're just very poor attempts at making it look like the Qur'an is saying things it isn't. --Tango (talk) 22:36, 15 February 2009 (UTC)

You requested a link in respect of the use of fingerprints in antiquity. See Fingerprint#History_of_fingerprinting_for_identification for statements, with sources, about the use of fingerprints as identification on legal documents as early as 1900 BCE, which is just shy of 4000 years ago. ៛ BL ៛ (talk) 22:44, 15 February 2009 (UTC)

we are using a very advanced technology to identify finger prints , and some time we have errors and your telling me that 4000 years ago they were using it to the same purpose . will .. is this make any sense , mabey they notice the shape,mabey they assume that its unique , but use it to identify people in thieft cases ... iam sorry this is too mush ...??????????? —Preceding unsigned comment added by 94.249.40.92 (talk) 23:03, 15 February 2009 (UTC)

We use ink and some kind of powder - not very advanced, really. You don't need computer analysis for fingerprints to be useful, it just makes it quicker and more accurate. --Tango (talk) 23:10, 15 February 2009 (UTC)

I noted that fingerprints were being used for identification instead of signatures. I said nothing about criminal use. Muslim tradition dates the Koran from around 610-630 CE. From the article "Fingerprint" linked above comes: In China around 300 C.E. handprints were used as evidence in a trial for theft. From the remainder of that paragraph, it appears that at least one other culture knew about fingerprints at the time the Koran was compiled, and this knowledge was a part of the Chinese criminal-justice system some 300 years prior to the dates of the Koran. It is fact. ៛ BL ៛ (talk) 23:23, 15 February 2009 (UTC)

I apologize for leaving off the link - but (as others have pointed out) it's right there in our Fingerprint article. Fingerprint#History_and_validity to be precise. It says (with LOTS of impeccable references) that the Babylonians were fully aware of the uniqueness of fingerprints around 4,000 years ago. The didn't use ink - they used soft clay which was then baked into pottery to make it permenant. They used them in place of signatures. So without any doubt whatever - the Quran didn't predict or explain anything that wasn't already well-known. If you were honestly curious - you could have looked at that article and discovered precisely what I discovered. But even if we somehow deny all of these older instances of an understanding that fingerprints are unique - you can't claim that this one sentence in the Quran says ANYTHING about fingerprints being unique. Just read the darn thing! It says that they are in "perfect order" - I can't make my brain go from "perfect order" to "completely and utterly random and different on every single person in the world"! How can those two things POSSIBLY mean the same thing?! So the Quran didn't predict or explain ANYTHING - in fact (if we are to believe that it's talking about fingerprints at all) it stated completely the opposite of the truth! I don't know whether you plan to drop these supposed "facts" from the Quran on us every few days in the hope that one of them will be convincing - but honestly, it's pointless - I can tell you - in advance - that not one of them will turn out to be true...not one. So if you really must - why not get it over and done with in one go. Just list the whole phreaking list in one question and I promise that I'll personally go through the list disproving every single one of them - with references. If you're honest - then you'll have to admit that this stupid book is as big a pile of crap as all of the other "great" religious books of the world and then we can go back to answering questions from people who aren't trying to push an agenda. Sadly, I know you won't do that because you're brainwashed. You don't give a damn about the answers - you just have some vague hope that we'll be dazzled by the impressiveness of a 1400 year old book...but we're not going to be. If the Quran contained all of these deep scientific and technological truths - how come none of the consequences of that was ever discovered by the people who live and die by that book? Most of math, science and technology comes from the christian world...and mostly from atheists living within the christian world. Religious teachings ALWAYS act to suppress advances in science and technology...the Quran is no different. SteveBaker (talk) 02:58, 16 February 2009 (UTC)

dear Mr steve .. you hav'nt disprove any of them . about finger print ... the statment says that god will recreat evry one of us that he will even rebuild his finger tips ... god want to show you that he is cabaple of reproducing your body after its turned into ashes that he will even build your finger tips back .... translation may not give the same meaning , because languages are different , that i can't help you with . and why the people who lived by the book had'nt dicover any thing , because they are no ascientiests , they are an ordinary people , what its gonna mean if they discover it 1400 years ago . arab world became the most advanced in the world , because they lived by the book , bibble and tawrah is the book of god as mush as the quraan , but we missed the two up , that god send the last one (quraan) to be the last , surly god didnt leave people before islam lost in the world . and finally , i will list up what i know , and wait for your answers , and before you answer read the explanation of it , and dont expect to find some mathmatical expression in it , such science could'nt be expressed by arabic language that time , the word was'nt enough . i look at indian scientist worshiping caws , mabey i'am justlike them and maybe not , at least i considering the possibility , why dont you , you could be wrong either Mr steve . —Preceding unsigned comment added by 79.173.227.192 (talk) 07:34, 16 February 2009 (UTC)

So you've changed what you were saying. You asked us to comment on a video that said that the Quran predicted that fingerprints are unique. I clearly showed that not only does it not say that - but also it didn't say whatever it actually DOES say until a couple of thousand years after the fact was already well known. Now you are just saying that the Quran tells us that god will rebuild us or something - that's a completely different matter - it doesn't say anything about predicting that we all have unique fingerprints - which is what you asked us to discuss. So did we answer your question by proving that the Quran DOES NOT predict unique fingerprints? If so - then we're done here. SteveBaker (talk) 15:45, 16 February 2009 (UTC)

You're not listening and I'm not going to repeat it all. You clearly aren't here to learn, you just want science to prove Islam right, and that's not going to happen. Please stop posting here. --Tango (talk) 12:04, 16 February 2009 (UTC)

And what does this book say about aggregates (previous question above)? Bazza (talk) 14:54, 16 February 2009 (UTC)

What's the point of debating this? Either the Quran did have scientific facts in it, or it did not. Lots of books have lots of important information buried in lots of noise, and suffer from widely interpretable translation artifacts. But you don't see scientists running around quoting Principia Mathematica verbatim (Quantitates materiae in corporibus funependulis, quorum centra ossillationum a centro suspensionis a qualiter distant, sunt in ratione composita ex ratione ponderum & ratione duplicata temporum oscillationum in vacuo!) We have better ways to say the same thing, rendering the original text obsolete, and as a scientific community we can move forward. If the material is relevant, the truth of it will be self-evident. The mindless task of deciding attribution, or assuming that the author was divine, divinely inspired, etc., is a question for the humanities desk, because that sort of thing is not a science question. Nimur (talk) 16:59, 16 February 2009 (UTC)

On ancient languages being incapable of saying "fingerprints are unique"

You made an assertion at one point that they had no way to say "fingerprints are unique", so said the closest thing they could in the language at the time. I disagree. If they didn't have a word for fingerprints, they could have said something like "the patterns on the skin on tips of the fingers, on the underside, opposite the nail, are different for each person and each finger". This would work without the words "fingerprint" or "unique". Most concepts can be described without words needed for the concept itself, by using more words. This is what a dictionary or encyclopedia does, after all (or at least what they're supposed to do). StuRat (talk) 16:44, 16 February 2009 (UTC)

our discussion is if the quraan is god word or not , so we will assume that it was made by god , which lead to the fact that these is gods word not ours . i can give you alot of similar examples , but assuming that god want to talk about the earth , god mentioned that he had created seven earthes , its not clear unless you search for it to find that earth is made of seven layers , not three as we use to know , it was meant to remain unexplained until we explain it , so to be like aguide , aprove that this book is the word of god . will the question is is it acoincidence that seven earths were used , or mabey the fact is just wrong, or what and finaly , even if any one could proof that there is ascientific facts in quraan , its very easy to say , avery advanced civilisation had lived before us and this is just their remains . its easy to ignore it , to assume any thing . my friend , i'am not arelegious man , yes i'am amuslim but i'am not really amuslim if you know what i mean , just like chrestians these days , i'am just trying to find the truth , no thing i said were disapproved , they all make assumptions , like coincidences and such , from where did we come , evolution , mabey ,its just theories . all i'am asking is try to be neutral , admmit the possibility that this could be true . and please dont get angry , i'am not your enemy , thank you any way . —Preceding unsigned comment added by 86.108.53.185 (talk) 18:20, 16 February 2009 (UTC)

