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December 5

Einstein's Theory Of Relativity

Can you explain to me what The Theory Of Relativity states?

"Everything is relative".

Seriously, did you read the theory of relativity article? ~Amatulić (talk) 00:32, 5 December 2008 (UTC)

I thought spacetime intervals were absolute.--GreenSpigot (talk) 02:05, 5 December 2008 (UTC)

Actually Einstein himself thought "relativity" was a bad name for it, because what really matters about his theory are the few invariants that muck around with a relative universe. --98.217.8.46 (talk) 02:08, 5 December 2008 (UTC)

You may want to see Introduction to special relativity or simple:Special relativity. — DanielLC 17:15, 5 December 2008 (UTC)

Designing difficultiy

Why is it much harder to design/propose something simple then something complicated? —Preceding unsigned comment added by 79.75.83.53 (talk) 01:53, 5 December 2008 (UTC)

Simplicity requires being able to see through to the very essence of what one is getting at and to strip away everything inessential to that point. To do that requires knowing said essence and what is essential—a great amount of complete understanding that, especially on the first go of things, is usually quite hard to attain. When I write papers, the first draft are always overstuffed and complicated. Only after lots of revisions do I see what the core essence of it is and try to strip away everything else. Even then, it's hard to do it—there's a temptation to include all sorts of extra bits, just because they have grown on one. --98.217.8.46 (talk) 02:12, 5 December 2008 (UTC)

"I didn't have time to write a short letter, so I wrote a long one." (attr. Mark Twain, orig. by Blaise Pascal). DMacks (talk) 05:13, 5 December 2008 (UTC)

I don't think that's always true...but certainly it sometimes is. A car is more complicated than a skateboard - I would certainly never claim that a car was easier to design than a skateboard. But to design a car that's significantly simpler than current cars (and performs the same functions) would be extremely hard. It goes both ways.

I design software systems (computer games) - and very often, I come up with an initial design for some part of the system - but I may regard it as too complex and then have to put in more effort to simplify it. But if I saw that my design was actually too simple (and therefore couldn't do some of the things it needed to do) - it could easily take significant effort to make it sufficiently complex. Adding simplicity is very satisfying though...particularly if simplifying something makes it easier to make...the best computer programmers are lazy people!

SteveBaker (talk) 03:18, 5 December 2008 (UTC)

Keep design as simple as you can, but not simpler :) - manya (talk) 04:11, 5 December 2008 (UTC)

It think it should be "complex is easier than simple ... for equivalent functionality". If you started to attach an engine, breaks, air conditioning, leather seats, safety systems, etc. to the skateboard, things start to change in the simple/complicated analysis. I think one of the reasons that complex is easier than simple relates to whole epicycle issue- if you need to add functionality, it's easiest to just tack it on top of the already existing structure. Do that enough times, and you end up with a rats' nest. It then takes a lot of time, effort, and ingenuity to pare back the complexity and cleanly integrate the functionality at the base level, rather than having it be a tacked-on afterthought. -- 128.104.112.113 (talk) 17:31, 5 December 2008 (UTC)

Speed though time

At what speed do we all progress through time? —Preceding unsigned comment added by 79.75.83.53 (talk) 01:55, 5 December 2008 (UTC)

"Speed" is a concept which requires reference to time (e.g. miles per hour), so it's not a physically sensible question. The idea that time itself could have a speed is an illusion brought on by things like film technology which apparently let us manipulate the speed of time, but this is just an visual illusion related to how vision works. Time does not work the way it appears in a cinema. --98.217.8.46 (talk) 02:03, 5 December 2008 (UTC)

Yes but we all travel forward through time dont we? So, at what speed do we go. Its a reasonable question —Preceding unsigned comment added by 79.75.83.53 (talk) 02:10, 5 December 2008 (UTC)

One second per second. Algebraist 02:11, 5 December 2008 (UTC)

We don't travel through time. Time is not physical space. We use the metaphor of physical space to help us make sense of it with our clumsy human brains, but that is not what time is. (There is a relationship between time and physical space—spacetime—but that is not what time is.) --98.217.8.46 (talk) 02:14, 5 December 2008 (UTC)

Time is the 4th dimension. We travel through it. At what speed? —Preceding unsigned comment added by 79.75.83.53 (talk) 02:23, 5 December 2008 (UTC)

I told you already. What is the problem? Algebraist 02:34, 5 December 2008 (UTC)

You can think of time as the 4th dimension - but if you start imagining it's "just like another spatial dimension" then you're missing what's going on. Forget that analogy - it sucks and it's confusing and doesn't fit reality well. There are three spatial dimensions and one time dimension...don't roll them together - it just doesn't work.

But you only "move" when you are changing where you are in both space and time simultaneously. When you are travelling at 30 miles per hour - that means that as you travel along the time dimension - you also travel along the space dimension. If you plotted your 'time' and your 'distance' as points on a graph, the "speed" would be the slope of that graph. So you don't have speed in one axis at a time - speed is something that requires change in both the time dimension and one or more of the distance dimensions. If you don't move in the spatial dimension - the line is flat and your speed is zero - if you could somehow move in one of the distance dimensions without moving in time - the line would be at right angles to the time axis and your speed would be infinite.

So beyond the interesting philosophical issue of whether we should consider time to be the 4th dimension - it's truly a meaningless question. 03:06, 5 December 2008 (UTC)

According to Brian Cox, when we stand still in all three spacial dimensions we are moving through the fourth dimension (time) at the speed of light, and if we move very fast in any of the space dimensions we "use up" or transfer some of that "speed" in the forth dimension to the space dimension,so move more slowly through time.Trevor Loughlin (talk) 03:05, 5 December 2008 (UTC)

That's a bit garbled, but more or less true. See special relativity. However, from our own perspective we are always at rest, hence moving forward in time at one second per second (which translates, in this slight garbling, as the speed of light). From the point of view of observers moving at high speeds relative to us, we are going forward in time at much less than one second per second. Algebraist 03:08, 5 December 2008 (UTC)

Thanks a lot for this! Now I'm always at rest. How do I get to the bathroom? Wanderer57 (talk) 06:21, 5 December 2008 (UTC)

Cause it to move towards you. Duh. Algebraist 06:27, 5 December 2008 (UTC)

Oh good idea! Except with time moving at the stupendous rate of one second per second, I'm not sure I can hold out that long. Wanderer57 (talk) 07:21, 5 December 2008 (UTC)

I disagree that "from our own perspective we are always at rest". You can adopt whatever perspective you like. I personally don't think of myself as always at rest. I'm at rest as I write this, but when I go walking outside I'll be moving. I adopt the Earth (including all the stuff attached to it, like buildings and trees) as my reference body most of the time, because it's a more useful reference body than my body for most purposes.

Some people have gotten the idea that special relativity requires you to use rest frames. They get into horrible difficulties with what should be very simple problems involving accelerating objects because they believe that they have to work with uncountably many reference frames, one for each point on the object's worldline. Sometimes they even claim that special relativity can't handle acceleration at all, which is like saying that Cartesian coordinates can't handle circles. So I try to discourage the you-are-always-at-rest perspective because I think it interferes with learning special relativity. -- BenRG (talk) 15:47, 5 December 2008 (UTC)

There is no way to answer this question (except with jokey tautologies like : 'Sixty minutes per hour'). The word speed is defined as distance per unit time. What you're asking for is "distance (through time) per unit time" which doesn't make sense, because that just simplifies down to "time per time", which is silly.

"Speed" is what you get when you compare a movement against time. Comparing something with itself doesn't give you a usable answer.

So, I guess you could say that the answer to your question is "1". (no units, just 1). But that doesn't really mean anything. Better to say that there is no answer. APL (talk) 15:12, 5 December 2008 (UTC)

No, better to say that it is an ill-formed question, a question that does not permit valid answering. It's like asking how many pancakes it takes to make a banana. The question is nonsensical. --98.217.8.46 (talk) 15:33, 5 December 2008 (UTC)

There are two different concepts of time in physics, "time as a fourth dimension" and "time as a measure of change". As far as we can tell, though, there's only one kind of time in the real world. You can think of it as a fourth dimension or as a measure of change, but not as both at once, because that would be like having two independent dimensions of time or two independent time parameters. When you ask "how fast do we move through time", you're making that error. You have time as a dimension (which you call "time"), and you also have time as change (implicit in the verb "move" or "progress"), and in order to "move through time" they would have to act independently. You can think of the world as stuff moving through space, or as stuff in spacetime that just is, but you can't think of it as stuff moving through spacetime.

Interestingly enough, reconciling the two notions of time is one of the biggest problems with combining general relativity and quantum mechanics, the so-called "problem of time". Special relativity can function acceptably with either kind of time, but general relativity has problems with time as change, and quantum mechanics has problems with time as a dimension. -- BenRG (talk) 15:47, 5 December 2008 (UTC)

I think some of the recent questions on this ref desk (i.e. the apparent path of mercury question and this one) are arising from people watching the recent horizon program in which Prof. Brian Cox states that we are travelling through time at the speed of light and the passing of time is thus the result of us moving through the time dimension at this speed. See: http://www.bbc.co.uk/programmes/b00fyl5z (This programme is possibly only viewable in the UK) Jdrewitt (talk) 15:50, 5 December 2008 (UTC)

That sounds likely. What he's talking about is the Four-velocity. It is the tangent vector to the World line in Minkowski space-time and represents rate of change in space and time coordinates along the path. This four-velocity is always equal to the speed of light. From that follows that if a particle moves at near the speed of light, its rate of change in time is almost zero, and that if the particle is at rest, it moves at speed c in the time direction. So in that sense, we're progressing at the speed of light through time. This is complicated further when you'r working in a metric as the world line article points out. EverGreg (talk) 16:12, 5 December 2008 (UTC)

Carbon monoxide poisoning

Our article states that undiluted cigarette smoke contains roughly 30,000 ppm of carbon dioxide monoxide (typo). Under the Toxicity header, our article also has a nice little section dedicated to the side effects of CO poisoning and says that "12,800 ppm (1.28%) [causes] Unconsciousness after 2-3 breaths[citation needed]. Death in less than three minutes."

Okay...I'm a bit confused. If undiluted (yeah, I know cigarettes have filters usually, but do they really take that much CO out? Or what if you smoke an unfiltered cigarette?) cigarette smoke contains 30,000 ppm of carbon monoxide, and LESS THAN HALF of that concentration will kill you in less than three minutes, why aren't there a lot more dead cigarette smokers? And even with the breathing in [moderately] unpolluted air in between cigarette hits, why doesn't this acute carbon monoxide poisoning cause severe headaches or nausea, like it supposedly does at 1600-3200 ppm? I'm just a bit confused is all. --71.98.25.115 (talk) 02:36, 5 December 2008 (UTC)

I suspect "undiluted cigarette smoke" means without air you suck through the cigarette, which would be most of the gas you inhale when you takea puff. It could do with some clarification in that article though. --fvw* 02:41, 5 December 2008 (UTC)

Yeah - I think that's the point. If your lungs were COMPLETELY full of air with 12,800 ppm of CO - it would be bad. But you are breathing a mixture of smoke with 30,000ppm of CO and fresh(ish) air that didn't come through the cigarette. The key word is "undiluted" - if you had several lungfuls of undiluted cigarette smoke - you'd be in deep trouble...but in reality, it's diluted...so it's not so terrible. Of course it's still terrible - there are hardly any chemicals that come out of a cigarette that aren't doing you harm. It's just a matter of degree. SteveBaker (talk) 02:47, 5 December 2008 (UTC)

Careful - carbon monoxide and carbon dioxide are different - it's the monoxide which is highly toxic, dioxide is harmless until you get up to pretty high concentrations. You meant "monoxide" in your first sentence. --Tango (talk) 12:11, 5 December 2008 (UTC)

Okay I see now. Just curious then, what would the typical concentration of CO be in the average hit of a cigarette? It must be pretty low, because people don't typically complain of headaches and nausea after smoking in my personal experience. --71.98.24.41 (talk) 18:52, 5 December 2008 (UTC)

Is this a legitimate scientific study?

http://www.medicalnewstoday.com/articles/64474.php —Preceding unsigned comment added by 216.239.234.196 (talk) 13:29, 5 December 2008 (UTC)

It appears to be a report about an essay about the effectiveness of an herbal product written by an organization devoted to promoting the use of herbs. An essay is not a scientific study. - Nunh-huh 13:37, 5 December 2008 (UTC)

That summary contained a link to this PDF file on the "study": [herbalgram.org/files/pdfs/5594COLD-fX.pdf], but the link doesn't work. This makes me rather suspicious. StuRat (talk) 14:04, 5 December 2008 (UTC)

I did a search and did find a seemingly valid study: [1], which does conclude that it's safe and effective (although they only claim a 13% reduction in the chances of getting a cold, which isn't all that great). StuRat (talk) 14:15, 5 December 2008 (UTC)

Is "HerbalGram" a peer-reviewed scientific journal? Looks like an in-house publication of a pro-herbal group... --98.217.8.46 (talk) 15:30, 5 December 2008 (UTC)

I don't know about them, but the study they sight seems to be legit, unless they've just made the whole thing up, of course. StuRat (talk) 17:48, 5 December 2008 (UTC)

"HerbalGram" is not peer-reviewed. However the original study is published in the Canadian Medical Association Journal, here. Axl ¤ [Talk] 10:35, 6 December 2008 (UTC)

Short answer: yes, it does appear legitimate. Axl ¤ [Talk] 11:31, 6 December 2008 (UTC)

But also note that a single study is not usually sufficient for a robust result. In this case, I also note that some of the authors work for the company that make the herbal remedy in question. That does not mean that it is false, but it's easy for bias to slip into it - if only by doing 20 studies and publishing the one that will show a 95% significance by chance. --Stephan Schulz (talk) 23:24, 6 December 2008 (UTC)

It bothers me that (according to that article) the manufacturers, the researchers, the peer-reviewers and the authority claiming the advance are ALL 'acknowledged' herbal/natural diet supplement 'experts'. Becoming an 'expert' in this field requires almost no scientific training or formal qualifications - so how do we know that any of these people know what they are talking about? I'd want to see some studies done by mainstream groups...the history of herbal medicines is littered with bogus claims, fraudulent studies, you name it. This one might be OK - but I'd definitely be sceptical. With herbal medicines, the barrier for testing for side-effects and counter-indications is very low indeed - that's because they mostly don't actually do anything. When you find a herbal medicine that actually DOES do something - then is the time to be worried because you have something with some powerful effect on the body - but almost no adequate testing for side-effects, drug interactions - nobody calculating the safe dose - nobody checking that it's not dangerous to children, pregnant women - no regulation of how much is administered, and so forth. The ones that "work" are the ones you should avoid the most!! SteveBaker (talk) 05:10, 8 December 2008 (UTC)

Energy

Do you have a better idea of what energy is, other than the 'ability to do work' or the fact it is scalar and is some form of attribute? My guess is no, but hey, I might be surprised. —Cyclonenim (talk · contribs · email) 14:29, 5 December 2008 (UTC)

It's the conserved charge corresponding (under Noether's theorem) to the symmetry of the laws of physics under time-translation. Algebraist 14:42, 5 December 2008 (UTC)

LED Grow Lights

Are there any LEDs that are created specifically for use as grow lights?

Would it work to simply use an array of red and blue emitting LEDs that were not created specifically for growing plants?

To put this another way, is this idea promising enough to be worth trying, or is it way off base? Thanks, Wanderer57 (talk) 16:35, 5 December 2008 (UTC)

Google results. --LarryMac | Talk 16:45, 5 December 2008 (UTC)

I've seen UV LED flashlights on ebay. Cool for seeing unspeakable stains on hotel walls! Not sure about growing plants. --70.167.58.6 (talk) 17:59, 5 December 2008 (UTC)

Yes, I have one of those UV LED flashlights. I've taken it on airliners, to examine the seat cushions, blankets, and pillows. I decided later, that what I don't know won't hurt me.

It seems to me that you could create your own grow light by mixing red, yellow, green, blue, white, and UV LEDs in a proportion that approximates a solar spectrum. ~Amatulić (talk) 20:51, 5 December 2008 (UTC)

Addendum: The light-emitting diode article cites this article, which indicates that simple red LEDs make good grow lights for plants. ~Amatulić (talk) 21:04, 5 December 2008 (UTC)

I'll bet those LED grow lights will be popular with those who grow marijuana crops indoors, as heat from regular grow lights is one of the ways cops find them, using infrared cameras. StuRat (talk) 00:43, 6 December 2008 (UTC)

I imagine not being harassed by cops is a plus for anyone who gardens indoors, even honest folk. APL (talk)

Yes, Lots. Typically they use some assortment of LEDs that emit on a specific frequency of red, and some LEDs that emit on a specific frequency of blue. Searching Google for "LED Grow Lights" will give you lots of hits.

If you're more of a do-it-yourself-er. Here are a couple of entries from the Make blog : [2] [3] I've been thinking about making a couple small ones on timers for indoor potted plants that don't get enough light.APL (talk) 00:53, 6 December 2008 (UTC)

Is it possible to smell your own breath?

I see people doing "breath checks" by exhaling into a cupped hand help up to their face. Barring any serious infection or chronic odor, is it possible to really tell if your breath is funky? --70.167.58.6 (talk) 17:52, 5 December 2008 (UTC)

This is a standard way of checking your breath. See "Smelling and tasting"(2002, or [4]. Another is to [5] [6] lick the back of your hand]. There is also the "Fresh Kiss HC-201," an electronic device which gives a reading ranging from "undetectable" to "very bad halitosis." Edison (talk) 19:44, 5 December 2008 (UTC)

Apparent contradiction in information about tumours

Hello; I heard on the radio that tumours grow exponentially, but that they grow more rapidly at the beginning than later. That appears like a contradiction to me. Can someone please clarify this for me? Thanks! Leptictidium (mt) 19:54, 5 December 2008 (UTC)

I'll hazard an educated guess, based on what I've been told by doctors, in relation to uterine fibroid tumors.

A tumor grows exponentially because each cell continues to reproduce. If you have a doubling of cells every constant time interval, you have exponential growth. However, the tumor cells need oxygenated blood supply to survive. At some point the growth becomes too large for the blood to sustain it, and cells start dying off, slowing the growth.

So yes, the growth is exponential, but a limiting factor takes over after a certain point. That's my guess at explaining the apparent contradition you heard. ~Amatulić (talk) 20:47, 5 December 2008 (UTC)

That's well put, and correct to my knowledge. - Draeco (talk) 00:19, 6 December 2008 (UTC)

Wikipedia really does have an article (or at least, section) on everything: Logistic curve#In medicine: modeling of growth of tumors. --Tango (talk) 01:03, 6 December 2008 (UTC)

Thanks, your answer has been very useful! Leptictidium (mt) 08:25, 6 December 2008 (UTC)

December 6

Lysosomes in plants

I am wondering if plant cells have lysosomes like animal cells do. Half the resources I've looked at say "no", and the other half say "yes". ♫Deathgleaner 04:45, 6 December 2008 (UTC)

Without any expertise in this, I get the impression that "lysosyme" is used as a name both for a group of enzymes and the organelle containing them. In [7] for instance, a plant lysosyme is referred to as an enzyme. This may be a reason for the discrepancy between your sources. EverGreg (talk) 16:00, 6 December 2008 (UTC)

It's important to be quite careful here — the lysosome is an organelle, while lysosyme is an enzyme (or a class of similar enzymes). TenOfAllTrades(talk) 16:24, 6 December 2008 (UTC)

By lysosomes, I do mean the organelle with the hydrolytic enzymes in it that digest foreign and malfunctioning organelles and particles. ♫Deathgleaner 22:51, 6 December 2008 (UTC)

The reason for the discrepancy is that it's still something of a debated question in plant biology. Part of it is that there are still questions about the biology, some of the rest of the controversy stems from disputes about nomenclature. Here's a good summary (tilted towards the "yes" side) of the issue: [8]. Deeper searching will find you a great deal of hemming and hawing about 'vacuoles', 'lytic compartments', and other lysosome-like structures. TenOfAllTrades(talk) 16:24, 6 December 2008 (UTC)

Stabilised Pool Products

I use a floating device in my pool which dispenses chlorine on a slow release basis, which needs replacing once a month. The packing indicates that the product is stabilised, and goes on to warn that the excessive use of stabilised pool products can lead to low levels of free chlorine and a build up of nasties. My understanding is that stabilisers such as cyanuric acid "lock" the chlorine in so that it doesn't break down too quickly in harsh conditions such as sunlight. My real question then: if I use this product on an ongoing basis, replacing the monthly refill when required, at what point will I reach a critical point of being over-stabilised, when the product will cease to work properly ? Is the regular flushing and replacement of a small % of the water (as I do anyway when backwashing) sufficient to keep stabiliser levels low ? Does the stabiliser itself break down over time ? Please provide a generalised response, as I know a scientific answer would require specific data around quantities etc involved.--196.207.33.197 (talk) 05:24, 6 December 2008 (UTC)

According to the introduction in this patent [9] (US6843925) the cyanuric acid is a by-product of chlorine tablets that slowly dissolve, releasing chlorine. An excessive concentration of the acid causes a "chlorine lock" where added chlorine becomes ineffective, probably because it can't be dissolved in the water. This then means bacterial and algae growth since chlorine is continuously removed from the water e.g by evaporation. The remedy is to change the water as you mention yourself. The patent also mentions that there exists a water test to detect if the adverse "chlorine lock" has occured, and this water test is what would answear your question conclusively. :-) EverGreg (talk) 15:50, 6 December 2008 (UTC)

I don't like high chlorine levels in my pool (who does?!) - and this effect is very noticable. If you first measure the pH of the water in your pool with a decent test kit (using fresh chemicals - test kits "go off" after a few months and lose accuracy) - and add pH+ or pH- chemicals until the pH is PERFECTLY right (not just within the limits shown on the test kit...better than that) - then you can use MUCH less chlorine and still keep the pool clean. I measure the chlorine level and have experimented with the levels needed - and the pool can stay shiney clean with much less than the recommended amount IF the pH is kept carefully in check. Those floating dispensers are a very 'blunt instrument' for attacking the problem - it's better to measure carefully and dispense accurately. With a little experience and some careful science (use graphs!) you can know exactly how much pH+ or pH- you need to nudge the pH to the right amount...and you can look at the rate of change of the pH to know how often you need to treat the pool (every 4 days works for me once everything is stable and under control).

I'd like to do this with my hot tub too - but the higher temperature and the much smaller volume of water makes the chemistry change faster than I can keep track of it - so excess chlorine is really needed in that case. SteveBaker (talk) 03:05, 7 December 2008 (UTC)

Partial and total derivatives

Diffrence between partial derivative and total derivative —Preceding unsigned comment added by Chaitanaya mohan (talk • contribs) 13:15, 6 December 2008 (UTC)

Have you read partial derivative and total derivative? --Tango (talk) 15:27, 6 December 2008 (UTC)

Strange phenomenom

I find this quite amazing. Not sure how it works, but I guess it is something to do with the light reflecting properties of older skin. I wonder if there is a practical military application. DriedOut (talk) 14:44, 6 December 2008 (UTC)

If it is true then it is not surprising that they are overlooked. 86.4.188.125 (talk) 15:40, 6 December 2008 (UTC)

Despite this sentence: "[Older women] tell me they feel invisible and they literally are invisible on television", they seem to mean they are symbolically invisible, meaning ignored and given only minor roles. I sometimes feel that those who misuse the word "literally" should be literally drawn-and-quartered. StuRat (talk) 16:36, 6 December 2008 (UTC)

I would go further than that, I feel that they actually should be drawn-and-quartered, not just literally. DriedOut (talk) 17:04, 6 December 2008 (UTC)

How do you actually and not literally draw-and-quarter someone? Jay (talk) 09:30, 8 December 2008 (UTC)

I believe they were making fun of the way the word was used in that article by using it the same way. StuRat (talk) 15:32, 8 December 2008 (UTC)

No, no. It means that older women are not hired for on-screen work. So you can literally not see old women on tv. Lova Falk (talk) 17:24, 6 December 2008 (UTC)

Yes, but it says they are literally invisible on TV, which would mean that even if they were to be on TV you wouldn't see them. You never see Angelina Jolie in my house, but that does not mean that she is invisible, she just never comes here...sigh... DriedOut (talk) 19:02, 6 December 2008 (UTC)

...unless she's invisible too. SteveBaker (talk) 02:57, 7 December 2008 (UTC)

I know it is SO wrong of me to think either of you is serious, but I should probably wikilink the article on metaphor so that we don't go too far with this. And I really hope this is not serious. And I have an invisible Angelina Jolie in my house. Unfortunately, she also comes with an invisible Brad Pitt and 13 invisible third world babies, so it's kind of a bummer... We never get any alone time... --Jayron32.talk.contribs 03:24, 7 December 2008 (UTC)

Inverse relationship between length of work shift and task performance, employee health

I'm having difficulty finding information (quotable, citable material) about the harmful effects of routine, lengthy work shifts on task performance, and also health consequences. The particular case is of instructors (female, ages 18-21) on the staff of a closed residential facility, where the duty shift is 15 hours (08:00 till 23:00, 4-1/2 day work week) minus two meal breaks (midday 1-1/2 hours, evening 1 hour) during which mandatory staff meetings and other work-related activities may be scheduled. The job requires classroom frontal instruction, discipline and supervision of the students, individual meetings with students and supervisors, and materials preparation.* Beyond the effects of cumulative sleep deprivation, the particular focus of my query is about long work shifts. This is to be the substantive basis for a worker-initiated proposal to cut back work hours. The pages on Eight-hour day, shift work, and medical resident work hours don't quite have what I'm seeking. *Note: further details suppressed for confidentiality's sake. -- Thanks, Deborahjay (talk) 16:31, 6 December 2008 (UTC)

I would say that performance most definitely would suffer after 15 hours. How long of a shift is acceptable depends very much on the type of work. Difficult physical work is perhaps the worst, with difficult mental work coming in next. A job you can "do in your sleep", on the other hand, might benefit from 15-hour shifts. I'd expect that instructors losing their voices would be an issue with such a schedule as you described. Noting the break schedule, they should have more, shorter breaks, like 15 minutes every 2 hours, with 45 minutes for lunch and dinner. The shorter breaks would be helpful to the students, as well, to use the bathroom, get a candy bar and coffee, etc. Why the brutal schedule ? Is this the military ? StuRat (talk) 16:46, 6 December 2008 (UTC)

Further to the query: What I'm looking for are studies whose findings indicate benchmarks for balancing length of instruction and supervisory tasks with rest breaks and downtime, to optimize the work without passing some point of diminishing returns by racking up a raw count in hours regardless of quality. This would be supported by evidence of optimal (rather than maximum) length of work shift before physiological changes (response time, attention span) take a dive. The classroom instructional content is academics and skills, but the job involves many additional hours of supervising, meetings, materials preparation, etc. -- Deborahjay (talk) 19:19, 6 December 2008 (UTC)

I found some interesting results by googling study length of work shift productivity. Most of those studies are industry-specific, but taken together they present a formidable argument for promoting shorter work shifts. 152.16.59.190 (talk) 23:52, 6 December 2008 (UTC)

Hours of service seems to have some studies although they are related to driving Nil Einne (talk)

Good pickup, I hadn't seen that page previously; its related concepts provide additional searchable terms ("cumulative fatigue effects" and "industrial or 'time-on-task' fatigue"). -- Thanks, Deborahjay (talk) 22:40, 7 December 2008 (UTC)

Maybe this isn't quite what you're looking for, but the R.S. Means Building Construction Cost Data series (ISSN 0068-3531) has a table in the back linking working time (hours per day and days per week) to production efficiency and payroll cost. So, for example, a schedule of 12 hours per day, five days per week, gives an efficiency of 90% after one week and falls steadily to 60% after four weeks. 198.29.191.149 (talk) 20:27, 8 December 2008 (UTC)

