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May 7

degree of benefit

Where might I obtain the data to determine if the installation of Internet capable water meters might reduce fuel consumption by various utility suppliers? 71.100.14.205 (talk) 01:08, 7 May 2008 (UTC)

You could try asking the suppliers. Otherwise, try googling for some study into them. --Tango (talk) 12:41, 7 May 2008 (UTC)

Infinity of space

Today my Physics teacher was discussing how the universe can go on forever or it can be like a snowglobe, and no one can know what's outside the globe. I'm extremely intrigued by the unknown factors in this and was wondering if someone could point me in the right direction to go read more into this (typing in "past what we think is the universe" didn't get me anywhere haha). Thank you! Evaunit♥666♥ 02:09, 7 May 2008 (UTC)

We've got an article on Shape of the universe, but it gets a bit technical. There's also the issue of the observable universe versus the "whole" universe. The problem about talking about things "outside the universe" or "before the beginning of the universe" is that all of our physics is based on observations inside the universe, so it's hard to say that they apply to things outside that. Confusing Manifestation(Say hi!) 03:22, 7 May 2008 (UTC)

I think your teacher is talking about the Ultimate fate of the universe and whether the universe will continue to expand such that the energy density approaches zero (infinite universe i.e. Heat death of the universe), or will it contract such that the energy density approaches infinity (reaches a maximum "snow globe" i.e. Big Crunch). Information cannot travel faster than light so the snowglobe is the size of light traveling since the big bang and there should always be a boundary, even in the collapsing model. --DHeyward (talk) 06:04, 7 May 2008 (UTC)

Data in the past decade seem to be pointing to a hyperbolic, infinite universe that does not contain enough mass to stop expansion. Imagine Reason (talk) 20:00, 7 May 2008 (UTC)

One weird idea that alot of people seem to have trouble with is that although the universe may have a contained shape, that doesn't mean that anything lies outside the shape. When physicicsts talk about "the universe," they are attempting to describe everything that exists. If the place where everything exists is in some dimension spherical (which it's probably not, by the way), then nothing lies outside of that sphere because the sphere just is everything that exists. Contemporary scientific theory has raised the possibilty of multiple universes, so maybe this should be qualified as "everything that exists for us" or as Confusing Manifestation pointed out "the observable universe." --Shaggorama (talk) 20:09, 8 May 2008 (UTC)

chemical, mineral, vitamin make-up of menstrual blood?

I have read that menstrual blood contains all the contents of regular blood, such as plasma, but doesn't it also contain vitamins and minerals and growth hormones? Also I just read of an English firm that is recruiting women to submit their menstrual blood because it contains stem cells. A landscaper friend of mine regularly uses birth control pills to make all his bedding plants look spiffy, which implies that mammalian hormones stimulate plants- and perhaps plant hormones stimulate people?- (Spring fever and all that) Really, I am just looking for a layman's list of the contents of menstrual blood.People777 (talk) 05:34, 7 May 2008 (UTC)

Menstrual "blood" is a misnomer: what is shed during menstruation is the lining of the endometrium. "Menstrual fluid" is closer to correct. There's blood mixed in there, but it's not the main constituent. I don't know where you'd find an analysis of it, but I'm sure it contains as many vitamins or minerals as you'd find in any body tissue. It certainly contains endometrial cells, cervical mucus and vaginal secretions. As to the birth control pills: plant hormones and human ones are similar; plant sterols and estrogen are synthesized by similar pathways. - Nunh-huh 07:14, 7 May 2008 (UTC) (actually, there are papers, but I don't know that there's online access: e.g. Am J Obstet Gynecol. 1965 May 15;92:183-8 14281826 (P,S,E,B) THE CONTENTS OF MENSTRUAL FLUID: AN ANALYSIS OF 260 SAMPLES FROM HUMAN FEMALES. M S BURNHILL, C H BIRNBERG

Have you looked at our Menstruation article? Blood as the body's transport medium contains many substances including vitamins. Phytoestrogens are plant substances that mimic estrogen. 71.236.23.111 (talk) 07:37, 7 May 2008 (UTC)

A new Vector Energy Interpretation of Quantum Mechanics - what to do?

This derives from a very thorough paper (external) that examines relativity if time were treated as a vector. To the best of my ability, the derivations look valid. Combined with the transactional interpretation one can derive an "offshoot" interpretation that treats a negative energy vector as a photon traveling backwards in time. The interpretation's main premise is that these photons are absorbed by empty space and since energy is added, must be conserved as in pair production (other things conserved too); or the tunnel effect being a particle in an energy well converting all mass/energy into a negative vector energy photon emission and disappears. Outside the energy barrier empty space absorbs a negative vector photon and the particle appears there.

The problem is that this can be used in several ways, all IMHO have merit.

One of these appears to be absurd at first; it is much deeper, though not many I feel will see the deeper significance. So I don't know what to do?

any help appreciated

reference user:fx303 page for the 'absurd' view. —Preceding unsigned comment added by 67.174.224.78 (talk) 06:07, 7 May 2008 (UTC)

Hello. Can you supply us with anything at all to read on the subject, or at least point to where/under what name this paper has been publicised? Scaller (talk) 14:42, 7 May 2008 (UTC)

I think the OP was referring to User:Fx303#Vector_Energy_Interpretation_of_Quantum_Mechanics. -- JSBillings 01:01, 8 May 2008 (UTC)

Amount of zinc gluconate in Zicam

I understand the formula is propietary, and I have been looking for the patent, but I was wondering how much zinc is actually in it in mg. This is due to problems of zinc destroying nasal tissue, although I'm not sure of the mechanism.

Thanks, JD139.225.81.128 (talk) 14:57, 7 May 2008 (UTC)

Could time be expanding?

Hi. Have physicists considered that time could be expanding like space is? Or does the standing definition of 'time' and the physics around it somehow make this impossible? What if time were expanding (somehow), but we just haven't noticed it (either in real life or theoretically)? I wish I could give more 'punch' to this possibility, but I'm no physics expert... Thanks in advance, Kreachure (talk) 16:44, 7 May 2008 (UTC)

I'm not an expert either but i'm pretty sure time is part of the whole space idea. If space expands, time should expand proportionally and it'd make no difference? Probably wrong, but hey, worth a shot! Regards, CycloneNimrod^Talk? 16:59, 7 May 2008 (UTC)

We mostly define distance in terms of the time it takes light to travel over that distance. I suspect you could describe the expansion of the universe as mathematically equivalent to a static universe with a changing time dimension. As we live in the universe, if the two descriptions are equivalent (as I suspect) then it is probably easier for us mortals to assume the nature of time is not changing. Dragons flight (talk) 17:09, 7 May 2008 (UTC)

The big bang cosmological model doesn't contain anything that I'd describe as "expanding time". The concept doesn't make much sense because expansion is something that happens over time. When you say that something is expanding you mean it's smaller at an earlier time and larger at a later time. You could probably come up with some sense in which "time is expanding"—for example, the time you've been alive is "expanding" at a rate of one second per second—but probably nothing very interesting or meaningful. -- BenRG (talk) 17:28, 7 May 2008 (UTC)

Well, let's pull an Einstein and think about what time is: a measurement of how long it takes for some regular interval to happen. Let's say we had a light clock with a 1 second interval—that is, a photon bouncing between two mirrors and it takes it one second to get from one mirror to the other. Now let's say the space between the mirrors expands with space so it takes longer than 1 second for the photon to go over the space: do we redefine the second, or do we say that that particular clock no longer measures what it used to measure? I would think the latter. But I think the rub is that if all space was expanding evenly, you'd have no way of knowing, though: how would you know your clock no longer worked the same way it used to, without another clock to compare it to? If the same expansion of space affected that clock too, in exactly the same way, then in effect there'd be no way to determine the difference. If, however, the expansion was detectable in one way or another (which our current expansion is, because it affects different scales more than others), then it would be easy to say that the clock had just gotten inaccurate. Someone correct me if I'm reasoning totally wrong here. --98.217.8.46 (talk) 18:23, 7 May 2008 (UTC)

First you have to define time. In an attempt to be overly general (so don't respond with quotes out of your physics book to clarify the specifics), there are two views on time. One view is that time is a dimension (like length, width, and height) that contains events. Objects travel through the time dimension and measure it by the time distance between events. Another view is that time is not a dimension, nothing travels through it, and it does not contain events. It is merely a value placed by humans to make formulas work properly. If you use the first definition, it is possible to claim that the time dimension is expanding since it has the same properties as the other three dimensions. If you use the second definition, time cannot expand because it doesn't exist. -- kainaw™ 18:45, 7 May 2008 (UTC)

The definition of the term "expanding" breaks the symmetry between time and space. Even if time can somehow expand, it can't expand in the same way that space does. It's like asking whether space expands with distance. There's a weird circularity in the idea. You can think of time as an implicit dimension that parametrizes change, or you can think of it as an explicit dimension like space, but you can't have both at once. In the spacetime picture there's no implicit change. Objects don't move along their worldlines, they simply are their worldlines. Changing the past isn't a physical impossibility, it's a logical contradiction. (Actually that's true of either notion of time.) If the original question was whether the time dimension can expand over the course of some other (implicit) time interval, then the answer is no, that doesn't make sense. If the question was whether it can expand over the course of the same time that it itself measures, then I think the answer is still that it doesn't make sense. -- BenRG (talk) 20:12, 7 May 2008 (UTC)

To expand on my comment above. You generally describe the structure of the universe as a whole through the FLRW metric of spacetime:

$\mathrm {d} \tau ^{2}=\mathrm {d} t^{2}-{a(t)}^{2}\left({\frac {\mathrm {d} r^{2}}{1-kr^{2}}}+r^{2}\mathrm {d} \theta ^{2}+r^{2}\sin ^{2}\theta \,\mathrm {d} \phi ^{2}\right)$

Where the scale factor a(t) describe the expansion of space as a function of time. However, I am fairly confident that one could construct an equivalent metric:

$\mathrm {d} \tau ^{2}={b(t)}^{2}\mathrm {d} t^{2}-\left({\frac {\mathrm {d} r^{2}}{1-kr^{2}}}+r^{2}\mathrm {d} \theta ^{2}+r^{2}\sin ^{2}\theta \,\mathrm {d} \phi ^{2}\right)$

where b(t) is a new scale factor, and yet I suspect that if you apply the Einstein equations and follow the construction through it could be designed to give rise to the same dynamical structure. The second metric would be described as having static spatial dimensions and a dynamic time dimension, but from the point of view of any quantities observable by people living in the universe they would give exactly the same behavior. Dragons flight (talk) 20:32, 7 May 2008 (UTC)

P.S. I also think it is possible to construct a system with both dynamic time and dynamic space, but I think there no physically useful reason for doing so as one can always condense all of the variation into one or the other. Dragons flight (talk) 20:39, 7 May 2008 (UTC)

More importantly, if time was expanding in this way (which I think it probably is), do you think we would be capable of noticing it? in relative terms, the amount of time we experience probably would stay the same, for the same reason we don't notice out bodies expanding as the universe does. relativity is a pretty elegant theory. --Shaggorama (talk) 10:11, 8 May 2008 (UTC)

Our bodies don't expand as the universe does. The expansion is defined in terms of real physical distances that we can measure; our measuring devices tell us that the universe is expanding at large scales but human bodies aren't. The trouble with the b(t) metric above is that it doesn't describe a measurable expansion the way the FLRW metric does. -- BenRG (talk) 18:05, 8 May 2008 (UTC)

No, this metric won't work. Make the substitution $t'=\int _{t_{0}}^{t}b(u)\,du$ and it becomes

$\mathrm {d} \tau ^{2}=\mathrm {d} t'^{2}-\left({\frac {\mathrm {d} r^{2}}{1-kr^{2}}}+r^{2}\mathrm {d} \theta ^{2}+r^{2}\sin ^{2}\theta \,\mathrm {d} \phi ^{2}\right)$,

which is the FLRW metric with a(t ') = 1. The observed geometry of the universe requires a non-constant a. Also, b isn't actually a parameter, since you get the same geometry regardless of b. You could try making b a function of r instead of t. I think this would get you a family of geometries distinct from the FLRW geometries (in which case they still don't describe the real world), but I'm not entirely sure. -- BenRG (talk) 18:05, 8 May 2008 (UTC)

This does work, though: $\mathrm {d} \tau ^{2}=b(t)^{2}\mathrm {d} t^{2}-t^{2}\mathrm {d} \mathbf {x} ^{2}$, if you take $b=(a^{-1})'\,\!$, i.e. the derivative of the inverse of a. (I'm writing $\mathrm {d} \mathbf {x} ^{2}$ for the big parenthesized part of the metric.) The only caveat is that a has to be invertible (and have no critical points), which rules out a recollapsing universe but doesn't rule out the Lambda-CDM model. For k > 0 the "picture" you get from this is a universe with the big bang at the center and later cosmological times represented by concentric spheres. Distances within the spheres are what you'd expect from a background Euclidean geometry, but distances from the center are timelike and scaled by b(t). So this is something like an expanding/contracting time picture of the FLRW universe. You're free to think of the universe this way, but I think the usual expansion picture is intuitively clearer. (The usual picture can even be understood in Newtonian terms—see this long thread.) -- BenRG (talk) 14:15, 10 May 2008 (UTC)

The Doolittle Raid

Why wouldn't the U.S. navy install booster rockets to the B-25s of the Doolittle Raid? Wasn't it cheap and proven technology? -- Toytoy (talk) 17:29, 7 May 2008 (UTC)

Perhaps a better question is "why would they?" Based on our JATO article, it doesn't appear the US had them at this point, and I doubt that they'd be classified as "cheap and proven" at that stage even if they did. Training for the raid had already established that B-25s should be launchable from a carrier, so why would the Navy and Army add extra unnecessary complexity? — Lomn 19:01, 7 May 2008 (UTC)

The rocket boosters, had they been a proven and available technology, might have allowed greater takeoff eweight, thereby allowing more fuel load (possibly via aux tanks) with greater range and thus the possibility to launch farther from Japan with greater safety for the carrier and less chance of premature detection, or with a greater bombload, or with a greater chance of making it on to a safe landing in China. Edison (talk) 19:43, 7 May 2008 (UTC)

As I recall (from the book version of Thirty Seconds Over Tokyo), the B-25s were already doing stuff like carrying jerry cans of fuel internally. While I concur that in principle with the higher weight -> more range -> safer mission principle, I don't know that any practical payoff was likely (bomb load vs range is a different matter, I guess, but meh -- it was a propaganda raid. 5% more bombs doesn't affect that). Regardless, a large part of the range problem was the premature launch of the mission due to possible detection, though my personal opinion from reading about this as well as the Flying Tigers is that the US was overly optimistic to expect these aircraft to successfully rebase out of China. — Lomn 19:59, 7 May 2008 (UTC)

Retrospective analysis can always find superior solutions. The Doolittle raid was cobbled together from available pieces in a very short time. With the benefit of hindsight, we can find all sorts of clever improvements. In your scenario, JATO units would have increased the bomb payloads, resulting in much more damage to Tokyo. but in an equally likely scenario, one or more JATO units would have failed catastrophically, causing distruction of a B-25 and renderingthe carrier incapable of launching other B-25s. -Arch dude (talk) 02:33, 8 May 2008 (UTC)

I can hardly think of a reason why they could not modify a military rocket for a mission like this. The army has been using ground-based rockets for many years. This proven technology shall be adapted for launching bombers on an aircraft carrier's deck. It can decrease the risks.

Installing jerrycans on a bomber seems to be ... well ... stupid. These cans are heavy and not very efficient. Why couldn't they make a large aluminium oil tank?

I find the jerrycan article funny. Allied scientists had to reverse engineer steel oil cans? Was it rocket science to make cheap and durable oil cans? Hitler ordered jerrycans secretly? Was it really such a big deal to make some oil cans for people? Couldn't the Germans make up a good excuse for making oil/water cans? e.g., "These cans are for delivery of cooking oil to the hospitals." -- Toytoy (talk) 12:44, 8 May 2008 (UTC)

Methinks you overestimate the ease of something like this and the likelihood of success. Getting rockets to work reliably was not an easy task; to do it with manned flight and without causing danger to the launching platform was simply not a risk worth taking in 1942. In any case, thinking backwards like this is a poor historical methodology—all you learn about is yourself, not the past.

As for the jerrycan, I think you also underestimate the materials science and good engineering that goes into that particular steel oil can. Think about it this way: if it was easy to do, they wouldn't have needed to reverse engineer it. They weren't any stupider than people today are. --98.217.8.46 (talk) 13:33, 8 May 2008 (UTC)

What ground-based rockets did the U.S. have in 1942? The German and the Russians deployed things like the Katyusha but these probably didn't have the power to accelerate a bomber significantly. The development of large rockets by the Germans during the war was a major advance. (And so we acquired their technology and personnel after the war.) See Rocket artillery#World War II, V2 rocket. Rmhermen (talk) 14:36, 8 May 2008 (UTC)

Digging deeply through our poorly organized material on Wikipedia, Aerojet tested a U.S. design for a JATO rocket in August 1941 but it didn't go into production until 1943. Elsewhere I found, that in the 1941 test, it took 12 rockets to launch a 1,260 lb max weight plane. A loaded B-25 weighed 33,510 lb so we only need to attach about 320 rockets to each bomber! In April of 1942 (the same month as Doolittle), the U.S. began testing a liquid-fueled JATO on a bomber smaller than the B-25; however, development was abandoned in 1944. Rmhermen (talk) 14:54, 8 May 2008 (UTC)

Proving Technology for Aerospace Applications

Hi all, does anyone know what sort of tests are required to prove a new technology or material for use on aeroplanes or spacecraft? And what issues need to be considered? So far I've considered:

• An ability to be implemented consistently, reliably
• Withstanding repeated exposure to the pressure and temperature changes likely to be experienced
• A knowledge of how to detect flaws and failings in the material or technology.

I have also found, British Aerospace EAP an example of testing aerospace technology.

This is part of revision for an exam coming up. If anyone has any thoughts, knowledge or ideas I'd be very grateful. Many thanks, LHMike (talk) 18:43, 7 May 2008 (UTC)

Technology Readiness Level has some information on American standards Mad031683 (talk) 19:49, 7 May 2008 (UTC)

Thanks, that's really helpful. Also found Mature technology linked. LHMike (talk) 00:26, 8 May 2008 (UTC)

Biology

Can human polyspermy end as a viable embryo (e.g. by mixoploidy etc.)? Eliko (talk) 19:52, 7 May 2008 (UTC)

Sort of. Such an egg will convert into a pair of diploid zygotes, however. It was never clear to me how that actually happened. Someguy1221 (talk) 23:52, 8 May 2008 (UTC)

Let me quote from the article Polyploidy:

Triploidy, usually due to polyspermy, occurs in about 2-3% of all human pregnancies and ~15% of miscarriages. The vast majority of triploid conceptions end as miscarriage, and those that do survive to term typically die shortly after birth. In some cases survival past birth may occur longer if there is mixoploidy with both a diploid and a triploid cell population present.

So I'm really eager to know about any source for your statement: Such an egg will convert into a pair of diploid zygotes.

Eliko (talk) 07:28, 9 May 2008 (UTC)

I'll just say that Nature said it. I could hunt down their own two references, but it's kind of late, so I think I'm out for the night. Someguy1221 (talk) 09:27, 9 May 2008 (UTC)

And reading the Nature article again, I'll take that partially back. It is never stated that the egg splits into a pair of zygotes, merely that it forms a chimeric diploid embryo that later produces twins. Someguy1221 (talk) 09:29, 9 May 2008 (UTC)

Thank you for the source and for the news, it really helped me. By the way, this source does not indicate that polyspermy "forms" a chimeric diploid embryo - i.e. as a usual result of polyspermy; it just says that a chimeric diploid emryo - may be a "way" (i.e. a possible "way" out of some possible different results) of polyspermy. Please pay attention to the word "way" (in the report summary). Anyways, thank you again for the news: My original question - whether polyspermy can end as a viable embryo - has been answered. Eliko (talk) 13:10, 9 May 2008 (UTC)

Oh yes, I realized that after reading it again, last night. But why yearn for ultra-accuracy with my wording when I trust you're going to double-check the source anyway ;-) Someguy1221 (talk) 17:19, 9 May 2008 (UTC)

Swings and insurance liability

I've seen in other countries swings on which children stand up. I see only swing seats here in America. Does this have to do with the rate of injuries? I find the seats rather boring. Imagine Reason (talk) 20:08, 7 May 2008 (UTC)

That doesn't sound like a science question to me... just google it and see if you can find some studies. I doubt anyone here just happens to be an expert on playground accident statistics (although anything is possible...). --Tango (talk) 22:16, 7 May 2008 (UTC)

You can stand up on any swing with a hard seat. You've never seen a swing with a wooden plank for a seat? --Shaggorama (talk) 10:12, 8 May 2008 (UTC)

Not in public in America you won't (see any swings with hard seats). The legal threat posed by such a deadly item is just too much! So very uncomfortable, not very swingable "sling seats" are all you'll see.

Atlant (talk) 13:14, 8 May 2008 (UTC)

I never had any trouble standing up on a sling seat. --Carnildo (talk) 20:52, 8 May 2008 (UTC)

I didn't know if any desk would be appropriate for this question, and I'd watchlisted this page, so...anyway, if I've seen planks in America, I've forgotten about it. I never saw any seats in Asia, either. I did try standing on the seats, but couldn't stand on their round bottoms. Imagine Reason (talk) 01:02, 9 May 2008 (UTC)

Hm. Hard seats certainly existed in America forty years ago. Did something happen? —Tamfang (talk) 22:28, 13 May 2008 (UTC)

Are old-growth forests being cleared faster than they regenerate?