I don't see why "words having come from God" would mean that they must be so vague they could be interpreted to mean just about anything. Why exactly would God want to give us confusing descriptions instead of clear ones ? As for your example of "7 Earths", it's quite a wild assumption to take that to mean "one Earth with 7 layers". And, even if you did (mis)interpret it that way, you could say the Earth is made of just about as many layers as you want. Just the atmosphere could be said to have 7 layers, if you wanted to define it that way. So, if you combine being able to interpret holy words in any way convenient and being able to interpret science in any way possible to get a match, you will find you can "prove" just about any holy words you want. StuRat (talk) 19:19, 16 February 2009 (UTC)

Islam teaches that only the original Arabic is God's word - you're talking about translations of God's word, and often serious mistranslations. --Tango (talk) 22:50, 17 February 2009 (UTC)

Do you seriously imagine that the Arabic version is any clearer on these points? SteveBaker (talk) 14:32, 18 February 2009 (UTC)

No, I don't think many of the points exist at all in the Arabic version (they barely exist in the English ones). --Tango (talk) 17:20, 18 February 2009 (UTC)

On the predictive nature of good theories

While it's one thing for a theory to be able to be adjusted to fit data that doesn't fit initially, it's certainly not a proof that the theory is correct. What would be a partial proof is if the theory allows us to predict things accurately. For example, was there anything in the Koran which clearly pointed to the date of the tsunami ? (I mean so clearly that everybody reading it would have been sure that it could only mean that date, before the event occurred.) No, of course not. If so, then all believers would have evacuated the coastal areas on that day, but they didn't. StuRat (talk) 19:29, 16 February 2009 (UTC)

Question about the nature of the expanding universe

Hi, my question is ver stupid but here it goes. What is beyond the expantion? 1) Nothing?? in this case we can say that "the expantion of the universe" is creating "space" as it keeps going. 2) Empty space? in this case we can say that our big bang could be just one of "many big bangs" going on at other points of that "empty space" I think this question is a little confuse.. sorry about that and thanks for the future answers. --Starlingmaximilian (talk) 20:28, 15 February 2009 (UTC)

There are two acceptable answers. One is "nobody knows and we don't have any good way of knowing." Not very interesting but technically true. The other is "nothing is necessarily beyond it, as far as we understand it"—that is, the expansion of the universe is creating "space" as you put it, it isn't expanding into anything. Whether people lean towards one or the other interpretation seems rather arbitrary to me, but in any case the answer given isn't ever going to be "empty space", at least, other than that being a possible answer in the "nobody knows" sense (which would make it as valid an answer as, say, "butterflies"). --98.217.14.211 (talk) 20:36, 15 February 2009 (UTC)

Neither. It's not really clear whether the universe is infinite or whether it 'wraps around' in some manner...but in either case, there is no "edge" of the universe - and therefore no "beyond". We've tried to explain that here MANY times - but the thing people don't "get" is that it's not that objects in the universe are moving apart so much as it is that space itself is stretching. This gives the impression that things are moving apart - but essentially, they are staying still while space itself stretches. SteveBaker (talk) 20:41, 15 February 2009 (UTC)

SteveBaker has it right. Try it from this perspective. The simplistic view is that the Big Bang was a singular event. People often view it as a massive explosion which "pushed" objects outward, and that the expansion we see is merely the inertia of these objects which they carry from this initial push. Its a nice, easy to understand image, and like most of "real" physics, it doesn't match what is really going on. The more complete view is that the Big Bang is the process of space creation. Under this understanding, space is created between the galaxies; they don't actually move of their own accord. The Big Bang is not a singular event, its an ongoing process. The problem with the "explosion" explanation is that, if it were true, we could observe the motion of the galaxies, and identify a "center" of the Universe from which the matter was moving away from. Except, when we look at the whole observable Universe, the grand picture is not of galaxies moving away from a central point of explosion, its of all galaxies moving away from each other uniformly. That only makes sense if there is no center of expansion; and the "creation of space" model fits the observations much better than the "big explosion" model. --Jayron32.talk.contribs 20:53, 15 February 2009 (UTC)

Could we not be in a volume of space that is shrinking in a pervasive way such that none of our local measurements seem to be affected, embedded in a static infinite Universe ? Cuddlyable3 (talk) 21:54, 15 February 2009 (UTC)

How are you defining "shrinking"? If our measurements of its size are staying the same then, by any reasonable definition I can think of, its size is staying the same. --Tango (talk) 21:56, 15 February 2009 (UTC)

By shrinking I mean you, me and all our tape measures getting smaller. An astronomer on a distant galaxy who is also shrinking could be looking towards us right now, measuring our sun's red shift and calculating how much closer we are than them to the time of their equivalent B. Bang concept.Cuddlyable3 (talk) 19:12, 16 February 2009 (UTC)

Universe can't be infinite, it must be an "edge", call it "end of the space" or "Matter moving from initial inertia". If space is tretching is because it has a limit!! and if is being created it has a limit as well!!! I found 98.217.14.211's answer very satisfactory, cause i don't know about phisics but is philosophically impossible that the universe doesn't have a "dinamic edge" —Preceding unsigned comment added by Starlingmaximilian (talk • contribs) 22:04, 15 February 2009 (UTC)

It's difficult to get your head around, I know, but the universe doesn't have an edge. Either it's infinite (trying to understand how the big bang works in an infinite universe is a sure fire way of giving yourself a headache!) or it has a closed shape - think of the surface of a balloon, as you blow it up the surface expands, but it doesn't have an edge. --Tango (talk) 22:10, 15 February 2009 (UTC)

In the baloon example the "edge" would be the last layer of rubber of the ball, and the "beyond" the air surrounding it... sorry... i'm very troublesome :)

No, we're just considering the surface of the balloon - the idealised 2-dimensional object. --Tango (talk) 22:32, 15 February 2009 (UTC)

Ok, In the baloon example the "edge" would be the unique layer of the ball (sphere), and the "beyond" is whatever outside the ball, it may be "the nothing" "the lack of space" call it as you like. —Preceding unsigned comment added by Starlingmaximilian (talk • contribs) 22:47, 15 February 2009 (UTC)

Inside and outside are references to the 3rd dimension, we're just talking about the 2D surface. Imagine you are a tiny ant walking around on the surface, there is no edge that you can fall off. --Tango (talk) 22:54, 15 February 2009 (UTC)

the body of the aunt is in "the nothing" in your example (obviosly impossible) and only the feet of the aunt are in contact with the sphere, but yet, outside. —Preceding unsigned comment added by Starlingmaximilian (talk • contribs) 23:16, 15 February 2009 (UTC)

Indeed, as with any analogy it breaks down if you look too closely. The ant is meant to be infinitely thin - it's just an analogy to help make it easier to understand. Obviously, the universe is 3D, not 2D, but the principle is the same. --Tango (talk) 23:37, 15 February 2009 (UTC)

I told you that this was going to be the problem! We've explained this at least a dozen times - and every time our OP gets stuck at the same point. We explain the balloon analogy and it doesn't help. How about the chocolate chip cookie analogy? If you buy raw cookie dough - a blob about an inch across can be placed on a baking sheet and after you bake it, you have a cookie that's about four inches across. With chocolate chip cookie dough, you start of with something that seems to be almost all chips - but after you bake it, they are quite far apart. So - the chocolate chips are...galaxies say...the dough is space. As the dough cooks every chip gets further from every other chip. No matter which chip is "you" - it seems like all the other chips are moving away from you - and the further they are at the outset - the faster they'll seem to recede. Now - if your original piece of cookie dough was infinitely big - and you baked it in an infinitely large oven - the result would still be infinite and every chip would see every other chip receding from it. SteveBaker (talk) 02:29, 16 February 2009 (UTC)

The problem is that REALLY BIG PHYSICS and really small physics work very non-intuitively. That is, the laws which govern the way the REALLY BIG THINGS (like Galaxies) and the really small things like atoms, do not obey the same basic laws which govern the medium sized world we live in. Basic Newtonian physics, where infinity has no meaning, where I push something and it behaves as I expect it, where waves are waves and objects are objects, describes the medium-sized world very well. However, when we actually make observations and measurements of the REALLY BIG STUFF (like galaxies) and of really small stuff (like atoms) the laws that seem to work well for the medium-sized world just don't apply. So entire new sets of laws and theories needed to be created to account for these differences in observations.

