:If your concern is the satisfaction of your future partner, then being relaxed about it is more important than anything else. The "first time" is rarely very good, because you have to learn to understand each other's desires and to read each other's signals. Create a relaxed and romantic atmosphere, take your time, and be generous with both compliments and [[caressing]] and other forms of affectionate touching. --[[User:Lambiam|Lambiam]][[User talk:Lambiam|<small><sup>Talk</sup></small>]] 01:36, 10 August 2006 (UTC)
:If your concern is the satisfaction of your future partner, then being relaxed about it is more important than anything else. The "first time" is rarely very good, because you have to learn to understand each other's desires and to read each other's signals. Create a relaxed and romantic atmosphere, take your time, and be generous with both compliments and [[caressing]] and other forms of affectionate touching. --[[User:Lambiam|Lambiam]][[User talk:Lambiam|<small><sup>Talk</sup></small>]] 01:36, 10 August 2006 (UTC)
>>My only other sugestion is don't drink to much alcohol, high blood pressure pills will effect sexual function, and expecially anti-depresents to a much higher degree than reported, other than that you might want to talk to a doctor and try viagra oc ciallias, it even helps people with no problem at all, and just may be the confidence boster you need.
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August 1
The evolutionary value of doing calculus?
Human beings evolved to survive, but why did we evolve the ability to do calculus?
I do not understand why humans can do so many clever things that are quite unnecessary for survival. Surely evolution is parsimonious and abilities that are of no value to surviving in the savannah environment should never have been developed? --62.253.44.34 00:18, 1 August 2006 (UTC)[reply]
There isn't a gene for being able to calculus. Rather, doing calculus comes naturally (with some training) to any human with a firm grasp on symbols, the concept of reducing complex problems to tiny steps, and a few other basic skills that definitely have evolutionary value. StuRat 00:40, 1 August 2006 (UTC)[reply]
I think the questioner was trying to ask why intelligence evolved in humans, and used calculus as an example. --Bowlhover 03:31, 1 August 2006 (UTC)[reply]
Intelligence is a major advantage! It allows humans to solve difficult problems, use tools (as noted by Melchoir), comunicate effectively, resolve conflicts nonviolently, waste time on the computer :), and many other things. The ability to do calculus is just an extension of the ability to do arithmetic and count, albeit a pretty big extension. Emmett5 04:01, 1 August 2006 (UTC)[reply]
There's actually a stub at Evolution of intelligence that needs work, if people here are interested. --Allen 04:25, 1 August 2006 (UTC)[reply]
I added to it. StuRat 21:48, 5 August 2006 (UTC)[reply]
(Warning: this opinion is very biased and discriminating. Don't take it entirely seriously.) I don't think humans have ability to do calculus genetically coded in them. Humans have evolved such that they could comprehend more and more abstract thoughts and plans (symbols, as StuRat says), and as they also learnt how to count, the ability to do algebra came naturally. Caluclus, on the other hand, is not like that. Most people don't understand calculus instinctively but have to be thought rules of calculus written in the language of algebra. The basis of calculus were invented by a few brilliant mathematical geniuses who did have a calculus instinct by fluke, e.g. Newton and Leibniz (real calculus), Euler (complex analysis). Once they wrote the foundations of a theory in the language of pure mathematical formulas, others could derive new results in calculus by manipulating the prior results using the rules of algebra. – b_jonas 12:58, 1 August 2006 (UTC)[reply]
FYI Norbert Weiner as a child prodigy and after learning algebra, invented the calculus only to discover it had already been invented. (He entered college at age eleven.) This implies something; I'm not sure what. -Wfaxon 23:57, 8 August 2006 (UTC)[reply]
It implies that it's a real thing, not just something silly somebody made up (like most of psychology, for example). It also implies he should have spent a bit more time studying existing theory before developing his own. StuRat 01:39, 9 August 2006 (UTC)[reply]
I was thinking more along the lines that at the turn of the 18th century you needed mature world-class geniuses to invent the calculus; at the beginning of the 20th century all you needed was genius. Either that or the way that algebra was taught in 1900 itself implied the calculus since the authors of the algebra texts Weiner learned from certainly knew it. BTW one really shouldn't be too critical of a nine-year-old's lack of research back then: No internet! -Wfaxon 04:21, 9 August 2006 (UTC)[reply]
"Years of laboratory research have saved me from having to spend hours doing research at my local library." StuRat 18:26, 9 August 2006 (UTC)[reply]
The nice thing about general intelligence is that it is very flexible—you're not locked into one adaptionary box. That makes it a tremendous evolutionary advantage when you are a species that is not terribly fast, strong, or with acute senses relative to the sorts of predators around you. It also means that you can migrate with relative ease and don't have to wait hundreds of generations to develop (or lose) a shaggy coat. ;-) --Fastfission 12:50, 1 August 2006 (UTC)[reply]
I used calculus as an example of intelligence. Although we take our intelligence and the man-made world for granted, I think it is very odd that it evolved at all and we can do all these things. Its as if an earthworm had somehow evolved the ability to run at 60mph - it doesnt need it to survive in its environment, so the ability to run at 60mph should never have evolved. Yet in humans this is what has happened - you dont need much intellect to survive (other animals get along without it) yet somehow we have developed this intellect and ability to do things such as eg calculus which natural selection has played no part in. How? Why?
I've heard a couple of differing opinions on what the evolutionairy advantage of our intelligence is. Some propose that our ancestors required enhanced cognitive abbilities so they could better use the tools they had. One particulair example I liked was how ancient humans might have had to use their brain to figure out the trajectories the rocks they threw would take. It could also be a result of the tight social groups we form. Being able to accurately communicate with your fellow man would be a big advantage (and this would require some decent brain power).
Whatever the basis of our smarts may be, you should remember that we haven't stopped evolving. Things like calculus, rocket science, chemistry, sudoku puzzles and Barney the dinosaur all fill a niche in our society and thus are not without purpose. So our ancestors did not do calculus because it didn't have any use to them, being able to hit a gazelle at 50-100 yards away did and from these humble beginnings the rest followed. -Pascal
The answer is that we did not evolve the ability to do calculus, or mathematics in general — that's why we are so incredibly bad at it. Consider the fact that even quite simple computers, like the one on your desk, can outperform humans in basic arithmetic by a factor of about a U.S. billion (that's 109), but have enormous trouble with tasks like, say, speech recognition, or catching a thrown object, which we did evolve for. Our ability to do any mathematics at all is basically a side effect of us having evolved, for other reasons, enough abilities for abstract thought to — barely — allow universal computation. That means we can, in principle, do anything a computer can do; it doesn't mean we can do so in any reasonably efficient manner. To use a programming analogy, all our conscious thought processes happen at an extremely high level, far from the hardware — indeed, the fact that they are subject to conscious monitoring implies that. We have efficient low level primitives for all sorts things that are useful for survival in nature, but for things we didn't evolve such primitives for, we need to rely on high-level processes that are extremely inefficient, since they are built upon systems that weren't designed for such use at all. —Ilmari Karonen (talk) 22:19, 1 August 2006 (UTC)[reply]
Nice analogy, Ilmari; thanks. I'd never thought of it like that. --Allen 04:52, 2 August 2006 (UTC)[reply]
Consider, for example, our skills at language. Noam Chomsky's famous hypothesis is that there is a kind of language gizmo in the human brain that can learn any language, because it carries some sort of pre-prepared algorithm for verbal communication. But extensive research seems to suggest that their is no such thing as a central language processor in the human brain. Rather, language processing is distributed all over the brain: when a illiterate child looks at words, activitiy is seen in several regions in the rear part of the brain; when they listen to words, their brain shows activity in an area in its center; when they speak nouns, activity occurs in a different area of the central brain, nearer the top; when they speak verbs, activity occurs in two separate areas, one nearer the front, the other nearer the back.
In 1861, when Paul Broca discovered significant damage to an area of the brain (now called Broca's area) while doing an autopsy on a patient with a verbal disability, observers worldwide thought he might have discovered something very significant. Broca's area is on the left side of the brain, near the front; damage there will cause sufferers to speak haltingly, and mostly in nouns; they generally understand others who speak to them, and realise that they are unable to speak. Broca's patient, Leborge, was nicknamed 'Tan', because it was one of a handful of words he could say. Carl Wernicke made a similar discovery, in an area now called Wernicke's area. Wernicke's area is also on the left side of the brain, but further back. Sufferers of damage in Wernicke's area can speak fluently, but their speech is essentially a randomly assorted jumble of words.
What this shows is that our linguistic skills are not a discrete brain function. Rather, they are an aggregate of dozens, possibly hundreds of more basic skills that may have been evolved for very different reasons, such as hunting, scavenging, or tool making. Math is probably the same way. One of the most remarkable features of the human brain is its 'plasticity', or ability to rewire itself to perform completely new tasks. The most remarkable example of this is a woman who had a stroke that caused massive damage to the left hemisphere of her brain. For some time, she was unable to read, until she was coached into using her right brain to interpret symbols. She completely rewired her brain to have a totally different approach to symbols; she went from a scientific, logical approach to the interpretation of the alphabet to seeing them as an artist. Likewise, people who are talented with math have brains that have assembled basic, simple functions into a more complex skill. It is like a computer rewriting its own software to use its basic functions in a totally new way.
By the way, this is precisely the debate between Darwin and Wallace. Wallace argued that natural selection would have only had to make humans a little smarter than other big apes currently are in order to have an unbelievable evolutionary advantage, and didn't believe there was any reason for a "savage" to develop a conscience or complicated moral sensibility, much less high intelligence. Darwin countered with his theory of sexual selection, arguing that bigger brainpower might have been related to impressing females, in the same way that a peacock's feathers serve no functional purpose outside of being attractive to the ladies. Wallace never bought into that, though (it probably didn't help that he was left at the alter—he never could accept the idea that female mates were in charge of choosing attractive mates), and instead went the direction of thinking that a conscious spiritual force had guided human evolution into its present position. Darwin was understandably horrified and wondered if Wallace hadn't "murdered" their "child". --Fastfission 04:39, 2 August 2006 (UTC)[reply]
As the Donna Nook fire range has been used by A-10 Thunderbolts for cannon practice and the A-10s have a GAU-8/A Avenger Gatling gun, which indeed fires depleted uranium armor-piercing shells, is there any publicly available information on the health risks associated with the place? Does anyone know whether the Freedom of Information Act could be used to request information from the MoD or is it not applicable? Thanks, E Asterionu talking to me? 00:35, 1 August 2006 (UTC)[reply]
Basic Burn Question
I looked on web md, but they skirted the question. I just got a minor burn by grabbing a hot pan. It's been two or three days and the small burn has turned into a small raised blister that doesn't hurt at all unless put under particularly hot water. The raised blister's really irritating me, and i was wondering if after three days, the skin has formed underneath the scab sufficiently for me to pop it, let the liquid out, and peel off the scab to let the new skin heal over. If not, when, if ever, is this a good idea? Should I never pull the scab off, because it seems to me that that scab is not what's going to become my new top skin layer. Thanks. Sashafklein 05:57, 1 August 2006 (UTC)[reply]
My understanding is that as long as there's fluid in the blister, the flesh beneath is vulnerable. All the literature I've read says never to pop blisters, so I ice them, which decreases the fluid pressure and makes them less irritating. Technically you're not supposed to apply ice directly to burns, but you're not actually applying it to the burn, you're applying it to the blister. Also, even after several days the application of cool can have anti-inflammatory benefits. Also, cover the blister with a bandaid or a loose dressing to keep it from bursting or being bumped.--Anchoress 07:01, 1 August 2006 (UTC)[reply]
Actually, when you burn your skin the best thing to do is to cool it down with warm water (not hot of course, but about body temperature). This makes it hurt more at that moment, but it will prevent a blister from forming and thus reduces pain later on. At least, I heard this once and tested it on one occasion, and in my case it worked. DirkvdM 12:24, 1 August 2006 (UTC)[reply]
I hadn't heard that warm water is better than cold, I'd just heard that ice isn't good for burns. But we're talking about a 3 day old burn here, IMO ice is better.--Anchoress 18:24, 1 August 2006 (UTC)[reply]
Thanks. Should it just eventually deflate or peel off? Sashafklein 07:05, 1 August 2006 (UTC)[reply]
Yeah, it'll either deflate or end up getting punctured on its own. If the latter happens you should wash it very carefully and put some antiseptic (e.g. Neosporin) on if you have it, and probably a bandage, to prevent infection. I've done this an embarrassingly high number of times (something about the way my toaster is made seems to encourage me to burn my fingers trying to get things out of it). --Fastfission 12:48, 1 August 2006 (UTC)[reply]
BTW Neosporin isn't an antiseptic, it's a topical antibiotic.--Anchoress 18:24, 1 August 2006 (UTC)[reply]
I've been a burn surgeon for many years and this is my advice:
The fluid in a burn blister is clean, but not sterile and eventually will get infected. As long as the blister is intact, the burn wound is protected and relatively painless. If these blisters are small and do not interfere with function (e.g. not over a joint, or so large that they compress the circulation to a body part) then I leave them alone for 1 - 2 days. If it starts to get red, indicating infection, they need to be removed and topical antibiotics applied. If there is suspicion that the burn is fairly deep, then I remove the blister so that it can be inspected on a frequent basis. If there is any doubt, you should see a burn specialist ASAP.
BTW, cold water applied within seconds of a superficial burn will tend to lessen the degree of injury - but it must be done RIGHT AWAY. Best of luck. --Ronbarton 21:35, 6 August 2006 (UTC)[reply]
Diff. b/w university and college
my question is wat is the difference b/w university/college..and university/ institute or college/institute??
The common-usage meaning and specific definition varies somewhat with country. College would be a good start. DMacks 07:28, 1 August 2006 (UTC)[reply]
If you tell us which country you are from, we might be able to be more specific regarding the use of the words college and university. However, academic institutes tend to be research orientated, while colleges and universities will offer teaching as well as research. Rockpocket 07:53, 1 August 2006 (UTC)[reply]
"Institute" is a term which generally has a lot of flexibility. The Massachusetts Institute of Technology is basically a university, while the Institute for Advanced Study is more like an academic think-tank. The terms "university" and "college" are more specifically defined in the United States than is the term "institute". --Fastfission 12:43, 1 August 2006 (UTC)[reply]
Ever been to a university? They have many colleges.
Maybe in your country. In Australia, a college is either a tertiary learning institution of lower status than a university, or the last 2 years of high school. Universities here don't have colleges within them, as far as I know. JackofOz 14:12, 1 August 2006 (UTC)[reply]
In the UK, "college" is used sometimes to mean a further education institution of lower status than a university; sometimes as a synonym for university, and for some universities, including the most prestigious, a university is divided into semi-autonomous colleges (see e.g. King's College, Cambridge). Some colleges are called schools (see e.g. London School of Hygiene & Tropical Medicine) but nobody ever uses the term "going to school" to refer to further education (this is a significant difference of usage with the US). Notinasnaid 15:05, 1 August 2006 (UTC)[reply]
Want more confusion, see the article about the University named the College of Charleston. It can't even decide what it is! Well, it was a college that gained university status and decided to keep the old name for the undergrad and only change to University of Charleston for graduate courses. --Kainaw(talk) 14:57, 1 August 2006 (UTC)[reply]
Maybe a university that's named "College" would be a good place to go after attending Baltimore City College, which is a high school. DMacks 16:39, 1 August 2006 (UTC)[reply]
In the U.S. there are similarly several University High Schools associated with Universities. Rmhermen 01:05, 2 August 2006 (UTC)[reply]
(edit conflict) In the UK there are plenty of schools called colleges (though then are often private schools - and to confuse matters further, they call them public schools - e.g. Fettes College). There are also sixth form colleges, which are further educational establishments, as well as higher educational establishments, called colleges. I have never heard of an UK academic institution that teaches though, and neither have i heard of a British university be anything other than a higher educational establishment. I await correction on this. So the bottom line, i think, is that college is a term that can cover a lot of different educational establishments, but university and institution are more precise (though there are possible exceptions). Rockpocket 17:28, 1 August 2006 (UTC)[reply]
The Institute Of Education is part of London University, and teaches teachers.
In the U.S., generally a stand-alone college is more narrow in scope than a university, which includes several divisions usually called "colleges." For example, I graduated from the College of Arts and Sciences at the University of Oklahoma, although I took courses in other colleges (e.g. a course in the College of Business). A stand-alone college may be as rigorous as a university, or it may be less so, as is the case for community colleges, junior colleges, and (at least some) for-profit colleges. --Ginkgo100talk · contribs · e@ 19:58, 2 August 2006 (UTC)[reply]
ADHESIVES
WHAT IS THE BEST ADHESIVE TO BE USED BETWEEN RUBBER AND POLYURETHANE, TO PREVENT PRESSURIZED WATER TO COME BETWEEN. WALEED KHAMIS
Please don't shout. DirkvdM 12:27, 1 August 2006 (UTC)[reply]
You want something like an acrylic resin that will turn into a hard polymer in the presence of water. Luckily, that is what Super Glue is. How stiff do you want it to be? Super Glue gets very hard, so the rubber won't be flexible. (Oh - and don't shout!) --Kainaw(talk) 14:54, 1 August 2006 (UTC)[reply]
Communication equipment
I'm doing research on Euipment used in Communication.please help!!--198.54.202.146 08:54, 1 August 2006 (UTC)Sizwe—[reply]
What kind of communication?--Shantavira 18:20, 1 August 2006 (UTC)[reply]
Is this a communication breakdown? Try to communicate your problem to us. DirkvdM 19:30, 1 August 2006 (UTC)[reply]
I agree. They needed to be more specific. --Proficient 20:36, 5 August 2006 (UTC)[reply]
Overlapping of orbitals
Whether S-S overlapping takes place only in the formation of Hydrogen molecule? Are there any examples for such type of molecules in which S-S overlap takes place? —The preceding unsigned comment was added by Vamsi mahathian (talk • contribs) .
I assume by "hydrogen molecule" you mean H2, so there's also H3+. Also consider the alkali metal hydrides. DMacks 16:29, 1 August 2006 (UTC)[reply]
Starching a Battledress?
Does anybody know why on the label of US made True-Spec BDU trousers it is written that you should not starch them? I have heard a military urban myth that starching your battledress makes it easier to see you using night-vision equipment. Can anybody deny or confirm this claim? Thank you for your time. Mieciu K 13:46, 1 August 2006 (UTC)[reply]
Standard military issue night-vision equipment works in either of two ways
By taking in the low amount of photons and magnifying the light so you can see on a little screen
Infrared radiation intensity is mapped, with different colors denoting different temperatures.
I don't know what the starch is that you use for washing is made of (perhaps starch?). If it is starch, I would think that the infrared radiation nor the visible light intensity would be had a more than negligible effect on.
Unfortunatly the label on the bottle of liquid (laundry?) starch dosen't specify what is the content of the starch that I have used, but I presume it was vegetable starch. Mieciu K 14:21, 1 August 2006 (UTC)[reply]
My experience with night-vision in the Marines is that a moonlight scope (which amplifies the visible light available) gets a bit of a reflection off smooth surfaces. If you overly starched your uniform, it is possible to get a reflection off the smooth surface. But, that is not likely. Infrared, on the other hand, did pick up on guys in newly starched uniforms better then those with unstarched ones. At the time, it was DI's and recruits. The DI's have heavily starched uniforms. I could see them much better than the recruits who were in wrinkled and dirty uniforms. Just to throw a wrench into the works - this was with the old uniforms. The Marines use a different material and pattern now. --Kainaw(talk) 14:47, 1 August 2006 (UTC)[reply]
Doesn't starch show up fairly vividly under ultraviolet light? Perhaps the idea is to make sure you don't stand out in a nightclub. --LarryMac 19:07, 1 August 2006 (UTC)[reply]
Yeah, that's what I thought, it might be a mixup with the reflection by blacklights. But that's caused by optical brighteners in laundry detergent residues. DirkvdM 20:11, 1 August 2006 (UTC)[reply]
Of course, it's also a bad idea to starch battle clothes for other reasons; stiff clothing is more likely to make noise, giving away your position, and cause abrasions, which may then become infected. Quite a stupid way to be injured on the battle field, isn't it ? StuRat 02:10, 2 August 2006 (UTC)[reply]
Are there clever ways to get injured? DirkvdM 07:14, 2 August 2006 (UTC)[reply]
No, but there are ways to get injured thru no fault of your own. StuRat 05:23, 3 August 2006 (UTC)[reply]
i was told in the NZ Army the fabric has IR absorbing dye in it. maybe the starch displaces or otherwise interferes with this? Xcomradex 08:30, 2 August 2006 (UTC)[reply]
I wonder if starch might have a negative effect on the marginal CBW resistance of the uniform?
Make Your Own Starch
Can you make your own clothing starch from the stuff at the surface of a pan of boiling potatoes? --130.161.135.31 14:38, 1 August 2006 (UTC)[reply]
Yes, that is how starch used to be made. However, I believe potato starch turns black as it oxidizes. So, you will want to experiment with the starch from other vegetables. --Kainaw(talk) 14:50, 1 August 2006 (UTC)[reply]
Try drying the goop from atop a pot of boiling rice. I vaguely remember doing this in elementary school to make starch. Nrets 15:32, 1 August 2006 (UTC)[reply]
Just Google "make your own starch" (use quote marks), e.g. "You can make your own starch by mixing 2 teaspoons of cornstarch with 1 litre of water." Other hits do include potato receipes.--Shantavira 18:23, 1 August 2006 (UTC)[reply]
Wow, you can make starch with starch? DirkvdM 07:16, 2 August 2006 (UTC)[reply]
It seems so. o.o--Proficient 20:37, 5 August 2006 (UTC)[reply]
Hub Gears
My bike has hub gears but I have to stop pedalling in order to change gear - is this a common feature of all hub gears or are mind just dodgy? Would I damage the bike if I changed the gear but carried on pedalling forward? And why is the hub physically unable to change gear unless I stop pedalling? --130.161.135.31 14:35, 1 August 2006 (UTC)[reply]
You should only have to stop pedalling for a split second (not at all if you're lucky). Yes, it is perfectly normal.
Have you looked up Sturmey-Archer? With such gears it is normal to stop pedalling while changing. At traffic lights, you might even have to back-pedal in order to change gear before setting off.--G N Frykman 17:12, 1 August 2006 (UTC)[reply]
If you just slow the pedals down a bit you should be able to change gear without actually stopping the "flow". Even with the other type of gears (which I can never spell) it's not a good idea to apply much force to the pedals while you change gear as this puts unnecessary strain on the mechanism.--Shantavira 18:27, 1 August 2006 (UTC)[reply]
I love hub gears and hate derailler (sp?) ones. I would be interested to know if there is now another company making hub gears since Sturmley Archer went out of business, as you cannot buy new hub geared bikes in the UK (except for a very heavy dutch town bike I think). The only hub geared bikes here are very very old ones. --81.104.12.138 20:50, 1 August 2006 (UTC)[reply]
Back-pedalling to change gears before traffic lights? I haven't used a gear bike in years, but I don't remember having to do that. Then again, maybe I anticipated the lights and changed gear before coming to a standstill. However, the hub gear article says "The other main advantage is that the gear can be changed when the bike is stationary, which makes them suitable for riding in city traffic with lots of stops and starts." DirkvdM 07:50, 2 August 2006 (UTC)[reply]
A geared bike is like a manual transmission car. On a car to change gears you use the clutch to disengage the engine from the transmission and then change which gears are engaged. On a bike, since the pedals only work one way (forward) and freewheel the other direction, you can effectively disengage the gears from the rear wheel by pedaling slower than the gears are turning. This allows you to switch without placing major stress on various components (as would be the case if you tried to slam a car in gear without using the clutch). Since derailleur type depend on the chain to ride itself to a new sprocket it needs be moving a little.72.1.70.58 13:14, 8 August 2006 (UTC)[reply]
Homework Questions
Q1) You are running a fermentation using anaerobic bacterium 'Megasphaera elsdenii' for the production of hexanoic acid using glucose as a carbon source.
(a) Assuming the hexanoic acid is a growth-associated product, draw a sketch graph of the relative concentrations of glucose, hexanoic acid and biomass with time for a batch culture. Explain what is happening at each stage of the fermentation.
(b) What calculations would you use to determine the efficiency of this fermentation in regard to the conversion of substrate to product, and the speed of production of the product?
(c) You need to increase the efficience and speed of the production of hexanoic acid. What environmental factors would you consider changing to achieve this?
i'm guessing that the answer for this is temperature and possibly pH
Q2) You have been given the task of removing the particulates from a fermentation broth, prior to extraction of the product from the liquid.
(a) i) Describe the structure and principle of operation of one type of filter you could use at production scale.
(ii) If you found that you were unable to achieve a suitable filteration rate, what other methods of particulate separation would you test?
(b) Describe one method for the drying of fermentation products, and state whether it is suitable for a heat-labile product or not.
–--81.154.224.133 15:04, 1 August 2006 (UTC)[reply]
Since you failed to see the big link for posting a question at the top of this page, you probably missed the note telling you to do your own homework. --Kainaw(talk) 15:36, 1 August 2006 (UTC)[reply]
Try reading the relevant articles, then come back here if you have an actual question, in your own words, about something you don't understand.--Shantavira 18:31, 1 August 2006 (UTC)[reply]
Black hole A partial balck body
As far as i have read ,it says that a perfect black body is somthing that can absorb as well as EMIT every possible radiation?????
in that case why is black hole not a partial black body?????????--59.178.2.243 15:14, 1 August 2006 (UTC)Harshita Gupta[reply]
Did you read black body and black hole. Perhaps you want to create a new article (and a whole new area of science) for partial black body. Hey, my body absorbs some radiation. Am I a partial black hole? --Kainaw(talk) 15:43, 1 August 2006 (UTC)[reply]
I have never encountered this term "partial black body". I take it to mean anything that isn't a perfect blackbody or a perfect mirror! In theory a blackbody can emit radiation of any frequency. The frequency of radiation emitted depends on the temperature of the blackbody (there is a nice graph of this in the black body article. As the temperature of a black hole is determined by the black body radiation temperature of the radiation that comes from it, it is possible to determine that the temperature of any observable black holes (as opposed to theorised sub-atomic ones) would be extremely close to absolute zero (~.00000001-.00000000000000000001K). This is why they don't emit every possible radiation.
Ummmm.... no. See the black hole article, the temperature of black holes is roughly 2.73 K, the same as the background temperature of space. Dan 15:02, 10 August 2006 (UTC)[reply]
Chronic wounds and maggot therapy
Good day,
I wish to know:
1. what are the sickness/dieases/injures would cause chronic wounds / necrotic(dead) tissue?
2. what are the sickness/dieases/injures would cause chronic wounds / necrotic(dead) tissue, but not recommend to apply Maggot Dbridement Therapy(MDT) treatment?
3. Are there any reports stated that MDT treatment fail to deliver successsful wounds healing？
4。 Are there any reports stated that MDT treatment tansforms chronic wounds worse?
Thank you very much.
Please take a short amount of time to familiarize yourself with the instructions at the top of the page. We're pleased to help out with most questions, but I'm afraid that we have to ask you to Do your own homework. If you need help with a specific part or concept of your homework, feel free to ask, but please do not post entire homework questions and expect us to give you the answers. TenOfAllTrades(talk) 16:16, 1 August 2006 (UTC)[reply]
is it true that the elephant population has tripled in the last month?--Nulity 16:19, 1 August 2006 (UTC)[reply]
Now that you mention it, I guess it did. We had zero elephants in Charleston before last month. Now, there are three times as many elephants in Charleston. --Kainaw(talk) 16:26, 1 August 2006 (UTC)[reply]
Lets see.... The elephant gestation period is about 22 months. Lets assume about 50% of the elephant population is female. Even if every female was pregnant at once and gave birth in the last month (and assuming there was no elephant deaths) then the population would simply have increased by a factor of 0.5. For the population to have tripled, every female would have had to have had quadruplets in the last month. According to this source [2] "Twins are very rare in elephants" and the ones in captivity in Bangkok "may have been unique". Therefore the chances that there has ever been elephant quadruplets seems highly unlikely. Given this, the answer to your question should be obvious. Rockpocket 17:44, 1 August 2006 (UTC)[reply]
For those who don't get it, last night Stephen Colbert did a segment on Wikipedia for The Colbert Report. He urged viewers to rewrite truth by editing a few Wikipedia pages, and Elephant was one of them. Melchoir 19:30, 1 August 2006 (UTC)[reply]
The media are calling for mass vandalism on Wikipedia? Are they getting scared? Afraid of the competition? (in which case they should have picked Wikinews, but let's not give them any ideas). Maybe we need an article on information terrorism. DirkvdM 08:00, 2 August 2006 (UTC)[reply]
Well, Colbert -- or at least his character on TV -- is a great believer in the democratic relativity of truth. He thinks that if something is repeated enough, it becomes true, and that Wikipedia is an ideal tool for exploiting this phenomenon. Of course, this is just the show's way of lampooning conservative American thinking. On the "The Word" segment, while he was talking about Wikipedia, at one point the caption read "The future will not be verified"; I take this as evidence that he's actually aware of WP:V in real life. Melchoir 18:25, 2 August 2006 (UTC)[reply]
Only seven edits? I thought Stephen Colbert's viewer figures were better than that. :-) DJ Clayworth 18:04, 2 August 2006 (UTC)[reply]
How to invest in different stock exchanges?
Can I use an online brokerage to invest in any stock exchange? I'm thinking specifically of the Toronto Stock Exchange (I am an American). How to specify the symbols used on each, since a three-letter symbol in one exchange might stand for a different company in another?
Thanks.
They'll have .TO pasted on to them. --jpgordon∇∆∇∆ 18:14, 1 August 2006 (UTC)[reply]
Corn earlage
What is corn earlage, and what is the difference between corn earlage and silage? --AR
Silage is a functional definition for something you feed to animals while stover is just described as everything but the grain. As for earlage...
Solubility vs. Temperature Curves for Glycine-Sodium Sulfate Solutions
How do I find Solubility vs. Temperature Curves for different concentrations of Glycine and Sodium Sulfate Solutions? Glycine is the simplest amino acid (NH2CH2COOH) and Sodium Sulfate is an inorganic salt, often called saltcake (Na2SO4). Thanks for your help.
M.D.S.—
start with the CRC Handbook of Chemistry and Physics Xcomradex 08:22, 2 August 2006 (UTC)[reply]
Why gender body size difference in humans?
I'd like to make clear from the start that I have a lot of respect for women, that I'm a very gentle person, and that I abhor violence or aggression. To continue -
The average size of human males is greater than that of human females. I am not sure to what extent that this is true of other primate or mammalian species.
Some time ago I heard on the radio someone saying that this size difference evolved due to males fighting among themselves for female mates. I think the speaker was taking care to be P.C., as wouldnt it be more likely to be due to larger males raping less powerful smaller females, and thus evolution would select for both larger males and smaller females?
And, on a more minor point, perhaps human IQ evolved because of the machiavellian tactics required to get a mate and avoid deadly violence in a primitive society that was brutish and violent and without any ideas of gentlemanly behaviour?
Humans are social animals, meaning not that they (necessarily) behave more socially, but that they live in groups. Any aggression within the group would make it less stable and more vulnerable, giving offspring a smaller chance of surviving. Humans also form couples. A female without a mate might get less meat, which would stint the child's growth and such, giving it an evolutionary disadvantage.
However, if, like you do, you view humans as individuals fending for themselves, bigger and stronger women would have a better chance of protecting themselves and their offspring, both against rapists and other threats. I'd say that the fact that females are smaller supports the notion that they are social animals. Is this true for other animals as well? DirkvdM 08:21, 2 August 2006 (UTC)[reply]
Males are larger because they compete with other males. Peter Grey 00:56, 5 August 2006 (UTC)[reply]
People tend to leave out the possibility that we may have been created. Intelegent design may help you to understand not only our physical atributes but also our social structure.ĆÁĎ
Designs in nature don't show much intelligence, only brute-force trial and error. Peter Grey 19:20, 7 August 2006 (UTC)[reply]
Cashew
Is a cashew a legume or a nut?
Neither; it's a drupe. See Cashew for more. --Allen 21:16, 1 August 2006 (UTC)[reply]
Hey, who are you calling a drupe? Ca'shew see the notice about no personal attacks? ;-) --Fastfission 04:32, 2 August 2006 (UTC)[reply]
Quite a few cashew questions recently. How long until they have overtaken gulls? DirkvdM 08:24, 2 August 2006 (UTC)[reply]
Only a very slow gull could be overtaken by a cashew. Gandalf61 13:27, 2 August 2006 (UTC)[reply]
That would depend on who is throwing the cashew... - 87.209.70.231 20:39, 6 August 2006 (UTC)[reply]
He can if he's masturbating. – ClockworkSoul 22:04, 2 August 2006 (UTC)[reply]
I have some questions about MRI scans (specifically fMRI) that I hope you can answer.
How loud is it inside an MRI machine (i.e. how many decibels)? Are the earplugs they give you any good at filtering out the noise?
Do they use any radio frequency waves? Is the amount of these waves large enough to be harmful?
Is the magnetic field harmful to the human brain? What are the long-term effects?
Are there any other potentially dangerous/harmful things about MRIs?
Thank you!--Anakata 00:34, 2 August 2006 (UTC)[reply]
I have no technical info, but I can tell you it's not so bad with the earplugs. And I'm sure they're perfectly safe. Melchoir 01:32, 2 August 2006 (UTC)[reply]
When I went they gave me head phones to listen to any radio station I wanted. I couldn't really hear any noises, and I could also hear the mri tech through the head phones asking me how I was doing and how long each scan was going to take.
Another question: Is the noise potentially harmful to my hearing?--Anakata 02:42, 2 August 2006 (UTC)[reply]
Now that I don't know about. I seem to recall that the reason for the earplugs was more that the sound is annoyingly loud rather than dangerously loud... but my memory is terrible. Anyone else? Melchoir 02:59, 2 August 2006 (UTC)[reply]
The only thing potentially dangerous about MRI scanners are freak accidents relating to the magnets—i.e. if something metallic is brought into too close of a range with an active scanner it can be pulled into the machine (when that "something" is a gun or an oxygen tank, it can easily be fatal), or if the patient has some metal in their body they don't know about (which is why people who have worked in autoshops or other places where you can get filings embedded into you without your knowledge are generally prohibited from being in MRIs). Other than that there is no known damage to be suffered from MRI scanners, to my knowledge. It's a danger worth taking seriously but it is a side effect of the way the scanner works, not a direct product of being scanned. Statistically it is very safe (I have had it done to me personally, and there was no problem at all. In the end I got a neat picture of my brain out of it by asking the people to send me the raw datafiles). --Fastfission 03:14, 2 August 2006 (UTC)[reply]
So one shouldn't go into an MRI scanner with a gun strapped to one's head. The things I learn on Wikipedia. DirkvdM 08:34, 2 August 2006 (UTC)[reply]
The gun incident happened because there was a police officer in the room, just a bit too close to the magnet, if I recall... --Fastfission 12:41, 2 August 2006 (UTC)[reply]
As stated in the article, it does indeed use RF energy. If you go to the NMRI article, and scroll down to the safety section, you can read all about the health concerns. --198.125.178.207 13:35, 2 August 2006 (UTC)[reply]
MRI's can generate sound pressure levels up to about 130 dB during certain scans. There is the potential for hearing loss at these levels, so earplugs (or muffs) are necessary to protect the patient / subject's hearing.
MRI's do use RF energy. The energy can create focal heating, particularly on electrically conductive materials that can act as antennae. Make sure that there is space and / or padding between your body and the walls of the MRI and any wires used to monitor your vital signs during the exam. The RF energy is believed to be of no health concern.
Magnetic energy (and RF energy, for that matter) is non-ionizing. This means that the cancer risks that are present in conventional X-ray imaging are not present in MRI imaging. The magnetic fields used in MRI, even though they are dramatically more powerful than most people would otherwise come into contact with, are not shown to have any adverse biological effects. The magnetic fields can interfere with implants and devices, so it's critical to provide your full medical history to the MRI provider.