My question is specifically directed towards the forests in British Columbia, where environmentalists (namely Greenpeace) have targeted most. I know that the UN's Forest and Agriculture Organization (FAO) reports that Canada has maintained over 400,000 hectares of forest cover, but how much of that is old-growth? Does that amount of cover provide old-growth forests to regenerate by the time they are logged again? —Akrabbim^talk 22:06, 7 May 2008 (UTC)

Although the term Old growth forest is somewhat disputed, from what I know it is generally agreed that once it has been cut down it's gone. What you replant is a managed tree lot usually called Secondary forest. Certain features of old growth forest like natural selection of species growth pattern, influence of dead trees and fallen old logs, established drainage patterns and natural territory boundaries are not re-created once the old growth has been logged. UW researchers studied Mount St. Helens after the blast [1] what is not mentioned in this article is, the study plot that was cleared of fallen and dead logs and replanted actually recovered slower than the plots left to their own devices. Some forestry managers now use limited controlled fires to control underbrush, because they found that dousing all fires just made the next fire bigger and more dangerous. Sustainable forestry is no substitute for old growth because it just means that loggers don't take out more trees than they grow. It's like taking out a creek and putting a concrete lined canal there instead. The water still flows but many other factors can not be re-created. On a positive note, some areas of South American rain forest used to be farmed by natives in ancient times and are now almost indistinguishable from undisturbed growth. We just won't leave a forest alone for a couple of centuries for "old growth" to develop again. Hope this will help with answering your question. --71.236.23.111 (talk) 23:52, 7 May 2008 (UTC)

Does that mean that if and only we continue sustainable forestry for a couple of centuries, the answer to this question becomes yes? Of course, that doesn't address the amount of old-growth forests there would be. If we continued to cut down trees at our current rate, and always cut down a certain portion of old-growth trees (say, half the ones we cut down are old growth, regardless of how much old growth is left), then I'm willing to bet the answer would be "none". Of course, centuries from now, humanity would probably either be advanced enough for this make an unnoticeable difference, or extinct. Either way, the only practical time frame is short enough for new old-growth to be, for all intents and purposes, nonexistent. — DanielLC 00:01, 9 May 2008 (UTC)

Nope only if you'd leave your replanted forest alone it "might" happen. What you plant is all the same species and with little genetic variation at that. Trees are planted at regular intervals to enable easy access for machines. They are all the same age. The underbrush is gone. The soil is all stirred up and topsy-turvy. Roads cut through plots depending on local conditions they can either create a wall for water-flow patterns and animal and plant dispersal or a highway for floodwater and opportunistic species (or both). Some modern forestry techniques are trying to copy pages from nature's book, like planting a mix of species, but still while we meddle it won't become old growth. For that to happen you'd have to maybe airlift individual trees out and only cut one every mile or so every 50 to 1oo years maybe. (You might be able to get away with closer together and more often or you might need to do it farther apart and less often.) The trees that you take out would not be available as fallen trunks, but a system can and does usually cope with a little bit of interference. Sustainable forestry just means that there is a tree growing for a tree you cut down. It's as though you'd take the Mona Lisa out of the museum and instead would hang a photograph there. Eventually, in a hundred years or so that photograph might also become art. If it survives a couple of hundred years more it might even become unique art and deserve a place next to the old masters, but if you hang a new picture in the frame every couple of years that's never going to happen. Lisa4edit (talk) 20:48, 9 May 2008 (UTC)

Based on how things work with farming tribes in tropical rainforests, you could sustainably harvest an old-growth forest by cutting one-acre patches amounting to about 0.25%-0.5% of the forest each year. --Carnildo (talk) 21:20, 9 May 2008 (UTC)

Question: What is the compound/name of the chelate of calcium produced by plants?

As chlorophyl is a chelate of magnesium produced by plants, I wish to know any chelate of calcium that is produced during the symbiotic relationship of plant roots and soil microbes. Best answered by a SOIL BIOLOGIST.

I have asked several chemists this question and they always say, "EDTA." We are talking about organic chemistry here. Engintinc (talk) 22:50, 7 May 2008 (UTC)

Well, EDTA certainly will chelate calcium ions, but it's a synthetic molecule, and not really something made by plants. (And if you're interested in calcium specifically, EGTA may be a better bet for a synthetic chelator.) For natural compounds, you're probably looking for a calcium equivalent to siderophore. Unfortunately, I am unaware of any such molecules, although they certainly may exist. -- 128.104.112.85 (talk) 14:37, 8 May 2008 (UTC)

Conservation of angular momentum

During a physics lab on the conservation of angular momentum, we were asked to sit on a chair could rotate effectively frictionlessly. After firmly placing our feet on the ground, someone spun the wheel, and then we were asked to flip the wheel. Now, as per the conservation of angular momentum, it is expected that we would spin in the opposite direction, and that is what we observed. However, what I don`t understand is what causes the person in the chair to spin. To illustrate my point, let us consider linear momentum. Linear momentum, like angular momentum, is conserved if the sum of the external forces on the system is zero. Now, force is by definition what causes a change in momentum, so the fact that momentum is conserved if there are no external forces is fairly obvious. But, when a stationary object is hit by a moving object, the fact that the stationary object moves is because not because momentum is conserved, but because there is an internal force acting on the object. So, my question is this: when considering angular momentum, what causes the person in the chair to spin? It must be a torque (the rotational equivalent of force). But what is the source of the torque? Also, a perhaps related question, why is it hard to flip a spinning wheel? Can how hard it is to spin be calculated?

Could you please re-explain the scenario in your lab? I'm having trouble following it. Oh, and please remember to sign your posts using four tildes (~~~~). -mattbuck (Talk) 23:22, 7 May 2008 (UTC)

You're sitting in a chair that can spin, and you're holding a wheel (the wheel can spin; it has handles of sorts going through the center of the wheel). Someone spins the wheel (it is parallel to the floor), and the you flip it 180 degrees so that it's spinning in the opposite direction. Afterwards, you begin to spin. —Preceding unsigned comment added by 76.69.240.138 (talk) 23:30, 7 May 2008 (UTC)

I'm pretty sure it's Newton's 3rd law - equal and opposite forces. The spinning wheel has angular momentum, and when you flip it, the torque you provide changes the direction of the angular motion 180 degrees, so you receive an equal force in the opposite direction, causing you to spin, conserving (angular) momentum. —Akrabbim^talk 23:38, 7 May 2008 (UTC)

Yeah, the force making you spin is the reactive force to you moving the wheel. It's the same basic principle as rocket propulsion - sit on the same chair with a heavy weight and throw it away from you and the chair will move backwards. This is just the rotational equivalent. --Tango (talk) 00:35, 8 May 2008 (UTC)

Okay, I think I get it. But why is it hard to flip the wheel, and how can this be calculated? —Preceding unsigned comment added by 76.69.240.138 (talk) 00:53, 8 May 2008 (UTC)

You can think of it as the rotational analogue of Newton's 3rd law - essentially, when you try to flip the wheel, you are applying a torque to the wheel (torque is a change in momentum over time, just like force is a change in momentum over time). The wheel applies an equal and opposite torque to you! You may need a pencil and paper to see this properly - the angular momentum vector of the wheel is initially vertical. As you flip the wheel, you're changing the angular momentum vector, and the torque is in the direction of that change; as you flip the wheel, there is a torque with some component in the vertical direction, and the equal and opposite torque on you and your chair produces your angular acceleration. It is "hard" to flip the wheel for the same reason it's "hard" to throw the wheel across the room to give yourself linear momentum - both you and the wheel have rotational inertia! Using the equation in our article on precession (look in the torque-induced precession section), the net torque causing you to spin will be $\tau =\omega _{p}\omega _{s}I_{s}\sin(\theta )$ where $\omega _{p}$ is the angular speed of your flipping motion, $\omega _{s}$ is the spin angular speed of the wheel, $I_{s}$ is the angular moment of the wheel, and $\theta$ is the angle of the axis of the wheel to the vertical. It is possible to think of the forces "microscopically", i.e. in terms of the forces on each part of the wheel but it is pretty tedious in my opinion. If you want to see that treatement, there's a decent one in the aforementioned article on precession. --Bmk (talk) 01:30, 8 May 2008 (UTC)

Got it! Thanks a lot. —Preceding unsigned comment added by 76.69.240.138 (talk) 02:49, 8 May 2008 (UTC)

Momentum of a photon

How can a photon, which is massless, have momentum? —Preceding unsigned comment added by 76.69.240.138 (talk) 23:14, 7 May 2008 (UTC)

A photon has zero rest mass. However, under special relativity, accelerating particles gain mass. If you were to accelerate a massive particle to the speed of light, its mass would become infinite. Hence it is necessary for a photon to be "massless" for it to be able to travel at the speed of light. Confusing Manifestation(Say hi!) 23:26, 7 May 2008 (UTC)

You've probably heard of the equation "E=mc²". It describes an equivalence between mass and energy - that equivalence goes a further than that simple formula (which is the special case for objects at rest - a photon isn't at rest, since it always moves at the speed of light). While a photon has zero rest mass, it has a positive energy, and that gives it a momentum. That momentum (in a vacuum, at least) is $p={\frac {E}{c}}={\frac {h}{\lambda }}$ where h is the Plank constant and lambda is the wavelength. --Tango (talk) 23:32, 7 May 2008 (UTC)

I never thought about that. that's messed up. --Shaggorama (talk) 10:14, 8 May 2008 (UTC)

Relativity can be rather counter intuitive... For example, even though photons are massless, they are still affected by gravity in the same way as anything else (a beam of light on Earth will fall at 9.81m/s/s - it's hard to tell, since it's out of sight before it's fallen a noticeable amount, but it does fall). --Tango (talk) 13:28, 8 May 2008 (UTC)

[repost from old question] Be careful with that equivalence! As described at general relativity, light suffers twice the deflection that one would naïvely expect from analogy with a fast rock. --Tardis (talk) 15:30, 8 May 2008 (UTC)

Interesting... what causes the difference between a very light particle travelling at 0.999999c and a photon? --Tango (talk) 20:18, 8 May 2008 (UTC)

all I can think of is that maybe light is refracted by the gravitational time dilation in addition to the distortion of space.Em3ryguy (talk) 21:26, 8 May 2008 (UTC)

I'm confused. I was told once that it was one half the expected value. Also you might find this interesting-http://www.experiencefestival.com/a/Newtons_aether_model_-_Modernised_Newtonian_theory/id/5333093Em3ryguy (talk) 20:41, 8 May 2008 (UTC)

It's twice, but that only applies at large scales where the whole gravitational field is involved. In local experiments where the field is uniform, light falls at 9.8 m/s² just like everything else. (You can see this from the equivalence principle: imagine doing the same experiment on a rocket ship accelerating at one gee.) The extra global deflection comes from the fact that the circumference of a circle around a gravitating object is less than π times the diameter. Here's an analogy: take a circular sheet of paper with a pie-shaped wedge missing. Draw a straight line which intersects one edge of the missing wedge and a second parallel line which intersects the other edge. Pull the edges together, making a cone, and extend the lines across the seam in as straight a fashion as possible. Going around opposite sides of the cone has caused them to converge. This deflection is (in a certain sense) independent of the speed of the object, whereas the "ordinary" deflection of course depends on the speed. At light speed they have the same magnitude; at 0.999999c they have almost the same magnitude; at small speeds the "ordinary" deflection dominates. -- BenRG (talk) 01:14, 9 May 2008 (UTC)

That makes sense. I thought it odd that a photon would behave significantly differently to a very fast moving light massive particle... --Tango (talk) 18:07, 9 May 2008 (UTC)

In special relativity the relation between energy and momentum is E² = (pc)² + (mc²)², where m is the rest mass. When people say the photon is "massless" they mean that m = 0, which implies that E = |p| c. Both E and p are always nonzero. -- BenRG (talk) 01:14, 9 May 2008 (UTC)

centripetal motion of car

I was given a question where a car of known mass was turning on a circular road of known radius and coefficient of static friction. The question then asks what's the maximum velocity of the car. That wasn't to difficult, but I have a theoretical question. In this question, I treated the centripetal force as the static friction force, but for this to work the static friction force should be pointing to the center of the road. But it's pointing along the path of the car. Then, how can static friction cause centripetal motion. Wouldn't we need the angle of the tires to treat friction vectorally? —Preceding unsigned comment added by 76.69.240.138 (talk) 23:25, 7 May 2008 (UTC)

The scope of the question seems to be assuming that the tires are rolling ideally, that is to say no slipping. The torque the axle provides causes the tire to push backwards on the road. Since the wheel is not slipping, that force is solely static friction, as the rubber is not necessarily moving in relation to the road, as each infinitesimal point of the tire touches down on the road in an instant, pushes back, and then is removed from the road, as the tire rolls. —Akrabbim^talk 23:44, 7 May 2008 (UTC)

I don't think you've understood my question; perhaps I was unclear. I know why the car moves. It is a simple application of Newton's third law. My question is why we treat the centripetal force as equal to μ*m*g. After all, isn't the friction force not directed at the center of the circle of motion. —Preceding unsigned comment added by 76.69.240.138 (talk) 00:18, 8 May 2008 (UTC)

I think it has to do with the fact that the tires aren't pointing in the direction of travel. I'm not sure about the details, though... My attempt to work it out ended up with the car going in the wrong direction, so I'm clearly missing something... --Tango (talk) 00:31, 8 May 2008 (UTC)

The car is observed to be moving in a circle at constant speed. Therefore, the car is constantly accelerating toward the center of the circle. Therefore, there a is force acting on the car and the force is acting in the diretion of the center of the circle. The only force acting on the car (in a pure gedankenexperiment) is the friction between the roadway and the tires. Therefore, the direction of this force must be toward the center of the circle. Conclusion: the vector of the force is in this case perpendicular to the direction of motion. -Arch dude (talk) 02:03, 8 May 2008 (UTC)

From this, we can see that your "obvious" assertion (that the friction force is in the direction of motion), is incorrect. -Arch dude (talk) 02:12, 8 May 2008 (UTC)

There is no motion. In static friction, the two objects touching (the bottom of the wheels and the ground) remain stationary compared to each other. The rest of the car isn't touching the ground, so its motion is irrelevant. The friction force is in the opposite of the force acting upon it (centrifugal force). — DanielLC 23:48, 8 May 2008 (UTC)

May 8

Taste vs. Smell

I read our articles on "the 5 senses."

When i get sick, I can't really taste anything. Does this mean that taste is a sub-set of the sense of smell? Are the two linked in some way? If I smell something foul, am I also tasting particles of it?

Can those without a sense of smell still taste, what about the inverse?

Thanks-- —Preceding unsigned comment added by 24.218.24.148 (talk) 00:22, 8 May 2008 (UTC)

Apparently if you eat an orange with a banana under your nose, the orange tastes like a banana. Don't know where I read that, sorry. LHMike (talk) 00:28, 8 May 2008 (UTC)

There is definitely a strong relationship between taste and smell. Just try eating something while holding your nose. I don't know the details, though, really... They are the same basic thing, though - both involve detecting certain molecules, either in the air or in things we eat and drink. --Tango (talk) 00:30, 8 May 2008 (UTC)

The taste+smell thing is called flavor. See the article for loads of info. — Kieff | Talk 01:43, 8 May 2008 (UTC)

You may be interested in a recent profile of noted chef Grant Achatz, who has partially lost his sense of taste due to cancer. The article discusses the relationship of scent and taste in some detail. -- Coneslayer (talk) 17:56, 8 May 2008 (UTC)

Smell and taste are both chemical detection methods. While smell primarily works on gases, taste primarily works on liquids. There's lot of overlap though, as many liquids also evaporate to produce fragrant gases, and strong odors also contain gases that can dissolve in the saliva on the tongue. StuRat (talk) 02:03, 9 May 2008 (UTC)

The smell of any substance is recognized by the Olfactory lobe of the brain. The tiny particles from the smelling substance reach the sensors and trigger some particular chemical reactions. On the other hand taste is perceived by taste buds on the tongue surface. But, generally, we recognize any food items by the combined signals of its smell and taste, and memorise the feeling as taste of the substance. It is like matching any object by the use of two different attributes together (e.g. if something is liquide and white in colour, we think it may be milk). However, when one falls ill (specifically cold and caugh), the smell of the food cannot reach the sensors and hence, the individual fails to get the combined sugnal, what he or she recognises as taste of the materials and it appears tasteless to him/her. Also, sometimes medication with antibiotic drugs affects taste buds and everything appears to have a metallic taste. Dr.Rajarshi (talk) 10:33, 9 May 2008 (UTC)

Practically speaking, "smell" only samples gases and "taste" liquids because we happen to sniff with our noses and drink with out mouths. There are few bio-molecular reasons that non-volatile liquids cannot stimulate our smell receptors and volatiles our taste receptors. Indeed, in many species animals will sniff up liquid droplets and thereby smell liquids directly, some even have a distinct olfactory sub-organ for doings so.

As others say, you can both taste without smelling and smell without tasting. Losing one does not alter the detection of the other type of chemosensation. But if you lose one, then you lose the ability to determine flavor, which is the perception we assign to the combined sensation of taste + smell. Flavor is what what we really mean when we talk about the "taste" of something in general terms. This is why it appears we lose taste when we can't smell, because our sense of smell contributes a lot more to the flavour that we generally think. In contrast, losing the ability to taste doesn't have too much effect on smell, because we often smell things without tasting them, but rarely taste things without smelling them.

Incidentally the olfactory bulb (or lobe) doesn't recognize smells per se. The odors are detected by the olfactory epithelium, processed by the olfactory bulb and projected to cortical brain regions, which does the recognition and attribution. Rockpocket 01:38, 10 May 2008 (UTC)

Just try eating bittermelon without tasting at least some of its bitterness. Except in seniors the bitter taste is like 1000x stronger than the sweet taste sensors or something like that. Thanks. ~AH1^(TCU) 01:57, 10 May 2008 (UTC)

Decibels

I read about a set of billboards that show the noise level in decibels of the surrounding area. From an acoustics class I took, I remembered there were a few ways to measure sound levels in decibels. After reviewing the relevant articles in Wikipedia, I deduced the decibel numbers on the billboards are likely sound pressure levels, maybe unweighted or using A-weighting.

When measuring street noise, how large of a difference would there be between the different weightings?

Also in terms of street noise, how much does the location of the sensor affect the decibel reading?

--Bavi H (talk) 00:45, 8 May 2008 (UTC)

dB (decibel) is a ratio, not an absolute measure of sound. Thus, it is valid to say that "ambient sound increased by 20dB" (i.e, there is 100 times more acoustic power) without specifying any particular absolute level. To specify an abolute level, you must relate the level to a particular absolute standard: 0dB(SPL) is the smallest (absolute) acoustical energy perceptible to a (statistically average) human, and 20dB(SPL) is 100 times as much acoustical energy. The various alternative measures differ in the ways they assign weights to the frequencies in the acoustic spectrum. Each such weighting is a convention that derives from some perspective, not a mathematical or physical fact. The only objective measure of sound at a particular location would be a spectral graph, and even that is only valid for a particular integration period.-Arch dude (talk) 01:35, 8 May 2008 (UTC)

To answer your question on the different readings you would get with different weightings for street noise - you cannot say because it depends on the exact frequency content of the noise in that particular street at that particular time. Even with unweighted measurements, it makes a difference what frequency range the measurement is filtered to, but again, this cannot be enumerated without reference to the spectrum of the particualr sound you are measuring. SpinningSpark 21:29, 8 May 2008 (UTC)

Expanding Universe

Thanks everyone for the help so far! But there's still something I'm missing: if the universe is expanding, what is in the space before the universe expands into it? Is it impossible to know how far that area on non-universe goes or if there's something on the other side? Evaunit♥666♥ 00:52, 8 May 2008 (UTC)

Generally, the Metric expansion of space is defined by the objects in the universe, and the distance between objects. Said simply, the expanding universe isn't expanding into anything, it is simply increasing the distance between objects. -- JSBillings 00:58, 8 May 2008 (UTC)

Take a non-inflated balloon. Draw some dots on it. Now blow it up and watch the dots - they move apart as the balloon expands. There isn't an edge of the balloon (considered as just a 2D surface) that's expanding into anything, the expansion is caused by the balloon itself stretching at every point. The universe is the same, just with one more dimension. The only problem with the analogy is that the balloon is a 2D surface existing inside our 3D world - the universe doesn't exist within anything, it simply is, so you need to ignore all of the world except the balloon. Consider what an ant living on the balloon would see. --Tango (talk) 02:04, 8 May 2008 (UTC)

Here's a very concrete thought experiment you can use to understand this concept: Send an astronaut somewhere into space with a stopwatch and a flashlight, and put a mirror very far away from him/her, such that the astronaut and the mirror are stationary with respect to each other. Have the astronaut shine the flashlight at the mirror, and time how long it takes for the light to make the round trip. When cosmologists say "space is expanding", it means that if the astronaut repeats the experiment over time, the astronaut will measure that the round trip time is increasing!! There are a few tricky issues about making the mirror and astronaut "stationary", but they aren't too difficult to figure out. That's basically all we know about this concept of "expanding space". It's anyone's guess what it really means - physicists have come up with an intuitive description of the concept, and a comprehensive mathematical formulism (see general relativity) that seems to describe it. -Bmk (talk) 02:23, 8 May 2008 (UTC)

PS: They have to be very far apart wait a very long time in between trials for a measurable effect (i.e. not on humanly accessible distances or time scales). --Bmk (talk) 04:48, 8 May 2008 (UTC)

Mu (negative) --Shaggorama (talk) 10:17, 8 May 2008 (UTC)

Centrifuge

Seeing as we are now in the era of unmanned space travel for a while, why would it not be a good idea to build a centrifuge in orbit around the earth and use it to catapult unmanned space ships at extreme velocity, thus shortening the time for travel to other planets? Also, as we will be re-entering the 'manned space race to unearthly bodies' in the near future, what effect would this system have on astronauts, considering they are already in practically zero gravity? Would the 9Gs or more affect them? My question is, in a zero gravity environment, how would this work, if at all?--ChokinBako (talk) 03:30, 8 May 2008 (UTC)

A centrifuge, flinging a ship with that much velocity, would itself be flung back towards to Earth with tremendous speed, would it not? I can't envision how this will work... 206.126.163.20 (talk) 03:37, 8 May 2008 (UTC)

Well, you could fling two similar ships in opposite directions without altering the centrifuge station's trajectory much, but I don't really see how this system could become more feasible than rockets. Perhaps it could be valuable for unmanned missions, but according to our article on g-force, NASA recommends limiting human acceleration to around 10 Gs for a few minutes of exposure. A centrifuge that is - let's be very generous - 500 m in radius (that's a kilometer in diameter!) with a centripetal acceleration at the edge of 10 Gs would only send a spaceship flying off at 220 m/s (that's 500 mph), which is not terribly impressive considering unmanned spacecraft going to mars average speeds in the 30,000 m/s (75,000 mph) range. Unfortunately, the speed goes up with the square root of radius and square root of acceleration, so if you double the permissible acceleration and double the radius (which seems improbable to me), you only get 1000 mph exit velocity. I think moon-based linear accelerators (using a rail gun or something) for unmanned craft is more feasible. --Bmk (talk) 04:38, 8 May 2008 (UTC)

Additionally, how are you putting the spacecraft on the centrifuge to begin with? It seems that your options are to either stop and restart the centrifuge or accelerate the craft up to centrifuge speed, neither of which suggests an advantage over just launching the craft normally. — Lomn 12:15, 8 May 2008 (UTC)

You could load them in at the center, then feed them down the length of the arm from there. Also the 2 arms don't have to be the same length, one side could be shorter but more massive, but you still wouldn't even be able to get velocities out of it that would even be close to the orbital velocity of the centrifuge, and if Bmk's correct it would still be going less than escape velocity. Mad031683 (talk) 15:14, 8 May 2008 (UTC)

It might be easier to use a Gravitational slingshot, though I couldn't say for certain as I don't have much expertise in this area. AlmostReadytoFly (talk) 13:18, 8 May 2008 (UTC)

You'd need a booster to get into a trajectory around another planet or you couldn't get the angles right from what I gather, so no savings. This is from an old Discover Magazine article [2] "Meanwhile, mechanical engineer Stephen Canfield of Tennessee Technological University in Cooksville and others are investigating using a whiplike tether to hurl a probe from Earth orbit toward another planet, eliminating the need for a booster rocket. "The idea is to store up a lot of energy by spinning the tether. Then you release that energy by briefly capturing a payload on the tether's end," Canfield says. They also had another rotating system they proposed that tossed and caught loads until it reached escape velocity the concept drawing for it looked sort of like a ninja shuriken with only 2 prongs. (Can't find that one. I had filed it somewhere for later reading.) I admit I'm quite nebulous on the concept, too, but it must work out somehow. The only tether I know of that they tried in earth orbit fried because they hadn't thought they'd get that much juice from just dangling a wire and there was a problem with isolation. Can't figure out how they'd make use of the induction in the spinning tether but maybe the two are not related. You'd get less power in a lunar orbit, but you wouldn't have to deal with an atmosphere. 71.236.23.111 (talk) 21:56, 8 May 2008 (UTC)

An interesting feature of a space elevator is that, if you had one, you could also use it as a centrifugal launch platform: it has to extend some distance beyond geostationary orbit anyway, in order to provide a counterweight to the lower portion, so anything thrown off the top will get flung away from the Earth — the energy for this ultimately coming from the Earth's rotation. —Ilmari Karonen (talk) 12:44, 11 May 2008 (UTC)

Indeed, in one beanstalk proposal I've seen, the height was said to be enough to fling to Saturn or Venus. —Tamfang (talk) 00:35, 14 May 2008 (UTC)

Pls, helping to answer this question !?