Now here's the kicker, these new laws and theories work perfectly well, they are mathematically and observationally consistant, they just don't make any sense. By that I mean that our unaided senses give us certain information about the world. That information leads to an intuitive model of how the world is supposed to work. It's almost subconsious; a 6-year old probably has the same intuitive model that a 30-year old does. The problem is that this model we have created for ourselves does not match the way that the REALLY BIG STUFF and the really small stuff works. So, you get the sort of incredulity that the OP expresses. At some point, if you are going to understand how the universe works on a cosmological level and on a subatomic level, you are just going to have to ditch everything you intuitively understand and accept what the actual data and observations are really telling us about how it really works. --Jayron32.talk.contribs 04:04, 16 February 2009 (UTC)

Well, it may be true that my intuition is playing me tricks... and i cannot accept examples like the balloon or the cookie... they always have a catch... but even if my intuition is making me unable to understand i can't let it apart.. i cannot accept something that don't makes sense, even if observations and maths tells me the oposite. Lets just keep it like this guys :), but one last thing, if any of you knows about any documental video explaining this subject please post it here and i will watch it. Also i want to thank 98.217.14.211 SteveBarker, Jayron32 and Tango for all the time you took in order to explain this subject to me, thanks to people like you wikipedia is as big as it is, thanks a lot guys. --Starlingmaximilian (talk) 10:05, 16 February 2009 (UTC)

Yes - there is a very real sense in which our minds are not evolved to deal with Quantum physics and the various large scale weirdnesses. However, if all else fails, you can punt on the idea of having a mental picture of what's going on - and instead just rely on the observations and the math. Sadly, you have to accept the reality of it because it is true. Nothing else can explain the observation that every object in the universe is moving away from us - and the further they are from us, the faster they are moving away. You can prove that with a spectrometer and a backyard telescope - so there is really no doubt that it's true. But getting your head around the concept that something can be both infinite and expanding is tricky. Then when you're told that it's space itself that's doing the expanding and all of the objects within it are more or less stationary...that is REALLY tough to envisage. So you have to believe it's real - even though you can't envisage a nice analogy. Trust the math. SteveBaker (talk) 15:22, 16 February 2009 (UTC)

Most scientists consider the universe to be "flat" - that is, if you were to look at the edge of the universe, it would be exactly flat. So it's an open universe, not round or closed, and it has infinite size. However, the "edge" would still be expanding "outward", that is, away from itself and its contents. ~AH1^(TCU) 16:36, 16 February 2009 (UTC)

There are empirical limits on how curved the universe can be, but I'm not sure it's true to say most scientists think it is completely flat. Even if they do, it doesn't follow that it's open - a 3-torus is closed and flat (when we think of it as embedding in higher dimensional space it has an extrinsic curvature, but it doesn't have intrinsic curvature which is all that matters in this context). --Tango (talk) 19:02, 16 February 2009 (UTC)

Okay, first, there was no big bang. Big Bang cosmology isn't about a big-bang event and doesn't say that there was one. It's misnamed. Second, we don't know whether there's an edge. The cosmological model we use doesn't have an edge in it, but there's no reason to think that it models the whole of existence. We already know it doesn't work farther back in time than ~14 billion years, and it doesn't necessarily apply further than some finite distance in space either. It's a mistake to assert that the universe has no edge just because the model doesn't have one. We couldn't directly see or otherwise detect any edge because of the light speed limit anyway. Third, as I keep saying, the cosmological expansion is just galaxies moving apart. It is not galaxies standing still while space is created between them. There's no way to invent a coherent concept of "creating space" because space doesn't have the properties of a substance. There's no conservation law for space. All of the space at any given time is brand new: it's all-new points in spacetime. The principle of relativity implies that you can't associate any particular point in space right now with any particular point in space at an earlier time (in contrast to ordinary matter, where you can trace back the worldlines and tell which matter is new and which has been around for a while). The other reason you can't talk about creating space is that the physics governing the separation of the galaxies is exactly the same physics governing the separation of any other two objects. These situations aren't distinguished in any way in the mathematics, and there's no natural dividing line you can draw between them. When an astronaut on a spacewalk drifts away from the shuttle, space is being created between him and the shuttle in exactly the same sense that space is being created between the galaxies in the cosmological expansion. It's all relative motion. If we knew the volume of the whole universe, and it was finite, it would be increasing with cosmological time, and you could describe that as an "overall expansion of space", but I would still strongly discourage that because everything I said above still applies. Physics is local; the universe doesn't care about quantities obtained by integrating over large quantities of space at a fixed cosmological time. Each bit of spacetime is doing its own thing, whether or not an overall volume can be defined. -- BenRG (talk) 18:24, 16 February 2009 (UTC)

I still don't get that. How does that work for, say, a 3-sphere? What are the momentum vectors for each galaxy at a given moment of time (in a given reference frame, it doesn't really matter which)? I can't see any way they can all be pointing away from each other. Somewhere you would need to have a region of space that is contracting, which doesn't fit with any theory of cosmology I've heard (except for contractions on very small scales, which don't help here). --Tango (talk) 19:02, 16 February 2009 (UTC)

Okay, here's the best answer I can come up with for this. The key points are: 1. The relative motion of galaxies and the relative motion of astronauts are essentially the same. This doesn't mean they're both special relativistic—they're not, they're both general relativistic. It's like saying that separation at 1 m/s and separation at 299,000,000 m/s are essentially the same, even though Newtonian physics gets one of them right and not the other. Think of the small-scale stuff in general-relativistic terms, not the large-scale stuff in special-relativistic terms. 2. Physics is local—the spacetime over here doesn't care about what the spacetime over there is doing, at least not directly. Suppose first of all that space has an edge. An edge of space, unlike the bulk, would have to have a state of motion. Suppose it's moving in roughly the same way as the galaxies in that region. Then, since the galaxies are moving away from neighboring galaxies, which are moving away from..., etc., all the way across the universe, the distance between the edges is also increasing, so the overall volume of space is increasing. However, the universe doesn't "know" this—all evidence suggests that different parts of the universe evolve independently. Locally, objects are just moving apart in the same way they would otherwise. In the case that space doesn't have an edge but closes around on itself, it's the same story. Locally, you have a net positive curvature that's due to the density of matter being a bit higher than the critical density. As matter continues to separate and thin out that density decreases and so does the curvature, though it remains positive. Global consistency requires that the total volume of space increased, but locally it doesn't matter. Locally there might as well be an edge moving "inward" at such a speed that the total volume remains constant (and eating up galaxies in the process, I suppose). In that case you might interpret it as galaxies flying outward through fixed space until they reach the edge instead of as fixed galaxies on an inflating balloon, but the universe doesn't care one way or the other.

The other thing is that it's somewhat arbitrary how you define the volume of space in the first place. Everyone knows that space is flat when the matter density equals the critical density and hyperbolic when it's lower than that. In particular, space is hyperbolic when the density is zero. But given that curvature is supposed to be due to the presence of matter, shouldn't it be flat in that case? In fact what's going on is that the Ω=0 limit of the FLRW cosmology is just a part of (flat) Minkowski spacetime, but the coordinates are such that the ones interpreted as "spatial" happen to cover a hyperbolic surface in Minkowski space for any given value of the "time" coordinate. If you look at the same cosmology in Minkowski coordinates, taking Minkowski x,y,z to be "space" and t to be "time", it looks like a finite flat space with a spherical boundary that's growing with time (at the speed c), instead of an infinite hyperbolic space with no boundary. Same physics, different coordinates. The Euclidean analogy for this is Cartesian versus polar coordinates. If you take Cartesian x,y to be "space" and z to be "time" then space is flat and infinite, but if you take θ and φ to be "space" and r to be "time" then space is spherical and finite and growing with time. A similar thing happens with de Sitter space, which is the exponentially inflating spacetime that was the past of our universe (according to inflationary cosmology) and also the future (according to ΛCDM). Cosmologists like to say that it's spatially flat (and infinite) and exponentially expanding (i.e. the scale factor goes like e^t), while mathematicians are more likely to say that it's spatially spherical (and finite) and the scale factor goes like cosh t. This is two different coordinate descriptions of the same thing. The universe doesn't care about global coordinate systems, and we probably shouldn't either. -- BenRG (talk) 23:19, 17 February 2009 (UTC)

Ok, i really like the point of view of BenRG, but if theres no space creation what do you understand with "origin of the universe"? i mean, if space is not "created" that means that the "origin of the universe" is just matter getting separated from his original point and that space was always there. But if you say that that would mean that many "origins of the universe" might be happening really far away of us, and maybe in an uncertain future colide with our "universe", but if we believe this, the word "universe" doesn't aplly anymore... do you really say that there was no "space cration" at the origin of the universe?? or maybe i got you wrong. --Starlingmaximilian (talk) 00:29, 17 February 2009 (UTC)