The primary risk in MRI is the magnetic attraction of ferromagnetic materials. These sorts of accidents make up the majority of injuries in the MRI environment. Focal heating is second. These accidents are largely avoidable and, despite recent dramatic increases in MRI accidents, are fortunately not terribly common.Tgilk (talk) 16:17, 14 December 2008 (UTC)[reply]
Speed of the Space Shuttle
Hi,
Does anyone know what the speed of the space shuttle is from T-0 to SRB separation? I was watching the launch the other week and just got around to asking the question. Deltacom1515 02:03, 2 August 2006 (UTC)[reply]
Um, do you mean how long it takes, or what's the average speed over that interval, or the final speed...? Melchoir 03:01, 2 August 2006 (UTC)[reply]
Sorry 'bout that. I meant the acceleration of the Shuttle from 0 to SRB separation and the velocity is is traveling when it clears the tower. Deltacom1515 20:51, 2 August 2006 (UTC)[reply]
What is the difference between electrostatic and electromagnetic levitation and another question
What is the difference between electrostatic and electromagnetic levitation? i have heard that electrostatic levitation can also lift non-conductive materials. is this true? secondly could electromagnetic waves or electrostatic waves be used to push an object instead of levitate it? [ by directing the force at the side rather than the bottom for example]
thanks
curious marve
The diff is that magnetic repulsion lifts in the one case and electrical repulsion in the other. Yes, only certain materials, like metal alloys containing iron, may be magnetized, while all materials can hold an electrical charge. And yes, either force could be used to fire a projectile, see coil gun, rail gun, linear accelerator, and cyclotron. StuRat 03:59, 2 August 2006 (UTC)[reply]
A copper bowl can be made to levitate by coils placed below it which produce an ac magnetic field. May be related to work by Faraday with a copper disc in a magnetic field, or by Tesla with a copper egg in a rotating magnetic field. I'm told the bwol heats up so the demo is usually for a few seconds. I've seen a demo with a magnet and liquid nitrogen in which the magnet levitates, or maybe a condictor levitates over the magnet. Maglev is used for some high speed trains. A charged object should levitate above a plane conductor with the same charge, if the magnetic repulsion is greater than the object's weight. It should similarly be lifted by a plane or point of the same charge above it, but this would tend to be unstable if the charges were constant. Edison 23:22, 3 August 2006 (UTC)[reply]
Thank you all, but can i crarify this please. So any material can be moved or levitated by elecrostatic fields, even stone,plastic or wood?
Curiousmarve
U.V- Effect
Hello! Very recently, one of my friends was working in the Laminar-chamber , he was busy streaking... and accidentally, the UV was switched on. Engaged in his work, he didn't realise it for about a minute , ie. he withdrew his hands from the laminar after about a min. Later, he consulted a general physician, and a radiologist too. All the tests indicated that he had no internal or external damage whatsoever. I want to know was he too lucky? Or may be the intensity of UV was too low? Is a minute's duration enough, to cause damage to human tissues(keeping in mind, the UV used here) ? --Pupunwiki 02:52, 2 August 2006 (UTC)[reply]
What's a "Laminar-chamber"? You don't say what the wavelength and intensity were, so I'm thinking the dose was so low it was harmless. —Keenan Pepper 03:58, 2 August 2006 (UTC)[reply]
A laminar flow cabinet is a type of biology safety cabinet for culture and/or for filtering potentially biohazards. Often they have UV sources for sterilisation purposes. Obviously UV exposure is not ideal, but i have seen quite a few scientists expose themselves to UV (usually in a electrophoresis gel transilluminator, which one might imagine to have higher UV intensity) for many minutes. Generally they suffer the equivalent of a bad sunburn on the exposed area. Of course, the long term effect of such an exposure on the skin and eyes is unknown, but there is no reason it should do any more damage than spending too long at the beach one summers day.
If your friend didn't even have superficial skin burns, then i expect the dose was low enough, the intensity was low enough and/or his skin tone was dark enough for no serious damage to be done. Or more likely a combination of all three. Either way, if the doctors have given him the all clear, it is most likely not something to worry about. Rockpocket 04:38, 2 August 2006 (UTC)[reply]
Pretty much what I was going to say. Laminar flow cabinets use UVC (the shortest wavelength of UV and the most harmful) to kill germs, but one minute isn't long enough to do significant damage (unless you stare at it and it hurts your eyes). The reason for all the warnings is that if you make a habit of working with the UV on, the damage will build up over time and you'll get skin cancer. —Keenan Pepper 04:46, 2 August 2006 (UTC)[reply]
I have to say, I'm a bit skeptical. When the UV is switched on in one of these hoods, there is no doubt that it has been turned on. In every model that I've ever seen, the lighting switches are configured as "on/off/UV", where "on" is working lighting, "off" is no lighting, and UV is a brilliant radiant purple or blue. I can't imagine that anybody would be so engrossed in their work that they wouldn't notice such an abrupt change in lighting, or somebody making such a mistake in the first place. That being said, such exposure for less than a minute is unlikely to have any problems. – ClockworkSoul 16:35, 2 August 2006 (UTC)[reply]
Unknown scientist
I was linking more names in the Timeline of luminiferous aether, but I could not find who
Tomascheck was. ("1924 - ... uses stars for his interferometer light source, getting the null result.") Anyone know his full name? Rmhermen 03:53, 2 August 2006 (UTC)[reply]
At current erosion rates, how long would it take for the present continents to erode to sea level if there were not any new land mass created from volcanic activity or any other process? The reason for this question is that I heard it said that it would take only 14 million years. If this is true, then how are there any fossils found dating back any further?
Just 14 million years is indeed an impressively short time span. And in the 80's erosion was considered the biggest threat to human food production (that place is now probably taken by climate change), although that is in part due to the wrong ploughing techniques.
Anyway, erosion is not just the removal of material - the material also gets deposited elsewehere. Also, it doesn't take all land above sea level to erode to below the present sea level. As more material gets deposited into the seas, sea levels will rise, speeding up the process. So the mountain tops will erode away, depositing their material on the lower ground, where most life resides. In time, this will get flooded, life will move further up, get covered in turn, etc, until it is all gone. And buried. In real life, apart from volcanic activity, there's also the rising (and falling) of landmasses. So many bones buried beneath the sea will eventually 'surface' (literally). Some have even made it to the highest peaks (sea shells on Mount Everest).
In short, erosion doesn't expose fossils. It buries them. DirkvdM 09:26, 2 August 2006 (UTC)[reply]
You ask " If this is true, then how are there any fossils found dating back any further?" That's an easy one, because there is volcanic activity and other processes. Personally, though, I doubt it can be true. Would Mount Everest erode to nothing in 14 million years? Let's see now, it is 8,850 m high. To go away in 14 million years it would have to erode 8850 / 14000000 m per year, which is about 0.6 mm per year. That's quite a lot for solid rock. Notinasnaid 09:36, 2 August 2006 (UTC)[reply]
That rate sounds believable to me. The missing element is that the mountains are being pushed up as fast or faster than they are being worn down, however. StuRat 06:31, 3 August 2006 (UTC)[reply]
This seems to be a creationist myth started in 1972, presented here along with such gems as the saber-toothed duck. It is debunked here. -- Avenue 09:50, 2 August 2006 (UTC)[reply]
Do fossils get buried by volcanic activity? Of course some will, but are they preserved for us to find? Sediments (from erosion) sound more probable to me. DirkvdM 10:36, 3 August 2006 (UTC)[reply]
Ok, I visited the suggested web pages. Thank you for the advise. However the web page said that 200 million years ago the mouth of the Miss. was as far back as Illinoise. My question has changed direction. How is it that Florida formed? If you receed all rivers back proportionately the same amount Florida becomes disconnected. Florida also has the St. John river, which is pretty large, that would split it. Florida seems to be to flat to be formed from plate uplift or volcanic activity. both of these actions make me think of mountains, Florida does not have any. I hope ya'll like to answer questions because I have a lot. Thank you for your patience.ĆÁḌ
I believe most of Florida, the Gulf coast, and central US were underwater at that time. I'm not sure if the water level was higher or the land lower or some combo of the two. Do we have a map of this in Wikipedia ? StuRat 06:17, 5 August 2006 (UTC)[reply]
I geus nobody has a good answer?
Sure we do. Your assumption that erosion happens by itself is wrong. At the same time some surfaces are being eroded, many others are being buried in sediment. Surfaces so buried, and any fossils they contain, are completely protected from erosion. StuRat 06:30, 7 August 2006 (UTC)[reply]
MRI accident on House
In an episode of House ("Euphoria" part 1), Dr. House wants to find out whether it's safe to do an MRI on a patient with ferromagnetic bullet fragments in his head, so he goes down to the morgue, shoots a corpse with the same kind of gun, and puts the corpse in the MRI. The bullet fragments jump out of the corpse and destroy the MRI machine.
Two questions:
How large does a ferromagnetic object have to be to cause harm to the MRI machine or the patient? I mean, many breakfast cereals contain "reduced iron" which is basically iron filings. Is it safe to undergo MRI after eating a lot of Cheerios?
Why did Dr. House think it would work? He's a brilliant doctor, he speaks many languages and he knows random facts about everything... why is he so clueless about basic physics? Did the show's writers just make a mistake? —Keenan Pepper 04:25, 2 August 2006 (UTC)[reply]
Because he plays by his own rules. (I've never seen the show.) Melchoir 04:42, 2 August 2006 (UTC)[reply]
I would suggest the primary explanation is that it makes better tv to have him destroy a MRI after shooting a corpse to demonstrate the point, than explain the same thing in dry scientific language. And anyway, House isn't really that smart. Rockpocket 04:49, 2 August 2006 (UTC)[reply]
What about ear/eyebrow rings? I have a few. I wonder if they'd be torn from my flesh and fly around like shrapnel inside the machine? --Kurt Shaped Box 08:36, 2 August 2006 (UTC)[reply]
Yep, if you google 'mri accidents' you'll see there was a case where someones hairpin was dragged inside their head... Xcomradex 10:07, 2 August 2006 (UTC)[reply]
If you walk by an MRI machine with metal earrings you can feel them start to tug (or so said my girlfriend at the time), much less a bullet in a gun. My guess is that it made more sense for the writers to have eclectic Dr. House do something like that than it did to have him say, "Well, obviously the better way to test if a bullet is ferromagnetic (if we need to test this at all) is to, I don't know, just put it near a smaller magnet, or maybe even just very slowly introduce it into contact with the MRI machine?" Anyway... when you sign up for an MRI they make you answer a million questions about ways you might have accidentally got metal filing into your body (people who have worked in machine shops for a living are not allowed to take them because of the chance they might have a metal sliver in them somewhere that they don't know about), so I imagine it doesn't have to be too big of a piece. I am sure the iron content of your blood is not a problem though, X-Men 2 not withstanding. --Fastfission 12:47, 2 August 2006 (UTC)[reply]
I had to get my permanent retainer temporarily removed to have an MRI awhile ago, but oddly enough, the reason they gave is that it would ruin the image(distort the field around my head), not that it might rip my teeth out. Black Carrot 22:03, 2 August 2006 (UTC)[reply]
The retainer may have been made out of a metal that is not ferromagnetic, which would not pull your teeth out but could cause distortion. 48v 18:37, 4 August 2006 (UTC)[reply]
Based on my experience, people who have worked in machine shops are not prevented from having an MRI scan performed on them. Depending on the risk exposure, they may be x-rayed a few times to see if any fragments of metal are actually still in them (in the eyeball, in my case); and if none are found the MRI scan will proceed. Anecdotally, I heard that one can hold something metal, like, say, a spoon up to the wall outside an MRI suite and it will be magnetically stuck to the wall. Depends on the building, of course, and how close the MRI scanner is to a wall...
Didn't that whole episode turn out to be a hallucination? House might be allowed a little rhythm under those circumstances.... --Trovatore 04:02, 3 August 2006 (UTC)[reply]
No, that was a different episode. =P —Keenan Pepper 19:52, 4 August 2006 (UTC)[reply]
In answer to the House MRI question...
How large does a ferromagnetic object need to be? A patient was blinded by a tiny sliver of ferromagnetic material in the eye some years back. An aneurysm clip of a couple centimeters twisted and tore, killing a patient, and a nail clipper put out an eye of yet another patient. So, depending on where it is, a very small mass of material can be very dangerous to a patient. Damage to the MRI machine typically requires something a bit more massive (i.e. chairs, gurneys, gas cylinders, etc...). However, MRI service personnel are sometimes called to take care of a machine that isn't producing quality images, a problem that is often triggered by a collection of small ferromagnetic materials (barrettes, jewelry, paperclips, etc...) that wind up getting collected inside the MRI machine.
Would his corpse experiment work? NO, it wouldn't, at least not the way it was shown on TV. There are two forces that act on ferromagnetic materials in the presence of a magnetic field. One is torque where the object tries to line-up with the magnetic polarity of the field. The other is the translational (or 'missile') effect which draws ferromagnetic materials to the strongest part of the MRI field (in the center, where the patient lies). The torque forces keep getting larger and larger as you move to the center of the MRI. The 'missile' effect forces, however, are greatest near the entrance to the 'mouth' of the MRI and actually drop to zero where the patient would be for imaging.
So, when House put the corpse into the MRI and 'turned it on' and the bullet came flying out, there are a number of things wrong. First, there is no turning the MRI's magnetic field on and off for most systems. So, the attractive 'missile' effect would have been present and increasing as they brought the corpse towards the MRI, but would have dropped to zero once they had the corpse's head in the middle of the MRI. The torque, which would have wanted the bullet to align with the polar orientation of the MRI's magnetic field, would have grown and grown, but having the bullet simply twist wouldn't have been nearly as good 'TV drama' as having it blow through the skull and 'shoot' the MRI machine.
Now the recent ER episode of the patient being pinned to the MRI by the gurney that they were brought into the room on... that's another story... see
http://mrimetaldetector.com/blog/?p=217
We know that EM waves dont comprise of sound.But if we were to hold the blades of a fan and turn it on,then from where do we here that noise?
The noise from a running fan is caused simply by vibration in the motor and the fan blades. -- AJR | Talk 12:30, 2 August 2006 (UTC)[reply]
How about when I put 5 amps through a nail-and-copper-coil solenoid I made in high school? That thing made some noise! — [Mac Davis] (talk)
If you stop a fan from going round, then the coils in the motor will be pulling on each other, or on the permanent magnets if there are any, with a force that's proportional to the current. Assuming the fan is mains-powered, then that current is alternating at 50 or 60 hertz (cycles per second). This makes the force pulsate at 100 or 120 hertz (because each cycle of current has two peaks, one positive and one negative). The pulsating force makes a buzzing noise because the parts of the fan are periodically distorted by the force. The same thing applies to the solenoid. The distortion is partly due to electrostrictionmagnetostriction and partly just to mechanical forces. --Heron 21:02, 2 August 2006 (UTC)[reply]
light speed
What if light were travelling in a striaght tunnel,and the tunnel happened to be the radii of a fast moving object.Since the end of the rod would be moving faster,would not that light be moving faster than light?
I'm not sure I really understand the question; but the answer is no.
Light moving faster than light, so something moving faster than itself? I suppose you mean a specific beam of light moving faster than 'the speed of light'. In other words, you're asking why there is such a thing as 'the speed of light', ie why light has a fixed speed. I could try an answer, but I'll leave that to someone more knowledgeable. I just tried to help you make your question clearer. DirkvdM 09:47, 2 August 2006 (UTC)[reply]
I'm not sure what the question means either, but you might find the article on frame of reference interesting, or special relativity, which is Einstein's answer to the dilemma which I think you are addressing. --198.125.178.207 15:31, 2 August 2006 (UTC)[reply]
I'm going to guess that you are imagining a long tube being spun round and then light shone down the tube, and then you are imagining that the light would move at the sum of it's own velocity and the velocity of the tube it is shining down. The answer is still no, because a) relativistic effects would ensure that the light always moved at constant speed and b) if the tube were spinning at any noticable speed the light would hit the walls, not follow the changing path of the tube. Light doesn't change direction to follow the walls it is 'contained' in. DJ Clayworth 17:43, 2 August 2006 (UTC)[reply]
There are several different recorded light speeds. I just heard on NPR radio that scientist claim to have stopped light and held it in place for a few seconds.
The speed of light depends on the medium it's travelling in. Air reduces it by a percentage point or two, diamond by about 60%, and certain exotic materials by a great amount indeed. This doesn't affect the fact that the speed of light in vacuum is a constant, and the highest possible speed. --Pyroclastic 14:03, 10 August 2006 (UTC)[reply]
Quanta UNIVERSE
We know that the theory of everything comprises strings.So does that not make it possible only for integral values of particles or strings to exist,so therby only intergral values of force and other quantity to be transmitted and recieved?
Well, we don't 'know' that. String theory is just a theory (and one might argue it is not even that because it cannot be tested - it is not falsifiable). DirkvdM 09:51, 2 August 2006 (UTC)[reply]
Please don't say "just a theory." However string theory fulfills only half of the scientific method. The theoretical part, not the experimental. — [Mac Davis] (talk)
I will say whatever I please. :) You're right that something being 'just a theory' doesn't mean it doesn't have value (the general theory of relativity being one example). Everything starts off as a theory anyway. But my point was that you shouldnb't confuse theory with knowledge. Strictly speaking, we don't know anything and everything is theory. Which again boosts the status of theories, of course. DirkvdM 10:41, 3 August 2006 (UTC)[reply]
Electron
An charged particle under acceleration should emit radiation.Then why would not a charged particle undergoing acceleration around the nucleus of the atom or in the cyclotron emit radiation,as it is tracing a circular path and objects tracing a circular path undergo constant acceleration?
The image of electrons as orbiting nuclei in a similar way to planets orbiting stars is a simplification. See Quantum Mechanics.
Here is one explanation: [3]. Weregerbil 08:54, 2 August 2006 (UTC)[reply]
Regarding a cyclotron, it seems it does actually emit as you expect (see cyclotron radiation and synchrotron radiation), because those actually do have particles orbitting. DMacks 20:37, 2 August 2006 (UTC)[reply]
CD-DVD burn
why cant we use a blank dvd to burn on a cd burner and blank cd to burn on dvd burner?
The grooves are too close together on a blank DVD for the CD burner to understand. Notinasnaid 10:26, 2 August 2006 (UTC)[reply]
But you can use blank CDs to burn on a DVD burner in most DVD burners. It will use the capacity of the CD.--Wikicheng 13:44, 2 August 2006 (UTC)[reply]
Pneumatic brakes
whats the advantage of air brakes over their hydraulic counterparts. i see that heavy trucks and trains tend to prefer air brakes over hydraulic,why?why not have these air brakes on passenger cars if they are that effective?
An obvious answer is that passenger cars aren't quite as heavy as trucks. The other part of the answer would then be that hydraulic brakes are in some ways more expensive (the brakes themselves, their operation, maintenance, whatever). DirkvdM 09:57, 2 August 2006 (UTC)[reply]
There is no advantage - the two types of brakes do different jobs. Air brakes are used only as a failsafe backup system. In an emergency, the air is vented to the outside to apply the brakes. This is simple and reliable, but too cumbersome and not controllable enough for normal braking. Trucks, like cars, use hydraulic brakes for normal braking, because hydraulic brakes are quicker, smaller, easier to control and more powerful. --Heron 20:53, 2 August 2006 (UTC)[reply]
Many heavy vehicles do use pneumatic brakes for normal braking—haven't you ever heard them at a stop light? In order to stop a heavy vehicle quickly you need to exert much more force than for a passenger car. One could design a hydraulic system with enough mechanical advantage to provide this force from a foot pedal, but then you would have much less control over braking. Air brakes are controled by a valve which feeds air from a reservoir to the pistons—giving much more control over the range of forces which can be applied. Air brakes are also more tolerant of leaks and water in the system.
Pneumatic brakes are not used in passenger vechicles because the are not necessay, are more expensive and bulky, and require more maintenance.EricR 02:10, 3 August 2006 (UTC)[reply]
Well, what do you know, a subject I know next to nothing about and my answer was spot-on. Long live educated guesses. :) DirkvdM 10:45, 3 August 2006 (UTC)[reply]
In the event of a major catastrophe, that sent mankind back centuries or approached (near-)existinction levels, could the internet data (such as the information from wikipedia) theoretically be retrieved then at a much later date? (such as the case of the Rosetta Stone being "translated" in the 19th Century)
Also, could theoretically the internet be received or "read" by other distant civilizations? (as in the way that extraterrestial communication/signals are hoped for possibly through radio waves I think)
Thanks for info. ==Joel==
Something similar was asked before here at the ref desk. Apart from that, the rosetta stone wasn't translated, it was itself a translation, helping with other translations. And if humans were almost extinct, the information on the Internet would not survive (it needs electricity). So the info would have to be stored in a different way. DirkvdM 10:10, 2 August 2006 (UTC)[reply]
The information does not need active electricity in order to survive as just data on a million computers. There is a lot of worried discussion among computer scientists about how long current data storage mediums last — not too long. The Rosetta Stone, being carved in a rock, is much more durable than magnetic storage media, much less affected by the elements, much easier to use if part of it became damaged. Still, I imagine the sheer volume of data which goes into the internet means that quite a bit could be recovered even if nobody was tending to it for a few centuries. I imagine that many servers are in places that would be relatively protected from the elements (such as those buried deep within large facilities).
As for the second questions, the only way that the internet would be read by someone off of Earth is whether it is broadcast (like television or radio). I don't know enough about tramission protocols, but I do think that some internet connectivity is done via satellite? If that's true then those connections may be potentially interceptable, decrypted, etc., I suppose (I don't imagine WiFi signals to be strong enough to make it that far, but I know little about this sort of thing). Let's hope that the people with connections like that don't just use it to surf for porn. ;-) --Fastfission 12:59, 2 August 2006 (UTC)[reply]
I've read a description of a wished-for radio telescope talked of by a radio astronomer: You take a star as your lens and sit back where the stuff you're interested in is focused by the gravity. The radio astronomer described it as potentially able to hear a walkie talkie (hand held radio) being used on a planet 10 light years distant. The latancy would suck though.
In my opinion, if it were some space beings coming to Earth long after humans were gone, it wouldn't be by chance. They would be attracted by the radio and television waves shooting out into space. Surely, they would decipher it before arriving on Earth and will have prejudged humans based on what they've seen and heard - pretty much how humans prejudge other cultures based on mass media. Youth in Asia 15:01, 2 August 2006 (UTC)[reply]
The beauty of the Internet is that it is designed to work over just about anything - TCP/IP consists of many ayers and you just need to adjust the bottom layer (I think). And it does work over anything. I one route doesn't work, another one is used. So I suppose that everyone will at least once in a while receive some data that have gone through satellites. DirkvdM 10:50, 3 August 2006 (UTC)[reply]
Thanks to all above for the info., Joel
how do we know if its been tried?
hi my names ben, ive been thinking about this perpetual motion thing a bit, since i noticed what seems like a working example, i dont expect to hold the key, but im curious to see other failed attempts based on this illusion of free energy. is there a list i can go through?
because regardless of weather or not it does create free energy, i think it may still be useful.
i think we'll figure it out one day, we'll follow a trail that will lead us to the very beginning, and there we'll find the supernatural, proof of thats not hard to find, also seems someone have allready nailed it,i like the way joal thinks, out side the box,i consider the physical universe as we know it a box.theres alot more if if you know how to open your eyes. search psychic witnesses, and ufo evidence.
thanks heaps for any help
Beno
You want us to check if something you will not describe has been tried before? Thanks for the confidence, but we're not gods. :) DirkvdM 10:13, 2 August 2006 (UTC)[reply]
There's "a lot more" out there than "psychic witnesses" and "ufo evidence", indeed. But the latter two strike me as not very interesting, frankly: examples of a human willingness to believe, age-old desires to know that someone is in control, somewhere -- a hope that there is still mystery in the world. But there's much more mystery in the natural world than there are in dreams of the supernatural. How much more interesting the mantis shrimp is than the "greys" that the UFO nuts like to talk about! How much more bizarre the human mind is, with its strange wiring and odd sense of the world, than ramblings of New Age "psychics"! Oh, if only we could really appreciate how fascinating and bizarre the natural world is, we wouldn't have to take refuge in the relative banality of fantasies, which only reflect the limits of the human imagination! --Fastfission 13:06, 2 August 2006 (UTC)[reply]
Very well said. I'm keeping that. — [Mac Davis] (talk)
Truth is indeed, in many ways, stranger than fiction. Sadly, though, the curious appearance of a shrimp doesn't help me make things levitate. Black Carrot 21:51, 2 August 2006 (UTC)[reply]
I wouldn't view an apparently successful perpetual motion machine as proof of the supernatural, but rather as evidence of a natural, although currently unknown, form of energy. Radio wave energy, for example, was unknown for most of human existence StuRat 06:08, 3 August 2006 (UTC)[reply]
You can fill in pretty much what you like for 'radio wave energy' because most of what we know now was unknown for most of human existence. DirkvdM 18:52, 3 August 2006 (UTC)[reply]
Yep, that was just one among many possible examples. StuRat 20:57, 3 August 2006 (UTC)[reply]
When you talk about tings supernatural you are only talking about things observed that we can not yet understand. Things such as religion. There is ample amounts of imformation to support the thought of intelligent desighn. One day ,if man ever does find a way to understand these things in a way that would go further than religion, these things will be facts & not religion. Something that is truth from the begining is not less true simply because we do not understand. If nothing else, Science has taught us that. So, indeed there is an answer to prpetual motion and energy.ĆÁĎ
Consumption
I was looking for disseases/afflictios that greatly eat up/damage the inside of the body. Necrosis and consumption, but i'm looking for other, and perferabbly stronger examples.
Consumption doesn't eat up the body any more than many other diseases (see tuberculosis), though it was once thought so. The classic diseasse that eats up the inside of the body is cancer. For nasty and well known diseases try leprosy and ebola. Notinasnaid 11:38, 2 August 2006 (UTC)[reply]
As well as 'eating up' the inside, im looking for things that make them go black-like when you see those anti-smoking adds, and they show you those black lungs.
That doesn't 'eat up' the lungs either, nor is it a disease, and anyway, working in a coalmine (or living next to a highway) is much more effective in blackening your lungs. DirkvdM 10:53, 3 August 2006 (UTC)[reply]
Necrotizing fasciitis is a pretty good example for a disease that quickly "eats up" the flesh (hence the nickname of its cause, "flesh-eating bacteria"), but this isn't the inside of the body, its the deeper layers of skin and subcutaneous tissues (fascia). – ClockworkSoul 16:23, 2 August 2006 (UTC)[reply]
Hemotoxic venoms do, and Phosphorus certainly would, although I don't know if you could call it an affliction.--Anchoress 19:17, 2 August 2006 (UTC)[reply]
These are all very good, and thanks to all the contriubtors. What woudl be great though are things that are very astheticaly profound, like more with an urg factor.
Did you read the article on ebola? Hollywood has embraced it because it considers (perhaps wrongly) that it has more urg factor than any other condition in history. Notinasnaid 12:28, 3 August 2006 (UTC)[reply]
sexual thought freqency
Is there a real study on the freqency of sexual thoughts in men and women? All I find is contradictory and annecdotal.
I saw an article once (I forget where) about an interesting experiment which tackles (one element of) this question. They kitted out subjects with special spectacles which recorded where they were directing their attention. If I remember correctly, it was found that the average woman does look at the "interesting bits" of men, but proportionately less than men do for women.
I don't the experiment analysing gay men and women's behaviour.
Clearly, looking at bums is just one aspect of sexual thought, but it was a usefully revealing methodology, even if the specs themselves weren't all that revealing. --Dweller 15:04, 2 August 2006 (UTC)[reply]
So it's true then? Girls don't like boys; girls like cars and money? --Trovatore 20:30, 2 August 2006 (UTC)[reply]
Well I sure like boys, but I'd rather look at a car.--Anchoress 21:01, 2 August 2006 (UTC)[reply]
I've never understood the concept of "sexual thought frequency". To think about it repeatedly, wouldn't you actually have to stop thinking about sex at some point ? Who can do that ? :-) StuRat 04:07, 9 August 2006 (UTC)[reply]
Geologic time scale terminology: Paleo- vs Eo-
In the Archean eon, why does the Eoarchean era precede the Paleoarchean era, when in the Paleogene period (early Cenozoic) the Paleocene epoch precedes the Eocene epoch? (Yes, I realize that the Precambrian time divisions were only recently established and assigning names to them is somewhat arbitrary; but even so, why would the International Commission on Stratigraphy have chosen to go along with a usage of prefixes which is inconsistent with the already long-established Cenozoic sequence of epochs? Were they catering to previous publications, or lazy geologists, or what?) Lots of searching on this seemingly trivial point has revealed absolutely nothing, which makes it all the more annoying (to me, anyway). --DWIII 15:08, 2 August 2006 (UTC)[reply]
Megawatt_hour
How to compute the cumulative power output (in MWh) of a power plant generating 100MW?
100MW is the power. MWh is used to measure energy, not power. Youth in Asia 16:30, 2 August 2006 (UTC)[reply]
Sorry, I mean cumulative energy (at least for a day).
Just multiply. 24h * 100MW = 2400MWh. --Allen 16:57, 2 August 2006 (UTC)[reply]
What do you mean by 'at least for a day'? In case you're confused, the unit Wh is confusing and converting from power to energy is sort of 'the wrong way around'. One watt is one joule per second. So the Wh first divides by one unit of time (the second) and then multiplies by another (the hour). 100 MW means 100 MJ/s (one Joule of energy every second). There are 60x60x24 = 86400 seconds in one day, so the power plant produces 86400 Joule (or 86.4 GJ) per day. Which is equal to 2400 MWh, but that is not an SI unit (because of the 'hour' in it), so preferably use J. DirkvdM 11:03, 3 August 2006 (UTC)[reply]
I think the picture is fake. The plausible types of 'invisibility' I've come across either require you to look through a specific viewpoint (and so would be handy to make your car look transparent from the rear view mirror) or only work at specific wavelengths, currently very small, meaning they could cloak against some detection systems, but not the human eye. I'm trying to work out which this is, or if it's new. Skittle 17:44, 2 August 2006 (UTC)[reply]
Mmmm...yeah, the hand picture looks fake to me. The article is kind of vague about what exactly the research finding or engineering breakthrough is. It sounds kind of like they're talking about a metamaterial, but it's hard to say. And the appications they talk about don't make any sense, at least under that interpretation. If they've invented a specialized material that is invisible, how would that help you look through earthquake rubble? Or see through a hand? In any case, materials that are invisible (i.e. allow visible light to pass through them) are nothing new!! See glass and water and diamond, etc, etc. I really don't know what this article is talking about. But i'm also confused, because I thought the Royal Society was a reputable organization... someone want to clarify, or confirm, or explain why this is legitimate after all? --198.125.178.207 18:08, 2 August 2006 (UTC)[reply]
The alt text for the hand image says "This is what you'd see if the system worked with the atoms in your hand". It doesn't work with the atoms in your hand, so the picture is a fake. There's a slightly less dumbed-down version of the story at hero.ac.uk. --Heron 20:39, 2 August 2006 (UTC)[reply]
Ah. That makes much more sense. The other article did a good job making it sound like a crackpot fraud. None of that silly "seeing through earthquate rubble" stuff. --198.125.178.207 21:10, 2 August 2006 (UTC)[reply]
It did sound awesome though, thanks.
The picture isn't supposed to be a picture of the experiment (it is still all hypothesized anyway), just as a nice looking thing that goes with the article. If you want to learn more, what the articles talk about are nanotechnology's quantum dots used as artificial atoms. — [Mac Davis] (talk)
Possible to reduce ozone levels indoors?
I'm finding that my throat is inflamed and it's just a bit harder to breath lately -- and I think it may be due to elevated Ozone levels in the area. (I read about this effect here.) My question is: is there a way to reduce the amount of ozone in my house? -Quasipalm 18:29, 2 August 2006 (UTC)[reply]
Turn off any ionic air filters, as they are a primary cause. StuRat 05:55, 3 August 2006 (UTC)[reply]
I should also point out that there are other, far more likely causes, such as dry air, mold spores in the air, dust mites, pet dander, chemicals (like formaldehyde) released from new furniture, carpets, paint, and cleaning compounds, etc. StuRat 05:58, 3 August 2006 (UTC)[reply]
Candles are supposed to produce ozone and I thought that was a good thing, or is that just new age mumbo jumbo? DirkvdM 11:08, 3 August 2006 (UTC)[reply]
Ozone indoors (and outdoors, at ground level) is generally a bad thing, although it can kill bacteria and viruses in the air. As for candles, I'd be more concerned with the soot they produce than any small amounts of ozone. StuRat 21:01, 3 August 2006 (UTC)[reply]
You haven't been breathing in air out of your microwave after you put lots of metal in it have you? That might be the cause. It could be inhalation of bug zapper fumes. — [Mac Davis] (talk)
unit question about article : List of countries by electricity consumption
Hello,
I am quite interested in the total number of Watts countries around the world use for industry/civilian purposes/others...
But : List of countries by electricity consumption gives consumption in numbers of kWh, and consumption per capita in kWh as well. Call me crazy, but I thought people use Watts/kilowatts , and they use kilowatthours during a day or year or whatever.
So in short : what is up with the units? Are they for a full year or what?
The unit "kilowatt hour" is a unit of energy - it is the amount of energy transferred in one hour by one thousand watts (a watt is a unit of power). The list you cited is describing how much electrical energy each country consumes in a year. I agree that it is confusing - the article should say that the time period is one year (i'm fairly sure it is).
I'm not sure what you would use "watts/kilowatts" - for. The per-capita figure is simply the total figure divided by the population of the country. If you want to know the power usage, you can find the average power usage of the country by dividing by the number of hours in a year (8760); then you will have the average power consumption of the country in kilowatts. --198.125.178.207 19:19, 2 August 2006 (UTC)[reply]
I think it can be assumed that the figures are kWh/year, since there's a column in the table that states which year the figure is for. I added "/year" anyway, just to make it clearer. --Heron 20:30, 2 August 2006 (UTC)[reply]
Thanks, I discussed this with my dad (he works with industrial energy) and he agreed there is almost no doubt they mean :per year. But I wanted to check with you.
Now forgive my insolence, but I like to think in Watts (megawatts) too. For instance the power generated by windmills is given in megawatts. So... wouldn't it be nice to have a separate column converting it to Watt too? I mean, it would also be nice to compare then with [4]
I am willing to take care of that conversion.
Evilbu 22:23, 2 August 2006 (UTC)[reply]
It's generally assumed that readers will be able to convert between units. Otherwise we'd have to include horsepower, ergs/second, etc. Composite units like kWh/year actually make sense, because giving consumption in watts would give a false impression of continuous consumption when actually electricity consumption is highly diurnal and seasonal. 1 kWh/yr = 0.114 W. EdC 03:35, 3 August 2006 (UTC)[reply]
Wow, that is even more important. Are you saying that the Orders of magnitude article uses Watt as unit while the numbers are incorrect?? Evilbu 11:25, 3 August 2006 (UTC)[reply]
That would indeed be a rather serious error., Especially if it isn't done consistently. What makes you say that?
Btw, Watt and Megawatt aren't different units. It's the same unit with an SI prefix. 'Mega' means million, so 1 MW is 1,000,000 W, The conversion is so easy it doesn't need to be given, but then of course you do need to know about prefixes, but you should learn that pretty soon at school. However, kWh/yr doesn't make sense because it mixes up three units of time: second, hour and year. I keepon trying to add this info to Watt-hour#Explanation, but it keeps on being removed because it wouldn't be interresting info. I think this discussion disproves that.