What is the difference between macronutrients and micronutrients? Will the consequences of depriving a plant of a micronutrient be less severe than those of depriving the plant of a macronutrient? —Preceding unsigned comment added by 121.1.58.38 (talk) 03:51, 8 May 2008 (UTC)

I would recommend you read wikipedia's article on micronutrients. A macronutrient is simply a nutrient which is required in large quantities to sustain life, like water, carbon dioxide, and nitrates for plants. It's hard to answer your second question precisely - can you be more specific? I would suspect removing water or air supply will kill a plant much more quickly than removal of the supply of most micronutrients. --Bmk (talk) 04:22, 8 May 2008 (UTC)

First of all I would like to differ and negate the answer given above. It was wrongly dealt with. However, to answer your question, both micro and macro nutrients can be defined as essetial elements required for the plant growth and defficiency of which leads to certain metabolic disorders having definite symptoms. Only difference is that micronutrients are necessary in micro quantity while macro nutrients are necessary in large quantity for the plants growth. Carbon, Oxygen, Nitrogen, Hydrogen, Calcium, Magnaseum, Phosphorus, Potassium and Sulfur are macro nutrients, while Iron, Chlorine or Chloride, Zinc, Molybdenum, Manganese, Copper, Boron are major micronutrients. Sometimes Iron is also kept in the list of macro nutrients. So, difficiency of any of any of the nutrients will be similarly sever, and that will have some definite symptoms. —Preceding unsigned comment added by Dr.Rajarshi (talk • contribs) 05:14, 8 May 2008 (UTC)

I might be missing something here but the good doctor Rajararshi vehemently seeks to "differ and negate" from Bmk's reply, but then paraphrases it almost word for word. Bmk is wrong (I believe) to class air and water as nutrients, but apart from that their answers are much of a muchness Myles325a (talk) 03:09, 9 May 2008 (UTC)

Both answers agree on the definition of macro and micro nutrients. After that point, I think Bmk and Dr.Rajarshi are talking about 2 different things. I think they are both right.

Bmk talks about whether lack of a micronutrient will kill a plant. I think a plant with an adequate supply of micronutrients could live a long time if its supply of micronutrients was stopped (i.e, it did not get any more, but kept what it had.)

Dr.Rajarshi says that a deficiency in any nutrient, macro or micro, will cause definite symptoms. If a plant needs a particular nutrient to grow normally, lack of that nutrient will stop it from growing, or at least affect its growth.

That's my take on it. CBHA (talk) 04:47, 9 May 2008 (UTC)

The comment has flickered some controversies, which may not be desirable. But, the terms 'macronutrient' and 'micronutrient' are two definite scientific terminologies and those refer only to the nutrients listed above. There is no scopes left, that both the answers are correct. However, it is absolutely right that, if any of the nutrients (be it micro or macro) is necessary for growth, then deficiency of the same will affect the growth. It is also true that if the minimum amount of nutrient is available, then the proper growth and other functioning will continue, irrespective of the fact, whether it is being supplied from outside or not. Dr.Rajarshi (talk) 09:57, 9 May 2008 (UTC)

Organic Matter

Organic matter is not advisable to be added to paddy soils. Yes or No? Why? —Preceding unsigned comment added by 121.1.58.38 (talk) 03:59, 8 May 2008 (UTC)

Decomposition#Plant decomposition, Eutrophication and Hypoxia (environmental) might help. --71.236.23.111 (talk) 06:17, 8 May 2008 (UTC)

Pic

At 2:05 in [3], there's a picture of a cat with crazy blue eyes. Is that really possible? Black Carrot (talk) 05:23, 8 May 2008 (UTC)

No, it is photoshopped, to make the kitten look like someone who takes spice. --98.217.8.46 (talk) 20:22, 8 May 2008 (UTC)

Gingiva Recession

My gums are receding. My dentist says it's probably genetic. But I did not tell my dentist that my sister and mom have recession (see below).

My sister has recession, and I believe she has been flossing once and brushing twice a day. I never had recession, and my dental hygenine is the same. I think I am actually noticing recession. Is that possible? Because I haven't changed how I brush and floss to months ago, but it seems like my gums are receding faster. Also, my mom has recession, but she doesn't floss every day, but I think she at least brushes once a day.

Why can't recession be reversed, as in, why can't I build up bone growth again? How come I lose bone growth and can't gain it back? What are the causes of genetic gum recession? And have there been research to determine if bone can be rebuilt (in terms of gum recssion)? If not, why can't bone be rebuilt (in terms of gum recssion)? And what new research is being done to see if bone can be rebuilt? What are the new techniques? Thanks so much for all your help.68.148.164.166 (talk) 02:45, 7 May 2008 (UTC)68.148.164.166 (talk) 02:48, 7 May 2008 (UTC)68.148.164.166 (talk) 02:48, 7 May 2008 (UTC)

This is not medical advice and I'm no expert, but you might find more information on the following pages Receding gums, Periodontitis (look at the mention of risk factors there), Osteoimmunology As to your question why it can't be reversed (yet?) may be that despite surprising results (see Refdesk, "Humpty" May 2 ) our understanding of how cells work and what it takes to start and stop them from growing is still poorly understood. Particularly in dentistry, bone grafting and autologous (own) Stem cell treatments are areas with lots of studies on the way. Whether the results will be generally applicable, feasible and when they will reach common practice is another question. Lisa4edit (talk) 04:05, 7 May 2008 (UTC)

(see Refdesk, "Humpty" May 2 )???68.148.164.166 (talk) 09:40, 8 May 2008 (UTC)

Look particularly at the Scientific American article linked [4] I hope this works. If not click "Archive" above and look at May 2 in the Science desk archive. 71.236.23.111 (talk) 19:51, 8 May 2008 (UTC)

subliminal masseging

how to make subliminal messaging to subconcious mind —Preceding unsigned comment added by 117.197.48.133 (talk) 17:09, 8 May 2008 (UTC)

Subliminal message? Not sure what you're asking. --Ouzo (talk) 17:45, 8 May 2008 (UTC)

As a note, subliminal massaging would be, well, not that much fun, I imagine. Or would it? --98.217.8.46 (talk) 18:03, 8 May 2008 (UTC)

Really? Then why do you feel so good today? Nil Einne (talk) 19:34, 8 May 2008 (UTC)
Let's just get that nice spot right between your shoulder blades. Isn't that nice? Just relax, and let my hands take care of the work.

Huh? I don't know what you are talking about. There's no such thing. Obvious nonsense, that's it. --98.217.8.46 (talk) 20:24, 8 May 2008 (UTC)

It was once 'obvious nonsense' to propose the Earth was round. Don't dismiss things, unless you have proof to the contrary. Regards, CycloneNimrod^Talk? 20:29, 8 May 2008 (UTC)

I think you missed the joke. --98.217.8.46 (talk) 02:48, 9 May 2008 (UTC)

Please then, share your subliminal massaging technique. 24.76.169.85 (talk) 20:52, 8 May 2008 (UTC)

Sorry to post spam, but actually, you can buy such a thing [5] SpinningSpark 20:56, 8 May 2008 (UTC)

Havat our article on Hypnosis. Julia Rossi (talk) 23:54, 8 May 2008 (UTC)

If you are refering to "Neurolynguistic Programing" techniques, I can help you. An example of one of these tactics would be as follows:

Say you need to feel more confident. Close your eyes, and visualize yourself in a past time, when everything just clicked (everyone has at least one, whether it was with family or close friends.) Visualise yourself in the moment, pay close attention to the sounds, visuals, and environment. Try to make them as vivid as possible. Now imagine yourself stepping out of the "flashback" and see yourself watching yourself in this situation. This allows you to become an observer. Take some time, once again to visualise and make sounds, pictures, and envioronments as real as possible. Following this, (still playing an observer) imagine a time when you'll need this confidence again, say like a party, or a wedding. From there, visualise yourself stepping into that scene (whatever it may be). Once again, try to make everything as real in your mind as possible. Open your eyes, and let your subconcious do the rest!. This technique can be applied wherever needed. Even if you are nervous for a test. I use these techniques all the time, they work wonders for me. However, everyone's different. I would be interested to know who this helps, though. Please give feedback. —Preceding unsigned comment added by 72.40.54.255 (talk) 15:09, 12 May 2008 (UTC)

Validity of Sigmund Freud's work

From a scientific standpoint, how accurate or valid are Freud's theories? In particular, he introduced the world to the concepts of id, ego and super-ego, the unconscious, and others. Are these measurable? If so, how? If, not, why do they still hold such prominence in western society? —Preceding unsigned comment added by 72.35.21.126 (talk) 20:42, 8 May 2008 (UTC)

Psychology is a social science for a good reason, it studies empirically how people act but it, usually, doesn't relate all that much to biological function. Yes, we can detect things like depression by changes in chemicals and the like, but things like the ego are unmeasurable beyond visual observation and just listening. Regards, CycloneNimrod^Talk? 20:56, 8 May 2008 (UTC)

There's a lot of current discussion about this, actually. There are some who argue that modern neuroscience has vindicated some aspects of Freud's work and some who are that it has disproved it. There are also those—largely psychoanalysts, I believe—who argue that Freud's description was not meant to be a literal biological description of the mind, but is a set of concepts that maps well onto how the mind functions, and thus serve as tools for affecting what, at some level, has to be the the neurological basis of behavior and emotion (analogous argument: the basic principles of engineering can be used without any knowledge of how they correspond with quantum mechanics; a reductionist approach can be unreliable on larger scales). And there are those who argue that it is a 19th century, overly literary approach to what should be a harder science. From what I can tell it is all over the board at the moment.

The question of prominence in Western society is a difference one, though, from the question of whether modern neuroscientists use Freud. Freud is wonderfully literary and his idea of deep seated drives, secrets, and internal struggle is one that has appealed to Americans in particular since the 1940s. The ideas triggered strong cultural valences in postwar America and still holds sway today, even though most people know jack squat about cognitive behavior and science. --98.217.8.46 (talk) 23:04, 8 May 2008 (UTC)

Dont forget the idea of psychological energy. The idea that mental processes are subject to 'forces' and 'energies' just like physical processes are. http://en.wikipedia.org/wiki/Psychic_energy. Em3ryguy (talk) 23:25, 8 May 2008 (UTC)

By the way, this article is a combination of 2 articles. 'psychological energy' which is scientific and 'phychic energy' which isnt. see the discussion page for comments. Em3ryguy (talk) 00:15, 9 May 2008 (UTC)

That entire article reads as though it's riddled with pseudoscience. It's especially hard to tell as it isn't well sourced. 206.126.163.20 (talk) 00:23, 9 May 2008 (UTC)

The whole point of psychological energy was to show that mental phenomena are subject to laws just like physical ones. Someone who didnt know what they were doing combined that article with the 'psychic energy' article and screwed it up. Em3ryguy (talk) 00:50, 9 May 2008 (UTC)

The original version of that article describes Freud's theory of energy as 'psychic energy' and directs the reader to that pseudoscience article. I dont believe that is accurate. Em3ryguy (talk) 01:04, 9 May 2008 (UTC)

The original version of the article was poorly explained itself. I'm reading it right now and I don't get the point. It says "Some people think everything in the mind can be explained in terms of energy, though mainstream scientists are hesitant to accept this... general things about hormones and neurotransmitters follow". The last part of which could be stripped out, leaving the article with only a single sentence. That's like an uber-stub. 206.126.163.20 (talk) 01:52, 9 May 2008 (UTC)

Stereographic projection

Stereographic projection example

I need help to make sure that what I wrote at Template:POTD/2008-05-13 actually makes sense. Asked at Talk:Stereographic projection with no response, so trying here. Yes, I know that the article talks about representing spheres with 2-D pictures, and this is kind of the opposite, but it's way down at Stereographic projection#Photography. I mostly just copied-and-pasted from there, but since I didn't really understand this section of the article, I'd like more eyes please. Thanks. howcheng {chat} 21:15, 8 May 2008 (UTC)

You're close. I think the point opposite actually becomes infinitely enlarged - since the picture has only finite area, it isn't the whole sphere, it's the sphere with a small disc around the opposite point removed (roughly - the picture isn't circular, so it won't be quite a disc). --Tango (talk) 22:20, 8 May 2008 (UTC)

Nuclear Bomb Powered Rocket Project

I'm intrigued by a project from the 1950s or 1960s for building a spaceship which was powered by a number of nuclear bombs inside itself, going off at regular intervals to propel the vehicle. I wonder why this was even considered, as if one bomb went off, it would set all the others off, probably devastating half the planet in the process. Sure, it would get into space (or bits of it), but it wouldn't be a good way to do it. The fix for this would be to put each bomb inside some sort of material that is resistant to a nuclear blast, but this would just make the bombs go off inside their own casings and nothing would happen. It seems that NASA actually funded this project, and I have heard a rumour (sorry, forgot source) that they are even considering it again now. Is this true and is it even feasible?--ChokinBako (talk) 23:07, 8 May 2008 (UTC)

Project Orion (nuclear propulsion). First, you don't start the nuclear explosions on Earth, so there's no way for Earth to be "devestated." It would certainly take some radiation from orbital detonations, but if I recall correctly, such an explosion would only have enough radiation to kill ten people (proabalistically speaking, from the increased likelihood of cancer). Once the ship is out of orbit, that would cease to be an issue. As for the explosions destroying the rest of the nukes, this is sovled very easily in the two ways you could do this. If you're firing nukes at the ship from Earth or from an orbital/moon based/whatever platform, then you simply have the explosions take place far enough apart that each nuke is always outside the destructive radius of the previous nuke's blast. If the ship is carrying its own nukes, it simply waits until after each explosion to drop the next one in place. Someguy1221 (talk) 23:45, 8 May 2008 (UTC)

Ah, I see. So, the idea was that the ship would actually 'let go' of one bomb at a time and let them detonate a safe distance from the ship, but close enough to get the propulsion? The diagrams I have seen in the past just showed a rocket with about ten or twenty nuclear bombs inside it and didn't explain that bit. It seems to make some sense now. Thanks.ChokinBako (talk) 00:54, 9 May 2008 (UTC)

That's exactly right. The ship shoots the bombs out behind it, then the bomb detonates, and the force of the explosion is picked up by a big plastic plate (the pusher plate) when then imparts the radiant energy as kinetic energy, moving the ship. This YouTube video does a pretty good job of illustrating its pulsing approach right after it gets out of the atmosphere (in the "re-imagining" of the concept by the guy who made the video, he has it taking off with chemical rockets, to avoid fallout problems on Earth). --98.217.8.46 (talk) 02:39, 9 May 2008 (UTC)

The plan was indeed for the nukes to go off on Earth, as the spaceship was to be far too heavy for a chemical rocket to get it into space. The planners even specified that it would have one of those enormously heavy swiveling barber's chair, just to thumb their noses at the extremely-weight-restricted chemical rocket crowd who eventually won the day at NASA. The effects of atmospheric nuclear explosions were only just becoming known at that time, and when their danger became clear the project was doomed. One of my favorite books is The Starship and the Canoe, a dual biography of Freeman Dyson, who was one of the principal Orion people, and his son George Dyson, who lived in a tree in British Columbia. --Sean 01:03, 9 May 2008 (UTC)

Oh, I didn't realize that was actually the case. In any event, you could still use the concept as an in-space-only propulsion mechanism, since you can still send up your 400 ton space ship in little pieces, then use the bombs for the heavy work of getting to Alpha Centauri in a meaningful time frame. Someguy1221 (talk) 01:37, 9 May 2008 (UTC)

Here's a nice government-produced picture of where the bomb would go off relative to the spaceship, and then it would explode, and then push up against the "pusher plate" of the spacecraft, which would be made of a material that would reflect the energy primarily. Following Newton's whatever law, the act of this reflection would exert an equal and opposite force on the spaceship itself, pushing it along. --98.217.8.46 (talk) 02:45, 9 May 2008 (UTC)

Larry Niven and Jerry Pournelle used this propulsion method in their science fiction novel Footfall. They make the interesting point that for a launch from earth it is the second bomb that is crucial. If the first one fails - well you are still sitting on the deck, have another try. If the third one fails while you are in the air, you have enough time to detonate another. However, if the second one fails, thousands of tons of concrete platform (or whatever you have made the vehicle from) come crashing back to the ground before any corrective action can be taken. SpinningSpark 17:07, 9 May 2008 (UTC)

The fallout issue is unfortunate, because an Orion engine is twice as efficient in an atmosphere as it is in space: the atmosphere lets you catch more of each bomb's energy. --Carnildo (talk) 21:30, 9 May 2008 (UTC)

May 9

How many nucleotides are found in all of the exons of the CFTR gene?

How many nucleotides are found in all of the exons of the CFTR gene? —Preceding unsigned comment added by 65.29.80.238 (talk) 01:23, 9 May 2008 (UTC)

4575 [6] Someguy1221 (talk) 01:32, 9 May 2008 (UTC)

Well, there are non-protein coding sections within exons 5' and 3', but according to EBI Dbfetch (which is the data base I sometimes use in the lab), there are 4443 nucleotides in the mRNA [7]. Wisdom89 _{(T / ^C)} 04:57, 9 May 2008 (UTC)

The mRNA sequence is 4575 long if you end at the last translated codon. The EBI sequence left out the 5' untranslated region, 132 nucleotides long. Someguy1221 (talk) 09:19, 9 May 2008 (UTC)

Yes, you are correct, and hence my reference to 5 prime non-translated regions. This was just in case the user was possibly interested in just the coding region. Wisdom89 _{(T / ^C)} 11:16, 9 May 2008 (UTC)

Voyager Spacecraft

I've read that the Voyager spacecraft are at the edge of the Solar System and are slowing down. Scientists are saying this might be because of some interstellar wind that is pushing against them, making it hard for them to escape the Solar System. Could this not just be the same thing that rockets experience when attempting to reach 'escape velocity' from the Earth (sorry, I forget the correct term)? Could it not be that the Solar System has the same gravitational forces as the Earth, but on a much larger scale?--ChokinBako (talk) 02:32, 9 May 2008 (UTC)

That's quite true, the solar system (which can be greatly simplified to "the sun", for most purposes like these) does exert gravitational pull on Voyager. However, NASA et al have already accounted for this. What you've read likely means that there's an additional force of uncertain origin at play. — Lomn 02:35, 9 May 2008 (UTC)

The gravity from the Sun has been slowing Voyager down since it was launched. But it has plenty of velocity to leave the solar system and after a very, very long time reach some other star. Edison (talk) 03:55, 9 May 2008 (UTC)

I think the questioner may be refrring to the small unexplainned deceleration that has been detected in the Pioneer spacecraft - see our article on the Pioneer anomaly. 199.43.13.101 (talk) 11:05, 9 May 2008 (UTC)

(There's a great graph somewhere on WP of the probe's speed since its launch. I can't find it right now. If anyone has the link to it, it would be welcome.) 200.127.59.151 (talk) 17:57, 9 May 2008 (UTC)

Springtime for France

When does spring arrive in France ("arrive" in the phenological definition)? And when does it arrive in England? (although I imagine it arrives around the same time for both) 96.233.8.220 (talk)PrisonersOfLove —Preceding comment was added at 03:04, 9 May 2008 (UTC)

Would this be what you were looking for Spring (season)? Phenology deals with recording several natural events. It gives dates for a species, based on which next year's date can be predicted, e.g. to within about 55 days (-21, +34) for some flowers. So there is no fixed date. I assume that plants start blooming earlier in the southern part of France than in the northern part, which will be closer to southern England, since both are near the channel (gulf stream influence). But that's speculation. --71.236.23.111 (talk) 18:32, 9 May 2008 (UTC)

I just need to know when it gets warm and the flowers start blooming and it begins to *feel* like spring in those countries. Maybe someone who's lived there can help? —Preceding unsigned comment added by 96.233.8.220 (talk) 19:53, 9 May 2008 (UTC)

Varies heavily from year to year. Last year (in southern England), April was the closest thing we got to summer all year. This year April saw snowfall. See The Guardian letters page passim ad nauseam. Algebraist 08:59, 10 May 2008 (UTC)

France is a geographically diverse country. Marseille is on the Mediterranean. Calais is on the English channel. Alsace is inland. The climates are very different. Google "Marseille climate"[8], "calais climate"[9], and "Alsace climate"[10] -Arch dude (talk) 02:26, 11 May 2008 (UTC)

Why is there no Climate of France article?!!? It's even been redlinked on the List of basic France topics!!! Nimur (talk) 16:38, 14 May 2008 (UTC)

what is the term that refers to the earth's surface features?

the word comes from the latin term terra —Preceding unsigned comment added by Amandalsmithlpn (talk • contribs) 03:23, 9 May 2008 (UTC)

Terrain?--71.236.23.111 (talk) 08:45, 9 May 2008 (UTC)

Cancer

Is cancer just restricted to mammals and people, or can other living things get cancer? Our article makes no mention of other organisms besides humans getting cancer. I know that some trees can live hundreds of years, and I also know that "...cancer-promoting genetic abnormalities may be randomly acquired through errors in DNA replication, or are inherited, and thus present in all cells from birth.", so it stands to reason that really old trees that have undergone mitosis for ages would be susceptible to cancer (unlike insects who only live for a relatively short time). Thanks for all the info! PS-not specifically asking about old trees, just giving an example. I want to know can ANY living organism get cancer (in a nutshell). --71.98.26.52 (talk) 04:02, 9 May 2008 (UTC)

The difference between the way that plants and animals grow means that plants generally don't get cancer (because a huge increase in cell growth in a plant will just make a bigger plant, or one with more branches). However, the gall created by a gall wasp is, roughly speaking, a plant cancer. Confusing Manifestation(Say hi!) 04:13, 9 May 2008 (UTC)

As long as something is made of DNA, mutations are possible. Cancer, as we know it (e.g. tumors and neoplasms), may not be present in every animal or plant but there are other genetic diseases which resemble it. Regards, CycloneNimrod^Talk? 08:51, 9 May 2008 (UTC)

The misleading explanation is removed, thanks for the comments. Dr.Rajarshi (talk) 04:34, 10 May 2008 (UTC)

Unless I misread, but "uncontrolled cell growth" is not termed metastasis. Wisdom89 _{(T / ^C)} 11:13, 9 May 2008 (UTC)

Per Wisdom89, use 'Dr.' Rajarshi's information with caution. The process by which cells become malignant (cancerous) is called carcinogenesis, while the specific steps wherein growth regulation is lost may be called neoplasia. (Note that not all neoplasms are malignant.)