Our current theories only explain things back to a tiny fraction of a second "after the big bang", we don't know what happened before that (we talk about there being an "infinitesimal singularity" that went "bang", but "singularity" is just what physicists say when they don't actually know what's going on). --Tango (talk) 15:55, 17 February 2009 (UTC)

That was the traditional big bang, but in modern inflationary cosmology they do think they know what was going on and it's not a big bang singularity. The ΛCDM scale factor at very early times looks something like $a(t)\propto {\sqrt {t}}$, which obviously goes to 0 at t=0. That's the big bang. However, in inflationary cosmology there's a time t_R > 0 before which the scale factor is exponential instead due to non-ΛCDM physics, so overall you have something like

$a(t)\propto {\begin{cases}e^{{\frac {1}{2}}t/t_{R}}&t\leq t_{R}\\{\sqrt {et/t_{R}}}&t\geq t_{R}\end{cases}}$

where I put in factors of e and 1/2 to make a and a' match up at the crossover point. Real inflationary models are not this crude—there's a gradual transition between the models, not a grafting together of two different functions—but I think this gives the right general idea. The interesting thing here is that this new function never reaches zero, no matter how far to the left you go, so this model no longer has a natural beginning-of-the-universe. That doesn't mean there wasn't a beginning of the universe, but it does mean you should forget about the idea that there was a big bang at t=0. Nothing special happens at t=0; it's just a mathematically convenient origin point for the ΛCDM part of the model.

Incidentally, it's worth pointing out that the inflationary expansion is slower than the ΛCDM expansion in the regime where it actually takes place (i.e. before t_R). People are fond of saying that inflation causes the scale factor to increase by a factor of $10^{10^{10}}$ in 10⁻³⁰ second, but they neglect to mention that the ΛCDM expansion would have increased it by a factor of infinity (from 0 to a nonzero value) in an even shorter time. In fact, inflation is so slow that it takes literally forever to get from zero to a(t_R) (not that anyone thinks this simple model is valid arbitrarily far back in time). Inflation solves the horizon problem by being enough slower than ΛCDM that causal influences have time to cross the whole observable universe (which was very small back then, but not small enough to compensate for the quickness of the ΛCDM expansion). Also note that the duration of inflation is much longer than the "time after the big bang" at which it ends (in other words, inflation starts at t/t_R << 0). Or so it would seem, anyway. I don't think I've ever seen a description of inflation that mentioned either of these things explicitly, so I may be missing something, though I don't know what it is I could be missing. It would be nice to have some sources so I could either fix my thinking or fix Wikipedia's cosmology articles. -- BenRG (talk) 23:19, 17 February 2009 (UTC)

Coming from the inflation page, if space grew at a speed faster than the speed of light, then even though at a time before inflation light could travel across the whole universe, wouldnt info still not reach the edges of the universe (if there even is one) even traveling at the speed of light?--GundamMerc (talk) 15:44, 17 February 2009 (UTC)

It's not true that inflationary expansion is faster than light (a lot of books claim it is; they're all wrong). It is true that causal influences can't necessarily cross the whole inflating spacetime, but they only need to cross a part somewhat larger than our present-day observable universe to explain what we see. The uniformity that we see doesn't necessarily extend forever. -- BenRG (talk) 23:19, 17 February 2009 (UTC)

Do you edit on the redshift page, i think you would be useful there (groans inside at the different editors taking philosophical sides during discussion). Oh, and thanks for the help with that question.GundamMerc (talk) 12:29, 18 February 2009 (UTC)

Boiling to Death

I read our article on the concept, my question is though, what is the cause of death?

Does the skin slough off? Can the lungs not take in air if it's too hot? Does the blood boil in the veins?

Why would being immersed--not drowned, just immersed, in boiling hot water--kill someone?24.91.161.116 (talk) 21:34, 15 February 2009 (UTC)

Warning, the following link contains explicit images of a decomposed human corpse which may be distressing to some readers

If you really have to see. Please don't try this at home. Cuddlyable3 (talk) 21:44, 15 February 2009 (UTC)

That link is not safe for... um... anywhere from where you can see the computer screen... --Tango (talk) 21:50, 15 February 2009 (UTC)

I am apalled that the police could even consider releasing that picture on to the internet. The man must have relatives. SpinningSpark 00:53, 16 February 2009 (UTC)

I just feel bad for whoever cleaned up. Zain Ebrahim (talk) 15:00, 17 February 2009 (UTC)

An interesting question... Obviously your skin would burn, but I'm not sure that would be the cause of death (death from skin burns usually takes some time, as I understand it, I expect death by boiling to be reasonably quick). Boiling water entering the mouth or other orifices could cause internal burns, which could be more fatal (causing internal bleeding, damaging lung tissue and causing suffocation, etc.). Or, death could simply be by hyperthermia, getting too hot - if your core body temperature gets above about about 40 degrees, you're in real trouble, and I guess it wouldn't take long to get up to such temperatures when immersed in boiling water. --Tango (talk) 21:46, 15 February 2009 (UTC)

Quite simply, the cause of death would be the symptoms pertaining to hyperthermia. Your blood pressure would drop like a stone, dehydration, tachycardia (this could be the big killer here) etc. When your heart fails, you can no longer supply cells with oxygen and you will essentially die from that. Also, when you become unconscious, there's a risk of drowning. —Cyclonenim (talk · contribs · email) 23:18, 15 February 2009 (UTC)

One time, a girl fell into an area where the water was boiling in Yellowstone, after getting out of a hotspring. She was in the boiling water for seven seconds, and then she was dragged onto a cold river to cool for 45 minutes. She didn't survive. ~AH1^(TCU) 16:33, 16 February 2009 (UTC)

That probably wasn't the best treatment... In just 7 seconds I expect the only damage would be burns, hyperthermia wouldn't have set in yet. The first aid for burns covering more than about 1% of the body (and 100% is more than 1%!) is not to cool it since that will just cause hypothermia, but rather to go straight to hospital (after wrapping the effected area in cling film). Of course, this should not be taken as medical advice - if you want to learn first aid, take a first aid course! Even with correct treatment, though, her chances of survival would have been pretty slim. --Tango (talk) 18:42, 16 February 2009 (UTC)

Cream Smell

My girlfriend uses a skin cream which reminds me of doctors. Just smelling it immediately makes me think of hospitals.

I'm wondering which ingredient in this cream is the cause:

they are as follows: Aqua, Glyceryl, Stearate SE, Glycerin, Lanolin, Alcohol, Benzyl Alcohol, Cetearyl Alcohol, Oleic Acid, Triethanolamine, Stearic Acid, p-Chloro-m-Cresol, Parfum (Fragrance), Linalool, Limonene, Citronellol, Courmarin, Geraniol, Anise Alcohol, Benzyl Cinnamate

is one or several of these a main component of the bandages/first aid/ointment smells of hospitals?24.91.161.116 (talk) 21:39, 15 February 2009 (UTC)

The alcohol (ethanol) and benzyl alcohol are both common solvents and disinfectants that are found in many medical products; they both have a fairly distinctive odor that you may associate with hospitals. Triethanolamine also has an ammonia odor which again could be associated with all sorts of medical products. p-Chloro-m-Cresol, if I recall right, has a distinct odor of phenol, which is another common disinfectant which has a very distinctive smell - if I had to bet, I'd say that is likely to be the culprit. Phenol makes me think of hospitals too, it's a very horrible and very distinctive medicine-like smell. The last eight ingredients are all substances specifically added for their smell; and are all common components of perfumes and cosmetics - it's unlikely you'd associate any of those with hospitals, though again it's possible. ~ mazca ^t|c 23:29, 15 February 2009 (UTC)

^{yes, I've spent too much time sniffing chemicals at university. I'm surprised I'm not dead.} ~ mazca ^t|c 23:29, 15 February 2009 (UTC)

Mmmm I would say the alcohol would definitely be methanol and its unlikely you are smelling that over the Parfum (which means perfume) or the Lanolin. The methanol that normally goes into these products has almost no smell. I know you may be thinking 'Hey, I've smelled rubbing alcohol before and I know it has a smell,' but that isn't the methanol you are smelling; it is an additive to make sure you don't try and drink it. Benzyl alcohol is just a preservative and while it is found in IV solutions to keep them sterile, I don't think you could pick that out either. I have compounded many similar creams and would say that you could smell the lanolin. Most lanolin that goes into cheaper OTC products isn't necessarily medical grade and contains a lot of smelly fatty acids. Whether or not those smell like a hospital, I'm not sure. Mazca probably hit on the answer in one of his other suggestions, but I'll rule out methanol as a possibility. --Mrdeath5493 (talk) 01:30, 16 February 2009 (UTC)

Yeah, you're correct on the topic of those alcohols - regardless of whether it's ethanol or methanol, in retrospect I doubt either would smell strongly enough to overpower the perfume ingredients. Benzyl alcohol does have a noticeable smell, I personally find - but again, you're right that it probably isn't strong enough. I hadn't thought about the lanolin - in its pure form it's basically odourless, but it's true that impure stuff could have all sorts of distinctive smells. ~ mazca ^t|c 10:50, 16 February 2009 (UTC)

Actually I don't know what I was thinking with methanol. I was truly thinking isopropyl alcohol.