Magically clean acrylic yarn

Craft (magazine) claims that Eco tawashi (reference there), made from 100% acrylic yarn, can "magically" clean dishes without detergent, "similar to microfiber". Is there any truth to that claim? — Sebastian 18:45, 6 December 2008 (UTC)

"Magically" No. When used with water and a reasonable amount of scrubbing, it will clean off a lot of food residue. Plastic scrubbers, stainless steel and other metal scrubbers, coated sponges, etc. have similar effects. Some acrylic fibres are more effective than others for this purpose. I'm told that Phentex (this is a brand name) would be a good choice. CBHA (talk) 19:10, 6 December 2008 (UTC)

Of course my question was not about if there's really magic involved. (Or else I wouldn't have posted it on the science RD.) My question is twofold: Are microfibers so good for cleaning that you achieve the same result without detergent? And if so: Does standard yar (for $2 a skein) really have the same properties? (And what's special about Phentex yarns?) — Sebastian 20:23, 6 December 2008 (UTC)

The cleaning cloths have lots of fibre ends sticking out like a towel. You would have to cut your yarn into lots of little pieces and weave them into a cloth. They work to some extent, but you need detergent if there is a lot of grease involved. Graeme Bartlett (talk) 21:02, 6 December 2008 (UTC)

In the article a teacup is pictured. I am sure a plastic wool cloth (eco tawashi) and a firm grip would make a teacup look clean. It would not clean grease and oil and would not remove some stuff heated on to a steel pot... its 100% acrylic i.e. plastic. ~ R.T.G 02:16, 7 December 2008 (UTC)

Diamonds

Diamonds are very valuable (thus, expensive) rocks. However, once found in their raw form, they need to be cut and shaped in order to have the aesthetic appearance that we "expect" (for example, on jewelry, etc.). After the rock is cut and shaped, what exactly happens to the "shavings" or the rest of the remaining rock? There must be little "shavings" that are left over after the rock is cut and shaped ... no? I assume that these are valuable also? Or are they merely discarded? Thank you. (Joseph A. Spadaro (talk) 19:32, 6 December 2008 (UTC))

They are used for smaller cut diamonds, or for industrial uses like diamond saw grit. Graeme Bartlett (talk) 20:39, 6 December 2008 (UTC)

Thanks. In my original question, I meant the remaining "shavings" after all of the diamonds (large or small) had been cut from the rock. What do you mean by the "grit" of a diamond saw? I looked up that Wikipedia link ... and it only describes the tool used to cut diamonds. Thanks. (Joseph A. Spadaro (talk) 20:46, 6 December 2008 (UTC))

Because diamond is the hardest (naturally occurring) mineral, fragments of diamond which are either too small or too low quality to be used as gems can be incorporated into saws and grinding implements for industrial applications such as cutting through hardened steel. Dragons flight (talk) 22:04, 6 December 2008 (UTC)

You're kidding? They "waste" the valuable diamond shavings for that purpose? Wow. (Joseph A. Spadaro (talk) 22:08, 6 December 2008 (UTC))

Even more, it's been available as a material for decorative applications. Andy Warhol used it in paintings for example, "Diamond Dust Joseph Beuys",[10] "acrylic, synthetic diamond dust, ink on canvas"; and the later abstraction series Shadow series I-V incorporated varying degrees of diamond dust application.[11] I'd like to know the cost of it. Julia Rossi (talk) 22:12, 6 December 2008 (UTC)

Hardly a waste, really. It's not like the trimmings can themselves be cut and sold as diamonds—would you buy a 1/512 carat diamond ring?—and the alternative would be to throw them into the trash, and get nothing for them. Morrand (talk) 22:52, 6 December 2008 (UTC)

Good point, Morrand. I guess a part of me was thinking ... is there not some process by which they can take all the small shavings and somehow bring them back together to create a bigger rock / diamond? I assume not, but that was my thinking. (Joseph A. Spadaro (talk) 00:39, 7 December 2008 (UTC))

It would be way more trouble (and cost) than it would be worth. The shavings are the size of a grain of sand. HalfShadow 01:21, 7 December 2008 (UTC)

To my way of thinking, using diamonds to cut hard materials is a productive use, while making silly rings that some mugger will shoot you to steal is a pathetic waste. StuRat (talk) 01:17, 7 December 2008 (UTC)

It's worth mentioning that diamonds aren't really all that rare. The price is kept high by the fact that there is essentially a complete monopoly on diamonds from the De Beers company. The left-over dust from the cutting & polishing phase is only as valuable as the market is prepared to bear. Since synthetic diamond is now fairly easy to make (especially in the tiny sizes and quantities needed to coat machine tools) - the price for diamond dust has fallen to quite affordable levels. I have a diamond cutting disk for my Makita angle grinder - it cost more than a regular cutting disk - but it wasn't outrageously expensive. Diamond is just carbon - we're close to being able to make LARGE synthetic diamonds that are cheaper than natural ones - and they are chemically and stucturally identical, so the only thing that stops the price of diamond from crashing is the continued advertising from De Beers pushing the idea that these chunks of carbon are somehow 'special' and that only the gift of a natural diamond ring is good enough to get a guy laid. Sad, but true. SteveBaker (talk) 02:52, 7 December 2008 (UTC)

OK - scratch that - this site has natural 1 carat diamonds in the classic 58 facet 'brilliant round' cut for about $3,000 - but this site has 1 carat synthetic diamond (chemically identical to the real thing remember) in that exact same 58 facet cut for just $100. So I guess we already passed the point where natural diamonds make any kind of sense at all. SteveBaker (talk) 05:47, 7 December 2008 (UTC)

Yes, I seem to recall a New Scientist article where a team in South Africa (not sure if they were De Beers or not) were given a diamond that was believed to be a synthetic diamond but whoever it was wanted proof. In the end, the only reason they decided it was synthetic was because it was too perfect. This is the same for many other precious stones I believe. For example, I seem to recall watching a show many years back where someone was making synthetic rubies which were (nearly?) indisguistable from the real thing (they used to have to need some sort of starter/core but this team devised a way to make it without that I believe). The biggest/only? difference was that they added a UV dye so it was possible to distinguish them. It seems that the too perfect thing is rather common now [12] and indeed it's something that was recognised a long time ago [13]. I guess from that POV we haven't yet devised a way to make a diamond that is indistinguisable from most natural diamonds (this [14] suggests we are close and notes that there isn't really such a thing as a flawless diamond of any sort) although obviously it's theoretically possible for a natural diamond to be flawless as well. The diamond article also discusses this a bit. Nil Einne (talk) 09:31, 7 December 2008 (UTC)

I've been reading around the subject some - and it appears that the synthetic diamond people can now control the insertion of flaws and they routinely dope the diamonds with various trace elements to make subtle colour shifts and such. So the "too good" problem seems to have been addressed also. However, the manufacturers go to some lengths to point out that they are not in the business of making 'fake' natural diamonds - they just make diamonds that are as good or better than the natural ones. SteveBaker (talk) 03:12, 8 December 2008 (UTC)

Can they make (good quality) synthetic coloured diamonds? From what I can tell, that seems to be where the real money is. --Tango (talk) 14:47, 7 December 2008 (UTC)

Yes - definitely. There are several sites out there selling synthetic yellow diamonds (which are apparently quite rare in nature). It's just a matter of 'doping' the carbon with various other elements before they apply the heat and pressure. SteveBaker (talk) 03:12, 8 December 2008 (UTC)

To SteveBaker ... pardon the stupid question ... what exactly is the difference between a natural diamond and a synthetic diamond? One comes from nature and one is man-made. That is the only difference? Other than that, they are 100% the same exact identical thing? Is that what you are saying? Thanks. (Joseph A. Spadaro (talk) 16:40, 7 December 2008 (UTC))

I'd hate to answer for him, but yes. They are exactly identical. Unlike some other gemstones, diamond is chemically VERY simple. Its a network solid composed soley of tetahedrally bonded carbons (i.e. sp3 hybridization), and that's about it. Its essentially pure elemental carbon, and quite simple to produce synthetically. They are also relatively common naturally as well; the reason the price is so high is that DeBeers buys up all the raw diamonds in the world to keep the price artificially high. BTW, this is incorrectly identified as a monopoly; DeBeers is more correctly described as a Monopsony or a Syndicate. They aren't the primary retailer of diamonds; they are however the primary buyer of diamonds, and carefully control how many diamonds they release onto the market. --Jayron32.talk.contribs 19:01, 7 December 2008 (UTC)

OK, makes sense so far. But, if they are indeed exactly the same ... why wouldn't everyone just forego the "real thing" costing thousands of dollars and purchase the exact same (synthetic) thing for only a fraction of the cost? Thanks. (Joseph A. Spadaro (talk) 02:18, 8 December 2008 (UTC))

Well - that's the REAL question. Quite simply, the "natural" diamond people advertise to gullible buyers that "natural is better" in some nebulous and ill-defined manner. If you are in the jewellery store with the woman of your dreams - and the salesman brings out the $100 one carat ring and the $3500 one carat ring - and you make the HORRIBLE mistake of asking why - he's going to say "Well sir, the one on the left is SYNTHETIC (he shudders theatrically at this point)"...now, can you tell the oh-so-sexxy long-legged green-eyed redhead that you're going to buy her the SYNTHETIC diamond when there is a NATURAL one right there in front of you? Good luck with that one! The problem is that buying diamonds for jewelery isn't a matter of providing a lump of rock with an appropriate chemical formula and sufficient mass - it's more a matter of conveying the message: "Look how I'm a better potential mate than that bastard Brian you've been flirting with because I clearly have so much more disposable income than him that I can buy this sparkly thing with no particular 'inherent' value and give it to you."...and if your potential mate ever found out that you were a cheapskate and went with synthetic rather than natural - well, Brian might be back in with a chance! Why do male peacocks have such ridiculous tails? Welcome to human mating rituals! But this is not a new matter. Natural versus cultivated versus synthetic pearls has undergone a similar debate over the years....and it's just as ridiculous. SteveBaker (talk) 03:12, 8 December 2008 (UTC)

Taking the woman with you when you buy her a ring is a serious mistake. So, buy her a 2 carat synthetic ring, when she isn't present. If she asks if it's real, you can answer honestly that it is. As for her finding out, that's the whole point, it is a real diamond, so there's no way to tell if it was dug up or not. I bet that cheap synthetic diamonds will damage sales of zircons and all other imitation diamonds. StuRat (talk) 15:19, 8 December 2008 (UTC)

It's easy to tell the difference between a Zircon and a diamond because zircon has a lower refractive index and to make it sparkle like a diamond you have to cut the stone at different angles - so a halfway decent jeweller can spot one just by looking at how it's cut. Cubic zirconium (which is NOT the same thing a zircon) has a very similar refractive index to diamond and is harder to tell apart without destroying it. Cubic zirconium crushes fairly easily and I believe you can shatter it by whacking it with a hammer...which wouldn't work with a diamond that's a flawless as a cubic zirconium appears to be. But certainly, it's essentially impossible to test a diamond and know conclusively whether it's synthetic or not...but just be sure she doesn't see any credit card receipts! SteveBaker (talk) 16:53, 8 December 2008 (UTC)

Apparently some synthetic diamond manufacturers do (or are planning to, at least) engrave tiny serial numbers on their diamonds so people can tell they are "fake". I guess the "real" diamond merchants wouldn't let retailers sell them otherwise (of course, a retailer could switch to entirely "fake" diamonds but the diamond merchants would tell the press and the retailer would go out of business, even though no-one could actually tell the difference). --Tango (talk) 14:04, 9 December 2008 (UTC)

My Lord ... how eye-opening this discussion has become ... particularly given the original question that I had posed ... Thanks! (Joseph A. Spadaro (talk) 04:48, 8 December 2008 (UTC))

Irradiated currency

I was wondering if some law enforcement agencies use irradiated currency, as shown in the film Dark Knight? I've tried web search to see if any of them does but the results weren't terribly enlightening. --BorgQueen (talk) 19:43, 6 December 2008 (UTC)

Lots of agencies have used "spy dust" to track all sorts of things since the 1950s at least, currency included. Some of these are purely chemical, some are radiological. I know the Stasi in particular used radiological sources to tag all sorts of things to see where it went and who came in contact with it. (Note that there is a distinct opportunity there for someone to write an article on the subject!) --98.217.8.46 (talk) 21:35, 6 December 2008 (UTC)

They use things called 'Taggants' to track all sorts of things. These are microscopic particles that they make by taking several different colored sheets of very thin plastic - fusing them together and rolling them out to make a very thin 'sandwich' of different colored layers - then shredding the resulting material into dust-like particles. Viewing that 'dust' under the microscope lets you see the order of the colors. So, imagine you have red, green and blue plastic, you could make layers RGBGBGR (say) and impregnate anything from bullets to explosives, money - almost anything with tiny shreds. By keeping careful track of which color sequences are used in what products, at any time in the future, if taggants with that color combination show up at a crime scene or whatever - they can look up that RGBGBGR color sequence and know precisely when and where the substance was manufactured. That's how crime scene analysis can discover precisely when and where explosives were manufactured. Check out the MicroTraceSolutions web site for a photo of some taggants. The taggants are vastly too small to allow anyone to remove them - and there are huge numbers of them in any specific piece of explosive or whatever. It would certainly be possible to covertly dust someone's clothes with taggants and use them to discover whether they had been in some specific place. SteveBaker (talk) 02:39, 7 December 2008 (UTC)

I know of a case in Romania, when some lumber thiefs were caught using some kind of fluorescent paint. Wood at sawmills was painted with some invisible paint, and the night after some more lumber had disappeared, police patrols were just driving through neighboring villages with UV lights. The vehicles and clothes of those responsible suddenly begun to shine brightly. :) Not exactly currency and radioactivity, but the same principle. --131.188.3.20 (talk) 12:12, 8 December 2008 (UTC)

Bush vs. Obama

Who would win a fight between Bush and Obama? This is not a joke question. Really I am asking the question of what scientific process you would follow to try to predict the outcome of a fight between two people, I have just picked Bush and Obama as a test case because they are both very well known "average" guys, so people have a good idea of their physiques and other characteristics, but neither are known as "athletes" or "fighters". 212.159.3.234 (talk) 19:58, 6 December 2008 (UTC)

The closest one gets to a really scientific process would come only if one had statistical information on their past fights. That's how bookies do it, anyway, and even they are wrong enough to make betting worthwhile. Other than that it is no more scientific than Pirates vs. Ninjas. Once someone has decided that one side would win for some reason, they can find a thousand reasons why and a thousand counter arguments, because they are not in any way constrained by the facts of the matter. --98.217.8.46 (talk) 20:15, 6 December 2008 (UTC)

There are some reasonable objective facts you can use - height, weight, age, any martial art or self-defense training, etc. In the case of the example used: They both appear to be broadly similar in size (Obama's about an inch taller and ten pounds lighter), but Obama's fifteen years younger than 62-year-old Bush. I'm not personally aware of any particular training either may have that would swing it, so if I had to bet it would probably be on Barack. But yeah, beyond these limited items it's down to personal opinion about how a given fight would happen. ~ mazca ^t|c 21:01, 6 December 2008 (UTC)

Obama may have a better sense of balance then Bush. At least he doesn't regularly fall of a bike that I'm aware of (of course he may never ride one). Whether that will help in a fight, I don't know. On the other hand, the OP didn't mention unarmed combat or rules for this fight and Bush is more likely to have a gun then Obama Nil Einne (talk) 09:06, 7 December 2008 (UTC)

Diffusive Systems

I am studying off of this math modeling book in which they model all kinds of physical (chemical) and biological systems. There is a section on the diffusion equation. The book derives the equation, and then solves it. I already have the answer but I was trying to graph the solution just to get a feel of what really is happening in the system but the problem (and the solution) has 6 parameters. My question is, can someone please give me an idea of what the value of these parameters can be? How large or small are they? What is their order of magnitude in real life so that I can plug them and obtain a graph modeling a real life system? The parameters are D which is the diffusivity constant, v which is the drift velocity of the particles, mu which is the decay (death) rate of the particles, L is just the length of the system (one dimension equation), j which is a fixed flux on one of the boundaries (let's say x=0), and w which is the intrinsic speed. Any real system will be okay as long as I can get some values for it. It can be diffusion of oxygen in air at room temperature or larvae hatching from eggs, spreading out and then being eaten or something. If it will help, I can post the equation (and the solution).-Looking for Wisdom and Insight! (talk) 02:05, 7 December 2008 (UTC)

Radioactive Decay

On a different note, when we are talking about radioactive decay, the number of particles that decay is proportional to the number of particles present and the constant of proportionality is the probability of a single particle decaying. Using this, we get a very simply (and well known even to the algebra students) ordinary differential equation which gives us an exponential decay solution. My question is that mathematically, we are assuming continuous number of particles but in real life, the number is not only finite but also discrete. It is not possible to have 4.567 particles at any time. So, what really happens in a physical system with radioactive decay? If I have a few drops of Barium 137 (which has a half-life of around 2.5 minutes), in the beginning there are a large number of particles, but what starts happening when the number of particles become small, less than a hundred let us say? The math says that there always be "something" but in real life, after long enough, I will have only a single atom left and if it decays, there is nothing left. And if it never decays, there is always one left. The number is not decreasing. Looking for some wisdom and knowledge. Thanks!----A Real Kaiser...NOT! (talk) 23:15, 6 December 2008 (UTC)

You're absolutely right, the exponential decay is an approximation of the real thing. For a large number of atoms (which is usually what you have - atoms are pretty small!) it's a very good approximation. Once you get down to very few atoms it's not a valid approximation at all and the number of atoms left needs to be considered as a random variable. --Tango (talk) 23:44, 6 December 2008 (UTC)

Exponential solution gives an expected value of the number of particles left. Simply speaking, expectation is how many particles you expect, on average, to remain after time T. Imagine you have many identical systems (many identical drops of Ba 137). After a given time T (say, a week exactly) you will have 10% of drops with 0 atoms of Ba 137 left, 20% of drops with 1 atom left, 15% of drops with 2 atoms left, etc... Average number of atoms left is an expected value. Even if the number of atoms is always integer, expected value formally need not be integer. If you have 2.4 children per family, no single family will actually have 0.4 of a child ;) . It just means that 2 or 3 is a better guess than 9999. --Dr Dima (talk) 00:02, 7 December 2008 (UTC)

Yep - it's purely a statistical relationship. It's theoretically possible for your Barium 137 to just sit there doing nothing for a thousand years then to have all of it decay in a microsecond. The only thing that prevents that from happening in common practice is that there is such an ungodly number of atoms in "a few drops" that the probability of that kind of decay pattern is very, very tiny indeed - unlikely to happen ever during the entire life of the universe...but the probability isn't zero - so it might happen. Think of this like having a bucket of pennies - you dump the bucket out onto the floor once a day and take out all of the pennies that come up 'heads' and put all of the 'tails' back into the bucket ready for the next day. The 'half-life' of your bucket of pennies is 1 day because there is a 50/50 chance of each penny being removed on each day - so the number of pennies drops by a factor of two each day. If there are 1024 pennies in the bucket on day 1, then the theoretical statistical time for them all to decay is about 11 to 12 days because the expected number of pennies in the bucket each day is: 1024...512...256...128...64...32...16...8...4...2...1...1...0. But you and I know that if you flip 4 coins, you won't always get two heads...so in the last few days of the experiment, all four coins could easily come up heads on day 9 of the experiment - or it might take many days of flipping that last coin and getting tails before the last coin 'decays' and ends the experiment. But the first few days of the experiment will follow theory pretty accurately - but not exactly. SteveBaker (talk) 02:25, 7 December 2008 (UTC)

December 7

Electric Tooth Brush

I have a couple of questions regarding these tooth brushes: does their effectiveness correlate with their frequency?

• would it make sense to design a tooth brush that made the teeth resonate, or would it damage the teeth? Soap (talk) 00:13, 7 December 2008 (UTC)

I don't know about effectiveness - but you couldn't design something like that. No two teeth are the same size or shape - so the resonant frequency of each tooth would be different. SteveBaker (talk) 02:11, 7 December 2008 (UTC)

Some frequency searching feedback could fix that - talk about having a tune on your mind! -hydnjo talk 03:06, 7 December 2008 (UTC)

Probably a small hammer that would hit the tooth and measure the resonating frequency would do that right? Assuming it is practical, would it make sense to design it?77.243.73.133 (talk) 11:30, 7 December 2008 (UTC)

Putting aside the fact that hitting your teeth with a small automated hammer may not be all that healthy, I don't think there's any particular benefits to a resonating toothbrush. Their purpose is to remove unwanted substances from the surface of the tooth, so causing the tooth itself to vibrate doesn't sound very necessary. There will definitely be a correlation between frequency and effectiveness, but it's more to do with finding a balance between swiftly removing plaque in the limited period the user is touching a particular tooth, but not having the toothbrush blasting away so fast it wears down the teeth or damages the gums. ~ mazca ^t|c 12:33, 7 December 2008 (UTC)

Rare meat

Why does rare meat taste so much better than well-done? Or rather, as de gustibus non est disputandem, what chemical changes account for the difference in taste between rare and well done meat? DuncanHill (talk) 00:18, 7 December 2008 (UTC)

Blood. You are experiencing a pleasure in the taste of fresh blood. I do not know if this is any good an answer for you but certainly you will find more blood in your raw flesh than in your burnt one. ~ R.T.G 01:24, 7 December 2008 (UTC)

I like cooked blood too. DuncanHill (talk) 01:25, 7 December 2008 (UTC)

My understanding is that the red stuff that comes out of a rare steak is not actually blood (the animal is bled before butchering), but a thin fluid of proteins leaching from the muscle tissue. I don't have a specific cite handy, but I heard it on Good Eats, which is unusually fact-based for a food show. Matt Deres (talk) 02:13, 7 December 2008 (UTC)

The red stuff is Myoglobin, here's a book source about the flavor part. -hydnjo talk 02:36, 7 December 2008 (UTC)

Yeah, the red stuff is definately not blood. Blood isn't found spread evenly among all of your tissues; its pretty well confined to things called veins and arteries. There is no blood inside of your muscle tissues. Blood is also pretty terrible for the flavor of meat; if it is not quickly drained, and it does enter the meat, it pretty much ruins it. The red stuff is just the stuff that makes muscles red in general; as noted above, its myoglobin. --Jayron32.talk.contribs 03:14, 7 December 2008 (UTC)

The red color of meat is certainly caused by the myoglobin (and that also explains why chicken isn't bright red) - but "There is no blood inside your muscle tissues"??? Er...are you sure about that? Our article on muscle says that they are "densely" suffused with capillaries - and the article on capillaries says that they carry blood. So there ought to be a fair bit of blood in muscle - and hence in meat from an un-bled animal...but I'm no biologist - I could be wrong. SteveBaker (talk) 05:34, 7 December 2008 (UTC)

Capillaries will have blood in them. Whether you consider them part of the muscle tissue or seperate may vary Nil Einne (talk) 09:02, 7 December 2008 (UTC)

OK, nice semantics - but they are definitely a part of the steak - some of them are so fine that red blood cells have to fold up to get through them...there is absolutely no way you could dissect them out during butchering! I doubt very much that 'bleeding' the animal after slaughter would drain those teeny tiny tubes - so we may safely deduce that there IS blood in steak. SteveBaker (talk) 02:49, 8 December 2008 (UTC)

Would that work with meat that is frozen almost as soon as it's killed or eaten fresh without being drained? We never drain anything and it never tastes odd. CambridgeBayWeather Have a gorilla 04:57, 7 December 2008 (UTC)

You hunt meat, kill it, and then don't drain the blood? Really? --Jayron32.talk.contribs 05:31, 7 December 2008 (UTC)

While today you might be able to get back to town and find a heated area to drain it before the meat freezes, in older times that would not have been possible, it's unlikely that you would get back quick enough. CambridgeBayWeather Have a gorilla 06:59, 7 December 2008 (UTC)

Why do you need to find a heated area? You can drain blood rather fast if you adopt the Muslim/halal method of killing an animal. (If you kill the animal while hunting that won't be possible but I'm pretty sure traditionally people would have been far more likely to wound rather then immedietly kill an animal. Arrows, spears and the like aren't going to guarantee and immediate kill.) Unless you are living in liquid nitrogen, the animal is not going to die that fast Nil Einne (talk) 08:56, 7 December 2008 (UTC)

Did you mean dhabihah rather than halal? To do that would you not need to be able to catch the animal first? It would seem to me that wrestling with a wounded muskox or even a caribo and trying to cut it's throat is going to be a problem. Still the animals were never (and still aren't) drained prior to eating. CambridgeBayWeather Have a gorilla 12:13, 7 December 2008 (UTC)

No I did mean halal. Dhabiha methos of slaughter is generally compulsory for halal meat for many Muslims. Anyway ignoring the semantics for now, I disagree it's going to be a big problem. Ultimately you have to kill the animal. Whether you slit it's throat (note it could be a spear or whatver, it doesn't have to be a knife) or try to stab its heart, both obviously require some skill but aren't not going to be that hard if you're used to that sort of thing. Otherwise humans would never have succeeded at hunting Nil Einne (talk) 15:54, 14 December 2008 (UTC)

I should note that not everyone prefers rare meat Nil Einne (talk) 08:57, 7 December 2008 (UTC)

A few notes from a cooking point of view. Many people like a rare steak. In this case the outside of the meat is cooked very quickly and the sugars undergo caramelisation. The taste mixes salt and sweet, which is generally pleasant. I expect there is umami involved as well. There is also an agreeable contrast between the crispy outside and soft middle of the steak. Let's also consider the counterfactual: long-cooked meat. If you cook a steak for a long time it may become tough and rubbery. However, some cuts of meat respond very well to slow cooking. Often we sear the meat first, to achieve the caramelisation, then add liquid (water, stock, wine, beer etc.) and cook slowly for hours. The meat becomes fibrous but not dry. The taste of the meat is transferred to the liquid and any vegetables that are included. Itsmejudith (talk) 12:55, 7 December 2008 (UTC)

Many thanks to you all - some fascinating stuff. DuncanHill (talk) 12:59, 7 December 2008 (UTC)

And given CambridgeBayWeather's very high latitude, where the average low is below -10ºC all year long, I'd guess that the meat and its blood would freeze rather rapidly if you didn't find a heated area. Nyttend (talk) 14:49, 7 December 2008 (UTC)

Whoops, I probably should have indicated that I live in Cambridge Bay, Nunavut and the mean daily average is −14 °C (7 °F). Sorry for any confusion. CambridgeBayWeather Have a gorilla 22:50, 7 December 2008 (UTC)

In the old days of farming, a farmer would kill hogs when the temperature dropped cold enough to preserve the meat but perhaps not way below freezing [15]. The animals throat would be cut and he would be hoisted by his hind feet to drain the blood within a couple of minutes. I don't see why that wouldn't be desirable for a deer as well. Field dressing [16] should get rid of the blood as well as speeding the cooling of the meat. Edison (talk) 03:51, 8 December 2008 (UTC)

All of that seems to involve the hanging of the animal but without trees that's not practical. Anyway, the thing is that we don't drain the blood and the animals taste fine, which seems to contradict with the earlier comment. CambridgeBayWeather Have a gorilla 06:44, 8 December 2008 (UTC)