Metastasis meanwhile, is the spread of a malignant tumour from its original site to other locations within the body.

In my experience, the term cancer is used to describe malignant growths in mammals only; uncontrolled growths of cells do happen in other organisms, but usually go by other names. TenOfAllTrades(talk) 13:46, 9 May 2008 (UTC)

Plants do get cancer, but since plants don't have mobile cells, these cancers can't metastasize. --Carnildo (talk) 21:39, 9 May 2008 (UTC)

Interesting...thanks for all of the info. So I'm assuming other organisms which have mobile cells (and that live long) can get cancer that matastasizes, such as those sea turtles that live a hundred years? And I'm also assuming that insects, which live a relatively short time, have almost zilch chance of getting cancer? --71.117.40.7 (talk) 13:51, 10 May 2008 (UTC)

Book-name

What is a book-name?

The term is used in the article Spiny squirrel. Thank you. CBHA (talk) 04:18, 9 May 2008 (UTC)

Here[11] (scroll down) implies it's a "common name" that isn't in use but written down anyway for description purposes in the hope it catches on, as in: [It is] "desirable that well-chosen names be available... if no popular name be already available, a suitable book name will in time come into use as a common name." Julia Rossi (talk) 10:22, 9 May 2008 (UTC)

Meaning of a species name

In the article Bearded Barbet, the scientific name of this bird is Lybius dubius.

Why was it called dubius? Thanks, CBHA (talk) 05:04, 9 May 2008 (UTC)

There are quite a few species with 'dubius' in their name. The term is just what it seems: Latin for the similar word "dubious". My understanding is that species are given this name if the criteria for classifying them as a distinct species or placing them in a specific group is... well, dubious. According to this list of Latin terms used for species classification, the term can also mean "uncharacteristic". Dooky (talk) 09:15, 9 May 2008 (UTC)

Acute chest pain

What are some causes of acute chest pain that would not found by an echocardiogram or chest x-ray? Mac Davis (talk) 05:52, 9 May 2008 (UTC)

Chest pain might hold some clues. 71.236.23.111 (talk) 08:39, 9 May 2008 (UTC)

Just as a forewarning, please read this: Wikipedia:Medical disclaimer. Wisdom89 _{(T / ^C)} 11:10, 9 May 2008 (UTC)

Perhaps this can help you [12]. --Taraborn (talk) 14:36, 9 May 2008 (UTC)

Exothermic reaction

Alkalisation of cellulose with a mixture of ethyl alcohol & sodium hydroxide is an exothermic reaction. Can the heat generated be caluculated in terms of kcals using enthalpies of reactants?59.93.71.174 (talk) 12:11, 9 May 2008 (UTC)

It could be if you knew the products produced. In this case I suspect you may get a complex mixture including sugars and aldol condensation products, too complex to calculate. Graeme Bartlett (talk) 21:45, 9 May 2008 (UTC)

CO2 of fans

Is it more environmentally-friendly to have air-con in an office or for everyone to have electric fans blowing all day? 195.60.20.81 (talk) 14:33, 9 May 2008 (UTC)

It will probably depend on 1. the size of the office space (which gives you the power requirements for the central air), 2. the number of individuals in the office (which tells you how many electric fans there would be), and 3. assumptions about the efficiency of the technology in question (are we talking new, EnergyStar approved air conditioners, or one from decades back?). Not knowing any of those, I would estimate that central air is more energy-efficient under some conditions and individual fans are better for others. Which doesn't say much. --98.217.8.46 (talk) 16:19, 9 May 2008 (UTC)

: "Environmentally friendly" questions are always a tricky can of worms. What the outcome is depends more on who counts what how than comparable data. That's why I'm not going to drag up study A versus study B, but will give you a couple of factors to consider. First of all, if you get a real scorcher electric fans blowing all day are not going to provide the same level of comfort as an AC unit. They offer comparable performance only in moderate heat. This is particularly true if the heat is accompanied by high air humidity (the rule of thumb says to add 10 to the heat index for high humidity). Running an AC unit will actually dry the air. Airflow patterns for office buildings are usually designed with some degree (ideally a high degree) of care. Airflow patterns from individual fans are haphazard and chaotic. Fans cool by creating high volume air flow. This is a less efficient way of cooling than in the AC which uses a refrigeration cycle to actually remove the heat from the air. Central AC creates most of its noise away from your workers, individual fans running at full tilt can cause considerable noise pollution. Central AC can be kept on at a certain temperature setting overnight. If nighttime temperatures don't drop significantly enough the building will heat up overnight when your individual fans are turned off. This can actually lead to a much higher power consumption when the workers come back in the morning and run their fans to try and cool down the "oven". Such influences depend on individual structures and building materials and are therefore impossible to quantify on a general basis. Central AC can be adjusted following guidelines that take energy saving aspects into consideration. With individual fans you have to rely on the individual attitude of each worker. While we can calculate power consumption rates for a central AC at certain settings, calculating the overall power consumption for individual fans is highly arbitrary. Comparing both systems at maximum levels will not give realistic results. How much of an influence additional losses due to distributed power use for individual fans is I'll not consider now, that in any case would also depend on highly variable local factors. So far for power consumption of the units

Average life of an AC unit and individual fans is comparable at about 12 years. After that time you have only one AC unit to replace which will usually be removed by a professional and may be disposed of in ways with low environmental impact. Choosing the other option you end up with a pile of used fans that are usually disposed of in the ordinary trash. They can have some components that are environmentally taxing. Components that could theoretically be recycled, like e.g.metal components, will not be. Plastic recycling has recently come under fire, ironically from some environmental groups, because of the high energy expense, low efficiency and water use involved. AC units on the other hand often contain refrigerants that contribute significantly to the depletion of the ozone layer and/or are considered a health hazard. Fans with plastic components may emit Plasticizers and while the refrigerant in the AC is contained in a closed system any substance emitted by a fan will be emitted directly into the airflow hitting the worker. This also goes for any other substance detrimental to health that may be contained in the paint (e.g. heavy metals), insulation material, lubricants (hydrocarbon compounds) etc. If this wouldn't make the picture complex enough, comparing the environmental footprint of the manufacture and transport of the units opens a whole new chapter, with results influenced by such diverse factors as distance to the consumer, energy use and various sources of pollution involved in the acquisition of materials and the manufacturing process. Environmental impact of said pollutants and effectiveness of countermeasures. Not to mention packaging. So the answer is: yes or no or 42. ;-) (The above is neither medical nor legal or any other advice except for maybe looking very closely at all the factors before starting to point fingers.) 71.236.23.111 (talk) 17:44, 9 May 2008 (UTC)

Are one or more ceiling fans suitable for your office? Nil Einne (talk) 17:35, 11 May 2008 (UTC)

Sensitivity of Taq polymerase to heat

My lab supervisor (I'm an MSc student and she's a PhD student) often seems obsessive about keeping Taq polymerase on ice when it's not in the freezer and minimising the time spent between. I figured that if it still functions after being subject to 95 degrees C, then it ought to be fine for a few minutes at room temperature. The way that I was told do set up a PCR reaction was to insert the DNA samples into those strips of 0.2 ml tubes, and then add the 'master-mix' containing everything else. After three rounds of contaminated PCR reactions, presumably a result of contamination of the pipette tip used to add the master-mix, I decided to avoid the possibility altogether by adding the master-mix to all empty tubes and then adding the samples to the master-mix. Now that I've imaged the products, I see that almost all reactions failed except for a few which gave really light bands and the positive controls which worked fine. It could be that there were too many primers in the outside flanking mix (I'm doing nested PCR)... could it be that the Taq was at room temperature for about 15-20 minutes? ----Seans Potato Business 16:18, 9 May 2008 (UTC)

I keep Taq on ice while its out, but I've definitely had it in the master mix at room temperature for at least 15 minutes while filling a 96 well plate. I've also always gone mastermix first, then samples, because the mastermix has always been the larger volume, for me, and to avoid a simply excessive use of pipette tips. Have you tried any positive controls during your PCR runs? Someguy1221 (talk) 17:31, 9 May 2008 (UTC)

Yeah, the postive controls worked. I'm suspecting the samples. I will try it again with a greater quantity of sample and reduced water in the master-mix. ----Seans Potato Business 19:13, 9 May 2008 (UTC)

I agree with Someguy. I usually keep it on ice at all times, as it's become an automatic habit. However, whenever I do any type of PCR reaction (whether it's mutagenesis or straight up generating amplicons for subcloning), I always make the master mix without the enzyme. I add master mix, template, then lastly the enzyme. However, that being said, if you are getting "contaminated" looking lanes, it's most likely the primers and the annealing temperature. Very rarely does DNA contamination really affect the PCR reaction, at least in my experience. Don't get me wrong, it could, and you should wear gloves and use DNase/RNase free tips and tubes, but, I've never had that sort of problem if such precautions are being taken. Have you tried a gradient PCR? Wisdom89 _{(T / ^C)} 18:09, 9 May 2008 (UTC)

Oh, and just a recommendation, regular Taq Pol is good, but I would suggest trying to use Pfu turbo or ultra. Wisdom89 _{(T / ^C)} 18:10, 9 May 2008 (UTC)

The contaminations I talked about were in the water controls so it was likely the master-mix which was contaminated. The primers have all been optimised using gradient PCR to find the right annealing temperature and number of cycles. I don't have much say in the reagents we buy, particularly since Red Taq Pol usually works just fine. I'll try using more sample as per above and see how I go. I'll be back on Tuesday to report/whine. ----Seans Potato Business 19:13, 9 May 2008 (UTC)

Like the others, I always keep Taq on ice or in an ice block when not at -20. Its good lab practice. That said, most types of Taq Pol are pretty temperature resistant. I recall a student in our lab doing some PCR then leaving his Taq on the bench overnight and doing the rest the next day. Those amplified after 16hrs at room temperature worked just as well as those done immediately. If you store your Taq is small enough aliqouts, then some raised temperatures are unlikely to have much effect. However, if you store a large volume of Taq in one tube, you should always keep it cold, because eventually the Taq will begin die. I doubt very much Taq is the issue with your PCR. Sounds like a sample problem to me. Rockpocket 01:12, 10 May 2008 (UTC)

I actually went in yesterday to try it with more sample (16 ul instead of 4). Half of the reactions worked and half didn't at all. It's nested PCR and the outside is done with a mix of primers, to amplify a number of sequences. The product is diluted 1:1000 and then 4 ul of this is used in subsequent reactions (this is methylation-specific PCR)for different genes. We used seven primers in the outside reaction and the DNA is derived from paraffin-embedded tissue. It may be that there were too many flanking primers for the original sample. This whole thing is stupid... :/ --Seans Potato Business 21:32, 11 May 2008 (UTC)

May 10

Could magnetism be said to warp space-time in a similar way to gravity?

And spare me “jokes” about luminiferous ether. It’s just that there are obvious similarities between the attractive effects of those two forces on distant objects. (Although there seems to be no repulsive action with gravity). So, can magnetism curve space and slow down time like gravity? And if not, how does a magnet ATTRACT a distant object? Myles325a (talk) 00:19, 10 May 2008 (UTC)

I don't think so. As I understand it, the electromagnetic force (of which magnetism is one aspect) works by an exchange of photons, rather than a curvature of space. However, a magnetic field does involve energy, and I believe energy does warp spacetime (E=mc² and all that), but that warping isn't what we feel as magnetic force. Physicists are working on theories that unify the various fundamental forces, so it's possible there are theories in which EM works in a similar way to gravity by curving spacetime, but in the standard theories EM is described by quantum field theory (exchange of particles) and gravity is described by general relativity (curvature of space) - trying to describe one in terms of the other is very difficult and no-one's quite managed it yet. --Tango (talk) 00:31, 10 May 2008 (UTC)

This is not such a crazy idea. See Kaluza–Klein theory. Nothing has really worked though. Quantum mechanics gets in the way. I have to run though. Sorry for the shoddy explanation. — gogobera (talk) 02:00, 10 May 2008 (UTC)

Magnetism follows an inverse cube law not an inverse square law like gravity. The electric force would therefore be more similar to gravity. Magnetism is similar to frame dragging though. Em3ryguy (talk) 12:57, 10 May 2008 (UTC)

It follows an inverse square law. It's just that every north pole is paired with a south pole and vice versa. The further you get, the proportionally closer the two poles are, and the more their effects cancel. — DanielLC 23:18, 10 May 2008 (UTC)

Its not really that simple. There are no north or south poles. A single electron moving through space produces a magnetic field that does follow an inverse square law but the field is complex. it is strongest perpendicular to the motion of the electron and nonexistant in front of and behind the electron which therefore makes it even less like gravity. If gravity and the electric force are like the stretching of space then magnetism and frame dragging are like the twisting of space. Em3ryguy (talk) 20:38, 11 May 2008 (UTC)

OP Myles325a back. Ok gogobera you SHOULD be sorry, because throwing Kaluxi—Zippi …Lapis—Laputski …Lupus—Kaluah …Whatever the hell those jokers are called—at me and then saying BYEEEE…. This is just what the other clown was doing. I would hardly be asking THIS question if I could UNDERSTAND anything on that page, would I? Now, instead of throwing someone to the most esoteric edges of physics, how about starting somewhere closer? Isn't it true that Einstein's General Theory received its first big corroboration when it was observed that light rays were deflected by the Sun's gravity? So, let me ask then, does Magnetism similarly deflect light? And it has been demonstrated that time slows down for objects in strong magnetic fields. So is anything like that observed in strong magnetic fields? And wouldn't such effects be much stronger as magnetism is so much stronger than gravity? And don't magnets just work on metals? In that case, how do those particle accelerators bend deflect those particles in a curve? See, just take it from there, and we will all be soaking up Kalitsy—CalvinKlein or whatever in no time at all. Myles325a (talk) 05:35, 12 May 2008 (UTC)

A magnetic field only has a very small effect on warping space-time. The reason is that a magnetic field contains energy. But you would need a collosal amount of energy in a small space to have a significant effect, so in practice we do not see it. Magentic fields also work on moving charges. The particles in a particle accelerator are charged and are deflected sidewasy by the magnetic field. If you have a CRT monitor or TV you can hold a magnet near the screen and see the distrotion in the picture. A magnetic field also has an effect on atoms, for example the Zeeman effect, because atoms are made from "moving" charged particles. Magentic fields of extreme levels (too strong for humans to make) will make atoms lose their spherical shape and become long and thin stretched out along the magnetic field lines. This may happen on neutron star surfaces. Graeme Bartlett (talk) 05:49, 12 May 2008 (UTC)

Dogs and cats

I sometimes see dogs and cats licking their privates. Do they ever do this to the point that they, shall we say obtain their jollies? FairmontMN (talk) 01:54, 10 May 2008 (UTC)

You may find Animal_sexual_behaviour#Autoeroticism_.28masturbation.29 interesting. --Tango (talk) 01:58, 10 May 2008 (UTC)

Conditioning

If you reward a behavior irregularly, it will condition that behavior very strongly, even when the rewards disappear. If you punish a behavior irregularly, it will tend to prevent that behavior very strongly, even when the punishments disappear. What happens if you both punish and reward a behavior, both irregularly? Will the animal shoot up a convenience store? Black Carrot (talk) 02:53, 10 May 2008 (UTC)

The idea behind this question is so good I imagine animal experiments must have been done on it, although I don’t know of any off hand. One would think it would involve how intense the drives to obtain a particular reward versus escaping a specific penalty were. In the case of things like food, where the need to obtain it can be absolutely vital, then perhaps a subject will risk much more than if the reward was less important. In human experience, some people will rob a bank at the risk of incurring long jail terms IF the potential reward is a very great deal of money. I suppose we all unconsciously work out negatives and positives for any action we are likely to take. After all, any action involves a cost in terms of effort, so everything we do is weighed up against the scenario of what would happen if we did not do it. Myles325a (talk) 03:08, 10 May 2008 (UTC)

Possibly, but the focus of my question isn't really on whether the animal will continue the behavior or not, it's what the side effects will be. See, if you do this to most humans, they'll get incredibly stressed-out and frustrated, whatever they wind up deciding to do about it. Some humans are pushed so far by conflicts like this that they become needlessly and self-destructively violent. I'm wondering whether animals have the same capacity for stress, and eventual mental illness, that people do, or if they respond to it more dispassionately, as merely a stimulus. Black Carrot (talk) 07:28, 12 May 2008 (UTC)

sauna temperature control

How does the copper tubing temperature sensor in a sauna provide feedback to the electrical control box to maintain the temperature?

Will throwing some water on the copper tubing sensor damage the control box?

Will intermittent water squirted on the copper sensor eventually damage the sensor over a period of time? Jaimegonzo (talk) 03:05, 10 May 2008 (UTC)

I can't say I know exactly what the “copper tubing temperature sensor in a sauna” is, but I imagine that you might start with Bi-metallic strip#thermostats. Maybe that's entirely not what you're wondering about, though?

About the water… it seems likely to depend on the housing for the control box -- is it water resistant? Does the thermostat rely on electrical conductance at all? I would hazard a guess that in sauna temperatures, if “throwing some water on [it]” doesn't cause problems, then “intermittent water squirted on [it] … over a period of time” won't do much either. Of course, “period of time” is a bit vague. :P  — gogobera (talk) 06:02, 10 May 2008 (UTC)

If you have a real Finnish sauna it will tolerate water, as throwing water on the stove ("kiuas") is an integral part of sauna. A Finnish kiuas that doesn't tolerate water is a nonsensical concept. Check the stove manufacturer's instructions though; other types of steam rooms from other countries might not be designed for water. If the temperature sensor is inside the stove it will be protected from water. The sensor can also be inside a thermometer on the wall, turning the heating elements on and off based on air temperature rather than stove temperature. Weregerbil (talk) 09:43, 10 May 2008 (UTC)

The copper tube is likely a thermocouple. (A friend of mine recently cut one like this on a hot tub when he assumed it was a grounding wire). -- Flyguy649 ^talk 14:31, 10 May 2008 (UTC)

In thermostats, the copper bulb is usually just a gas-filled copper bulb, connected to the thermostat by a very thin copper tube called the capillary. Within the thermostat, the pressure of the gas within the copper bulb bears on a bellows and that presses on a mechanical switch. Heat the bulb enough and the mechanical switch opens the electrical contacts, shuts the gas valve, or what-have-you, shutting off further heating until the copper bulb cools down again.

Atlant (talk) 16:00, 12 May 2008 (UTC)

Rube Goldberg pendulum

In a Rube Goldberg machine I am building, a marble hits 'something' which causes a pendulum on the top of a tower to swing back and forth a few times before it hits another marble which rolls down the tower. I'm having some trouble deciding what must be used to do what I just described. What should that 'something' I mentioned earlier be? --hello, i'm a member | talk to me! 03:29, 10 May 2008 (UTC)

In truth I have some ideas, it wouldn't hurt if I get some more. --hello, i'm a member | talk to me! 03:30, 10 May 2008 (UTC)

No ideas but what you said doesn't really make sense to me. The pendulum will swing the greatest distance on the first swing. Thus it will reach the marble on the other side of the swing on the first, not necessarily the second, third, etc. swing. Dismas|^(talk) 03:38, 10 May 2008 (UTC)

True if the pendulum swings in one plane. If the 'something' can provide an offset that causes the pendulum to oscillate in two dimensions, it can oscillate through several perioed before striking the target. Example: The pendulum bob might be held at an angle tothe vertical by a hook. the 'something' strikes the bob at an angle that dislodges it from the hook and imparts momentum that is not in the plane of the top of the pendulum. -Arch dude (talk) 04:07, 10 May 2008 (UTC)

This is what is so difficult about creating a pendulum to the marble on top: how do I create the nesscesary torque to cause the pendulum to oscillate like such (so that it eventually hits the marble)? --hello, i'm a member | talk to me! 04:21, 10 May 2008 (UTC)

Have you considered driving the pendulum by using another pendulum? Suspend two pendula from one crossbar such that both pendula have the same period of oscillation. Set one pendulum in motion. The system will be a bit 'leaky', and energy will be transferred from the moving pendulum to the stationary pendulum, driving it to oscillate. (The effect only works if both pendula have the same period.) TenOfAllTrades(talk) 06:00, 10 May 2008 (UTC)

Addendum: It's a fairly popular physics demo; here's a YouTube video of the principle in action: [13]. TenOfAllTrades(talk) 06:03, 10 May 2008 (UTC)

For another idea of how to get torque look at Driving wheel. We may have a page that describes it better, but I don't know where. Maybe s.o. else does. Otherwise just look at a model train. 71.236.23.111 (talk) 13:47, 10 May 2008 (UTC)

What is a "geographic feature"?