If you're from the US it may take some getting used to that there is just one unit per quantity in the SI system, but ultimately it's a much easier (because simpler) system. DirkvdM 13:04, 3 August 2006 (UTC)[reply]
I fixed the error mentioned above in orders of magnitude (power). They were just a power of 1000 off :) --Bmk 13:24, 3 August 2006 (UTC)[reply]
Snakes
Is the saying about venomous snakes, "red next to yellow, bite a fellow, red next to black, friend of Jack," true? 69.40.240.98 19:40, 2 August 2006 (UTC)[reply]
To clarify: it is correct regarding coral and milk snakes, not poisonous snakes in general. – ClockworkSoul 20:34, 2 August 2006 (UTC)[reply]
Yes, thanks ... also, it should say "red on yellow, kill a fellow," as a milk snake can certainly bite. Its bite is not venomous, but it could be painful. --Ginkgo100talk · contribs · e@ 03:26, 3 August 2006 (UTC)[reply]
Yeah, I meant to say "kill a fellow". Thanks. 69.40.240.55 04:31, 3 August 2006 (UTC)[reply]
I always thought the "friend of Jack" part was a really lousy rhyme in comparison to the "kill a fellow" part. Jack? Jack who? In any case, this little rule does take the fun out of movies when one can easily see that a "deadly snake" is a relatively harmless milk snake. --Fastfission 05:00, 3 August 2006 (UTC)[reply]
I agree. When I heard 'friend of Jack', I thought 'friend of the devil', either meaning the snake was really bad or that the person who came in contact with the snake would be dispatched to the afterlife. Combined with the 'bite a fellow' mistype, I thought the rhyme was backwards.--Anchoress 06:11, 3 August 2006 (UTC)[reply]
Don't ask me, I've never heard that rhyme before, and I know next to nothing about snakes (which is very surprising, given that I am the Devil incarnate). :--) JackofOz 03:22, 4 August 2006 (UTC)[reply]
On the other hand, I'm not above biting a fellow or two, given half a chance. You have been warned. JackofOz 03:23, 4 August 2006 (UTC)[reply]
Alcohol Gel and Salt
While playing around with some alcohol gel, I sprinkled some common table salt into it, and found that it causes the gel to seperate into a thinner liquid (just the alcohol and alcohol soluable substances?) and a whitish, flaky solid. Has anyone else see this phenomenon? What causes it? Any ideas? Brian Schlosser42 20:50, 2 August 2006 (UTC)[reply]
Having just read common ion effect, it doesn't really explain how the addition of a substance containing one ion (which is present both substances) causes the solubility product of one to be exceeded. Salting out is another phrase for it. G N Frykman 22:31, 2 August 2006 (UTC)[reply]
Might be interesting to read the ingredients of the alcohol gel to see what ions or other dissolved solids might be present. DMacks 22:57, 2 August 2006 (UTC)[reply]
Here are the ingredients from the Purell website- Active: Ethyl Alcohol Inactive: water, isopropyl alcohol, glycerin, carbomer, fragrance, aminomethyl propanol, propylene glycol, isopropyl myristate, and tocopheryl acetate. Brian Schlosser42 12:17, 3 August 2006 (UTC)[reply]
I don't have an answer, but intuitively, it doesn't seem illogical that the salt could de-emulsify the substance, causing the liquid to separate from the gelling agent.--Anchoress 06:09, 3 August 2006 (UTC)[reply]
Molecular orbitals and symmetry
I was going to ask this question about benzene, but then it occurred to me that acetylene is a simpler molecule with the same basic problem. Acetylene has two pairs of electrons in two perpendicular pi bonds, but its electrostatic potential map has full cylindrical () symmetry. How is this possible if neither of the pi orbitals has cylindrical symmetry? —Keenan Pepper 21:05, 2 August 2006 (UTC)[reply]
Now I'm curious to know the answer too. Also, the second paragraph of acetylene says, "As the molecule cannot twist around the triple bond, all four atoms lie in the same straight line, with bond angles of 180°." Now, the first part of that sentence makes sense with the two pi bonds, and would go agaist the cylindrical symmetry. But the second part of that sentence seems to be a non-sequitur. The bond angles would be 180 degrees either way, right? --Allen 22:32, 2 August 2006 (UTC)[reply]
"Not twisting around a pi bond" is how we normally explain the existence of cis and transisomers in substituted ethenes to our pupils. The phrase is meaningless with ethyne - twisting of this linear molecule would mean bending, and I am sure that there is an IR absorption for triple bonds doing this! The cylindrical symmetry in ethyne (lengthwise) implies indistinguishable overlap between the two perpendicular pi bonds.--G N Frykman 22:48, 2 August 2006 (UTC)[reply]
The "twisting" phrase is a bit odd for a triple bond. There presumably is no twisting in the olefin sense (rotation of the orbitals on one atom in a way that breaks and then reforms a different π system), but that would have no effect on the geometry. I'd be interested to see an electrostatic map that includes orbital information and is cylindrical. For most purposes, treating the triple bond as a "fat bond", a cylinder of π cloud, gives good enough results. DMacks 23:11, 2 August 2006 (UTC)[reply]
There is a fundamentally simpler answer to this question. Recall that the px, py, and pzorbitals are actually probability maps for where electrons will be in space at a given time. Combined, all three p orbitals map to a perfect sphere. The usual drawings of the orbitals are actually drawings of the area in space in which there is a 60% probability that an electron occupying the orbital will reside at a given instant in time. There is, however, a 40% probability that one or more electrons will be outside of this area at a given instant. Thus, in acetylene, the py and pz orbitals that hybridize to form the pi bonds seem to be asymmetric when drawn, but this is because you are only considering 60% of the probability density for each electron. If you instead consider the volume of space for which there is a probability density that one or more of the four pi electrons will reside at any given instant, you will actually see a perfectly symmetric tube surrounding the x-axis of the molecule. Hence, if there is a lower probability that a py electron will reside in a specific area, this is compensated by the fact that there is a higher probability that a pz electron will be in this area. As such, it is correct to say that acetylene has symmetry.
As for rotation around pi-bonds, there is actually some computational evidence to suggest that it requires less energy to rotate around a triple bond than a double bond. While this may seem counter-intuitive because two pi bonds must be broken to rotate around a triple bond (versus one for a double bond), it actually makes sense because the overlapping p orbitals must only rotate 45 degrees out of phase before they come into phase with a new set of p orbitals and begin to re-form a pair of pi bonds. Since energy varies non-linearly as the orbitals come out of phase, the net energy barrier to rotation around a triple bond is lower than around a double bond. However, since the four atoms in the triple bond lie along a single axis (this is due to electron repulsion, NOT molecular orbitals: electrostatic repulsion leads to molecular geometry which, in turn, leads to the mathematical construct of molecular orbitals - probability densities determined by specific molecular conditions unique to each molecular environment), this cannot be tested experimentally and is therefore basically irrelevant. -- C. S. Joiner (talk) 01:02, 10 August 2006 (UTC)[reply]
Brushing your teeth
Everyone in the know seems to recommend brushing your teeth for 2.5 minutes, twice or three times a day. But what I wonder is, after the first 30 seconds or so, what is being cleaned off my teeth? And is it better to brush my teeth twice a day for 2.5 minutes, or five times a day for a minute?--Anchoress 21:41, 2 August 2006 (UTC)[reply]
My Sonicare manual says that you should brush for two minutes. As for what is cleaned off, it is probably like scrubbing a wall. If you scrub for too long, you will through the paint and into the drywall. I don't think it is a matter of how many times you brush. It is when. You do not want food - especially sugar - sitting on your teeth. So, brushing every time you eat and then not drinking sugar-water between meals will not only help your teeth but also help your breath. --Kainaw(talk) 23:09, 2 August 2006 (UTC)[reply]
Its really something that is more qualitative than quantitative: How well you brush, not how long. — [Mac Davis] (talk)
But brushing straight after you eat can cause slight erosion of the enamel on your teeth, which can build up over time if you do it regularly. So wait a while after eating. Or brush before eating to remove the plaque so there's nothing for the sugar to stick to. Sugar doesn't just stick to enamel. At least, that's what I was taught. Skittle 12:49, 3 August 2006 (UTC)[reply]
I thought that brushing after or before eating was a bad idea, which is why just before going to bed is the best time to brush. Also, it depends on the food. Sugar rots your teeth, so you should avoid eating that, and especially around brushing time. Acids are also bad. One of the worst combinations is yoghurt with sugar. Or cola, which also contains loads of acid and sugar. When I was a kid I drank loads of cola (almost a litre per day!) and almost all my fillings are from around that time. I got accustomed to getting new filings every time I went to the dentist. From my twenties that stopped and until a few years ago (I'm now in my fourties) I almost never had any problems at the dentist. Also, when I was a teenager I brushed my teeth more often than later on in life, so that should give the previous explanation extra credibility, unless brushing your teeth (the way I did it?) is actually bad for your teeth. DirkvdM 13:22, 3 August 2006 (UTC)[reply]
My Sonicare says to spend 2 seconds on each tooth, on the front surface and then the rear. Given the standard human allotment of 32 teeth, that's 128 seconds. --LarryMac 14:59, 3 August 2006 (UTC)[reply]
I don't know what 'my first sony-care' is, but does it do one tooth at a time. My toothbrush is several teeth wide. Still, I spend more than 2 minutes brushing my teeth, but I do it only once a day - the quality vs quantity thing that MacDavis mentioned, just a different interpretation of the principle. :) DirkvdM 19:13, 3 August 2006 (UTC)[reply]
Ah, it's sonic air! DirkvdM 18:48, 4 August 2006 (UTC)[reply]
Having been to the dentist this morning, I'm in a good position to chime in here! Apparently, the number 1 cause of adult tooth loss in the UK is not tooth decay, but gum disease. The time spent brushing your teeth (and, as importantly, flossing), is to improve the health of your gums; preventing your otherwise healthy, decay-free teeth from falling out! --Dweller 14:10, 4 August 2006 (UTC)[reply]
Considering my background, perhaps I should say something as well. Though there may be some technical result found in research saying that it is harmful to brush after eating, in reality this is not seen as a problem. Brushing your teeth after you eat is generally not seen as causing detectable levels of damage. However, how you brush is important, and not necessarily how often. If you brush 26 times a day but not in a manner to remove all the plaque, then those 26 times really do no good. Since the point of brushing is to remove all the plaque, you probably will not remove all the plaque off a tooth on your first stroke--- which is why you will have to spend some time on it. And a bit unrelated, sugar helps form tooth decay, but the frequency of your sugar intake is more important than the amount. So, eating a bag of candy in 30 minutes will be less harmful for you teeth than eating the same bag of candy slowly throughout the day. - Dozenisttalk 23:05, 8 August 2006 (UTC)[reply]
Valium + Alcohol = ?
I'm currently taking valium, prescribed by my doctor (5mg, every 3 hours). Is it safe to drink *any* alcohol at all? What happens when you mix the two? Is it a case of just getting drunk quicker or could it kill me?
Valium + Alcohol = Death. They are both depressants. Its best to stay away, the combination of the effects can cause your heart to stop if the right amounts are taken. Don't be stupid. pschemp | talk 22:20, 2 August 2006 (UTC)[reply]
a) I agree with pschemp; they're both nervous system depressants. b) talk to your doctor or pharmacist. This is definitely near the top as far as questions that should not be settled on the advice of anonymous posters.--Anchoress 22:24, 2 August 2006 (UTC)[reply]
I think it was answered quite well here, by saying they should NEVER be taken together. You can't go wrong by taking that advice. StuRat 05:50, 3 August 2006 (UTC)[reply]
It's always a good idea to not be stupid. That should, however, not be confused with ignorant. If there is any danger in combining valium with alcohol, there should be a warning on the valium bottle (or whatever that comes in). If there isn't then that would be stupid (and if you're in the US you might think of sueing them). DirkvdM 13:25, 3 August 2006 (UTC)[reply]
There is a warning: "Drunk, pregnant children operating heavy machinery while driving should not take this product". Or something like that. :-) StuRat 21:09, 3 August 2006 (UTC)[reply]
Value and alchohol can make your brain work like its never worked before. that can either kill you or make you a super human. you choose the red pill and your free.
What mushroom is this?
Hey, I have this mushroom growing in my front yard and I was wondeirng what type it is. Thanks for any help, Newnam(talk) 23:29, 2 August 2006 (UTC)[reply]
My Mushroom
I dunno, but don't eat it no matter what anyone here says! :) ok, now more knowledgeable people can take over and identify it. --18.239.5.61 02:09, 3 August 2006 (UTC)[reply]
It looks like a portobello, I think. Black Carrot 03:38, 3 August 2006 (UTC)[reply]
Or it could be a death cap which will kill you in about the nastiest way there is. Weregerbil 06:00, 3 August 2006 (UTC)[reply]
It doesn't look the least bit like the death cap. Are you just trying to scare people? DirkvdM 13:30, 3 August 2006 (UTC)[reply]
It looks a lot like the death caps I see in the forests where I go mushrooming (and they are not portobellos as those are rare in this climate). All white, pronounced collar, and a sock (is that what it is called in English). Given the deadly nastiness of death caps I certainly don't mind scaring people away from all white mushrooms that can't be positively identified. Like for all mushrooms: I love picking and eating them, but not enough to die for a meal. Weregerbil 20:44, 3 August 2006 (UTC)[reply]
Yeah. You can see from the protruding spots on top that it's almost certainly a death cap, and absolutely not a portobello. Do not eat this, if you were considering it. If you have a mouse problem, cut it up, soak the pieces in milk, and wait a couple days. All the mice in your house will die fairly quickly, because the milk attracts them. Sashafklein 22:40, 3 August 2006 (UTC)[reply]
Thanks for all the imput. I certainly will not eat it. I was just wondering, as this mushroom was by itself, and the first I ever noticed in my yard. Thanks again, Newnam(talk) 03:43, 4 August 2006 (UTC)[reply]
Might be a destroying angel too, or some other similar Amanita species. If the photo was a bit sharper it'd make the identification easier, as would seeing the gills and, most important, knowing where the photo was taken. I could be wrong, of course — I'm certainly no mushroom expert — but something about the general shape does scream Amanita to me, at least enough that I'd leave the thing well enough alone. —Ilmari Karonen (talk) 23:51, 10 August 2006 (UTC)[reply]
August 3
Human-raised birds
Say if I was to hatch a bird (e.g. a crow) from the egg myself and raise him from chick to adulthood without him ever seeing another bird, would he still be able to fly? Or would he not know how and walk around like a human instead?
It would depend largely on if it fledged properly. Actually, the article uses the term a little differently from how I use it; I use fledge to mean "to learn to fly as a chick at the right developmental stage." In wild birds this seems to happen when the flight feathers are significantly (but not necessarily completely) grown out, which incidentally is right now in the temperate northern hemisphere, and it's a time of high mortality for chicks. With many pet birds such as parrots, if they don't learn to fly at the right time during their "chickhood," often they never really do. I had a yellow-collared macaw who never fledged and who absolutely refused to fly voluntarily, even though I let his flight feathers grow out and tried to teach him with gentle tosses to the bed. I also have a ringneck parakeet who didn't fledge as a chick either, but he has done better at learning as an adult. Neither of these birds was raised by other birds; what matters with a human-raised bird is whether it is taught to fly. --Ginkgo100talk · contribs · e@ 03:35, 3 August 2006 (UTC)[reply]
It's really hot in here...
and the airconditioner isn't working. how hot does it have to be before a computer goes from sluggish to not working at all? it's already over 100 (oF) in here, how much more can it take?--152.163.100.74 01:48, 3 August 2006 (UTC)[reply]
It depends on how efficient your computer's cooling system is. Generally consumer CPUs are rated at anything between 65° and 95°, so the ambient temperature isn't going to cause problems per se, but it will obviously make cooling less efficient. You can monitor the internal temperature sensors with free tools e.g. Gnome Sensors Applet. EdC 03:04, 3 August 2006 (UTC)[reply]
Removing the computer cover and pointing a fan at it can help dramatically, if it tends to overheat. StuRat 05:45, 3 August 2006 (UTC)[reply]
Using munitions to disrupt hurricanes
Hello all -
I have a general question about using munitions to disrupt hurricanes. Is something like this possible? I read over the hurricane page (specifically the section on Artificial dissipation) and Googled this topic, but I really did not find anything that really answered the question.
Here is the scenario: If a Rita/Katrina-type hurricane should brew in the Atlantic Ocean, is it possible to drop several powerful cluster bombs throughout the eye (and exterior) of the hurricane and disrupt or eliminate the hurricane, or at the very least lessen the force of the hurricane. I would imagine that thousands of explosions within the center of the hurricane, at the waters surface, and beneath the waters surface would severely disrupt the strength of the hurricane. I think this might be akin to using explosion to put out fires: the vacuum created by the explosion might disrupt the wall and eye of the hurricane, thus decreasing the force of the hurricane.
Simply put, there's no way that would work. Here is a good article explaining why. Titoxd(?!?) 03:46, 3 August 2006 (UTC)[reply]
Thanks for the comment. I just would imagine that if there were thousands of powerful cluster bombs being detonated at all altitude levels, at the waters surface, and under water, this would have the potential to disrupt the hurricane. -Rangermike 03:52, 3 August 2006 (UTC)[reply]
As a side note, I would not advocate using nukes to disrupt the hurricane; conventional munitions only. -Rangermike 03:56, 3 August 2006 (UTC)[reply]
There's just not enough bombs to actually do anything to the hurricane, and tropical cyclogenesis is not something we can completely predict yet (as a look at 2006 Atlantic hurricane season's talk page archives show). Titoxd(?!?) 03:56, 3 August 2006 (UTC)[reply]
Thanks for the info! -Rangermike 04:05, 3 August 2006 (UTC)[reply]
I would think many nuclear weapons would be needed to disrupt a hurricane. A new hurricane would spawn almost immediately, in the same area, however, as the water temp cooling would stop once the old hurricane was disrupted. This hot water would then generate a new hurricane in the same area. Another method of disrupting hurricanes would be to dump millions of tons of a special gel (which absorbs a million times it's weight in water) from cargo planes, into the hurricane. This particular gel (I can't recall the name) dissolves in sea water, and is nontoxic. Unfortunately, the hurricane would also respawn after this method was used. The real cure for hurricanes, then, is to prevent to water from overheating in the first place. I propose partially covering the tropical oceans with solar collectors to generate electricity and prevent a heat buildup. Perhaps in a century of two we can manage it. StuRat 05:41, 3 August 2006 (UTC)[reply]
You're somewhat correct that a tropical cyclone would probably remain in the same place, but I doubt it'd be a new hurricane because of high SSTs. Hurricanes don't just "spawn" in hot water, else New Orleans would be hit every other month when the Loop Current sheds an eddy. The larger-scale structure takes too long to develop and they're fairly fragile while developing. If you could really just get rid of the hurricane entirely or put it back to its "random mess of convection" stage, it would take a long time for it to return to its prior strength.
But using bombs (i.e. randomly blowing up the hurricane's structure) would probably only degenerate it back to a tropical storm's structure at most if you're lucky and get the right bits. Tropical storms already aren't that organized and you probably won't find any structures to bomb on a small-enough size scale. Also, bombs probably wouldn't be able to stop the winds and low-level convergence and upper-level divergence already spun up. The same things that were favorable to the intensity of the 'cane before would probably act to re-strengthen the same storm. —AySz88\^-^ 06:58, 3 August 2006 (UTC)[reply]
Given that hurricanes are a phenomena that is hundreds of km wide, I doubt very much that any munition could have any significant effect, but seeding the clouds to make rains at appropriate location(s) and time(s) could shift the path of an hurricane enough to avoid populated areas.
HereThat website brings up an interesting question. Is it possible to harness a large portion of that energy? Deltacom1515 00:25, 4 August 2006 (UTC)[reply]
Gasoline
Does gasoline go bad or lose octane overtime?
Not if it's stored in an airtight container. If it's left out in the open, though, it will quickly evaporate, forming dangerously flammable vapor. —Keenan Pepper 04:03, 3 August 2006 (UTC)[reply]
In the UK, what is sold as "unleaded petrol" does indeed "go off". Opinions differ on how long that takes. Notinasnaid 10:56, 3 August 2006 (UTC)[reply]
Scientific question
How fast can a three legged cheetah run?
Thirty-five miles an hour [5]Rockpocket 04:24, 3 August 2006 (UTC)[reply]
Aaaawwwwww!!!! Rockpocket, you ROCK! Rock by name, rock by nature.--Anchoress 05:45, 3 August 2006 (UTC)[reply]
Given that the average 4-legged cheetah can run at up to 70 miles an hour, the average three-legged one would logically be able to run at 52.5 mph.
Then again, if it's on nandrolone or some Testosterone-based performance-enhancing drug, who knows how fast it can go if it's "cheeting". --Dweller 14:16, 4 August 2006 (UTC)[reply]
I had a zoology professor who claimed a no-legged cheetah could run six miles per hour. --Ginkgo100talk · contribs · e@ 20:14, 3 August 2006 (UTC)[reply]
Sorry I left that all without context ... my professor's point was that the mechanics of the cheetah's spine contributes something like 10% to its speed.
It would then move a bit like a caterpillar. I'd love to see that! DirkvdM 18:54, 4 August 2006 (UTC)[reply]
Step away from the cheetah, Dirk. Skittle 19:43, 4 August 2006 (UTC)[reply]
List of countries by electricity consumption - part 2
In the List of countries by electricity consumption someone seems to have gone through the trouble of filling in the per capita values for scandinavian countries, where these values are very high. Same for Canada (even higher than the US). For other western countries (excluding the US) it's much lower. I can understand a higher energy consumption due to heating, but why do they consume two to four (!) times as much electricity? DirkvdM 13:37, 3 August 2006 (UTC)[reply]
I looked at that and I thought that it isn't accurate to claim that each person is consuming 2-4 times the electricity. The figure is dividing the country-wide consumption by the population. So, a completely robotic factory with only a handful of workers will consume a lot of electricity. That is being added to each person's average usage on that specific table. Therefore, I expect industrialized nations to have a much higher per-capita usage due to business/factory/government use and not really due to personal use. --Kainaw(talk) 13:47, 3 August 2006 (UTC)[reply]
Norway, for instance, produces a lot of cheap hydroelectric power, and has the lowest population density in Europe. Despite having no bauxite, they are one of the leading producers of aluminium.EricR 14:13, 3 August 2006 (UTC)[reply]
The situation in Canada is similar. There are a number of sites that produce a lot of hydroelectricity, and Canada imports enough bauxite to refine nearly 3 million tons [6] of aluminum each year; at 15 kWh per kilogram of aluminum produced, that comes about 40 GWh of electricity consumption per year. In other words, a single resource industry accounts for about 8% of Canada's total electricity consumption. Most of that aluminum is exported to other countries – Canada is the second-largest aluminum exporter in the world, after Russia[7] so counting that electricity use as 'Canadian' gives a somewhat skewed picture of that country's consumption. TenOfAllTrades(talk) 14:33, 3 August 2006 (UTC)[reply]
I guess industry could account for some of it - I also assumed it's because it's so cold all the time that heating costs were higher. But I don't know. --198.125.178.207 17:39, 3 August 2006 (UTC)[reply]
There ought to be a correlation between per capita wealth and consumption. For energy, think of heating houses, cooling houses ; and this, mostly in countries located where temperatures vary : wealth is related to temp variation (personal research). --DLL 18:32, 3 August 2006 (UTC)[reply]
Like I said, I assume heating is not done with electricity, so that couldn't cover it then. And bauxite represents 'only' 8% of the electricity consumption of Canada, but the total consumption is more than double that of other western countries, so that can't explain it. And for Norway and Iceland it's even three resp four times as high. Those are huge differences. But Norway does have a lot of water power, so maybe they use more electricity and less fossil fuels. Hold on, don't they have a lot of cars running on electricity? That might explain it. And then Iceland. That has a lot of geoithermal power. But I can't think of how that could explain it. Is it just a coincidence that countries close to the North Pole use more elctricity? DirkvdM 19:24, 3 August 2006 (UTC)[reply]
Aaaaw c'mon, let's just come out and say it! Canadians are the energy hogs of the entire world! :-) Oh sorry, can't talk any more, I have to take my recycling out of the dishwasher, and the dryer's finished heating up the bathroom for my shower. ;-)--Anchoress 19:32, 3 August 2006 (UTC)[reply]
Stop that - don't you know it isn't legal to criticize countries other than the US? --Bmk 19:44, 3 August 2006 (UTC)[reply]
Oops, sorry. Well what if I said it's the US's fault that we're such energy hogs?
From a soon-to-be-aired episode of Oprah
[Canada] (sobbing) He doesn't respect me! He never listens to me! I wouldn't have a problem with reckless consumption if I got the acknowledgement I deserve! I mean, how big do I have to be before I get some recognition?
[Oprah] There there, little Canada. When he runs out of steam I'm sure he'll notice you.
They don't have to. If gravity didn't pull down on it, making the bottom thick and heavy while the top becomes thin and fragile, it would just go on being a happy little bubble. But, gravity is evil and hates soap bubbles, so it pushes down and down and eventually the top is so thin that the surface tension cannot hold. The little soap molecules cry as their fingers slip and pop - no more soap bubble. --Kainaw(talk) 14:02, 3 August 2006 (UTC)[reply]
I disagree. Even without gravity the bubble solution would quickly evaporate and burst the bubble. Perhaps in a zero g, 100% humidity environment they might last until they hit something. StuRat 20:44, 3 August 2006 (UTC)[reply]
My answer was limited in scope to Earth-bound bubbles. Gravity gets to them faster than the environment. I learned about it in a strange place - watching a documentary on making colored bubbles. Turns out that making bubbles with a solid color is very hard. Gravity pushes the dye to the bottom and then POP, you get a stain on the floor. --Kainaw(talk) 13:34, 4 August 2006 (UTC)[reply]
The solution: bubbles in space. --130.161.182.77 14:12, 3 August 2006 (UTC)[reply]
..with the pressure equalized inside and out? Can a bubble even exist in space?--Shantavira 14:47, 3 August 2006 (UTC)[reply]
"Soap bubbles in space" - interesting question. Of course the Earth itself is in space and it is possible to make soap bubbles here. In zero gravity (or microgravity really) we find soap bubbles on the International Space Stationhere. For bubbles in vacuum: possible, but the liquid will evaporate quickly and thus the bubble has only a short lifetime[8]. Weregerbil 15:06, 3 August 2006 (UTC)[reply]
In Yakov Perelman's Physics for entertainment, he mentions that the bubbles made of right solution are not as short lived as we presume them to be. He cites examples where bubbles were stored for (I think) about a month --Wikicheng 04:48, 4 August 2006 (UTC)[reply]
What about dust, too? I bet that may have something to do with it, along with surface tension. --71.98.25.103 03:13, 9 August 2006 (UTC)[reply]
Bike Brakes At The Hub
My bike has brakes that occur at the hub of the wheel, instead of at the top (pressing against the wheel rim) like I'm used to. What kind of brakes are these? --130.161.182.77 14:01, 3 August 2006 (UTC)[reply]
last week I experienced the not so frequent pleasure of finding a hedgehog in my garden. I had heard that you should always check the little guys for ticks (care for sick/wounded hedgehogs can be done for free in bird centers here), but as usual he ran off almost immediately.
When I went to Wikipedia, to my amazement I discovered that hedgehogs are not to be found in the USA at all! Does the average US'er even know what a hedgehog looks like?
Anyway, are there any other surprisingly non present animals ( in parts of the world with about the same climate and flora, I am not surprised there are no elephants here).
Yes, there are many. Australia is a great place to find unique animals that could survive elsewhere, but haven't really ventured out into the world. As for Americans and hedgehogs, there is a small group of people in the U.S. that own domesticated hedgehogs as pets. However, most couldn't tell the difference between a hedgehog and a porcupine. Finally, the trick to picking up hedgehogs is to scoop them from both sides. I face them as I do so, I think it is less traumatic (though it has to be frightening to get picked up) if they see it coming. They will roll into a ball and make a lot of huffing and popping noises. After a long time (I've had it take over 10 minutes), they will relax. Of course, it is actually easier to inspect them as they are rolled up in a ball than it is to inspect them when they are relaxed and the quills are laying flat. --Kainaw(talk) 14:30, 3 August 2006 (UTC)[reply]
Of course I know what a hedgehog looks like..--64.12.116.74 15:20, 3 August 2006 (UTC)[reply]
I was extremely surprised to find out recently that there are no Skunks in Africa, Europe and most of Asia. You don't know what you're missing.--Anchoress 19:27, 3 August 2006 (UTC)[reply]
Anybody want to trade hedgehogs for skunks? I'd take a hedgehog infestation any day over the tyranny that skunks have. As Darwin wrote of them: "Conscious of its power, it roams by day about the open plain, and fears neither dog nor man. If a dog is urged to the attack, its courage is instantly checked by a few drops of the fetid oil, which brings on violent sickness and running at the nose. Whatever is once polluted by it, is for ever useless." --Fastfission 19:32, 3 August 2006 (UTC)[reply]
Talk to Standing Bear. He has a lot of hedgehogs. Of course, he will want to ensure you give them a nice home. --Kainaw(talk) 19:46, 3 August 2006 (UTC)[reply]
One obvious animal present, just, in the UK but not in similar habitats in the U.S.A. or, as far as I know, elsewhere outside Europe is the Red Squirrel. That though is because the, more aggressive & less attractive, Grey Squirrels outcompete them. AllanHainey 15:03, 4 August 2006 (UTC)[reply]
What kind of Praying mantis is this?
Can anyone help me find the latin name for this particularly beautiful Praying mantis? It was uploaded to Wikicommons by a French speaking user, who labelled it a Sudanese mantis. But I haven't been able to find any other pictures of Sudanese mantises, I'm not sure whether that is the actual vernacular name or just a description (a mantis found in Soudan). Help would be appreciated. Do you think it could be Blepharopsis mendica? --woggly 15:48, 3 August 2006 (UTC)[reply]
Soudanese Mantis
It looks a lot like this fellow, who is a young Blepharopsis mendica, I think (the page it is from lists it as a "larva"). --Fastfission 19:30, 3 August 2006 (UTC)[reply]
Hmm. Yes and no. The eyes are angled differently from the head, but that might just be a difference in the angle of the photograph... I'd really like to know, because I want to nominate this for a featured picture, and for that it needs to be illustrating the proper article (not just Praying mantis - there are too many other good pictures there). Anyway, it wouldn't be a larva, but a nymph. Thanks for finding that picture, which is the closest I've seen so far! --woggly 19:59, 3 August 2006 (UTC)[reply]
I've loooked at more Blepharosis mendica pictures, and I don't think this is it. The Blephs all seem to have mottled eyes and long antennae, whereas this guy has distinct "pupils" and short or no antennae. Still looking... more ideas would be appreciated. --woggly 05:42, 4 August 2006 (UTC)[reply]
Logo or symbol or abbreviation for engineers
Is there any internationally recognized logo or symbol for engineers? e.g. red cross for doctors.What is the short title for an engineer(Er or Ir or Ing) e.g. Dr for doctor.
I've only seen "Eng." used. It is rarely used alone. For example, I am a CSciEng, not an EEng. Then, some drop the "ng". EEng is often just EE. --Kainaw(talk) 17:27, 3 August 2006 (UTC)[reply]
For an international title there would have to be an interntionally accepted exam, at least that would make sense. Then again, dr is indeed rather international, without there being international exams (afaik). Btw, Ir and Ing are Dutch. Are you? Or are these titles used elsewhere too? DirkvdM 19:33, 3 August 2006 (UTC)[reply]
I don't know of any internationally recognized logo but in context something like a gear would probably be recognized by most people. --Fastfission 21:31, 3 August 2006 (UTC)[reply]
The closest thing to an 'official abbreviation' will be a variant of P.E., which at least in the US stands for Professional Engineer. It is used after one's name, as in John Doe, P.E. But it wouldn't be used in typical day-to-day correspondence, only in situations where the title would be familiar to the audience. If our John Doe wrote a letter to the editor of the newspaper, he wouldn't include the P.E. after his name; but if he was authoring a report commissioned by a client of his engineering firm, then he would.
In India, I have seen people use Er. as the abbreviation for engineers (So I should be Er.Wikicheng :-) ), though it is not very common. Electrical_Engineer#Engineer.27s_degrees_in_Europe has some abbreviations of other countries which may belp--Wikicheng 05:08, 4 August 2006 (UTC)[reply]
In Canada, the common abbreviation for a professional engineer is P.Eng. in English and, I believe, Ing. in French. I think that Ing. is also used in Germany. As far as logos or symbols, there's no clearly accepted symbol, particularly since engineers do so many different types of work. I've seen a cogwheel, chains, the beaver and the Vitruvian Man used, but not universally. In Canada, the Iron ring is understood as an engineering symbol. --ByeByeBaby 06:53, 5 August 2006 (UTC)[reply]
Hepatitus c and Vitiligo
i am looking for advice how to treat a Vitiligo (1 year) if have a Hipatitus c (5 years).
Vitiligo and Hepatitis C may have some useful information about each condition, but for a real answer, you should see a doctor. (Note the statement at the top of this page: "If requesting medical...advice, please consider asking a doctor...instead.") -- Scientizzle 19:59, 3 August 2006 (UTC)[reply]
cat with neurological problem - stroke?
He had a temperature of 104 F at the beginning, now gets around slowly and shakily, barely responsive to stimuli, licks soft food, doesn't drink without bottle help, wants to put his head into corners, has forgotten how to use litter box. Does anyone have ideas for rehabilitating a cat who's had a stroke, or something like it? --Halcatalyst
That doesn't sound like a stroke. That sounds like sickness. He should go to a vet. After a stroke, cats have trouble moving, usually the back legs. They don't curl up and wait to die. --Kainaw(talk) 19:27, 3 August 2006 (UTC)[reply]
Was that a useful addition? What's this tendency to point out the blatantly obvious, even when that was already done by the previous poster? DirkvdM 19:38, 3 August 2006 (UTC)[reply]
It was added before I noticed Kainaw had already added his veterinarian comment. Note the similar edit times. And the obviousness of the comment isn't really relevant. It is the best possible advice. --198.125.178.207 19:46, 3 August 2006 (UTC)[reply]
We did take him to a vet and he was in the hospital for several days. They eventually diagnosed a neurological disorder and released him to our care. They said they had never seen anything like this and also suggested it might be time for euthanasia. We're hoping there might be something to be done to help him recover. --Halcatalyst 19:40, 3 August 2006 (UTC)[reply]
(As I've mentioned many times, I work in a hospital, so I can ask random doctors for advice - but do not consider it binding advice as I'm just a comptuer programmer)...
According to a doctor here, if it was a human he would first send it to MRI to test for pressure on the brain. Then, he would send it to GI to have the intestines checked. Because of the fever, he suspects a viral infection. --Kainaw(talk) 19:44, 3 August 2006 (UTC)[reply]
The vet at first thought it was a gastro-intestinal infection, but the tests came back normal. And he hasn't improved on the antibiotic (which we're still giving him. He's also on prednizone. --Halcatalyst 20:08, 3 August 2006 (UTC)[reply]
I know how it feels to see your pet going through suffering. I can't help you with the treatment, but I wish you the best of luck. --mboverload@ 23:22, 3 August 2006 (UTC)[reply]
I agree. My last hedgehog had very similar symptoms. On Monday he didn't eat much, but kept running around like normal. On Tuesday, he didn't want to run. He just curled up by me and kept sleeping, so I made an appointment for the vet on Wednesday. On Wednesday morning, I got him up to check on him and he was the same. I got dressed and went back in and he had passed away. Later, I found out he had multiple cancerous tumors in his intestines. I was frustrated because I had taken him to the vet a month earlier and he got a clean bill of health. I felt like the vets didn't take it seriously because it was a hedgehog and not a dog. There is a lot of emotion involved - pain, sorrow, anger. I now feel that I should have listened to my doubts about the first vet and gone to a different one. Keep finding a different one until you find one that isn't just going through the motions to cash a check. I'm sure there are a few vets out there that take the job seriously. They are just hard to find. --Kainaw(talk) 13:26, 4 August 2006 (UTC)[reply]
I'm not sure that was a redundant addition. In some parts of the world vet is not commonly the abbreviation for veterinarian; but for combat veteran. Many of them are hungry, but that doesn't mean they will want your cat. Notinasnaid 13:55, 4 August 2006 (UTC)[reply]
My mentor is an immunologist (PhD) and vet (DVM), and he agrees that given the information supplied that the source of the cat's neurological symptoms is most likely suffering an infection. He also highly recommends that you look around for possible sources of the infection: other animals contacts (wild or otherwise), and the like. Possible contagion to or from other animals is a very serious consideration (though it is highly unlikely that the pathogen is infectious to humans). – ClockworkSoul 19:02, 4 August 2006 (UTC)[reply]
Because of the high temperature, the vet[erinarian] ran a full set of tests, which were negative. Nevertheless, the cat has been on antibiotics for ten days now. In a week, he has urinated a couple of times and only one very liquid bowel movement.
Thank you all for your interest. Poor Ozzie is worse these last two days; he can't get around at all anymore, but he is eating soft food ravenously. He can't drink by himself (it's as if he doesn't know what water is), and I hope I'm getting him enough hydration. He doesn't appear to be in any pain. --Halcatalyst 01:44, 6 August 2006 (UTC)[reply]
Ref Desk Archive Problem
I keep on ending up on an archived page accidentally. It seems when I edit certain questions on an active Ref Desk page I end up in an archived page, after I finish. Does anybody know what's going on here ? It has been happening for quite some time, but only happens, say, 10% of the time. StuRat 20:50, 3 August 2006 (UTC)[reply]
How do you get out from the archived page into the real world again? One can't make a phone call from a page. --LambiamTalk 21:24, 3 August 2006 (UTC)[reply]
Weird, I thought I answered this earlier.It's because you are editing a section from an archive that is transcluded onto this page. When you edit the section and save, it sends you to the page that you actually edited. Actually, if you hit 'edit this page' at the top instead of just a section, you'll easily see that the first few days displayed on this page are transclusions of archives. Hyenaste(tell) 01:37, 4 August 2006 (UTC)[reply]
So why do we do that ("transclude" archived pages that appear to be on the active ref page) ? I would think they should either be on the active page or the archived page, not somewhere in limbo between the two states. StuRat 05:34, 4 August 2006 (UTC)[reply]
Ready to learn easy maintenance tricks ? OK, listen : never listen to complaining customers (I admit this only occurs in sci-fi stories about horrid old admins with tentacles). --DLL 15:29, 4 August 2006 (UTC)[reply]
Physical basis of the Mendelian ratios?