"Globin" such as "myoglobin" and "haemoglobin", is a word used to describe blood cells, one is red, one is white. They contain stuff like salt, sugar, iron, etc. The red colour is partly caused by the iron, which in its natural form is pure rust or red rock, is the building block (a magnet) upon which oxygen is carried throughout the body therefore being well spread in a length of veins long enough to reach around the planet several times (that much veins must go into muscles or something) and being several six inch nails worth in a human body and as may be known has a strong taste. Salt, its very important, you are stuffed with it, what it does I do not recall, it has a strong taste. Sugar, again you are packed out with the stuff. It is the coal for you fire. It is the acid by which your blood and stomach burn. It burns the food and lets off the gas and steam and again it has a quite strong taste. Unfortunately what is sad but true after this point is that other stuff with a strong taste in its basic element sort of goes as far as calcium, clorophyll (or whatever gives that green taste), and narcotic tasting stuff like caffine and aspirin which tastes more alike the more pure it is. It's all sugar, salt and steel. Even natural flammable gas has no smell or taste. The smell is added so that if you are about to suffocate or set it on fire you have some sort of warning. Even when making soya milk it tastes pretty much like carboard unless they add calcium, salt and sugar (or apple juice which is common in the tastier stuff). Tastes pretty much like milk but is basically that same old stuff you are tasting. Ask any chef what is most important in a good meal... colour and presentation. What do they make fake meat out of? Corn. Can they make it taste like real flesh? Little fatty bits and all. Yik. ~ R.T.G 19:23, 8 December 2008 (UTC)

Um quite a bit of what you're saying is wrong. For example, I never, ever heard someone call Myoglobin a 'blood cell' in my 4 years at university doing biology which isn't surprising given that it isn't found in the blood. Nor have I ever heard some call myoglobin a white blood cell which isn't surprising since besides the aforementioned reason myoglobin when oxygenated is generally red (or brown) as with haemoglobin. BTW, the vast majority of Meat analogue is made with soyabean and sometimes a variety of legumes like chickpeas not corn. Nil Einne (talk) 16:01, 14 December 2008 (UTC)

Natural orbitational phenomenon

As in the orbitational phenomenon. What are the odds? Lets say you could remove the moon to outside the system and send it toward the Earth repeatedly on random courses until you got a stable orbit. What are the odds? Would the time scale of orbitational phenomenon occuring naturally fit in with the time scale of the orbital decay (or opposite) of the celestial bodies we have in the system now? i.e. the moon and other orbiting stuff will eventually crash or fly away... will this happen so slowly as new similar sized bodies will find such orbits before they do? Is there any known records of anything like a comet or a meteor that flew into a new orbit in our solar system? Any comets or meteors been recorded which are not beleived to have some sort of orbit in our system? ~ R.T.G 01:20, 7 December 2008 (UTC)

When looking for the likelihood that something the size of the moon would get "caught" in the orbit of earth you'd have to acknowledge that the moon didn't likely come towards the earth and then get caught in orbit (Giant impact hypothesis). Now if someone can try to do some math to give you a real answer, that'd be impressive. Chris M. (talk) 02:04, 7 December 2008 (UTC)

It's not a matter of statistics...it's not possible. SteveBaker (talk) 02:09, 7 December 2008 (UTC)

"orbitational" isn't a word. I guess you're asking how the earth could have 'captured' the moon? The answer is that it couldn't. There is no course that the moon could arrive along that wouldn't result in it shooting off back out into space - or crashing into the earth. But you should read our article on the Moon#Formation - it explains that the 'capture hypothesis' doesn't work. The generally accepted theory is that another planet collided with the earth and the moon was formed from material ejected from the collision. The moon's current orbit isn't 100% stable - it will gradually move further from the earth. This applies to other objects heading towards the earth - they'd have to find some means to lose exactly the right amount of energy as they arrived in order to make a stable orbit. Notice how our spacecraft heading into orbit around other planets have to use an 'orbital injection burn' of their engines - or use the drag of the atmosphere of the planet - to lose some energy and make a stable orbit. Meteors and comets don't have energy - so atmospheric drag is the only way to get into orbit...and an incoming moon would need to shed far too much energy for that to work. SteveBaker (talk) 02:09, 7 December 2008 (UTC)

But the need to slow down is because the spacecraft is going so fast. If an object approached the Earth at a lower speed, essentially tangent to the Earth's orbit about the Sun, it might be possible for it to fall into a stable orbit. Certainly not a likely scenario with an object the size of the Moon, but still possible, I suppose. StuRat (talk) 04:35, 7 December 2008 (UTC)

Nope - no matter how close to the correct orbital velocity you were going (Remember: velocity means speed and direction), you couldn't be at the exact correct velocity without already being in orbit. Hence you either have to gain or lose energy from somewhere...which means that you need either some engines, sufficient drag through the atmosphere or some third body to shed the excess energy into. SteveBaker (talk) 05:19, 7 December 2008 (UTC)

You talk as if there is only one possible orbit. Aren't there an infinite number of orbits at different distances (and subsequently speeds) from the Earth ? And, therefore, won't a body moving in a certain range of speeds naturally move into a stable orbit by either getting closer to, or farther from, the Earth ? StuRat (talk) 23:03, 7 December 2008 (UTC)

No. Conservation of energy means an object has the same amount of total energy (potential+kinetic) at all points in its orbit, either that is enough energy for it to escape or it isn't. You can't move from one type of orbit to another without a change in total energy. One way to look at it is to realise that the laws of gravity are completely time symmetric, so if it is possible to go from a hyperbolic orbit to an elliptical one, it is possible to do the reverse - that means you can break orbit without needing to fire your rockets, which is clearly not true. --Tango (talk) 23:29, 7 December 2008 (UTC)

Ah! Thanks Tango! That's an elegant way of saying what I was trying to get across. Time symmetry...yeah. SteveBaker (talk) 02:34, 8 December 2008 (UTC)

Ok, so let's say the Moon's orbital velocity (at one point in it's orbit) is now X. You're saying that, if the Earth didn't have a Moon, and an object identical to the Moon approached the Earth at tangent to the Moon's orbit, but at a velocity of 0.999999999999 X or 1.000000000001 X, that instead of settling into a slightly higher or lower orbit, the Moon would fly off into space or crash into the Earth ? I find that impossible to believe. Orbits aren't that unstable. If so, then when some ancient meteor hit the Moon and increased or decreased it's velocity that much, it would have been knocked out of orbit, too. StuRat (talk) 14:51, 8 December 2008 (UTC)

If an object were at that speed in that position then it would already be in orbit. You can't get from a long way from Earth to a lunar distance from Earth without the Earth's gravity accelerating you (we call moving towards a massive object due to gravity "falling") so you would be at a too great a speed to be captured. --Tango (talk) 15:19, 8 December 2008 (UTC)

Escape speed at a given distance is √2 times the speed of a circular orbit at that distance, by the way. (In a Newtonian universe; near a black hole that's likely off.) —Tamfang (talk) 08:44, 14 December 2008 (UTC)

Quibble: velocity means speed and direction, yes, but direction isn't important here: if the kinetic energy is less than (the absolute value of) the gravitational potential energy, the body is in orbit, no matter which way it's going. —Tamfang (talk) 08:44, 14 December 2008 (UTC)

To expand a little of SteveBaker's excellent answer; orbital capture COULD theoretically work for a small chunk of rock that happened to hit the atmosphere at just the right angle and slowed down to exactly the right speed. The main problem with the moon is that its, and this is a scientific term, pretty friggin huge. With the exception of the now-demoted "Pluto" system, the Earth-Moon system represents the closest in size between a satelite and a planet in the solar system, by far. The moon is about 2% the size of earth; no other satelite is even CLOSE to being that large relative to its planet. Orbital capture works; but not for something that size... --Jayron32.talk.contribs 02:50, 7 December 2008 (UTC)

Actually, it might be possible to capture a moon-sized object by gravitationally scattering it off of our existing moon-sized object. An incoming planetoid with just a little more energy than escape velocity might be captured if it transfered enough energy to our existing moon. Of course, that would leave both objects in eccentric and probably unstable orbits, but why be picky. Dragons flight (talk) 03:32, 7 December 2008 (UTC)

Yep - but the idea that our moon could simply be free-falling through space, pass close to the earth and be "captured" is a mathematical impossibility. That's why this theory for the formation of the moon has been dismissed these days. SteveBaker (talk) 05:19, 7 December 2008 (UTC)

So how do the theories that certain moons of other planets were captured work? Do they rely on the other moons or nearby planets? I can see why in the 2-body problem you can't go from an escape orbit to a periodic one without a change in energy, but it must happen somehow. --Tango (talk) 13:55, 7 December 2008 (UTC)

It's only a mathematical impossibility in the 2-body point mass (or rigid ball) model. While it's unlikely, the gravitational influence of the Sun could change the velocities by the right amount, see Interplanetary Transport Network. I think at least theoretically there could be a situation where tidal forces slow down a moon while it is passing close to the planet and make the orbit more stable (but the evolution of such a orbit wouldn't fit to the current orbit of Earth's Moon). Icek (talk) 15:00, 7 December 2008 (UTC)

Great answers! The collision idea is easier to visualise. It also gave me an idea to support it I think... all of the Suns orbiting bodies are more or less in a disc formation. Perhaps this is the angle at which large stuff is more likely to bounce off and find an orbit. I must agree that thinking about how an object would hit an atmosphere sounds more likely to make it curve. Also given the fact about the moons size and its relationship to life here (it provides the tide and hence the beat) its a pity we can't compare similar systems. I have seen a few pics on TV of a comet which hit Jupiter or Saturn but that is the only mention of something large hitting the gravity of a planet I can recall and funny enough as it left a large mark (i cant rememer which planet but it was a gas giant, Jupiter I would beleive) the comet bounced like a skimming stone not just leaving one mark but a row of marks where it bounced, another collision supporting evidence too. ~ R.T.G 01:58, 8 December 2008 (UTC)

BUT... if the Moon hit the Earth causing the orbit... isnt the Earth on a stable orbit? Wouldn't the collision of the Moon cause the two bodies to orbit each other rather than one orbiting the other? I guess the Earth could have been stabilised by the Moon colliding but is that any more likely than them just happening on their orbits without colliding? ~ R.T.G 02:04, 8 December 2008 (UTC)

The earth and moon DO orbit each other. The point about which they both rotate is somewhere beneath the surface of the earth - about a third of the way down to the center. Technically - the moon didn't hit the earth. Some other small planet (called 'Theia - perhaps the size of Mars) hit the earth - the resulting energy would have forced a blob of molten matter to spirt out of the opposite side - and billions of tons of debris to be shot into orbit - rapidly forming a disk (like the rings of Saturn). Gradually, the material in the rings would clump together making a larger and larger body - which eventually consumed all of the ring material. THAT is the moon. Our article Giant impact hypothesis explains the currently prevailing theory. SteveBaker (talk) 02:34, 8 December 2008 (UTC)

The Comet that hit Jupiter was Shoemaker-Levy. It didn't bounce. The reason we saw a series of collision points was that the comet broke up (prior to collision), due to tidal forces.Bunthorne (talk) 07:49, 8 December 2008 (UTC)

That theory of Giant impact hypothesis sounds good for most part but I don't understand the pictures where the theia object moves backwards and forwards or in a sort of a squiggle shape...? Don't cellestial bodies travel in straight lines or perfect curves? And, if the moon was definitely a ring but definitely only for a hundred years... what is going on with Saturns rings? ~ R.T.G 18:45, 8 December 2008 (UTC)

The picture was probably centred on Earth rather than the Sun, so the weird path is combination of the (roughly) perfect curves of the Earth and Theia. As for Saturn's rings, nobody is entirely sure, but it may be to do with its moons preventing coalescence. --Tango (talk) 01:00, 9 December 2008 (UTC)

No, they are all pictures of the Earths orbit around the Sun and at least 3 of them show Theia moving on a random path, including making about ten percent orbit on Earths orbital line then doubling back and repeating that a few times before smashing in to the Earth instead. Maybe its just some vandalism for a laugh but some effort has been made. ~ R.T.G 02:30, 9 December 2008 (UTC)

Actually, I think the theory of how Saturns rings stay put is becoming pretty well developed - there are multiple causes of their stability - and it seems they all conspire to create the unusual density, structure and longevity of Saturns' ring system. The moons that stop the rings from coalescing - yet give them such defined structure are called 'Shepherd moons'. There has even been a recent discovery of rings around one of Saturn's moons (See: Rings of Rhea)...this is amazingly cool! SteveBaker (talk) 02:40, 9 December 2008 (UTC)

I seem to remember reading something not too long ago about an attempt to model Saturn's rings and it didn't work, they couldn't get them stable over long periods (it's possible they simply aren't stable over long periods and we're just lucky to be born at a time when they are there). --Tango (talk) 13:40, 9 December 2008 (UTC)

If you look at the animated image you'll see the Earth is staying still, whereas we know it's actually orbiting the sun, the the image is being rotated as you watch it to compensate for the Earth's movement. The movement of Theia combined with that rotation of the image is what gives the weird shape. --Tango (talk) 13:40, 9 December 2008 (UTC)

Tango, if you can't see something unusual about the Theia trajectory... also regarding the lucky timing of the rings, Jupiter, Saturn, Neptune and one of Saturns moons all have rings although only Neptune and Saturns are easy to see. Planetary rings ~ R.T.G 00:17, 10 December 2008 (UTC)

Well, its trajectory isn't a standard elliptical orbit because of the influence of Earth's gravity, but it's not far off. It just goes a little faster or slower than you would otherwise expect at certain points, which causes it to either catch up with the Earth or fall behind it. --Tango (talk) 00:38, 10 December 2008 (UTC)

Comet Shoemaker-Levy 9 illustrates something said earlier, that tidal forces may cause capture. During the two years before impact, the comet fragments orbited Jupiter (in a very eccentric ellipse). I'd guess that some other fragments escaped. —Tamfang (talk) 08:44, 14 December 2008 (UTC)

nepeta

Catmint and catnip seem to be used interchangably. Catmint is 'nepeta mussinii' and catnipt is 'nepeta cataria'. Cat have quite different reactions to each. Can that entry be refined?

Goetzds (talk) 01:28, 7 December 2008 (UTC)

Wikipedia: The encyclopedia you can edit! SteveBaker (talk) 01:54, 7 December 2008 (UTC)

Ouch! hydnjo talk 02:26, 7 December 2008 (UTC)

WP:SOFIXIT is the link you were looking for... --Jayron32.talk.contribs 02:44, 7 December 2008 (UTC)

Why do CFL bulbs take a while to reach full brightness?

Why do Compact Fluorescent Lights take a few minutes to "warm up" to full brightness? Incandescent bulbs seems to reach full intensity instantly. --69.149.213.144 (talk) 03:34, 7 December 2008 (UTC)

I think it is literally because they need to warm up. That is, they work better once they reach optimal temperature, much like a car. Not all compact fluorescent lights have this deficiency, however, or at least not to the same extent. Regular incandescent bulbs need to warm up, too. The difference is that they warm up in a fraction of a second, because they are so much less efficient, and that wasted energy all produces heat. StuRat (talk) 04:25, 7 December 2008 (UTC)

Fluorescent lamp is a bit technical, but has more details. 76.97.245.5 (talk) 05:05, 7 December 2008 (UTC)

In that article, it isn't really so clear that there is a difference between the types of ballast. I guess that your CFLs just happen to be older and still have magnetic ballasts (a.k.a. "reactive ballasts"). (Thanks for being an early adopter!) New CFLs should have electronic ballasts and start up just as fast. This is a little bit better described at Electrical ballast — Sebastian 09:17, 7 December 2008 (UTC)

I don't think the OP is talking about start up time but warm up time. As in the CFL has started but is not that bright Nil Einne (talk) 11:29, 7 December 2008 (UTC)

That's correct. They all turn on instantly (no flickering or delay), but are rather dim for the first few minutes. (I think CFLs are too small for magnetic ballasts anyway, no?) --69.149.213.144 (talk) 13:47, 7 December 2008 (UTC)

My suggestion, give those old CFLs to a heavy drinker, as a light that starts out dim will be less shocking to them during hangovers. StuRat (talk) 22:40, 7 December 2008 (UTC)

Light bulbs work by making something white hot. In your older light bulbs this is a hair thickness piece of metal which even the flame of a match would burn through. It is specially sealed so that it doesnt burn itself out. In a flourescent bulb is a gas which doesnt need to be so hot to reach white hot intensity. Compare it to the movie special effects trick for making a person appear to be on fire. The stuff used doesnt burn at such a high temperature as most fire but does burn hot. So, your flourescent bulb heats up a gas and even though it requires less heat, it still is hot and to heat the whole chunk of gas to white hot in one instant would probably give you an explosion. The electricity only provides heat and the whole inside of the CFL bulb lights up not just a little strand of metal. ~ R.T.G 23:14, 8 December 2008 (UTC)

According to Wikipedia there is such a thing as flourescent lighting that starts instantly ~ R.T.G 02:58, 9 December 2008 (UTC)

What puts the fluorescence in fluorescent lights?

What are the most common phosphors in commonly available fluorescent lights? Dragons flight (talk) 04:42, 7 December 2008 (UTC)

Have you actually read the fluorescent light article you linked to? There is copious information about the phosphors there. SteveBaker (talk) 05:08, 7 December 2008 (UTC)

There is some information, but most of it is not very specific (e.g. which Eu and Tb compounds?) and does a poor job of distinguishing what are the most common (as opposed to listing what is merely possible). I'd like to know which specific compounds are the most significant on the market today. Dragons flight (talk) 05:35, 7 December 2008 (UTC)

The article seemed pretty darned specific to me...the section Flourescent_light#Phosphor_composition says that the most common lamps use rare-earth doped phosphors - and provides a labelled spectrum of the light (Image:Fluorescent_lighting_spectrum_peaks_labelled.gif) - which (if you scroll down a bit from the image) lists the chemical composition of the phosphor corresponding to each peak. You won't do better than that because (as the article explains at some length) each tube manufacturer will tweak the mix of phosphors to get the exact most pleasing/natural color they feel is right. SteveBaker (talk) 06:04, 7 December 2008 (UTC)

Steve, I'm not sure if you intended to link to the spectrum image or not but incase you're not ware, if you want to link to an image without it appearing in the page you can use [[:Image:Cat.jpg]] Image:Cat.jpg (wow that actually exists) Nil Einne (talk) 08:51, 7 December 2008 (UTC)

(fixed!) Ooops! Yes, I knew - I was just being yelled at to "get away from that damned computer and do {somethingorother}" which broke my concentration. Sorry! SteveBaker (talk) 02:16, 8 December 2008 (UTC)

making Part II

Thank you for the information. However, some of it was a little too complicated for me. Let me ask another question.

Let's say I want to make Zestril (Lisinopril), a high blood pplyssure medication. Would I start with, say a plant (or some other natural being), then alter the chemical make up to create a substance. Then add several other products, chemicals, heat, transfer of the product to make a drip, then alter the drip to make another product, etc....In the end I would have Zestril.

What I want to know is what kind of initial product or plant would you start with? I'm talking all drugs, I just used Zestril as an example. I hope the question makes sense. —Preceding unsigned comment added by JelloTube (talk • contribs) 10:22, 7 December 2008 (UTC)

We don't know how to quickly select the initial product/plant to start with in drug discovery and only find out the right one via clinical tests. To compensate with the lack of data we try to obtain as much samples as possible of anything which have promising effects (for example a plant was used by native inhabitants to alleviate muscle pain while another mushroom is rumoured to have the same effect). The selection process are usually done through in toxicity and dosage tests in cell tissue, Animal testing and finally Clinical trials. Anything with adverse reactions or have nasty side effects will be removed. If we're lucky, probably out of 10,000 initial samples will yield one or two viable substances for drug use (and we have to monitor the long-term effect of that drug). This process is extremely long and expensive costing millions of dollars and years.--Lenticel ^(talk) 12:40, 7 December 2008 (UTC)

Lenticel is referring to the selection/discovery of the drug, but if you already know the chemical and just want to synthesize it then it would be a good idea to read the patent! Drugs are usually protected by patents, and in order to get patent protection you have to publish details of the chemical process. E. g. go to http://www.google.com/patents/ and enter "lisinopril", and one of the results is Process for the preparation of 1-(N 2-(S)-ethoxycarbonyl)--3 phenylpropyl-N6-trifluoroacetyl.... - just click on "Read this patent" and there it is. You'll probably have to do further research on cited prior art in order to find out how to make the direct precursors.

By the way, Zestril is not the same as lisinopril; the latter is one chemical, the former is a whole medical preparation containing the chemical. Icek (talk) 13:37, 7 December 2008 (UTC)

OK, a simple answer: You can buy chemicals at all levels of complexity, check Sigma Aldrich, a company that sells literally millions of different chemicals. Some are isolated from plants or other living sources, some are derived from petrol, but most are have been synthesized from these by chemical synthesis. It works like a construction kit - you assemble assemble building blocks and add molecular features. Chemist learn the rules for this game and if a chemical synthesis has been published then you can repeat the sequence. Cacycle (talk) 03:26, 8 December 2008 (UTC)

Thank you. All these were helpful. I've just always wondered how the complicated world of medications began. —Preceding unsigned comment added by JelloTube (talk • contribs) 08:44, 8 December 2008 (UTC)

Asking the gods of science for some help.

A member of my family is going to attent a game show of this format http://en.wikipedia.org/wiki/Deal_or_No_Deal

There are 22 boxes with progressively larger ammonts of cash in each box. I would like to ask if there are any factors which can give an advantage (something similar to monthy hall problem), something to increase the probability of winning?. —Preceding unsigned comment added by 77.243.73.133 (talk) 14:13, 7 December 2008 (UTC)

How much will I get if I tell you? Icek (talk) 14:31, 7 December 2008 (UTC)

The strategy is relatively simple: Keep track of which amounts are removed. When asked whether you quit, compute the average of the remaining amounts - that's the expectancy of what is in your box. If the amount you are offered is greater than or equal to the average, then quit, else continue. Icek (talk) 14:36, 7 December 2008 (UTC)

I think the traditional and most effective method is to sleep with the producer - but there may be ethical, moral, and sexual compatibility problems with this approach. DuncanHill (talk) 14:38, 7 December 2008 (UTC)

This has been asked on both the maths ref desk and here... interestingly the maths ref desk has produced far more constructive answers - take from that what you will! (Oh, and to the asker - please don't cross-post in future, it just ends up with effort being split.) --Tango (talk) 14:42, 7 December 2008 (UTC)

But, being on the Science Ref Desk, perhaps we should go beyond the simple mathematics of probability. For example, if offered either 100 million dollars or a 1 in 2 chance at 1 billion, just about everyone would take the sure thing, even though, on average, the gamble will pay better. StuRat (talk) 22:35, 7 December 2008 (UTC)

Calculating an average of the contents of the remaining boxes in the stress and pressure of the show may be unrealistic (at least until there are just a couple of boxes left). The likelyhood of making a slip in your mental math under the hot lights and with the adrenaline pumping is HUGE. What is needed is an algorithm that improves your odds AND which is really easy to remember and apply under pressure. I recommend sitting down with family members and picking a dollar amount that represents the amount of money that'll make a big difference to your life - an amount you would not be disappointed to walk away with. Let's say that amount is $20k. Now, instead of calculating an average - just add up the number of boxes that'll "make a difference" and the number that won't. If the offer they make you "makes a difference" and less than half of the boxes "make a difference" then take the offer - otherwise turn it down. If the offer they make doesn't "make a difference" turn it down unless none of the boxes make a difference either. This is a simple enough rule to keep in your head under pressure. This approach doesn't maximise your expected dollar return - but it does maximise the chances of you walking away with a huge smile on your face - which matters more IMHO. I very much doubt that (walking out of the studio) you'll very much care whether you won $100k or $200k. Considering the amount of money at risk here - you might want to consider getting someone to write a computer program to simulate various strategies so you can test them out. SteveBaker (talk) 02:12, 8 December 2008 (UTC)

Indeed, my answer on the Maths desk accounted for that. (It's a consequence of the diminishing marginal utility of money combined with the need for a risk premium. The additional utility of the extra 900 million is pretty small so isn't sufficient premium to be worth the risk.) --Tango (talk) 23:25, 7 December 2008 (UTC)

I'm sorry for splitting posts, I was corrupted to the dark side. I promise not to do it again unless money or women are involved :P Bastard Soap (talk) 09:06, 8 December 2008 (UTC)

Common descent

Not being very familiar with evolutionary biology, I was somewhat confused by Common descent: although it unambiguously states that the idea of a common ancestor means a single organism for all organisms living today, is this meant for specific types of organisms? Is it typically said that all animals have a common ancestor that isn't a common ancestor for plants? Or the finches: would it be normal to speak of a group of finches flying to the Galapagos Islands as together the common ancestors of today's finches? Nyttend (talk) 14:56, 7 December 2008 (UTC)

Any given population will have a most recent common ancestor, the more restrictive that population the more recent that ancestor will be (roughly speaking). The most recent common ancestor for all life on Earth was about 3 or 4 billion years ago (I forget when exactly), the most recent common ancestor for animals will be some time later than that (somewhere around 0.5 billion years ago, I think), the most recent common ancestor for humans is somewhere in the order of 10,000 years ago (estimates vary). You may also be interested in the identical ancestors point. --Tango (talk) 15:08, 7 December 2008 (UTC)

With asexual reproduction this is a fairly strait-forward question, since each organism has one and only one parent. But, with sexual reproduction, it becomes more complicated, since we each have 2 parents. Thus, we have 4 grandparents, 8 great-grandparents, etc. (assuming no interbreeding). This means 1024 forebears at 10 generations, over a million at 20 gens, and over a billion at 30 gens (around 1000 years). Now, this doesn't actually happen, because over those time scales you get a lot of interbreeding. However, when you go back hundreds of thousands of years, a rather large percentage of the human population back then became the forebears of any given individual now. So, there may have been more than one individual who is the common ancestor of everyone alive today.

A further complexity comes in with chromosomes. You have half the chromosomes of each parent, on average a quarter of each grandparent, etc. Again, that means that you would only have 1/1024 of the chromosomes of each ancestor from 10 generations back. And, since we only have 46 chromosomes, that means we have a 46/1024 chance of having a chromosome from each ancestor. Again, this math is altered based on interbreeding, but, if you go back far enough, the chances of having any one chromosome in common with a given ancestor is small. This was assuming random distribution, however. If a chromosome contained genetic material which made survival more likely, then you're more likely to have that chromosome from your ancestor. Then there's also the possibilities of genes moving from chromosome to chromosome and there are mutations to consider. So, how much genetic material we each have in common with our common ancestor or ancestors is quite complex of a question. And can you call someone your ancestor if you don't have any genetic material in common with them ? StuRat (talk) 16:42, 7 December 2008 (UTC)

These is certainly more than one common ancestor of any population (except possibly all life), since any ancestor of a common ancestor is a common ancestor. That's why it is the *most recent* common ancestor which is relevant. --Tango (talk) 16:57, 7 December 2008 (UTC)

Note that (with the exception of the Y chromosome, which is inherited only from the father, and of which most people have at most one copy) the odds are very poor that any single chromosome will be passed on intact for multiple generations. Genetic material is swapped between pairs of chromosomes by a number of mechanisms; crossing over (chromosomal crossover) is the most common. The likelihood of a crossover event taking place is roughly 1% per million base pairs (see centimorgan) of human DNA. Even the shortest non-Y chromosome (chromosome 21) is just shy of 50 million bases long, and the longest (chromosome 1) is about five times that.