I've just created the article geographic feature, but I'm not sure I've defined the class entirely correctly. I took some of the material from other Wikipedia articles, and I don't know if they were correct.

For example, are countries and other administrative divisions geographic features? What about imaginary lines like borders, the Equator, etc.

I said they weren't (except for settlements), but I'm not 100% sure.

Wikipedia isn't consistent on geographic features, landforms, etc., and it isn't clear what is or is not a geographic feature. The article landform implies that landforms are not geographic features.

I couldn't find a definitive treatment of what is or is not one, so that leaves a bunch of things up in the air:

What about national parks?

Nature reserves?

What about orchards?

And then there's the sea floor, and its features, like trenches, submerged reefs, etc.

I look forward to your edits and comments.

The Transhumanist    07:28, 10 May 2008 (UTC)

Political boundaries and the like are not geographical features. That's why they are not invariably found on geographic (=physical) maps; they are found on political maps. - Nunh-huh 07:41, 10 May 2008 (UTC)

In the field of GIS, as well as cartography to some degree, a geographic feature is anything spatial you are representing on a map or in a geodatabase. The usual term is just "feature", but it's not uncommon to hear "geographic feature". I would argue that political boundaries and the like are geographic features. The field of geography includes political geography, not just physical geography. Pfly (talk) 07:59, 10 May 2008 (UTC)

I agree. It seems bizarre to me to say that political boundaries are not geographical features; maybe this is not as well-defined a concept as you seem to think. And while this is not the place to debate it, I don't see what the point is of having an article about geographical features in the first place. If they're things shown on maps, why shouldn't that article say whatever is to be said about them? --Anonymous, 08:30 UTC, edited 10:27, May 10, 2008.

Here is a great method of finding out what is a geographical feature and what isn't. Position yourself in a landscape, and point at anything that you know is there. Is it visible? If so, you've located a geographical feature. If it is a resident house, it is a very minor geographical feature, and a man-made one at that. If it is a tall mountain, it can be considered a major geographical feature. If it is a river, it is also a geographical feature, notable if it is big, not notable if not so big. What does the geography feature? It may feature a border station with customs, barracks and wire. The border control station is a feature - the political border is not. The wall of wire is a feature (major if big, minor if not), but is entirely disjoint from what is defined to be the end of a geographically defined administrative region. Hereupon lies the source of confusion with regards to wether or not a border is a geographical feature. Political boundaries are not geographical features. The wall the Israelis built just recently is, however, a geographical feature that signifies a political boundary.

I don't wish to take to the refdesk what should otherwise be on the article's talkpage, but you aired a question here, and as such it deserves my best answer. Scaller (talk) 12:19, 10 May 2008 (UTC)

Note that some non-geographic features are often included on geographic maps simply to help us locate the geographic features. State, provincial, and national boundaries and large cites might be included, for example. In the case of a map of California fault lines, it would be useful to know where Los Angeles and San Francisco are located. StuRat (talk) 20:58, 10 May 2008 (UTC)

I think what Anonymous said about the terms being only loosely defined is right. I know the word "geographic" is often used for physical things only, which would leave political boundaries out. But this usage is not the only one, nor necessary "correct". I just went and picked up a book I have called "Modeling our World: The ESRI Guide to Geodatabase Design". Here's a quote from page 25: "Geographic features are located at or near the surface of the earth. They can occur naturally (rivers, vegetation, and peaks), can be constructions (roads, pipelines, and buildings), and can be subdivisions of land (counties, land parcels, and political divisions)." Pfly (talk) 21:21, 10 May 2008 (UTC)

Another example is the USGS Geographic Names Information System. Although they mostly use just the word "feature", as in "feature name", "feature class", etc, they do use the term "geographic feature" on their FAQ page: "GNIS public Web site: Directly queries the database for official geographic feature names, their locative attributes, variant names, and other data..." The geographic features in the GNIS database all kinds of non-physical things, like counties, states, etc. Pfly (talk) 21:49, 10 May 2008 (UTC)

Screech of Chalk on a Blackboard

Has anyone done a Fourier analysis on the screeching sound which can be made by chalk or fingernails on a blackboard. Does anyone know why this sound is so unpleasant. 90.206.167.42 (talk) 10:49, 10 May 2008 (UTC)

Yes [14], and surprisingly the answer is the middle frequencies make it horrible, not the high frequencies. There is some suggestion that the sound is similar to primordial alarm calls and this is what makes us sit up and take notice. You can take part online in that sites study into what makes horrible sounds horrible. But be ready to cringe before you turn up the volume! SpinningSpark 13:20, 10 May 2008 (UTC)

And of course, I should have known, Wikipedia really does have an article on everything.SpinningSpark 13:23, 10 May 2008 (UTC)

determining the sugar content of grapes

hi, can anybody tell me how i would find the sugar content of grapes using the equipment found in a small lab? —Preceding unsigned comment added by 82.45.96.96 (talk) 10:56, 10 May 2008 (UTC)

Homework alert! Makey melly (talk) 11:10, 10 May 2008 (UTC)

Have you another looked at Sugar#measuring sugar ? SpinningSpark 14:48, 10 May 2008 (UTC)

Aircraft as flying disc

Can an aircraft able to transport a human being have the form of a flying disc? 217.168.4.133 (talk) 12:44, 10 May 2008 (UTC)

Yes it can, take a look at Avrocar, British Rail flying saucer and also Military flying saucers is interesting. There is also Lenticular Reentry Vehicle although this was not intended as human transport. SpinningSpark 13:03, 10 May 2008 (UTC)

Accelerated Thought.

The concept of gaining command over the matter, that is the entire nature through the process of accelerated thought demands attention. Is there any model which presents the operative dynamics of "accelerated thought"? —Preceding unsigned comment added by Dr.Ramakrishnan (talk • contribs) 13:22, 10 May 2008 (UTC) Dr.Ramakrishnan (talk) 13:31, 10 May 2008 (UTC)

Psychokinesis and James Randi --71.236.23.111 (talk) 14:19, 10 May 2008 (UTC)

I don't think this is about telekinesis. I think he means "How can we improve web-based education?". --Heron (talk) 14:24, 10 May 2008 (UTC)

Perhaps you are asking about the Future Shock effect, which predicted an ever-increasing rate of technological advance. IMHO this effect has failed to materialize. Can you clarify your question please ? StuRat (talk) 20:50, 10 May 2008 (UTC)

Photon energies in cosmological redshift.

Asked my physics teacher a rather obvious question after being taught about cosmological redshift the other day: If the energy of a photon is given by E=hf (planck's constant * frequency), yet the frequency decreases over time due to the expansion of the universe, then doesn't this violate conservation of energy? Won't photons from distant stars lose energy before they reach us? Where does the energy go?

I've had four thoughts about this:

1. Is planck's constant really a fundamental constant? Could it change related to the age of the universe so as to conserve photon energies?

2. Is the problem here that cosmological redshift (though not redshift due to relative motion, which I understand has energy conserved in a specific reference frame) is a prediction of general relativity, which is incompatible with quantum mechanics (which is where I assume the E=hf equation comes from)?

3. Moving on from the last point, does general relativity actually include conservation of energy? what about other conservation laws?

4. If it does, then is photon energy somehow conserved in a specific reference frame within general relativity, and the apparent loss of energy due to considering the photon from different reference frames?

Or is it something else altogether?

JMatopos (talk) 13:26, 10 May 2008 (UTC)

Photons do lose energy as the universe expands, and the simplest explanation is that it becomes potential energy of the gravitational field. But in a broader sense, energy actually isn't conserved in general relativity. There's a good (though somewhat technical) discussion here. On your four thoughts: 1. It's possible that the fundamental constants could change with time, but this has been tested and ruled out to pretty high precision. So this can't explain the loss of energy, and anyway it's predicted by general relativity without changing the constants. 2. There's nothing wrong with E = hf, but you could say the lack of gravitation in the standard model is the problem. 3&4. General relativity does predict differential energy conservation (the energy at a point equals the energy that was there before plus the energy that flowed in from elsewhere minus the energy that flowed out). But this has to be taken with a grain of salt because the "energy" here doesn't include gravitational field energy. Energy from the photons gets transferred to the gravitational field despite this law seeming to say it can't. Defining an "energy of the gravitational field" is surprisingly difficult. The page I linked says more. -- BenRG (talk) 14:46, 10 May 2008 (UTC)

Proving alcohol

Suppose, I'm filming a glass of vodka (or, generally any alcohol). How can I prove to the audience that this is vodka, not water? A litmus paper? --85.132.14.38 (talk) 13:43, 10 May 2008 (UTC)

Alcohol is flameable, right? Setting fire to it would prove its not water. Would spoil the drink though. —Preceding unsigned comment added by Makey melly (talk • contribs) 13:48, 10 May 2008 (UTC)

The simplest way isn't exactly scientific, but take a new, sealed bottle of vodka and open it in front of the camera. Any scientific test is just likely to confuse people, and could probably be faked anyway. I mean, if litmus paper worked, you might just end up trying to prove that it's real litmus paper. If you set fire to it, what's to say it's not just a liquid hydrocarbon or some other flammable substance? JMatopos (talk) 13:51, 10 May 2008 (UTC)

Well what is to prove you didn't fill a vodka bottle with water and then reseal it? Or change the label on the bottle? You could do all three; open a vodka bottle, drink some, set fire to some etc to prove beyond doubt. Or have a witness to say "yes, that is vodka". Makey melly (talk) 13:58, 10 May 2008 (UTC)

Yet in my mind, any attempt to 'prove' that it's vodka on camera would immediately raise my suspicions that it wasn't. Removing the foil seal on a new bottle of vodka is believable, natural and easy to do. Not that all these tests are a bad idea; I mean if you really wanted to 'prove' it, you could set some on fire, use a pH meter to show it's very mildly acidic and give some to a Russian who swears on his life it tastes like vodka. Seems like a lot of hassle, though. :-/ Besides, if I were watching this video, there's no way you'd prove to me 'beyond doubt' it was alcohol unless you personally gave me a sample to run through an IR spectrometer, and I figure that isn't an option. :) JMatopos (talk) 14:20, 10 May 2008 (UTC)

Having someone in the audience take a sip sounds like a best idea to me. --Tango (talk) 14:04, 10 May 2008 (UTC)

Dropping in some oil might work. It would separate out and float to the top in water. Breathalyzers use IR spectroscopy if you want something fancy. 71.236.23.111 (talk) 14:10, 10 May 2008 (UTC)

Ah, but how does he prove that the bottle of oil actually contains oil? Really, there's essentially no way to conclusively 'prove' the identity of a liquid in a videotape—virtually any conceivable test could be faked through mislabeling the reagents used, tampering with the instruments, swapping liquids during a cut between cameras, or using special effects. At some point, you have to rely on the trust of your audience.

The question here might be, "What property of the liquid is actually important?"

• To show that it's nontoxic, just drink some.
• To show that it's not straight water, use it to dissolve an ink stain. Test in advance to find an ink that will run in 40% alcohol but not (very much) in water.
• To show it's not very viscous, slosh it around a bit.

To demonstrate much more than that, you're into a difficult place. Those three tests will demonstrate that it's a drinkable liquid of comparable viscosity to water with some hydrophobic solvent properties. The things that fit those criteria (especially the "I'm willing to drink it" test) are mostly distilled beverage spirits: vodka, white rum, gin, etc. Is that sufficient for your purposes? TenOfAllTrades(talk) 16:26, 10 May 2008 (UTC)

Of course one further problem is that people could easily feel the video may be faked. For example, it wouldn't be that hard to design a video that to the untrained eye looks like a continuous shot but in fact contains different shots and you could use one drink for the non-toxic part, one drink for the ink part and one drink for the not viscious part and one final drink for where you actually perform the final test on the alcohol solution (I guess there's a point to proving something is alcohol). Of course, you could add a billowing curtain or something similar in the background to help make this more difficult and you story more plausible. It would also be a lot more difficult, even without a curtain to ensure your video fools an experts. This really depends on a lot of things. If for example you are attempting a magic trick/illusion, some of the suggestions from TOAT or others combined with your assurances to the audience that it is alcohol and no camera tricks were used may be sufficient for many viewers. Obviously not everyone is going to be satisfied, but these sort of things generally require some degree of trust from the audience anyway Nil Einne (talk) 19:58, 10 May 2008 (UTC)

The problem to me isn't that you can "prove" it, but that it's illustrated to be Vodka -- whether the demo is faked or real, for the purposes of a video it illustrates your point. If it's to record an experiment then you;d be playing it straight for teaching purposes. Otherwise, I'm thinking advertising e.g. with two glasses, one labelled (our brand), and one (other brand) for example. Viewers know it's a setup but they suspend disbelief operating through the filmic "wall". Actors don't exactly scull drinks with litmus paper in them. Otherwise like comments above, you can also discredit your demo. Btw, if using a glass of vodka with the oil drop, it seems appropriate to have a glass of water + oil to compare results. Apols if this is all too beside the point, Julia Rossi (talk) 02:24, 11 May 2008 (UTC)

Goldfish. Put goldfish in the alcohol - dead goldfish proves its not water. Of course, it could still be turpentine, so personally I would not drink any on the basis of that proof, but it is definitely not water. SpinningSpark 20:52, 11 May 2008 (UTC)

aurora borealis from space

Can the aurora borealis be seen from space? Mr Beans Backside (talk) 13:55, 10 May 2008 (UTC)

Yes; see http://en.wikipedia.org/wiki/Image:Aurora_australis_20050911.jpg and http://en.wikipedia.org/wiki/Image:Aurora_Borealis.jpg - Bear in mind that the first image is a composite and has been enhanced, though - it's not really that bright. JMatopos (talk) 14:01, 10 May 2008 (UTC)

Yes. You can even see aurora on other planets (see Aurora (astronomy)#On other planets). --Tango (talk) 14:03, 10 May 2008 (UTC)

Absolutely. Here are links to some NASA images: [15], [16]. POES (Polar Operational Environmental Satellite) observes aurorae at the north and south poles; reports are available here, among other places. TenOfAllTrades(talk) 14:09, 10 May 2008 (UTC)

Why are magpie's tails so long?

What is the explanation for the length of the magpie's tail. It must be an adaptation to something, but to what? Since both sexes have the same tail length it cannot be sexual selection. 217.42.89.22 (talk) 14:17, 10 May 2008 (UTC)

I disagree that it can't be sexual selection. Both males and females may choose mates that have a long tail, as that's a sign of good health and genes. StuRat (talk) 15:17, 10 May 2008 (UTC)

Just a thought: Long tails are good for balancing. This may be a factor here. Since there are long and short tailed species (e.g. cats, monkeys), this is not a very selective trait, but it might cause a new species to split off. 71.236.23.111 (talk) 15:19, 10 May 2008 (UTC)

Every magpie in my area has a certain green-blue tint to their tails, very much like the plumage of a pigeon (bar then the red/purple). I will therefore present the argument that it can have a sexual purpose. Scaller (talk) 17:39, 10 May 2008 (UTC)

Edit: See this -> http:/upwiki/wikipedia/commons/8/8b/Elster_wikipedia2.jpg Ah, what a beautiful picture. Serves my purpose perfectly, even. Scaller (talk) 17:41, 10 May 2008 (UTC)

See this research paper on the correlation between tail length and general health in black billed magpies. It looks like they are an honest signal on the overall health of the bird to prospective mates in boths sexes. Multiple elements of the black-billed magpie's tail correlate with variable honest information on quality in different age/sex classes. Lumos3 (talk) 22:19, 10 May 2008 (UTC)

machine that destroyeds itself

Who invented a machine that destroyed itself on purpose? Mr Beans Backside (talk) 14:44, 10 May 2008 (UTC)

The Manhattan Project. FairmontMN (talk) 14:46, 10 May 2008 (UTC)

...or for that matter any explosive, used in war or peace, like blasting caps. I suppose an artist might also create such a thing for "artistic reasons". There are also disposable machines, like a disposable camera. Finally, there is "planned obsolescence", whereby a device intentionally fails after some period of time to make you go out and buy another. StuRat (talk) 15:23, 10 May 2008 (UTC)

Possibly you are thinking of Jean Tinguely [17].--Eriastrum (talk) 19:32, 10 May 2008 (UTC)

If with "machine" you are referring to the device commonly known as homo sapiens, all you have to do is to find the name of the inventor. --Cookatoo.ergo.ZooM (talk) 23:22, 10 May 2008 (UTC)

Someone recently reported in the Risks digest that he had been awakened one night by the carbon monoxide detector in his home beeping every 30 seconds, like the way some devices signal a low battery, but in this case it was displaying Err. He located the manual on the Web and learned that the manufacturer said the device should be replaced after 7 years -- and that they enforced this by having it count 7 years and then automatically stop working and go into this error state. (Wouldn't it be fun to be the company's lawyers if someone died of CO poisoning because this happened and then there was a genuine, undetected CO emergency before they could get to a store to replace the detector?) --Anonymous, 09:00 UTC, May 11, 2008.

Outside the US, I don't see how this would be a problem. If the device started to beep once it entered into a deactivated mode, then the person would either put up with it or turn it off. If you've turned off your device or are ignoring the beeping, you can hardly complain to the company that the device didn't detect CO. Outside the US at least, this would probably be far better for the company then if their device were to be ineffective after 7 years but if the device didn't warn you of this fact Nil Einne (talk) 17:18, 11 May 2008 (UTC)

I believe the person who posted the story was in fact in the US. In any case, I think there is certainly cause for complaint if the device deactivates itself without advance warning (and I don't consider the fact that the manual mentions it to be adequate warning). Even if one accepts that the basic idea is sensible, it could have started beeping a month ahead, for example. --Anon, 04:54 UTC, May 12, 2008.

Who's to say the device wasn't still working anyway? Did someone actually test it? There's a good chance the err mode still would have gone to emergency mode if there as a leak. In any case, any beeping is liable to result in the person with the device either ignoring the beeping (rare, I doubt anyone could stand the intermitent beeping for very long if it's like a smoke alarm) or turning it off, which as I've already stated, defeats the purpose of the device. Note that it's the manufacturer is going to say "REPLACE DEVICE NOW, IT NO LONGER WORKS" the same way they say "REPLACE BATTERIES NOW, IT NO LONGER WORKS" but I'm pretty sure if you actually test most devices, they may still work provided the problem doesn't stop them from working (which is one of the reasons why they tell you it no longer works). It's generally a bad idea to actually make a device completely deactivate since there's always a risk the device may do it without giving the proper warning somehow. Note that if the person wasn't already aware they should replace the device in 7 years or it's going to start beeping, which we can assume they weren't since they didn't replace the device, then they alway likely weren't aware they should replace the device in 7 years because it's likely to be ineffective after then. It is FAR, FAR better that they were actually made aware of the fact that the device was no longer effective then it is for them to go along their merry way with a non-beeping but ineffective device. Moving the time frame forward doesn't actually achieve anything, it just makes the problem worse (besides I highly doubt the device actually started beeping at exactly 7 years). Note that if you're referring to some sort of complex electronic alarm system which warns the user until he/she turns it off 1 month before, then say more urgently 15 days before, then say every day a week before, while this may sound good in practice, in reality something like this is 1) expensive 2) far more likely to go wrong meaning that in pratices it's simply a bad idea. A simple device which goes into 'error' mode when it has a problem (like the person forgot to replace it even though he/she was supposed to) is far, far better. Let's not forget in the end the only reason anyone will ever encounter this is because they were stupid enough to not replace their device when they were supposed to.Nil Einne (talk) 16:05, 12 May 2008 (UTC)

airport security system x-rays (part I)

Are the airport security system x-rays the same in strength at those at the dentists? If so, why do the dentists run out of the room when they use the x-rays but the airport staff are next to them all day long? Mr Beans Backside (talk) 14:55, 10 May 2008 (UTC)

The X-rays at airports are contained within the box that checks your luggage by lead, whereas your dentist has no such protection from the X-rays.

Not sure about the relative strength, but the X-ray machines at the airport are shielded by those strips that fall down on either end, while the one at the dentist's office is not shielded, so that makes a big difference. StuRat (talk) 15:14, 10 May 2008 (UTC)

As a note, there are different grades of X-rays at airports. Checked baggage undergoes more intense x-raying than carry-on baggage, to the point that undeveloped film in checked baggage can end up getting fogged, whereas film in carry-on luggage will not. --98.217.8.46 (talk) 17:30, 10 May 2008 (UTC)

From what I can tell, this isn't universally true [18] Nil Einne (talk) 17:11, 11 May 2008 (UTC)

airport security system x-rays (part II)

Does the average airport security system x-ray the contents of your stomach? For example if you were hiding something illegal in there would they find it? Mr Beans Backside (talk) 14:56, 10 May 2008 (UTC)

Only if you jump on the conveyor belt along with your luggage. The thing you walk through is just a metal detector, not an X-ray machine, so it would only detect large metal objects in your stomach. StuRat (talk) 15:05, 10 May 2008 (UTC)

Oh, thank you. That clears a few things up. Mr Beans Backside (talk) 15:11, 10 May 2008 (UTC)

The metal detector would not detect anything other than metal in your stomach. You should probably check out this legal disclaimer and this medical disclaimer though, I seriously wouldn't advise trying it. It's dangerous from a legal and medical point of view. Regards, CycloneNimrod^Talk? 15:13, 10 May 2008 (UTC)

rechargeable batteries

Can i use rechargeable batteries in television remotes? The instruction manual says not to use them. What damage would it cause? Mr Beans Backside (talk) 14:58, 10 May 2008 (UTC)

Generally it is best to follow instructions for the sake of safety, but in this case i'm pretty sure the only difference would be reduced performance in terms of the life of the battery. Regards, CycloneNimrod^Talk? 15:08, 10 May 2008 (UTC)

I think it's more of an issue of the rechargeable batteries not having sufficient voltage to operate the remote, especially after they've been recharged hundreds of times (they get progressively weaker with each recharge). StuRat (talk) 15:09, 10 May 2008 (UTC)

Yes, the difference is 300mV per cell (NiMH or NiCd rechargeable against Alkaline). So assuming your remote takes two batteries it will start off 0.6V too low and then steadily deteriorate. Couple that with NiMH do not perform at their best in low drain/infrequent use applications you may find you have to take the batteries out to recharge quite often. On the other hand, disposable batteries in a TV remote would typically last a year or two, close to the shelf life of the battery. Another common problem with rechargeables in this area (though possibly not usual for TV remotes) is that any device with a low battery warning calibrated for alkalines is going to go off way too early. In short, I agree with the first answer - follow the instructions. SpinningSpark 17:08, 10 May 2008 (UTC)

Rechargeable batteries also have a very noticeable self-discharge phenomenon. That is, even without a load, they discharge themselves over a fairly short period of time (a few months). By comarison, I find that a fresh alkaline battery used in a typical infrared remote control can last several years in that very-light-duty service. This makes the alkaline battery more appealing to me.