--Mrdeath5493 (talk) 21:12, 17 February 2009 (UTC)

The last few ingredients: "Linalool, Limonene, Citronellol, Courmarin, Geraniol, Anise Alcohol, Benzyl Cinnamate", are actually all perfume ingredients. The nasty hospital smell is likely p-Chloro-m-Cresol since cresol compounds smell bitter, irratating and "clean" in a hospitalish way. Triethanolamine may also contribute but I don't think its smell is strong enough to really register in this case. All the other ingredients that you see besides parfumcan be basically considered as scentless. Sjschen (talk) 16:53, 18 February 2009 (UTC)

The night sky

Is it possible to have a faint glow in the night sky around the moon during a lunar eclipse? There, you can both have your moments now. --Tango (talk) 21:48, 15 February 2009 (UTC)

If you're referring to what I think you are, then I don't think a lunar eclipse is a very good time to look for it, as the eclipsed moon is still quite bright. According to Google, the best time is in the middle of a clear moonless night in late February (the time of year is relevant because you don't want the milky way to obscure the view). You realize it's no fun this way, don't you? Algebraist 21:57, 15 February 2009 (UTC)

I know it's no fun, I just wanted to stop you two complaining... Shall I log out and word the question less obviously? --Tango (talk) 21:59, 15 February 2009 (UTC)

Best wait a few months first. Algebraist 22:02, 15 February 2009 (UTC)

But then I have to put up with you complaining for a few months... --Tango (talk) 22:03, 15 February 2009 (UTC)

how i make small text? —Preceding unsigned comment added by 194.80.240.66 (talk) 13:20, 16 February 2009 (UTC)

Uh, perhaps you could've looked at how Tango and Algebraist did it? In any case, anything you write between <small> and </small> is rendered in a smaller font size -- so typing "<small>small text</small>" results in small text. -- Captain Disdain (talk) 13:40, 16 February 2009 (UTC)

Do you have an account? If you do, login and you get an expanded toolbar that includes a button with that feature. Or try Captain Disdain's suggestion. A Quest For Knowledge (talk) 13:43, 16 February 2009 (UTC)

February 16

Time

Why do AM and PM start at 12:00 instead of 1:00? JCI (talk) 03:50, 16 February 2009 (UTC)

Because they stand for "before noon" and "after noon" in Latin. See 12-hour clock. --98.217.14.211 (talk) 04:33, 16 February 2009 (UTC)

Can I also add that am should be thought of as starting at 0:00 (just the maths does) CipherPixel (talk) 08:54, 16 February 2009 (UTC)

When does 12 a.m. mean noon?

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)

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)

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! Dbfirs 09:11, 16 February 2009 (UTC)

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)

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)

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)

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)

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)

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)

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)

I believe I am right in saying that trains in Britain are never timetabled to depart or arrive at midnight, for this very reason. DuncanHill (talk) 14:57, 16 February 2009 (UTC)

I disagree, most people can agree on what 12am means. There is some confusion, but it far less common then people make out. Nil Einne (talk) 14:18, 18 February 2009 (UTC)

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)

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)

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)

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)

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)

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)

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)

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)

What country has a state monopoly on teaching? Every country I know allows for private schools... --Tango (talk) 12:21, 16 February 2009 (UTC)

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)

In that case, I don't have the faintest idea what you're talking about. Do you actually have a factual question? --Tango (talk) 13:09, 16 February 2009 (UTC)

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)

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)

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)

Perhaps the other reason we don't teach the proof of the "three color map theorem" is because it doesn't have one, seeing as it isn't true... ;) --Tango (talk) 15:16, 16 February 2009 (UTC)

Spoilsport! --Stephan Schulz (talk) 15:28, 16 February 2009 (UTC)

Duh! The "three colour map theorem" works perfectly well. I once tried it out on the map of Down Under and had one colour left. --Cookatoo.ergo.ZooM (talk) 16:44, 16 February 2009 (UTC)

D'oh! How stupid we mathematicians have been all these years... why didn't you tell us?! --Tango (talk) 17:08, 16 February 2009 (UTC)

Do'h indeed. Sorry - I meant four-color...not three. You see what happens when they don't teach you stuff! I should have gone with Fermat's Last Theorem. SteveBaker (talk) 21:48, 16 February 2009 (UTC)

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)

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. Algebraist 22:02, 16 February 2009 (UTC)

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)

"most of science is pretty self-evident if you know where to look for evidence." goes into the quote-file:) DMacks (talk) 01:29, 17 February 2009 (UTC)

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)

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)

quantum mechanics(a particle in box)

It is possible that a particle in a box is equaly likely to moving in either direction. Iwant a disscation on it.Supriyochowdhury (talk) 14:03, 16 February 2009 (UTC)

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)

I think the OP meant "discussion". A Quest For Knowledge (talk) 16:11, 16 February 2009 (UTC)

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)

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)

Terpenes

are Terpenes base or acidic and can they be turned solid? —Preceding unsigned comment added by 76.14.124.175 (talk) 16:35, 16 February 2009 (UTC)

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)

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)

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)

Resolving small things is the same as resolving dim things for a camera or a telescope. Is the human eye any different? Nimur (talk) 17:31, 16 February 2009 (UTC)

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)

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). WilyD 18:03, 16 February 2009 (UTC)

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)

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)

"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)

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)

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)

hydroponics

do hydroponicaly grown plants grow faster than dirt grown plants? —Preceding unsigned comment added by 76.14.124.175 (talk) 18:11, 16 February 2009 (UTC)

According to our article, yes. A Quest For Knowledge (talk) 18:21, 16 February 2009 (UTC)

sudden freezing

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)

Supercooling. DMacks (talk) 18:34, 16 February 2009 (UTC)

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)

(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)

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)

See ice spike. StuRat (talk) 19:04, 16 February 2009 (UTC)

That's it! Thanks. A Quest For Knowledge (talk) 19:12, 16 February 2009 (UTC)

Water has many unusual and mysterious properties, some mysterious even to science. I've read that one experiment suggested water to be H_1.5O! ~AH1^(TCU) 23:21, 16 February 2009 (UTC)

Do you have a source for this? That doesn't make much sense to me.. there are Non-stoichiometric_compounds but water isn't one. Friday (talk) 17:51, 17 February 2009 (UTC)

See Water (molecule)#Quantum properties of molecular water. DMacks (talk) 19:02, 17 February 2009 (UTC)

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%.

Any help would be greatly appreciated!

— Sam 72.248.152.57 (talk) 20:07, 16 February 2009 (UTC)

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)

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)

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)

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? NeonMerlin 21:27, 16 February 2009 (UTC)

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.--NeoNerd 21:36, 16 February 2009 (UTC)

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 [13]. You might also have found [14] or [15]. 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)

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)

New colours

Could there be colours waiting to be discovered / thought up by our minds / whatever? - Jarry1250 ^{(t, c)} 22:01, 16 February 2009 (UTC)

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)

You also have combinations of those wavelengths to consider. --Tango (talk) 22:38, 16 February 2009 (UTC)

No you dont, waves superpose. —Preceding unsigned comment added by 129.67.37.225 (talk) 00:10, 18 February 2009 (UTC)

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)

Even among normally sighted people there's some variation in the cone responses; I believe they averaged over that. -- BenRG (talk) 01:56, 19 February 2009 (UTC)

(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)

(triple edit conflict!) You may want to look at tetrachromat. If tetrachromacy in humans exists, then the trichromatic colors won't cover all the colors tetrachromats can see. 152.16.144.213 (talk) 22:41, 16 February 2009 (UTC)

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)

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)

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)

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.

(also don't forget the hooloovoo). --Trovatore (talk) 22:58, 16 February 2009 (UTC)

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)

The question also is one of language. You might be able to imagine a new color, but how do you communicate that to others? See Minor Discworld concepts#Octarine.76.97.245.5 (talk) 00:24, 17 February 2009 (UTC)

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.