In other words, if you examined one of your copies of chromosome 1 very closely, you almost certainly wouldn't find that it's identical to the chromosome 1 of one of your grandparents. It's much more likely to be grandma's chromosome 1 at both ends, with some of grandpa's chromosome 1 swapped in in the middle. This mixing and matching within chromosomes happens with each generation. In the example above, the odds are not 46/1024 that any given ancestor would have – by himself – supplied one of your chromosomes. Instead, the odds are essentially zero; no chromosomes are likely to have survived intact for ten generations without a crossover event. However, this does mean that the odds are pretty good that you will share at least some genetic material with each of your ancestors. Due to crossing over, it's likely that you'll have gotten a piece of DNA of some length from your eight-times-great grandfather. TenOfAllTrades(talk) 19:42, 7 December 2008 (UTC)

But to go back to the original question: No, it is not meant for specific types of organism only. The science of cladistics deals with formalizing the relationships of all living being. A recent common ancestor of all Galapagos finches was probably something we would call a finch. But the most famous ancestor of all birds would be a dinosaur. Richard Dawkins' The Ancestor's Tale is an excellent book, tracking back the ancestors that humans share with increasingly larger parts of life on earth. --Stephan Schulz (talk) 22:39, 7 December 2008 (UTC)

Displaying carbon and hydrogens in Symyx/ISIS draw

I'm trying to use Symyx (formerly known as ISIS draw) to draw some molecules but I can't get it to display the carbon and hydrogen atoms. I want all atoms of the molecules to be displayed. Anyone know how I can do it? ----Seans Potato Business 16:53, 7 December 2008 (UTC)

In my ISIS Draw...select a molecule, and then Edit Molecule (double-click the seelcted structyre, use right-click popup, or use the Object menu). There, in the Atom pane, you can control how the hydrogens are displayed. It looks like this always gives condensed structures ("CH_n") rather than drawing explicit bonds to H atoms. DMacks (talk) 19:18, 7 December 2008 (UTC)

This fixes the hydrogen isssue but not the carbon issue. I'm also unable to get the program to display the molecule at right angles. If I click Chemistry > Clean then bonds adopt more realistic angles which is not what I want. Trying to drag them into regimental order is labour-intensive an ineffective. ----Seans Potato Business 20:38, 7 December 2008 (UTC)

Not sure I understand what you mean (i.e., what you want it to to look like). Actually, I am sure I don't understand. Could you give us a sample diagram of what style you're trying to accomplish? DMacks (talk) 21:21, 7 December 2008 (UTC)

In this image, in the upper section, you see angled bonds (which I don't want) and in the lower section, regimental, right-angled bonds which I do want]. I also want every carbon atom to be displaced. I know it's possible somehow, because I'm looking at it in a text book. ----Seans Potato Business 21:43, 7 December 2008 (UTC)

A California earthquake causing an associated blackout and causing people to see the Milky Way

Hi. There was an earthquake in California that caused a blackout at night, causing people to run outside and see the Milky Way for the first time. Authorities and a local observatory were flooded with calls. I have also posted this at Talk:1989 Loma Prieta earthquake, which might have been responsible for this blackout, but it might also have been the 1994 Northridge earthquake, which struck in the middle of the night, and since I want this to be included in an article and I don't want to post OR, does someone know which earthquake it is, and preferably find a reliable source as well? Thanks. ~AH1^(TCU) 18:37, 7 December 2008 (UTC)

Here's information on a related event during the Northeast Blackout of 2003: [17]. --Jayron32.talk.contribs 18:47, 7 December 2008 (UTC)

I'm guessing not Loma Prieta; I didn't think to look at the sky, but lights were on in patches soon after dark. —Tamfang (talk) 08:50, 14 December 2008 (UTC)

Rhizobium

Hi the article on Rhizobium says that the bacteria convert atmospheric nitrogen to ammonia. My question is can plants use this ammonia directly to form their proteins etc or does it need to be converted to other molecules - e.g. nitrates before the plants can use them? Thanks. —Preceding unsigned comment added by 139.222.240.167 (talk) 19:58, 7 December 2008 (UTC)

See Nitrogen fixation#Biological nitrogen fixation and Nitrogen cycle#Assimilation. It looks as though the ammonia is quickly converted to ammonium ions, which are what the plants use. No doubt someone who understands this far better than I will soon be along with additional information. Deor (talk) 21:47, 7 December 2008 (UTC)

Long train journey

I had the misfortune today of having to catch a train from Preston to Southampton which took nearly six hours! I did a very simple calculation and worked out that the average speed of the train during the journey was 52 mph which seems very slow, particularly as it is supposed to be a main line service.

The first leg of the journey from Preston to Stockport via Bolton took 1:39 and is about 35 miles (according to a quick path-drawing excercise following the general route of the line in Google Earth). This averages around 21 mph although there were quite a lot of stops.

The main part of the journey, from Stockport to Southampton via Stoke, Stafford, Birmingham, Oxford and Reading (but with more stops than that, about 15 stops in total) took 4:09 and is about 214 miles. This works out at an average of 52mph.

The trains [[18]] are capable of doing 125 mph. I assume that not all of the lines it went on allow that speed and obviously slowing down and stopping at stations all wastes time but it stills seems very slow indeed to me. The Virgin Voyager trains seem to accelerate quite fast so I can't believe that and slowing down adds so much to the journey time.

If the train could average 80mph then it would easily do the journey in about 3 hours, which is a bit more bearable but why does going 250 odd miles take such a long time? I think I'll fly next time I want to travel such distances! Much quicker and usually cheaper too. —Preceding unsigned comment added by 62.249.220.179 (talk) 21:01, 7 December 2008 (UTC)

Slowing down, stopping, waiting in a station, and getting back up to speed again does take a significant amount of time. Say it adds on 5 minutes per station, you say there were about 15 stops on the main leg, that's 1hr 15 mins added on to your journey. There may also have been additional delays due to waiting for other trains to get out of the way or parts of track where the train had to go slowly (damaged rails, damaged bridges, sharp corners, etc.), which all adds up. --Tango (talk) 21:35, 7 December 2008 (UTC)

5 minutes per stop seems quite low. That might be how long they are actually stopped, but adding in the slow down and accel and you can probably double that. StuRat (talk) 22:15, 7 December 2008 (UTC)

Indeed, that was a conservative estimate. I was guessing at 3 minutes stationary and 1 minute breaking and accelerating (it will spend more than 1 minute doing those things, but it is moving, if slowly, so not all the time is lost). --Tango (talk) 23:21, 7 December 2008 (UTC)

It usually works out quicker although more expensive if you go via London. That's where the fast trains go. Very annoying for us provincials. Itsmejudith (talk) 23:29, 7 December 2008 (UTC)

Yes, it's just under five hours via London according to Traveline. It's eight hours by coach but that includes an hour's wait in Birmingham, giving you time to do some shopping.--Shantavira|^{feed me} 09:05, 8 December 2008 (UTC)

The biggest problem with this sort of journey is that the rail system was never designed that way. In fact it wasn't designed at all, but grew somewhat organically depending where the railway companies (no national organisation in those days) thought that they could make some money. Presumably no-one thought that there would be much call for paying customers to travel your route, so you have to make use of the tracks that actually were built (and those not subsequently ripped up in the time of Beeching). Cross-country routes like this one are generally hampered by the need to use parts of the major routes and they have to wait their turn to fit in with the express trains. I've had my share of journeys like you describe, just try your best to feel noble about your reduced carbon footprint. Mikenorton (talk) 18:32, 8 December 2008 (UTC)

So lets say the train does 0 to 60 in ten seconds after every stop... not one for the old folks anyway. Wouldnt work the best if you were standing at the toilet. ~ R.T.G 12:50, 9 December 2008 (UTC)

Citrus identification

Can anyone identify this citrus tree? The fruit are about 3 inches (7.5 cm) in diameter, with orange skin and greenish pulp. The taste is like a lime, and very sour. [19] --Amble (talk) 23:18, 7 December 2008 (UTC)

Likely it's Mandarin lime – Citrus limonia is a hybrid. Julia Rossi (talk) 01:07, 8 December 2008 (UTC)

Thanks. I considered that one but doubted it because of the flesh color; it's greenish-yellow instead of orange. --Amble (talk) 05:48, 8 December 2008 (UTC)

I found it tricky too, but it's the pulp that makes it different. The article could use more images. : ) Julia Rossi (talk) 06:01, 8 December 2008 (UTC)

December 8

Carbs from Vegetables

Sort of 3 questions:

1. Does anyone know of a place that lists the amount of carbohydrates, protien and fats in typical vegetables (brocolli, colliflower, protatoe, pumpkin, carrot, etc.)?

2. What is the scientific consensus on eating non-starch vegetables (ie no potatoe or pumpkin) as the only source of carbohydates in a diet (ie no bread/rice)? Not asking for medical opinion, I just want to know if scentifically the body can get all the carbs it needs from only non-starchy vegetables.

3.Before cultivation, what was the source of carbs for hunter/gatherers? And in what period did the majority of the earths population start eating mainly cultivated food instead of hunting/gathering for food. --Dacium (talk) 01:39, 8 December 2008 (UTC)

1. USDA food database

2. Humans don't need carbohydrates at all. See gluconeogenesis. If a chemical is classified as "nutritional fiber" that means that humans cannot digest it, and while human intestinal bacteria can digest some sorts of fiber, they (the bacteria) mostly live in the colon where monosaccharides cannot be absorbed into the body anyway. Icek (talk) 02:22, 8 December 2008 (UTC)

3. See Neolithic Revolution.

Icek (talk) 02:22, 8 December 2008 (UTC)

Thanks! About number 2, why is it that low carb diets seem to be not recommended scientifically? Upon reading most of the articles I could find here (such as low carb diets etc) it appears the lack of carbs itself is ok, but they don't recommend it because people eat to much fat or protien?

If a diet is just non-starch vegetables, eggs, nuts and lean meat (ie no excessive protien or fat), is it scientifically considered healthy?--Dacium (talk) 02:38, 8 December 2008 (UTC)

Actually, most recent science actually supports the low-carb, high-protein diet as the most healthy. The "low fat, high carb" diets of the past have been more recently shown to be quite a bit LESS healthy. This radio broadcast: [20] discussed in detail a recent Israeli study that compared 3 diets: The "atkins style" low carb diet, the "ornish-style" low fat diet, and the "mediterranean diet" seen as lying somewhere between the two. It found that the rank-order for healthful outcomes among practitioners of the diet was 1) Atkins 2) Mediterranean and 3) Low-Fat. Here is the original article, published in the New England Journal of Medicine: [21] Here's another article: [22] that cites two different studies from 2004 which show unequivocally that low-carb diets beat low-fat diets in lowering both blood cholesterol levels and blood triglyceride levels. We have a carry-over from the old days when "low fat" was everything, but most modern studies seem to be leaning more and more towards "low-carb" diets. --Jayron32.talk.contribs 03:47, 8 December 2008 (UTC)

The study you mention is a weight loss study. Even if a lot of people's health would benefit from losing weight, a healthy diet is a diet that keeps your weight the same, and that you can live on for years and years without suffering from any nutritial deficiencies. As for your claim that the high-protein diet is the most healthy, neither of the articles even discusses if people get enough vitamins and minerals when they eat low-carb, high-protein. I don't recommend eating rice or bread, but vegetables and fruit (= carbs) are important sources of vitamins and minerals. Lova Falk (talk) 20:56, 8 December 2008 (UTC)

When I hear people making such arguments about getting sufficient vitamins and minerals I wonder whether they don't realize that one can easily get these micronutrients in concentrated form e. g. as pills which is often more convenient than e. g. eating relatively large amounts of carrots for a little vitamin A. After all, scientists have figured out which chemicals are behind the vitamins; it's not like the 18th century when it was only known that lemons and sauerkraut prevent scurvy, it has been pinned down to ascorbic acid. So why not use modern science and technology? I don't want to say what's a healthy diet but that vitamin deficiencies are actually easily solvable problems (vitamin pills aren't expensive either).

By the way, it seems to me that the results from the NEJM article cited by Jayron32 has more to do with the psychology of eating habits than with healthy nutrition. Icek (talk) 01:31, 11 December 2008 (UTC)

This site has it all. -hydnjo talk 04:01, 8 December 2008 (UTC)

Non-starchy vegetables are generally high in sugars, so they do supply "carbs". They are generally also high in micronutrients and in fibre, which is why they are a useful part of the diet. If you fancy fish and broccoli for dinner, with no potatoes, go ahead, but adding one or two small potatoes won't kill you either. Itsmejudith (talk) 08:49, 8 December 2008 (UTC)

Mushroom Substrate

what makes a good mushroom substrate, that doesn't involve vermiculite? i can't find one on the internet so i'm asking u guys. —Preceding unsigned comment added by 76.14.124.175 (talk) 02:40, 8 December 2008 (UTC)

At Fungiculture we've got a substrate section[23]. And google has a range[24], but what is "good" needs someone who knows – Julia Rossi (talk) 02:48, 8 December 2008 (UTC)

thanks! —Preceding unsigned comment added by 76.14.124.175 (talk) 03:14, 8 December 2008 (UTC)

Fixed link – you're welcome,  : ) Julia Rossi (talk) 04:31, 8 December 2008 (UTC)

Penn & Teller ? StuRat (talk) 14:24, 8 December 2008 (UTC)

Compressing Water

I've heard that compressing water (like compressing air in an air compressor) is extremely difficult, borderline impossible. Why is this, when there is plenty of space between water molecules? [[User:Shane 42]] (talk) 04:09, 8 December 2008 (UTC)

There isn't much space between the liquid water molecules...when water changes from liquid to solid, it's volume actually increases! With most liquids the volume of the liquid and solid is the same - so most liquids are no more compressible than their corresponding solids. The molecules only separate out when they form a gas - ang from 20001 to 20002 atmospheres (perceived). Water is compressible, but only at pressures comparable to 20000 atmospheres. HTH, Robinh (talk) 08:14, 8 December 20d the volume of one gram of gaseous water (steam) is MUCH larger than one gram of liquid water or ice. Hence, steam is very compressible - but water and ice are not. SteveBaker (talk) 04:51, 8 December 2008 (UTC)

See equation of state#Other equations of state of interest (stiffened equation of state). Water is like air already under 20000 atmospheres, so changing from 1 to 2 atmospheres (real) pressure is like water changin08 (UTC)

Due to the hydrogen bonding between water molecules, there is actually little to no space between them - the formation of crystalline ice disrupts the hydrogen bonding, which is why water expands when it changes state to ice. Bobzchemist (talk) 18:07, 8 December 2008 (UTC)

UK DNA taken from criminals

How do the police get this? Kittybrewster ☎ 08:23, 8 December 2008 (UTC)

Usually with a cotton swab on the inside of the cheek.--Shantavira|^{feed me} 09:10, 8 December 2008 (UTC)

"So Mr Jones - would you care to explain how we came to find your DNA all over that cotton warehouse down by the docks on the night in question?" SteveBaker (talk) 13:56, 8 December 2008 (UTC)

Human body voltage

I just held the leads of my multimeter, and sure enough, there was a 60mV difference between my left hand and my right hand (the right hand being the "ground"). Sure enough, when I switched hands on the leads, it read -60mV, and when I let go, it popped back to 0, so I doubt it's a fluke of the multimeter itself.

Does anyone know of any articles or external links as to what my be causing a measurable electric potential between a human's extremities? And is it actually normal, or am I turning into Elle Bishop? :) --Link ^(t•c•m) 08:43, 8 December 2008 (UTC)

60mV is an incredibly small difference - it could easily be caused by some kind of inductive pickup in the wires leading to the meter. I would do two things:

1. Try doing the experiment while standing in different places in the room - also outdoors - and see if this number changes (I bet it does)
2. Try reversing the leads an seeing if it still reads 60mV-ish...which would suggest an inaccuracy in the meter.

I'm pretty sure you aren't abnormally turning into "The Human AA". Be careful with measuring yourself with a meter...people have died trying to accurately measure their resistance on the ohms scale! (Although you should be OK on the volts scale).

SteveBaker (talk) 13:54, 8 December 2008 (UTC)

Indeed - be careful! Whatever you do don't pierce the skin, once you are through the skin your resistance is very low and the high voltage used to measure it can kill you (as Steve says, measuring voltage should be safe, it's a pretty passive test, but it's not worth risking it). --Tango (talk) 15:29, 8 December 2008 (UTC)

That'd be very difficult to do with a battery-powered meter, as the voltage cannot be possibly higher than the one provided from the batteries, and, the last time I tried that, even the resistance between the two sides of my tongue was several kilohoms. -- Army1987 – Deeds, not words. 15:35, 8 December 2008 (UTC)

The thing about measuring across the tongue is that your heart isn't on the path between the two probes - so it's relatively safe (I say relatively - because if one hand happens to be touching some metal part of the meter...and the other probe is on your tongue - then maybe you are still in trouble). But measuring resistance from one hand to the other puts your heart right in the firing line. The "I did it and got away with it" argument also applies to crossing freeways while blindfolded. SteveBaker (talk) 16:37, 8 December 2008 (UTC)

Nevertheless, it has happened. The voltage can easily be higher than that of the batteries, you just need a transformer, although actually now I think about it is probably current that is the risk, not voltage. --Tango (talk) 15:38, 8 December 2008 (UTC)

It's the current that's the danger, I think there was a Darwin Award for someone who killed himself with a multimeter - the electrodes pierced his skin, and the current caused a heart attack. DuncanHill (talk) 15:41, 8 December 2008 (UTC)

In this case, the current isn't enough to zap and kill a person. However, it is enough to cause fibrillation. The chance of fibrillation in a healthy adult is small. In a person with a pacemaker or heart disease, the risk is increased. Whenever I hear about the volt/current argument, I can't help but remember reading specs on a railgun that used a teravolt generator that had very low current. The warning was: "They say volts won't kill you. That is true. A few thousand teravolts won't kill you. It will vaporize you." -- kainaw™ 15:52, 8 December 2008 (UTC)

Yes, the current is the danger (or more precisely the charge, you need around 60 mC IIRC), that's why I mentioned my resistance. Assuming the ohmmeter uses 4.5 V, and a resistance of 30 kΩ, you'd get 0.15 mA, so you'd need to wait 400 seconds before any significant danger. YΩMV, but I don't think that in "normal" circumstances you could get a much higher current through your body with a "normal" multimeter. (BTW, are there really transformers working with DC?) -- Army1987 – Deeds, not words. 16:03, 8 December 2008 (UTC)

Every time I say this - we have the same debate - the fact is that more than one person has actually, for real, died from doing this. So if your theory says that it can't happen then you need to find a new theory because your old one just met with reality and didn't come off so well! SteveBaker (talk) 16:37, 8 December 2008 (UTC)

Where did you get the 30kΩ figure? Are you remembering that we're talking about the resistance of the inside of the body (you have to pierce the skin first) which is essentially salt water? Salt water has a pretty low resistance. --Tango (talk) 16:43, 8 December 2008 (UTC)

Sorry, but can we have a WP:RS that says that someone died from the electric shock of a passively used multimeter? I can easily imagine all kinds of accidents with a multimeter and live cables, but I have trouble believing in the lethal power of a bog-standard battery that is used in many millions of toys without adding in a lot of stupid-smart electronics. --Stephan Schulz (talk) 16:47, 8 December 2008 (UTC)

The award Duncan refers to is at http://darwinawards.com/darwin/darwin1999-50.html. I had not understood that the winner had done that. If you reach blood, resistance will be low enough. (But it's somewhat unlikely to happen accidentally, at both terminals. And measuring voltage as the OP was doing shouldn't be very dangerous.) -- Army1987 – Deeds, not words. 16:52, 8 December 2008 (UTC)

I haven't re-read the Darwin award, but I believe it was done intentionally. I agree it's not likely to happen by accident, but nevertheless caution is warranted. --Tango (talk) 17:06, 8 December 2008 (UTC)

← (e.c.) Also, if you have a pacemaker you can kill yourself with a smaller current, indeed those body fat measuring scales recommend that pacemaker users don't use them. -- Army1987 – Deeds, not words. 17:10, 8 December 2008 (UTC)

A factor that must be considered is the internal resistance of the voltage source. If the internal resistance is high, it will reduce the current for any given external resistance. That's why "shocking coils" do not harm people. —Preceding unsigned comment added by 98.17.46.132 (talk) 17:20, 8 December 2008 (UTC)

I think stun guns have caused death. Does anybody know the open-circuit voltage of a typical stun gun? ("Open circuit" means measured with a very high-resistance voltmeter. I don't think voltage can be measured without imposing some sort of load - shades of Heisenberg.) Some stun guns use body contact from 2 prods. Others use penetrating barbs on the end of wires; the barbs benetrate the skin and stick there to give the shock. The barb kind is obviously more dangerous, unless the prod type touches an open cut, mosquito bite, etc. Sweat on the skin also enters into it. —Preceding unsigned comment added by 98.17.46.132 (talk) 17:40, 8 December 2008 (UTC)

Does anybody know the internal resistance of a typical stun gun? If the internal resistance and open-circuit voltage are known, the current can be calculated for any given external load. If the external load is assumed to be zero, that will reveal the maximum current that the stun gun can impose. It should be less than lethal. —Preceding unsigned comment added by 98.17.46.132 (talk) 18:02, 8 December 2008 (UTC)

Are you claiming that a stun gun applied to the internal body (below the heavily resistant human skin) is in no way lethal? Much of this topic is discussing the possibility of harm or death by applying voltage/current below the skin - especially to the blood, which is highly conductive. -- kainaw™ 18:25, 8 December 2008 (UTC)

In general, the probes for a stun gun should be close together, which would make the current path relatively local. This would tend to reduce the risk of applying fatal current to the heart, and is rather different than applying a multimeter or other current source to both hands. Dragons flight (talk) 19:08, 8 December 2008 (UTC)

I don't believe the Darwin Awards story. Just because some guy from the US Navy says it's true doesn't make it true. Note the word "Unconfirmed" at the top of the article. Where is the original report? And if you can kill yourself with a 9-volt battery and two pins, why has it happened only once in recorded history? And why never with a 12-volt car battery, or a 9-volt plug-top transformer, or a PC motherboard with all those jumper pins sticking up?

Anyway, returning to the question, I can get very close to the same results as the OP if I repeat the experiment enough times. Most of the time, though, the readings are apparently random in polarity and magnitude. My guess is that the voltage across your fingers is some messy waveform related to the sinusoidal mains voltage that your body picks up like an antenna, and to your body position and skin resistance. A cheap DVM set to DC will probably convert this waveform into a more or less random reading depending on the shape of the waveform. If you've ever looked at the waveform on an oscilloscope when you hold a high-impedance scope probe in your finger then you'll know what I mean. Imagine that the DVM is taking samples at random points on that waveform, or at least trying to average it with a very poor averaging circuit. --Heron (talk) 20:50, 8 December 2008 (UTC)

Electrical current flow in the human body is 3-dimensional. Usually, we think of electrical current as electrons flowing between 2 points in a narrow stream through a wire - essentially a 1-dimensional flow. However, electrons repel each other, so the flow in a 3-dimensional conductor is different. The following simple demonstration will show this. Fill a cup or glass nearly full with tap water. Dissolve some table salt in the water. Put the two prods of an ohmmeter in the water and adjust the meter to show the resistance between the prods. Now move the prods closer together, then farther apart. There will be no noticeable difference in resistance regardless of the spacing of the prods. This is because the electrons can spread out and have a great many parallel paths between the two prods. Unlike a typical wire-resistance measurement (essentially one-dimensional), the width of the salt-water conductor is very large compared to the distance between the prods - hence the current path is 3-dimensional. (The current flow resembles, in 3 dimensions, the "lines of magnetic force" shown by iron filings on a sheet of paper placed over a bar magnet.) Some electrons in the salt water demo will actually move away from the positive electrical pole at first, then swing around toward it. Between the two electrical poles, electron distribution will have approximately an even density across all parts of a plane normal to electron flow. (The boundaries of the cup or glass, and the surface of the water, are the approximating factor, as compared to a container of infinite size.) In the human body, electrical current from an externally-applied voltage will flow in the same manner. If a voltage is imposed between two points on the torso on opposite sides of the heart, and the heart is not directly between those two points, the spread-out of current will still give the heart the full current of that plane. (A complicating factor is that different bodily organs will have a different specific resistance. The outer boundary of the body is another complicating factor.) If a voltage is imposed at two points on the same arm or leg, the heart will experience very little of the current. So it is torso-applied voltage, or hand-to-hand applied voltage, that is lethal when the voltage is sufficiently high and the internal resistance of the voltage source is sufficiently low. —Preceding unsigned comment added by 98.17.46.132 (talk) 21:06, 8 December 2008 (UTC)

A 60mV difference is nothing. There's about a 200 V difference in the air between your head and your feet: [25], due to the inherent potential gradient in the atmosphere... --Jayron32.talk.contribs 21:59, 8 December 2008 (UTC)

Hold on there. Between two points, vertically spaced with 2 metres, there might be a 200 volt voltage, but only until you connect the points with a human body or another conducting object. When you do that, you short-circuit the voltage you originally had. As an equivalent example, consider a 9 volt battery. What is the voltage between the electrodes? It's 9 volts, of course, but what happens if you connect them with a piece of wire? The voltage drops to essentially zero. —Bromskloss (talk) 13:05, 9 December 2008 (UTC)

This anecdote of death by Simpson 260 sounds like an urban legend, since the meter does not place a 9 volt battery in series with the two test leads. Instead it has circuitry including the calibration rheostat, perhaps scaling resistors, and the meter movement in series. The present Simpson 260 manual [26] says (p9) the maximum short-circuit current on the ohms times 10000 scale, where the 9 volt battery is used, is 75 microamperes. For the RX1 and RX100 scales, it uses just a 1.5 volt battery. The meter movement itself is 20,000 ohms per volt and 50 microamperes full scale. The short circuit current on the RX1 scale is 125 mA, but note that is for a SHORT CIRCUIT, which the human body is not. I have seen safety bulletins in the past which contained myths intended to scare readers away from doing things which might lead to injury, such as if a person did the meter experiment with a source of greater current at higher voltage, or with an ammeter and a high energy source. I do not deny that under contrived conditions such as implanted electrodes it might be possible to cause electrocution with a 9 v battery. Edison (talk) 04:02, 10 December 2008 (UTC)

The following site says there has been several hundred deaths from stun guns in Britain alone. It also says 50,000 is typical for a barb type stun gun. —Preceding unsigned comment added by 98.17.46.132 (talk) 06:39, 11 December 2008 (UTC)

Longevity

I was just wondering - even if we extend average life expectancy to beyond 90 or 100, wouldn't we spend a good chunk of those last years blind deaf and frail - as we haven't worked out how to fix age-based deterioration in sight and hearing amongst other things. Paul Austin (talk) 11:09, 8 December 2008 (UTC)

Well, my visual prosthesis and cochlear implants are working fine, but that doesn't help my ... other thing ...begins with "m" ... what was the question ? Gandalf61 (talk) 12:19, 8 December 2008 (UTC)

Actually - I think the reverse is true. We've made such improvements in fixing things like eyesight, hearing and such that now we find many people are dying while they still have a lot of productive years ahead of them. SteveBaker (talk) 13:48, 8 December 2008 (UTC)

Have we really? My aunt is slowly getting blind and there is nothing anybody can do about it (I don't know her condition). Anyway, instead of jokes and opinions, isn't there any research done? The quality of the last ten years of people's life now compared to a previous period. Should be possible to do, but has anybody done it? Lova Falk (talk) 16:51, 8 December 2008 (UTC)

Actually, I am going to disagree with SteveBaker here. In the U.S. at least (can't speak for elsewhere) we have the means to both extend the life and improve the quality of that extended life; however we lack the political will to do so in an effective and equitable manner for all people. Essentially, the haphazard manner in which healthcare is handled in the U.S. actually provides both problems (i.e. people dying while still productive AND people living well past the usefullness of their own bodies). Both are solvable with modern medical technology; but given the poor access most people have to health care, it is likely we won't see any widespread universal system for providing both kinds of care to all people. --Jayron32.talk.contribs 21:54, 8 December 2008 (UTC)

I know a number of people in their 90's, in the U.S., who live self sufficiently and participate in a variety of activities. Time eventually catches up with them, but many have had a "hale and hearty" lifestyle well past 90. I knew a lady of 104 who was in a wheelchair and in a nursing home, but who could see and hear fine and was apparently of sound mind. Certainly some people have a stroke or Altzheimers decades earlier, or become blind or deaf. Edison (talk) 03:21, 10 December 2008 (UTC)

Island of Stability

Does anyone know of any images representing the graph of stabilities of nuclei, other than the one linked on the article? Specifically I was looking for something showing the 'sloping' of elements towards stability.