What's the physical basis of some genes being dominant and recessive? Is this well understood at the moment? I poked around the pages which looked most relevant here (recessive gene, dominant gene, Mendelian inheritance, classical genetics, molecular genetics) but saw nothing about this. I'm just curious, that's all. Is this a universal function of all DNA-carrying organisms? I can see the evolutionary advantage of recessive genes but it surprises me that all organisms have them—one could hypothetically imagine DNA that dealt with only dominant genes. Which would lead me to think that either the ability to have recessives is so basic and advantageous (in a way I don't understand) that it would have outpaced a dominant-only arrangement early on, or it is closely related to the basic functioning of DNA in a way I don't understand. Anybody have a clue? --Fastfission 21:22, 3 August 2006 (UTC)[reply]
What they taught me in college is that there's actually a spectrum of dominance, from completely recessive to completely dominant and everything in between. The physical basis is simply the body's reaction to different amounts of protein. If you have two copies of an allele, you'll have about twice the resulting protein as if you have one copy. If the body needs the full amount for whatever function, then having only one copy will mess you up, and the disease-causing allele will be dominant. But if the body only needs a little bit, so that 1X or 2X the amount makes no difference, then the disease-causing allele will be recessive (you only need one copy of the good allele, meaning to be sick you need both copies of the bad allele). There are examples, though I can't quote them off my head, of diseases where having one good copy and one bad copy will cause a disease, but having two bad copies will cause a more serious disease or even prevent the fetus from developing at all. The article you need is Dominance relationship, but I just now found that after writing this, so I hope I'm on-base. --Allen 21:40, 3 August 2006 (UTC)[reply]
An example would be sickle cell anemia, where one sickle cell gene causes mild symptoms, but also provides partial immunity to malaria. Two sickle cell genes, on the other hand, cause a serious and often fatal version of the disease. StuRat 05:30, 4 August 2006 (UTC)[reply]
I assume you understand that for most human genes, every person normally has two copies of each type of gene, one copy from each parent (see: diploid). Here is an analogy for a recessive disease: think about human vision. If you have damage to one eye, you can still see fairly well with just one functioning eye. For many genes, if the copy from one parent is defective, the biological function that is normally accomplished by that type of gene can be accomplished using just the one good copy from the other parent. In order to seriously disrupt the function of that type of gene, you need to have inherited mutated versions of the gene from each parent. For many dominant gene mutations, having one normal copy of the gene from one parent cannot compensate for the problem caused by having one copy of the mutant gene. Some proteins coded for by mutant genes have been shown to function at the molecular level as "dominant negative" regulators of cell processes. In some cases, even a very small amount of altered protein from a mutant gene can have dominate effects over the normal protein. Often this is the case because many proteins normally exist in an "inactive" conformation. Such proteins normally do nothing inside cells until something special happens to activate them and as soon as the special condition is over, the protein goes back to being inactive. In many cases, dominant mutations in the genes for such proteins result in a version of the protein that is always on. This over-activity can cause a disease condition, even if half of the proteins of this type are normal (produced by the non-mutated copy of the gene. Analogy: think of fire sprinklers. If 50% of the sprinkler heads in a building had a defect that made them activate at room temperature, that building would have a problem. Even if only 1% of the sprinkler heads had this defect, most building owners would object. Dominant mutations are often of this type....the mutant gene codes for a protein that causes trouble. --JWSchmidt 22:18, 3 August 2006 (UTC)[reply]
Those are interesting and good descriptions, thanks. It's a bit more complicated than the classical genetics approach usually makes it out to be. --Fastfission 15:19, 4 August 2006 (UTC)[reply]
Bromine and its effect on swimsuits....
Hello....I swim several times a week for fitness and have noticed that I need a new swimsuit about every three to four months...sometimes I swim in a pool with bromine instead of chlorine...is bromine more caustic to swimsuit material than chlorine??? Just curious...thank you for your time...Jane----
According to this site bromine is less caustic than chlorine and "will not fade bathing suits or yellow blonde hair". It would appear chlorine is used for economic reasons rather than functional ones. Perhaps you should swim more regularly in the bromine treated pool and see if your swimsuit degrades at the same rate. Rockpocket 00:07, 4 August 2006 (UTC)[reply]
(after edit conflict) As an isolated element, Bromine is actually less chemically active than Chlorine and, based on a little research, the bromine compounds commonly used in swimming pools appear to be less damaging to hair, skin, and bathing suits than chlorine. Bromine is often the sanitizer of choice in spas and hot tubs as it is more resistant to very hot water. --Nebular110 00:15, 4 August 2006 (UTC)[reply]
hormones
Please explain the origin and function of gherin, i.e. what stimulates its release, what tissues make it, and what tissues are targets.
First, please explain the function of homework (this sounds like homework to me). Next, try searching for gherin and hormone in your favorite search engine. If you have questions needing to clarify anything you find, feel free to come back and ask them. digfarenough (talk) 23:06, 3 August 2006 (UTC)[reply]
what is gastro enteritis??
i hav tried looking it up heaps of times but there isnt anything.
i know that it is something that can happen if you are poisoned but i want to know wat it acctually is. for ex.
vomitting, dizzynous, etc.
any help would be greatly appresiated
--Sammie hero 23:08, 3 August 2006 (UTC)[reply]
Does the page on gastroenteritis not help? (Perhaps your extra space or hyphen in the word is making it harder to find information). digfarenough (talk) 23:09, 3 August 2006 (UTC)[reply]
A question to Doctors.regarding my strainge chest pain.
All respected concerned health exeperts, would you please guide me the course of action I should take to takle my strainge pain which I am feeling for the last 4 to 5 days .I call it strainge as I AM QUITE NORMAL though at 66 of age my day to day activities are normal and Iam not experincing any kind of simptums other than this pain on the chest at right breast region.Pain is not consistant all through the day,I feel it when I sneege and or when I cough occasionally.If I sqeese the muscle on the breast Idont feel the pain but when I PRESS the right brest with my paw I feel the pain.Is it a impending heart problem ? Please adise me whether to ignore it as it might subside after few days or should I consult compintant Doctor.Iam male quite healthy at 66 of age except for slight hiper tension with reading 155 -86. I am vegitarian non smoker and active all through the day. Thank you yours loving s.k.pujar
There are many causes of chest pain. You should definitely see a doctor so that they can diagnose it. No one is going to be able to diagnose such a complicated thing well based on an online description, except to say, "It might be serious, go get it checked out." --Fastfission 03:11, 4 August 2006 (UTC)[reply]
You ask us Reference Desk editors to advise you whether to ignore your pain. Well, I advise you NOT TO IGNORE IT because we cannot give appropriate medical advice. A physician examining you can. Please do not hesitate to visit a doctor -- immediately if possible. --Ginkgo100talk · contribs · e@ 03:22, 4 August 2006 (UTC)[reply]
Of all of the chest pains that are seen, chest pain which is on the right side and you can reproduce by pressing the chest wall is least likely to be related to your heart. Especially after five days of constant pain without other symptoms. However, just because it might not be cardiac doesn't mean that it can't be something else just as bad. Please, go get it checked out as soon as possible! InvictaHOG 03:26, 4 August 2006 (UTC)[reply]
I agree. See a doctor immediately. StuRat 05:18, 4 August 2006 (UTC)[reply]
Et tu, StuRat? DirkvdM 07:27, 4 August 2006 (UTC)[reply]
"The fault is not within our stars, but within our editors." StuRat 06:57, 5 August 2006 (UTC)[reply]
car cell phone charger
Do car cell phone chargers convert dc from the car to ac which the phone can charge on?
Is it the reverse of one of those big, heavy wall adapters?
You're assuming those wall-adapter chargers are supplying AC... DMacks 04:04, 4 August 2006 (UTC)[reply]
All cell phones charge on DC. The wall adapters convert AC to DC; the car adapters convert DC to a lower voltage DC (the car voltage is ~28VDC, while most phones charge at less than 5VDC). However, the DC to DC converter can do it by first converting to a high-frequency AC and then back to DC (and, in the same way, the wall adapters can convert AC to DC to high-frequency AC to DC; this is usually done in the smaller wall adapters, while the big heavy ones use a large transformer and a direct AC to DC conversion). So, your car cell phone charger might be in fact converting to AC (but only as an intermediate step). --cesarb 16:46, 4 August 2006 (UTC)[reply]
28VDC? My car's voltage is around 14V when running. —Bradley 17:21, 4 August 2006 (UTC)[reply]
Car batteries are intended to supply around 12 volts. Most cars supply this voltage. 48v 18:13, 4 August 2006 (UTC)[reply]
(edit conflict) Looks like I confused the voltages. Indeed, cars use 12VDC nominal, not 24VDC nominal. --cesarb 18:16, 4 August 2006 (UTC)[reply]
A friend of mine bought one of these, plugged it on one end into the car and on the other end into his regular wall cell phone charger. Is this wasteful/silly?
While this solution will work, yes. It is both wasteful and silly. The power which the car privides is very near the voltage which the phone needs to charge, the car chargers provide only a charging circuit and a voltage regulator. Instead he/she is using an inefficient 'inverter' to try to simulate AC residential power. And then using a moderately efficient chargere to convert that voltage (110-120) back to what the phone needs (5-10.) Buying a car charger would be cheaper, simpler, and better for the car battery. 48v 04:44, 6 August 2006 (UTC)[reply]
Hearing pianos over the phone
Why can't you hear pianos clearly over cellphones? This problem doesn't appear to exist with other instruments, the guitar for example. Any ideas? Please answer on my talk page. Thanks for your help! MarkBuckles (talk) 04:49, 4 August 2006 (UTC)[reply]
I would guess it's the small frequency range on each piano note. They may fall into "frequency holes", which are omitted to fit more conversations into a given bandwidth in a highly compressed cell phone transmission. StuRat 05:14, 4 August 2006 (UTC)[reply]
Piano notes have a small frequency range? Most keys hit more than one string and they're in an encasing that gives them ample opportunity to give off all possible vibrations, resulting in many overtones. On top of that, the piano is the instrument with the widest tone-range. A telephone line is, however, restricted to the frequencies that are important for speech. Piano key frequencies range from 27 to over 4000 Hz. The range of the guitar is from 82 to less than 1000 Hz (way up on the neck). I can't find what frequencies are transmitted over a telephone (searching for 'telephone frequencies' only leads to radio frequencies the connections use, which is something different). But it may be in the hundreds of Hz (althogh I thought it was around 1000 Hz), which would explain why you can't hear notes above that. You could still hear lower notes, though, through the overtones. So same answer, just the other way around. :) DirkvdM 07:59, 4 August 2006 (UTC).[reply]
The standard sampling rate for telephony is 8000Hz, which due to the Nyquist–Shannon theorem means the highest frequency transmitted is 4000Hz (see Nyquist rate). If you use 8 bits per sample, you have a bitrate of exactly 64000 bit/s, which uses too much radio bandwidth (on POTS, however, you have almost the full 64000bps rate). To reduce the bandwidth, the sound is compressed using special speech codecs (which can vary from 13kbit/s to as low as 4.75 kbit/s). Of course, to reduce the data rate that much, some information is lost; these codecs are optimized to retain more information related to the human voice (and, sometimes out-of-band, DTMF tones), and less information related to everything else (including background noise and music; comfort noise can also be generated at the receiver). It's not a specific frequency being dropped (i.e. there are no "frequency holes"); these codecs actually try to predict the waveform using mathematical models (tuned to the human voice), and encode the resulting coefficients and residuals. --cesarb 16:22, 4 August 2006 (UTC)[reply]
So the explanation would be that (somehow) a guitar behaves more like a human voice? Might be interresting to test how different instruments and different notes on those instruments come across on a telephone. i just don't know who I might call who would be equally interrested in such an experiment. Ah come on, do I really have no interresting friends? Is that why I spend so much time here? Or is that the other way around? ... I will now just go and sit in a corner and feel sorry for myself. DirkvdM 19:04, 4 August 2006 (UTC)[reply]
You could try to find implementations of these codecs which run on a normal PC, convert a small sample of music (losslessly compressed if possible) to the codec and back to a normal wave file, and then do a blind a/b test (we seem to be missing either an article or a redirect here; any takers?). --cesarb 23:43, 4 August 2006 (UTC)[reply]
Part of the characterist sound of a piano is not the sustained tone alone, composed of a fundamental plus harmonics, but the initial attack as the key is struck. The 300 or 400 Hz high frequency cutoff in modern phones may allow the fundamental tones to pass, but block some of the harmonics. It may also cut off some of the envelope of the initial attack, which is somewhat percussive and may include more high frequencies. Edison 18:24, 5 August 2006 (UTC)[reply]
There's a high frequency cutoff at just a few hundred Hz? That explains a lot. If you're sure about this, could you add it to the telephone article? DirkvdM 08:50, 6 August 2006 (UTC)[reply]
No way it could be that low; plain lowpassing at 500 Hz gives an awful muffled sound with all sibilants unintelligible. --Kjoonlee 09:08, 6 August 2006 (UTC)[reply]
I assume Edison meant 4000 Hz, as cesarb mentioned above. --Kjoonlee 09:09, 6 August 2006 (UTC)[reply]
exhausting a portable air conditioner through the chimney flue
Is it possible to exhaust a portable air conditioner's exhaust through the chimney flue instead of the window? Would I be able to force the air out with a fan (after closing a furnace exhust vent) if the atmospheric pressure is too great?
Maybe. As you seem to already know, the exhaust from the A/C unit won't be sufficient in volume or heat to create a proper draft up the chimney. A fan at the chimney alone probably wouldn't be sufficient, either, as this would create a negative pressure in the house sucking the exhaust back down the chimney. If a second fan were added to force air into the house, this would probably do the trick. However, this would be blowing in hot air from outside which is going to fight the A/C unit. I suppose it still might cool the room containing the A/C unit, but the room in which the air enters the house would get hot. So, I recommend against this approach. Now, if you could rig up a long tube and route it up the chimney, and force the exhaust up the tube, that might work a lot better. A dryer vent hose might work. StuRat 05:08, 4 August 2006 (UTC)[reply]
Our toilet has such a ventilation shaft with a fan, so it should work. Air will easily get sucked in through all sorts of holes and chinks (is that the right word?) in the house. If it's hot and you create a lot of current that would be like having a fan for the whole house, so you can leave the ac off. It would have to be pretty strong, though. But then you wouldn't need the ac, which is begging the question. I suppose you'd better ignore this advise. DirkvdM 08:11, 4 August 2006 (UTC)[reply]
Of course, indoor Cannabis growers do this all the time. AllanHainey 14:46, 4 August 2006 (UTC)[reply]
I don't. I like the smell. DirkvdM 19:06, 4 August 2006 (UTC)[reply]
Every portable AC that I've had also drips water out the back. If you try to put it in a chimney opening, you'll end up with a puddle in your chimney. --Kainaw(talk) 14:48, 4 August 2006 (UTC)[reply]
The air conditioner doesn't really exhaust air; it exhausts heat. The fan on the hot side of an air conditioner is only there to increase the heat transfer not get rid of air. So, a single fan in the chimney would do very little as you need to be pulling cooler air into the condensing coils of the air conditioner. StuRat's idea of a tube within the chimney (a tube within a tube, effectively) to pull down cooler air and push out hotter air would be best. Modern wood-burning stoves do this. They pull the combustion air down the outside of a double-walled stack, burn the wood, and the combustion gases are vented up the middle of the stack. This prevents the stove from stealing your warm air in the house for combustion and pushing it out the chimney. In this case, you don't want the air conditioner stealing your cooled air to cool the condensor coil and push it out the chimney. —Bradley 17:16, 4 August 2006 (UTC)[reply]
Meteorite
Is it possible that a meteorite could hit the earth at an angle that would forever increase the speed at which our planet rotates on its axis. Thanks.
Sure, but not by a lot. Something the size of what killed the dinosaurs could change the angular velocity of the Earth by up to about a few milliseconds per day. Dragons flight 05:29, 4 August 2006 (UTC)[reply]
Just consider classical physics questions of momentum--the metorite would have to have a combination of mass*velocity (useful to visualize as a vector) that was non-negligable to the mass*velocity vector of the earth in order to detectably alter the earth's vector. I'd be more worried about massive global extinctions over resetting my Timex if something that large were to come our way... -- Scientizzle 07:45, 4 August 2006 (UTC)[reply]
Let's fill this in. Earth's volume is 1012 km3. A really really big meteorite could be 10x10x10 km = 103 km3. Assuming the same mass per volume, that would mean the meteorite's mass is only one billionth of Earth's. Earth has a rotational velocity of 465 m/s at the equator. Compensating for the fact that not all mass is at the surface, let's say 100 m/s. If the meteorite had 1000 times that speed (100,000 m/s or 360,000 km/hr - an enormous speed) then that would only constitute 1 millionth of Earth's rotational momentum. Also, just a tiny fraction would go into a rotational change - most of the energy would be absorbed (on this scale the Earth is quite elastic) and of the remaining energy, most will change the Earth's direction (and thus its orbit), not it's rotation, depending on the angle at which it hits. And that change would also be minute. DirkvdM 08:26, 4 August 2006 (UTC)[reply]
Let's just make some assumptions to simplify things here. a) Assume all the momentum transfered from the meteorite to the Earth is transfered to the Earth's angular momentum about the centre of mass (it hits a cliff). b) Assume the collision is perfectly elastic. The angular momentum of a sphere is given by (the moment of inertia) multiplied by the angular velocity. For the Earth this works (I think) at about 2.5x1057. I'll leave you to come up with momenta for meteorites. As DirkvdM says, in reality most of the momentum would be affecting the angular momentum of Earth's centre of mass (it's orbit), but as this is so much higher than the angular momentum about the centre of mass I would guess that (depending on the angle of collision) there would be a greater effect on the Earth's rotation (about its axis) than on its orbit.
What about a really really really big meteorite... But then again you might prefer to call a Mars-sized rock a "planetary collision" rather than a "meteorite hit". Weregerbil 09:46, 4 August 2006 (UTC)[reply]
One possible explanation for how the moon formed is as a result of a giant meteor collision with Earth. A meteor this size would likely have affected the rotation rate of the Earth by a significant amount. StuRat 07:45, 5 August 2006 (UTC)[reply]
Based on what StuRat said I'm not sure if it actually affected it's rotation but the metorite which hit the earth actually put the earth on a rotation (thus giving us the seasons). However, i think it can be possible if a metorite that large hit the earth and was that large could affect it's rotation speed. Probably much like the Metorite Apophis
Some corrections are needed here. The seasons are caused by the Earth's tilt and revolution around the Sun, not by it's rotation. The rotation only causes day and night. Also, the Earth would have had an initial rotation, which comes from the rotation of the solar system. According to physics, as the diameter of a rotating object decreases, it spins faster to maintain a constant rotational momentum. Thus, as the Earth formed from a dust cloud, the rotation of the cloud would increase. I would think we could calculate the expected rotation rate of a planet based on it's size and distance from the Sun. Then, any deviation from the expected value would be from impacts since then (most of which might be tiny dust particles hitting the atmosphere). StuRat 17:46, 11 August 2006 (UTC)[reply]
Bullet
If I fired a bullet stright up into the air would it (technically) hit the ground at the same speed that it left the gun from. Assuming there is no wind etc.
If fired in a vacuum, however, it would. When dealing with speeds that don't approach the terminal velocity of the object in question, it's safe to say that upward release velocity will be essentially equal to downward falling velocity at the same height (with variations due to chaotic perturbations of the air and object, etc.). The nature of an atmosphere that provides non-negligable friction makes things slightly more complicated at higher velocities... -- Scientizzle 07:38, 4 August 2006 (UTC)[reply]
Don't try this at home. And if you do it outside, make sure to step aside. DirkvdM 08:30, 4 August 2006 (UTC)[reply]
See also MythBusters (season 3), Episode 50. It seems that if the bullet retains its spin, it will exceed its normal terminal velocity.--Shantavira 11:56, 4 August 2006 (UTC)[reply]
They also pointed out that the bullet would retain spin if it had any arc in the path. To keep it from spinning, you have to fire it straight up - which is nearly impossible to do. The gun, wind, spin of the Earth, and all will contribute to causing the bullet to go up at an angle, arc over (still spinning), and come back down.
Answering the question, though - no. It will not be at the same speed. Bullets do slow down as they pass through the air. Even though it will still be a lethal speed, it will be slower than the muzzle velocity. --Kainaw(talk) 13:30, 4 August 2006 (UTC)[reply]
The only real factor that would cause the bullet to have a different speed would be air resistance. Firing the gun from the surface of the Earth, it would be nearly impossible to get it to move in anything other than an arc due to the coriolis force caused by the Earth's rotation (which wouldn't be very much unless it was a very very powerful gun). This shouldn't effect its speed when it lands though as it wont travel any further coming down than it would going up. It's all about conservation of energy. Mathematically, the velocity with which it would hit the ground would look something like:½ where v is the final velocity, u is the initial velocity and Du and Dd are the energy losses on the ascent and decent respectively.
If he stood on the equator of the moon, facing in the direction of the moon's rotation and fired his pistol straight up (so no air resistance) at 300 m/s, would it go straight up and come straight down and (theoretically) land in the barrel of the pistol? The gun rotates with the moon surface at 4.63 m/s in a slightly curved path. The bullet along with its decelerating vertical velocity has an initial horizontal velocity of 4.63 m/s. At the moon's gravity of 1.622 m/sec squared, the bullet would rise for 185 seconds to its highest point. It would fall for another 185 seconds. If the shooter could see it, it would appear to move along the equator retrograde to the direction of rotation, and would land to the retrograde side of the gun. Not good enough at orbital mechanics to say exactly how far behind, but I am curious. Then assume he stood on the north pole of the moon and repeated the experiment. The coriolis effect due to the moon's rotation should be absent, but what effect would the orbital velocity of the moon about the earth and about the sun have?Edison 19:35, 5 August 2006 (UTC)[reply]
If he stood on the equator and fired the gun the bullet would land in front of him (doing a quick calculation) as the coriolis force causing the bullet to land in front of the firing point would have a greater effect than the rotation of the Moon causing the bullet to land behind the gun. Taking the Coriolis force as F = 2mΩv you can calculate that the distance moved in the direction of rotation is (4Ωu²)/g and the (apparant) distance moved in the opposite direction is (2uΩ)/g you can see that it will always move further in the direction of rotation. Standing on one of the poles, the effects of the Moon orbiting the Earth and the Earth orbiting the Sun would stop the bullet landing back down the barrel of the gun, but they shouldn't have a great effect (if you don't fire the bullet too high).
Energy consumption per country
We've got lists on just about anything, but I can't find a list showing the energy consumption per capita per country. All I can find is Image:Energyconsumption.jpg and Image:Energy per capita.png, but those don't show what I am looking for and only give vague indications. The latter has a list it's based on plus a source, but before I make that into an article I want to be sure there isn't already such a list (in a less obvious place perhaps) and also that I can use (and re-arrage) the data (no copyright violation). DirkvdM 08:50, 4 August 2006 (UTC)[reply]
When I worked in energy conservation 30 years ago, we we able to find figures for the "quads" of total energy used by the US and other countries. It should be easier now with the internet, but maybe you should visit a good sized library and have the librarian direct you to reference books on energy. We had a very small proportion of the earth's population and used a very large portion of the energy. Have things changed much? I don't think so, except that there are decreasing reserves of oil and increasing demand in developing nations. Don't forget to combine all sources of energy, and to allocate electricity to end users.Edison 19:40, 5 August 2006 (UTC)[reply]
Birds in Slovenia
Why are apparently very few birds in Slovenia. On a holiday in the region of Lake Bohinj, it was noticed that there was no dawn chorus, and few visible birds. Why is this? Thanks, --217.42.132.207 09:38, 4 August 2006 (UTC)[reply]
I believe this is because people take pot-shots at them for sport. It's much the same in many parts of eastern and southern Europe. One side effect is that butterflies etc flourish in places like this.--Shantavira 11:53, 4 August 2006 (UTC)[reply]
The same thing happens in Italy, people shoot them for food & sport when they migrate over & large numbers don't make it. There was a BBC Radio 4 programme on several months ago about this and the steps being taken to try to preserve the birds, such as legislation & bird reserves. I don't think that there has been a great deal of success in stopping the hunters. AllanHainey 14:28, 4 August 2006 (UTC)[reply]
At this point, which standard seems more likely to be adopted as the primary for consumers and studios?
I can't remember which way round it is, but one is supported by Apple and the other by Microsoft. I'd plumb for the one supported by Apple.
Really, we don't know. It is whatever hits The Tipping Point first. They both have their pros and cons. Sony is supporting Blu-Ray all the way, they already are putting out movies in DVD and Blu-Ray. If you just looked at the names, and they were the same thing, you would pick Blu-Ray. I've found I personally, and most people, like technology names to be less abstract. They prefer Mac OS Tiger, or Lisa over AOL version 10.2.3, or Microsoft XP SP3. — [Mac Davis] (talk)
I am holding out until Blu-Ray 2.0, then, just to be contrary!
Weird really. The whole point of the free market system and competing companies and technologies is that the consumers pick the ones they like so those manufacturers get an impulse to make more such products. Sounds good in theory, but in this case consumers just sit around waiting for which one will become the standard and only then go out and buy it. Which is the wrong way around. The central problem here is that the determining factor is the standard. So that should really be set by others, after which the manufacturers can then all use this open (!) standard and start competing with actual products. The openness of the standard is essential for this (the free market really works on the wrong level here). So who should set that then? The old answer would have been governments. But the new answer is the Open Source community. Any ideas how this could be brought about? Is it just a matter of some people deciding to come up with a standard and then presenting that to manufacturers? Or do the consumers need to be convinced to go for that one? DirkvdM 19:24, 4 August 2006 (UTC)[reply]
I don't know much about blu-ray/hddvd, but isn't it a fundamental hardware difference? How can open-source communities handle this? If it were up to open-source folks, there would be 10 different versions of the new DVD instead of two.
As a consumer, I don't really care about blu-ray or hddvd, I just want to consume video at a reasonable quality and reasonable availableness for the cheapest price possible. I don't want to invest and put in some mighty dollar votes for the newest gadgets. It's a means to an end and that's all.
The link you want is dollar voting. Make sure to also check out the talk page.
The open source community would converge on one standard. If you're thinking about the many Linux distros, that's exactly what I mean. There are many distros, but they all use the same Linux core. That's the standard. Commercial companies (and others) can then use that for their own version, thus putting the competition where it should be, but leaving the standard alone. DirkvdM 09:09, 5 August 2006 (UTC)[reply]
All the latest talk is about how HD-DVD is better in quality, and the players are 1/2 the price of a bluray. Given Sony's hysterical failings of making new standards I seriously don't see how they will ever succeed --mboverload@ 00:45, 5 August 2006 (UTC)[reply]
It's possible - perhaps likely - that the true successor to DVDs will be neither Blu-Ray nor HD-DVD, but instead will be online file-transfer, scrapping physical media altogether. The current competition between Blu-Ray and HD will hold everything up a long time, where as digital files have many more benefits to producers (there's essentially no cost to creating a new file, and if they use something like BitTorrent to distribute it, bandwith costs fall on consumers). In short - the average person shouldn't bother getting either Blu-Ray and HD-DVD for a long time, if ever. zafiroblue05 | Talk 01:13, 5 August 2006 (UTC)[reply]
The dirty truth is that we might not even need a new format. A movie encoded with H.264 or similar advanced codec can fit an HD movie on a standard DVD. In fact I have The Transporter in 720p HD in only 4 gigs, while standard movie dvds are 8. --mboverload@ 07:08, 5 August 2006 (UTC)[reply]
I'd like a new format, I will always think it's a good idea to back up my hard-drive on a read-only disc. And my hard-drive can only get bigger in the future.
priming fuel pumps
i wonder why internal combustion engines use centrifugal pumps for the fuel delivery system.this gives us the headaches of priming the pumps.isnt it possible just to use a positive displacement pump for fuel delivery since it needs no priming?why prefering the centrifugal ones.moreover i understand centrifugal pumps do not develop good pressure heads. --Chiwaye 13:48, 4 August 2006 (UTC)Chiwaye,04/08/06[reply]
Rabbit Internal Organs
Hello,
Can someone tell me what the, relatively, large white organ rabbits have, I've ruled out the heart, stomach & I think kidneys but I've no idea what it is. It's white with a few red flecks or thin veins & its ovalish. Any ideas? AllanHainey 14:22, 4 August 2006 (UTC)[reply]
A bladder shall be whiter than a liver. --DLL 15:21, 4 August 2006 (UTC)[reply]
Rabbits have a pretty big cecum, which kind of matches your description. Is it a hollow organ? --Joelmills 15:43, 4 August 2006 (UTC)[reply]
I didn't cut it open to see but it may be the cecum. Sounds like either the Cecum or bladder. Thanks. AllanHainey 07:22, 7 August 2006 (UTC)[reply]
Do you have a picture? The location in the body may give us a clue. - Cybergoth 20:37, 14 August 2006 (UTC)[reply]
lichen damage to trees
Can lichen, growing on the bark of trees, damage the trees? I have a Wigelia (tree form)that is covered with lichen and one branch has become so soft that it has twisted and flopped to the ground.
Thanks to everyone for any help you can give me.
Antcathy
I wouldn't think so. Are you sure it's lichen ? StuRat 05:45, 6 August 2006 (UTC)[reply]
Oldest surviving sound recordings
Dear Wikipedia, I have tried searching on wikipedia for the oldest surviving sound recordings. Wikipedia provides a video file of the 'Roundhay Garden Scene' (1888); supposedly the oldest motion picture and also provides the oldest surviving photograph; 'View from the study window' (1826/27) by Niepce (I think that's how you spell his name). Wikipedia doesn't, however, seem to provide the world's oldest surviving sound recordings. I wrote to the British Library a while ago to find out more. Here is a copy of my question and their answer...
'Hello, my name's Russell and I may have an FAQ for you. I am interested in finding the world's oldest surviving sound recording.
I've heard that the first thing ever recored was Edison's 'Mary had a little lamb' from Decemeber 1877 but presumably this does not still exist.
I've tried searching on the Internet but can't seem to find out. If you could help I'd be grateful.
Reference Specialist (Sound Archive)
Humanities Reference Service
The British Library
96 Euston Road
London NW1 2DB
UK
Email: <e-mail removed to prevent spam>
Tel: +44 (0)20 7412 7676
I am no expert so I'm a little dubious about writing an article.
Thanks for doing the research! Sometimes on Wikipedia, in order to avoid knighting a thing as "the oldest X" where there is uncertainty or disagreement, we'll have a list of candidates. Then, if a candidate has an article, its claim to the title is linked to the list. Examples can be found in Category:World records. Perhaps it's time for an Oldest sound recording article, with a section for surviving recordings? Melchoir 20:08, 4 August 2006 (UTC)[reply]
I think you mean "dubbing", Melchoir. "Dubbed" can be applied to naming things generally, including making a man a knight. But "knighted" can only be used in that specific sense. JackofOz 12:34, 8 August 2006 (UTC)[reply]
I've heard Edison reciting Mary Had a Little Lamb, so some version of this recording still exists. StuRat 07:35, 5 August 2006 (UTC)[reply]
Someone was clever enough to make a backup? Ehm, ... on what? DirkvdM 09:12, 5 August 2006 (UTC)[reply]
Naw it was a hysterical re-enactment [9]MeltBanana 14:01, 5 August 2006 (UTC)[reply]
Edison's first phonograph was demonstrated to Scientific American editors in their offices and featured in the December 22, 1877 issue. IIRC, they included an illustration supposed to be an exact representation of a photo of the pattern of indentation in a tinfoil recording. That photograph or to a less accurate degree the illistration published would theoretically be one of the oldest "surviving" recordings. Actual foils are supposed to be too fragile to play, but a laser scan of one might produce reproducible sounds. A month or so later, tin the multi-volume collected papers of Edison, one of his assistants wrote he had made a plaster impression of a tinfoil recording which accurately reproduced all the indentations, and that he thought copies could be made from it. There is no sign this was done at the time, but maybe it is in a file somewhere. The phonautograph was pre-Edison and made accurate sound tracings on smoked glass cylinders. In fiction, they have been copied and played and perhaps could be in reality. There are urban legends of ancient pottery turned on a wheel and decorated with a wooden stylus having accidentally recorded sounds in the pottery shop, but the potter's hand would be far less effective than Edison's diaphragm connected to a recording stylus as a sound collector. Edison 19:59, 5 August 2006 (UTC)[reply]
about macbook (screen size 13.3 inches)
Have anyone seen the new mac book from apple which has a screen size of 13.3 inches? Is it big enough for anyone? Or is it just for students aged under 18? Is it good enough for adults?
One more thing I would like to know
What is the ideal distance between this monitor and our eyes while reading?
Thanks
I personally find that the bigger the screen, the better, because quality is not an issue with MacBook screens. I think if you're not a college kid without any money, you should get a bigger screen. I just checked the site, [10], and it says 13.3 is the only size for MacBooks!! I guess if you want a bigger screen you'll have to get a Pro. As for ideal monitor-eye distance, it is like the whole "don't sit too close to the tv Timmy, you'll hurt your eyes." You put your eyes where ever it is easiest for you to read. — [Mac Davis] (talk)
I think one good thing to check about a screen/computer combination is the refresh rate - try opening a window, then dragging it around the screen very quickly - if the motion looks choppy, you might want to look elsewhere. --Bmk 18:14, 4 August 2006 (UTC)[reply]
Just to get all pedantic on you, it's an LCD screen, so it doesn't have a refresh rate: it has a pixel response time. - Nunh-huh 04:32, 5 August 2006 (UTC)[reply]
Thanks for making time for that refreshing response. :-) StuRat 07:31, 5 August 2006 (UTC)[reply]
Screen size in laptops is usually directly correlated with weight. If you plan to carry this around with you a lot, a smaller size can make a lot of difference (I use a 12" iBook for this reason, it is large enough for everything I use it for). But if you have doubts you should go to an Apple retail store, where they will no doubt have many display units out that you can play with and see.--Fastfission 18:26, 4 August 2006 (UTC)[reply]
It really depends on what you're doing. When I'm programming, I find the 17-inch display on my laptop to be too small, but for reading ebooks, the 2.5-inch screen on my PDA is just fine. --67.185.172.158 04:23, 5 August 2006 (UTC)[reply]
Resolution is most of it for me, I had been using a 19xx by 16xx resolution for a while I think, I came back home, got on my old iMac, with a 1280x800 resolution, and everything seemed so fat. lol — [Mac Davis] (talk)
Freaky Plant Situation
Is it possible for two plants to get fused together or exchange genetic material just by being planted very close together? Because I have two plants, a green one and a purple one, and recently the greeen one's been getting streaks of purple in the leaves. The purple plant has vine-like stems and now the green plant is growing vines and it never did before. I have no idea what type of plants they are. It's sort of freaky, but I swear it's absolutely true. Is it possible the purple plant's a parasite or something?
--Anakata 22:05, 4 August 2006 (UTC)[reply]
Also, another thing is that one of the abnormal vines on the green plant is actually growing through one of its own leaves, i.e. it poked a hole through it.--Anakata 22:14, 4 August 2006 (UTC)[reply]
The Chimera thing could be the cause, but these strange purple streaks only started appearing very recently, like one month ago. Before that the plant was perfectly fine and green throughout. If it was a chimera, wouldn't it be like this from the start?--Anakata 23:02, 4 August 2006 (UTC)[reply]
Can you upload a photo? —Keenan Pepper 23:04, 4 August 2006 (UTC)[reply]
Are the two plants of the same species, and do the reproduce sexually (via stamen, pistols, and pollen) ? If so you may get a cross pollination between the two color phases. I've seen this in alyssum myself. StuRat 07:24, 5 August 2006 (UTC)[reply]
If the colouring is caused by some chemical, there need not be an exchange of genetic material, just picking up some of the other's juices. Just a guess DirkvdM 09:16, 5 August 2006 (UTC)[reply]
Reproductivity of results
What is meant by reproducibility of results in science? Why is this important in science?
Some time ago, I heard about a group of researchers at a university extracting a substance strongly resembling silk from pigs' ears, and using it to make a purse. However, I can't find anything about this besides retellings of the story, with various embellishments. Is there any truth to this, or is it another urban legend? --67.185.172.158 04:20, 5 August 2006 (UTC)[reply]
Tails of shrimp, stems of peperoncini, and peels of oranges and banannas
People often think I am some kind of weirdo because I eat the tails of shrimp, stems of peperoncini, and the peels of oranges.
I sortof understand from a taste/texture point of view - shrip tails are really crunchy and hard to eat, peperoncini stems are stringy, and orange/bananna peels are just bitter.