SteveBaker (talk) 01:22, 17 February 2009 (UTC)

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)

Steve: Brown is a desaturated, dark red. It is not somewhere outside the CIE diagram. Edison (talk) 01:52, 17 February 2009 (UTC)

Edison: There are different browns. Some are more a dark orange, or even dark yellow, than dark red.

Yeah - brown is nothing particularly special - it's a word we use to mean various dark shades of red/orange/yellow.

Speaking (typing) as a colour blind person, I see a lot more brown than normally sighted folk. I take this to mean that we tend call things brown when they don't have a 'clear' colour. Mikenorton (talk) 14:04, 17 February 2009 (UTC)

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)

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)

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)

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)

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)

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)

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)

@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)

(He doesn't have green receptors; see my response below the divider. -- BenRG (talk) 01:56, 19 February 2009 (UTC))

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)

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)

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.

Whether this actually happens, as I say, I don't know. But it's not as simple to refute as you're making it out to be. --Trovatore (talk) 03:40, 17 February 2009 (UTC)

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)

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)

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)

I get the feeling neither you nor Steve has read what I actually wrote. --Trovatore (talk) 20:47, 17 February 2009 (UTC)

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)

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)

Wait a minute — you're saying the red cones don't respond to 400nm light? Then why does it look purple? --Trovatore (talk) 23:28, 17 February 2009 (UTC)

(See my response below the divider. -- BenRG (talk) 01:56, 19 February 2009 (UTC))

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)

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)

And how exactly do you know that? --Trovatore (talk) 22:59, 17 February 2009 (UTC)

Because I've looked at the graphs and can see that the green and red lines are pretty much flat by that point. --Tango (talk) 23:00, 17 February 2009 (UTC)

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)

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)

(No such bump—see my response below the divider. -- BenRG (talk) 01:56, 19 February 2009 (UTC))

(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)

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)

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)

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)

Or even better, infragreen. The color of the Mushroom Planet. --Trovatore (talk) 03:41, 17 February 2009 (UTC)

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)

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)

New colors...Editing Break

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)

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)

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)

February 17

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)

Only in a subtractive color model do colors converge on black (which is not used for light). So I doubt you'll find a colorspace diagram for it, as they are modeled on light, not paint... --98.217.14.211 (talk) 00:43, 17 February 2009 (UTC)

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)

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)

The OP may also find Munsell color system (and some of the articles linked therein) of interest. Deor (talk) 12:53, 17 February 2009 (UTC)

Matter and Anti-Matter creation from energy

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

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 on or the other; that would violate conservation of charge, etc. (Please correct where necessary.) -- Aeluwas (talk) 09:41, 17 February 2009 (UTC)

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)

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?)

Many thanks, 81.140.37.58 (talk) 11:16, 17 February 2009 (UTC)

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. — Lomn 14:19, 17 February 2009 (UTC)

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)

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)

So there's no general rule? Ho Hum... —Preceding unsigned comment added by 81.140.37.58 (talk) 17:09, 17 February 2009 (UTC)

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)

Also, you might want to check out our Bodybuilding supplement article. A Quest For Knowledge (talk) 17:15, 17 February 2009 (UTC)

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.

--Mrdeath5493 (talk) 20:50, 18 February 2009 (UTC)

Most complex formula in Physics

What is the most complex formula that you know in Physics?--Mr.K. (talk) 11:55, 17 February 2009 (UTC)

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)

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:

$\rho {\frac {\partial ^{2}{\vec {\zeta }}}{\partial t^{2}}}=-\nabla (-\gamma p\nabla \cdot {\vec {\zeta }}-{\vec {\zeta }}\cdot \nabla p)-{\vec {B}}\times (\nabla \times (\nabla \times ({\vec {\zeta }}\times {\vec {B}})))+(\nabla \times {\vec {B}})\times (\nabla \times ({\vec {\zeta }}\times {\vec {B}}))+(\nabla \Phi )\nabla \cdot (\rho {\vec {\zeta }})$

(reference) which is the linearized magnetohydrodynamic equation of motion for plasma in terms of the plasma displacement vector, ${\vec {\zeta }}$. Of course, there are always more complex equations, but that's probably the longest one I've ever used. --Bmk (talk) 15:17, 17 February 2009 (UTC)

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)

As I'm not a physicist, I don't have much experience of long formulae, but this one is pretty nasty (Continuous Fourier transform#Spherical harmonics)):

$F_{0}(r)=2\pi i^{-k}r^{-(n+2k-2)/2}\int _{0}^{\infty }f_{0}(s)J_{(n+2k-2)/2}(2\pi rs)s^{(n+2k)/2}\,ds.$

The Laplace transformations and Laplace's equation articles will give you ammunition to impress the ladies at parties. --Mark PEA (talk) 21:40, 17 February 2009 (UTC)

It's been a while since I used it, but $R=\kappa T$ (see Einstein's field equations) still gives me nightmares. Don't think it's complicated? It's actually (if I remember correctly) 4-dimensional, 4th order non-linear differential equation, with the only saving grace being a couple of symmetries. Confusing Manifestation(Say hi!) 22:52, 17 February 2009 (UTC)

Hmm, how about the Standard Model Lagrangian? -- BenRG (talk) 23:35, 17 February 2009 (UTC)

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)

Microsoft Office Live Workplace for Linux users

This question has been moved to the Computing Desk, Nimur (talk) 16:31, 17 February 2009 (UTC)

Liquid density

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?

A.4/3 ρ      B.5/3 ρ
C.3/2 ρ      D.3ρ  —Preceding unsigned comment added by 116.71.33.96 (talk) 13:12, 17 February 2009 (UTC) 

Please do your own homework.

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)

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. — Lomn 14:14, 17 February 2009 (UTC)

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)

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)

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)

Incidentally, have you read our articles: Naked singularity and Cosmic censorship hypothesis? (Lots of tags at the top of them both, so they may not be very good - I haven't read them recently.) --Tango (talk) 18:41, 17 February 2009 (UTC)

I did, but unfortunately they didn't really deal with the question above (or if they do it was in an over-my-head technical area). 63.95.36.13 (talk) 22:50, 17 February 2009 (UTC)

Coincidentally, we covered a similar question in january EverGreg (talk) 18:16, 17 February 2009 (UTC)

Nuclear submarine crash

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)

Hmm. Are you asking because you've read this article (or another one on the same subject) or is this just a great coincidence, considering that was published yesterday? -- Aeluwas (talk) 17:00, 17 February 2009 (UTC)

Yes, I was in fact trying to tie together X and Y, but I guess absolute explictness trumps collegial allusiveness. BrainyBabe (talk) 17:12, 17 February 2009 (UTC)

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)

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)

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)

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)

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. --Sean 21:59, 17 February 2009 (UTC)

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)

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)

You're referring to USS San Francisco (SSN-711)#Collision with Seamount? --Carnildo (talk) 02:18, 18 February 2009 (UTC)

Failure modalities:

• 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.

87.115.43.168 (talk) 20:19, 17 February 2009 (UTC)

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)

Wow, 87.115, you sure know your stuff! I'd buy you a drink if I could. BrainyBabe (talk) 21:17, 17 February 2009 (UTC)

Resolved

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)

Aren't military subs designed to be as quiet as possible? --Tango (talk) 14:47, 18 February 2009 (UTC)

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 [16]. 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)

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)

The road to Xibalba

The lead section of Xibalba states: Another physical incarnation of the road to Xibalba ... is the dark rift which is visible in the Milky Way. Is this an example of a dark cloud constellation? Astronaut (talk) 18:03, 17 February 2009 (UTC)

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)

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)

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)

I just want to know, exactly where is the bunny in the picture above? ~Amatulić (talk) 21:42, 18 February 2009 (UTC)

Health: green tea leaves v. cabbage leaves

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)

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)

Potential effects of tea on health makes many claims for green tea's health benefits; Cabbage makes fewer. They are quite different plants and they presumably contain many different trace chemicals. Tempshill (talk) 21:27, 17 February 2009 (UTC)

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)

"Large amount" is rather overstating the case, and our article on Mount Erebus doesn't mention it, but see this New Scientist article (which is the first hit in a Google search for Antarctica volcano gold). Deor (talk) 20:16, 17 February 2009 (UTC)

sort of alchemy

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)

I believe you are referring to nuclear transmutation. Yes, it is possible but is too expensive to be worth the cost. A Quest For Knowledge (talk) 20:35, 17 February 2009 (UTC)

And if it were inexpensive to do, the supply of gold would increase substantially, which would lower the price of it. --Mark PEA (talk) 21:28, 17 February 2009 (UTC)

yes, but is the resulting material radioactive, or stable? —Preceding unsigned comment added by 65.167.146.130 (talk) 21:34, 17 February 2009 (UTC)

Per our article on the synthesis of noble metals, Au₁₉₇, the only stable isotope of gold, can be produced from mercury. Likely there exists a path from lead to Au₁₉₇, but it's also quite likely more complicated. — Lomn 22:01, 17 February 2009 (UTC)

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?