Atlant (talk) 15:48, 12 May 2008 (UTC)

Soil moisture measurement (copied from Misc. desk)

The following is on the misc desk. Doesn't seem to work there, so I copied it here: (don't know how to move stuff)71.236.23.111 (talk) 16:40, 10 May 2008 (UTC) Which method would be more reliable to measure soil moisture: resistance or capacitance? Does different soil type contribute much to the measured resistance/capacitance? Does capacitance method still work at freezing temperatures? I'm working for a automatic watering controller using soil moisture measurements and the accuracy doesn't have to be very high, but I do want it to work reliably between different soil types. --antilivedT | C | G 07:01, 10 May 2008 (UTC)

Take a look at Frequency domain sensor which seems to give some of the answers to this and Soil moisture#Geophysical methods has links to some other probe types. SpinningSpark 17:22, 10 May 2008 (UTC)

What's the name of the fish species...

... in which the male is far tinier than the female, and ends up living parasitically inside her vagina (or fishy equivalent)?

thanks, Adambrowne666 (talk) 17:59, 10 May 2008 (UTC)

Anglerfish. --98.217.8.46 (talk) 18:04, 10 May 2008 (UTC)

You might note that although the male does become a parasite attached to the female's body, this is not inside her oviduct.--Eriastrum (talk) 19:42, 10 May 2008 (UTC)

Thanks very much - so am I conflating two species then? - is there a happy, nonparasitic fish that does live in the oviduct? Adambrowne666 (talk) 23:23, 10 May 2008 (UTC)

Ridiculous genomic databases and their stupid lies

I'm trying to get a gene sequence around its transcription start-site, so I'm using this Japanese website: http://dbtss.hgc.jp/ - I am interested in the TJP1 gene: http://ensembl.genomics.org.cn/Homo_sapiens/geneview?db=core;gene=ENSG00000104067

When, on the Japanese database page, I set the category to Ensemble(ENST), and insert the code ENSG00000104067, I get the message: Sorry, there is no hit data. Your search keyword is 'ENSG00000104067'. Is there an alternative to way? ----Seans Potato Business 20:00, 10 May 2008 (UTC)

Sorry this may be way off, but would this help? [19] —Preceding unsigned comment added by Lisa4edit (talk • contribs) 22:45, 10 May 2008 (UTC)

Thanks, Lisa. If I go to the page you linked and click on the "genomic sequence" link on the left panel, it seems to give some potentially-useful information but I'm having trouble figuring out what's being displayed. The 'flanking sequence' form fields seem to have no effect and I can't find the transcription-start site. ----Seans Potato Business 23:09, 10 May 2008 (UTC)

That would be under "Gene information" and there's a link there for the start, at least I think that's it. --Lisa4edit (talk) 23:38, 10 May 2008 (UTC)

Personally, I use this site for all of my searches. Wisdom89 _{(T / ^C)} 17:42, 11 May 2008 (UTC)

What settings do you use? I used Swiss-PROT/TrEMBL and search for TJP1 and then I get an information page, with links to other pages which include the sequence. But there's no way of telling where the transcription start site is. That ExPASy site seems to be mostly dedicated to proteins. ----Seans Potato Business 21:25, 11 May 2008 (UTC)

Why don't you export it directly from Ensembl? Find the gene you want, then choose the transcript you want (e.g. [20]). Then note where it says the transcript is found ("Chromosome 15 at location 27,778,863-27,901,974."). Since the gene is on the reverse strand, that means the beginning of the transcript is at 27,901,974bp on C15. The you can export the sequence from Ensembl. On the tab on the left, click on "Export transcript data". [21]. On this page you can choose the sequence you wish to export. If you would like to see 50bp either end of the transcriptional start you should add and subtract 50 from the start value: ("Chromosome 15, Bp 27901924, Bp 27902024") [22]. Choose your output format and, viola... you have the transcriptional start context. Rockpocket 22:21, 11 May 2008 (UTC)

If I go here: [23] to export a sequence and either a) retain the transcript value and continue (0 upstream and 0 downstream bp added) b) change to gene and enter tjp1 and continue, neither of the presented sequences begin with the start codon. Thinking more about the word 'transcript', I figure that in this context it just means the DNA sequence that is transcribed, so I'd expect a start codon at beginning of this sequence, even if not for the gene (which I suppose includes promotor info?). --Seans Potato Business 00:02, 12 May 2008 (UTC)

Transcripts don't typically begin with a start codon. They have something called 5'UTR first. If you want to start your sequence with an ATG then you want the cDNA sequence, not the transcript. Rockpocket 01:33, 12 May 2008 (UTC)

Seagulls

What was the natural habitat of the seagull before humans started interfering with the environment and encouraged them into towns and cities? Are there any seagulls left that still live as nature intended? --62.136.203.112 (talk) 23:30, 10 May 2008 (UTC)

We have an article on seagulls, you know. Anyway, as the name might suggest, they're seabirds, typically nesting on seasides. Their natural diet includes fish and other sealife, although they're opportunists and will readily exploit other available food sources. —Ilmari Karonen (talk) 23:50, 10 May 2008 (UTC)

Beat me to it. : Seagull isn't all the same. Our Gull page lists quite a few species. Some fish, some scavenge, some hunt other birds and eat eggs and some steal the catch from others. Most gulls live in costal areas. Only some species live near humans. (I guess if you eat dead tuna or dead duck it doesn't matter much if it has been in a can or trashcan before, or is "fresh" from the beach. :-) Lisa4edit (talk) 23:58, 10 May 2008 (UTC)

May 11

absolute zero

Does all motion stop at absolute zero —Preceding unsigned comment added by 74.47.169.87 (talk) 01:05, 11 May 2008 (UTC)

Take a look at Absolute zero, the first couple of lines should answer your question. --Tango (talk) 01:10, 11 May 2008 (UTC)

Expanding on this a little. All particles with mass would be stationary, but all massless particles would be traveling at the speed of light as they always do. It would be very interesting to see what a neutrino did under such conditions. GameKeeper (talk) 22:47, 12 May 2008 (UTC)

Why does this microwave have electric-plug-shaped ventilation holes?

The microwave ventilation holes at the bottom are shaped like a variety of electric plugs.

Microwaves have ventilation holes in the rear; but after closely investigating many microwaves, we noticed that there is consistently inclusion of "ventilation holes" which are exactly shaped and sized like various international electric plugs. Any ideas why this exists? We have exhausted a lot of possible explanations to no avail. There is no electric connectivity to these plug holes, they just go through the sheet metal casing. Ideas? Saket (talk) 04:47, 11 May 2008 (UTC)

Just a wild guess, but it could be because they used those holes to test whether plugs were shaped correctly during some sort of Q&A analysis. Seems a bit weird, though... Titoxd^{(?!? - cool stuff)} 04:54, 11 May 2008 (UTC)

Here's a random idea - maybe that rear panel of the microwave is used in several different models of microwaves, some of which have power inputs in that location? That could explain the various power-plug shaped holes. Although it seems odd that the female power junction is on the microwave - usually it's just on the wall outlet... it's just a wild guess. --Bmk (talk) 05:02, 11 May 2008 (UTC)

Or perhaps it's part of some metal-shaping quality control procedure in the factory? Kind of like the colored patches you can find under cardboard flaps on cereal boxes? I can't think what the purpose would be though... --Bmk (talk) 05:03, 11 May 2008 (UTC)

Is it a place to "park" the plug while in its box? Julia Rossi (talk) 05:24, 11 May 2008 (UTC)

We thought of all of these possibilities. We should mention that one of our microwaves (not the one in the photo) only has european-style holes in the ventilation panel EVEN THOUGH it is an American model with a US-style plug. This seems to invalidate many of the above possibilities... Saket (talk) 05:31, 11 May 2008 (UTC)

The one not-yet-mentioned possibility is that this particular model was designed to konfuze WP Reference Desk editors. :) -- Fullstop (talk) 05:35, 11 May 2008 (UTC)

Aww, my microwave is boring, no plug holes. How about this: a built-in template for the workers to figure out what country the microwave is going to, so they don't get them mixed up in the factory. The workers don't have to be able to read or anything, it's all done with diagrams. For the exception above, that factory is just wiring North America and Europe-style plugs, so they only need one template to check against. Franamax (talk) 06:43, 11 May 2008 (UTC)

By my count, there are 9 hole patterns in that pic. Thats covers pretty much every type, not just the North Am + European ones. -- Fullstop (talk) 07:01, 11 May 2008 (UTC)

Yes, that one came from a factory supplying the whole world. The other one mentioned above at 05:31 is from a factory with less scope. Franamax (talk) 07:04, 11 May 2008 (UTC)

I think it's for packaging purposes; when the microwave was packaged, the plug was perhaps inserted into the relevant holes and excess cable bunched up with a wire tie thing. ----Seans Potato Business 07:51, 11 May 2008 (UTC)

Packaging maybe not, but assembly more likely. You could feed the terminal end of a pre-assembled cord through a hole in the panel and then store the plug. That way it doesn't dangle around while you move that sub-assembly to the next step. Process wise feeding the cord through is a process (grip, position, feed, pull) that is quite different from fixing the cord and putting the back panel on (grip, position, fix screws). Either a human or a machine would have to change tools, so it would make sense to do it at 2 separate stations. But who knows. Lisa4edit (talk) 09:15, 11 May 2008 (UTC)

I vote for packaging, I have unpacked items myself that had the plug stored in this way. SpinningSpark 09:47, 11 May 2008 (UTC)

See reference at 5:31 to a model of a microwave oven with an American plug and only European holes on the back panel. That only makes sense for assembly if the plug was replaced after assembly (say, as part of the importing process), and makes even less sense for packaging. Or did they just screw up with that model? 128.12.187.10 (talk) 11:34, 11 May 2008 (UTC)

Well it could still make sense for packaging. UK plugs are horrible blocky things with pins sticking out sideways causing problems getting it into the box. You need somewhere for the pins to go. US plugs on the other hand are slimmer and with the pins pointing along the cable axis. Coiling the cable and tieing may be sufficient. Also (not sure if this point applies), are not some US power cords detachable like IEC power cords are? If it is not captive then it is not such a problem packing, it is put in the box after the main item. SpinningSpark 12:14, 11 May 2008 (UTC)

No reason you can't have an IEC style UK plug. Computers, rice cookers, kettles in the UK and/or Malaysia use them Nil Einne (talk) 16:58, 11 May 2008 (UTC)

Yes, but that was not the point. The question is, does the US microwave mentioned above have one? I suspect the answer is probably no as it is uncommon to find detachable cords on power devices as it is cheaper for the manufacturer to make the cord captive (kettles are a special case because of the need to pour). SpinningSpark 17:40, 11 May 2008 (UTC)

No it doesn't.128.12.190.172 (talk) 22:12, 11 May 2008 (UTC)

But my point was, if the US plug was detachable, then surely the UK plug would be as well? Why make an IEC style detachable plug and then make the UK one fixed and the US one detachable? And if the US/UK one was detachable, then the issue of it not being a problem packing because it's put into the box after the main item equally applies. So it just seems to me it's irrelevant whether or not it was detachable as to an explaination for why it owuld have holes for a UK plug but not a US plug Nil Einne (talk) 15:50, 12 May 2008 (UTC)

Concentrate Juice vs Non-Concentrate

<moved from miscellaneous desk>
How much of a difference is there between fruit juices that are "made from concentrate" and those that are "not made from concentrate"? Suppose if Juice A is made from concentrate with just filtered water and juice concentrate as its ingredient and Juice B is not made from concentrate (like Tropicana), how much of a nutrient difference is there? Is the juice not made from concentrate "healthier" for you? Acceptable (talk) 21:31, 10 May 2008 (UTC)

Well the effective food miles of from concentrate is way lower so you really shouldn't touch the "not from concentrate" stuff. I have tried blind taste off from concentrate with bits versus not from concentrate and they are indistinguishable but real freshly squeezed of course is quite different. --BozMo talk 08:30, 11 May 2008 (UTC)

I guess you've seen our articles food miles, concentrate and juice? In the last, sugar's a health issue. Julia Rossi (talk) 10:10, 11 May 2008 (UTC)

I don't understand why "from concentrate" juice should have fewer food miles - could you explain Boz? -Bmk (talk) 15:34, 11 May 2008 (UTC)

While the concentrate may have travelled just as far, the water has hardly gone anywhere. --Tango (talk) 16:20, 11 May 2008 (UTC)

Right so the "litre-kilometres travelled" per litre drunk is less. --BozMo talk 20:33, 11 May 2008 (UTC)

BozMo's point that fresh-squeezed juice tastes different is due, I believe, to the pasteurization process, which heats the juice to the point where some chemicals are altered, resulting in a flavor change. In my experience, juices that have been flash pasteurized more closely approximate the flavor of fresh-squeezed juices.

Assuming that both the concentrate and not-from-concentrate juices have been equally pasteurized, I would say there are minor differences, but they would be indistinguishable. When boiling away the water in a vaccuum at low temperature, other volatiles in addition to water can get boiled away too. This may result in a slightly different chemistry between the concentrate and original, which may result in a detectable difference in aroma if not flavor. =Axlq 06:07, 12 May 2008 (UTC)

Platinum

<moved from miscellaneous desk>
I have a piece of what apears to be platinum that was melted down in a crucible and was wondering how do I go about finding out what it is?--66.191.106.19 (talk) 08:31, 11 May 2008 (UTC) Probably just as simple as taking it to a jeweler, if that doesn't work, ask said jeweler for any contacts of his. —Preceding unsigned comment added by 121.222.146.142 (talk) 10:32, 11 May 2008 (UTC)

Well...there is a test, which is that if it isn't attacked by either concentrated nitric acid or hydrochloric acid, but it does react with the combination of the two (aqua regia), then it's probably platinum. But I would take it to a jeweler - if you do it yourself you run the risk of damaging your sample or yourself. --Bmk (talk) 18:18, 11 May 2008 (UTC)

One way is determine the density. If it looks pure with no bubbles or inclusions, weigh it, and find the volume by water displacement. Platinum is one of the densest metals, so it should be heavy, but there are a few other dense silvery metals too, such as osmium or iridium. A metalurgist may have equipment such as xrays that could determine what it is too. Graeme Bartlett (talk) 21:29, 11 May 2008 (UTC)

Density may not work particularly well if the sample isn't pure. If it's alloyed with something else, the density could be significantly different from the density you would find in a textbook for pure platinum.. --Tango (talk) 00:17, 12 May 2008 (UTC)

Oh, and platium is worth a lot (US$2000/once) so get it to a jeweler.118.90.102.125 (talk) 12:33, 13 May 2008 (UTC)

crystals

where and when were crystals discovered —Preceding unsigned comment added by 76.29.128.29 (talk) 13:34, 11 May 2008 (UTC)

I imagine they've been known about since pre-historic times. --Tango (talk) 16:17, 11 May 2008 (UTC)

According to our article on crystals, they were indeed known to (if not understood by) the ancient Greeks, and probably most other ancient civilizations as well. Nicolas Steno, a Danish geologist, is sometimes credited with beginning the modern science of crystallography and minerology when he observed in 1669 that any sample of a single crystalline substance has the same angles between faces. --Bmk (talk) 18:39, 11 May 2008 (UTC)

Nutrient needs of brain

Are there any nutrients which have been shown to be essential or particularly beneficial to the brain, more than to the rest of the body? Also, how many calories(assuming average calorie intake, which I think is 2000 daily) does the brain alone require every day? Hence, what would be the daily nutritional needs of the proverbial "brain in a vat" which maintains mental functions without a body? —Preceding unsigned comment added by 69.224.182.55 (talk) 14:58, 11 May 2008 (UTC)

You average calorie intake is unlikely to have much effect on the energy requirements of your brain. (Your average calorie intake doesn't have much effect on the energy requirements of your body either although the heavier you get, the more energy your body needs to move you around) Nil Einne (talk) 16:53, 11 May 2008 (UTC)

I think the question was what percentage of the daily calorific intake is used by the brain, not how does calorific intake affect what the brain uses. --Tango (talk) 19:01, 11 May 2008 (UTC)

The brain has an almost absolute requirement for glucose. It does not metabolize fatty acids. However, it will use ketone bodies for energy if glucose is not in abundance. Wisdom89 _{(T / ^C)} 17:36, 11 May 2008 (UTC)

ionizing radiation

What is the simplest definition of ionizing radiation? Mr Beans Backside (talk) 17:30, 11 May 2008 (UTC)

Electromagnetic radiation (high energy EM waves/particles) or radioactive particles (beta particles, neutrinos, alpha particles etc..etc..) that strip electrons and produces ions of neutral elements. Wisdom89 _{(T / ^C)} 17:33, 11 May 2008 (UTC)

"Any radiation capable of displacing electrons from atoms or molecules, thereby producing ions" - from http://dels.nas.edu/potassium_iodide/glossary.html Regards, CycloneNimrod^Talk? 17:45, 11 May 2008 (UTC)

Dark matter

Why doesn't dark matter reflect light? I was wondering because of the recent story reporting the discovery of a dark planet. I seemed to have forgotten what it was exactly that was discovered, and can't find the story now. Maybe I dreamed it! But I thought it said something about gravitational lensing. Any help, or am I losing it? Mr Beans Backside (talk) 17:31, 11 May 2008 (UTC)

You're not losing it. Dark matter (see that article, it should answer your questions) either does not emit electromagnetic radiation or doesn't emit enough of it to be detected directly. Instead, we detect it by it's gravitational effects on matter. Not entirely sure why it doesn't reflect light, though.. Regards, CycloneNimrod^Talk? 17:43, 11 May 2008 (UTC)

Light is an electromagnetic wave - only charged bodies interact with it. So (presumably uncharged, certainly the upper limits on its charge are very small) dark matter particles don't interact with it. The electrons in your body are what reflect light - a big brick o' neutrons would reflect very little light indeed (only through virtual particles. WilyD 17:46, 11 May 2008 (UTC)

How do we know the upper limits on the charge are small? Wouldn't our observations just tell us the upper limits on the net charge? Objects with a zero net charge can still reflect light by being made up of equal numbers of positive and negative charges (eg. atoms). --Tango (talk) 18:59, 11 May 2008 (UTC)

That's correct. But we can put small upper limits on the charge of each particle. Your body is neutral because it contains equal numbers of electrons and protons, but the negative electrons still reflect light. So DM can't be made of negative and positive particles lumped together like 'normal' (Baryonic) matter is, or we'd see it. Olaf Davis | Talk 20:41, 11 May 2008 (UTC)

If the charge is not small, then dark matter particles would be created quite often in particle accelerator experiments, where it would show up as missing mass and momentum. Null results from such experiments limit the charge of any unknown particle (this depends on the mass of the unknown particle). This method does not depend on whether or not the particles actually exist.