Are any of them bad for you, though? Is it really that weird to eat these things? It just comes from a family where, if you have food, you EAT it. --69.138.61.168 05:12, 5 August 2006 (UTC)[reply]
Nope. I've visited parts of the word where these things are considered delicacies - of course, they are prepared differently than what I imagine a typical Wikipedian would. --HappyCamper 05:15, 5 August 2006 (UTC)[reply]
One thing to watch out for is that orange peels may have pesticides and dyes in them that are not intended for human consumption. So, you'd better stick with organic oranges if you intend to eat the peels. StuRat 07:19, 5 August 2006 (UTC)[reply]
And in the tropics it is often advised to only eat peeled fruit (and to peel it yourself) to avoid diseases. Don't know which ones, though. DirkvdM 09:20, 5 August 2006 (UTC)[reply]
Obelix once complained of his belly after eating oysters. Asterix asked him "Don't you take off the shells ?" --DLL 17:19, 6 August 2006 (UTC)[reply]
i ned an urgent info
dear sir, i need an urgent info how to separate UREA and CREATININ from a water solution?
please get me the details in this regards as soon as poissible. thanks..
with regards,
budhaditya chattopadhyay,
bangalore, india
BE(medical electronics)
<email address removed>
depends on what purpose they need to be seperated for. if you just want to seperate them analytically, i'm sure RP-HPLC will do the trick. If you want to seperate them preperatively, it becomes more tricky. perhaps cation exchange chromatography? you could exploit the charge differences, i imagine creatinine picks up a positive charge at a higher pH than urea. from a quick look, it seems creatinine forms a complex with zinc chloride, you could have a go at that. Xcomradex 07:44, 5 August 2006 (UTC)[reply]
Windows Vista
I think I once saw a link to a program (on Wikipedia) that would configure an XP computer to take on the appearance of a Vista-driven one. Does such a program exist?--the ninth bright shinertalk 05:56, 5 August 2006 (UTC)[reply]
Maybe this helps? [11] --Abdull 10:06, 5 August 2006 (UTC)[reply]
possible infant diarrhea epidemic in Detroit's Harper Hospital in 1943
My infant brother died of diarrhea that year and the family story was that many babies died of it at Harper Hospital during the time of the 1943 race riots because they could not separate the well babies from the sick babies during the riot. I recall at one time years ago reading a newspaper clipping about it but cannot find any now. I am a retired reference librarian so I've looked pretty hard under subject headings pertaining to the (1)riots,(2)Harper's history and(3)medicine, but I know the databases are very different today.
Thank you.
--209.112.212.40 06:12, 5 August 2006 (UTC)[reply]
I don't have an answer, but would like to point out that diarrhea isn't a disease, but rather a symptom of many diseases, quite a few of which result from poor sanitation, especially drinking dirty water. It would be important to know the actual disease which caused the fatal diarrhea if you wanted to research it more thoroughly. Also note that simple rehydration therapy (drinking fluids somewhat similar in composition to Gatorade) can prevent death from diarrhea, so I would research whether this was done at that hospital at that time. StuRat 07:10, 5 August 2006 (UTC)[reply]
If I had to guess a disease that would cause an epidemic of diarrhea affecting infants in a hospital, I would tend to assume either cholera or amoebic dysentery. Our article on diarrhea discusses these and more. --ByeByeBaby 13:36, 7 August 2006 (UTC)[reply]
As a relative you should be able to get a copy of the death certificate which should list the exact cause. (in 1940s terminology.) Rmhermen 00:18, 9 August 2006 (UTC)[reply]
I've been quite disappointed with death certificates. They frequently just seem to take a guess at the cause, or just list a symptom. It probably just lists "diarrhea" as the cause of death, or maybe "dehydration". Considering that resources are allocated based on the fatality rates of various diseases, it doesn't seem right that death certs are so sloppy in listing the cause of death. StuRat 22:10, 9 August 2006 (UTC)[reply]
Chromatography
SIR,
I am not able to understand the basic concept of chromatography hence i am fasing problem to learn and understand it.
1) For, eg. " In chromatography , the sample is applied at one end of the porous support which holds the stationary phase and the mobile phase is made to flow over it". The various constituents in the sample gets seperated due to difference in their distribution behaviour.
Now, the stationary phase is the porous support or the sample which is applied? What it is ment by distribution behaviour?
2) The various chromatographic techniques can be classified depanding upon the forces of interacting phenomenon between the solute molecules and the stationary phase.
Now which is the solute molecule and whice is stationary phase, Can you give me any example.
3) Can you explain me the principle of gel- filtration chromatography in simple english.
I changed the formatting to make your questions easier to read. What are you quoting here? It's not the article Chromatography. Maybe you should start by reading that. —Keenan Pepper 06:32, 5 August 2006 (UTC)[reply]
The "simple English" WP has no Chromatography article. Imagine what concepts could be operated to deliver something readable for one only acquainted with simple words (but shall such words be enough when it comes to facing the study of a "problem".) There ought to be a ferryman and it should be the teacher : Why don't they get asked first ? --DLL 17:13, 6 August 2006 (UTC)[reply]
atomic physcis
which has higher energy the nuclear fusion or nuclear fission?
Fission and fusion are processes that convert energy from one form into another. It doesn't make sense to say they "have energy". Atomic nuclei have different amounts of energy, as shown in Image:AvgBindingEnergyPerNucleon.jpg, and that's what makes fission and fusion possible. —Keenan Pepper 07:14, 5 August 2006 (UTC)[reply]
Fusion generally releases more energy. This is what you should write down. — [Mac Davis] (talk)
...that is, fusion of a given mass generally releases more energy than fission of an identical mass. Fusion also requires much more energy to initiate. StuRat 20:32, 5 August 2006 (UTC)[reply]
Since when do we just tell people what to write down?? —Keenan Pepper 05:14, 6 August 2006 (UTC)[reply]
Beware that they don't write down you name too. The parents might sue you if the pupil gets convinced of obtaining extra help. --DLL 17:06, 6 August 2006 (UTC)[reply]
Well spotted. I'm pretty sure these are the same phenomenon. The articles need to be merged (anyone?). Anthelia is the plural, by the way, and duplicates anthelion.--Shantavira 15:30, 5 August 2006 (UTC)[reply]
go ahead and merge it abdull. be bold
Actually, sudden mergers can upset some people. It might be wiser to apply {{mergeto}} and {{mergefrom}} and see who rises to comment. Melchoir 17:05, 5 August 2006 (UTC)[reply]
It looks to me as though "anathelia" and "glory" should be merged, but "heiligenschein" is different (for example, it doesn't seem to have rainbow colors). --Trovatore 05:39, 6 August 2006 (UTC)[reply]
But the point is, I think it's a different phenomenon on the dewey grass, since you don't see rainbow bands of color, just white. --Trovatore 17:09, 6 August 2006 (UTC)[reply]
Yes, it's a different phenomenon altogether. If you follow one of the external links from heiligenschein you'll see that the explanation has to do with the drops of water focusing the sunlight on the blade of grass behind them, then acting as a lens from the point of view of the viewer. A glory, on the other hand, has to do with surface waves of light on the water drop itself. So please don't merge these; they seem to be quite distinct. --Trovatore 17:30, 6 August 2006 (UTC)[reply]
The other side of the Big Bank
After the Big Bang, why is it that the Universe is expanding in one general direction? If this is not the case, then what is on the other side of the initial point of the Big Bang?
In one general direction? It expands forward in time. If it expands backward in time from its starting point, I don't think we'd know. In most (all?) big bang scenarios, time started at the initial point and so nothing was before it because there was no time before it. digfarenough (talk) 16:53, 5 August 2006 (UTC)[reply]
In some branches of String Theory it is possible that there was a 'before the big bang'.
I think that Dparisi is under the impression that the universe is moving out into the left (or right). In reality, because the universe itself is expanding (not a bunch of things moving away into the universe), it makes no sense to say that it is expanding in a direction. Space is just getting bigger. —Daniel(‽) 17:39, 5 August 2006 (UTC)[reply]
One way to visualise this is as a balloon with dots on it. When you blow up the balloon, all the dots move away from each other. We observe (almost) all stars around us moving away from us, so the conclusion was that we must be part of an 'expanding balloon', ie the universe is expanding. Of course one flaw here is that you can see that the balloon is expanding in relation to its surroundings (the other option would be that everything else is getting smaller, which would be silly). But the universe is everything, so what do you measure its size against? Don't we have to assume that the size of the universe is fixed? (if it indeed is everything) DirkvdM 17:48, 5 August 2006 (UTC)[reply]
It is usual to say that all the galaxies in the Universe are moving away from us as opposed to most stars (although as all the stars in the Universe apart from the ones in our galaxy are moving away from us). The balloon analogy can be better expressed by affixing coins to the balloon (top represent galaxies) as these wont expand with the expansion of the balloon. The only real problem with the balloon analogy is that the curvature of a balloon is positive and the curvature of the Universe is zero. This analogy is useful for demonstrating that the big bang happened both everywhere and nowhere. We measure the size of the Universe from the inside by using standard candles to determine the rate of expansion (the Hubble Constant). Once we know this value the age of the Universe can be established then, by association, the size of the visible Universe. We do not know how big the Universe it is, but it is a fair bet that the visible Universe is not the whole Universe. I'm not sure why one would assume the size of the Universe is fixed. The Universe is expanding in either 4, 10, 11 or 26 dimensions; depending on which theory you take to be true.
Since at least one of those dimensions is time, what exactly does "expanding in the temporal direction" mean ? Getting older ? I guess I'm "expanding in a temporal direction", too, then (not to mention a couple of spatial dimensions). :-) StuRat 20:24, 5 August 2006 (UTC)[reply]
For one, the big bang is just a theory. Nothing can prove that it happened. Why would you assume that it is expanding? All things we observe in the universe are in an orbit around something. So it is possible that we , our galaxy, could be in orbit around something. This would be a large orbit that would be impossible for us to observe in our short life time. So we would assume that everything is moving away from us when it realy is not. For example, Haley's comet comes roughly every 80 years. For half of its trip it is moving away from us. The other half it is moving towards us. If this orbit was 1 million yeears insead of 80 it would be imposible for us to tell that it was in an orbit.
Using that logic you would expect about half of the galaxies to be moving towards us and half away, but almost everything is moving away. StuRat 05:35, 6 August 2006 (UTC)[reply]
If we could measure its trajectory precisely enough we could observe a certain curvature that corresponds with an orbit (would that be a hyperbola?). So the limiting factor is not time but precision. DirkvdM 09:17, 6 August 2006 (UTC)[reply]
Mind you, other galaxies are not just moving away from us, but accelerating away. Something that a little theory of mine predicted! See my talk page. The problem is that gravity should provide a countering force, ultimately causing the Universe to collapse on itself again (if there is enough matter in the Universe). But the opposite happens. My theory, however, actually uses gravity to explain this. If our galaxy is collapsing in on itself, we will be accelerating towards its centre, and thus away from other galaxies and silly us think that they are accelerating away from us. Once again we regard ourselves as the the unchanging centre of the Universe. When will we ever learn?
Still, there is the problem that local dynamics (within our galaxy) don't seem to fit in with this theory. Or do they? DirkvdM 09:12, 6 August 2006 (UTC)[reply]
All the glaxies are moving away from each other, not only away from us. Following the cosmological principle we certainly do not regard ourselves as the centre of the Universe. That gravity should be pulling everything together is correct, however there is a force driving everything apart (see cosmological constant). If DirkvdM's theory that the Universe is collapsing is correct, there would be evidence for this in changes in the cosmic microwave background. The collapsing Universe theory also doesn't explain why the further away galaxies are, the faster they are moving away from us. If this was caused by gravity the opposite should be true. It is also interesting to note that there are some theories suggesting that, over extremely large distances, gravity might be replusive.
Einstein called the cosmological constant the biggest mistake of his life. It has been re-introduced just to explain away the acceleration, but is not really based on anything, afaik. But my idea of falling towards some great attractor would mean that the further away something is, the faster it would accelerate away from us. That's a prediction I made (although at first I saw it as a flaw) before it was found to be true. That's a theoretician's wet dream and that's the reason I keep on persisting in it, despite the fact that I barely know what I'm talking about. :) DirkvdM 12:22, 7 August 2006 (UTC)[reply]
If all gallaxies are moving away from some center point then there should be some other gallaxies moving at the same speed in the same direction as us.
The universe is a four dimentional object and so no adequate explanation can be given to explain its shape or structure to someone who cannot percieve the fourth dimention. It has no centre point, Bill Bryson likened this to taking a person from a universe where there are only 2 dimentions to a sphere, the would find it incomprehendable that they could walk all round it and find no edges, and as such we cannot comprehend how we can travel indefeinitely in any direction at an infinite speed and find no edge, there is no edge that we can comprehend. If you travelled in a straight line for long enough, you would eventually return to your starting point, such is the shape of the universe. As a result there is no centre point. Galaxies are all moving apart. But not from a point that we can comprhend. PhilcTECI 00:49, 7 August 2006 (UTC)[reply]
If we travel long enough in one direction we will return to our starting point? That means that in reality everything is on a colision course. Which means that the universe is not expanding nor is the other galaxies moving father away from us.ĎÀČ
It is possible that if you travel far enough in one direction you will arrive back at your starting point, but it is not possible to test this theory.
Just imagine crossing the entire universe and then missing your starting point by 10 m. Then you'd have to start all over again. Ad infinitum. QED (I think). DirkvdM 08:08, 8 August 2006 (UTC)[reply]
Just to return to the original topic as shown in the title, on the other side of the Big Bank is probably the Big Mall, the Big Carpark, the Big Newsagent, the Big Lawyer's office and the Big Optometrist. :--) JackofOz 14:16, 9 August 2006 (UTC)[reply]
I'm a senior high school student doing (or will start doing) a kinetic study of the permanganate/oxalate reaction for my final grade 12 year. I have an idea of what I'm going to do and how I'm going about it, but I have a few questions about the experiment. The equation for the reaction is the following:
2 MnO4-(aq) + 5 C2O42-(aq) + 16 H+(aq) --> 2Mn2+(aq) + 10 CO2(aq) + 8 H2O (l)
1. The reaction is very often mentioned as autocatalytic, which I have no reason to doubt. The problem is that most sources do not explain why this is so. The closest to an answer I've seen is something to do with the manganous ion produced collides with manganese complexes and this speeds up the reaction, but even then I could be wrong since I saw this in one source that tried to explain it. Then that doesn't really help me either, even if its correct. Some clarity on that would be appreciated.
2. The reaction procedes in an acidic solution. Would the rate law look like this: rate = k[MnO4-]x[C2O42-]y or do I have to add the proton (like [H+]z) to the equation?
3. I've read some experiment writeups where sulfuric acid was added to the reaction. Does it have to do with the reaction needing to be acidified? Would it be required if I used say oxalic acid instead of sodium oxalate (although oxalic acid isn't very strong)? Another explanation I've found is that it destroys the permanganate and speeds up the reaction and otherwise this reaction would take too long. Any ideas?
Thanks in advance.--72.56.179.48 19:35, 5 August 2006 (UTC) Adam Friedman[reply]
If you look at the basic equation you have written, you will see that it requires, at least theoretically, for two negative ions to react together. This would indicate that the reaction has high activation energy. You must look at the way the two manganese-containing ions react together. Secondly, you cannot predict the rate equation by looking at the balanced chemical equation. Rate equations can only be worked out by a series of experiments, for example, varying the concentration of H+ ions. Thirdly, the reaction is a very heavy consumer of H+ ions. These can only be provided by a strong acid. The original ethanedioic acid is far to weak to do this.--G N Frykman 21:01, 5 August 2006 (UTC)[reply]
Thanks for the above. Regarding the interactions of the manganese ions, is there a relatively simple way to explain it? I mean the manganese ion in permangante is reduced the 2+ state, so it must collide/interact. But can someone offer some sort of explanation regarding the interaction of the manganese ions and how this contributes to the autocatalytic nature of the reaction? (Or perhaps offer a basic idea of an experiment I could do...)
I didn't want to give you all the answers at once! Manganate(VII) and manganese(II) ions react together in a reverse disproportionation reaction to produce manganese(III) ions. It is these which oxidise the ethandioate ions to carbon dioxide. You will see that, as opposed to two negative ions reacting together, we now have a positive ion and a negative ion reacting. This can't happen, of course, until some manganese(II) ions have been produced by the slow reaction of the two negative ions. There is a hint of an experiment that you could do on the page autocatalysis.--G N Frykman 09:11, 6 August 2006 (UTC)[reply]
Yes, its ok not to want to give me all the answers all at once. Now that it was brought to my attention, I remember seeing in a journal article I read what is presumed to happen in the reaction in terms of how the maganese ions are reduced. They had three equations, and one of them was something like the following: Mn (VII) + Mn (II) → Mn (III) + Mn (VI). Then it says that the 3+ species is destroyed in a reaction with the oxalate species, actually now I that I think of it, like you mentioned. So I offer my thanks. I will next check the autocatalysis page. Again, thanks. --72.56.179.48 19:06, 6 August 2006 (UTC)[reply]
electromagnetic fields and radiation pressure
What is the difference between the lorentz force exerted by electrostatic and electromagnetic fields and the raditation pressure of electromagnetic radiation pressure. Secondly I saw an article in the 70s where small glass balls were levitated by electromagnetic radiation pressure, what is the largest and heaviest object moved by radiation pressure to date?
Curiosgeorge
It's worth reading the articles The most important difference between them is that the Lorentz Force only acts on charged particles; radiation pressure can be exerted on anything. The Lorentz force will also make charged particles move along curves, rather than straight lines. I'm afraid I don't know what the most massive objects moved by radiation pressure (in an experimental setting) are, but using radiation pressure to propel spacecraft is an active area of research.
The Lorentz force is the force that electromagnetic fields exert on charge particles. "Radiation pressure" is an interesting macroscopic example of the Lorentz force, but nonetheless they are really the same phenomenon. Both the lorentz force and radiation pressure only affect charged particles. Luckily, most matter is made of charge particles - protons and electrons. You might be interested in the Yarkovsky effect, which is an interesting example of the momentum of radiation affecting astronomical bodies in an unusual way. --Bmk 01:57, 6 August 2006 (UTC)[reply]
The radiation pressure exerted on an area, A, is given by (dp/dt)/A (where p is momentum). This does not involve any charges. It's an application of conservation of momentum.
There can be no radiation pressure without charges. All atomic matter consists of charges - electrons and protons. The only way for radiation to exert a pressure on a solid is if the solid contains charges; the electromagnetic field only interacts with charged particles. --198.125.178.207 18:47, 7 August 2006 (UTC)[reply]
That's not right, light carries momentum and when it is absorbed or reflected by an object, it transfers that momentum to the object. Light even though it does not have mass, has energy, and therefore can transfer momentum. This is an often overlooked effect of relativity. Dan 15:15, 10 August 2006 (UTC)[reply]
Vinegar reacts with hairspray to form a solid
A strange elastic white porous soild formed when I poured vinegar into a hairspary formula (40% alcohol) at room temperature and standard pressure. I smell the ethyl acetate, but that doesn't explain the solid. Can someone tell me what happened?
Do the ingredients of the hairspray list something like sodium benzoate? You have probably precipitated the insoluble acid (eg benzoic acid) of a soluble salt by lowering the pH.--G N Frykman 20:52, 5 August 2006 (UTC)[reply]
I once had to inject small amounts of benzoic acid into rubber-stoppered vials via a small guage needle and syringe. I can attest to the fact that benzoic acid is indeed very stringy and very sticky. Indeed, I'm pretty sure I never was able to get it in, and had to pick another chemical.Tuckerekcut 23:52, 5 August 2006 (UTC)[reply]
Nitpick: you can't pour anything into a formula because that's something abstract. Referring to the mix in the canister as a 'formula' is commercial blah. DirkvdM 09:27, 6 August 2006 (UTC)[reply]
Counter-nitpick: Any mother or half-interested father knows that what goes into a baby's bottle is usually called a 'formula'. Scientists are humans too (mostly). :--) JackofOz 01:32, 7 August 2006 (UTC)[reply]
I think any combination of chemicals can be called a formula. — [Mac Davis] (talk)
Well formulated. DirkvdM 08:08, 8 August 2006 (UTC)[reply]
Nice, a precipitation. --Proficient 04:29, 9 August 2006 (UTC)[reply]
Intercalating agents and you
I'm a labworker and during my work I get into contact with many nasty substances like ethidium bromide and DAPI. I tend to handle these substances (even in heavily diluted form) as if they were death incarnate. Sadly I'm also an incredible clutz and did get some DAPI on me and possibly in me. Of course I freaked out like no tomorrow especially because there is so very little known about the substance at hand. There are however quite a few other substances like this like Benzopyrene and Alfatoxin both of which, if I can believe the wikipedia articles, occur in my toast with peanutbutter (all be it in small doses).
Yet both these substances are flagged as highly carcinogenic (just like ethidium bromide and DAPI). So why aren't we dying of cancer left and right. Given the world we live in, with it's smoke, bbq's and crispy brown baked bacon, we should be accumalating this crud in our system at a staggering rate. So what gives? Am I missing something here? Can the body " deal " with these molecules shunting themselves between our precious base pairs thus causing happy frame shift mutations and the like? - Pascal
First, are you sure they accumulate instead of passing through the system ? Second, perhaps the dosage is insufficient to cause a problem. Third, perhaps it's not in a harmful form (for example, elemental mercury is far less dangerous than methyl mercury). StuRat 21:43, 5 August 2006 (UTC)[reply]
Alas, I remember the first time I spilled EtBr on myself. I freaked out too, but my reaction was decidedly less pronounced the 100th time. I'm not sure what the wikipedia article says (perhaps I'll stop by later), but EtBr (as well as DAPI) is not carcinogenic per say, but mutagenic. Much like UV radiation and charred carbohydrates, it is advisable to limit exposure, but don't worry so much that it takes over your life. From what I have learned from working with some geneticists who were working on their degrees before Watson and Crick even published, use gloves whenever possible (nitrile gloves) and if you spill a little you spill a little. In situations where you are working with visible dilutions (solutions which are visibly colored by the stain, red for EtBr, or blue/green for DAPI) double glove, and walk don't run to the shower if you spill on yourself. Gels (even mildly colored ones) are usually not a big deal for contact exposure because not much chemical is available at the surface. Basically, freaking out about a spill isn't gonna help you much, and as long as you haven't succombed to any toxic effects, the mutagenic effects can't generally be reversed specifically after the fact. Really the best protection is to stay healthy with a good diet and plenty of excersize. The human body has a slew of cancer-peventing mechanisms, utilizing many levels of protection at different teirs of biology (i.e. promoters/demoters in genes all the way to cells that scavenge for budding neoplasms). In short, lots of stuff can cause cancer, but we have pretty good defences. The goal is limited exposure, not necessarily zero exposure.Tuckerekcut 23:48, 5 August 2006 (UTC)[reply]
Good points made above. I also work in a lab and agree that you have to accept some element of risk, but work to minimize it. The point i wanted to make is that we simply do not know what the mong term effects of working with substances like EtBr or DAPI is. It could well be that they are carcinogenic to humans even at a very limited exposure, but corrolating increased cancer rates with lab workers will be very difficult to do. A lot of chemicals we are exposed to are called carcinogenic, usually because in some study somewhere - after exposure to ridiculously high doses - mice were shown to have an increase in tumour development compared to controls. If you live in California you would be amazed at the things that, according to state law, must be explained to you that they could cause cancer.
Poor old Marie Curie found out that working with material we do not fully understand can have pretty nasty effects, that is why we treat lab chemicals with such care, probably more than we strictly need to, on the principle it is better safe than sorry (and also to stop litigation based on the due care an employer owes their workers). That said, risk is relative, if i were you i would worry looking left and right when crossing the road than about suffering from EtBr exposure. Rockpocket 03:44, 6 August 2006 (UTC)[reply]
Thanks for the replies guys. I had already talked to the institute's doctor and he had already assured me that I didn't have to much to worry about, but your words of wisdom are always welcome. Also thanks for the advice for wearing nitrile gloves. I used to wear those dinky medical examination gloves (standard in our institute) untill I found those nitrile gloves. The nitrile gloves fit me better, cover the wrist area well and offer better protection so I'm sticking with them. Though I won't be returning to the labs soon (It was an internship of mine) I feel better prepared now.
I heard in a documentary on the Chernobyl accident that exposure to moderate doses of radiation aren't as harmful as one might expect from the effects of higher doses and might actually even have a positive effect, almost like a vaccination, causing the body to counteract cancer even though the doses aren't high enough for it. But that is speculation. DirkvdM 09:44, 6 August 2006 (UTC)[reply]
One of the reason that medium levels of radiation are often safer than low levels of them is because of the way that radiation affects the cell. In a rather simplistic form: if one particle hits the cell, you get a mutation (and potentially cancer). If two hits the cell, the cell just dies. So there is supposedly a level in between low and high in which cancer is less likely, since most of the cells that would be cancerous would end up just getting killed instead of surviving from their exposure. Or something along these lines. There is a lot of uncertainty and debate on the question of low-level radiation, I should point out. --Fastfission 16:29, 9 August 2006 (UTC)[reply]
actually the phenomenon is well precendented. it thought it was called hysteresis, but the wiki article doesn't mention much about its relevance to biology. it might be another h-word. Xcomradex 11:13, 6 August 2006 (UTC)[reply]
Just to be clear, the reason for using nitrile gloves goes beyond mechanical resilience. Ethidium Bromide is able to migrate through latex barriers with little difficulty (a phenomenon not often observed because latex so effectively stops the primary solvent for EtBr, water); and based on its similar ability to cross cell membranes, DAPI is likely to be able to do this too. Thus nitrile gloves offer barrier protection from these stains while latex gloves do not. I'm not so sure about other materials, though.Tuckerekcut 23:18, 6 August 2006 (UTC)[reply]
Strangely enough everyone in the institute uses latex gloves for just about anything. This makes sense because heck I could only scrounge up 1 box of nitril gloves in the intire institute. I think the institute needs to adjust it's safety protocols. - Pascal
how a snowboarder turns around while on the air
As far as I am concerned, things need stable things to move. (Car-Road, Boat-sea). So how a snowboarder turns around in the air an astronout in space without touching anything else. if so which musles are more likely to be used while in the action?
Any relevant answer would be much appreciated...
You can change your direction in the sense of turning around by simply shifting your own weight around. You can't change the path you are on very radically though—i.e. if you were thrown to the left, you could just throw yourself to the right without some sort of friction involved. --Fastfission 23:29, 5 August 2006 (UTC)[reply]
When snowboarders go for a jump, they give themselves some angular momentum by pushing off in the right way. Since they are also moving quickly through the air standing on a large board, there is significant air resistance which they can use to turn themselves. --Bmk 02:00, 6 August 2006 (UTC)[reply]
If an astronaut can't push against anything, that means his centre of gravity can't move. But that doesn't mean he can't turn around his own axis. If he stretches out his arms and swings them both to the left, his body will rotate to the right. His arms will wrap around his body, thus accelerating the rotation, like a figure skater. This rotation will continue until he moves his arms back again. To come to a stop he would have to do the same in reverse. If he would just move his arms back along his body (not outstretched) the rotation would merely be diminished. I think. Even thought the reasoning sounds right, it still feel counterintuitive, so I understand your question. I have wondered the same thing about 'accelerating' on a swing. I still find it hard to reason how this would be possible, but the person on the swing is excerting energy and that has to go somewhere. DirkvdM 10:09, 6 August 2006 (UTC)[reply]
The astronaut would only continue spinning until his arms stopped moving, then he would stop spinning; conservation of momentum prohibits him (or her) from gaining angular momentum. Basically, he can swing his arms, and his body will rotate a certain amount, but it will not continue to rotate unless he rips off his arms and throws them across his spacecraft, which is strictly against NASA regulations. --Bmk 13:25, 6 August 2006 (UTC)[reply]
Citation needed ? --DLL 16:59, 6 August 2006 (UTC)[reply]
How would you explain being able to increase the amplitude on a swing without violating the conservation of momentum? DirkvdM 13:35, 7 August 2006 (UTC)[reply]
Interesting question - after thinking about it, i think the way a person is able to increase their energy while swinging is because they are connected to the swing set by the rope. Basically, when they are swinging, they can use their muscles to elevate their body by pulling on the rope, thus adding potential energy to the motion, which is converted to more kinetic energy when they stop pulling. Momentum is conserved in the earth-swinger system. Oh, and by the way, I should have cited conservation of angular momentum in my first comment. --18.239.6.57 15:02, 7 August 2006 (UTC)[reply]
The arguments of conservation of momentum (be it linear or angular) or energy and such take a step back, looking at the system as closed and saying nothing can enter or escape. You say the person on the swing converts energy stored in their body to create (angular) motion. Can't the astronaut do the same? Then again, I recognise that they couldn't create linear motion that way, so I'm still stuck on this level. But in detail, the trick is to give the impulse in one direction with outstretched arms and then moves the arms back along the body. I'm not sure they would keep on spinning (I suppose they wouldn't), but if they keep on repeating this, they could keep on turning. DirkvdM 08:20, 8 August 2006 (UTC)[reply]
Right - the trick with the swinger is the system in which angular momentum is conserved is the entire swingset-swinger system. In the case of the astronaut, there's only the astronaut - if he wishes to have some angular momentum, there are no other parts of the system to which he can impart the opposite angular momentum to maintain conservation (unless he's allowed to blow air). And the astronaut would not actually be able to keep on turning - his angle will be limited (this is all neglecting air resistance, which would allow him through use of aerodynamics to gain angular momentum). Try it on a good swiveling chair - one with very low turning resistance. You should be able to verify that without the help of the resistance on the chair bearings, you are not able to continue turning after you arms are maximally twisted and stop twisting. --Bmk 20:19, 8 August 2006 (UTC)[reply]
i was wondering that if i were to make plate mail armor what would be the best metal for the job, by best i mean strong yet light, but wont dent or hardly dent when hit, thank you.
I would actually use Kevlar. It would meet all your requirements except that it is not metal. Titanium is a good metal candidate but I do not think you would find metal that is light and wont dent easily. Skapur 04:28, 6 August 2006 (UTC)[reply]
Yeah, you probably don't want to mess with real armor. Those knights were crazy strong. If you actually want it to protect you, the article armor has some suggestions, one of which is apparently 15 times stronger than steel, and fairly comfortable. If you're going for a recreation, iron might be accurate, but something light like tin foil on cardboard is way more practical, especially if you live someplace hot. Black Carrot 06:31, 6 August 2006 (UTC)[reply]
Titanium would be the best, but it's very expensive. Kevlar is a better armour, but you can't make plate mail out of it. The Guy From Ipanema
Electrical
What is the name of the electrical component that converts "noisy" electricity (e.g., that produced by a power plant) into electricity that is "clean", suitable for use in appliances (e.g., air conditioners etc)? I know this is a bit vague, but I figure someone might know what I am talking about. BenC7 03:26, 6 August 2006 (UTC)[reply]
A power conditioner regulates voltage and reduces noise in a power signal so that it is suitable for sensitive computer or audio equipment. A series of transformers reduces the voltage from the power plant to the voltage which can be used in houses. Hope that answered your question. 48v 04:30, 6 August 2006 (UTC)[reply]
Actually a large power plant produces clean electricty to begin with. Small electric generators tend to be quite noisy and a power conditioner helps. Skapur 04:42, 6 August 2006 (UTC)[reply]
Yes. The power plant energy is fairly clean; however, by the time it is transmitted to end-users, there is noise and voltage variation which can be problematic to sensitive equipment. 48v 04:57, 6 August 2006 (UTC)[reply]
Perfect! Thanks. BenC7 10:21, 7 August 2006 (UTC)[reply]
trying to identify a mineral/rock
hi, i wanted to ask what this mineral is, it is a bit lighter than a cap eraser, and has a shiny silver-graphite look too it with maybe a hint of light blueish shade to it(barely visible), and has no other colors on it.
Well, it could be graphite, as you say, or mica, that's also shiny. It would help if you said where you found it, or uploaded a photo. —Keenan Pepper 05:12, 6 August 2006 (UTC)[reply]
Sounds a little like hematite, but hematite is pretty dense (I assume when you say it's lighter than a cap erasor, you mean it's less dense). --Bmk 13:29, 6 August 2006 (UTC)[reply]
trying to identify a mineral/rock 2
this is for the question right above me, it was biotite mica, thanks
Just so you know, you can (and should) put anything relating to a single query in the same section - you do that by clicking the little link marked 'Edit' on the far right of the section header. Confusing Manifestation 07:19, 6 August 2006 (UTC)[reply]
Oh, and you should always sign your posts on pages such as this with four tildes: ~~~~, which then becomes something like this: Confusing Manifestation 07:23, 6 August 2006 (UTC)[reply]
When you say that it manifests itself as something that might be confusing to newbies. :) DirkvdM 11:19, 6 August 2006 (UTC)[reply]
Cool, I guessed it! Glad to have helped. —Keenan Pepper 08:07, 6 August 2006 (UTC)[reply]
Hair fall problem
Hi All, Im having a very serious problem : my hair is falling cont. and it has become too weak,dry and unhealthy. Could anybody please suggest me an appropriate site where I can get some help, or advise me.
Shave your head. You don't say if you're male or female, but you could shave it in either case. Don't forget to put sunscreen on your scalp. —Keenan Pepper 08:06, 6 August 2006 (UTC)[reply]
Im a female in my early twenties, and there is no way im shaving my head.
Oh, sorry. In that case I'd say either try a new shampoo, or talk to your doctor or hairdresser. —Keenan Pepper 09:24, 6 August 2006 (UTC)[reply]
It's normal for hair to be falling continuously, so if the ammount of falling hair has not increased, then there's no problem. (However, it's easier to notice fallen hair if your hair's long, as women's hair can be.) --Kjoonlee 10:35, 6 August 2006 (UTC)[reply]
And men's hair, for that matter. No discrimination, please. :) DirkvdM 11:21, 6 August 2006 (UTC)[reply]
I used to lose a lot of hair, in the sense that I had a receding hairline (so actual loss). When I was in my late twenties I stopped using shampoo. At first I started losing even more hair, but luckily I persisted and after about a month there was a noticeable improvement. At the moment I'm in my fourties and still have a fair amount of hair (check out the photo on my user page (click on my signature), although that doesn't show the bold spot at the back). My brother lost about as much hair as I did, but he kept on using shampoo and by the time he was in his fourties he was almost bold (although that doesn't really prove anything, but it's an indication). I should also mention that I had already switched to baby shampoo, so you might try that first. Maybe it's enough to stop the hair loss. Also, at first your hair will get greasier because it's used to compensating for the shampoo. But after a while it will adapt (back to normal, really). Showering with water really is enough to keep your hair (and your body) clean. Soap is only necessary when you've been to the toilet. DirkvdM 11:14, 6 August 2006 (UTC)[reply]
While your answers are frequently "bold" (for their total lack of supporting evidence), the word to use here is "bald", meaning "devoid of hair". I will now revise the way I view you, from an ultra-liberal, pot smoking hippy...to a greasy haired, balding, ultra-liberal, pot smoking hippy. :-) StuRat 07:08, 7 August 2006 (UTC)[reply]
Not ultra. Never ultra. Pretty liberal yes (in the Dutch sense, which corresponds to what in the US is called libertarian, I believe), but with a sufficient amount of socialism thrown in for balance. And not greasy either. You haven't been paying attention again, have you? Read my post again. DirkvdM 13:42, 7 August 2006 (UTC)[reply]
I read what you said about it not being greasy any more, I just don't believe it. You just got used to it being greasy, similar to how smokers can't tell they stink of smoke, after they get used to it.StuRat 10:31, 8 August 2006 (UTC)[reply]
Thyroid problems, vitamin & mineral deficiencies and hormone changes can cause hair loss. The dry, shedding hair is definitely a symptom of hypothyroidism. The internet is great, but I'd suggest seeing your doctor.--Anchoress 11:34, 6 August 2006 (UTC)[reply]
You didn't specify if it's falling down and becomes straight or if it's falling out. In either case talking to a doctor and a hair dresser would be your best option. - Mgm|(talk) 20:52, 6 August 2006 (UTC)[reply]
Try a moisturizing conditioner after you shampoo. Also, avoid swimming in pools, as chlorine can have just the effect you described, and try not to use a blow dryer. Question: Are you on a low fat diet ? These can reduce the natural oils your hair follicles produce. If so, I suggest a "healthy fat" diet instead, where you avoid trans fats and animal fats (except fish), but get lots of vegetable oils. StuRat 07:15, 7 August 2006 (UTC)[reply]
Thanks all, it really helped me.
Already? In my case it took a month. DirkvdM 13:42, 7 August 2006 (UTC)[reply]
Answering StuRat, no im not on a low fat diet, and I thanked you guyz for your suggestions,it helped me understanding the problem more (for DirkvdM). Hoping to get more from you all, wondering if someone can suggest some health site where I can get help from experties.[who asked the question].