Cheers,

—Cyclonenim (talk · contribs · email) 14:27, 8 December 2008 (UTC)

In the first picture in the article Island of stability, height indicates stability, so you can really see that sloping towards the stable peak. Click on the picture to get a higher resolution, it was awfully hard to read on my screen at least. EverGreg (talk) 15:36, 8 December 2008 (UTC)

I agree that it's a good image and very helpful; however, I was looking for a kind of inverted image that showed the most stable nuceli in a sort of ditch. The reason for this was because the example we were given in class was like a ball rolling down a hill, and it'd be a good way to indicate it. —Cyclonenim (talk · contribs · email) 17:51, 8 December 2008 (UTC)

Wikipedia, Censorship and Child Pornography

I was reading about how the UK has banned the Wikipedia article on the Scorpion's Virgin Killer because the original album cover had a naked child. I understand that Wikipedia is not censored. But it made me wonder what images are in the child pornography article. I hesitate to look at the article because I'm at work (not to mention I personally might find it disturbing). Can an editor upload hard-core child porn and justify it by saying Wikipedia isn't censored and that's what the article is about? Or how about showing the images that Gary Glitter was imprisoned for? 216.239.234.196 (talk) 18:20, 8 December 2008 (UTC)

An editor can upload any image and make any claim he or she would like to make. That doesn't mean that the other users have to accept it. With far more people acting in a sane and reasonable manner, those who just want to be a dick are kept in check. -- kainaw™ 18:23, 8 December 2008 (UTC)

For the record, child pornography presently has no images of children or of pornography. Dragons flight (talk) 18:26, 8 December 2008 (UTC)

Also, I think you misunderstand the whole not-censored idea. If something is morally opposed, Wikipedia will not remove it as it is not censored to personal belief. The only circumstance in which something is removed is if it is against the law where the servers are held (I think it's Los Angeles but I could be wrong). Child pornography images (not potential images but explicitly proven images) would have to be removed by law in LA. —Cyclonenim (talk · contribs · email) 18:35, 8 December 2008 (UTC)

Actually the servers live in Florida, but your point is otherwise correct. Dragons flight (talk) 18:59, 8 December 2008 (UTC)

So if Florida rules that Virgin Killer album is illegal, then it will be removed? What about images that have not yet been ruled child pornography? What's to stop somebody from uploading child porn images to the child porn page and then (accurately) claiming that if they haven't been ruled illegal yet, then they must stay? I guess the other editors, right?

Also, I just realized that I accidentally posted this to the Science desk. I meant to put it in the Humanities desk. Is it OK if I move it? 216.239.234.196 (talk) 19:06, 8 December 2008 (UTC)

You can move the question, but it has already been answered. One user demanding that an image is legal and must be kept is not enough to keep it on Wikipedia. This is a community. One use cannot force an image to be on a page against the wishes of the community. So, the community will keep a user from exploiting Wikipedia policies to be an annoyance. -- kainaw™ 19:09, 8 December 2008 (UTC)

See the Miller Test. I think everyone would agree that an album cover has "artistic merit", and so is going to be legal in the US pretty much regardless. Though we don't have the finality of a court of law, I think in general Wikipedians are likely to apply a similar standard to Miller in deciding whether something should be included or not. Dragons flight (talk) 19:13, 8 December 2008 (UTC)

It also should be noted that the furor over this album cover is rediculous. I can buy this album, underage penis and all, at my local WalMart. I checked. The greater issues are legion, however:

1. A non-governmental agency is allowed to control content for ISPs which cover 95% of Britain, without means for formal redress should mistakes be found.
2. The method of censorship is unneccesarily disruptive (the use of transparent proxies) where other, less disruptive means are availible and easy to implement. The end result (preventing users from seeing the image) could have been achieved without funneling access from essentially all of the UK through 12 IPs. Furthermore, even using the transparent proxy method, the ISPs involved could implement an XFF standard which would essentially allow a users original IP address (and not the proxy's) to be seen by Wikipedia.
3. The censoring of the image can be easily bypassed by using subtle variations on the URL, which means that the censorship of the image itself is both unreasonably disruptive to the free flow of information (see above) and entirely ineffective in actually censoring the image.
4. The blacklist in question has blacklisted BOTH the image and the article about the album. One could make a justification for censoring the image which is consistant with "community standards" over child-pornography. However, the blocking of access to the text of the article, which contains nothing at all which could be construed as pornographic, is outrageous, and is again why problem #1 (having no means of redress) is such an issue.
5. The parties involved (the ISPs individually and the IWF specifically) have been unreasonably flippant about working with Wikipedia or the Wikimedia Foundation to solve the problem, despite the relative easy with which a solution could be worked out, and the potential media shitstorm that could result by being so flippant. If the IWF or the involved ISPs responded to the problem in a reasonable manner, this would have been solved days ago. The fact that they seem to be uninterested in working out a solution has resulted in an unneccesary escalation of the problem in the media, which is NEVER a desirable outcome.

None of these problems have anything at all to do with the actual censorship of the objectionable image. Arguements could still be made that the image should be censored; however that is NOT the major issue at hand here. The major issue is the irresponsible manner in which the involved parties have handled the censorship. --Jayron32.talk.contribs 21:10, 8 December 2008 (UTC)

For further info about the IWF blocking problem see Wikipedia:Administrators' noticeboard/2008 IWF action. Gwinva (talk) 21:34, 8 December 2008 (UTC)

Also, didn't Wikipedia move its servers to San Francisco? (Also I think the Nevermind album also has a similar image if I remember correctly but it doesn't seem to be banned). ~AH1^(TCU) 23:29, 8 December 2008 (UTC)

Servers still live in Florida. The administrative offices are in SF. Dragons flight (talk) 00:44, 9 December 2008 (UTC)

Yeah but the Nevermind album is a pic of the real life miracle of a babys ability to swim before he can walk. The other one is a picture of a little girl with something unusual looking around her vagina and, is it a picture of a "virgin killer" or a picture of what a "virgin killer" should or has targeted? Valid arguement against it but as per Wiki usual people will compare this picture to the Nevermind album, the added tasks and descisions regarding censorship, showing an oil painting of Mohammed and say "Oh if you censor that we wont be able to show anatomy or naked people kissing." Rubbish but hopeless to argue with. Well done for pointing it out anyway. It is a pity the word "pornography" dominates the debate about a picture which is obviously part of an artists protrayal of maliciousness towards a small girl. Sex is not evil but the creation of that album cover was certainly not all halos and polka dots. So long as people farm animals against their own animal cruelty laws, morals will be confusing unless directly affected in a negative way. Closed Community - 1 Wider Community - 0, Open to anything - 1 Open to everything - 0 ~ R.T.G 00:22, 9 December 2008 (UTC)

It is not proven despite numerous studies that the viewing of "real" child pornography, or violent pornography, leads to abuse or proves an intent to abuse. Therefore, anyone criminalized by viewing extreme material or mere nudity in the case of this image, is a victim of false abuse and imprisonment. Censorship is crime, as are visual pseudo-crime laws. It is interesting to conjecture the possibility of a libel action by those falsely accused of sexual criminality under these thought-crime laws. False abuse industry figures such as John Carr and Jim Gamble would be seriously out of pocket. This is nothing to do with protecting children from sexual predators-it is a moral crusade. —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 07:20, 9 December 2008 (UTC) Trevor Loughlin (talk) 07:21, 9 December 2008 (UTC)

Just as the word "pornography" is not the best description of the problem with this particular item, the claim of persecuting the viewer is not really a good part in this debate. Wise up Trev. You are defending the guy who breaks his ankle in a pot hole in case he is sued for the dangers the pot hole created... Censorship is a crime huh? Spitting on the phrase "moral crusade" in general... You probably have a low opinion of Mother Theresa. I am white. Bring back slavery I say. Two sugars please. Persons like you help to make drugs illegal because you prove that it may be absolutely neccesary because you do not respect the fact that some humans can be real evil fucks and we have all survived it. You would have it all go to crap and watch it just becase nobody has watched it going to crap for ages. Not one for the zoo or the carnival except a carnival of horrors. Sorry for the language. False abuse industry? Out of pocket? Stuff? Nonsense? Its as though some sort of group is trying to control our country by their own opinions. Prevent people having guns without a license? That would be a crime or a restriction or something. No difference between guns and candy floss. Every kid should want one. Blah. ~ R.T.G 12:45, 9 December 2008 (UTC)

You know, it brings up the question of "What is child pornography?". I don't find either image (Nirvana or Scorpions) remotely erotic. But maybe somebody else does? Out of 6 billion (or so) people on the planet, if one of them finds them erotic, is it child pornography? 216.239.234.196 (talk) 13:52, 9 December 2008 (UTC)

Unfortunately, that standard can never be applied with any sort of usefulness. There are people who get sexually aroused by pictures of clothed children, and yet we don't outlaw pictures of children altogether. In the U.S. the Miller test defines obscenity in all of its forms, though I can't speak to similar principles in other nations, I imagine some sort of "community standard" principle exists in many other nations. --Jayron32.talk.contribs 16:57, 9 December 2008 (UTC)

When I was small the film The Exorcist was banned. I thought there was too much hassle over films where people got hurt in similar ways you might see in an engineering mill or to much hassle over creatures which arent much more scary than your mild mannered dinosaur. As it turned out the film has stuff like a ten year old girl who when she is finished puking on hereself takes to stabbing her own vagina screaming "fuck me Jesus". The "Virgin Killer" piece is not the same as Nevermind. Again, talk about peoples ideas of clothed children... it's not quite hitting the button. The album definitly hits some sort of button. If it is not an erotic and/or abusive one... please go in to what it is because to be fair, what else is it? If it could be construed as something else it would be the first thing described rather than comparing it and defending it blindly. The only arguement here outside of quoting standards is that if one could watch paedophilia without joining in that it should be available to all. Who is up for that? I wonder. ~ R.T.G 00:11, 10 December 2008 (UTC)

Personally - I don't give a damn what sick shit people look at. What bothers me is what the kid went through in order for the picture to have been taken in the first place. We need laws that prevent those children from being involved - and to punish those who get the children involved. But once that has played out - what's done is done and the actual album cover is somewhat 'meh'. I don't have a problem with Wikipedia showing it in an appropriate context - just so long as we're not encouraging more people to do that kind of thing. The time to worry about this was when the album was released - and the people to hassle about it are the ones who commissioned, photographed, published, initially printed and violated the rights of that poor kid. They should all have gone to jail. SteveBaker (talk) 02:43, 10 December 2008 (UTC)

• Since this is a ref desk, not an opinion post, I'm not sure we need do much more here than direct the OP to Internet Watch Foundation and Wikipedia which covers the issue and provides links to various media commentaries. Gwinva (talk) 02:50, 10 December 2008 (UTC)

Yeah Gwinva but it is so weird the way Wikipedia debates this topic. The main concensus is that anything goes, had better go and questioning that is something wrong. How weird is that? That girl, now a 40 or 50 year old lady has to make the psychology of not giving a shit or she does give one and feels bad forever. It's indecent (that doesnt mention anything about sex, clothes, community groups, local law anything it's very plain in its own right "virgin killer" destruction of innocence, poison of the mind pure and by design). ~ R.T.G 06:32, 10 December 2008 (UTC)

Post-docs

When did post-docs become the common path of career progression in the sciences? Our article on the topic doesn't provide much history. My impression is that pursuing faculty positions immediately following one's PhD used to be much more common in the sciences than it is today. Dragons flight (talk) 19:02, 8 December 2008 (UTC)

That's probably correct. The American Physical Society probably has the statistics on that. --98.217.8.46 (talk) 01:37, 9 December 2008 (UTC)

My guess is it coincided with the increase in number of PhDs compared to available faculty positions. This combined with the greater mobility and perhaps larger number of places countries likely to be of interest to a scientist Nil Einne (talk) 12:32, 11 December 2008 (UTC)

Continuously-cooling device?

Apparently some people from Stanford created a zero electricity cooling device, which you use by heating it over a fire, and then it cools way down to refrigerator-like temperatures.

First, I'm wondering how the device works. I wasn't able to much out about that. I'm guessing that it's some long-running endothermic reaction (which thus sucks in heat), which is jump-started by heating the chemicals up until the reaction starts. Is that likely?

Second, I'm wondering if there's anything theoretically against having the same system (if it indeed works as described above), where the chemical reaction starts at room-temperature (specifics of the actual chemicals used aside)? If so, would it "yo-yo" back and forth between freezing, warming back up to room temperature, and then freezing again? And, since there is an energy gradient from which presumably you can draw energy, would this provide a continual "free" energy source, which would gradually suck up heat from the Earth? (Yay! Free energy until we all freeze to death!)

Thanks! — Sam 63.138.152.238 (talk) 20:14, 8 December 2008 (UTC)

This isn't a new concept. It most likely works on the same principles as an icyball which I believe predates modern compression refrigerators. Unfortunately the process wouldn't work at room temperature so no free energy here.-- Mad031683 (talk) 21:03, 8 December 2008 (UTC)

(edit)I should actually read the articles I link, It's from the 20's though still not new. -- Mad031683 (talk) 21:05, 8 December 2008 (UTC)

Absorption refrigerator? ~ hydnjo talk 22:22, 8 December 2008 (UTC)

But is there anything against there being a chemical reaction of this kind that takes place at or below room temperature, besides the fact that none has been found (or is likely to be found) with what we have at our disposal? — Sam 146.115.120.108 (talk) 03:51, 9 December 2008 (UTC)

The laws of thermodynamics are a harsh mistress. Certainly there are chemical reactions that do these kinds of things - but the energy in that case comes from (or winds up in) the chemicals. That doesn't give you 'free energy' that gives you energy from reacting chemicals...which isn't 'free'. SteveBaker (talk) 04:18, 9 December 2008 (UTC)

If at any point you reach the conclusion that something provides "free energy" there's an error in your reasoning. The laws of thermodynamics are pretty fundamental to our understanding of the universe, something that violated them would invalidate every theory we have, which is problematic since we have working technology and centuries of experiment prove the laws to be true. -- Mad031683 (talk) 17:31, 9 December 2008 (UTC)

Traction for tires.

Static (non moving) friction is stronger than kinetic (sliding) friction. This means that once an object (such as tires) start to slide, it has less friction strength to push in the opposite direction. This is demonstrated when our car gets stuck in snow. It's easier to drive slowly out of being stuck than by trying to spin our tires. So why is it that dragsters spin their tires? They should have less available traction and thus just sit and spin.

A corollary to this question, if I may. Once I have an explanation of why dragsters spin their tires for more forward movement, I will want to know if it is possible to stop faster with the tires driven in reverse (naturally, being aware that the tires spinning in reverse will lose directional control, but that is not my present question).

Thankyou.

Doug —Preceding unsigned comment added by 192.30.202.21 (talk) 23:51, 8 December 2008 (UTC)

I thought they melted the tires a little so that it would stick to the track, providing greater grip. I'm sure you can find the answer on the appropriate wikipedia page. 96.242.34.226 (talk) 00:06, 9 December 2008 (UTC)

Yep, that's basically it. Per our article on burnouts, tires have more traction at higher temperatures, and the friction of an intentional burnout is the fastest way to boost tire temperature. As for braking, eh... bearing in mind that there's a mechanical distinction in attempting to drive the wheels backwards and actually doing so, I think the answer is still "no". A dragster at speed can easily lock the wheels (and start slipping) by simply braking (thus the drag chute). Spinning the wheels backwards would have no further effect and could prove damaging to the vehicle. — Lomn 00:47, 9 December 2008 (UTC)

Rubber is weird stuff - and (as is fairly obvious) it gets sticky as it gets close to melting. So hot tyres are sticky - and sticky is good. So they heat the tyres up by spinning them (often with bleach poured on the track to help soften them still more). But for the actual launch at the start of the run - the idea is to NOT spin the tyres. In Formula 1 car racing, the pit crews keep replacement tyres in electrically heated jackets so that they are nice and sticky when they are put on the car at the next pit stop. SteveBaker (talk) 02:15, 9 December 2008 (UTC)

I wonder if releasing the clutch at super high revs might snap something. Formula cars do a lap to warm the tires and they would be the best gripping tires around but apparently if you spun one you would wreck its grip and unbalance the steering very easily. Rally cars were made at one time that could almost compete with formula cars but they were so dangerous and after a few races they would be burnt and seize up so they did away with them. ~ R.T.G 02:47, 9 December 2008 (UTC)

Hang on one second...I've often read that to get the best start off the line you basically have to dump your clutch at high enough revs that traction would just about be broken. This is to get the engine into the power band as quickly as possible. It is supposed to be a fine balance between trying not to spin your wheels endlessly (i.e. not moving) vs. not spinning at all and "bogging down" at low revs far below the power band of the engine. It is also given as a reason why four-wheel drive cars are so difficult to launch, the apportionment of torque to all four wheels makes it harder to break traction. This is just what I read on the net and in magazines, if anyone can explain it in finer detail I'd much appreciate it. Also, given the torque and power curves of a Honda S2000 (apparently a notriously difficult car to launch), what is the optimum RPM to dump the clutch at? Zunaid 16:51, 10 December 2008 (UTC)

Yes - you want the most torque possible at the wheels - consistent with them rolling (and therefore maintaining static friction) rather than slipping (and therefore getting dynamic friction). Since static friction is greater than dynamic friction for almost all materials - this is the best you can do for maximum accelleration. Dumping the clutch at this optimal RPM is certainly one way to reach that goal. Although...letting it out a little more gently to get the car rolling before ALL of the power is applied might be fractionally better for a turbo-charged car. With a turbo, you need enough engine RPM to generate enough exhaust to get the turbo spinning. If that RPM produces more torque than your tyres can stand without spinning - then you have a nasty problem. In that case - you might want to rev the engine to the higher RPM level to get that turbo going - then either briefly drop them as you dump the clutch (the turbo will take a while to spin back down again...) or you can let go of the clutch a little more gently to give the car time to get rolling before you let the full power of the engine get to the wheels. However, a car that demands that you do that could REALLY use a different gear ratio for 1st gear and/or some better tyres!

Differentials are the enemy of fast launches because they feed more power to the wheel that's moving the fastest. This is great for going around corners - but crappy when you are trying to launch quickly. If just one of your wheels starts to slip (maybe because the road is worn a bit more smooth on one side than on the other - or one tyre has a little less tread left) - the diff will apply more power to that wheel - robbing power from the wheel that's gripping and making the slipping one slip much worse. This is a problem in two wheel drive as well as four - but in a 4 wheel drive vehicle, you'll probably have a front diff, a rear diff and a center diff - all fighting hard to find the wheel that's LEAST able to make the car go fast and give it all the power! The fix for THAT is sophisticated "limited slip" differentials, lockable differentials and (best of all) fancy computer controlled differentials that are tied into traction control and yaw rate sensors. With those things, you can get a faster launch because power is given to the SLOWEST wheel instead of the FASTEST.

Sadly, on most cheap modern cars without fancy differentials, etc, there is "traction control" - which is supposed to prevent wheel slip on launch by artificially limiting your revs. This sounds like a good thing - but they are typically tuned to preven slip with not-perfect, not-sticky tyres and relatively poor road surfaces. Hence they limit the revs to something below what your nice new semi-slicks are capable of on clean, dry pavement - also, when they do drop the revs, it takes the engine time to get back up where you want it when the traction controller finally decides to give you back the right pedal. That means that to get the best launch speed you (ironically) have to turn off the very system the manufacturers put in place to help you do this!

As for a Honda S2000...the only thing I know about it is that the radio antenna is a nice short rubbery one that happens to fit perfectly onto the stock MINI Cooper'S antenna base and which produces considerably less drag and better FM reception than the one that came with my car! Thank you Honda! So there is at least ONE thing you make which I really like. SteveBaker (talk) 22:26, 10 December 2008 (UTC)

December 9

Coconut water as an IV

While perusing of our coconut article, I noticed that it said that coconut water can be used as an intravenous fluid. I'm a little curious about it. Would it be used to help dehydration, or what? bibliomaniac15 00:55, 9 December 2008 (UTC)

It would never be used IV: if you were on a island where you had nothing else to use, you wouldn't have IV tubing and an intravenous catheter; and any place that has IV tubing and an intravenous catheter would have a bag of saline, too. That said, coconut water is hyperosmolar/hypertonic: it is about 500 mOsmol/L in contrast with blood, which is about 290 mOsmol/L. So if infused, the effect would be to increase serum osmolality, resulting in retention of fluid. Since the statement in the article is unsupported by any citation, it needs to go. The one with the citation can stay :) - Nunh-huh 01:08, 9 December 2008 (UTC)

It can be, and has been, used as IV fluid, here is a link to an article discussing it. [27]. DuncanHill (talk) 01:12, 9 December 2008 (UTC)

And here's another [28]. DuncanHill (talk) 01:13, 9 December 2008 (UTC)

And a third [29]. DuncanHill (talk) 01:16, 9 December 2008 (UTC)

And another, [30]. DuncanHill (talk) 01:19, 9 December 2008 (UTC)

Still they keep coming [31]. DuncanHill (talk) 01:20, 9 December 2008 (UTC)

The fact that every time some clown uses it someone writes an article about it is actually pretty good evidence that it's not used except under extraordinary circumstances. - Nunh-huh 02:37, 9 December 2008 (UTC)

(outdent) I think it would be better to drink instead.--Lenticel ^(talk) 04:32, 9 December 2008 (UTC)

Extracting oxygen from ferrous oxide (FeO)

Could you? What resource would it drain? Does FeO actually contain O or is such a compound changed for ever? And why, if the moon has as much of this red stuff as mars... is it black and not red? ~ R.T.G 02:35, 9 December 2008 (UTC)

FeO (or iron(II) oxide) does indeed contain oxygen. It is actually a black solid, which would help explain the colour difference. DuncanHill (talk) 02:40, 9 December 2008 (UTC)

But FeO is rust right? And iron is definitely red unless you melt it... ? I thought it was iron that made Mars red and blood red, is ferrite not iron? Whats the difference? ~ R.T.G 02:51, 9 December 2008 (UTC)

FeO is only one form of rust. Iron(III) oxide is the common red rust that you were thinking of. 76.97.245.5 (talk) 03:33, 9 December 2008 (UTC)

The article on Mars surface color is a good place to start. You should read it and follow at least some of the links. Please ask if anything is still unclear. Now, regarding the extraction of oxygen on Mars: as far as I can recall, most projects involved extracting oxygen from CO₂ in the Martian atmosphere rather than from iron oxides on the Martian surface; see Mars Surveyor 2001 Lander for example. Extracting oxygen from iron oxides is possible, of course; but probably not as convenient or not as economic. You can do a little research here - this is a good topic for a project. BTW, it is possible to extract oxygen from Al₂O₃, too. The "by-products" (carbon, iron, or aluminum, respectively) are likely to be of considerable use, as well, so you should take that into account. --Dr Dima (talk) 04:02, 9 December 2008 (UTC)

Another article you should read is In-situ resource utilization. Enjoy, --Dr Dima (talk) 04:18, 9 December 2008 (UTC)

Its a lot easier, in general, to extract the metal from metal oxides (basically by transfering the "oxide" part to another substance, and leaving behind the metal) than it is to extract the "oxide" as oxygen. The reduction potential of the O₂ + 4e^1- --> 2O^2- half-reaction is quite high; to actually oxidize O^2- you'd need a rediculously strong oxidizing agent, or to do it electrolyticly you'd need a rediculously huge amount of current. Neither is a particularly economical means of producing oxygen. Free oxygen is such a hard thing to produce, it required a massively complex and convoluted chemical system (photosynthesis) to actually make it on Earth. If we are going to produce free oxygen in situ on another planet we colonize, then its going to come from a biological source rather than from an industrial/chemical one. --Jayron32.talk.contribs 04:27, 9 December 2008 (UTC)

It is true that energy demands of restoring a metal oxide to metal and oxygen are relatively high. However, electric energy is pretty much the only thing that will not be lacking on the early stages of Mars or Moon exploration. Bringing and deploying solar panels is very much easier than bringing and sustaining, say, water-tanks with algae. Solar panels have 20-30% efficiency vs 5-6% for photosynthesis, and the working temperature range for the solar panels is much broader. This is of crucial importance on both Moon and Mars, where temeprature changes between day and night are quite extreme. So, on earlier stages of Moon & Mars exploration, the direct electro-thermal process seems the way to go. On the more advanced stages of exploration / colonization / terraforming, the photosynthesis will produce al least some of the breathing oxygen and food for the humans. --Dr Dima (talk) 05:47, 9 December 2008 (UTC)

Agreed. Even though producing industrial amounts of free oxygen on a foreign, uninhabitable planet will probably never be an easy feat, using biological means would probably be even more difficult than using electrical means. Of the photosynthesising organisms we know today, I doubt even one species would survive on Mars for a fair amount of time, let alone being able to produce reasonable quantities of oxygen. Genetic engineering is always an option, of course, but I'm going to go on a limb and say it's probably easier and more economically viable to create a durable, properly catalysed electrochemical oxygen generator than it is to genetically engineer an extremely hardy and efficient photoautotroph. What's more is that using the biological way, a steady and reliable source of liquid water is pretty much a necessity for the organism to even do anything other than just sit there as a planetary ornament. --Link ^(t•c•m) 06:12, 9 December 2008 (UTC)

Water tanks and algae may be unworkable, but there may be a promising future in certain forms of archaebacteria and other extremophile life forms which may prove to be useful in this endeavour, especially with a little genetic engineering thrown in. We may find that engineering some little archeon with the ability to extract oxygen from oxides is easier even still than dragging around solar panels. The ability of a wide-range of enzymes and other biological process to turn otherwise impossible or improbable chemical processes into workable systems is mind boggling, and it may simple require putting together the right biological system to make it feasible. --Jayron32.talk.contribs 06:02, 9 December 2008 (UTC)

Back to the original question, is there a solvent that can dissolve FeO, and when electrolyzed produces oxygen and Iron metal (rather than hydrogen)? Graeme Bartlett (talk) 10:43, 9 December 2008 (UTC)

And with Graeme Bartletts question, what amount of solvents would current technology want for creating plant supporting atmosphere on the moon including ozone and other nessecary stuff? Would it all float away before it was useful? ~ R.T.G 13:08, 9 December 2008 (UTC)

Iron oxides dissolve in phosphoric acid, see this patent, for example. I never heard of electrolytic extraction of iron, though. Iron is usually produced from oxide in presence of carbon or carbon monoxide in a blast furnace, see Iron#Production of iron from iron ore. I'd venture guessing that the process to be employed on Mars - if iron oxides are to be the source of oxygen there ar all - would be some modification of an induction furnace or an electric arc furnace that would thermally dissociate iron oxides into iron and oxygen. At near-zero pressure the dissociation will go more readily, and there are no consumable chemicals to be brought from Earth - a definite advantage over a chemical process. Regarding your second question (the one about retaining an atmosphere) - Mars has been losing its atmosphere over a few billion years now, and there is still some left; so if humans generate a new Martian atmosphere it will not "float away" any time soon :) . Moon has lower gravity than Mars, though, and is closer to the Sun; and Earth with its magnetosphere does not help either. So I don't know how long a lunar atmosphere may persist once generated. --Dr Dima (talk) 17:46, 9 December 2008 (UTC)

Time Travel

One idea about time travel is that when you exceed the speed of light, everything, relative you you, is going backwards. This will have zero scientific meaning because, as the nice old man with the funny hair tells us, you can't make matter go faster than the speed of light. Even if you are going fast enough to see light stop in its tracks, wouldn't the matter that it's coming from continue to move? You can't measure speed without comparing it to a unit of time, 100 km/hr, 40 ft/second, 3 light-years/minute, so would you bump into the still moving objects because all you would see is the light from 2 min in the past or an hour in the past. If we were an x-ray, which i believe goes faster than the speed of light, would you see the light hitting and bouncing off matter? Say you continue to go the speed of light, which would hurt when, relative you you, air molecules run though you like bullets, could you go to the Sun, and just go through it without getting hurt? Infrared is lower than light so could you run though it like your hand over a candle? Weird stuff, but I think it's interesting. --70.181.81.205 (talk) 03:20, 9 December 2008 (UTC)

X-rays don't go "faster than the speed of light". -hydnjo talk 03:32, 9 December 2008 (UTC)

First see speed of light. Many of your assumptions about the speed of electromagnetic waves are simply wrong. -- kainaw™ 03:33, 9 December 2008 (UTC)

Sorry - all of your basic premises are incorrect - so your conclusions don't work.