22:01, 17 February 2009 (UTC) —Preceding unsigned comment added by Scofield Boy (talk • contribs)

I don't know for certain, but it may play a role in detoxifying potentially harmful compounds and/or removing peroxides from the blood. – ClockworkSoul 22:34, 17 February 2009 (UTC)

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)

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)

First thing, human growth hormone is completely different from and unrelated to GHB (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.

1. Critical evaluation of the safety of recombinant human growth hormone administration: Statement from the Growth Hormone Research Society. J Clin Endocrinol Metab 2001;86:1868 – 187025.. I would like to note that according the Growth Hormone Research Society webpage they are sponsored by a variety of corporate entities and thus may have outside interests. I do not know enough about the sponsership to make that call.
2. 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."
3. 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.
4. 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.
5. 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)

AIDS and Non-Hodgkins Lymphoma (NHL) are certainly associated. NHL is the most common lymphoma affecting people with AIDS; NHL is an AIDS-defining illness in the presence of a positive HIV test. - Nunh-huh 04:37, 18 February 2009 (UTC)

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)

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)

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)

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)

Do you have any references that it is "commonly" used as a date rape drug, other than tabloid newspapers? According to this paper [17], 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)

- 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)

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)

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)

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 1/770000mols/L so 300 units/mL is ~39mM 0.39mM which if divalent will add an extra ~117*10^-3 1.1710^-3: a 50% 0.5% increase in ionic strength. (edit. redid those calculations and found I was off by a factor of 100... 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)

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)

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)

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)

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)

I don't know about the other questions (you'd have to look up electronegativity tables, I think), but for #1 take a look at the infobox on sodium chloride. Confusing Manifestation(Say hi!) 05:55, 18 February 2009 (UTC)

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)

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)

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)

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)

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)

Electrode spacing seems to matter little with 200 ml of concentrated brine solution.Edison (talk) 19:55, 18 February 2009 (UTC)

Bacterial illness

My doctor told me that bacterial illnesses are mostly caused by more than one kind of bacteria. Is that true?

More generally, what is known about combinations of infecting agents (be it bacteria or others, possibly mixed)? 93.132.168.56 (talk) 08:15, 18 February 2009 (UTC)

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)

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.

--Mrdeath5493 (talk) 17:44, 18 February 2009 (UTC)

So my doctor is wrong is stating that bacterial illnesses are mostly caused by more than on kind of bacteria? 93.132.168.56 (talk) 20:01, 18 February 2009 (UTC)

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.

--Mrdeath5493 (talk) 20:18, 18 February 2009 (UTC)

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)

Yeah you're right. *Many* are. --Mrdeath5493 (talk) 21:46, 18 February 2009 (UTC)

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)

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)

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)

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)

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)

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)

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)

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)

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!

Siouxdax (talk) 09:58, 18 February 2009 (UTC)

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)

That is exactly what I was looking for! I don't know why I thought he was in the same time as Archimedes. Thanks so much! Siouxdax (talk) 10:25, 18 February 2009 (UTC)

Clarification required

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?

For a verifiable source try the BBC —Preceding unsigned comment added by 121.221.4.199 (talk) 10:49, 18 February 2009 (UTC)

I'm guessing you have read Cubit and in particular Cubit#History_of_the_different_cubits? If you believe the article to be incorrect i'd suggest discussing it on the relevant talk-page for the article, and cite your sources. 194.221.133.226 (talk) 11:20, 18 February 2009 (UTC)

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)

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: [18] 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)

Electron composition

what is an electron made of?Vipinchandranp (talk) 13:52, 18 February 2009 (UTC)

Have you even tried to read electron ? As you could read there, the electron has no known substructure. So it is, as far as we know at the moment, a fundamental particle. TheMaster17 (talk) 14:06, 18 February 2009 (UTC)

Whoever find the answers to this question wins more than a couple of noble prizes.Sjschen (talk) 16:13, 18 February 2009 (UTC)

RadioShack Weather Stations

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)

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)

Following EC: Yes. [19] [20]. 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 [21] might be willing to share their opinions. [22]--76.97.245.5 (talk) 17:31, 18 February 2009 (UTC)

If you do get a PWS, please consider hooking it up to www.weatherunderground.com so that everyone in the world can check it! Franamax (talk) 00:04, 19 February 2009 (UTC)

Is there any scientific evidence backing 9/11 conspiracy theories?

I am currently embarking a major project to clean up all the articles relating to 9/11 conspiracy theories. Part of the problem is that 9/11 conspiracy theorists keep trying to insert their conspiracy theories into the articles as if they are legitimate. Another part of the problem is that some good-faith editors don't quite understand what WP:NPOV really means and inadvertently give too much undue weight to fringe theories. I am planning on starting with the main article on 9/11 conspiracy theories. I've already posted my intent on the main article's discussion page, [23]. I will proceed until every article on 9/11 Truth Movement, Loose Change, etc. is in accordance to WP:NPOV. In order to be fair and balanced, what I would like to is this. Are any reliable sources from the scientific community claiming that 9/11 conspiracy theories are true? A Quest For Knowledge (talk) 15:50, 18 February 2009 (UTC)

"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)

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)

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)

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)

Popular Mechanics did a well recieved debunking of the most popular conspiracy theories concerning 9/11.

--Mrdeath5493 (talk) 17:26, 18 February 2009 (UTC)

Yes, Popular Mechanics did an excellent job. They even turned their article into a book [24], but finding reliable sources to debunk 9/11 conspiracy will be easy. The hard part will be finding reliable sources that are in favor of 9/11 conspiracy theories. A Quest For Knowledge (talk) 17:46, 18 February 2009 (UTC)

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)

20/20 hindsight is, as always, an incredibly impressive and incredibly useless ability. --Tango (talk) 19:06, 18 February 2009 (UTC)

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)

No, it applies to everything. It's easy to say "I would have foreseen that" after the event. --Tango (talk) 01:28, 19 February 2009 (UTC)

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)

Does this count as scientific evidence? [25] - Azi Like a Fox (talk) 22:42, 18 February 2009 (UTC)

Er... no. --Tango (talk) 01:28, 19 February 2009 (UTC)

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, [26]. 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)

Speculation on Glaucoma and HSV

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".

Read to the bottom of http://www.nei.nih.gov/health/glaucoma/glaucoma_facts.asp and you find the exact cause of glaucoma is unknown.

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?

4. Here's something which really surprised me at http://en.wikipedia.org/wiki/Herpes_simplex and http://en.wikipedia.org/wiki/Alzheimer_disease;

"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.

Thank you.Stevej000 (talk) 16:35, 18 February 2009 (UTC)

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)

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. – ClockworkSoul 21:37, 18 February 2009 (UTC)

ClockworkSoul, you are a candidate to work at the Resource Exchange, where we never ever do that kind of stuff, none of the time. Nice work! :) Franamax (talk) 01:20, 19 February 2009 (UTC)

Thanks again folks, I no longer feel like a total crackpot! Stevej000 (talk) 12:07, 19 February 2009 (UTC)

Is it a coincedence 2... ?

http://www.islamreligion.com/articles/215/

just follow this and tell me what do you think....? —Preceding unsigned comment added by Mjaafreh2008 (talk • contribs) 17:06, 18 February 2009 (UTC)

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)

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)

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)

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)

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)

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)

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.G 05:35, 19 February 2009 (UTC)

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.contribs 06:41, 19 February 2009 (UTC)

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)

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

http://www.55a.net/firas/english/

thank you for the concern —Preceding unsigned comment added by Mjaafreh2008 (talk • contribs) 14:21, 19 February 2009 (UTC)

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)

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...

If they are real world capacitors there are dielectric losses (leakage current) and series resistance (ESR). http://en.wikipedia.org/wiki/Capacitor. If they are ideal capacitors I don't know.Stevej000 (talk) 18:21, 18 February 2009 (UTC)

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)

Global warming. Cuddlyable3 (talk) 00:17, 19 February 2009 (UTC)

>>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.