Soap is NEVER necessary (at least, not the kinds sold in stores). Sorbolene does a damn fine job, does not produce allergenic reactions, makes the shower a whole lot easier to clean, leaves no residue, and leaves the skin smelling naturally fresh and sexy in a way that soap cannot hope to emulate. I thoroughly recommend you ditch your soap supplies and get some sorbolene. It might cost a little more, but it's worth it. JackofOz 12:21, 8 August 2006 (UTC)[reply]
In an average male person of 70kg, how much of that is not fat or muscle - i.e., mass that can't be "modified", so to speak. I know that erythrocytes comprise about 3% of one's body weight, how about all organs, bones and so forth? Jack Daw 12:27, 6 August 2006 (UTC)[reply]
Your bones usually make up about 20% of your body weight.
Tissue energy demands
How much energy (in kcals) does the body use at rest? Or at mild to heavy work? Also, you always hear that muscle requires more energy than fat. How much more? Jack Daw 12:44, 6 August 2006 (UTC)[reply]
Right, that answers my first question. And the others? :) Jack Daw 18:32, 6 August 2006 (UTC)[reply]
I read on a weight training website that every pound of muscle you gain burns an extra 60 calories, but I don't know if that's accurate.--Anchoress 21:55, 6 August 2006 (UTC)[reply]
I can't believe I only read the first sentence! Were the questions there before? Mild to heavy work: It depends on what work you do. It is different with every person too. Muscle requires more energy because it consumes a lot more. You do more work with muscle than fat. Fat is more so stored energy, while muscles is more used to release energy. — [Mac Davis] (talk)
http://muller.lbl.gov/teaching/Physics10/PffP_textbook/Chapter01.htm search for "Human power";. HIgh expenditure, about 1 horsepower = 746 watts for brief moments, or about a 100 watts sustained. If you are an Olympic athlete maybe you can do a horsepower sustained. "you always hear that muscle requires more energy than fat." Please rephrase your question. --GangofOne 06:22, 7 August 2006 (UTC)[reply]
Let me quote Dieting: "Ideally, overweight people should seek to lose fat and preserve muscle, since muscle burns more calories than fat." It's the last part I'm wondering about; how many more calories? Jack Daw 15:13, 7 August 2006 (UTC)[reply]
Right, my question too. I have never heard that and it sounds like complete nonsense. The body burns fat to operate the muscles. Or do you mean that making and storing fat requires energy? Probably. But then I still don't understand the statement. The two can't be compared (at least not without more info). DirkvdM 13:54, 7 August 2006 (UTC)[reply]
What do you mean by 'nonsense'? There's no need for an attitude. Jack Daw 15:13, 7 August 2006 (UTC)[reply]
I have no attitude (ahem...), I just care about the truth. DirkvdM 08:26, 8 August 2006 (UTC)[reply]
Don't call people's questions "nonsense" then, that's completely uncalled for. Jack Daw 14:13, 8 August 2006 (UTC)[reply]
If you have 2 pounds of muscle and 2 pounds of fat, the fat will provide energy as well as using some small amount to maintain the fat cells, the muscle will use up energy every time you move as well as using some for the maintenance of the cells. Your 2 pounds of muscle uses more calories than your 2 pounds of fat. If you weigh a set amount, if more of it is muscle you'll use up more calories. Not nonsense. But I'd like to know how many more too. Skittle 19:27, 7 August 2006 (UTC)[reply]
Ok, so pretty much what I thought. It was just stated in an awkward fashion. DirkvdM 08:26, 8 August 2006 (UTC)[reply]
Bio-0 electricity volume and question
How much bio-electricty can be generated by the human body? I read from a work of a biochemist that works for the US government Dr Mayne R Coe that in theory one cubic inch of the human leg tissue can generate 400 000 volts at low amprage, but this is only at max output and if a high amprage reaction sparked it off. Is this true? What is the general amount present in the human body including neurochemical electricty?
Secondly Why is there no wikipedia page on "high voltage syndrome" the case where an individual generates more bio-electricity than normal with strange side effects? It is documented in medical journals such as "journal das debats" and in reports such as the ones from the ontario medical assosiation and mentioned in books such as "anomaloies and curiosities in medicine" and "abnormal hypnotic phenoemena"
Robin
Feel free to start the article yourself! It's your encylopedia too. However, I have to say I don't think there's much truth to this idea. Our somewhat dubious article bio-electricity could be of use. There are small macroscopic voltages from body part to body part, but they are on the order of millivolts. There is also a small but significant amount of energy in the electrical signals of neurons, but it also isn't much. Mainly the body stores energy in chemical form (which, if you really get down to it, is electrical energy anyways). You might be interested in the article voltage, also. --Bmk 13:56, 6 August 2006 (UTC)[reply]
I think that may be wrong, the brittanica encyclopedia claims http://www.britannica.com/eb/article-9079250 that each cell membrane has an electrical potential of around 50 millivolts, and there are millions of cellmembranes in operation in your body at a time.
Any comments?
Robin
Sure, many/most neurons, for instance, have a resting potential of around -70 mV (really it varies widely). It's caused by a separation of ions across the membrane. But when you open up an ion channel to let the membrane reach equilibrium, you're talking a very tiny amount of current that flows (I don't know an actual value offhand, but my guess is it's down in the nanoamp range). You'd be hard pressed to find an efficient way to actually use such a tiny amount of electricity, especially as you'd probably have to "tap" each cell individually. digfarenough (talk) 16:01, 6 August 2006 (UTC)[reply]
Thank you, but can anyone tell me exactly how many millivolts/ volts are in the human body on average, combinding the cell membranes, neurons firing etc the brain, limbs, nerves etc. the whole thing. How much coltage wise?
Robin
Well the root of your confusion may be a units problem! A volt can be transformed around quite a bit via electronics and chemistry. For example, see Ohm's law relating voltage and electric current What is really relevant is the electric power. Realistically, there is not much electrical power floating around (probably in the neighborhood of microwatts to milliwatts; i.e. hundreds of times smaller than the chemical or mechanical energy inside a biological organism). The form that this electrical energy takes may be ionizing a cell-membrane, which could be very small (maybe millivolts), or synaptic junctions, which could reach volts for very short time intervals. It's not very common to talk about the "total number of volts in the body" because you can't just add them all up as if they were grams. Voltage must always be measured between two points - you can conceptually think of it a bit like "distance" - you can't really have the "total number of distance" either. But the end result is that not much electrical energy is floating around at any given time, no matter how you slice it. Nimur 12:46, 7 August 2006 (UTC)[reply]
History of Household Appliances
I am trying to find information about when household appliances such as hot water heaters and refrigerators were first manufactured and sold in the US. Any assistance would be greatly appreciated.
joc_trebor
According to our article about refrigeration, Alexander Twining was the first to introduced a commercial refrigeration device to the US in 1856. --Bmk 14:03, 6 August 2006 (UTC)[reply]
As for hot water heaters, they were preceded by cold water heaters. --DLL 16:49, 6 August 2006 (UTC)[reply]
A google search on "technology timeline" gives a very good list of resources. You could also look at articles for specific appliances in wikipedia, or google. Please "search first". 48v 17:18, 6 August 2006 (UTC)[reply]
I'll skip the 'hot water heater' (DLL already covered that) and move on to the next question. Do you mean 'electrical'? Heating water over a fire has been done since prehistoric times. And refrigeration was done in the middle ages (and possibly before that, but the US didn't exist then) by storing ice in deep pits, where it stayed frozen all summer long. Simpler cooling methods use evaporation, just like electrical refrigerators, except that evaporating water is a lot simpler - just wet a towel and put it on whatever needs refrigerating. DirkvdM 14:02, 7 August 2006 (UTC)[reply]
dual core processor
If apple or dell mentions a dual core processor to be 2 GHz in speed, then will its speed be equal to a 2 GHz single core processor or will its speed be equal to 2 x 2 = 4 GHz? ie. twice a 2 GHz single core processor?
ThankZ
Generally, they are talking about the clockspeed of each chip, so you will have two 2GHz chips (actually, half-chips) but it is an oversimplification to say that thats actually 4GHz in total as they are speeds, and not completely additive. 48v 17:21, 6 August 2006 (UTC)[reply]
The processing speed of the cores will each be 2GHz, but this does not mean that together they achieve 4GHz. The Dual core will do things quicker only because more tasks can be performed simultaineously at that speed. The Guy From Ipanema
If the clock speed is 2 GHz, then that's what it is. If you have two watches, that doesn't mean they go twice as fast. In case you meant performance-equivalent, I can't give you a figure, but it'll probably be under the performance of a 3 GHz single-core. Getting two processors to work on the same thing is very difficult. They would spend a lot of time waiting for the other's results before they can proceed. This is one of the most difficult programming tasks one can face. So it depends much on the programs that run on them, too, unless there is some very clever operating system that has a general solution to this. DirkvdM 14:10, 7 August 2006 (UTC)[reply]
Hep C and organic sulfur
The question is what is the correlation between organic sulfur,
bio available sulfur and Hep C.
The reason I ask the question is Dr. Burton M Berkson reported
on MedPlus in 1999 three cases of liver regeneration with IV
sulfur based amino acids and selenium in about a year of treatment.
Currently Hep C is addressed in the medical community with either
liver transplants which often are infected after the transplant
and Interferon chemo therapy which has limited applications.
Being that Dr Berkson article dates from 1999 I was curious about
the sulfur link being that a Member of the Live Blood Study had
the same results ingesting 12 grams of organic sulfur which he
obtained from the Study in 15 months. His viral count drooped
7 million and his biopsy demonstrated healthy new liver cells.
We in the Study believe that considering the nature of Hep C
the availability of bio available organic sulfur could be a
factor in this deadly viral infection. Viruses hate oxygen
and sulfur as well as selenium enable the transport of oxygen
across the cell membrane as described in David Gregg's Ph.D
article “MSM and DMSO the oxygen transport pair.”
It is also the belief of the Study that this lack of sulfur in
our diets can be tied to two things: First the use of chemical
fertilizers in the US, 1954, and the use of chlorine to purify our
water systems, chlorine is an effective block for the uptake of
sulfur.
The results of the Live Blood Study have yet to be published to
date but this information regarding Hep C and other viral infections
appears to be too important not to address and we in the Study would
welcome any input regarding a possible treatment of all viral disease
which has no side effects.
Patrick McGean
Director Live Blood Study
of the Body Human Project
search google for the Live Blood Study under “Patrick McGean.”
Please state the citations to the Berkson and Gregg papers. Also, please give a url, do not ask us to search google. I tried and all I got back was a big pile of medical pseudoscience and I couldn't see the good information you are referring to. --GangofOne 01:16, 7 August 2006 (UTC)[reply]
seems there might be something in it, but the treatment is in early days (phase 1 published in 2005). i guess that doesn't stop snake oil peddlers from making a few dollars at the expense of an increasingly scientifically illiterate public.
that about does it i'd say. Xcomradex 08:51, 7 August 2006 (UTC)[reply]
the white living things on lobsters
I was in a store the other day and saw a lobster tank. I went over to take a closer look and there were white things all over this lobster on its head and one of its claws. The white things were in a mound and had some kind of living thing in the center of it that would go in and out of the mound. It was small and looked like a fan. I have looked everywhere and cant find out what they are. So what are those white things living on the lobsters?
>> Whales have something similar the are refered to as whale lice, but are accutually crustations, they live on the whale and reproduce.--Aaron hart 09:39, 9 August 2006 (UTC)[reply]
Death by Dreaming
According to popular beliefs, if a person dies in his or her dream, that person would die in real life. This this belief true? If it is true, why is that, and if it is not true, what ths the rationale behind the belief?
--72.57.219.186 18:59, 6 August 2006 (UTC)[reply]
No, it isn't true. I die in my dreams all the time (usually by falling off of tall things, I always seem to lose my balance in my dreams; though the other day I was shot in the gut! A bit more violent than usual, and my sides actually clenched when I woke up immediately after). The rationale behind the belief is probably just that people of all cultures have regarded the reality-state of dreaming to be a mysterious area, one ripe for mystical speculation and myth-making, and have believed that it can enter into one's waking life as well. Though it would seem snarky to postulate that Freud's theories on dreams were just a modern extension of this, he himself acknowledged as much in his The Interpretation of Dreams at many point, placing himself in the tradition of those who in the past believed that the life of the dreamer and the waker were intimately connected. My personal favorite approach to this is Borges' The Circular Ruins. --Fastfission 19:13, 6 August 2006 (UTC)[reply]
Actually, it's perfectly true. If you die in your dreams, you're guaranteed to die within the next 200 years. Until medical science makes a major breakthrough, at least. Confusing Manifestation 00:38, 7 August 2006 (UTC)[reply]
I'm giving a cautious overestimate. Just because the actual value is, at the moment, around 120 (assuming that the world's oldest people dreamed of dying in their first few years of life) doesn't mean that there won't be someone who dreamt of dying 100 years ago, and in 100 years time (thanks to aforementioned medical breakthroughs) says "That's funny, that guy on Wikipedia said I'd be dead by now." Assuming they've managed to cure Alzheimer's as well as everything else. Confusing Manifestation 00:15, 8 August 2006 (UTC)[reply]
Are you...serious? This isn't the Matrix, maybe you forgot... ? --mboverload@ 10:26, 7 August 2006 (UTC)[reply]
If soneone is already weak, the shock of a nightmare might do them in, I imagine. DirkvdM 06:26, 8 August 2006 (UTC)[reply]
evolution of white skin
hi,
given that black skin burns less and is less suceptible to skin cancer (this may not be true, its just something i've always assumed), what is the evolutionary advantage of white skin? is there one? given that we're all supposed to have come from afica originally, it seems bizarre that people in colder climes have different pigmentation when it doesnt serve an (obvious) purpose. any enlightenment would be much appreciated- thanks 200.166.84.18 19:19, 6 August 2006 (UTC)[reply]
The short, simple, general reason given is that pale skin is able to produce more vitamin D from less sunlight. Skittle 20:22, 6 August 2006 (UTC)[reply]
Which is quite useful in less than tropic localities. - Mgm|(talk) 20:50, 6 August 2006 (UTC)[reply]
Except the evidence, at least with regards to MC1R, suggests that is not the case. However the exciting discovery of SLC24A5 and its association with human skin colour, may provide evidence for positive selection for vitamin D production. Time will tell. Rockpocket 06:27, 7 August 2006 (UTC)[reply]
evolution of snoring
Given that snoring makes it easier for lions to eat you when you are asleep. Is it true that Africans do not snore? Ohanian 22:02, 6 August 2006 (UTC)[reply]
that is the smartest thing I've seen all week
Why does snoring make it easier for lions? 8-?--Light current 01:27, 7 August 2006 (UTC)[reply]
Lions have big ears to find you when you make noise. This does not help them to eat you, though. There are lions in less than 20% of Africa. Now we are looking for a testimony about real africans really snoring like you and me. --DLL 19:35, 7 August 2006 (UTC)[reply]
Having lived in Africa for a number of years, where i attended a boarding school. I can confirm Africans do snore. Loudly. Rockpocket 05:35, 8 August 2006 (UTC)[reply]
Northern Europeans would freeze to death if they had no protection against the cold, such as houses. Africans don't need houses against the cold (well, not as much anyway), but they do help against lions. So they can snore for the same reason we can survive without fur. We have different means - our ability to change our environment (ie build houses). DirkvdM 08:32, 8 August 2006 (UTC)[reply]
Porosity vs. Heat Capacity
How does the porosity of an object relate to its thermal capacity? For example, does a material with more pores allow more heat to pass through it than an object with fewer pores?
Depends probably on the comparative thermal conductivities of the pores (air) and the material of the object. BTW did you read your own question? 1st part makes no sense.--Light current 01:31, 7 August 2006 (UTC)[reply]
Oops...
Persykology
What's the deal with that strong desire some people have, on encountering an extremely cute and appealing organism, to kill it? I know that sometimes when I see a cute animal I want to squeeze it to death. What's with that? Also, why do people find baby animals appealing anyway? I suppose it would have been an evolutionary advantage to our ancestors as part of the domestication process, as anyone finding an abandoned wolf cub, finding it cute and raising it would have an obvious advantage when the bugger grows up, eh? Try and answer my first question first because you may have forgotten about it, I know many people who would have :P Vitriol 23:03, 6 August 2006 (UTC)[reply]
I'm sorry, but I have never heard of a desire to kill cute, appealing things as a common response. As for why baby animals are appealing, see cuteness. --Ginkgo100talk · contribs · e@ 20:47, 7 August 2006 (UTC)[reply]
I'm sure some people would know what I'm talking about. Or maybe I'm just nuts. Vitriol 23:09, 7 August 2006 (UTC)[reply]
I'd say that when people remark that they want to hug/squeeze something 'to death', they're not actually serious. It's more of an indication of how cute something is. --Con 23:26, 7 August 2006 (UTC)[reply]
O RLY? I am nuts! Vitriol 23:37, 7 August 2006 (UTC)[reply]
Welcome to the club! (Although my nutness lies in other areas (and why doesn't my spellchecker protest against the word 'nutness'?))
Btw, I love baby crocs. They have this unique combination of cuteness and a vicious appearance. DirkvdM 08:40, 8 August 2006 (UTC)[reply]
I don't think you're nuts, Vitriol - I've felt it too, and know several people who have - I reckon it manifests in such phrases as 'I could just eat her up', and 'I love her to pieces' - it's like cuddling the object of your affections isn't enough - you want to squeeze! There's a scene in Punch Drunk Love where the lovers tell each other they want to smash each other's faces in with mallets etc - but it's extremely tender; they're saying kissing each other just won't suffice to express the fierceness of their love. Well, that's what I think anywayAdambrowne666 01:40, 10 August 2006 (UTC)[reply]
natural hydrogyn production
Is the Earth's atmosphere filling up whith hydrogyn? If so at what rate?
...should it be? Vitriol 23:49, 6 August 2006 (UTC)[reply]
Why would you think that? I can't think of anything that naturally releases hydrogen gas. —Keenan Pepper 00:35, 7 August 2006 (UTC)[reply]
YOUR MUM! Hahahahahahaha Vitriol 00:36, 7 August 2006 (UTC)[reply]
Humans do not release hydrogen.(at least not in large quantities). Also, this page is not for stupidly childish comments like that above.8-(--Light current 01:19, 7 August 2006 (UTC)[reply]
Yeah but when you set fire to farts, its the methane that ignites- is it not?--Light current 02:25, 7 August 2006 (UTC)[reply]
No, hydrogen in the atmosphere is excited by ultraviolet light to react with oxygen and form water. Hence it is not accumulating. In addition, like helium, hydorgen is so light in its pure form that the portion that manages to rises to the top of the atmosphere without reacting with oxygen is slowly blown into space by the solar wind. Even without an oxygen atmosphere, a planet with the mass of Earth at our distance from the sun would not be able to accumulate much free hydrogen because the solar wind would blow it all away. Dragons flight 06:25, 7 August 2006 (UTC)[reply]
Is it possible to build a rechargable battery that could hold a Megawatt or more?--67.126.143.196 00:09, 7 August 2006 (UTC)[reply]
EDIT'D because someone mistakenly put their question here, eh? Vitriol 00:50, 7 August 2006 (UTC)[reply]
A megawatt is a measure of power and you cant hold power in a battery. Howver if you mean megajoule which would give 1 MW for one second, then it should be possible by connecting lots of small batteries together. Why would you want to do such a thing anyway?--Light current 01:05, 7 August 2006 (UTC)[reply]
1 million joules is easily held in a typical car battery, and is a relatively small number compared to what's typically used in commercial UPS applications. A common large scale UPS configuration will have 200 or more batteries, together capable of discharging up to 1MW each second, for up to 15 minutes, amounting to almost 1GJ of energy. Did you mean for it to be portable? --Jmeden2000 21:46, 7 August 2006 (UTC)[reply]
And how large is this GJ battery pack?--Light current 02:10, 8 August 2006 (UTC)[reply]
Imagine a whole room full of batteries, and then double it :-) --Jmeden2000 15:16, 8 August 2006 (UTC)[reply]
Persactly! That Y I suggested HV capacitors.--Light current 15:22, 8 August 2006 (UTC)[reply]
Too bad there isn,t one the size of a car but thanks alot for the help.
Wouldnt you need a bunch of fuel cells to produce 1 Million Joules? A car sized battery or device that could produce power in the millions of joules would be perfect for spacecraft, using possibly Ion Thrusters or some sort of electrical thruster.
Dont ask me -- look at the page! 8-)--Light current 21:23, 8 August 2006 (UTC)[reply]
Septic System
I can't seem to grasp the workings of a septic system
If I use DIAL soap, and dial soap is anti-bacterial, as is most of the laundry detergents on the market, doesn't that cause the septic system to shut down?
Why aren't there enough "bacteria" in the human by-products going into a septic tank so that you don't have to add an additive of more bacteria?
Thanks
Larry
You shouldn't have to add any kind of additives to a properly-functioning septic system. The enzyme treatments and other things sold to be used in septic systems are not really necessary. The things that cause a septic system to fail are pretty simple mechanical failures: Over time, the indigestible solids will accumulate in two places- as a floating scum layer, and as solids that sink to the bottom. Given enough time the scum layer can become very thick, and the solid layer at the bottom can also become very thick, and so the 'working space' below the scum layer and above the solids becomes too thin to be effective.
If the baffles fail, then it's possible for the scum layer to drain down into the drain field, where it may plug up the orifices in the laterals, severely affecting the ability of the drain field to function. So having the system checked, inspected, and pumped out every five to ten years will greatly help it to keep working. You don't say if it's a gravity system or a pressurized system; gravity systems tend to fail over time because the flow rate through the drain field is very low. It's not hard to inspect a septic system, doing a google search will point you in the right direction; a couple simple tools and some time and you will be able to check your system out.
I almost forgot to answer your original question: Yes, excessive use of antibacterial products may cause harm to your septic system. The key words are 'excessive' and 'may'. Normal use seems to be fine, just don't go overboard. For additional reading, see pages like this one .71.112.133.208 04:00, 7 August 2006 (UTC)[reply]
You don't need to add bacteria because they are quite capable of doing that themselves through reproduction. And unless you throw in huge amounts of antibacteria, they shouldn't be hurt too much. Bacteria can take quite a beating. DirkvdM 08:47, 8 August 2006 (UTC)[reply]
hang-drying clothes indoors with A/C
If I have my air conditioner on, and I hang up my wet clothes indoors to dry, I figure I'm essentially asking the A/C to do the work that the dryer would otherwise be doing, and in theory it might take the same amount of energy. But what about in practice? Considering the different technologies and drying times, would one process (A/C vs. dryer) would use more energy than the other, or would they be about the same? Thanks. --Allen 00:48, 7 August 2006 (UTC)[reply]
I don't know if this is any better than just having a fan blowing on the clothes.
It is better, becuase an A/C (or a dehumidifier) will remove the moisture from the air leading to quicker drying. A fan would just tend to make the air more humid, reducing its drying potential. 8-)--Light current 14:31, 7 August 2006 (UTC)[reply]
How does a fan make the air more humid? DirkvdM 08:50, 8 August 2006 (UTC)[reply]
By transferring the water from the wet clothes into the air of course!--Light current 11:26, 8 August 2006 (UTC)[reply]
The primary function of an airconditioner is to cool the air, which doesn't help in this case. If it's so hot outside that you need an airconditioner, then why not hang your clothes outside? DirkvdM 08:50, 8 August 2006 (UTC)[reply]
It could be raining outside but hot inside 8-)--Light current 13:23, 8 August 2006 (UTC)[reply]
The action of cooling the air also dehumidifies it as the water condenses on the cooling coils!--Light current 11:48, 8 August 2006 (UTC)[reply]
Exactly, Light current. It often rains in the afternoon in Tennessee, even on the hottest days. So if I hang my clothes on indoor drying racks instead of using the dryer, I'm curious to know whether I'm conserving energy or just inconveniencing myself. --Allen 04:03, 9 August 2006 (UTC)[reply]
Depends on the comparative efficiencies of the AC unit and the drier. 8-) You dont say what sort of drier it is. --Light current 11:01, 9 August 2006 (UTC)[reply]
Hot mirrors
Today it was rather warm (say 25 celsius) and humid. This afternoon, I was standing about 0.7 m in front of some large mirrors for a long time (playing a gig actually). I noticed that it felt considerably hotter infront of these mirrors than in other parts of the room or even outside. I initially thought it was the IR from the surroundings reflecting but since IR cant travel thro normal glass, I remain puzzled. 8-? Any suggestions as to the cause of this phenomenon? --Light current 01:13, 7 August 2006 (UTC)[reply]
Yeah thanks for that, but those cookers use no glass. I was cooking in front of glass! Also, it wasnt sunny-- complete cloud cover.--Light current 01:37, 7 August 2006 (UTC)[reply]
No glass? Read a little more closely. Almost all of them are made of glass/mirrors. Even when it is completely cloudy there is still lots of solar radiation reaching the surface. Rangek 02:04, 7 August 2006 (UTC)[reply]
Yeah OK, but theyre using high intensity visible light energy from the sun. THere was not much light in the room and IR cant pass thro the glass to be reflected by the silvering on the back of the mirrors. Mirrors can reflect IR if they are front silvered (or just a shiny bit of metal)--Light current 02:15, 7 August 2006 (UTC)[reply]
Is that what youre saying? If so, what sort of radiation would that be? Would it be the near IR, and if so can you feel it as heat?--Light current 13:15, 7 August 2006 (UTC)[reply]
Can I ask where it is you live that it's only 25 degrees Celsius? Southern hemisphere? Iceland? Seems most of the northern hemisphere is in the throes of a long-lasting heat wave. Today is a cool day where I'm from and it's supposed to hit about 30 Celsius. --Ginkgo100talk · contribs · e@ 20:50, 7 August 2006 (UTC)[reply]
The northern hemisphere is slightly bigger than where you live. :) The heat wave in Europe is long over. DirkvdM 08:56, 8 August 2006 (UTC)[reply]
Okay. The last I had heard, Europe was still suffering. The veiled insult was unnecessary. --Ginkgo100talk · contribs · e@ 18:07, 9 August 2006 (UTC)[reply]
Its the UK. And maybe it was 27 or 28 Celsius. I didnt have a thermometer handy!--Light current 01:42, 8 August 2006 (UTC)[reply]
I suspect you are thinking of UV not easily passing through glass. --Seejyb 22:15, 7 August 2006 (UTC)[reply]
No Im thinking of IR. UV can pass thro glass I believe. Think of greenhouses! 8-|--Light current 01:42, 8 August 2006 (UTC)[reply]
Ahh it must be visible light that passes thro glass in a greenhouse then and gets converted ito far infra red?--Light current 03:24, 8 August 2006 (UTC)[reply]
Actually, it turns out that has very little to do with how greenhouses work. See greenhouse. It turns out it isn't so much that the greenhouse is trapping the radiation, but it is just not letting the hot air drift away. Rangek 18:29, 8 August 2006 (UTC)[reply]
And the hot air being above absolute zero emits radiation- yes? seeWein's laws. If this radiation can escape thro the glass then the heat will not be retained. What is the wavelength of the radiation at 300 K? and can it pass thro greenhouse glass -- that is the question! 8-|--Light current 19:44, 8 August 2006 (UTC)[reply]
Any chance it has nothing to do with the mirrors? Was there anything else about that spot? Maybe less air current (the back of a room?). And you were doing a gig, so were there any lamps pointing at you (although I doubt you would have missed that option). DirkvdM 08:56, 8 August 2006 (UTC)[reply]
Dont think so. There were 3 lamps each of 60W spaced at about 1.5 m between the mirrors. As this power was only equivalent to that generated by about two persons, I decided that this could be ignored. It felt like a few hundred watts on my back. Also i was standing in the center of the mirror (not in front of any of the lamps). Also it felt like radiation, not warm air.--Light current 11:33, 8 August 2006 (UTC)[reply]
Some confusion here. Glass normally absorbs UV; Reflects a lot of IR (feel the reflection from an ordinary glass pane when you shine an IR light on it; maybe you would have felt the same heat standing in front of unmirrored glass, especially if you were wearing black). But definitely transmits some IR. Herschel discovered IR by transmission through an ordinary glass prism - there was something measurably hot coming through beyond the red end of the spectrum, and the heat he measured was more than that from the red part coming though the glass of the prism. Most optical cables use IR for transmission - once the light is in the glass fiber, with not as much being absorbed as shorter wavelengths would, it is tranmitted better than visible or UV light of the same initial energy. If you put an IR lamp in front of an ordinary glass pane you can feel the reflection of heat. "Ordinary" 35mm cameras can take quite effective IR pictures with "ordinary light" lenses, using IR sensitive film - the focus has to be compensated for, but some lenses have IR markings on them. --Seejyb 01:13, 9 August 2006 (UTC)[reply]
OK this makes the most sense yet. So I was getting about twice the radiation that I would have got if there had been no mirror and just the brick wall? Hmm -- interesting!--Light current 03:01, 9 August 2006 (UTC)[reply]
Plane on conveyer
Why there's no article about that famous plane on conveyer that some mistakingly claim won't take off? It was twice on Straight Dope with two conflicting answers on 03.03.2006 and 03.04.2006 and that alone makes it notable. By the way, the plane will fly off with wheels sliding all the way, contrary to the second article :)
The two articles are [12] and [13]. I'd like to take the position that the second article is correct: the conveyor belt can be rigged so that the plane does not take off. Just as the plane starts moving forward, you speed up the belt so that the plane nudges back where it was one second ago. Keep doing that, and you get a balance where the friction of the wheels causes a backwards force that exactly balances the forward force of the plane's engines. Zero net force, no movement. Weregerbil 07:32, 7 August 2006 (UTC)[reply]
But if lift is generated by air moving over the areofoils, and there is no air moving over the areofoils due to the wings not moving through the air, how can the plane take off? --130.161.182.112 14:29, 7 August 2006 (UTC)[reply]
Right. In one interpretation the question can be reduced to: Will the plane pick up enough absolute speed? If we manage to keep the plane in place by increasing the belt speed more and more, the wheels will also spin very fast and eventually generate so much heat through friction that the axle melts, or else the wheels come apart by the centrifugal forces. If we assume idealized components not subject to such mundane effects, you have to be very precise about which parts of physics are still operational. If the plane remains stationary while the belt moves extremely fast, the belt will drag air along and cause so much wind that the plane still gets sufficient lift. And so on ... --LambiamTalk 16:23, 7 August 2006 (UTC)[reply]
If we have a real plane its engines have finite maximum power, so at some point the speed of the belt stabilizes and significant air flow from the belt doesn't necessarily need to happen. Or maybe it will. This could be one of those things that needs to be tried in practice. How do you go about suggesting things to the MythBusters? :-) And no wimping out by using a small model plane. Weregerbil 16:43, 7 August 2006 (UTC)[reply]
Lift requires that the plane be moving in reference to the air, not the ground. --mboverload@ 00:31, 8 August 2006 (UTC):[reply]
I've seen this question beat to death dozens of time on the internet. I like this discussion the best at physicsforums [14]. — [Mac Davis] (talk)
float glass
What is float glass? And what is the russian translation for it? Inna.
Our page entitled Float glass is probably a good place to learn what it is. DMacks 05:57, 7 August 2006 (UTC)[reply]
I suspect that in Template:Lan you can use полированное стекло ("polished glass") or for an audience of experts simply флоат-стекло. --LambiamTalk 08:26, 7 August 2006 (UTC)[reply]
Photons
Photons have no mass, yet they can exert radiation pressure(mass-mass interaction involving change in momentum?
Yes. While they do not have any mass, they nevertheless have momentum (given by h/λ, where h is the Planck Constant and λ is the wavelength of the photon).
>>This one took me eight years to figure out, 'And yes Photons at times do indeed have mass', refered to as rest mass, but there is really no difference, it's just the termanology. I will give you a hint; photons as electromagnetic energy have no mass, and can even travel through two slits at the same time ( ie. the dual slit experiment). Yet durring an interaction (such as striking a white or black piece of paper), like an inferometer their velocity is no longer the speed of light, and they are no longer electormagnetic rediation but a particle that has mass aquired from the conservation of evergy. This is only a hint, It seems to be from my experience a close held secret, at least for undergraduates. Other clues in space time energy fluxuations cause mass to "pop" out of energy, then the mass transfers back to energy. Also in a clyclatron durring a collision there are particles with mass that have a spiral trajectory in an electromagnetic field, but are short lived before they "disaper or transform into energy." It goes both waysAlso They Do Have Mass When Transfering Momentum!.--68.189.46.87 12:52, 7 August 2006 (UTC)aaron.[reply]
When you talk about the rest mass of the photon I assume you mean (hf)/c² (or p/c). I don't believe that is of any consequence in this question, although a good means of explaining where photons get their momentum from.
Yes the rest mass is relative to this question, It is the mass of the photon when it exist as a particle!Durring an interaction. The Photon acctually has the mass of the rest mass, for a brief period of interation! aaron--68.189.46.87 14:02, 7 August 2006 (UTC)--68.189.46.87 14:02, 7 August 2006 (UTC)[reply]
>>>Do I need to repeat the old adage of photons at times behave as electromagnetic radiation and at other times as a particle. Think about it, I believe I have explaned it, if you don't understand, quit trying>>>Photons durring interactions are particles with a mass equal to their rest mass. Look up the interaction tables! aaron--68.189.46.87 14:22, 7 August 2006 (UTC)[reply]
When I say I don't think it's of any consequence, the question didn't ask for the mechanisms by which momentum was exchanged. The effects are described well enough by whoever gave the second answer. I can assure you I do understand wave/particle duality, I did do a PhD in quantum computing.
Sorry but I felt that the mechanisms by which momentum was exchanged was relavent to the understanding of the original question, in my opinion. I trust you opinion and your understanding, but since the question stated that photons have no mass in my opinion it was relative. Again Im sorry. aaron--68.189.46.87 15:01, 7 August 2006 (UTC)[reply]
That's quite alright. I generally hesitate to use the term 'mass of a photon' because, while they may have mass during an interaction, it is only for a very short time and time and energy/mass are non-commuting variables.
What about reading our article Photon? Photons have energy and therefore also have mass in the usual sense of gravitational mass. The usual meaning of "rest mass" is the mass at zero speed, which is meaningless for photons, but using the formula for relating (relativistic) mass with rest mass, you find a rest mass for photons that is zero, zilch, nada. --LambiamTalk 16:33, 7 August 2006 (UTC)[reply]
Yes you are correct the rest mass of a photon is a misnomer, since it can never be at rest, it is an old term for it's mass at non relativistic speeds. But durring interactions when it is a particle it does have mass, read the article photon and you will find an approximation for a photon's mass. Not rest mass but mass --68.189.46.87 17:50, 7 August 2006 (UTC)aaron[reply]
The term 'rest mass of a photon' is a useful (if rather antiquated) terminology for explaining radiation pressure. Mathematically it comes from the energy of a photon, E=hf and E=mc² and gives m=(hf)/c²
>>Yes mathematically, but the truth of the matter is that it is a particle for a brief period of time durring the interaction, it is a actually a partical with mass that is not traveling at the speed of light; and this does come from the energy of the photon, which is transformed into mass. Which may or may not transforme back to pure energy with no mass, travaling at the speed of light--Aaron hart 07:22, 8 August 2006 (UTC)[reply]
Black holes
How come black holes have two beams of energy?
The polar jets or relativistic jets don't come from the black hole itself, but rather from the accretion disk around a black hole. StuRat 06:46, 7 August 2006 (UTC)[reply]
I have found a rock that is 1235 cm^3 and weighs only 148g, this gives it a density of .12g/cm^3. Is this just a large size of unusual pumace. It has a honycomb sturcture on the outside, but under an ultraviolet light, there is a distinct differece (as in two distinct layers, like the bottom side was heated to a much higer temp. than the top. Also on the top there is a bump with the lighter grey comming from the tip to the bump, and then it darkens,) I can see how the heat has effected it, turning it a lighter grey?? It is black to dark grey any coments??
aaron--68.189.46.87 14:38, 7 August 2006 (UTC)[reply]
Could it be a chunk of an artificial building material, like foamed slag concrete, pumice concrete, or expanded shale? Femto 15:13, 7 August 2006 (UTC)[reply]
>>No it was found out in the woods on the top of a hill, It is definatly all natural, Thanks for the advise though.