• In your first sentence: This idea that something unknown and interesting happens when you exceed the speed of light completely neglects the indisputable fact that you can't do that. If you plug speeds greater than lightspeed into the equations relating to time, length and mass, they end up producing something like the square root of -1. The square root of -1 is not -1 (which is what you imply by suggesting that time would go backwards)...go ahead and type -1 into your pocket calculator and push the square root button. What you get is "Error". The square root of -1 is not a number that can express a real world property of mass, distance or time. This makes it impossible to ever go faster than ligh - not just some kind of interesting unknown thing...IMPOSSIBLE. That impossibility means that we can't use math or science to speculate on what would happened if you somehow magically did do that. The impossibility lies at the heart of the very mathematics we use here.
• In your second sentence: Einstein didn't just say you can't go faster than light - he actually said that you can't go as fast as light. So your idea of stopping light in it's tracks by moving alongside it at the same speed would be impossible even in a non-relativistic world. But the distinguishing thing (the utterly WEIRD thing) about light is that it's speed is always the same relative to you no matter how fast you're moving. So even if you are moving away from the Sun at 99.9999999% of the speed of light - if you try to measure the speed of that ray of sunshine, you'll find that it's STILL moving past you at the speed of light...not only does it not stop - it doesn't even slow down to the slightest degree! This is a deeply weird thing - but we've proven it to be true in numerous highly convincing experiments.
• In your third sentence: You claim that one cannot measure speed without reference to time. In truth - the universe seems to be entirely dominated by this lightspeed thing - and it's arguably the case that we should treat speed and distance as fundamental things and make time be derived from speed and distance. In such a situation, you would indeed measure your speed (as a fraction of lightspeed) without reference to time.

From this point on, your statements pile incorrectness on incorrectness to the point where it's hard to comment on them. But as others have pointed out - infrared light isn't slower than visible light - along with ultraviolet light, radio, microwaves - they all move at exactly the speed of light.

The one thing you that you say which is SO true...is that this stuff is weird but interesting. But you need a better grasp on the underlying science...once you do, things are much weirder than you can possibly imagine.

SteveBaker (talk) 04:09, 9 December 2008 (UTC)

Furthermore, by combining the second law of thermodynamics with the law of special relativity as described by SteveBaker above, you could contruct a completely coherant and consistant system of mechanics and motion with no mention of time at all. By the second law of thermodynamics, the entropy of the universe increases continuously. Thus, if we take the idea of "absolute time" to mean the 0 point is the Big Bang and the end-point of time to be the heat death of the universe; then we could just as well look at the Big Bang as a perfectly ordered universe (0% entropy) and the end of the universe as 100% entropy, and you could deal with temporal measurements merely by saying "event A happened when the universe was at entropy = 50%" and "event B happened when the universe was at entropy = 50.1%" you would have an unambiguous means to order event A and B without resorting to any measurements of time at all. Time is a mathematical convenience we use more easily express the ordering of events, but its not a real physical "quantity" the way that mass and distance and speed are. --Jayron32.talk.contribs 04:44, 9 December 2008 (UTC)

Well, I give the OP credit for some original thinking. Perhaps what he says is true in a parallel universe which has its own physics and natural laws. As Shakespeare wrote, "There are more things in heaven and earth than are dreamed of in your philosophy". Even in this universe we may be looking at things in a way that distorts reality, yet which is "proven" by mathematics and physics. Einstein himself showed that the Newtonian way of looking at reality was wrong, even though it was supported by mathematics and physics. Perhaps Einstein, in his turn, will be proven wrong. Conventional wisdom sometimes turns out to be conventional foolishness. Great ideas sometims start as heresy. —Preceding unsigned comment added by 98.17.46.132 (talk) 06:15, 9 December 2008 (UTC)

This demands a little correction. Einstein didn't prove Newton wrong precisely. He amended Newton's laws to account for the strange things that happen close to the speed of light. Newton's laws are stunningly accurate for all 'reasonable' speeds - and over the entire range of conditions for which they had ever previously been tested. Einstein didn't formulate his equations in order to explain some horrible experimental discrepancy that had been found - he was seeking an explanation for the absolute nature of the speed of light and deduced by pure reasoning that this correction to Newton's laws were therefore required. Remember it was only YEARS later when super-careful solar eclipse experiments had been performed specifically to test relativity that we finally had any kind of experimental evidence for the error in Newton's laws. Any amendment to Einsteins laws would have to apply in situations that are stranger still - which have yet somehow evaded our ability to test them. It would also require some kind of new discovery about the nature of the universe - something as stunningly weird as the absolute nature of the speed of light. But since we've tested these laws at all sorts of extremes - and they seem to work just fine - the number of places where a 'correction' to Einstein could possibly be hiding are rapidly vanishing. Certainly any new 'Hawkins law of refined relativity' (or whatever) would have to show Einsteins laws as working just fine over an enormous range of conditions - and any loopholes it provided for potential time-travellers would (by necessity) be impractical in the extreme! Personally - I doubt that'll ever happen. We fixed the bug - and now it's right. SteveBaker (talk) 13:46, 9 December 2008 (UTC)

Such an enquiring mind deserves its own expression in a science fiction novel. Who knows where that would take you? Think on, 70.181... Julia Rossi (talk) 07:09, 9 December 2008 (UTC)

The phrase "time travel" is a double negative. The word time is similar to the word speed and the word motion. It has no size or shape. It is a scale with no measure which looks odd but is spot on. You can traverse a centimeter but not an instant lol. When Einstein says that such speed would slow you down he is refering to the fact you would be squashed so tight nothing could move similar to ice or the Earths core. ~ R.T.G 10:54, 9 December 2008 (UTC)

I respectfully disagree with Steve's comment "We fixed the bug - and now it's right." Einstein's general relativity models gravity and space-time. However it does not model quantum theory. Einstein's theory is a more accurate refinement of Newton's model, but it does not represent every situation. Many scientists have worked to create a more accurate model, and I expect that the scientific community will eventually agree on a new theory that models gravity more accurately than general relativity. Axl ¤ [Talk] 21:46, 9 December 2008 (UTC)

It's perfectly possible that that could happen - but (and here is the crucial thing) whatever this new theory is, it has to agree with relativity rather precisely over the entire range of measurements we've done to date that confirm relativity. So the new theory would pretty much HAVE to prohibit faster-than-light travel. Sure, it could say that gravity doesn't warp space - or that some different set of math applies at the scale of quantum events...but the math has to produce the same results as Einstein over the range of data we have...which is pretty much the entire range of human experience - and higher speeds out to lightspeed and masses up to black holes and down to atoms. SteveBaker (talk) 02:32, 10 December 2008 (UTC)

Indeed, if you want to allow time travel or faster than light travel you need to introduce something which we haven't been able to observe yet. "Exotic matter" is the usual way people construct such theories. --Tango (talk) 14:03, 10 December 2008 (UTC)

Yes...although that's about as meaningful as speculating that the magic time-travelling pixie will come along and tell us how. It's not like there are these mysteriously faster-than-light things that we're trying to explain - there is zero reason to expect or even imagine that exotic matter will do anything interesting whatever in terms of relativity. Of course Newton would have said the same thing if asked about the speed of light (he didn't even know that light HAD a speed) - but the state of experimental science was pretty poor in Newton's day. Apples falling from trees are rather blunt instruments when it comes to probing the secrets of the cosmos...we have cool toys like a computer-controlled telescope the size of a schoolbus in orbit around our planet and something the size of a shoebox that sits on your desk, contains all of human knowledge and can do simple arithmetic about ten billion times faster than Newton could manage. But - as I said in the post that triggered Axl's reply - "Personally - I doubt that'll ever happen." - not "I know for 100% sure it'll never happen." SteveBaker (talk) 21:52, 10 December 2008 (UTC)

Sure, given how much observing we've done, "something we haven't observed yet" means something that probably doesn't exist. It's still interesting to think about, though (at least, it is for me, I'm a mathematician, we rarely let such minor details as whether things exist in reality get in the way of interesting maths). --Tango (talk) 21:59, 10 December 2008 (UTC)

Just to clarify: I do not think that a new widely accepted theory will allow time travel to be possible. Rather I think that there will be a new theory that would be a better model than general relativity. Comment to Tango: I think that the Large Hadron Collider (and later particle accelerators) will indeed show new phenomena that have not yet been observed. Axl ¤ [Talk] 22:19, 10 December 2008 (UTC)

GR does allow for time travel, it just requires you to fudge things a bit (eg. with exotic matter). Finding such matter (or a way to create it) is rather unlikely, but not impossible. The LHC will almost certain show us things we haven't seen yet (that's why it's being built), but they are likely to be things we already know ought to exist, it will just help us fine tune our theories. Observing exotic matter would be a much more significant event than observing the Higg's Boson, say (which would be a pretty big event). --Tango (talk) 22:26, 10 December 2008 (UTC)

Containing a super-volcano?

Could a very large Kevlar bag contain a super-volcano eruption and prevent the consequent mass extinction of mankind? Could any conceivable structure contain the dust and gases?Trevor Loughlin (talk) 07:33, 9 December 2008 (UTC)

Although I'm no expert on the subject, I know supervolcano eruptions are extremely energetic events. Containing the actual explosion would require unobtainium. As for the gas and dust, supervolcanoes eject over 1000km³ of tephra alone - not to mention the enormous volumes of gas that are released. I'd think your options are limited to damage minimisation, luck, and - unlikely but possibly - prevention of eruption. Containment is all but impossible as far as I can imagine. In any case, it would probably be more feasible to construct domes over all the major cities and harness geothermal and nuclear energy to stay alive. You'd also need to create artificial sunlight for greenhouses and the like. --Link ^(t•c•m) 08:17, 9 December 2008 (UTC)

Kevlar is seriously weakened by heat, so it stands no chance against lava or a volcanic bomb. Graeme Bartlett (talk) 10:31, 9 December 2008 (UTC)

Perhaps an Operation Plowshare sort of endeavour could relieve the pressure and prevent an explosive eruption. Or at least make an awesome Jerry Bruckheimer movie. --Sean 13:42, 9 December 2008 (UTC)

That might work, yes. On the other hand, it might just set it off early. Which would, kinda, suck. —Ilmari Karonen (talk) 18:15, 10 December 2008 (UTC)

Stellar Classification

I've read the article, found it a little confusing, but finally think I've got it. However, I wanted to check my understanding....

If a star is rated G1V in its wikibox, it means

• G - about the same size, temperature and brightness as the sun
• 1 - a bit hotter than the sun, though, since the sun is G2V
• V - about the same size as the sun.

Hmm. I mentioned 'size' twice. Maybe that's ok. Have I got this right? mike40033 (talk) 07:58, 9 December 2008 (UTC)

The classifications are explained in Stellar classification. G will be the Harvard spectral classification. I think the number (in this case 1) relates to the absolute magnitude and V is the Yerkes spectral classification, all of which are explained in the article I cited. Jdrewitt (talk) 15:43, 9 December 2008 (UTC)

Yes, that's the article I mentioned, that I read, and found confusing, and wanted to check my understanding. Have I got it right? mike40033 (talk) 00:35, 10 December 2008 (UTC)

Hello, well the Harvard classification indicates the temperature of the star's atmosphere, so strictly speaking G will stand for a star which has a comparable temperature to the sun. I think though since the sun is a main sequence star, you can infer the size and other properties from the temperature (This would not be the case for a red giant though). The number relates to the luminosity of the star, so 1 will stand for a star that is simply brighter than the sun, not necessarily hotter though. Then the Yerkes sectral classification relates the luminosity to the size of the star, so V will indeed represent a star about the same size as the sun. That's my interpretation of the article anyway. Jdrewitt (talk) 15:45, 10 December 2008 (UTC)

You are wrong about the arabic number. As the article says: "The spectral classes O through M are subdivided by Arabic numerals (0–9)." Hence, the spectral type of the star is G1 as opposed to the sun's G2. This means that the star is a little hotter and therefore has a spectrum closer to type F than the sun. This agrees with what the original poster stated. Indeed, the designation G1V has two parts (not three as one might suspect), in agreement with the Hertzsprung-Russell Diagram being a two-dimensional representation of properties. The spectral type is essentially given by temperature, the luminosity class (as indicated by the Roman numeral) by luminosity, although the boundaries between the luminosity classes are different for hot O type stars than for cool M type stars. The variation of size and mass can also be traced on the Hertzsprung-Russell diagram, but that is a little more complicated. --Wrongfilter (talk) 18:40, 10 December 2008 (UTC)

Thanks for pointing that out, it is not clear from the article by any means. Yeh, that makes sense now. Jdrewitt (talk) 10:46, 11 December 2008 (UTC)

Energy crisis

HI pple, I wanted to know whether its feasible to convert IR radiation to electricity..and use it ,say, for mobile charging ... If so, can you just tell me how.. —Preceding unsigned comment added by 59.163.146.11 (talk) 08:36, 9 December 2008 (UTC)

Well, for starters you can use IR radiation to heat things, so if you had enough of it you could use it to run a boiler to power a steam generator, but I'm almost certain there would be more efficient ways to do it. Gunrun (talk) 10:06, 9 December 2008 (UTC)

Possible? Definitely. Feasible? Apparently, not quite yet. --Link ^(t•c•m) 12:06, 9 December 2008 (UTC)

The boiler/steam generator concept has been implemented here, although it's not exactly a mobile solution, and the power it generates is currently still more expensive than conventional methods. Gandalf61 (talk) 13:27, 9 December 2008 (UTC)

There is research work going on in the field of infra-red 'solar panels' that would collect radiant heat and convert it to electricity. There are all sorts of interesting applications for them. However, if they exist at all - they are lab experiments - not something you can go out and buy. SteveBaker (talk) 13:30, 9 December 2008 (UTC)

Speed and mass

I remember reading somewhere that the faster an object goes the more mass it has. Is this right? Assuming it is does this mean that if you could accelerate a 9mm bullet to massive speeds (possibly using magnets?) you could demolish a house with it? Also would it be possible to accelerate an object to such speeds that its mass would be more than its atomic structure could withstand causing it to collapse in on itsself and form a black hole? Is this the reason nothing can move as fast as light? Gunrun (talk) 10:01, 9 December 2008 (UTC)

This is right, mass increases with speed. But no, a thing cannot be made to collapse into a black hole this way. See our article on mass and relativity. As for destroying a house with a single bullet, to get any really noticeable increase in mass, you would have to accelerate the 9 mm bullet to such a velocity that it would not hold together for an instant flying through the atmosphere. If the house were in a vacuum, however, then you could do a lot of damage with a single bullet, although it wouldn’t require a relativistic velocity, just plain very, very fast would do. This sort of thing is a problem for stuff in outer space in general, and especially for delicate instruments and space vehicles in orbit; we’ve managed to pile up quite a lot of junk up there in the past fifty years.--Rallette (talk) 10:49, 9 December 2008 (UTC)

There are a few things to note here:

1. The mass of the bullet is no different from the perspective of the bullet. It's only heavier for outside observers. But since the house is an outside observer - the bullet would indeed seem heavier.
2. The bullet's energy is kinetic energy - which is given by 1/2 M v² - so when you double the speed, you quadruple the amount of energy. So even without the relativistic effect, a bullet moving close to the speed of light would do an insane amount of damage.
3. However, the bullet won't collapse or break apart or anything - as far as it is concerned, it's just sitting there minding it's own business, being the same mass it always was. So providing it's moving through a good, hard, vacuum - it'll be just fine. Of course in air there would be severe problems - the heating due to friction would evaporate the bullet at just a few thousand miles per hour - LONG before it got remotely close to gaining mass noticably!
4. Note that the energy it would take to get something as big as a bullet moving that fast would be horrendous.
5. When we're talking about relativistic effects, there is an ENORMOUS difference between going at (say) 99.999% of the speed of light and going at 99.9999% - adding that extra '9' causes enormous differences in the mass we'd perceive the bullet to have attained - and spectacular increases in the damage it could cause.
6. You can work out the change in mass quite easily. Take the mass of the bullet and multiply it by $1/{\sqrt {1-v^{2}/c^{2}}}$ (where v is it's velocity and c is the velocity of light) - then, you can calculate the energy by multiplying that mass by v² and dividing by two.

So if we take a 6 gram 9mm/17 Browning round and push it up to 99.9999% of lightspeed, we have a mass of 6g / sqrt ( 1-(99.9999x99.9999)/(100x100) ) which is 4242g - about 4 kilograms. At 99.9999% of 299,792,458 meters per second (light speed) that bullet would release 1,900,000,000,000,000,000 joules - which is about 500 megatonnes of TNT. About ten times more than the biggest nuclear bomb ever detonated! The bullet wouldn't just destroy the house - or the city that the house was in - it would stand a good chance of destroying an entire european country. That's at 99.9999% of light speed. Make that 99.999999% (six nines after the decimal point) and the amount of energy goes up by another factor of ten and most of the planet would be at risk from your 9mm bullet!

Of course the amount of energy you'd need to get the bullet up to that speed in the first place would be...exactly the same...so to get your bullet up to 99.9999% of the speed of light - the propellant would have to be something with about the power of ten decent size hydrogen bombs.

SteveBaker (talk) 13:24, 9 December 2008 (UTC)

Actually, the city would probably be fine, in fact the house would probably survive. In order to do any damage that energy would have to be absorbed somehow, I would expect the bullet to just go straight through barely slowing down. --Tango (talk) 13:59, 9 December 2008 (UTC)

So it seems it would actually do less damage to humans as an ordinary 9mm bullet does. Yes, it will make a hole, but not turn and/or deform. --131.188.3.20 (talk) 14:42, 9 December 2008 (UTC)

I think it depends on how it impacts. If it came in at an angle and hit the ground - I don't see how it could keep going for long. You'd have a large crater and an enormous amount of material ejected into the atmosphere - nuclear winter...all of that stuff. If it came in horizontally - then maybe it's a different picture.

Let's consider your "pristine bullet" scenario. The tip of the bullet touches the wall at 99.9999% of c. The molecules of brick immediately in front of the tip do...what?

• Suppose the tip of the bullet is a shallow cone. The molecules of the brick either have to move out of the way laterally (which means accellerating to maybe a tenth the speed of light from a standing start - and then continuing at that speed through the brick above, below and to the sides of the bullet - with maybe 50 Megatonnes of energy between them.
• ...or the molecules have to accellerate to 99.9999% of the speed of light to stay in front of the bullet and fly out of the 'exit wound' on the far side. The force required to do either of those things has to be imparted by the bullet itself...so it has to apply a SPECTACULAR amount of force to the material of the brick...there is no way for it to do that without shedding a lot of energy (and in truth - evaporating into a cloud of relativistic particles.
• More likely is that the atoms of the bullet act like particles in the large hadron collider and convert the material they impact into who-knows-what exotic particles - which in turn shoot off at relativistic speeds...but we're not talking about a small cloud of a few dozen protons at near light speed - we're talking about an avagadro's number (or so) of protons doing that! The amount and energy of the resulting sub-atomic debris would vaporize a city...no problem.

So, no - I don't see how the bullet can go right through without releasing an enormous amount of energy. If you think it can - tell me in detail what happens to the cylinder of material immediately in front of the bullet - it can't just "go away" - and it can't gently move to one side because it doesn't have enough time. So it either accellerates to near lightspeed itself (causing secondary, tertiary, etc damage in the multi-megatonne range) or it's converted to other particles - which form a VAST amount of hard radiation with similar consequences as it's absorbed by surrounding materials.

Nope - I'm pretty sure we get our big satisfying explosion...not just a neatly drilled hole. SteveBaker (talk) 15:03, 9 December 2008 (UTC)

I'm not sure exactly what would happen, but let's consider the possibility of the cylinder of matter just being pushed forward ahead of the bullet and see what happens. That requires a spectacular amount of force, certainly, but we have that. Let's assume we have a perfectly inelastic collision, what we need to work out is the energy lost in that collision because that's the energy that's going to go into destroying things (the bullet and cylinder of brick will head of into space if they don't hit anything else first (we'll assume there is just one house and nothing but desert to the horizon), so that energy doesn't go anywhere interesting). We have 4 (relativistic) kg of bullet colliding with a thin cylinder of brick (we'll ignore the bonds between that cylinder and the rest of the house because I'm a mathematician and that's what we do - the energy to break them is probably trivial compared to the energy of the bullet anyway). Most of the house is air, so we'll ignore that, let's say we have two external walls and an internal wall to get through, we'll say that's 2 metres of brick (it's something of that order). According to Brick, the density of brick is about 2000kg/m³. The diameter for the bullet is 9mm, so that's a volume of 9mm*2m=0.018m³, so a mass of 36kg. Now we get to calculating the energy lost in a relativistic completely inelastic collision, and I'm not entirely sure I've done it right, but this is what I got: The bullet and brick are now moving at 0.11c (much slower than I expected, brick is heavier than I thought!), so you have an object of rest mass 36kg moving at 0.11c, that's an energy of, well, 1/2 mv² (0.11c isn't very relativistic), so 2*10¹⁶J, or 5 megatonnes of TNT, so we have 495 megatonnes left to destroy the world, so ok, that's pretty nasty. Out of interest, I did the same sums for your even faster bullet and got that the bullet and brick after the collision are now going at 0.74c, giving an energy of (using relativistic formulae this time) 1.6*10¹⁸ or about half a gigatonne of TNT, leaving 4.5 gigatonnes left. So, the moral of the story is not to shoot houses with relativistic bullets (and that Steve has a better intuition about relativistic physics than me)! --Tango (talk) 16:49, 9 December 2008 (UTC)

I can't calculate the volume of a cylinder... hang on while I revise all that... --Tango (talk) 17:32, 9 December 2008 (UTC)

Ok, it's 1kg of brick (I thought 36kg was a bit much!), so the final speed is 0.97c (far closer to what I was expecting), which corresponds to an energy of 2.8*10¹⁷J, or 67 Mt, leaving 433 Mt left. So, still a massive bang. For the faster case we have a final speed of 0.9997c, and an energy of 3.6*10¹⁸J or 0.86 Gt, leaving 4.14 Gt, so again, still a massive bang. Oh well, the final conclusion is the same, but not by quite as much as I my first calculations showed. --Tango (talk) 17:44, 9 December 2008 (UTC)

Since the proportion of energy left is decreasing as speed increases, I've done it again for 99.9999999999% c to see what happens. This gives a final speed of 0.99999997c and an energy of 3.6*10²⁰J, or 86 Gt, from an initial energy of 500 Gt, leaving 414 Gt left, exactly the same proportion as last time, perhaps this is an asymptotic thing? 0.86 is about ${\frac {\sqrt {3}}{2}}$, could that be the limit? --Tango (talk) 17:52, 9 December 2008 (UTC)

No, that would be stupid, while the brick weighs a nice round number the bullet doesn't, so we wouldn't expect a nice answer. It's probably coincidence. --Tango (talk) 17:54, 9 December 2008 (UTC)

The problem with the bullet pushing a neat cylinder of brick out of the wall is that the particles of brick have to accellerate from zero to 99.9999% of the speed of light (minus a little bit) in the time it takes the bullet to travel maybe a couple of millimeters at most. At lightspeed, a nanosecond is a foot - 300mm - so the brick molecules would have to accellerate to a significant fraction of lightspeed in just a few picoseconds - it's a very, very VERY short period of time. Classically F=ma - and for the relatively small mass of the brick, and an accelleration of zero to lightspeed in a few picoseconds...that's a PHENOMENAL amount of force that the bullet has to apply to the brick. Worse still - the brick cylinder is being accellerated to relativistic speeds - so the energy it needs is pretty much the same as the amount of energy it took to get the bullet up to that speed in the first place. So the energy of the bullet would have to be divided roughly equally between brick and bullet post-collision. So the brick accellerates from zero to maybe half the speed of light in maybe 3 picoseconds - and the bullet slows down by about the same amount just as quickly. Just think of the g-forces on the bullet! We're talking g forces comparable to a neutron star. How can a lump of lead or brick suffer that much force without being utterly annihilated? It's just inconceivable that this can end in anything much short of two thousand quadrillion joules(!) of spectacularly high energy gamma rays...which will cook everything out to the horizon and to a depth of a few kilometers into the ground. A few thousand square miles of everything would simply vanish - the resulting debris would likely be thrown up into the upper atmosphere and would probably shut out the sun for a few years - maybe plantlife dies - then animal life dies - then it's game over for humanity. SteveBaker (talk) 02:23, 10 December 2008 (UTC)

It doesn't matter if the bullet and brick are completely annihilated, as long as the remnants continue to travel on at relativistic speeds and take a large chunk of the energy isn't space with them. However, my calculations show that it wouldn't be a large enough chunk and we would still be looking at an explosion big enough to wipe out all life on Earth. (Although, I've realised I still can't calculate the volume of a cylinder, I used the diameter instead of the radius, so it's actually 0.25kg of brick. That doesn't seem to make a significant difference to the end result though.) --Tango (talk) 13:58, 10 December 2008 (UTC)

You might be interested in the Oh my god particle, a relativistically-fast micro-bullet From Beyond! --Sean 13:46, 9 December 2008 (UTC)

This whole bullet scenario is pretty silly. You're applying a physical model which is designed for elementary-particles to macroscopic objects. There are so many problems - like, bullets would not remain in solid-form when their individual particles attain kinetic energy many orders of magnitude above their intermolecular binding energies. Once again, when you pose a ridiculous physical scenario, there's no good scientific-model to apply, so throwing equations at it will not conclusively answer anything. Maybe we should move this question to the Science Speculation Desk For Crackpot Theories Applying Quantum Mechanics and Special Relativity to Unlikely Scenarios. I don't think it does a service to the "uninitiated" readers who are unfamiliar with advanced physics when we use inapplicable theories on non-physical situations. It's bad physics, even if the math is flawless. Nimur (talk) 16:17, 10 December 2008 (UTC)

But the bullet's kinetic energy is zero in the only reference frame that tells you anything about what state of matter the bullet is in. --Tango (talk) 16:56, 10 December 2008 (UTC)

It's hard to say where to begin in shooting down Nimur's post! Firstly, the 'physical model' is Einsteins special relativity theory - which most certainly does apply to macroscopic objects. The bullet is PERFECTLY able to retain it's solid form (so long as we're in a vacuum) precisely BECAUSE relativity says that the laws of physics are the same for all inertial frames of reference - so the bullet is able to consider itself to be stationary - and if it's stationary in a vacuum then it's certainly not going to fall apart due to some mysterious binding energy issue. The same is true for the building...and in fact, this is just as much a question of what happens when a building that's moving at 99.9999% of lightspeed hits a completely stationary bullet...because that's the EXACT same question. Bullets don't usually spontaneously disintegrate just before something hits them! Until bullet and building actually meet, neither of them is in the slightest bit inconvenienced. If you don't know this (and given what you just said - it's hard to see how you do) then you should sit back and read some of the things posted here rather than complaining about them because there is a strong possibility that you'll actually learn something. The equations I was throwing at the problem are all perfectly acceptable for this kind of situation. It's hardly "advanced physics" - the equations have been around for 80-some years. Lorentz, F=ma, E=1/2 mv² are all taught in any good high school - and those are the only equations I've used. This is a perfectly legitimate way to discuss the question as asked. If you're going to start whining about the nature of the questions that are asked here - then you are on a slippery slope. SteveBaker (talk) 21:37, 10 December 2008 (UTC)

You were taught special relativity in high school? I didn't get taught about Lorentz factors until Uni. (I'd read about them in books before then, of course, but that's just because I'm a geek.) --Tango (talk) 21:56, 10 December 2008 (UTC)

Sequence line-ups

I am starting a project involving the use of computer programs (BLAST, ClustelW, AlignX) to line-up the genes of different clades of the same enzyme in two species of flatworm. I don't know where to begin, however, as I have no experience in this area. Can anyone guide me where to go to find information about how such a project may be undertaken or a link to a paper or two that have used the same method before? 143.117.157.60 (talk) 11:35, 9 December 2008 (UTC)

This paper covers a lot of relevant tools: [32]. Another resource is CDD. TreeFam seems relevant: [33]. Some of these I found Googling "alignment orthologs flatworm", etc. BioEdit is a nice, free (Windows) sequence editor that has plenty of built-in tools. HTH --Scray (talk) 11:54, 9 December 2008 (UTC)

You might also want to consider using Psi-BLAST, and it has a nice tutorial. --Scray (talk) 11:57, 9 December 2008 (UTC)

I also find ClustalX much friendlier than ClustalW. --Scray (talk) 11:59, 9 December 2008 (UTC)

There are several pretty decent Wikipedia references that you might want to read through. If you already have your sequences in hand, you can assemble them into FASTA format and run them through Clustal (use version ClustalX as suggested above, since it's a graphical user interface) to generate your multiple sequence alignment. ClustalX can also export the alignment file as in a format that can be used to generate a phylogenetic tree or dendrogram (which is what I assume you are trying to do). As mentioned above, Bioedit is very useful for modifying/annotating your alignment file from ClustalX into a form that can be published.