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)

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)

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.

--Mrdeath5493 (talk) 20:30, 18 February 2009 (UTC)

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)

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)

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)

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)

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.

What's wrong with that argument? What does the tip of the laser beam look like? 93.132.168.56 (talk) 20:44, 18 February 2009 (UTC)

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)

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)

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)

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)

You are not giving medical advice, are you? 93.132.168.56 (talk) 21:28, 18 February 2009 (UTC)

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)

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)

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)

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)

The electromagnetic wave equation is:

${\Bigg (}\nabla ^{2}-{1 \over {c}^{2}}{\partial ^{2} \over \partial t^{2}}{\bigg )}\mathbf {E} \ =\ 0$

For the sake of illustration, let's assume spherical symmetry, so this reduces to:

${\Bigg (}{1 \over r}{\partial ^{2} \over \partial r^{2}}r-{1 \over {c}^{2}}{\partial ^{2} \over \partial t^{2}}{\bigg )}\mathbf {E(r,t)} \ =\ 0$

It is straightforward to demonstrate that any solution of the form:

$\mathbf {E(r,t)} ={1 \over r}f(c\ t-r)$

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)

Thank you, now I see. f could be (composed of) some patchwork function like $f(s)=s^{3}$ for $s>0$ and $f(s)=0$ else. 95.112.165.196 (talk) 08:35, 19 February 2009 (UTC)

(I edited the math in the above to make it a bit clearer.) Vespertine1215 (talk) 16:31, 19 February 2009 (UTC)

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 ([27] 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 ([28] 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)

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.

--Mrdeath5493 (talk) 21:03, 18 February 2009 (UTC)

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-huh 00:05, 19 February 2009 (UTC)

You could also add hemochromatosis to the short list of conditions that benefit from a good bloodletting. --- Medical geneticist (talk) 00:26, 19 February 2009 (UTC)

...and some porphyrias. --Scray (talk) 04:12, 19 February 2009 (UTC)

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)

Oh yeah don't forget to check out Maggot therapy too.--Mrdeath5493 (talk) 21:15, 18 February 2009 (UTC)

While you are at it, be sure to miss Purification Rundown which promises you bonus IQ points as you get purer.Cuddlyable3 (talk) 00:14, 19 February 2009 (UTC)

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)

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)

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)

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.contribs 04:43, 19 February 2009 (UTC)

Purple Orange

File:PurpleOrange.JPG

My mom was peeling oranges when she came across this ! Does anyone know why? Bewareofdog 23:09, 18 February 2009 (UTC)

It looks like a blood orange to me. Why it would be mixed up with regular oranges, I don't know. --Tango (talk) 23:17, 18 February 2009 (UTC)

February 19

xkcd science reference

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.

I've never heard of this. Can anyone enlighten me to what Mr. Munroe is talking about? 90.234.71.57 (talk) 00:32, 19 February 2009 (UTC)

The title of the comic suggests that our article dark flow may be relevant, and indeed it is. Algebraist 00:40, 19 February 2009 (UTC)

Ahh, silly me! Should've seen that :) Thanks! 90.234.71.57 (talk) 00:43, 19 February 2009 (UTC)

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)

No, not at all. As the article explains, the Great Attractor is well within the visible universe. Algebraist 01:00, 19 February 2009 (UTC)

When reading XKCD, it's frequently necessary to read the popup that appears when you hover the mouse over the cartoon. SteveBaker (talk) 02:10, 19 February 2009 (UTC)

Yes, but I doubt the Pioneer anomaly is due to the force of my love would have helped much in this instance.... --Trovatore (talk) 02:15, 19 February 2009 (UTC)

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)

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)

This is an encyclopedia, you know: pioneer anomaly. Algebraist 03:47, 19 February 2009 (UTC)

FYI, they aren't still working. At least, they aren't communicating with Earth any more. You may be thinking of the Voyager probes. --Tango (talk) 13:42, 19 February 2009 (UTC)

Did you check the forum? — DanielLC 17:45, 19 February 2009 (UTC)

Boyle's Law

What is an everyday situation that involves Boyle's Law? I had thought of tire pressure but that doesn't work. Thanks! Reywas92^Talk 02:22, 19 February 2009 (UTC)

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)

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.

Compare how a completely sealed pouch of airline peanuts looks when you're aloft vs after landing. DMacks (talk) 02:39, 19 February 2009 (UTC)

I suppose resisting the temptation to actually eat the peanuts in flight is a bit easier these days  :( hydnjo talk 02:54, 19 February 2009 (UTC)

Thanks! Anything that goes the other way? Increase the volume to decrease the pressure, or decrease the volume to increase the pressure. Reywas92^Talk 02:42, 19 February 2009 (UTC)

Compression stroke of internal combustion engines. DMacks (talk) 02:46, 19 February 2009 (UTC)

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. -hydnjo talk 03:48, 19 February 2009 (UTC)

—Preceding unsigned comment added by TungstenCarbide (talk • contribs) 04:02, 19 February 2009 (UTC)

Eyes wide shut?

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)

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:

"Eyelid closure is an active process that requires contraction of orbicularis oculi and inhibition of levator palpebrae superioris"

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)

...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)

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)

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)

We have an article on Weighing scales which has lots of different pictures of different types and models of scales. Do any of these help you? --Jayron32.talk.contribs 06:35, 19 February 2009 (UTC)

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)

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)

• 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. +

— B00P (talk) 08:27, 19 February 2009 (UTC)

Oh, OK. I had heard it was too bright to miss (as bright as the full Moon), but if that's not the case, then definitely. 128.194.250.39 (talk) 08:38, 19 February 2009 (UTC)

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)

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)

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)

All over Europe, for three weeks? Algebraist 13:58, 19 February 2009 (UTC)

Doesn't it ever get cloudy in Europe for 3 weeks at a time ? StuRat (talk) 21:31, 19 February 2009 (UTC)

Grooves (archaeology)

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)

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)

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)

Apple juice

If I make apple juice at home, what can I add to it to prevent oxidation - at least for some hours? Mr.K. (talk) 13:22, 19 February 2009 (UTC)

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)

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)

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)

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)

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)

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?

Does our caffeine article explain this ? StuRat (talk) 13:39, 19 February 2009 (UTC)

(ec) Our article on caffeine has a pretty extensive section on pharmacology and its mechanism of action. You should be able to get a good start there; let us know if you're stuck on anything. TenOfAllTrades(talk) 13:42, 19 February 2009 (UTC)

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)

Time travel survival

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:

1. Water purifier (drinking water is essential for life)
2. Storm-proof lighter (fire keeps you warm and helps you cook)
3. Swiss knife (comes handy in many situations)
4. Net (for catching food)
5. A medical kit (for treating injuries and diseases)

Am I forgetting any important objects? --83.45.155.43 (talk) 15:50, 19 February 2009 (UTC)

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)

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)

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)

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)

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)

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)

You picked yourself up from the Permian? Nimur (talk) 18:48, 19 February 2009 (UTC)

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)

I'm thinking you need better shelter to survive for a year.

1. Sturdy 1-person tent
2. A sleeping bag that keeps you alive in -20F temps
3. Bow and arrows (they'd be reusable)
4. Camouflage that you can wear for a year
5. Some sort of pot/pan/utensil set

And before you leave, I would learn how Bear Grylls makes fire.--Mrdeath5493 (talk) 19:12, 19 February 2009 (UTC)

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)

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...

Basics

what is the best easy going reference which discuss the basic concepts about physics...thanks alot .

Physics for Scientists and Engineers (~$150 US) doesn't cut corners. It is considered "basic" at the college-level. What is your approximate grade level or mathematical background? That will help decide the right book or resource for you. Nimur (talk) 18:33, 19 February 2009 (UTC)

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)

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)

How can i get this books for free ,pdf if possiblThe Feynman Lectures on Physicsthanks ....

Coincidentally, I have Feynmann on PDF, but I don't think Gmail can handle such large attachments ~70MB total. Someguy1221 (talk) 20:57, 19 February 2009 (UTC)

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?

Please do your own homework.

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)

Squirting Orgasm

How do a give a woman a squirting orgasm?

Buy her a squid. Hang on. Thought you meant organism! Aw shucks.

I don't believe there is a guaranteed method. There isn't even agreement on whether it is possible at all. See Female ejaculation. --Tango (talk) 20:51, 19 February 2009 (UTC)

Blue supergiant

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)

See blue supergiant and supergiant - they aren't main sequence stars. I've never 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)