Pumice is a good idea. --DLL 19:28, 7 August 2006 (UTC)[reply]
The density of Pumice can vary quite a bit but I've never heard of a sample that light before. The range is usually somewhere between 0.6g/cm³ and 1.2g/cm³. Where do you live? Do you have a picture of the rock that you could post? --Nebular110 19:33, 7 August 2006 (UTC)[reply]
Honeycomb structure? Is it a nest of somesort? Wasps make very light nests... Isopropyl 00:00, 8 August 2006 (UTC)[reply]
Yes I can post a picture, if I can find out how, and no it is not a nest of somesort, it's almost like a carbon structure, I will attempt to upload a photo, if unsucessful I will post my email and I will send it to you. aaron--68.189.45.241 03:32, 8 August 2006 (UTC)[reply]
This rock was found in Shasta County, ca. on the top of a hill, and yes the density is aporxamatly .12g/cm^3 I believe this to be rare, Please reply--Aaron hart 07:02, 8 August 2006 (UTC)aaron[reply]
It looks like scoria, but I think that would typically have a higher density; I don't know the range. Tuff can be very light, but usually doesn't look so rough. I think that also applies to cinder, which however can be so light (according to our article) that it even floats on water, so that aspect fits. --LambiamTalk 07:57, 8 August 2006 (UTC)[reply]
Looks like the carbon left over after the dehydration of a sugar, can that happen naturally? PhilcTECI 12:21, 8 August 2006 (UTC)[reply]
Looks like a large piece of coke (coal with all the hydrocarbons removed leaving only pure carbon) Can you see any pores in it. Cant tell from photo--Light current 13:46, 8 August 2006 (UTC)[reply]
Could it possibly be extra terrestrial?--Light current 14:06, 8 August 2006 (UTC)[reply]
According to [15] there are no lightweight meteorites. Femto 15:13, 8 August 2006 (UTC)[reply]
Aaron, forgive me if I sound patronizing, but are you sure you got the weight right? Any silicate is going to have a local density of ~2 g/cm^3. Pumice and other volcanic rocks can lower their bulk density by incorporating air pockets and voids, but your pictures shows no evidence of voids intersecting the surface. Similarly, with the dimensions shown, it couldn't have more than a few millimeter thick shell of silicate, in which case I'd expect it would have been so fragile that it would long ago have broken. At less than 200 g, even a decent wind should be able to blow it around and smash up the thing. If it really has the density you say, my only conclusion is that it can't be a rock, and is likely to be synthetic. What is the texture like? Is it rough? Squishy? My guess might be some sort of weathered packing foam. Dragons flight 14:45, 8 August 2006 (UTC)
>> Yes the mass not the weight is 148g. And I really doubt that it is packing foam, I guess I will have to take it to the local colledge, and then I will let you know. its tecture is very hard and brittle, pices come off of it every time I pick it up.--Aaron hart 14:51, 8 August 2006 (UTC) but you may be correct, we shall see, maybe I found something rare??
>>Forgive me I checked very accuratly and the mass is 147.2g--Aaron hart 15:01, 8 August 2006 (UTC) also it is full or pores, and I can tell that the crust is more than a few mm thick. But it may be synthetic, just seems ood to find it on top of a hill in the woods.--Aaron hart 15:04, 8 August 2006 (UTC)[reply]
Strange. Did you break it open to see what the inside is like? Is it mostly hollow maybe? Were there other specimens similar in the area or did it look totally out of place on the top of the hill? --Nebular110 17:43, 8 August 2006 (UTC)[reply]
It would be good if it was a new stone; they could call it Hartstone! smurrayinchester(User), (Talk) 21:48, 8 August 2006 (UTC)[reply]
Two Cars in a Head-On Collision
In my game PGR3 (in which I find the physics very unrealistic) I was going to run in to my brother in a head on collision. I was going 207 mph and he was going 183 mph. With the physics like they are, the cars collided and not a whole lot happened. My question is, how much power would that exert? I'm not real smart about Physics, but I remember the Law of Conservation of Energy and that the energy is still there, you just don't see it(?) and all the energy those cars had were almost immediately gone. I hope someone understands my rambling here. Thanks. schyler 12:04, 7 August 2006 (UTC)[reply]
Without knowing the game I guess they may be simulating the energy absorbing features of the cars and they just crumple up. THe energy is used in deforming the metal, creating sound etc but all the enrergy finally ends up as heat if both cars are at rest. THe kinetic energy of each car is 0.5 mv^2, so you could work out how much energy was dissipated in the crash (assuming both cars are at rest afterwards).--Light current 13:23, 7 August 2006 (UTC)[reply]
Also unlike Kenetic Energy the momentum for the two cars before and after is absolutly conserved, Kinetic Energy is also conserved but takes on other form. But The momentum before and after the collision are the same. Momentum=mass*velocity so if they came together at a complete rest, without one or the other moving backwards, the masses of the two cars must be different, in other words v1m1=v2m2. In a system Kinetic energy is transformed into deformation, heat, sound etc. and as stated earler end up as heat. But momentum is conserved without transformation into other forms. Although after both cars come to a rest there is frictional momentum that is transformed to the earth. aaron--68.189.46.87 13:33, 7 August 2006 (UTC)[reply]
You are right about the shoddy physics, especially with respect to collisions. Most driving games don't bother with them since its little or no fun to watch a car turn into 'not a car' and then require the player to start over. The question I think you should be asking (since you probably know that you are just dealing with two huge quantities of kinetic energy) is 'where would that energy go to?' Objects collide and one of two things happen to the kinetic energy, a) An elastic collision where kinetic energy is conserved and b) an inelastic collision where kinetic energy is converted into internal energies. Since cars are quite dynamic there would be a combination of these two as the various metal and plastic bits met head on. Much of the energy is 'gone' into another form such as heat, as the metal in each chassis takes on a dramatically different form. Some energy may come back kinetically and one or both cars will continue moving after the collision, or (more likely) many small bits from each would keep moving. --Jmeden2000 21:17, 7 August 2006 (UTC)[reply]
It's not a physics answer, but the reason why the cars don't suffer a whole lot of damage/body deformation in the game is because the car manufacturers, who licence their cars for use in the game, don't want their brand associated with mangled wreckage, etc. (or so rumour has it). On the other hand, a game like FlatOut which uses generic unbranded cars can mangle the bodywork all it likes. Sum0 23:33, 7 August 2006 (UTC)[reply]
>> Also in deformation of the cars there energy put into the deformation, but also this creates a large amount of heat, The Physics may be shoddy, but sugesting an elastic collision, with cars, come on now! aaron--Aaron hart 07:14, 8 August 2006 (UTC)[reply]
Did you even read my entire reply? Just curious, i know i tend to ramble sometimes but i did get everything in there i intended to --Jmeden2000 15:12, 8 August 2006 (UTC)[reply]
>>A perfectly elastic collision is defined as one in which there is no loss of kinetic energy in the collision. An inelastic collision is one in which part of the kinetic energy is changed to some other form of energy in the collision. Any macroscopic collision between objects will convert some of the kinetic energy into internal energy and other forms of energy, so no large scale impacts (ie larger than atoms, or molecules); are perfectly elastic--Aaron hart 07:04, 9 August 2006 (UTC) I do remember a little from college. For a possible elastic collision occuring, solids from the car body, must vaprorize into a gas, then it is possible for these two gasses to have a perfectly elastic collision, But this would be quiet neglagable, and would not even beging to be able to be calculated!--Aaron hart 07:15, 9 August 2006 (UTC)[reply]
biology
hi im a student of psg biotech....can anyone say how to estimate the density of spores like vegetative spores or especially the spores of bacilus subtilis.....give some detailed explanations....
Sounds like homework. I'd try a PubMed search for bacilus subtilis spore density and follow the protocols given in the articles. -- Scientizzle 18:15, 7 August 2006 (UTC)[reply]
In the microwave article, it says that after 15 minutes of use, the power of the microwave drops off - is this true? What is the cause? The text in question can be found at the bottom of the section which this link leads;
Microwave oven#Uneven heating, deliberate and not
It it is true, which it may well be, then it is a mechanical effect of the microwave oven, not with the microwaves themselves. --198.125.178.207 18:51, 7 August 2006 (UTC)[reply]
The magnetron gets less efficient as it heats up. There is a link in the microwave article that used to explain this, but it is now a dead link. --Heron 20:38, 7 August 2006 (UTC)[reply]
Pocket PC emulator
Can I run Pocket PC programs on Microsoft Windows using an emulator? -- Toytoy 14:21, 7 August 2006 (UTC)[reply]
I think that the answer is yes, that's why emulator design is for. Now, does such emulator exist, and did you try any search engine with the terms of your question ? -- DLL .. T 18:49, 8 August 2006 (UTC)[reply]
I believe that there is a Pocket-PC edition of Microsoft Visual Studio, which includes exactly such an emulator, as well as a Visual C++, Visual Basic, and other Microsoft programming environments/compilers for pocket-pc's. Are you a software developer, or just an end-user trying to use a PDA tool on your desktop? If the latter is the case, you may find a workaround using conventional desktop software for the same task. Nimur 19:39, 8 August 2006 (UTC)[reply]
I want to run MetrO on my Windows computer. I don't know why this program does not have a Windows version. -- Toytoy 05:55, 10 August 2006 (UTC)[reply]
A warm sun
Why does the sun feel warm when youre exposed to it? Its a serious question.--Light current 14:27, 7 August 2006 (UTC)[reply]
All electromagnetic radiation (including light) is just a form of energy. When the light hits your skin, some of it is reflected and some is absorbed. The energy in the light which is absorbed has to go somewhere (see Conservation of energy) and becomes heat energy. All light, natural and artificial, will transfer some heat energy to a surface it hits (as long as that surface isn't perfectly reflectant). -- Plutor 14:38, 7 August 2006 (UTC)[reply]
So you can get warm just from visible light?--Light current 14:40, 7 August 2006 (UTC)[reply]
OK thanks for shedding some light on the problem! 8-))--Light current 14:51, 7 August 2006 (UTC)[reply]
So do your eyes get warm when you look at things? I thought it was only glassblowers who got cataracts. 8-)--Light current 21:16, 8 August 2006 (UTC)[reply]
The sun is just a big firebrand. Visible light must take a very little part in the heating. Non-visible radiation (infra red) is also absorbed by the skin and diffuses to the body, it heats more accurately. --DLL 19:24, 7 August 2006 (UTC)[reply]
Well, he probably doesn't mean that the sun is made up of a bunch of cartoon characters, or that the sun is a burning ball of fighter planes so it's safe to assume maybe he meant that the sun is something that's on fire, like a giant bunch of burning wood.
Funny, 'brand' is Dutch for fire. What is the etymology of the word? DirkvdM 09:17, 8 August 2006 (UTC)[reply]
According to Webster's and Livestock branding, brand had meanings of hot stick/torch/sword in Middle English. I think I've seen -brand being used in sword names in the works of Tolkien as well. --Kjoonlee 13:56, 8 August 2006 (UTC)[reply]
I fear this thread is diverging rapidly--Light current 13:27, 8 August 2006 (UTC)[reply]
Sorry, firebrand was a bad googletranslatetool try. Let's say ember : hot burning wood. I meant that it is not the red that heats in it. -- DLL .. T 18:44, 8 August 2006 (UTC)[reply]
Ember is also a sort of bad translation. The sun's heat and light come from nuclear fusion, not combustion. Although it looks red, this is because the plasma is hot and acts as a blackbody, radiating energy in the visible spectrum and other wavelengths as well. You feel warm because you absorb some of the radiation in ALL wavelengths (albeit, more from some spectral elements than others). Ultra-violet radiation contributes to your tan (a bio-chemical process); infrared directly heats you, and visible light does contribute some heat as well. However, the sun is not an ember, or a firebrand - it is hot plasma of mostly hydrogen and helium undergoing thermonuclear reactions. Nimur 19:45, 8 August 2006 (UTC)[reply]
Ahh a sensible answer at last- THanks!--Light current 19:55, 8 August 2006 (UTC)[reply]
What the **"£$** have seagulls got to do with anything?--Light current 13:25, 9 August 2006 (UTC)[reply]
>> I thought the first two replies were sensible, and ansured your question, Not to make this thread any worse!--Aaron hart 07:24, 9 August 2006 (UTC)[reply]
Yes youre quite right Aaron. The first two replies were useful. Thanks 8-)--Light current 13:23, 9 August 2006 (UTC)[reply]
plz i am in ghana and did go to school but could not complete my highschool.but now i want to school in the nursing field at canada .so plz i will like to know how it will go and the steps i will be taking.i dont have any relations there but i want to school there and pursue my degree thank you
I think this question would have better chances on the 'Misc' page.--Light current 16:18, 7 August 2006 (UTC)[reply]
with spelling and grammar like that youre not going anywhere =P -PitchBlack
I could say that you meant to say "With spelling and grammar like that you're not going anywhere." but that would be unprofessional. Sum0 10:18, 9 August 2006 (UTC)[reply]
I know that GPS receivers usually report an estimate of the accuracy of the readings they provide, but I'm curious about their precision. Most give readings with seven digits, like N12° 34.567 W12° 34.567. How can you figure out the distance between that point and the very near one at say N12° 34.568 W12° 34.567? The distance between any two longitude lines is going to vary depending on how far you are from the equator, right? Is there any website that will calculate the distance between any two lat/long coordinates? 148.177.1.219 18:53, 7 August 2006 (UTC)[reply]
The circumference of the Earth is about 40.000 km or 360x60 = 21600 minute. So 1' = 1.85 km. That goes for all lattitudes and for longitude at the equator (at least if Earth were a perfect sphere, which it isn't, but I'm only giving an estimate here). For any other longitude, you have to multiply by the cos of the (mean) longitude. Luckily, you save me that trouble because the longitudes are the same. And consequently, I don't need Pythagoras either (the square root of the sum of the squares of the two distances). So the answer to your example is 34.568 - 34.567 x 1.85 km = 1.85 m. As a rule of thumb, 1° latitude is about 100 km (actually 111 km) and the same goes for longitude at the equator. At 60° north or south (roughly Scotland and New South Wales) it's half that. DirkvdM 09:47, 8 August 2006 (UTC)[reply]
See the Great-circle distance article for details about calculating distances between points on a sphere along its surface. DMacks 19:48, 9 August 2006 (UTC)[reply]
Scientist famous for numbering all correspondence and papers
I remember hearing about some scientist, I believe he was a physicist, who numbered pretty much everything he wrote for several decades. From journal articles to letters to friends. The numbering scheme was his three initials followed by a number (I think it was 4 digits).
Can anyone remember his name for me? Thanks.
Doesn't everyone do that? Notinasnaid 19:46, 7 August 2006 (UTC)[reply]
If I did that here, 4 digits wouldn't suffice. DirkvdM 09:54, 8 August 2006 (UTC)[reply]
I think there's something there for all of us to think about, Dirk. :--) JackofOz 12:03, 8 August 2006 (UTC)[reply]
It could do if the four digits were not decimal. hexa would'nt suffice ; but you may create any base (I have my eyes on the 'insert' template when editing this : 0123...ABC...ĕØΘЫɱ). -- DLL .. T 18:38, 8 August 2006 (UTC)[reply]
Death of fruits and vegetables
Usually I am able to answer my child's questions alone or by some quick research but this one has me stumped. My son asked me if the blueberries he was eating were dead. Are fruits dead when they are picked? When they rot? Some indeterminate time between these two? I appreciate anyone's help.
James
[email removed]
I would personally not consider a fruit or vegetable to be completely dead until it is unable to be planted and grow into a plant. There's still a seed of life inside anything that can be planted and grow. (forgive the pun) And by this reckoning, fruit can live for a very long time. http://en.wikipedia.org/wiki/Seed#Oldest_viable_seed
I believe the cells of most fresh fruits and vegetables are alive. When they die, they rot. The fact that picked fruits can continue to ripen is evidence they are alive. Seeds remain alive even after the fruit that contained it has died. Cooking, canning, toasting, and freezing kill cells, so non-fresh fruits and vegetables are not alive. --Ginkgo100talk · contribs · e@ 20:56, 7 August 2006 (UTC)[reply]
I think when we say that "X is alive", sometimes we mean "X is a living organism". As an example, we never say a person is alive after their heart and brain have permanently stopped working, no matter how many of their cells are still metabolising. So in this sense "alive" and "dead" have no meaning for picked fruit, because a fruit is not an organism. But other times when we say "X is alive" we mean something like "X is a collection of metabolising cells" or "X is a tissue or organ that could still function as part of an organism". So a fruit is alive the way a heart that's about to be transplanted into someone is alive, but not the way a person is alive. The seeds, of course, are alive in both senses. --Allen 21:51, 7 August 2006 (UTC)[reply]
There is a difference between plants and animals. In animals, the life of the organism is more important than the individual cells. By analogy, you could view the cells as bees, and the organism as the hive. The life of an individual bee is unimportant, only the hive matters. In plants, however, the individual cells and organs are more important than the organism, since they can survive and reproduce independently. (There are exceptions, like a planarian, which reproduces more like a plant.) So, I don't think you can apply the same rules to determining whether a plant, or portion of a plant, is dead that you apply to a human. I would say a piece of fruit is still alive, as long as it can still grow a new plant. StuRat 10:48, 8 August 2006 (UTC)[reply]
I love kids for asking such questions. That love quickly changes to hate when I try to answer them. One of the most important criteria for life is reproduction. Since fruit is itself a reproductive organ (?) it is alive as long as it can reproduce. Or is it the seed that is alive? If you remove it from the fruit, is the fruit then dead? Then again, I can still reproduce if I lose a leg, but that doesn't prove my leg is dead. Aaaarghhh! Also, I am now mixing up the definition of life in general (eg are viruses alive) and specific living things (eg is a headless chicken alive). DirkvdM 10:02, 8 August 2006 (UTC)[reply]
How can things live if they are cut off from their source of nutrients? Plucked Fruits have no source, so if they are not dead stright after plucking, they soon will be. THe question of rotting is something else, probbly depending on attack by fungi, bacteria etc. The seeds are not alive either-- only when supplied with nutrients can they grow and live.--Light current 12:01, 8 August 2006 (UTC)[reply]
Again, I think you are incorrectly applying animal standards for life and death to plants. The plant world has states between what we know of as life and death in the animal world (with perhaps a few exceptions, like spiders and insects that can stay dormant for years, then "come back to life" when conditions are right). I would say seeds are alive as long as they still possess the ability to sprout. StuRat 22:54, 9 August 2006 (UTC)[reply]
I am not eating now. Does that mean I am dead? DirkvdM 08:59, 9 August 2006 (UTC)[reply]
LOL. Probably, at least from the neck up! (joking) 8-)--Light current 13:51, 9 August 2006 (UTC)[reply]
Once a fruit is picked, can it be reattached to the plant it was picked from and start growing again? If so then I have to say at the point where this can no longer be done is the point of death. Keep in mind people have severed fingers and had them reattached hours later. Also, it seems link the plant which grows the fruit is what is really 'alive' not the fruit itself.
I saw a headless chicken once (on TV). It would run around the farm yard bumping into things. It was kept 'alive' by its owner pushing corn down its severed neck. 8-(--Light current 14:15, 8 August 2006 (UTC)[reply]
Usually not, but after a fruit is picked it can often be planted and grow into a new tree/plant/bush.... TenOfAllTrades(talk) 14:45, 8 August 2006 (UTC)[reply]
Yeah but thats because you are providing some nutrition again. THe plucked fruit probaly survives a short time. what about cut flowers in water, are they alive - or just not dehydrated?--Light current 14:58, 8 August 2006 (UTC)[reply]
Once I saw a vegetarian eating a banana. I asked her how would she like it if her skin was ripped off and she was eaten alive. Heh. This is by Carl Sagan, regarding your love-hate relationship with children's questions.
In East Africa, in the records of the rocks dating back to about two million years ago, you can find a sequence of worked tools that our ancestors designed and executed. Their lives depending on making and using these tools. This was, or course, Early Stone Age technology. Over time, specially fashioned stones were used for stabbing, chipping, flaking, cutting, carving. Although there are many ways of making stone tools, what is remarkable is that in a given site for enormous periods of time the tools were made in the same way—which means that there must have been educational institutions hundreds of thousands of years ago, even if it was mainly an apprenticeship system. While it's easy to exaggerate the similarities, it's also easy to imagine the equivalent of professors and students in loincloths, laboratory courses, examinations, failing grades, graduation ceremonies, and post graduate education.
When the training is unchanged for immense periods of time, traditions are passed on intact to the next generation. But when what needs to be learned changes quickly, especially in the course of a single generation, it becomes much harder to know what to teach and how to teach it. Then students complain about relevance; respect for their elders diminishes. Teachers despair at how educational standards have deteriorated, and how lackadaisical students have become. In a world in transition, students and teachers bother need to teach themselves one essential skill—learning how to learn.
Except for children (who don't know enough not to ask the important questions), few of us spend much time wondering why Nature is the way it is; where the Cosmos came from, or whether it was always here; if time with one day flow backward, and effects precede causes; or whether there are ultimate limits to what humans can known. There are even children, and I have met some of them, who want to know what a black hole looks like; what is the smallest piece of matter; why we remember the past and not the future; and why there is a Universe.
Every now and then, I'm lucky enough to teach a kindergarten or first-grade class. Many of these children are natural born scientists—although heavy on the wonder side, and light on skepticism. They're curious, intellectually vigorous. Provocative and insightful questions bubble out of them. They exhibit enormous enthusiasm. I'm asked follow-up questions. They've never heard of the notion of "a dumb question."
When I talk to high school seniors however, I find something different. They memorize facts. By and large, though, the joy of discovery, the life behind those facts, has gone out of them. They're worried about asking "dumb questions;" they're willing to accept inadequate answers; they don't pose follow-up questions; the room is awash with sidelong glances to judge, second-by-second, the approval of their peers. They come to class with their questions written out on a pieces of paper, which they surreptitiously examine, waiting their turn, and a oblivious of whatever discussion their peers are at this moment engaged in.
Something has happened between first and twelfth grade, and not just puberty. I'd guess it's partly peer pressure not to excel (except in athletics); partly that the society teaches short-term gratification; partly the impression that science or mathematics won't buy you a sports car; partly that there is so little expected of students; and partly that there are few rewards or role models for intelligent discussion of science and technology—or even for learning for its own sake. Those few who remain interested are vilified as "nerd," "geeks," or "grinds."
I also find many adults are put off when young children pose scientific questions. It is critical that this cannot happen. Why is the Moon round? Why is the grass green? What is a dream? How deep can you dig a hole? When is the world's birthday?" Too often, many teachers and parents answer with irritation or ridicule, or quickly move onto something else: "What did you expect the Moon to be, a square??" Children soon recognize that somehow this question annoys the grown-ups. A few more experiences alike, and the child is lost to science. Why should adults pretend omniscience before 6-year olds, I am baffled. What is wrong with admitting we don't know something? Is our self-esteem that fragile?
— Carl Sagan, The Demon-Haunted World: Science as a Candle in the Dark
What causes depletion of cortisone in your body?
And what does it mean?
--70.40.144.203 00:39, 8 August 2006 (UTC)[reply]
Where did you hear this, one of those diet pill commericials? --mboverload@ 00:47, 8 August 2006 (UTC)[reply]
That's stress hormone cortisol, suggested to be what makes you fat. — [Mac Davis] (talk)
Cortisone is not used up, per se. Instead, it is usually too low when the adrenal gland has been damaged or destroyed, such as in Addison's disease or Waterhouse-Friderichsen syndrome. Alternatively, it may never form (21 hydroxylase deficiency) or may be turned off by taking steroids such as prednisone. When you have too little cortisol (the name for the chemical in your body), things like low blood pressure and low blood sugar result. Hope this helps! InvictaHOG 00:49, 8 August 2006 (UTC)[reply]
Solar Dynamo soon?
Today, In a short fun discussion with a professor we talked a little about various types of sci-fi armagedon movies and laughed at their unsupportive / ridiculous events (if you want to call it that). Eventually, one of my peers mentioned about a possible Solar_dynamo happening in the near future (not sure if they're correct). In addition, they mentioned that it "the electricity will go out". I was wondering if that was just a rumor or it could really happen. If so, how devistating can it be? Thanks in advance for the output!
Did you read the "solar dynamo" article? If you're worried that the "solar dynamo" might happen soon then be very afraid, because it's already happened. It is describing a process that is at work in the sun all the time. Now perhaps what your schoolmates meant was a reversal of the sun's polarity, or whatever, and so um, "causing the electricity to go out." If they mean that it'll cause everything that uses electricity on earth to stop working, well, that's not what the solar dynamo will do. 71.113.119.102 01:32, 8 August 2006 (UTC)[reply]
Hmm... the part about the sun's polarity shifting sounds much more correct. I may have just read the wrong thing on the article of the sun. Thanks for the info! Is there any possibility when this might happen? because unless i have been misinformed again (or taken something out of context) they mentioned it happens every 11 years?
--Agester 01:50, 8 August 2006 (UTC)[reply]
Yes, every 11 years (give or take a few). It is associated with increased solar activity (e.g. solar flares, coronal mass ejections), which can be bad for satellites, but only rarely affects life here on Earth. It is possible for a very active sun to affect power grids and cause short lived outages, but that generally only happens when the grid is already overtaxed, and mostly at high latitudes where the Earth's magnetic shielding is weaker. See: geomagnetic storm. Dragons flight 03:16, 8 August 2006 (UTC)[reply]
Could we tap into this energy source? DirkvdM 10:07, 8 August 2006 (UTC)[reply]
Is it worth it for a couple of days every eleven years. PhilcTECI 12:18, 8 August 2006 (UTC)[reply]
*blink* you are suggesting solar dynamo only exists a few days every 11 years? If you wanted to tap the energy of it all the time, all you would need is a coil large enough to induct the energy. I will leave coil size up to you (hint, the field exists at the extremities of the sun) --Jmeden2000 15:10, 8 August 2006 (UTC)[reply]
Ok but the suns magnetic field is on an 11 year cycle, at the end of which it completely breaks down and starts again. PhilcTECI 23:08, 8 August 2006 (UTC)[reply]
A magnetic field isn't only useful when it changes...
Calculating speed from gravity.
Let's say I drop an object, from the window of the 2nd or 3rd floor, like a ball, and I use a stopwatch to measure the duration of fall. Once the object hits the ground, I stop the stopwatch and now have the time it takes to accelerate via a distance. With the time, using d = .5att (or d = (1/2at^2)), where a = ~32.1 feet/second^2. Plug in time t, and you now have the distance. But is there a way to calculate the speed at which the object hits the ground? (Like in miles/hour). Or am I missing some variables here?
For example, if t = 5.5 seconds, then I would already have reached freefall acceleration of 120 mph. Thanks. NealIRC
There are several ways - a*t gives you the velocity (this assumes no air resistance, as does your calculation). Another way would be to assume conservation of energy - the starting potential energy (m*g*d) = 1/2 * m * v^2. Raul654 01:50, 8 August 2006 (UTC)[reply]
For a constant acceleration (as with gravity, as long as you neglect air resistance) your final velocity is equal to your initial velocity (zero, if your object is dropped from rest) plus the acceleration multiplied by elapsed time.
vfinal = vinitial + a·t
Acceleration is the rate of change of velocity with time, right? 32 ft·s-2 tells you that your velocity is changing by 32 feet per second, each second. Every second that goes by, your velocity changes by 32 feet per second, until your smack into the ground. (Dang, I wish you guys would use metric...). TenOfAllTrades(talk) 01:55, 8 August 2006 (UTC)[reply]
TenOfAllTrades is correct; but the just to clarify: time is continuous, e.g. you don't speed up all 32 ft/s at the end of each second. You are gradually accruing additional velocity, so you can have fractional seconds. (after 1.5 seconds, you would have v=48 ft/s ). Nimur 19:57, 8 August 2006 (UTC)[reply]
Hey, not bad after 35 yrs not using it! I think I deserve a prize! But I dont think Ill be getting one 8-(--Light current 02:54, 8 August 2006 (UTC)[reply]
:-) Here Light, I give you this marble, , as reward for remembering Earth's gravity. Dragons flight 03:08, 8 August 2006 (UTC)[reply]
Hey thanks babe! I'll treasure it!--Light current 03:16, 8 August 2006 (UTC)
Oh I see -- that brings me back to earth 8-))! --Light current 03:19, 8 August 2006 (UTC)[reply]
Accurate value
That is if you are at the vertical geodetic datum; the value decreases as your elevation increases. However, if you need that level of accuracy, you're perhaps better off using G anyways... Titoxd(?!?) 02:54, 8 August 2006 (UTC)[reply]
That value is some kind of average. In St. Petersburg, Florida the actual acceleration of an encyclopedia dropped in a vacuum is closer to 9.79 m/s2. --LambiamTalk 07:43, 8 August 2006 (UTC)[reply]
I agree. The acceleration due to gravity is a naturally occurring phenomenon that can be measured, it's not some abstract concept that is amenable to an arbitrary definition. JackofOz 12:09, 8 August 2006 (UTC)[reply]
Sure, it's a defined constant, used as a reference value. The actual number will depend on your location and altitude. It's useful if you need an exact value (this component was stressed under an acceleration of 200 g, the samples were centrifuged at 100,000 g for 2 hours) so that you can make comparisons. It's just like how one atmosphere of pressure is usually pretty close to (but not exactly equal to) the actual atmospheric pressure at a given place and time on Earth. TenOfAllTrades(talk) 12:38, 8 August 2006 (UTC)[reply]
Spooky. Shades of those crazy 19th century Americans who tried to legislate for the precise value of π. JackofOz 22:37, 8 August 2006 (UTC)[reply]
Pi
Pi is a whole number equal to pi. Its all the other numbers that are wrong. 9-)--Light current 22:55, 8 August 2006 (UTC)[reply]
>> Actually Pi does have an precice value it is equal to 4* the intergal from 0 to 1 of dx/(1+x^2). Most people are just not used to this as a numbering system; never the less it is a precice value--Aaron hart 07:52, 9 August 2006 (UTC)[reply]
Exactly my point. Trouble is it makes counting and integers etc a bit difficult. I believe it can alos be expressed as the result of many other integrals not to mention infinite series. 9-(--Light current 13:31, 9 August 2006 (UTC)[reply]
>>But back to the real question, it does not only apply to the gravitational value of the earth, Acutally it is the two masses one the earth and the other the object accelerating towards it, the small object acctually accelerates the earth towards it, but this is an old theory, acutally gravity is due to the curviture of space-time due to mass, i.e. the moon accutally travels in a staight velocity through space-time that is curved due to the mass of the earth! This is rather complicated and has is due to the fact that matter in space-time is considered as a perfict fluid thats most important characteristic is its energy distribution. Thus the gravitational behavior of any body is determined by its total energy constent, but this is almost imposible to demonstrate by experimentation--Aaron hart 08:01, 9 August 2006 (UTC). I do not believe that it is totally understood![reply]
Pain Threshold
Is there a way, or are there multiple ways, for a person to increase his or her pain threshold significantly?
Do you mean threshold before pain is subjectively experienced, or threshold before you're willing to confess to anything they want to hear? The use of morphine can help, also with the latter. But most analgesics are controlled substances in most countries. There is the gate control theory of pain, which may give some ideas. Also read our article on Pain management. Some people are helped by meditation, others by hypnosis. There are claims that one can train to endure pain, but I've no specific knowledge about the effectiveness. --LambiamTalk 07:26, 8 August 2006 (UTC)[reply]
I'm reminded of Lawrence of Arabia, who was able to hold his hand over a lighted candle without flinching. When someone said "Doesn't that hurt?", he said "Of course it does, but I don't mind the pain". JackofOz 12:06, 8 August 2006 (UTC)[reply]
Great movie - I believe the quote is "Of course it hurts. The trick is not minding that it hurts" --Bmk 14:24, 8 August 2006 (UTC)[reply]
Thanks for the correction. My other favourite (hopefully not mis-)quote about pain is Oscar Wilde: "I can stand anything except pain". JackofOz 22:34, 8 August 2006 (UTC)[reply]
Did anybody ask the candle "Does't that stink ?" (guess its answer). Any threshold, anyway, is modified by regular use. See sudoku, Mithridate and athletic training.-- DLL .. T 18:31, 8 August 2006 (UTC)[reply]
No, that's not right. Even when it's utterly frustrating, Sudoku is always pure pleasure. JackofOz 22:34, 8 August 2006 (UTC)[reply]
The Buddha was known to be great at not caring about pain. But keep in mind, pain is something your body does to you to keep itself alive. You feel pain from a burn so you don't do it again. You feel pain if you get a rock thrown at your head so you don't let it happen again. — [Mac Davis] (talk)
A lot of top class martial artists are known for having colossal pain thresholds. So mine would be discipline, its not about not feeling the pain, but knowing its not the pain thats hurting in you. PhilcTECI 22:56, 8 August 2006 (UTC)[reply]
Well, in that context, the pain is indeed hurting you. But, if you don't want to get kicked in the ribs again, it is best to try to ignore it so you can, as my instructor likes to say, 'move yo' ass out the way of sommin' that's comin' straight atcha! ' That is my take on it. --69.138.61.168 16:46, 9 August 2006 (UTC)[reply]
You cannot significantly elevate your pain threshold by non-invasive or nor-pharmacological means. But you can quite effectively increase your pain tolerance by physical, cognitive and affective techniques (in addition to taking the drugs which can temporarily increase the threshold for pain). I assume you were asking about tolerance since all the comment above is about it. I see WP has no article describing any of the two quite opposite ways of describing the experience of pain. Hmm, I don't feel like work right now, but I've put up a pain threshold stub-plus for you. And will look to pain tolerance soon. Which should then at least answer your question. --Seejyb 01:01, 10 August 2006 (UTC)[reply]
Nanotechnology - Nano Coatings and ultra thin films - Market trends
Hi All,
Please provide me some information or relevant links to facts and figures related to technology trends and market trends in the area of Nano coatings and ultra thin films in relation to Nanotechnology.
Any help regarding this will be gratefully appreciated.
Have you looked at our article on Nanotechnology? I assure you, it's quite the relevant link. --ByeByeBaby 06:27, 8 August 2006 (UTC)[reply]
and it might be a good idea to check the also relevant homework. Xcomradex 08:22, 8 August 2006 (UTC)[reply]
Multiple time dimensions
I have a very hard time understanding the concept of multiple time dimensions.
Since our lone time dimension forms a timeline, i suppose having 2 of them could be described as a "timeplane", where the current time could be described with 2 coordinates.
How does an object move through the timeplane? Is its time trajectory random, or can it be controlled? Or does it move in all directions at the same time, creating an infinite number of timelines in the plane?
How is moving forward in the first time dimension different from moving forward in the second one?
The idea of multiple time dimensions is referred to at 2T-Physics. Itzhak Bars is a (if not the) recognised expert on this.
Leaving redlinks to answer questions is pretty unhelpful. PhilcTECI 13:40, 8 August 2006 (UTC)[reply]
Anon might be referring to Second Temporal Dimension, which is not a very helpful stub. (Sorry but I'm not even going to try to get my head round this question. Hopefully someone brighter will be along shortly.)--Shantavira 15:29, 8 August 2006 (UTC)[reply]
The idea is inconcievable to us as we are from a universe with a one dimentional timeframe (or timeline in this case) so you won't be able to percieve what the question is referring to if thats what you are trying to do. Since our time line is 1 dimensional, it can only go two ways, and for some reason i don't know, not being a physicist, this side of the speed of light it always goes forwards. Which is fair enough, because being a 1D timeline, if you go from one end to the other, you pass through all the possible timelines, however with a 2D(or more) timeline if you go from one end to the other, either:
You miss out a large portion of the possible times,
Time periodically jumps back on one of the axis
Several times are happening simaltaneously
Objects navigate the time plane/space/whatever randomly
Or some other obscure thing I haven't thought of, or we cant understand. Someone with a knowledge of these things please comment. PhilcTECI 18:39, 8 August 2006 (UTC)[reply]
Redlinks can be hellauseful because both "2T-Physics" and "Itzhak Bars" seem very nice google search terms. Dr. Bars' home page suggests another: Two-Time Physics. Sorry, the math is too much for me to write even a stub on it. Sp(2,R) Gauge symmetry acts on phase space, yeah, right, got it, thanks a heap. ;-) Weregerbil 18:30, 8 August 2006 (UTC)[reply]
How about if the second temporal dimension is viewed as movement into parallel universes ? For example, if you throw a ball 100 feet in our universe, perhaps you throw it 99 feet in another universe, and 101 in another. As you proceed to parallel universes further in this second temporal direction from ours, you might drop the ball, not even ever have tried to throw it, or you may not exist at all. StuRat 19:54, 8 August 2006 (UTC)[reply]
At best, this is highly-theoretical physics mathematics; more realistically, it is pseudo-science. Well, good luck wrapping your head around it; I don't know that it will be productive. Nimur 20:06, 8 August 2006 (UTC)[reply]
The parralell universe theory considers all possible universes, not specifically universes with 3 spacial dimensions and 1 time dimension, so inevitably the universe will have been created at some point with more than one time dimension, and as far as I am aware it is impossible for these universes to interact anyway, as there is nothing between them, no spacial or time or any other dimensions, so they are not connected to ours by time or space. 172.206.180.165 20:34, 8 August 2006 (UTC)[reply]
Chiropractor titles
A local Chiropractic clinic has opened in my town and the 2 chiropractors there, as stated on the door have BScs and MChiros but before their name the have Dr.
Now, is the title of doctor achieved with the MChiro or have the chiropractors just assumed the title?