If you don't already have sequences in hand, then you need to use BLAST ([34]) to find all of the sequences that are significantly similar to each other in the sequence database. To do this, take your known enzyme sequence and blast against a particular flatworm genome. There are a few variations that you need to be aware of:

1) BLASTN - nucleotide blast, searches a nucleotide database using a nucleotide sequence query

2) BLASTP - protein blast, searches a protein database using a protein sequence query

3) TBLASTN - translated blast, searches a translated nucleotide database using a protein sequence query

Any given enzyme will probably have fairly high identity at the protein level between closely related species, but the nucleotide conservation will be much lower. For that reason, I would recommend starting from a protein sequence and searching your different species using BLASTP to pull out the homologous enzymes. Note that this will only identify annotated protein sequences (or in some cases predicted protein sequences). You can extend your search using TBLASTN against the whole genomic sequences to find unannoted nucleotide sequences that could encode the enzyme you're interested in. If you find a piece of genomic sequence that seems to contain a protein-coding gene, you can run it through a gene prediction program. It can get a little complicated sifting through genome data, but it's a good exercise to see if you can find intron/exon junctions, etc. Have fun! Medical geneticist (talk) 20:14, 9 December 2008 (UTC)

Why does light refract upward at cold temps?

Was out snow shoeing earlier, have always wondered why at colder temperatures (<-25C) light refracts upward way into the sky? The only info I could find about this was instead for forming ice plates and cooler temps, when its real cold the ice crystals for a more vertical shape? Does air density have to do with this as well? —Preceding unsigned comment added by Oilsandsfj (talk • contribs) 12:50, 9 December 2008 (UTC)

http://en.wikipedia.org/wiki/Mirage#Superior_mirage This should help you I think. Gunrun (talk) 14:01, 9 December 2008 (UTC)

Cheese and intestinal blockage.

Is there anything in cheese that makes it cause constipation? I've noticed with myself and friends, whenever we eat a meal with quantities of cheese, our bowels get blocked up. I've eaten tons of dairy and lots of fatty foods in meals without any similar problems. But what is there about cheese that seems to act like intestinal concrete? --69.149.213.144 (talk) 14:31, 9 December 2008 (UTC)

The bigger issue is that when you are eating cheese, you are NOT getting as much dietary fiber as when you eat other foods. Try the experiment and see if eating some high-fiber foods alongside cheese doesn't improve the situation for you... --Jayron32.talk.contribs 16:51, 9 December 2008 (UTC)

Or get your fiber in your cheese, with caraway cheese: [35]. (Actually, this is low on fiber, so you'll still need other sources.) StuRat (talk) 05:01, 11 December 2008 (UTC)

What, no article ? Now I'm really cheesed off ! StuRat (talk) 05:03, 11 December 2008 (UTC)

Road salt

Will road salt kill grass? Grsz¹¹ 16:49, 9 December 2008 (UTC)

It can yes, if too much of it gets on grass it can burn it, the same way over fertilizing it can. -Djsasso (talk) 16:51, 9 December 2008 (UTC)

Oh well, I rent. Thanks, Grsz¹¹ 17:13, 9 December 2008 (UTC)

See Salting the earth... --Dr Dima (talk) 17:15, 9 December 2008 (UTC)

Instead of sodium chloride, potassium chloride is sometimes used to melt road ice. Would potassium chloride be less harmful to grass and to the metal parts of cars? —Preceding unsigned comment added by 98.17.46.132 (talk) 14:37, 10 December 2008 (UTC)

A very good question. Googling for KCl NaCl plant toxicity returns plenty of fascinating stuff, including a great 1908 paper on wheat root growth in solutions of several metal chlorides at various concentrations. Skimming conclusions from a few sources, the somewhat surprising answer is: KCl is not necessarily less toxic than NaCl for grasses. So please don't salt your garden! That is, unless Menelaus is calling ;) . --Dr Dima (talk) 18:47, 10 December 2008 (UTC)

How do you use microwaves to find out if there's foil inside butter tubs?

I've just started a new project with school and Dale Farm that we have to detect the foil inside butter tubs without taking the lid off. Microwaves work at finding out if there's metal there or not but I can't work out how to make a circuit that will tell me without looking at every current coming out. Anyone know of any useful websites? —Preceding unsigned comment added by C ocean (talk • contribs) 17:39, 9 December 2008 (UTC)

Puting metal in a microwave is contraindicated (don't do it!) for several good reasons. First, the potential for fire or other hazards is quite great, and secondly the presence of metal could damage the magnetron (the working bit) of the microwave as well. It would actually be quite easy to, using stuff lying around the house or availible at the local SuperMegaHardware Store, create a rudimentary Metal detector. this google search turns up literally hundreds of sites which show how you can do this. Good luck! --Jayron32.talk.contribs 18:01, 9 December 2008 (UTC)

It sounds like what you want is a radar setup. I agree, though, a metal detector is much more practical for the typical school project (unless this is a particularly unusual sort of school). 198.29.191.149 (talk) 19:08, 9 December 2008 (UTC)

Butter+foil+microwave oven=fire, don't do this combination. Graeme Bartlett (talk) 20:21, 9 December 2008 (UTC)

Although the flaming result would certainly reveal the foil. Fire extinguisher recommended. --—— Gadget850 (Ed) ^talk - 20:47, 9 December 2008 (UTC)

I don't see the word "oven" anywhere in the original question; C ocean, can you clarify what you are trying to do? Beyond that, I have seen microwave ovens with metal racks, so clearly the whole "never use metal in a microwave!!!111" meme is overwrought. --LarryMac | Talk 20:47, 9 December 2008 (UTC)

You can use metal in a microwave oven— such as a rack —under certain circumstances. You get some electric current induced into any metal, but pointed edges cause arcing and heating. A spoon would not arc, but a fork would. I suspect the the edge of the foil cover would arc, and melted butter is flammable. This would occur in a standard microwave oven or if it was just focused microwaves such as from radar. --—— Gadget850 (Ed) ^talk - 21:00, 9 December 2008 (UTC)

I've seen microwaves specifically designed to be safe with metal, but only one piece of metal and it needs to be pretty flat (eg, a piece of foil covering a bowl would be fine). If you have two pieces, of one piece that bends, then you can get arcs from one bit of metal to another, but if you only have one bit there is nowhere for the arc to go. I think the way they do it is to not have any metal around the edge of the oven so nothing can spark from a bit of metal inside to the edge. --Tango (talk) 22:10, 9 December 2008 (UTC)

Wait, wait, wait...are we over-thinking this? Are they talking about some foil contaminant buried deep inside the butter (seems unlikely) - or are they simply asking whether the foil that is SUPPOSED to be sealing the butter under the lid has somehow not been put there or perhaps was subsequently removed? If THAT is the question our OP has to answer then perhaps it's as simple as rotating the lid and seeing how stiff it is? Or tapping on the top of the lid and listening to the sound it makes (or having your computer listen to it)? Or weighing it? ...or...lots of REALLY simple tests! SteveBaker (talk) 01:51, 10 December 2008 (UTC)

The OP indicated some aspect of the project involved circuitry, so I assume that an electronic device is supposed to be built which will detect the presence of metal. Rudimentary metal detectors, involving simple inductor circuits, can easily be built using household materials, so I still think that's the easiest way to go. --Jayron32.talk.contribs 03:32, 10 December 2008 (UTC)

Or do a biopsy stick in a needle and take out a sample, too bad about the little hole though. Graeme Bartlett (talk) 03:46, 10 December 2008 (UTC)

This sounds VERY much like a common electronics class lab (sometimes used in physics as well). The point of the lab is to build two variable oscillator coils. Put one in the middle of the other and get them on the same frequency. Connect a tiny speaker between them. Everything should be fine until something interferes with the magnetic waves (not microwaves - magnetic waves). Then, the frequencies get messed up and get out of sync - causing an audible signal over the speaker (the beep that metal detectors make). I've seen it printed up many times for many different schools. The test is always "detect (some metal object) inside (some opaque container)". -- kainaw™ 03:51, 10 December 2008 (UTC)

cosmic string

If a cosmic string passed through the Earth, what would happen? Assuming they exist. --140.247.10.18 (talk) 19:10, 9 December 2008 (UTC)

For a long cosmic string (kilometres or bigger), I expect the Earth would be destroyed by tidal forces before it got too close, so it wouldn't be able to pass through the Earth. For a very short one (smaller than an atom) it would be much like a micro-blackhole and would pass straight through with little effect. I'm not sure about ones inbetween. --Tango (talk) 19:48, 9 December 2008 (UTC)

How to destroy the Earth: Whipped by a cosmic string — DanielLC 01:52, 10 December 2008 (UTC)

Theoretically we can calculate many results, but one thing should be noted the concept of cosmic string is still in a hypothetical stage. Otolemur crassicaudatus (talk) 10:35, 10 December 2008 (UTC)

Native Americans and Atlantis

How plausible is the information in the link here? http://www.redicecreations.com/specialreports/2006/05may/atlantisDNA.html --Emyn ned (talk) 19:20, 9 December 2008 (UTC)

"Genetic researchers determined that 96% of Native Americans fell into one of the four A-D haplogroups and while these mtDNA types were also found in Asia they are not present in Europe or Africa. This too indicates that Asia was the ancestral region of most Native American tribes. Then in 1997 another lineage was discovered, which geneticists dubbed X. This discovery ignited a storm of controversy that has not died down to this day. The X haplogroup needs careful,thoughtful, and deep historical analysis because this group may well hold one of the most important keys to unlocking the secrets of our collective past. ......

Moreover, the vast majority of tribes contained no X members. In fact, it was not found in any native tribes in Central or South America. Again, what did these patterns mean? Independent researchers associated with the Edgar Cayce Association (A.R.E.) quickly pointed out that the data supported some of the material found in the Atlantis readings that the 'sleeping prophet' had given in the 1930s. Cayce noted that some Atlantis refugees had immigrated to the northeastern region of the United States and later formed the Iroquois nation. It was in those tribes that the highest concentration of the X haplogroup was found." --Emyn ned (talk) 19:25, 9 December 2008 (UTC)

No comment on the genetics, I'm just amused by the concept of a mass migration from the Mediterranean to New England. I wonder how many Atlantians survived their first winter. APL (talk) 20:17, 9 December 2008 (UTC)

There are certain persistant cultural traditions and artifacts among Native American peoples which raise some questions as to how "isolated" they were. The Quetzalcoatl/Kukulkan myth in Central America has some depictions of the "feathered serpent god" as a bearded, pale-skinned man; neither traits were common among native American peoples, leading to speculation that the myth had European connections. Additionally, certain artistic traditions of the Olmec people show subjects with decidedly African (and not really Central American) features, suggesting contact there. Beyond that, there is the Vinland settlements circa 1000 AD, speculation over Chinese exploration of the N. American west coast, and other evidence of possible pre-Columbian contact between the hemispheres. While the celebrated, the well funded "expeditions" had the benefit of being ventures supported and historically recorded by the power elite, and so show up in the historical record. There may well have been fisherman plying the coasts of North America and other, less celebrated contacts, between the hemispheres that disappeared from the formal historical record. There are many, simpler, Occam's razor-compliant explanations for genetic anomalies among Native American populations than "Mega continent disappears without a trace, and leaves no evidence except genes among the Native Americans". --Jayron32.talk.contribs 22:18, 9 December 2008 (UTC)

Is anyone willing to comment on how this ties in with the reported descent of Native Americans from the lost tribes of Israel? CBHA (talk) 22:37, 9 December 2008 (UTC)

Sure. There is no such descent, at least as the Mormons or Atlantismaniacs tell it. See Human mitochondrial DNA haplogroup for a map of the travels of the peoples bearing Haplogroup X. - Nunh-huh 00:21, 10 December 2008 (UTC)

Does lemon juice damage your teeth?

All over the internet it is suggested that it does; but one can't always believe the internet. Nothing about the matter on Wikipedia, as far as I can see. I've recently taken to drinking green tea with lemon, which is very refreshing; and I suppose I'm going through about the juice of one small lemon a day. But if I'm damaging my tooth enamel, I'd better stop. 92.8.198.137 (talk) 23:16, 9 December 2008 (UTC)

Lemon juice is somewhat acidic, and the acid could damage your teeth, but the final pH of the liquid is what matters. Even highly acidic drinks like orange juice or pop don't really make much difference, the enamel damage comes from sugar that feeds bacteria that stay on the teeth, not the acid that just passes right by into your already acidic stomach. These bacteria produce acid that remains in contact with the enamel for a long time and can cause real damage. You might theoretically be damaging your teeth, but chewing on a piece of bread is probably worse. SDY (talk) 23:42, 9 December 2008 (UTC)

Here is a good reference. Otolemur crassicaudatus (talk) 00:05, 10 December 2008 (UTC)

Can't get access to the full article. I assume they were soaking the teeth in the liquid? Again, the final pH of "tea with lemon" is probably in the 4-5ish range at best unless it's "do you want some coffee with your sugar?" amounts of lemon juice. SDY (talk) 00:10, 10 December 2008 (UTC)

This is another interesting article (although orange rather than lemon). Axl ¤ [Talk] 22:51, 10 December 2008 (UTC)

December 10

Tea and diabetics

I was in my local tea market and they had a sign warning of the dangers of drinking tea if you are a diabetic. It warned that it can increase blood sugars. I've never heard of such a thing. Obviously, if you take your tea with sugar, that's a problem. But unsweetened plain tea? Is there any truth to this? --69.149.213.144 (talk) 04:15, 10 December 2008 (UTC)

According to this article, which appears to quote a reliable source, rat studies suggest that tea may be of benefit to people with diabetes. [36]. DuncanHill (talk) 04:32, 10 December 2008 (UTC)

Here is a reference according to which "Tea catechins, especially (-)-epigallocatechin gallate (EGCG), appear to have antiobesity and antidiabetic effects". Otolemur crassicaudatus (talk) 11:22, 10 December 2008 (UTC)

Tea does not worsen blood sugar. Axl ¤ [Talk] 18:29, 10 December 2008 (UTC)

Unless, of course, you add sugar to your tea... – ClockworkSoul 19:06, 10 December 2008 (UTC)

Caffeine is a diuretic. This means that it makes you pee. Depending on the type of tea, it can make you pee, which reduces your water proportion (and I mean the percent of water you are composed of). This, inturn, will increase your blood (glucose) sugar level, because the water that is excreted in the urine will be immediately from the blood. (urinary system for more). Then nephrons of the kidneys take the toxins from the blood and in urinary tubes (it's been a while since i last did biology) funnels it to the bladder for excretory storage. Mind you, water is the solvent in the medium of these toxins. So tea may increase blood glucose levels in this way.96.53.149.117 (talk) 07:58, 11 December 2008 (UTC)

If it were a tea market, I'm guessing there would be a lot of fancy teas some of which may contain sugars natural or otherwise. This may be directed at those. Even more so if you're a Brit in which case you may be thinking of several cupsof tea within a few short hours Nil Einne (talk)

Fleeting bad memories

Sometimes out of the blue I suddenly remember a bad memory and makes me feel bad. My knee-jerk reaction would bedoing an intellectual na! nanana! I can't hear you! by focusing on something else (tapping my fingers for example) until it goes away. What do you call that resurgence of memory and my suppression of it.--Lenticel ^(talk) 04:45, 10 December 2008 (UTC)

There's a wiki article Flashback (psychological phenomenon) which is too stubby to be of great help, but it's a start. Suppression of it, repression, is a defense mechanism. Julia Rossi (talk) 05:04, 10 December 2008 (UTC)

Take also a look at Rumination_(mental). --Mr.K. (talk) 09:51, 10 December 2008 (UTC)

The finger tapping block is mechanical, not the same thing as a subconscious repression. Try Thought suppression for the deliberate conscious one. Julia Rossi (talk) 22:34, 10 December 2008 (UTC)

I find swearing at the people who caused the bad memories to be beneficial. Of course, only do this out loud when you're alone, or you'll have to tell everyone you have Tourette's Syndrome. StuRat (talk) 04:48, 11 December 2008 (UTC)

Jets flying over populated areas

Do fighter aircrafts have to fly over populated areas? Civil aircrafts probably have to, but why do military jets do it?--Mr.K. (talk) 09:37, 10 December 2008 (UTC)

If a military aircraft flies over populated area, that does not mean it will use its weapons system. It becomes quite tough and the route becomes quite complex if it avoids civilian areas. If there is short air route available by flying over a civilian area, the fighter may take that route. Otolemur crassicaudatus (talk) 10:41, 10 December 2008 (UTC)

I would assume the question is motivated by the F/A-18 that crashed into a house in San Diego recently, and not by concerns over weapons systems. In this case the fighter was on approach to Miramar which is surrounded on three sides by populated areas. Dragons flight (talk) 11:07, 10 December 2008 (UTC)

It is not uncommon for military bases to be surrounded by populated areas. It is not reasonable to ask the fighter jets so somehow create a wormhole through space and teleport from outside the populated area to the military base without flying over all the homes that were built around the base - usually long after the base was built. -- kainaw™ 13:38, 10 December 2008 (UTC)

It's very unusual for fighter jets to land on houses, so it doesn't make sense to give the issue much attention in their routing. You'll probably save more lives by having the houses near the base, which will reduce the number of person-miles the base workers will drive on their daily commute. --Sean 13:42, 10 December 2008 (UTC)

Why should military aircraft be held to any standard other than civilian ones, given the latter are larger, not designed as ruggedly vs things that could happen in the air (747 doing a barrel roll and getting hit during a dog-fight?), and are owned by companies deep in bankruptcy vs the cash cow that some claim US military spending is. DMacks (talk) 14:02, 10 December 2008 (UTC)

"Why should military aircraft be held to any standard other than civilian ones..."

There are dozens of reasons:

• Different aircraft design, including size, speed, type of fuel, maneuvering capability
• Different flight capabilities
• Different engines (louder, noise-complaints over populated areas)
• Different training methods and selection criteria for pilots
• Different aircraft manufacturing (materials, hazardous components)
• Different safety regulations regarding pilot state (hours of sleep, for example)
• Different ground support crew (maintenance, air traffic control, personnel supervision)
• Psychological impact due to the presence of an ejection seat on a pilot in an emergency over a populated area
• Potential to carry weapons systems
• Overall different philosophy regarding the role and operation of military vs. civilian aircraft

The result is that there is a different standard, implemented in the form of air space - there is restricted military-only airspace; there is restricted civil-only airspace, and shared airspace. The F-18 that crashed this week had already declared an engine malfunction while over the ocean, and was being routed to Miramar (instead of the aircraft carrier where it was based), because it was probably thought safer to fly overland than over water [37] - "Several experienced pilots said that if there's a nearby landing field ashore, an inexperienced pilot wouldn't attempt a dangerous, engine-out landing on the pitching deck of an aircraft carrier." Pending the full investigation, it is not clear why the pilot ditched the aircraft, but assuming his judgement was sound, a serious equipment failure may have rendered it uncontrollable. Alternatively, the pilot may have misjudged or panicked. Nimur (talk) 16:36, 10 December 2008 (UTC)

Thanks for the knowledgeable reply! I might add in reply to the question "Why should military aircraft be held to any standard other than civilian ones...", that they are already held to much lower standards. To be exact, 750 feet lower. At least that was the case in Germany, where US jets (mostly Phantoms) crashed on civilian houses on a regular basis when I lived there - they were allowed to fly at 250 feet at supersonic speed, according to de:Tiefflieger (for which there seems to be no translation. Can it be that they only did that in Germany?) I can tell you - it all fun and games when they fly slowly over you on Fourth of July, but it's brute force when they blast over your head every other day at random times. — Sebastian 18:07, 10 December 2008 (UTC)

Tieflieger trained not only in Germany, but they were a particular problem there for a number of reasons. First, Germany is simply small and full. There are few areas without significant population, particularly not for an aircraft at Mach 1 or above. Secondly, Germany was seen as a likely battlefield in the Cold War. Hence, for realistic training, Germany was preferred. And thirdly, as a result of the WW2 capitulation, the allies got fairly far-reaching military cooperation agreements that allowed them to use German airspace for training purposes without alienating their own voters. --Stephan Schulz (talk) 19:28, 10 December 2008 (UTC)

Can you define "regular basis"? Was it daily? Who's house is going get destroyed today? Was it weekly? Was it monthly? Was it yearly? Did it happen 3 times over 20 years? It is difficult to relate this singularity in the U.S. with Germany without something better than "regular basis". -- kainaw™ 18:13, 10 December 2008 (UTC)

Ah, found it: de:Starfighter-Affäre. The plane was the Lockheed F-104G, a.k.a. "Starfighter". There were hundreds of crashes. According to the German article, alone in 1965, there were 27 accidents with 17 casualties. And as I remember, this dragged on for years. — Sebastian 18:24, 10 December 2008 (UTC)

Looking at our own article Lockheed F-104, which says "flying at high speed and low level over hilly terrain, a great many accidents were attributed to CFIT or Controlled Flight Into Terrain ...", I learned a wonderful doublespeak way to say "crash"! — Sebastian 19:33, 10 December 2008 (UTC)

"Controlled flight into terrain" isn't doublespeak, it's a term of art describing a specific type of crash. Other types of crash include runway overruns, mid-air collisions, and structural failure. --Carnildo (talk) 22:34, 10 December 2008 (UTC)

But of course! It's a "controlled flight into building", as in "Controlled demolition hypothesis for the collapse of the World Trade Center". ;-) — Sebastian 23:18, 10 December 2008 (UTC)

I see, I wasn't aware of that term. But it's still strange, and it doesn't seem to be common in aviation, at least not here at Wikipedia. Even our article Aviation accidents and incidents only mentions Controlled Impact Demonstration, which uses the term in the way most people would: "Controlled" meaning "keeping things under control". — Sebastian 00:16, 11 December 2008 (UTC)

I used to work in flight simulation - it's a common enough aviation term with a very precise meaning. It means that the plane didn't hit the mountain because it was damaged or because the pilot had blacked out...the aircraft was perfectly flyable - and the pilot was fully in command of the controls - but the plane smacked into a mountain anyway. Hence it means things like flying into a mountain because of reduced visibility - or some kind of nighttime navigational error - or because the altimeter was mis-calibrated...something like that. SteveBaker (talk) 06:21, 11 December 2008 (UTC)

And I should point out that I, despite having never heard the term before nor any experience in the airline industry was able to guess more or less what it meant Nil Einne (talk) 12:20, 11 December 2008 (UTC)

Reducing fat

There are a myriad of products on the market that promise to reduce the fat in your body. In a series of them, the effect is from outside the body (heat waves, cream, vibrations, small electro-shocks). Excluding surgery, is there any possibility to reduce fat through this way or fat can only be reduced from inside?--Mr.K. (talk) 09:47, 10 December 2008 (UTC)

Dieting may help. Physical exercise is the best option to reduce fat. It depends on the amount of body fat a person has. There are anti-obesity drugs also available. In extreme cases where the person is too overweighted, surgery is generally required. Otolemur crassicaudatus (talk) 10:47, 10 December 2008 (UTC)

The question is actually about ways of reducing fat with an external procedure (not diet, exercise, ...) and excluding surgery. Is it possible?Mr.K. (talk) 11:08, 10 December 2008 (UTC)

Well exercise is arguably an "external procedure", and likely to be effective. In principle, electrical muscle stimulators should be capable of improving muscle strength and tone in a way that is similar to (but probably inferior to) that of exercise. That would probably have an indirect effect on fat. I have also seen some studies (in rats) supporting the notion that vibration reduces fat deposition, though that is not the same as removing existing fat deposits. The best thing for reducing fat though is almost certainly dieting. Dragons flight (talk) 11:17, 10 December 2008 (UTC)

In the case of exercise, our body burns the fat to obtain energy, definitely a natural process of our body. --83.40.248.171 (talk) 11:39, 10 December 2008 (UTC)

Clockwork Toy (Homemade)

I'd like to make a gear-based toy, but I don't know a good source for cheap gears and such. Any suggestions? Preferably plastic. Black Carrot (talk) 10:56, 10 December 2008 (UTC)

McMaster-Carr has all sorts of those kinds of bits and bobs. --Sean 13:48, 10 December 2008 (UTC)

Lego Technic? SteveBaker (talk) 21:19, 10 December 2008 (UTC)

LPG

At what temp. does LPG turn to vapor for use on a furnace in a camper?```` —Preceding unsigned comment added by Raytrudell (talk • contribs) 13:34, 10 December 2008 (UTC)

Assuming good faith that it is not a homework question, the answer to your question is -42°C. Otolemur crassicaudatus (talk) 13:50, 10 December 2008 (UTC)

This temperature is appropriate for propane, however in case of LPG it may vary from -44 ºC to 0 ºC. Otolemur crassicaudatus (talk) 14:01, 10 December 2008 (UTC)

Doesn't pressure have something to do with it? —Preceding unsigned comment added by 98.17.46.132 (talk) 14:03, 10 December 2008 (UTC)

Yes, it is in "normal" atmospheric pressure. Otolemur crassicaudatus (talk) 14:20, 10 December 2008 (UTC)

LPG in a cylinder is at a higher pressure than atmospheric. When an appliance connected to the cylinder is turned on, the pressure in the cylinder is reduced somewhat and the liquid boils, thereby releasing gas. It will always boil, regardless of the temperature of the LPG liquid, unless the ambient temperature makes the temperature of the liquid LPG in the cylinder extremely low. LPG is mainly butane; in winter months, LPG suppliers mix some of the more expensive propane with it to ensure it will boil. —Preceding unsigned comment added by 98.17.46.132 (talk) 15:00, 10 December 2008 (UTC)

Yes it will boil in any temperature above 0 ºC which we see in our every day life, but it needs the minimum temperature -44 ºC in "normal" atmospheric pressure to boil. Otolemur crassicaudatus (talk) 15:16, 10 December 2008 (UTC)

"LPG" and "vapor pressure" in Wikepedia have information on this.