There are other ways to contrain the charge of dark matter particles. E.g. one can exploit the fact that the millicharged DM background would become polarized in an electric field. You can try to measure the electric field inside a cavity of a conductor when there is a strong elecric field outside, see here. Other possible experiments are discussed here and here. Count Iblis (talk) 21:02, 11 May 2008 (UTC)

(ec)First of all, no one has proved dark matter exists. Astrophysicists would like it to exist because if it does not there are severe theoretical difficulties with our theories of the universe. There are many ideas of what dark matter might be and why we cannot see it, as Cyclonenim said, look at the article for the various possibilities. I think the claimed discovery you are referring to is a galaxy rather than a planet, also mentioned in the article. SpinningSpark 17:50, 11 May 2008 (UTC)

I concur with Spinningspark - I'm not sure about the "dark planet" thing, but I guarantee it wasn't a planet made of dark matter. At this point dark matter is just a hypothesized (but as of yet not directly observed) substance introduced to explain gravitational anomalies in the universe. Some physicists have proposed a model of what dark matter might be like if we ever detect it - it's known as a WIMP. Basically, WIMPs are particles that interact only via the gravitational force and weak nuclear force, like neutrinos. So if dark matter exists and is made up of something like WIMPs, that would mean that they would not emit or absorbe any electromagnetic radiation (light), and would be literally "dark". But again, it's all highly hypothetical at this point. --Bmk (talk) 18:45, 11 May 2008 (UTC)

These are both realistically misrepresentations. Science never proves anything exists - The level of confidence among astronomers that is such that working with ~100 astronomers, I don't know any who take seriously an alternative explanation. But there's no evidence of "dark matter planets" - "dark planet" would presumably mean a planet that's just too dim - a planet discovered through radial velocities or gravitational lensing probably won't be visible, nor would a free-floating planet (you might call it a planemo if you want to avoid the ire of certain astronomers, who'll remain nameless). Dark matter might form compact objects, but it seems unlikely - all the observations we have of it suggest its not very collisional - see bullet cluster, for instance, and maybe read MACHOs. WilyD 18:56, 11 May 2008 (UTC)

According to the article 'bullet cluster', stars arent very collisional either-"The major components of the cluster pair, stars, gas and the putative dark matter, behave differently during collision, allowing them to be studied separately. The stars of the galaxies, observable in visible light, were not greatly affected by the collision, and most passed right through, gravitationally slowed but not otherwise altered". Em3ryguy (talk) 21:07, 11 May 2008 (UTC)

That's right. There are actually models (admittedly bit far out) that predict DM analogous to ordinary matter. So-called [mirror matter] is an example and this article actually suggests that some close in extrasolar planets might actually be made of this invisible mirror matter :). See also here. Count Iblis (talk) 21:16, 11 May 2008 (UTC)

math and physical difference in mental ability

is there any conclusive data that asain people are better at math because of a physical difference in there brain or learning ability that gives them an advantage over other races? —Preceding unsigned comment added by 206.75.0.220 (talk) 17:54, 11 May 2008 (UTC)

Not all Asian individuals are as intelligent as you imply. However, when they are, it tends to be as a result of how they were schooled rather than a physical difference. Regards, CycloneNimrod^Talk? 18:26, 11 May 2008 (UTC)

If you are pondering why a lot of good engineering is presented by Asian tigerstates, Japan and Asia in general, the answer should not lie quite in the brain. The dominant religion, for instance, is one which stresses subordination to mentors and the importance of learning skills; to strive for a common goal. Now, that's merely the gist of things. Greater political factors have a lot to do with how industry in Asia has gone well after the second world war. Confucianism, Japan and Four Asian Tigers should give you a quick introduction, while better, Asian-wide topics can be reached from these. Merely google something like "industry in asia", or "asian economy". Does this help you? I hope my interpretation was correct, or at least not completely wrong. Scaller (talk) 18:34, 11 May 2008 (UTC)

I may be heading down a slippery slope here, but see Race and intelligence. SamuelRiv (talk) 19:57, 12 May 2008 (UTC)

Concentrated Blackcurrant Juice

What would be the effects of "hypothetical person A" drinking too much concentrated Blackcurrant Juice? Would it be enough to kill them? ps this is not medical its science in hypothetical terms. Mr Beans Backside (talk) 18:07, 11 May 2008 (UTC)

It is hypothethically possible to drink enough of virtually any liquid to kill yourself, but the amounts are really quite excessive. See: water intoxication. Dragons flight (talk) 18:41, 11 May 2008 (UTC)

Do you mean without diluting it? I'm not sure it's strong enough to harm you, but if it is, it could dehydrate you and cause damage to the liver and kidneys, I expect. I'm just guessing, really, though. I expect someone here knows better than I do. --Tango (talk) 18:54, 11 May 2008 (UTC)

Why was I born to my parents in my town at a specific time?

moved to [[24]]

Taste of apple seeds

I've read that apple seeds contain cyanohydrins (see hydrogen cyanide) and that cyanide has a "faint bitter almond-like odor". I've also noticed that apple seeds (at least for Cripps Pink and Golden Delicious and some other varieties I've tried) taste quite strongly of almond. Is this a coincidence, or am I indeed tasting the hydrogen cyanide present in the apple seeds? Eric. 81.157.250.169 (talk) 20:15, 11 May 2008 (UTC)

Well cyanohydrins are produced by reaction with HCN. Also, the almond taste of such seeds is mostly subjective. For instance, I personally don't taste it. Cyanohydrins are derived from ketones, for instance, which can have a fruity/distinctive smell. This could possibly explain the taste. Wisdom89 _{(T / ^C)} 20:48, 11 May 2008 (UTC)

I thought that it was really bad for you to eat apple seeds? Never really thought to question it but I was told as a child that they were toxic and were always to be discarded... --Kurt Shaped Box (talk) 21:37, 11 May 2008 (UTC)

See Archive May 1 "Cyanide and almonds" same goes for apple seeds Lisa4edit (talk) 00:13, 12 May 2008 (UTC)

Ah, interesting. So the taste is due to benzaldehyde? I see. Eric 81.157.250.169 (talk) 12:52, 12 May 2008 (UTC)

I've had around 20 or so apple seeds in one sitting before (chewed, not swallowed whole), so either they're almost harmless or I'm working on being the next Rasputin. Eric 81.157.250.169 (talk) 12:52, 12 May 2008 (UTC)

Many plants and seeds contain glycosides in varying low does concentrations. Among them such healthy foods as spinach. One of those glycosides is amygdalin which is contained in the pits of stone-fruit and apple seeds. If you add enzymes to amygdalin HCN is split off. HCN is toxic in very low concentrations to plants and animals. Plants contain both the amygdalin and the enzyme, but they are stored separately from each other. When you chew the seed, the enzyme gets mixed with the amygdalin and reacts. Some amygdalin passes through to your digestive tract and reacts with enzymes there. HCN is also further broken down by enzymes into HCNO which is not toxic. But the body only has a limited capacity for that to happen. Some bacteria also process the HCN into HCNO. Individual apple seed have less bulk than bitter almond. I've dug around for concentrations and found one source [25] that states 690-790 ppm (mg/kg). Based on this study another source [26] created this scenario The ADI (acceptable daily intake) described for cyanide has been reported at 0.05 mg/kg. If all amygdalin would be converted into cyanide this would corresponds to an ADI for amygdalin of 0.85 mg/kg. For a person of 75 kg this equals an acceptable intake of amygdalin of 63 mg daily. Assuming that all amygdalin from apple seeds is extracted from the seeds (which will be an overestimation), this equals the consumption of 80 g of apple seeds. Before you start upping your daily consumption to that amount you should consider that the ADI includes intake from all sources. (lima beans, bamboo shoots, juice, cider, and even corn to name just a few). It also presumes that you are in perfect health otherwise and weigh 75 kgs. Lisa4edit (talk) 19:52, 12 May 2008 (UTC)

Thanks for the thorough research & information -- I considered asking for specific concentration information but thought that was a bit much to hope for. Fortunately 80 g of apple seeds is well beyond my appetite for them. I found your first reference helpful for putting such information in context. Eric 81.157.250.169 (talk) 04:15, 13 May 2008 (UTC)

Aluminum chloride

Is aluminum chloride the same as aluminum zirconium tetrachlorohydrez glycine? Mr Beans Backside (talk) 20:41, 11 May 2008 (UTC)

Take a look at aluminium chloride and zirconium + glycine and tell us Nil Einne (talk) 20:50, 11 May 2008 (UTC)

Hardness of water

Is the hardness of water a consequence of pipe scaling? What technology and major steps are involved in the purification of drinking water and the treatment of waste water? Mr Beans Backside (talk) 20:43, 11 May 2008 (UTC)

To the first one, er no... As Hard water and Fouling may tell you, it's more likely to be the reverse. For the second one, is there anything in particular that Water treatment doesn't tell you? Nil Einne (talk) 20:56, 11 May 2008 (UTC)

Pressure and altitude

Could someone explain why pressure decreases but temperature varies as altitude increases? Mr Beans Backside (talk) 20:44, 11 May 2008 (UTC)

Erm, well as a general rule, temperature decreases with altitude so I'm not entirely sure where you got this impression from. Regards, CycloneNimrod^Talk? 21:02, 11 May 2008 (UTC)

Once you get high enough, that's not the case any more. The Thermosphere can get extremely hot, for example. However, since it's so thin, the actual amount of thermal energy is very low, so it wouldn't feel warm. --Tango (talk) 21:53, 11 May 2008 (UTC)

You should look at atmospheric pressure for pressure (obviously) and lapse rate for temperature. SpinningSpark 21:21, 11 May 2008 (UTC)

Different sources of heat become significant at different altitudes, which is what causes the variation in temperature, rather than just a gradual cooling as you might expect. Earth's atmosphere will tell you more. --Tango (talk) 21:53, 11 May 2008 (UTC)

Energy sources

I know there's electric, solar, wind, hydroelectric, geothermal, coal, oil, natural gas, and nuclear. What other energy source are there, or are those them all? Mr Beans Backside (talk) 20:48, 11 May 2008 (UTC)

Biomass? Fribbler (talk) 20:57, 11 May 2008 (UTC)

No, that is not all. There is tide and wave power for a start. There are many more, take a look at List of energy topicsSpinningSpark 21:00, 11 May 2008 (UTC)

(EC) There are lots and lots of potential energy sources. Energy development has most/all of the ones currently of most interest. List of energy resources has a lot of other things including means of energy storage and energy conservation Nil Einne (talk) 21:01, 11 May 2008 (UTC)

What about potential energy? User:Yetmotega/1 Yetmotega (talk) 22:00, 11 May 2008 (UTC)

Potential energy is energy stored in a field. So you need to specify which force of nature we are discussing know the energy type, eg electric, magnetic, gravitational etc. SpinningSpark 22:30, 11 May 2008 (UTC)

E=mc² so basically everything is an energy source. GameKeeper (talk) 22:52, 12 May 2008 (UTC)

Which genes flank TJP1

How do I find out which genes flank TJP1 in humans? I figure one of the many genomic databases would be able to help but they're terribly complicated and intimidating. ----Seans Potato Business 21:04, 11 May 2008 (UTC)

On the link you provided, scroll down to the section Genomic context. This will tell you the chromosome the gene is present on and it's location. By searching the position before it or after it should give you your answer. Regards, CycloneNimrod^Talk? 21:11, 11 May 2008 (UTC)

Its actually a bit complicated this one. However, 5' of TJP1 appears to be necdin-like 2, while 3' is CHRNA7-FAM7A fusion isoform 1 (which is a very odd locus). There may be other genes in between, but they have not been characterized. Rockpocket 21:53, 11 May 2008 (UTC)

How did you get those? ----Seans Potato Business 21:59, 11 May 2008 (UTC)

Okay, this isn't working. I'd like to know in which order the genes TJP1, NDNL2, GREM1, SLC12A6 and SPRED1 occur. I know they're in the same region, but I want to determine if there are any genes between them and in what order the occur. If I search for each gene I get:

ndnl2 15q13.1

slc12a6 15q13-15

tjp1 15q13

grem1 15q13-15

spred1 15q14

Yet none of these shows up on the 'genomic context' diagram of any of the others. How can I interpret this mess? Does SPRED1 exist on an exon inside both GREM1 and SLC12A6 which both exist in exons of each other? I suppose one may be on the antisense strand, but there's going to be overlap somewhere here. ----Seans Potato Business 21:55, 11 May 2008 (UTC)

According to Ensembl (by searching for each gene on the human genome):

• Ndnl2.. can be found on Chromosome 15 at location 27,347,645 - 27,349,325 and is anti-sense.
• Tjp1.... can be found on Chromosome 15 at location 27,778,863 - 27,901,998 and is anti-sense.
• Grem1.. can be found on Chromosome 15 at location 30,797,497 - 30,814,158 and is sense.
• Slc12a6 can be found on Chromosome 15 at location 32,309,489 - 32,417,557 and is anti-sense.
• Spred1. can be found on Chromosome 15 at location 36,331,808 - 36,433,526 and is sense.

Are there intervening genes? Yes in all cases, except between Ndn12 and Tjp1. Rockpocket 22:35, 11 May 2008 (UTC)

Okay, this is really helpful of you. Thanks. However, now I have a conflict; SPRED1, according to this is at 15q14 while GREM1 according to this is at 15q13-15. If 15q13-15 means 15q13 to 15q15, then why do those numbers you (kindly) provided not overlap? And how did you find out whether they were sense or anti-sense? --Seans Potato Business 22:48, 11 May 2008 (UTC)

The "q" refers to chromosome regions while the numbers (13-15) refer to cytogenetic bands identified by staining. That nomenclature is an old skool way of positioning genes on chromosomes and is not particularly accurate. Now we have a fully sequenced genome we can precisely identify exact positions of genes. In this case 15q13-15 means that Grem1 resides somewhere within bands 13-15, rather than meaning it spans that huge length. I used Ensembl to find the info, and identified the strand from that. For example, have a look at the diagram on the TJP1 page, under the "transcripts" sub-section. Find the thick blue line that says "DNA (contigs)". Now any gene identified above that line is on the forward strand (sense orientation) and any genes under that line is on the reverse strand (anti-sense). TJP1 is directly underneath the line, therefore it is anti-sense.

If you don't wish to use Ensembl, the NCBI site you were using gives the same info. On the Spred1 page, on the right hand side of the "genomic context" section there is a link to "See SPRED1 in MapViewer" If you follow that link [27], you can see that the Spred1 gene is located on the right hand side vertical line spanning roughly the same distance I provided (36331k to 36433k). If you want exact values, you can always zoom in by clicking on the gene. Note also the little black arrow beside the Spred1 gene name. The arrow points downwards, indicating the gene is on the sense strand. If it was to point upwards, you would know your gene of interest was anti-sense. Rockpocket 01:22, 12 May 2008 (UTC)

How does something vibrate in 10 dimensions?

An article I read awhile back about an atom's parts said that superstrings are the smallest part of the atom. It went on to say it vibrates in 10 dimensions.

Huh? How do they determine this? If you cant actually see it with a microscope, how can you determine with fancy math that something can exist in 6 dimensions we cant even imagine?--Sam Science (talk) 21:40, 11 May 2008 (UTC)

There is very little experimental evidence for superstring theory at this point, as far as I know. It's mostly maths and mathematicians can imagine all sorts of things that don't fit in our everyday understanding of the world. If you can work out the maths of something vibrating in 3D, you can work it out for something vibrating in 10D, the maths is pretty much the same, just with different numbers. It turns out that if you do things in just the right way (that's the hard part) those vibrating strings happen to interact with each other in the same way we observe elementary particles interacting. --Tango (talk) 21:47, 11 May 2008 (UTC)

I think you're a tad confused with what you read in that article. String theory is theoretical, as the name suggests and it is hoped it'll fill in a lot of gaps in physics, but it certainly isn't proven. Also the theories state that the strings vibrate in one dimension, not ten. You're quite right in thinking we can't see them with microscopes, we can't even see atoms themselves properly. As I said, it is not a proven theory, simply something that is being made up to fix gaps in the theories of physics. Regards, CycloneNimrod^Talk? 21:50, 11 May 2008 (UTC)

"Proven theory" is a contradiction in terms. Theories can't be proven, you can just gather evidence for them until it becomes very unlikely that they're wrong. Proof is a mathematical concept, you prove theorems, not theories. And what do you mean by them vibrating in one dimension? They are one dimensional objects vibrating in 10 dimensional space. --Tango (talk) 21:55, 11 May 2008 (UTC)

Physicists use mathematics to describe the universe, using vectors and matrixes to describe space. In simple models these are 4-element matrixes - 3 space-like and 1 time-like (see Minkowski space). It may be surprising, but this often makes the mathematics a lot simpler - for example, electricity and magnetism join messily (using several equations) using 3 space dimensions and keeping time separate (using maxwells equations), but join simply (using one equation) when using the 4 element vectors (using the electromagnetic tensor). Maxwell's equations and the electromagnetic tensor are equivalent - the only difference is how they're expressed.

Theoretical physicists find that their theories work when these vectors and matrixes have more than 4-elements - generally the theories use either 10 or 11 elements in their vectors and matrixes, and this corresponds to 10 or 11 dimensions. The reason why a new theory is needed is to express the four fundamental forces and lots of fundamental constants more simply. This is cutting-edge physics - a lot of the work on these theories is currently working out how to detect how this is different from the standard model. --h2g2bob (talk) 22:43, 11 May 2008 (UTC)

The various string theories only work at all in a particular number of dimensions (10, 11, 12 or 26 depending on which variant you're talking about). I don't know what goes wrong otherwise, but it might be a violation of unitarity (meaning, basically, that the theory predicts events happening with a probability greater than one). So if you want to use string theory as a physical theory, you're committed to having those extra dimensions. There's no other reason to think they exist. -- BenRG (talk) 01:17, 12 May 2008 (UTC)

One of the things that fails is that photons are not massless. More generally, there is a mapping problem. If you assume that all particles are associated with vibrational string modes and that there are X independent classical properties of particles (e.g. charge, spin, color, etc.) then you require at least X extra dimensions to map those properties onto geometric structures. (You can get away with less than X if you assume that they aren't ultimately independent.) Dragons flight (talk) 05:43, 12 May 2008 (UTC)

Dogs in heat

How many times should a female dog mate while shes in heat to ensure she becomes pregnant? And at what point during her being cycle should she mate for the most success? Mr Beans Backside (talk) 22:07, 11 May 2008 (UTC)

• For the most success she should mate each day during her 3 most fertile days.Mieciu K (talk) 21:27, 12 May 2008 (UTC)

Chemists: solvents for spot cleaning carpet?

I have some dried emulsion paint (might be called latex paint in the US?) I want to remove from a carpet.

I do not know what the carpet is made of, but I do not think it is wool. Many capets in the UK seem to be made of polypropylene or perhaps nylon.

My questions are - 1) as an alternative to the below, would white spirit, turpentine substitute, or even WD-40 be just as good please? And 2) would Nail Polish Remover dissolve the carpet? I.E. It dissolves the paint, it does not dissolve the carpet!

Rug Doctor "Traffic Lane Cleaner" (carpet pre-washing spray): active ingrediant Ethylene Glycol Monobutyl Ether - has worked well removing dried chewing gum and unknown stains from a carpet. Have not tried it on paint yet.

Nail Polish Remover: Acetone, Glycerine, Cetylacetate, Oleyl Acetate, Acetylated Lanolin Alcohol, Polysorbate 80. Highly recommended for carpet paint removal here http://www.thriftyfun.com/tf991362.tip.html

Stardrops cleaner: Sodium dodecylbenzene sulphonate, Alkyl ether sulphate, Alcohols C9-11, ethoxylated Bitrex (Denatonium benzoate) solution, Bronopol (2-bromo-2-nitropropane-1,3-diol).

Cheaper and to-hand alternatives: white spirit, WD-40.

Thanks. 80.2.195.209 (talk) 22:54, 11 May 2008 (UTC)

Whatever you do, do a "spot-test" first on an inconspicuous area of the carpet (e.g. part that's always covered). --Seans Potato Business 22:58, 11 May 2008 (UTC)

I would guess that white spirit will work (it will almost certainly remove the paint, I'm just guessing it won't ruin your carpet). As Seans says, you should definitely test it somewhere out of the way first. If it were me, I would just have a go with white spirit somewhere hidden and see what happens, but you may want to wait for more informed answers (I've never been one to follow instructions!). --Tango (talk) 23:01, 11 May 2008 (UTC)

Not based on any chemical analysis, but merely OR. Undiluted "Pine Sol" and elbow grease along with a pile of paper towels worked well. A generic "compare to" product didn't. Since you aren't in the US I don't know if you can get it and whether you get the same stuff under that label. We're out and I threw out the old bottle, so I can't tell you the composition. Trying in a hidden area is always a good idea. Lisa4edit (talk) 23:46, 11 May 2008 (UTC)

Emission line

Where can learn more about the spectral lines of substances? In particular, there is apparently an argon emission line at 750.38 nm and I'd like to know if it belongs to the argon atom or an ion and what the cross section for its activation is as a function of incident electron energy. I imagine there are reference works for this kind of data and would be glad for directions. Thanks. —Bromskloss (talk) 23:09, 11 May 2008 (UTC)

Atomic spectral line has an explanation and a link at the bottom that should help answer your question. --Lisa4edit (talk) 23:33, 11 May 2008 (UTC)

Thanks, but I'm not looking for an explanation of how it works. What I need is a data collection where I could look up argon, see a list of all its lines and preferably the corresponding cross section for electron-argon collisions that would result in emission in this line. —Bromskloss (talk) 23:46, 11 May 2008 (UTC)

I recommend the CRC Handbook of Physics and Chemistry at http://www.hbcpnetbase.com/. It's quite comprehensive. The data you're looking for will probably be found in Section 10: Atomic, Molecular, and Optical Physics. --Bmk (talk) 02:08, 12 May 2008 (UTC)

Thanks for the tip. That one could be useful for the future. However, I look at the table Line Spectra of the Elements, but there is no mention of an argon line at 750.38 nm. :-( (And no cross secions, as far as I can see.) —Bromskloss (talk) 08:54, 12 May 2008 (UTC)

No, the Argon I line at 750.3 nm is listed there!! I must defend the honor of the CRC handbook!! :) The lines are listed in Angstroms, rather than nm, so you can find it at 7503.8 A. But no, I'm not sure where you can find the crossection. --Bmk (talk) 14:05, 12 May 2008 (UTC)

Ah, I didn't see that! It's a good thing for me you came to defend it. :-) —Bromskloss (talk) 09:11, 13 May 2008 (UTC)

A quick google search reveals that it is from ArI - ie non ionized. It is one of the main emmission lines. But this is not a systematic method! Graeme Bartlett (talk) 03:56, 12 May 2008 (UTC)

May 12

Guinea Pig head bump

I have two guinea pigs, and when i gently place my hand on either's noses, They quickly thrust their heads up. Why is this? Gbgg89 (talk) 04:29, 12 May 2008 (UTC)

Maybe it is a response to a nearby source of food, so perhaps to bite your finger? Astronaut (talk) 09:29, 12 May 2008 (UTC)

Maps and Time lines of plants, insects, sm. animals, and terrain.

I am looking to assemble a wide verity of information grouped together covering a certain area of land.

Along the border of China and Mongolia. 100 miles south of border to north 200 miles inside Mongolia From western border to eastern border

All from the time of 125 million to 300 million years ago.

Maps and graphs containing:

-Topographical : - Terrain

                - Water levels highs and lows
                - Some research sight (containing programs as to what the place looked like
                  back then

-Time lines of : - insects (paleontology)

                - sm. animals
                - fossils
                - charts graphs

WHY:

First Flower PBS Airdate: April 17, 2007 Professor Sun Ge, from China's Jilin University, is certain that early flowers evolved here, in northern China, and he is determined to find the world's first.