Moffo
(added title) Please use the "ask a question" link at the top of the page to ask a new question - then your question will get its own topic heading. In partial answer to your question, you should read the section on "Chiropractic education" in our article on chiropractors --Bmk 16:21, 8 August 2006 (UTC)[reply]
May I add that I live in the UK. I apologise about the title thing.
I'm fairly sure that they would have to have doctorates. An MChiro is a masters degree, so they wouldn't have got the title of doctor with it, although they may well have obtained the masters before the doctorate (or after, but that's unlikely). If they aren't really doctors they could get in trouble under the trade descriptions act.
If you live in the UK, you may be interested to know that even the majority of UK medical "doctors" aren't real doctors (in that they do not have a doctorate like an Doctor of Medicine). Most have only Bachelor of Medicine and Surgery degrees. They are officially titled "Registered medical practitioners" in the UK but, whether they have a higher doctorate or not, are afforded the courtasy of using "doctor" as an honorary title. That notwithstanding, it is not illegal to call youself a "Dr" without a higher degree in the UK. You can only get in trouble if you try and use the title in a fraudulant way. Whether chiropractors calling themselves "doctors" without a suitable qualification are committing fraud is open to debate. Rockpocket 19:41, 8 August 2006 (UTC)[reply]
Your comment about the majority of UK doctors not being "real" doctors assumes that the title is supposed to indicate possession of a doctorate. According to [16], which quotes the OED, the usage of "doctor" as a term for someone who treats illnesses or diseases goes back to (at least) 1377.--71.246.9.240 03:50, 10 August 2006 (UTC)[reply]
My 'assumption' is based on the root of the word. As our article, Doctor (title), tells us:
"Doctor means teacher in Latin. It has been used continuously as an honored academic title for over a millennium in Europe...its primary designation is a person who has obtained a doctorate (that is, a doctoral degree)...From the nineteenth century onward, "doctor" has been popularly used as a synonym for "physician" in Anglophone and many other countries; this term is commonly used as a title of address for physicians, whether or not they hold a doctorate."
I was surprised when signing on with a new dentist (in the UK) to see that he described himself on his business card as "Dr" so-and-do, despite only having bachelor's and/or master's degrees in dentistry. --rossb 08:11, 10 August 2006 (UTC)[reply]
Cost/Price of an EMD SD40-2 Locomotive in 1972
What was the price tag of an EMD SD40-2 diesel-electric locomotive in 1972, the first year they were offered?
I'm going to Google this, only because I am mildly amused by such a question. I wonder if you have already Google'd. But I am now legitimately curious... did you think anyone on the Reference Desk would know this off-hand?!? Or did you just want to solicit us to perform the google-search FOR you? Nimur 20:26, 8 August 2006 (UTC)[reply]
And I imagine that you were the one who asked the exact same question here. The responses estimate from $100,000 to $500,000. Nimur 20:32, 8 August 2006 (UTC)[reply]
And according to the IRS, though they insist this is not official, many EMD SD40s are re-built and can re-designated as SD40-2 models for tax purposes. This would significantly reduce the cost. Nimur 20:38, 8 August 2006 (UTC)[reply]
There's nothing wrong with asking - the reference desk isn't really for giving answers to questions - it's for helping people answer their own questions by pointing them in the right direction. In that spirit, i'm going to link to our insanely detailed article on the EMD SD40-2. I was rather surprised that we had an article on this, and even more surprised when it didn't mention the price :( Sorry - I tried --Bmk 20:45, 8 August 2006 (UTC)[reply]
Sorry. I didn't mean to sound aggressive, I meant to sound surprised. This is an awfully specific fact; I imagine the only way to find out such a detail is to personally contact a train salesman from 1972. Even then... Nimur 20:49, 8 August 2006 (UTC)[reply]
No problem, sorry for the reaction! It is a remarkably obscure fact, as facts on this desk go :) -Bmk 22:03, 8 August 2006 (UTC)[reply]
This fact may seem "obscure" and insignificant. However, it serves as a basis for comparing the cost/price in real terms against current locomotive models, and is therefore fairly important. Any info you can add on this would be greatly appreciated. The nearest I've come to the price is approximately $400,000, but an exact figure would carry more weight.
Moths and 100% Nylon
Will Moths eat 100% Nylon fabric, if it is used as a protective covering for clothing?
Thank you Anna Porter
I dont think they like nylon so its a good protector for clothes. Alternatively, you could use a platic carrier bag. I found that works.--Light current 19:17, 8 August 2006 (UTC)[reply]
Indeed, they won't. It is the hatched larvae that munch on your clothing, which they only do after burrowing inside the wool. A moth won't deposit her eggs on a smooth dense fabric. The larvae cannot digest nylon and need animal hair like wool or felt to survive. --LambiamTalk 19:25, 8 August 2006 (UTC)[reply]
... and that's no myth :--) JackofOz 22:26, 8 August 2006 (UTC)[reply]
Dont you mean moth? 8-)--Light current 23:35, 8 August 2006 (UTC)[reply]
No, it is a moth, just not a myth. Pay attention please! DirkvdM 09:10, 9 August 2006 (UTC)[reply]
Id get that lisp seen to if I were you! 9-)--Light current 13:04, 9 August 2006 (UTC)[reply]
Lithp? What lithp? JackofOz 13:30, 9 August 2006 (UTC)[reply]
uk Frogs
How long does a small frog grow into its full size (uk)--86.139.143.214 19:41, 8 August 2006 (UTC)[reply]
I assume since you asked about time in the UK, that you want it in UK units, like fortnights. :-) StuRat 19:57, 8 August 2006 (UTC)[reply]
HEY now, no anti British comments please! 8-)--Light current 22:12, 8 August 2006 (UTC)[reply]
Did I get off on the wrong track ? (Or should I say the wrong dual carriage-way ?) :-) StuRat 04:01, 9 August 2006 (UTC)[reply]
Well, you seem to have have put your foot metre in it. DirkvdM 09:25, 9 August 2006 (UTC)[reply]
What a display of xenophobic ignorance. PhilcTECI 11:26, 9 August 2006 (UTC)[reply]
First I'm being called anti-xenophobic and now xenophobic again. At least I'm wonderfully unpredictable, just the way I like myself. DirkvdM 18:35, 9 August 2006 (UTC)[reply]
No, no its all done the best possible taste as Kenny Everett plaing 'Cupid Stunt' used to say.--Light current 14:20, 9 August 2006 (UTC)[reply]
Frog life cycles are discussed on the main page. Specifically, "Most temperate species of frogs reproduce between late autumn and early spring. In the UK, most common frog populations produce frogspawn in February, although there is wide variation in timing. Water temperatures at this time of year are relatively low, typically between four and 10 degrees Celsius. Reproducing in these conditions helps the developing tadpoles because dissolved oxygen concentrations in the water are highest at cold temperatures. More importantly, reproducing early in the season ensures that appropriate food is available to the developing frogs at the right time." This suggests between 4 to 6 months from fertilization to frog-form. Nimur 20:01, 8 August 2006 (UTC)[reply]
Which is between 8 and 10 fortnights ; but the tadpole life may be quite long before you have a perfect small frog. -- DLL .. T 20:10, 8 August 2006 (UTC)[reply]
I officially declare this "irrelevant answer day" on the Science ref desk. I haven't carefully surveyed the other posts, but on this one there are about ten irrelevant comments for every helpful one. :) don't stop, though. It's much more fun to read. --User:bmk.
Incidence of Down's Syndrome decreasing?
The article on Down Syndrome mentions that a kind of 'eugenics by abortion' is happening, where parents undergoing prenatal genetic screening are opting to abort rather than give birth to a Down's child. I've been wondering if this has resulted in a decrease in the incidence of Down's children in the world. In the future, will Down's and other testable genetic disorders be seen only in families that are members of religions that are against abortion? Adambrowne666 23:09, 8 August 2006 (UTC)[reply]
Eeep. This is certainly a touchy subject. I'm sure somehow, someone's response will infuriate the internets :/ Anyway. I wonder if your hypothesis is accurate. It does makes sense to me - not just for Down Syndrome, but for numerous other genetic ailments. I wonder if 'eugenics by abortion' is a loaded phrase; but, yes, I tend to agree that this effect would occur, weeding out genetic problems in family-lines who would prefer no child to a diseased child. Another factor is the recessive gene effect (I'm not a biologist so I don't know if this applies to Down Syndrome, but certainly might for other diseases/conditions). It's possible that bad genes are passed through the hereditary line without ever expressing themselves. Perhaps this could continue for many generations; but the rate of occurence would be decreased. I guess a followup question might be whether it is testable. Nimur 23:44, 8 August 2006 (UTC)[reply]
Abortion would have an effect on the prevalence, but not the incidence, of Downs Syndrome. There's no "gene" for Downs Syndrome, it results from a chromosomal abnormality, and that abnormality generally arises anew rather than being inherited from someone who already has it. On the other hand, a societal trend to have children early, rather than late, in life, would decrease both incidence and prevalence of Downs Syndrome. - Nunh-huh 23:52, 8 August 2006 (UTC)[reply]
While Down's Syndrome is genetic, I don't think it's normally inherited. That is, it's caused by an error in chromosome replication in the sperm and ova of genetically healthy mothers and fathers. However, the tendency toward having errors in chromosome replication may indeed have a genetic component, so this trait could be reduced by abortions.
In a recessive genetic disorder, in unrelated mothers and fathers, the rate of appearance of the disease (phenotype), is proportional to the square of the portion of people with the recessive gene (genotype). That is, if 1 in 10 people carry the gene, then 1 in 100 will have the disease. StuRat 23:55, 8 August 2006 (UTC)[reply]
Is it impossible that a tendency to develop chromosomal abnormalities can itself be inherited? -Wfaxon 00:06, 9 August 2006 (UTC)[reply]
[ec]
For DS in particular, there's probably not a large "eugenics" effect simply because it's not a simple genetic trait, such as a sickle cell-type recessive mutation, but rather a trisomy of chromosome 21. DS patients rarely have children, so that pathway of genetic perpetuation is limited. It's very possible that parents of DS children have other genetic polymorphisms that may increase the incident of a nondisjunction event, and if these parents produce other viable children those polymorphisms will persist in the population.
The most important risk-factor associated with DS, however, is maternal age at conception. Modern technology has allowed far more 35+-year old women to have children, and far more reporductively-challenged couples to conceive. If I were to hazard a guess, the increased number of children born to older mothers probably offsets the screening effects, but I've not found anything on PubMed just yet that supports my guess or with a clear indication on increased or decreased prevalence of DS. -- Scientizzle 00:07, 9 August 2006 (UTC)[reply]
The total prevalence for trisomy 21 is increasing as more older women are having children, in some places as much as 2-fold over the last 20 years. However, there is a divergence between live births and diagnosed cases (At least in European areas with abortion) due to pregnancy termination. One recent study showed that 77% of Parisian fetuses diagnosed with trisomy 21 were aborted. The reference is "Dolk H, Loane M, Garne E, De Walle H, Queisser-Luft A, De Vigan C, Addor MC, Gener B, Haeusler M, Jordan H, Tucker D, Stoll C, Feijoo M, Lillis D, Bianchi F. Trends and geographic inequalities in the prevalence of Down syndrome in Europe, 1980-1999. Rev Epidemiol Sante Publique. 2005 Nov;53 Spec No 2:2S87-95. PMID 16471148" InvictaHOG 00:30, 9 August 2006 (UTC)[reply]
Though I don't think this applies at all in the case of DS, one of the stranger side-effects of prenatal abortion is that you have a high chance for a "dysgenic" effect (if we want to use those terms) because heterozygous populations can reproduce more often without getting double-recessive children. In Cyprus, for example, prenatal testing drastically allowed for the decrease in the prevalence of thalassemia (a condition similar to sickle-cell anemia) through pregnancy termination. Prenatal testing though has allowed heterozygous parents to have more children than the would otherwise: children with the double-recessive condition not only drained their family resources, but made them very anxious about having more children; after it was possible to have children without the double-recessive, parents felt more free to have more children. The irony here is that they've basically taken the Mendelian ratios and knocked the double-recessive option out of the picture: now the only options are AA, Aa, and aA. Which means that 2/3 of the children actually born are probably heterozygous, and there are probably more of them due to the larger family size, which a eugenicist of the old school would see as an issue (you are in fact leading to an increased incidence of the trait in the population than you would otherwise, even if the prevalence is decreased). At least, that's my interpretation of it. (I am not a eugenicist, mind you; I don't necessarily think that one needs to lower incidence if working on prevalence will do the job.) --Fastfission 01:11, 9 August 2006 (UTC)[reply]
Excellent answers, thank you. Adambrowne666 04:00, 9 August 2006 (UTC)[reply]
Down syndrome can be inherited - see Robertsonian translocation. Increases in "spontaneous" nondisjunctions (as noted above, due to older women giving birth) may have a larger effect on the prevalence. But inherited DS cases should be going down due to abortions. zafiroblue05 | Talk 04:25, 9 August 2006 (UTC)[reply]
Familial Down syndrom, as our article says, only accounts for 2-3% of all cases of Down Syndrome. There is still no reason to suspect that inherited incidence would go down via abortions (again, since most cases of DS are not caused by people exhibiting DS—the translocation would still presumably be passed along in the non-aborted, non-DS children who are born to such families). Indeed it may even rise, based on similar to logic to what I posted above. It is one of the grim ironies of "eugenics" that attempts which focus on prevalence may lead to solutions of increased incidence. --Fastfission 16:18, 9 August 2006 (UTC)[reply]
I find it curious that the questioner apparently assumes that anyone who discovered their in utero child had Down Syndrome would automatically want to end the pregnancy, unless a religious conviction precluded that. I could foresee many pro-choice people choosing to carry such pregnancies to term, perhaps based on experience with Down children, or an attachment formed with the child before its birth. --Ginkgo100talk · contribs · e@ 18:18, 9 August 2006 (UTC)[reply]
I didn't assume that at all. I was referring to the phrase 'eugenics by abortion' in the Down's article, and suggesting it as a tendency that might reveal itself over several generations. Adambrowne666 21:28, 9 August 2006 (UTC)[reply]
Why do they have 3 terminals? one positive, one negative.. and the third? pogetive? 00:49, 9 August 2006 (UTC)
I would think the third ground. — [Mac Davis] (talk)
Could be for charging. Not sure--Light current 02:55, 9 August 2006 (UTC)[reply]
>> I believe it is because the battery contains more than one cell, not sure but probably two. This has advantages for longer life; such as using two 6 volt batteries instead of two 12V for an R.V. but Im not sure as to why. Also lithium ion batteries last between 300-500 charge and discharges, They store best at 40% charge in a refrigerator. They should not be completly discharged, even a full charge is harder on them, Try to cycle 80% percent charge and run down to 20%, charge back to full or 80%. The worst possible senerio is as in laptops or portable DVD players is to keep them pluged in to an outlet, this keeps the battery fully charged at a high temp. You will get longer life out of them if you take out the battery, while using an A.C. Plug.--Aaron hart 09:24, 9 August 2006 (UTC)[reply]
My li-ion batteries only have two. PhilcTECI 11:24, 9 August 2006 (UTC)[reply]
I would take them back to the store for a refund!--Light current 11:46, 9 August 2006 (UTC)[reply]
No, theyr'e meant to, they are made to be the same size and shape as a pair of AAs, and fit into the same terminals. So there is not terminal for any more pins. PhilcTECI 11:57, 9 August 2006 (UTC)[reply]
Is that mentioned in Genesis? I didn't know they had terminals in Adam's day. :--) JackofOz 13:28, 9 August 2006 (UTC)[reply]
Lithium ion cells require precise monitoring during charging to prevent them from over heating and being damages or catching fire. The third terminal is often for a battery charge monitoring (a.k.a. gas gauge) IC inside the pack. This PDF (bq27000.pdf) is the datasheet for one of the ICs manufactured by Texas Instruments if you look at the sample circuit on the second page you'll see they make connections for PACK+, PACK-, and HDQ. HDQ is the communications port in this case. On other packs (NiMH/NiCd, for example), the third pin might be used to measure the voltage of a single cell for controlling the charge cycle and checking for an overdischarged/damaged pack condition. It could also, theoretically, be connected to a thermistor to measure the pack temperature, which is another method to control the charge cycle in non-lithium chemistries. —Bradley 15:04, 9 August 2006 (UTC)[reply]
Excellent response. Isopropyl 18:43, 9 August 2006 (UTC)[reply]
Makes sense, did I mention my 2 termianl ones were non-rechargeable (hehe, turned out to be quite improtant) ;-) PhilcTECI 21:52, 9 August 2006 (UTC)[reply]
Sexual power
how can i measure my sexual power(without having sex)?.
Interesting question. What is sexual power, and how would you measure it if you were having sex? --Allen 03:56, 9 August 2006 (UTC)[reply]
i'm guessing a large magnet, a coil of wire... Xcomradex 08:24, 9 August 2006 (UTC)[reply]
>> possibly by the heat produced??--Aaron hart 08:47, 9 August 2006 (UTC)[reply]
Hey i m serious...i m gettin married in few weeks..n i dont know i m capable enough ..i want to measure...isn,t there any method to measure?
There isn't an objective measure. There's a lot of fake stuff, and people like to pretend they are better than they are. It isn't a competitive sport. My tip: if you love one another, and are honest with each other about what you know, and what you like, you'll work it out and have fun. And practice makes perfect: you have the rest of your lives to practice. Notinasnaid 08:55, 9 August 2006 (UTC)[reply]
>> SORRY,, but on the serious side, you need to comunicate and both of you will learn; it will just get better and better, don't worry about the first time, relax it will help, as stated earlier you have the rest of your lives to practace--Aaron hart 09:29, 9 August 2006 (UTC)
thanks it means to became relax is the main point to increase your power....is there any excercise like swimming or jogging that help me strenthen my power...i want to make my...rock solid...so is there any excercise????[reply]
Doctors say dont smoke, dont drink (too much), eat well & healthily, take some excercise, get plenty of rest, dont worry etc. If you do all that already and still cant get it up, I would pop along to the doctor for a quick check up!--Light current 11:14, 9 August 2006 (UTC)[reply]
I don't know what you mean by "sexual power". It isn't like how good in bed you are is a direct factor of how strong you are, and there is no simple exercise that will increase that (though sex is an athletic activity—when done right!—so being in shape can help things). Your primary goal should be enjoying it, and making sure your partner enjoys it. This has more to do with talking to them about what they enjoy, and trying new things, than any sort of "sexual power". Take it slow, try to have fun with it, and always remember to think of your partner, and you won't be able to go too wrong. If you are having trouble with erectile dysfunction, that is unrelated to your "power"—a doctor would be the best person to consult about that, they see cases about that all the time, it is not a big deal. --Fastfission 11:42, 9 August 2006 (UTC)[reply]
As a woman, I can say the aphorism is true: it's not size (or "power") that matters, it's how you use it. Your new wife will be happy for you to learn how to use it together. I doubt she cares about your "power," whatever you mean by that. --Ginkgo100talk · contribs · e@ 18:20, 9 August 2006 (UTC)[reply]
Or : it aint what you got, its the way that you use it! Or alternatively: It dont mean a thing if it aint got that swing?? --Light current
If your concern is the satisfaction of your future partner, then being relaxed about it is more important than anything else. The "first time" is rarely very good, because you have to learn to understand each other's desires and to read each other's signals. Create a relaxed and romantic atmosphere, take your time, and be generous with both compliments and caressing and other forms of affectionate touching. --LambiamTalk 01:36, 10 August 2006 (UTC)[reply]
>>My only other sugestion is don't drink to much alcohol, high blood pressure pills will effect sexual function, and expecially anti-depresents to a much higher degree than reported, other than that you might want to talk to a doctor and try viagra oc ciallias, it even helps people with no problem at all, and just may be the confidence boster you need.
Disaster forecasting
How are hurricanes and tornadoes forecasted now? Can they be predicted by measuring wind speeds near the coasts?
Hurricanes can be generally tracked for days in advance. Problem is that people always cut the track too close and don't account for standard errors (ie. it suddenly takes a turn). With tornadoes, one can only track a severe thunderstorm that *could* produce a tornado. Most of the time, people do not take these warnings seriously (since they happen a lot). --Zeizmic 13:11, 9 August 2006 (UTC)[reply]
A large percentage of current day weather forecasting (including hurricanes and severe thunderstorms that can produce tornadoes) relies on numerical weather prediction, which involves using complex computer models to simulate the atmosphere and try to predict how systems will progress. Obviously observations such as the wind speeds you mention are also important, especially the upper air measurements we get from radiosondes and the overall views that weather satellites provide that Light current mentions. So, summarizing, observations and rules of thumb from experience are still important in modern day forecasting, but the way we can simulate the atmosphere using today's supercomputers are very important in forecasts. EWS23 (Leave me a message!) 20:16, 9 August 2006 (UTC)[reply]
camera
What are the functions of diaphragm and aperture in a camera?
There is more to 'focusing' than just focus. Check the main Camera article to start. For more details, F-stop, aperture, exposure (photography) and focal length will help; and if you want some more theory, optics or refraction may also be useful. In short, they control how much light can enter the camera- this means a different image is formed. Nimur 13:46, 9 August 2006 (UTC)[reply]
In an attempt to give an actual answer, the diaphragm regulates the aperture (the hole through which the light enters the camera). There is a constant trade-off between the amount of light and the sharpness of the image. The bigger the hole, the more light will fall into the camera, meaning that you can use a shorter exposure time, resulting in less movement blur (movement of either the subject or the photographer's hand). But a bigger hole also means that any point on the subject will be projected on several points on the sensor or film (forming a little circle), also causing an unsharp image. Perfect sharpness would be achieved with an infinitely small hole, but then the exposure would have to last infinitely long, and most people can't stand still that long. DirkvdM 18:47, 9 August 2006 (UTC)[reply]
As the aperture becomes very small, diffusion decreases sharpness. A pinhole camera mav an aperture as small as, literally, a pinhole, but putting a pinhole sized aperture in a good camera would greatly lower the sharpness. There is not a "constant tradeoff" with smaller aperture producing greater sharpness. See lens test data for various lenses. It is very definitely untrue the "Perfect sharpness would be achieved with an infinitely small hole.." One such site, http://www.hevanet.com/cperez/results.html says "Theoretic Diffraction Limits
Theoretic diffraction limits at f/22 for green light is 68 lines/mm.
By comparison a lenses f/32 diffraction limit is 47 lines/mm. If you look at the test results for all the lenses tested at that f-stop they very nearly ALL perform at that limit. See also a discussion of diffraction, circles of confusion and depth of field in books by Ansel Adams.Edison 19:14, 9 August 2006 (UTC)[reply]
Ships Floating
Hello,
Ive searched the Wikipedia database but couldnt find anything. I woudl like to find a detailed article on how/why ships are able to float and not sink in the ocean. A coin will sink but a huge ship made of steel wont, I knwo it has to do with probably bouyancy? but is there a detailed article in Wikipedia explaining this?
Yep - the buoyancy article has the answers. Basically, the trick is that the ship is hollow! It's mostly air. On average, it's less dense than the water, even though its outside is made of metal. If the ship were solid metal, it would sink just like a solid-metal coin. --198.125.178.207 14:47, 9 August 2006 (UTC)[reply]
PS: Of course, that's only if the ship is floating in an ocean of water. If it were floating in a sea of mercury, it would stay afloat even if it were solid steel. Because mercury is just that cool. But ignore me - i'm just confusing the matter. --198.125.178.207 14:48, 9 August 2006 (UTC)[reply]
If you made a double-hulled ship with a material like Styrofoam between the hulls (to prevent that space from ever flooding), and the volume of Styrofoam was large enough to float the ship, you really could make an unsinkable ship. StuRat 18:11, 9 August 2006 (UTC)[reply]
You wouldn't need the hull either, just the styrofoam. There's a guy in Amsterdam who has built his house on a styrofoam platform and the island keeps expanding as he collects more of the stuff.
At the other extreme, there's a houseboat opposite my house that is made of concrete. Any material will work, as long as the average density (including the air inside the boat) is lower than that of water. DirkvdM 18:58, 9 August 2006 (UTC)[reply]
If you don't put the Styrofoam inside something fireproof, it can all burn up, and then the ship could sink. StuRat 23:08, 9 August 2006 (UTC)[reply]
If you used styrofoam passengers, they would never drown, either. But they don't pay as well as the human ones. --198.125.178.207 19:35, 9 August 2006 (UTC)[reply]
I like Styrofoam people, they always seem so light-hearted. Although, I must admit, many of them are also air-heads. :-) StuRat 23:08, 9 August 2006 (UTC)[reply]
Ok since we seem to get this question every while, is it just me, or is it not because the ship weighs less than the water it would displace if submerged and no water could enter the ship. It seems pretty obvious to me, ships float because they are lighter than water (including the air they contain). Am being stupid or are other people? PhilcTECI 21:56, 9 August 2006 (UTC)[reply]
That is correct. An equivalent way of stating that fact is to say that the boat will float if its average density is less than that of water. --Bmk 22:42, 9 August 2006 (UTC)[reply]
raw bacon
Is raw bacon safe to eat?
Depends on what country the pig came from. — [Mac Davis] (talk)
I Wouldnt try it. I think it, like lots of meats, has bacteria on the surface (if not inside)--Light current 17:08, 9 August 2006 (UTC)[reply]
Baste it in something like lime or pineapple juice. Of course, some people say that is "cooking" the meat. --Kainaw(talk) 17:23, 9 August 2006 (UTC)[reply]
Meat can transmit certain diseases. Undercooked pork sometimes contains the parasites that cause trichinosis or cysticercosis. Chicken is sometimes contaminated with Salmonella enterica disease-causing bacteria. The recent outbreak of bird flu has stimulated global concerns over public health. Cattle tissue occasionally contains the prions that cause variant Creutzfeldt-Jakob Disease.
Is bacon pork or ham? TITQ.--Light current 17:29, 9 August 2006 (UTC)[reply]
According to a site I found, trichinosis is very rare in the United States. Cysticercosis is rare, although less so. I wouldn't recomment eating raw bacon, but at least in the United States (and probably other developed countries where the meat is factory-farmed rather than home-farmed), the risks don't appear to be huge. --Ginkgo100talk · contribs · e@ 18:30, 9 August 2006 (UTC)[reply]
Yeah, the pork industry in America today is so clean you can eat it raw. That's why I asked what country the pork is from. Anywhere else it is probably dangerous. — [Mac Davis] (talk)
Anything can cause diseases. Raw beef can cause Creutzfeldt-Jakob, so shouldn't one eat steak tartare? Raw fish is also a Dutch delicacy. But I have never heard of raw pork, so I suppose there must be a reason for that. DirkvdM 19:03, 9 August 2006 (UTC)[reply]
Note that cooked beef can also cause Creutzfeldt-Jakob, AKA bovine spongiform encephalitis, AKA mad cow disease. The protein which causes mad cow isn't alive, so isn't killed by cooking it. Only incineration works. StuRat 23:20, 9 August 2006 (UTC)[reply]
So we should all incinerate our meat before eating it? I like my steak well done so that sounds good to me! --Light current 00:01, 10 August 2006 (UTC)[reply]
Eating [any] raw meat that isn't pure Grade A or wasn't especially bred to be eaten raw (like in sushi, for example) is like playing Russian Roulette. Eat enough of it, and you are eventually going to get something in your body that you don't want in there. --69.138.61.168 07:20, 10 August 2006 (UTC)[reply]
Flammable
Is vegetable oil or grease flammable?
Yes. Many kitchen fires are caused by oil and grease catching fire on the stove. (Use baking soda & not water to put out the flames!) -- Scientizzle 18:50, 9 August 2006 (UTC)[reply]
Or you could put a lid on it (literally, I mean, on the pan - I'm not being rude this time). Water will worsen the fire, ironically. If you mix petrol and water 2:1 (or was that 1:2?) you get a brighter flame than from just petrol. So why isn't water mixed with petrol in combustion engines? DirkvdM 19:08, 9 August 2006 (UTC)[reply]
It would rust your block and break your pistons?--Light current 00:24, 10 August 2006 (UTC)[reply]
Brighter flame != more energetic. --Jmeden2000 19:14, 9 August 2006 (UTC)[reply]
If I remember correctly, brighter flames indicate insufficient oxygen consumption. Clearer flames are hotter. Isopropyl 19:19, 9 August 2006 (UTC)[reply]
I'd guess that the water causes the oil to spread out on a surface, thus giving more surface area for combustion, which might result in a brighter flame. There could be other processes at work though --User:bmk
The main reason not to add water to an oil fire is that it causes flaming bits of oil to splatter around the room, which is enough to ruin anyone's day. StuRat 23:14, 9 August 2006 (UTC)[reply]
What is dam3?
Hi. I am trying to find a definition of dam3, or dam cubed, in relation to the measurement of volume. The "3" in this case is superscript, indicating cubed. This term is used in the volume measurement of the storage capacity of resevoirs and dams, but it also seems to be used to describe flow. I am trying to find a definition, but Google and Wikipedia don't seem to have anything. I have never heard of this term, but the reports that I am reading use it extensively. Thanks
Could one of these cells be used to power a magnetoplasmadynamic thruster capable of carring up to five hundred tons?68.120.69.0 21:06, 9 August 2006 (UTC)[reply]
Until now I was not familiar with MCFCs, so I apologize if this is not accurate. Also, I'm not sure what you mean by "carrying" five hundred tons. Do you mean could it "provide five hundred tons of force"?
If so, I'd say the answer is certainly not yet. Plasma rocket design is a very new science, and there are a lot of possibilities, but it seems that the state of the art (according to NASA here) plasma thrusters are operating at about 1 Megawatt and producing 22.5 pounds of thrust. On the "supply" side, this site from the DoE shows a picture of a 1 megawatt MCFC plants, and it looks pretty big. No matter what the scaling law of power vs. thrust is, to scale 22.5 pounds up to 1 million pounds (500 tons) would result in a mammoth MCFC plant. I don't know what applications you have in mind, but I don't see it happening any time soon. But this is all my quick and dirty research, so feel free to correct me (as always). I'm curious though, why do you ask? MCFC seems like an odd power source for space propulsion. --Bmk 21:52, 9 August 2006 (UTC)[reply]
Well I was reading the fuel cell page and there was a table showing that this cell could produce 100MW so I thought that may be effeicent enough power for electric thruster of some kind. A link from the MCFCs page showed one at a fair and it wieghs around 20 tons so I was just curious if it produced 100MW and possibly if it did, could it produce enough lift to lift itself and the thruster along with other things.
Ah, I see. Interesting idea. This might work in space - where the power plant is weightless, and you're only working against inertia (I believe plasma thrusters require a vacuum to operate, anyways). However, I still see it as impractical, even in space, because there is probably a large energy requirement to melt the salt electrolyte to get the plant started. --Bmk 22:50, 9 August 2006 (UTC)[reply]
Swallows, Magpies, and Trains, oh my o:
If an eastbound Swallow takes off for Capistrano flying at a velocity of 299792457 m/s and starts to exibit relativistic effects shortly after crossing the Rocky Mountains, while at the same time a westbound train takes off from Cleveland, assuming that the westbound train is accelerating at a constant rate of 24 feet per hour per second, from a start velocity of 24 feet per leapyear. Assuming that the swallow is around 8 ounces and carrying a one pound coconut, and assuming that said swallow has exactly the nessesary drag coefficiant in order to maintain the air-speed velocity at a constant value, and mandating that said swallow does not attempt to deviate in a southerly direction while following the sun, and assuming once again that the train is of sufficient size and velocity that it does observe any quantum effects, and also assuming that it has a nice racing stripe painted on the side, exactly how many flavors of Baskin-Robbins low fat frozen yogurt does the snack car on the train have?--172.163.29.21 22:09, 9 August 2006 (UTC)[reply]
I just went through Cleveland on a train last night. I do believe the answer to your question is 0: I saw no frozen yogurt on the snack car. digfarenough (talk) 22:41, 9 August 2006 (UTC)[reply]
The question is invalid as it contains a spelling error!--Light current 00:35, 10 August 2006 (UTC)[reply]
An African or European swallow? User:Zoe|(talk) 01:57, 10 August 2006 (UTC)[reply]
Spectrum of the elements
Hello,
I'm looking for the spectrum of the elements. There used to be a website that had a java program that would present each element's spectrographic signature. You would click on the periodic table and the spectrum of that element would appear. What I would really like is that the spectrographic signature of each element also include all the infrared and ultraviolet lines. Does Wikipedia have this anywhere? I've searched and found nothing. Would Wikipedia like to include such a thing?
Thank you very much,
Michael King
michaellouisking@yahoo.com
I can't tell from the question if you're looking for the website that you mentioned. If so, I think I've found it. It's here. And it is really cool! Y'all should check it out. It would be neat if wikipedia included spectra in each element's article. Sounds like a job for...you! Or me if I decide to put the time in. Just make sure you understand the copyright issues, if you do decide to make it a project. --Bmk 00:34, 10 August 2006 (UTC)[reply]
ants/anatomy
please could some one tell me where i can go to find a piture of the internal anatomt of an ant i have gone to dozens of sites and can not find one Thank you
ISO and ANSI standards are copyright, and generally not available without cost. This is how the standards bodies cover their running costs. Sometimes the final draft can be found, but this often changes in the standard. It's worth checking with different standards bodies, as the same standard may have quite different charges. Notinasnaid 09:06, 10 August 2006 (UTC)[reply]
Marshmallow experiment
In the marshmallow experiment described under Deferred gratification, what was done to control for exogenous factors? It seems to me these might include:
Advanced/delayed development. As I understand it, not all four-year-olds have a clear concept of time, or even enough language, to understand the deal that was being offered. Conceivably, those slower learners who could not understand it might be less likely to wait, even if they had the same deferred gratification, and also less successful in later life.
I can't picture many 4 year olds who couldn't understand this simple proposition. They also were told that they would be notified when the 20 minutes was up, so they didn't need to have any sense of time. StuRat 06:41, 10 August 2006 (UTC)[reply]
Gender, race, etc. Suppose that for as-yet-unknown genetic reasons (I think that in four-year-olds, we can eliminate social conditioning), the group that were able to wait included a greater proportion of white children, more boys, or some other group that statistically earns more money than average. It would follow, then, that they would be more successful in later life, even if deferred gratification did not cause this greater success.
It could also be argued that, if more successful gender and racial groups demonstrated a superior ability to wait for gratification at age 4, then that may be why those groups are more successful. StuRat 06:41, 10 August 2006 (UTC)[reply]
Sugar addiction. From what I've read, widely varying degrees of sugar addiction have been detected in four-year-olds. I have also read that sugar addiction impairs learning and can lead to health problems (e.g. hypoglycemia) later in life. Both these things would negatively impact "success" down the road. I suspect that how long a child could wait would have had at least something to do with the strength of their sugar cravings.
Could be. There was also a child who refused to eat any marshmallows because their mother didn't allow it. StuRat 06:41, 10 August 2006 (UTC)[reply]
I also doubt if the sample size was large enough, say 1100 kids, for a 3% margin of error over a 90% confidence interval. StuRat 06:41, 10 August 2006 (UTC)[reply]
If these factors were not controlled for, how sure can we be that the results are valid? Perhaps the presence or absence deferred gratification at the age of four has nothing to do with whether it is present in adulthood. NeonMerlin 04:31, 10 August 2006 (UTC)[reply]
I don't have access to a research library, but perhaps someone can look this up. The original paper is: Shoda, Y., Mischel, W., Peake, P. K. "Predicting adolescent cognitive and self-regulatory competencies from preschool delay of gratification: Identifying diagnostic conditions". Dev. Psychol. 26(6), 978–86, Nov. 1990. --LambiamTalk 04:54, 10 August 2006 (UTC)[reply]
Looks good, I added that ref to the article. StuRat 06:41, 10 August 2006 (UTC)[reply]
You can read all the abstracts here. I get the impression that the wikipedia article might overstate the authors conclusions.--Peta 05:02, 10 August 2006 (UTC)[reply]
amyotrophic lateral sclerosis
Could someone with als also have peripheral neuropathy? Also, if this person fell because of the neuropathy, could the als worsen faster?
thank you
jimblab
Peripheral neuropathy could always occur coincidentally in someone with ALS. However, this is not typical and not part of the syndrome. ALS might seem to worsen in times of illness, such as after a fall or with pneumonia. I'm not sure that the disease is actually progressing - more that the neurologic deficits are exaggerated and more pronounced. InvictaHOG 06:59, 10 August 2006 (UTC)[reply]
Waterlilies and scum
I get an oily scum on my garden fishponds at certain times of year (for instance now - I live in the UK). I've been told that this is caused by the waterlilies, but I haven't been able to find a good explanation as to why this should be. Any suggestions? --rossb 07:55, 10 August 2006 (UTC)[reply]
, as reward for remembering Earth's gravity. Dragons flight 03:08, 8 August 2006 (UTC)
![[17]](https://upload.wikimedia.org/wikipedia/commons/a/a9/Ant_worker_morphology_corrected.svg){kind=link}