Test your microwave with a mobile phone?

On a recent episode of the Gadget Show it was claimed that you can test the shielding on your microwave oven by checking whether a mobile phone will receive a call when inside the oven [38]. I have tried this on two microwaves so far, and in both cases the phone could receive the calls. I have also read elsewhere that the shielding should not stop mobile phone calls because the frequency differs too much from those used by the microwave. Can anybody clarify this please? Larry Mystery (talk) 15:21, 10 December 2008 (UTC)

The question you are asking is, roughly restated, "does the microwave have a shield?" It should be more properly restated, to be very precise, as "What is the non-linear anisotropic attenuation-vs-frequency characteristic of the microwave casing, and what frequencies of attenuation overlap those frequencies used by the cellular phone?" First of all, let's clarify a few details:

• Microwaves and cell phones commonly do operate at the same or similar frequency band (for example, 2.45 GHz). But, maybe your microwave and cell phone operate at different frequencies... it depends on whether your phone uses GSM, where you bought your microwave, etc. You can check this with the marshmallow test, or if you're smart, just read the label on the back of the microwave oven.
• Microwaves commonly include a few features, such as a wave guide or horn to guide the microwave energy in a specific direction (towards the food)
• After the microwave energy is "in the oven", it bounces around, off the walls, maybe even setting up resonant waves. So, any "shielding" should really be surrounding the entire oven, with strongest protection at the places of strongest electromagnetic fields (typically, directly opposite the "horn" where the waves come in.
• Microwave ovens probably use a "crappy" but generally single-frequency tonal magnetron to create the electromagnetic waves. So, the shielding is quite probably a "notch filter" (isolating out that single frequency and preventing it from passing).
• By the second law of thermodynamics, any (passive) shielding should be bidirectional - that is, if the energy can't get out, then energy can't get in, either.
• Shielding is also not measured as "all or nothing" - it's measured as an attenuation. That means that the shield lowers the intensity of the radiation, but does not make the signal disappear completely. Now comes the non-linear part. The case in consideration compares two very very very different orders of magnitude - nearly one kilowatt of oven radiation, blasting from eight inches away, compared to a few milliwatts transmitted by the phone and maybe nanowatts (picowatts even!) received from the tower. (Depending on "details," your phone may need bi-directional communication to initiate the reception of a call; or it may just need to receive a single incoming message from the tower). So it may not be safe to say that the shielding materials attenuate by a fixed amount over this entire range of power levels. It's possible that very-low intensity signals, like those from the phone, are not attenuated much at all; while high-power signals are brought down to safe intensities (and no further)
• Cell phones use very complicated modulation to make sure that the data can be deciphered even when the signal is very very weak. This is what advertisers often mean when they say "fewer dropped calls" (though they might also be talking about density of towers). Specifically, some of the QAM spread-spectrum coding schemes are particularly insensitive to single-frequency interferers. So if the So even if the microwave shielding is "pretty good" at notching out (stopping) that single frequency that the oven operates at, the cell phone data may be fairly undeterred.
• And the anisotropic part makes a huge difference! The cell-phone probably has a crummy antenna, which may mean it has a weird angular reception pattern. And, the microwave oven shielding is probably not uniform either (presumably concentrated on blocking regions of highest radiation while cooking!) So, if you rotate the phone, you may get dramatically different reception patterns. And this is totally assuming that there is no resonant coupling between the 2.4-GHz resonant chamber of the oven, and the 2.4-GHz dipole antenna inside the phone. Who knows what may happen to the reception pattern if that effect is non-negligible! In summary, the orientation of the phone with respect to the oven, and the orientation of the oven with respect to the nearest tower, will dramatically change the results. (see Radiation pattern for more graphical explanation).

So, it can actually be fairly complicated to say whether a given microwave will "shield" a given cell-phone from a call. Irrespective of the result of that test, it is not really a good way to determine whether the oven casing effectively blocks out the microwave energy used during cooking. Nimur (talk) 17:00, 10 December 2008 (UTC)

paper mache external fuel tank

I attended a lecture at the Naval War College by Dr. Paul Kennedy of Yale University where he stated that during the second World War, the British developed paper mache external fuel tanks for the P-51 Mustang. He showed a picture of two Brits unloading one such tank from a stack. At that time, the Americans were using aluminum external tanks and the Germans were picking them up off the ground after they were dropped in Belgium and then they (the Germans) would reuse the metal. The paper mache tanks, however, when hitting the ground would become unusable. I have not been able to find any reference to paper mache tanks on the internet or in published materials I have on planes of the second World War. East5426 (talk) 15:58, 10 December 2008 (UTC)

Mildly related: the Tom Clancy movie Clear and Present Danger featured a paper bomb/missile that was used to blow up a drug kingpin's house such that it could not be traced to the US source by the shell fragments. Or something like that. --Sean 16:52, 10 December 2008 (UTC)

I've looked around on google a bit, and mostly all I see are modeling sites selling tanks for use on static models and discussion board posts, none of which meet WP:RS. Definitely happened, but you may need a bricks and mortar and, ironically, paper library to find references. SDY (talk) 16:59, 10 December 2008 (UTC)

It's possible the professor was making a vague allusion towards early research in composite materials, which now make up an entire class of aerospace engineering materials research because of their light weights. I don't know that any such materials were in use in research labs, let alone combat, in World War II. Nimur (talk) 17:12, 10 December 2008 (UTC)

In early 1943, the Eighth Air Force was looking for ways to escort B-17's to Germany and back. The YB-40's were no match for the German fighters, and once the B-17's had dropped their bomb load, the YB-40's were too heavy to keep up with the lightened bombers. Ira C. Eaker began looking at adding drop tanks to P-47 fighters. The U.S. was then using 200 gallon paper tanks for ferry flights, but these were mostly useless for combat, they added a great deal of drag to the airframe, tended to leak if filled with fuel for more than a few hours, and could not be used at altitudes greater than 23,000 feet.

Eighth Air Force fighter command, with the help of British engineers, designed a 108 gallon metal tank suitable for combat operations that was tested in May of '43, but a steel shortage prevented production. The Brits would begin supplying a paper 108 gallon tank which they had developed for their own use in September of '43. The British 108 gallon tanks extended the P-47's combat range radius from 190 to 375 miles.

The U.S. began manufacturing a 200 gallon paper tank (which was only half-filled on the P-47) that became available 28 July (260 mile rangeradius), and an 85 gallon (photo) (referred to as 75 gallon tanks, but actually held 85) metal tank (340 miles). On 27 September '43 the eighth flew it's first escorted mission to a target inside Germany using a mixture of the 85 gallon metal tanks, as well as the British 108 gallon paper and metal tanks. Levine, A. J. (1992). The Strategic Bombing of Germany, 1940-1945.] pp. 90-1. OCLC 25131830

Still looking for paper tanks for the P-51.—eric 21:17, 10 December 2008 (UTC)

This is a longshot but the search might work better in some search environments using "papier mache" instead of "paper mache". CBHA (talk) 21:28, 10 December 2008 (UTC)

[39] [40] w/ photos of the 108 gal. paper tanks.—eric 21:55, 10 December 2008 (UTC)

Diamonds Part 2

A few days ago, I posted a question about Diamonds. For the original question and discussion above, see this link: Wikipedia:Reference desk/Science#Diamonds. A follow-up thought (and question) came to mind after reading the input from my original question. So, we now have "real" (natural) diamonds that one can purchase for, say, $1000. And we have the "same exact thing" (synthetic) that one can purchase for, say, $100. Much of the discussion centered on purchasing the cheaper synthetic diamond, because it is exactly the same thing as the more expensive natural diamond. The only real difference is purely psychological and is a product of emotion and of clever marketing. But, what about looking at this issue from another perspective? Let's say that I indeed want to buy the "real thing" (natural diamond). As a consumer ... when I purchase what I think is the $1000 "real thing" … how do I know that I am not, in fact, being swindled and getting the $100 synthetic one in its place? Thank you. (Joseph A. Spadaro (talk) 18:23, 10 December 2008 (UTC))

Via grading and certification services such as the Gemological Institute of America. — Lomn 18:40, 10 December 2008 (UTC)

A related issue is how one is able to know that a natural diamond is not a blood diamond. Although there are industry procedures in place to ensure that synthetic diamonds or blood diamonds are not misrepresented, as an end consumer, you ultimately have to rely on your trust in the vendor. Past that, the article section Diamond#Synthetics, simulants, and enhancements notes that "Today, trained gemologists can generally also distinguish between natural diamonds and synthetic diamonds." It also mentions several machines/methods to distinguish them (DiamondSure & DiamondView). Additionally, most synthetic diamond producers are upfront about the nature of their wares. Many even visibly (under a loupe) mark their gem-quality diamonds with logos or other such items which shows who produced them. I believe DeBeers has even started marking natural diamonds in a similar fashion, to show that they are "real" diamonds. Natural diamonds from Canada are routinely marked, e.g. with the "CanadaMark" service. High carat diamonds may be marked with a serial number, and registered with institutions like the Gemological Institute of America, which record their provenance. (Unfortunately, I can't seem to find an article about diamond marking.) -- 128.104.112.113 (talk) 19:15, 10 December 2008 (UTC)

Could crooks put counterfeit certification markings on diamonds? Even if a serial number on a natural diamond is registered, how would a person know which diamond is the natural one? A record of all sales and purchases of a natural diamond would have to be kept as well. —Preceding unsigned comment added by 98.17.46.132 (talk) 22:09, 10 December 2008 (UTC)

Artificial gem diamonds aren't identical to natural gem diamonds. If made without further intervention, a lab diamond is (scientifically) superior - there are no almost impurities and a much lower incidence of flaws. To compete in the gem market, the lab people have to add impurities (mostly metals) to allow them to control the colour and clarity of their product; in particular they produce lab gem diamonds in colours that occur infrequently in nature. For now (because they don't feel the need not to, and to avoid stirring up a war with DeBeers) they do so in a fashion that simulates a natural diamond to casual (and fairly close) inspection, but isn't intended to deliberately appear entirely natural. DeBeers has a number of technologies to distinguish any of these from the "real" thing (as 128.104.112.113 notes above, they sell equipment to dealers for this purpose). Some other synthetic gems (such as emeralds) are made with deliberate un-natural additions that assist detection. If the lab people really wanted to, I imagine they'd be able to "improve" the growing process to produce the adulterations and defects that the gemologists and their machines look for. I guess (were that to happen) a technological tit-for-tat would ensue for a while (much like CAPTCHA) but eventually the lab ones would be sufficiently imperfect as to be entirely indistinguishable. Diamond marking is (in part) a recognition of this inevitability (the blood diamond thing is also a factor). But it's not much of a solution - numbers can always be cloned, and many gem diamonds turn over in the market so infrequently (decades) that the cloning won't be detected. Even if it is, if ten people all have identical diamonds with the same number, whose is the real one? And if a major player (say Russia or China) decided to mass-produce indistinguishable lab gem diamonds and tag them as coming from a mine that they really only bother to run when the inspector comes, they can produce fully certified artificials. And a major production of such diamonds could lower the price of all diamonds (except the truly exceptional ones with a provenance) as to make chasing after suspected "fakes" uneconomic. The only thing stopping this all from happening is that it's not in the interest of the artificial makers to ruin the market they've just joined - they want to be competitive, but they don't want to end up making diamond so cheap that there's only a decent profit when you make it by the ton. So they have a gun to DeBeers head (once they don't want to use) and DeBeers have one back - they can dump their (reportedly huge) reserves onto the market which zaps the artificial guys profit margins and makes their venture capital dry up (it's a Phyrric victory, as it also ruins DeBeers market for years to come). This stalemate won't last forever, I think. All those new members of the Chinese and Indian middle classes have a taste for things that the western middle classes already enjoy. Sooner or later someone will decide he can make his fortune selling a nice 1 carat artificial to 100 million people, and the game's up. 87.114.128.88 (talk) 23:08, 10 December 2008 (UTC)

...which, incidentally, is (in the long term) an unalloyed good for the Human Race. Diamond, like gold, is amazing stuff, and it's a shame it's been wasted in gaudy frivolity. The same technological improvements that will lower the artificials' prices so that everyone in India can have one will (hopefully) improve the diamond makers' abilities to the point where they can make affordable diamond an engineering material. Diamonds as bearings and bushings and joints, diamond coatings to metal components, diamond elements in aircraft wings and car engines, maybe even diamond beams holding up a three-mile skyscraper. 87.114.128.88 (talk) 23:19, 10 December 2008 (UTC)

I agree. Debeers has had people paying insane prices for shiny baubles for too long now. It's time that diamonds were made available to everyone at reasonable prices. An interesting side-effect will be that diamonds, once no longer rare or expensive, will no longer be valued in jewelry. Other gems will take over that position, like pearls, at least until they can be exactly replicated in the lab. StuRat (talk) 04:21, 11 December 2008 (UTC)

It's possible for diamond to remain popular in jewellery even after you can pick up a one carat rock for a buck and a half. They make excellent stones for decorative purposes because they don't get damaged (diamond being spectacularly hard) - and they have this HUGE refractive index which is what makes them sparkle so alluringly. Perhaps the trend will merely be for jewellery sales to trend towards much bigger and more perfect stones while the price remains pretty much stable. It's hard to predict when human emotion is so tied up in what happens. SteveBaker (talk) 06:14, 11 December 2008 (UTC)

I fear that super-cheap diamonds would suffer a "bling" problem (with gaudy people festooned in them like some kind of insane pearly king) that diamonds would become gauche; I guess it's much the same as how wearing purple was once such an indicator of success and thus prestige, but with the advent of synthetic dyes anyone can wear purple so it has no cachet whatever anymore. 87.114.128.88 (talk) 13:30, 11 December 2008 (UTC)

Travis Pastrana

I was reading about Travis Pastrana. During an athletic competition, he sustained an injury in which his spine was separated from his pelvis. While I was continuing to read about him, I was assuming that this injury would have left him paralyzed. Seemingly, it did not. Why / how could that be? Thanks. (Joseph A. Spadaro (talk) 19:43, 10 December 2008 (UTC))

By not damaging his spinal cord, or otherwise causing significant nerve damage. This is one reason why the common advice is not to move an accident victim: if the spine is damaged, moving the victim can indeed lead to spinal cord injuries and, potentially, to paralysis. 198.29.191.149 (talk) 20:11, 10 December 2008 (UTC)

In an adult human, the spinal cord only extends about 2/3 of the way down the back. Below that point, there are several nerves that travel the remaining distance through the vertebral column and exit at various lumbar and sacral segments. Without knowing much about the injury you describe, I would assume that a separation between L5 and S1, while painful and probably dangerous, could plausibly fail to sever any of the sacral nerves that exit from the sacral region. He may well have suffered some stretch-induced injury (similar to a brachial plexus injury) that might include temporary numbness or weakness of the lower extremities. -Medical geneticist (talk) 20:16, 10 December 2008 (UTC)

Washing up

When washing up, does one get better results if one puts the Fairy liquid in the bowl before filling it with hot water, or after? And if so, why? DuncanHill (talk) 22:36, 10 December 2008 (UTC)

I doubt you'd get much (if any) difference by placing the washing up liquid in the bowl before or after. There might be a slight difference as the splashing of water on the liquid when placed before the water may increase the 'bubbliness'. That said, I imagine the best results in those terms would come if you placed the liquid in during the fill-up process. —Cyclonenim (talk · contribs · email) 23:28, 10 December 2008 (UTC)

Agree with Cyclonenim, definitely during. And for the foreigners here, it's Fairy liquid  :) hydnjo talk 02:53, 11 December 2008 (UTC)

Towards the end is better, because the earlier you add it, the more foam you get. While a bit of foam is good as a thermal insulation, it doesn't drain as well when you dry your dishes. — Sebastian 08:58, 11 December 2008 (UTC)

I always rinse the dishes with hot water, so lather is not a problem. DuncanHill (talk) 13:08, 11 December 2008 (UTC)

Lonely inventor builds working cyborg girlfriend in own home - malarkey or effective way?

Just read a news story where this is claimed to be the case.

Any thoughts on the matter? I'm immediately suspicious of his claims, as the videos presented in the article only show a working head and working hand. There is nothing showing the entire femmebot up and about and performing the tasks he says that it can perform (which, to my mind would be the vids that would really wow everyone). The still photos kinda look like he's just posed a rubberised mannequin in various places.

Also, the story appears in The Sun - which, as any fellow Brit will know, doesn't exactly have the best reputation as a newspaper for fact-checking.

So, what do you think? BS or not BS? --Kurt Shaped Box (talk) 23:38, 10 December 2008 (UTC)

Well, leaving aside The Sun's unassailable history of quality reportage, the official website of the project is at [41]. DuncanHill (talk) 23:42, 10 December 2008 (UTC)

Dunno about you - but programming the gynoid to violate the First Law of Robotics (she can apparently slap humans) seems like a really bad idea to me. --Kurt Shaped Box (talk) 01:07, 11 December 2008 (UTC)

It's a pretty impressive project for a one-man hobby effort - but it's FAR behind the state of the art. He's got together a large collection of miscellaneous bits of software and wedged them into the computer that drives the robot - but look at the movements of mouth and eyes in the video - they are laughably pathetic. A lot of the claims on the web site are of the form "In theory she could be programmed to..." - meaning he hasn't done these things and in all likelyhood is unable to do so. Move along - nothing to see here. SteveBaker (talk) 06:08, 11 December 2008 (UTC)

December 11

Yerba mate

Does yerba mate have any caffeine? If not why does it seem to have that effect? —Preceding unsigned comment added by 63.165.5.103 (talk) 00:34, 11 December 2008 (UTC)

The article you linked seems to have quite a detailed answer: Mate contains xanthines, which are alkaloids in the same family as caffeine, theophylline, and theobromine, well-known stimulants also found in coffee and chocolate. Mate also contains elements such as potassium, magnesium and manganese. Caffeine content varies between 0.3% and 1.7% of dry weight (compare this to 2.5–4.5% for tea leaves, and 1.5% for ground coffee). Mate products are sometimes marketed as "caffeine-free" alternatives to coffee and tea, and said to have fewer negative effects. This is often based on a claim that the primary active xanthine in mate is "mateine", erroneously said to be a stereoisomer of caffeine. However, it is not chemically possible for caffeine to have a stereoisomer, and "mateine" is an official synonym of caffeine in the chemical databases. 76.97.245.5 (talk) 01:10, 11 December 2008 (UTC)

plants

is there a way to keep a plant or seed alive fo a couple months without letting it grow? —Preceding unsigned comment added by 76.14.124.175 (talk) 00:49, 11 December 2008 (UTC)

Seeds can remain viable for a very long time indeed. Our article seed hibernation mentions seeds which have grown into plants after ten thousand years or so of hibernation. Algebraist 00:53, 11 December 2008 (UTC)

so you have to freeze the seeds? —Preceding unsigned comment added by 76.14.124.175 (talk) 01:21, 11 December 2008 (UTC)

I think that's not necessary. As long as you store it in a clean, cool, dry and dark place then the seeds should be indefinitely dormant. Basically you don't want to trigger germination due to moisture and sunlight and avoid spoilage from fungi and bacteria.--Lenticel ^(talk) 01:58, 11 December 2008 (UTC)

Yea, just refrigerate them in a dark container. Freezing could actually damage seeds from tropical plants that aren't adapted to such conditions. StuRat (talk) 04:08, 11 December 2008 (UTC)

Laser cooling

What's the application of laser cooling? Is it only able to cool atom? Could it cool molecule? And do they provide data about the coolest temperature reach for each atom? Thanks for your responses. roscoe_x (talk) 01:19, 11 December 2008 (UTC)

• Laser cooling might be of help to you. As for the coolest an atom can be, have a look at Absolute zero. - Mgm|^(talk) 09:52, 11 December 2008 (UTC)

See Laser_cooling#Minimum_temperature for details on the minimum temperature that can be achieved by laser cooling. To cool large molecules is more difficult, but a method called Sympathetic cooling achieves this too. EverGreg (talk) 10:29, 11 December 2008 (UTC)

Crystallisation esp. seen in ice... what is the magic of the hexagon?

The chemistry of crytallisation is the usual topic but what about the physics? Especially seen in Snowflakes and on the poles of Saturn but also seen to create exotic type forces when freezing water (such as expanding its own mass without external reactions and creating linear faces). The stuff on snowflakes and Saturns poles... although non-solids convecting will form hexagonals naturally filling out the available space... what is going on with the hexagonals in snowflakes or on Saturns pole where there is ample space to be some random shape? Although the hexagonal pole of Saturn is peculiar, not even crop circles have a patch on snowflakes. Is this hexagonal a manifestation of the genetics of non-living items? How does a crystal create a smooth face over an area and how does a crystal without boundaries in size create a hexagon in an open space? If somebody travels through space and time, will they use a hexagonal stargate? Are some liquids actually a sub-viral life bound in a hexagonal skin? ~ R.T.G 02:00, 11 December 2008 (UTC)

well, ice is typically hexagonal due to the Hydrogen bonds in water. its not exactly random.--Lenticel ^(talk) 02:32, 11 December 2008 (UTC)

I don't think anyone has adequately explained why snow flakes have so many shapes. The water vapor, it is said, condenses on a dust particle and the shape initially established grows. I think there is a theory that impurities in the water vapor establish the original shape. Some information might be obtained if a snowflake can be grown on a solid particle of known size and shape and extremely pure water vapor is supplied for the growth material. "Snowflake" and "Wilson Bentley" in Wikipedia provide interesting information, photos, and leads to other information about snowflakes. —Preceding unsigned comment added by 98.17.46.132 (talk) 02:53, 11 December 2008 (UTC)

Yeah, the pictures I was talking about are on Wilson Bentley who learned a method to photograph snowflakes in detail. Although possibly related to hydrogen bonding, a ball is similarly related to a ball park. Look at the pictures close up, they are nothing unusual but they are amazing every time, symmetry across distances based on a hexagon much larger than a hydrogen bonded molecule and also the pole of Saturn is probably bigger than the Earth itself. Hey, its not random at all!! ~ R.T.G 03:05, 11 December 2008 (UTC)

Included among the Bentley snow-crystal photos shown at http://www.bentley.sciencebuff.org/collection.asp?page=1

are some snowflakes of unusual shape. At first glance, a few of them do not even seem to be hexagonal - but they are actually irregular hexagons. —Preceding unsigned comment added by 98.17.46.132 (talk) 03:14, 11 December 2008 (UTC)

Inhabitable planets larger than the Earth?

Assuming mankind either explores other solar systems or perfects terraforming within this system, how much larger than Earth could a planet be before it caused serious problems for the human colonists? And could a planet with a core of low density materials such as lithium or aluminum be much larger than Earth but have normal gravity? Since Ringworlds and Dyson spheres are unphysical even with advanced nano-materials, would a pressurized sphere of hydrogen gas be capable of making a terraformed "Earth" with normal gravity, but on a much larger scale? —Preceding unsigned comment added by Trevor Loughlin (talk • contribs) 02:57, 11 December 2008 (UTC) Trevor Loughlin (talk) 02:59, 11 December 2008 (UTC)

One possibility for living on a planet with higher gravity is to live some distance under the surface, where the gravity would be significantly less. Unlike the Earth, though, such a planet must not have a molten core. StuRat (talk) 04:02, 11 December 2008 (UTC)s

I guess it's possible - but the technology for digging that deep doesn't remotely exist - and remember that you'd have to start all of that constuction - as well as build things like solar power plants on the surface of the planet - so much of the work involved would still be high-g.

As for alternative construction approaches - RingWorlds and Dyson spheres are indeed problematic for all sorts of reasons. You didn't mention the other fictional star-encompassing idea from the book "The Smoke Ring" it's sequel "The Integral Trees" (an awsome piece of imaginative world-making - and actually rather more feasible than "RingWorld"). But why bother - if you have the engineering skills and the raw materials - then just make spinning cylindrical mini-worlds - each a few kilometers in diameter and a few tens of kilometers in length (think "Rendezvous with Rama")...you could make them in stable solar orbits - in vast quantities (if needed) with none of the theoretical issues you'd have with the more exotic designs. Your pressurized sphere of hydrogen would be an interesting concept - but I don't see why you'd choose hydrogen versus a big pile of asteroids. SteveBaker (talk) 06:00, 11 December 2008 (UTC)

Considering it is a hypothesis, why couldn't it be entertained?96.53.149.117 (talk) 06:06, 11 December 2008 (UTC)

Erection

I know that heterosexual rapists, some of them, get erections when rape is the form of sexual intercourse. Is this also found in homosexual rapists?96.53.149.117 (talk) 05:32, 11 December 2008 (UTC)

I'm almost certain they do, rapists rape for the same reasons whether they go for the same gender or not. —Cyclonenim (talk · contribs · email) 08:03, 11 December 2008 (UTC)

I'm sure I'm missing something here, but isn't it impossible to commit rape (as defined by the OP) without an erection? Zain Ebrahim (talk) 11:02, 11 December 2008 (UTC)

I think he meant that rapists can only get an erection when sex is non-consensual. Belisarius (talk) 11:51, 11 December 2008 (UTC)

1 calorie

Why is 1 calorie defined as the heat required to raise the temperature of 1g of pure water through 1 degree celsius from " "14.5 degree & not from any other temperature"? —Preceding unsigned comment added by 118.95.40.140 (talk) 07:30, 11 December 2008 (UTC)

Good question. The temperature needs to be indicated since the specific heat of water changes with temperature. Consequently, as our article calorie explains, there are different definitions for different temperatures, and the 15 °C calorie (cal15) is just one of them. But why anybody would want to use just that definition, I'm not sure. To me, the 20 °C definition makes more sense, since that is room temperature. Maybe it's because 15 °C is closer to the average outside temperature in moderate climates. — Sebastian 08:47, 11 December 2008 (UTC)

Spinal injury

I'm looking for information on spinal injuries, especially fuzing of vertebrae and conditions requiring this, etc. Got a friend who may need most of their back fuzed, and I'm looking for information on what it involves, what the impact might be long term, and (very much secondarily) what sorts of issues might medically lead to such a requirement. Mostly an article on spinal fuzing, or whatever the correct medical term is.

I can't find a relevant article. Do we have any, and if so what are the title/s? (If we don't, what are the correct medical terms and any suggested resources, for a wider search?)

Thanks.

FT2 ^{(Talk | email)} 13:05, 11 December 2008 (UTC)

Well, I was going to recommend the article tilted Vertebral fusion, but that is basically a dicdef and nothing else. Hm. Have you tried websites like WebMD or something like that? Google? --Jayron32.talk.contribs 13:20, 11 December 2008 (UTC)