Not far from the border of Inner Mongolia, there is a remarkable fossil site that is revealing what the Earth looked like more than 100,000,000 years ago. —Preceding unsigned comment added by Coffee1030 (talk • contribs) 05:15, 12 May 2008 (UTC)

ARUN SINGH BAGH

WHAT IS THE NAME OF THE WOODEN BLOCK ON WHICH THE WINNERS IN OLYMPICS STAND WHEN THEY GET FIRST SECOND AND THIRD POSITION —Preceding unsigned comment added by 195.189.142.54 (talk) 06:03, 12 May 2008 (UTC)

It is called a medal podium. Rockpocket 06:12, 12 May 2008 (UTC)

telecommunication-microwave survey as used in network establishment

elecommunication-microwave survey as used in network establishment — Preceding unsigned comment added by 61.246.1.108 (talk) 07:30, 12 May 2008 (UTC)

Do you have a question? Astronaut (talk) 09:07, 12 May 2008 (UTC)

It could be a site survey. Graeme Bartlett (talk) 04:55, 13 May 2008 (UTC)

Insanity

I don't know a lot about psychology (I got as far as AP psych in high school, so I know the basics), but I've recently gotten curious about how people go crazy. Since I don't have much background in the area, I don't where to go to learn about it. Any ideas? Also, as a subquestion, does insanity universally degrade a person's ability to succeed, or are there cases of people who become smarter, more creative, what-have-you after losing it than they were before? Black Carrot (talk) 07:35, 12 May 2008 (UTC)

The answer will depend on which specific conditions you group under the umbrella term of insanity - note that "insanity" is no longer considered a medical diagnosis (although it is still a rather loosely defined legal term in the UK and the USA). A fairly generic answer to your various questions might be as follows:

1. Many psychiatric conditions may be diagnosed in childhood, in adolesence, or appear in later life, possibly due to an event that triggers or exacerbates a previously unnoticed condition.
2. There are several autobographical and semi-autobiographical accounts of the onset of a psychiatric condition - see Girl, Interrupted, I Never Promised You a Rose Garden, The Bell Jar.
3. Most psychiatric conditions, as long as they are properly diagnosed and managed, do not prevent a person living a "normal" and indeed successful life. There are several well-known examples of people with a psychiatric condition that appears to be intimately linked to their success in a particular field - see, for example, John Forbes Nash (schizophrenia); Vincent van Gogh (possibly schizophrenia or bipolar disorder); Stephen Fry (bipolar disorder); Richard Borcherds (Asperger syndrome) ... Gandalf61 (talk) 10:25, 12 May 2008 (UTC)

Try reading up on: biopsychiatry and causes of mental disorders. Re Gandalf61, see creativity and mental illness. --Mark PEA (talk) 20:00, 12 May 2008 (UTC)

Entropy and Creationism

A common argument for Creationism is that as entropy can only increase there must be a start where everything is in order, which is when God created the universe. What is a rebuttal for this argument? How come entropy was so low after the Big Bang? --antilived^{T | C | G} 07:38, 12 May 2008 (UTC)

See Objections_to_evolution#Evolution_violates_the_second_law_of_thermodynamics, Entropy and life and Five Major Misconceptions about Evolution at TalkOrigins. Guettarda (talk) 07:53, 12 May 2008 (UTC)

OK that makes sense but how come the universe didn't go into heat death as soon as it was created? What had caused the disequilibrium (if that's a word)? --antilived^{T | C | G} 08:10, 12 May 2008 (UTC)

"Why was the entropy of the early universe so low ?" is a good question, and one of the big puzzles of cosmology. Rogare Penrose addresses the question at some length in The Road to Reality. There are several candidate explanations:

1. The universe has a very, very long pre-Big Bang history, and what we think of and observe as the Big Bang was a random fluctuation in which all the matter of the universe happened to arrange itself into an especially low entropy state (remember that processes that reduce entropy are not absolutely impossible, they are just very unlikely, and anything that is not impossible can happen if you wait long enough). In this view, our current state of increasing entropy is a relativley short-lived phase in the mega-history of the universe.
2. A large number of universes are continually being created, possibly by some sort of quantum "budding" process. Those that start in high entropy states are spectactuarly dull places and do not give rise to life. Only a universe that starts in a low entropy state could eventually give rise to beings that ask the question "why was the entropy of the early universe so low ?". This is a version of the strong anthropic principle.
3. Some mechanism active only in the early universe, and possibly connected with cosmic inflation, drove the universe into a low entropy state. Such a mechanism would break the second law of thermodynamics, so it cannot be active in the universe as we observe it today.

So there are various possible explanations - we just don't yet know which one is correct. Gandalf61 (talk) 09:25, 12 May 2008 (UTC)

And note that even if you want to say that God had a hand in this, it still requires an understanding of what naturalistic process God would have used to do it. "God did it" doesn't relieve the need for a physical explanation—even if it was done by some sort of intelligent deity there still would be a corresponding physical expression of that action. --98.217.8.46 (talk) 15:02, 12 May 2008 (UTC)

The first two options don't work at all, and Penrose should realize this. They're the cosmological equivalent of the 747-from-a-junkyard argument against biological evolution. Darwinian evolution is not a 747-from-a-junkyard theory, and if it were then it would be as useless as the ID people think it is. It would be unfalsifiable and predict nothing. Option 3 isn't an option, it's practically a definition of what it means to explain something. Explaining something doesn't mean showing that the world can be that way, it means showing that it couldn't have been some other way. You have to produce a mechanism that makes the world we see more likely than it appears on the surface. You have to rule out something beyond what you ruled out a priori with your anthropic (or aeronautic) principle.

In principle the idea of anthropic reasoning makes sense. What scientists do is reason from the available evidence to a theoretical model that explains it. One piece of evidence available to us is the existence of homo sapiens. If you reason from that evidence to a theoretical conclusion, you've engaged in anthropic reasoning. But in practice no one ever succeeds in doing that; it's too hard. Progress in natural philosophy began when people started to gather evidence about much simpler things, like the motion of a wheel on an inclined plane. As far as I know there has never been a successful anthropic argument in the history of science. All of its claimed successes are co-opted. Fred Hoyle reasoned from the observed abundance of carbon in the universe to a prediction that carbon must have a particular energy level, which was later found. This was claimed as an anthropic prediction. Why? Because human beings contain lots of carbon. It could just as well have been lithium instead of carbon that went into his argument, and then no one would have called it anthropic. Even worse is the current claims of anthropic reasoning in string theory. They want to narrow down the possible flux compactifications in string theory by requiring that they produce a universe consistent with the one we see. This is known as "fitting the model to the data", and it's what scientists have always done. The data is this case is that which supports the Standard Model and the existence of a small positive cosmological constant. It seriously scares me that prominent string theorists think they're "reasoning anthropically" when they do this. That, more than anything else, makes me worry that they've completely lost sight of reality. -- BenRG (talk) 16:56, 12 May 2008 (UTC)

Not going to pretend that I understand what triggered that particular rant, but let's clarify something for the record. Penrose doesn't actually come down in favour of any of the above three explanations. In fact, he sets them up in order to knock them down in favour of his own explanation, which is connected with quantum gravity. Gandalf61 (talk) 21:55, 12 May 2008 (UTC)

Michelson Interferometer

If the mirror is moved away then the number of fringes appearing in the microscope would change or not? If so then it is because the length of path is changing and so fringes are closely spaced. —Preceding unsigned comment added by MAQMAQ (talk • contribs) 08:54, 12 May 2008 (UTC)

Please do your own homework.

Welcome to the Reference Desk. Your question appears to be a homework question. I apologize if this is a misevaluation, but it is our policy here to not do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn how to solve such problems. But here is a hint to help you: consider what the interferometer is doing, how the fringes are created and what happens if one of the mirrors is moved.

Please attempt to solve the problem yourself first. The Michelson interferometer article might help, or you can search Wikipedia or search the Web.

Astronaut (talk) 09:27, 12 May 2008 (UTC)

Aloe Vera

I have been told that Aloe Vera Gelly will kill ear mites in dogs. Can anyone confirm this? Mr Beans Backside (talk) 10:12, 12 May 2008 (UTC)

Please ask your veterinarian. -- Coneslayer (talk) 11:47, 12 May 2008 (UTC)

Plants

When do plants use the cyclic electron pathway instead of the noncyclic pathway? Mr Beans Backside (talk) 10:13, 12 May 2008 (UTC)

You mean, "why do plants use the non-cyclic pathway?" The cyclic pathway has as its sole useful product ATP, whereas the non-cyclic pathway also produces NADPH (in addition to oxygen), which is necessary for driving the calvin cycle. Indeed, the cyclic pathway is considered more primitive; any photosynthetic organism relying solely on that process would have a fine source of ATP only in the daylight, and would need yet another process for using that energy to obtain or build the various molecules it needs. An organism using the non-cyclic pathway can use the NADPH to drive the conversion of CO2 into sugars, which can be used as stable stores of energy, polymerized into structural molecules, or converted into virtually any other molecule the plant needs. Someguy1221 (talk) 15:24, 12 May 2008 (UTC)

Global warming

What are some simple steps or creative ideas that people can take at home and work to combat global warming? Mr Beans Backside (talk) 11:50, 12 May 2008 (UTC)

• Ditch your SUV for something that uses less than 6 litres of petrol per 100km
• Plant a tree
• Turn down the temperature on your geyser or get a blanket to insulate it (in SA we use electrically powered geysers and our electricity is generated from coal (mostly) so this may not apply to you) and don't waste energy
• Make sure your house is well insulated
• Vote for politicians who are committed to reducing CO2 levels
• Recycle

I see there are quite a few wiki articles but linking all of them will make you less inclined to read any of them so I'll wait for someone to link the best one.

Zain Ebrahim (talk) 12:49, 12 May 2008 (UTC)

For those not familiar with British idiom, a geyser in this context is a water heater, and not an erupting hot spring. TenOfAllTrades(talk) 13:52, 12 May 2008 (UTC)

Is it some dialect? I'm British (North-West) and did not recognise the term, though I did surmise the correct meaning. --Seans Potato Business 14:14, 12 May 2008 (UTC)

I'm British, South-East, and didn't recognise it either. Zain mentions SA (South Africa, presumably) - I guess it's a term local to there. --Tango (talk) 14:18, 12 May 2008 (UTC)

Oh Sorry! I've only ever referred to it as a geyser and assumed it was a universal term. It not only heats the water but it also stores the heated water. Does a water heater do that as well or do you guys store the water elsewhere? Zain Ebrahim (talk) 14:42, 12 May 2008 (UTC)

Modern systems heat the water as its needed. You switch on the tap and the heater (or "boiler") switches on and hot water comes from the tap. This system is more energy-efficient than trying to store a quantity of hot water. Such storage systems do exist in the UK but are comparatively rare in low-usage applications (average household). ----Seans Potato Business 15:16, 12 May 2008 (UTC)

Interesting. Thanks. Zain Ebrahim (talk) 16:10, 12 May 2008 (UTC)

In the United States, the systems that Seans Potato Business described are uncommon. The common heater is the kind with a storage tank, like you described. However, the term "geyser" was completely unfamiliar to me. We just call them "water heaters" (or, rather strangely, "hot water heaters"). -- Coneslayer (talk) 16:32, 12 May 2008 (UTC)

Interestingly enough, the disambiguation page for "geyser" says that is can be "A water heating system, in British English". Although I have lived in the USA all my life, as a self-described Anglophile I understood geyser as used by Zain, so I'm perplexed by our NW and SE British colleagues indicating non-awareness of the term. Perhaps you need to read more Agatha Christie ;-) The various types of heaters and some of the terminology are discussed in the article water heating. --LarryMac | Talk 17:14, 12 May 2008 (UTC)

What I know as geysers used to be fairly common in the UK in my younger days - at least up to the 1970s. They were gas-powered devices where the main gas burner would ignite from a pilot light, usually with a terrifying whoomph, when the water was turned on. There was great skill required in getting the rate of water-flow just right: too fast and it wouldn't get hot enough, too slow and the gas would go out. AndrewWTaylor (talk) 19:58, 12 May 2008 (UTC)

I know these things as "boilers". In my experience, the hot water is usually stored in the UK. You have a boiler and a hot water tank. Heating the water immeadiately before using it sounds hard, since you need to heat it really quickly (certainly more efficient, though). --Tango (talk) 10:58, 13 May 2008 (UTC)

Eat less meat or go vegetarian. 200.127.59.151 (talk) 15:54, 12 May 2008 (UTC)

He was talking about lowering global temperature, how does eating less meat contribute? Mac Davis (talk) 17:55, 12 May 2008 (UTC)

200 was probably referring to Attribution of recent climate change#Key attributions#Land use#Livestock and land use. Zain Ebrahim (talk) 18:14, 12 May 2008 (UTC)

(edit conflict) In theory, less people eating meat would mean less land used for grazing lands. Less rain forests clear-cut to create grazing lands leaves more trees. More trees consume more carbon dioxide. And so on. Of course there's all that methane not being produced by farting cattle as well. --LarryMac | Talk 18:18, 12 May 2008 (UTC)

Change your incandescent lightbulbs to compact fluorescent lamps.118.90.102.125 (talk) 12:38, 13 May 2008 (UTC)

Protoplast fusion

while performing protoplast fusion we have to chop leaves into very fine peices before proceeding for actual fusion. so why don't the cells die out at that moment?--Kayatheangel (talk) 13:19, 12 May 2008 (UTC)

Finding CpG islands with genomic databases

How do I determine which area of a gene can be designated 'CpG' island? Suppose that I'm interested in this gene; I vcan see that it has a lot of CpGs but can I get a program (preferably online) that defines the CpG island(s)? ----Seans Potato Business 13:34, 12 May 2008 (UTC)

• http://www.cpgislands.com/
• http://www.bioinformatics.org/sms2/cpg_islands.html
• Or, normally, you can go to the contig viewer in Ensembl [28], go to the "detailed view" section and in the menu bar, click on the "features" tab. The check the "CpG island" check box, close the tab, it you should see a track on the viewer showing islands in the context of your gene. Ensembl seems to be having technical issues at the moment, and it finds an error when I do it, but it should be working again soon. Rockpocket 19:47, 12 May 2008 (UTC)

Widely-distributed, semi-technical history of moon shot?

Was there anything like the Smyth Report for the Apollo program, or for the Apollo 11 mission (moon landing) specifically? The Smyth Report was a government-produced history of the atomic bomb that came out contemporaneously with its use, to explain in more detail what people were seeing on the front pages of newspapers after the bombings of Hiroshima and Nagasaki. Anything like that for the space race? I don't mean official histories that came out years later, or unofficial histories/popularizations. --140.247.242.128 (talk) 17:16, 12 May 2008 (UTC)

While I can't directly answer the question, bear in mind that the Apollo program, and the related programs preceding it, were carried out in view of the public, in contrast with the secret Manhattan Project. There is not, as a result, the need for a parallel to the Smyth Report. — Lomn 19:45, 12 May 2008 (UTC)

Oceans, Lakes, and Seas

What is the differance between an ocean,lake,and a sea? —Preceding unsigned comment added by Unclejojo (talk • contribs) 17:43, 12 May 2008 (UTC)

(I made a new section, if no one minds) An ocean is a large salty body of water that is part of Earth's main body of water, a lake is a body of water surrounded by land, and a sea is a body of salt water surrounded by land and connected to the ocean (however, some salty lakes are called seas). 206.252.74.48 (talk) 18:46, 12 May 2008 (UTC)

A "sea" can also be a (pretty arbitrary) geographical region of an ocean, for example, the Sargasso Sea, the South China Sea.

Atlant (talk) 19:05, 12 May 2008 (UTC)

Earthquakes

I understand how earthquakes start - the release of pressure from two tectonic places which are pushing against each other or rubbing across each others boundary's - but how do earthquakes stop? What stops the plates from continuing to move? Mr Beans Backside (talk) 18:08, 12 May 2008 (UTC)

As I understand it, the plates are moving pretty much the whole time. An earthquake happens when the plates get stuck and pressure builds up until it is forcefully released and the plates continue moving again. --Tango (talk) 18:18, 12 May 2008 (UTC)

Or put another way, the plate portions right at the boundary get stuck again when enough strain energy has been released. Stress starts to build up again, since the plates as a whole are moving, but they are jammed against each other at the boundaries. Rub your fingers hard across a rough surface - you hand is moving continuously, but your skin is stopping and starting. Franamax (talk) 19:16, 12 May 2008 (UTC)

What you describe are interplate earthquakes. There is another kind Intraplate earthquakes. They are rarer, but generally more destructive. You might also want to have a look at Subduction. Lisa4edit (talk) 20:21, 12 May 2008 (UTC)

Paleontology

How do paleontologists determine the sex of a fossilized creature? Mr Beans Backside (talk) 18:09, 12 May 2008 (UTC)

I think it depends on the creature, but there are usually things that differ between the sexes. The total size, the size of certain body parts, the shape of certain body parts, etc. --Tango (talk) 18:16, 12 May 2008 (UTC)

But all you would have is bones? Does the bone structure differ between the sexes? Mr Beans Backside (talk) 18:24, 12 May 2008 (UTC)

Bone structures often (although not always) differ by sex. If the creature is extant (still alive somewhere), the skeletons of the male and female can be compared for differences. The specific differences between sexes vary by species. For instance, the presence of a baculum is an indicator of male (although females can have a baubellum) in most mammals; likewise antlers in deer, pelvic structure in humans, etc. might be used. For extinct species the work is mostly analogy to living relatives, although this can be difficult. The use of ancient DNA has also been able to shed light on some of the more recently extinct creatures. Some genetic work on moa (extinct, flightless birds of New Zealand), for instance, was able to show three "species" (classified by bones) were really one species of bird but of different sexes (two sexes, of course, the original classifier, Richard Owen working in the 19th century, had based the distinction largely on size). --TeaDrinker (talk) 18:31, 12 May 2008 (UTC)

Male to female ratio

Human offspring are roughly balanced 50% male to 50% percent female. Does this balance exist throughout nature, or has evolution resulted in more useful proportions for some species? For example, more male dear because some might die fighting each other. If proportions are unbalanced in some species, how does this work? Mr Beans Backside (talk) 18:45, 12 May 2008 (UTC)

Have you read sex ratio? -- Coneslayer (talk) 18:49, 12 May 2008 (UTC)

I'm not sure but I think animals like aphids have females or males which can reproduce asexually during certain seasons. Surely this would create such an 'unbalance'. Regards, CycloneNimrod^Talk? 18:51, 12 May 2008 (UTC)

Actually the human sex ratio is not balanced at birth, since males tend to die faster. Evolution has resulted in this proportion, 50.5:49.5 as a response.

In some other species, the sex-ratio changes in response to food availability, more males in times of abundance, more females in times of scarcity. Franamax (talk) 19:21, 12 May 2008 (UTC)

More detailed answers: Wikipedia:Reference desk/Archives/Science/2007 October 26#gender ratios in a species. Rockpocket 22:01, 12 May 2008 (UTC)

Does the universe spin?

The planets, solar systems, star clusters, and galaxies all spin. Does the universe itself spin? Mr Beans Backside (talk) 19:58, 12 May 2008 (UTC)

We have no evidence that it does and no reason to expect that it would. The systems you mention, from planets to galaxies, are all examples of systems that have coallesced under the force of gravity. Gravitational contraction preserves any initial angular momentum a system may have had at random, and as a result amplifies a system's rate of rotation. However, by contrast, the universe as a whole is not a gravitationally collapsed system, and hence the same dynamics will not apply. Dragons flight (talk) 20:04, 12 May 2008 (UTC)

Apparently there are a lot of bored theorists, cause it isn't that hard to google papers on rotating universe versions of cosmology. This quotes a limit of 2×10⁻¹³ radians/year, or one revolution every 30 trillion years. Dragons flight (talk) 22:17, 12 May 2008 (UTC)

This is making my head spin

Isn't "spinning" defined in relation to surrounding space? But what if there is no surrounding space? How could you tell the Universe is spinning if you have nothing outside the Universe to compare its changing position to? Just curious.  :)  The Transhumanist    21:28, 12 May 2008 (UTC)

Excellent question, and not an easy one to answer. I'm not sure if there even is a generally accepted answer. Consider this: You have two masses connected by a string, you set them spinning around their common centre of gravity and the string will go taut. What happens if you do it in an otherwise completely empty universe? They're not spinning with respect to anything else, since there isn't anything else, so does the string go taut? --Tango (talk) 21:39, 12 May 2008 (UTC)

Yes the string would go taut, the physics to calculate this does not involve any other entity. spin is not relative. It is a bit too abstract for me to talk about an entirely empty universe, instead consider a very empty space, very large space, you know the string would be taut in this case. If you want some more interesting physics, Black holes preserve angular momentum as one of the few properties that exists beyond the event horizon. GameKeeper (talk) 22:35, 12 May 2008 (UTC)

The short answer is "no" - you can tell if something's spinning due to the appearence of interial forces, namely the "centrifugal force". I don't believe this has ever been measured for the universe, which'd give some low upper limit, but I don't know what it is. WilyD 21:57, 12 May 2008 (UTC)

I'll back up this 'no'. Spin is not relative, it's not measured in relation to the surrounding space but can be absolutely determined due to the accelerations it involves. The maximum spin of one revolution every 30 trillion years (as mentioned above), would mean the universe would have to be 2000 time older than current best estimates before it did one rotation. Something rotating at a maximum of such a rate most definitely would not be described as spinning. GameKeeper (talk) 22:27, 12 May 2008 (UTC)

You can construct theoretical models of a rotating universe. There's no axis of rotation (much like there's no center to the expansion), but there is a direction (of the angular momentum vector), so these models violate the cosmological principle. This would be visible as an anisotropy in the cosmic microwave background. There was actually a claim a few years ago that such an anisotropy does exist (astro-ph/0502237). I don't know what the current status of this is, but the evidence for it is weak at best. -- BenRG (talk) 23:35, 12 May 2008 (UTC)

I'm surprised no one has mentioned Mach's principle. -- BenRG (talk) 23:35, 12 May 2008 (UTC)

Yes of course, that's why I left this thread alone. Basically (if I understand it right), the only way you know for sure you're spinning is because of the presence of distant "fixed" stars. It is the presence of those incredibly distant stars that establishes your own local inertial frame. Put another way, if the whole universe was spinning, how would you know? There would be nothing to measure it against, and you could equally say that the whole non-universe was spinning and the universe was standing still. It would make no difference. Franamax (talk) 03:12, 13 May 2008 (UTC)

Of course, there's no particular reason to believe Mach's principle is true... WilyD 04:42, 13 May 2008 (UTC)

One could easily apply Newton's Bucket argument instead - which seems just as reasonable, and experimentally indistinguishable. WilyD 04:44, 13 May 2008 (UTC)

Newton? That hack couldn't even dodge a falling apple! Reading through that article, beyond the fact that there is an external observer of the bucket, I see "true motion can be understood only in reference to absolute space" - but the notion of absolute space has been pretty throughly destroyed, along with absolute time. We're only left with relativity, and Mach used the relation to fixed/distant stars. The central axis of the bucket is pointing to one particular star, the rotating reference frame of the water is defined by the fact that other distant stars "revolve around the bucket". The point here though is that if there is nothing outside the bucket-universe, "spinning" loses all meaning, you can't define spinning if there's nothing outside to look at. That article could probably use an update to elaborate how the view of absolute measurement has since fallen apart. Franamax (talk) 07:25, 13 May 2008 (UTC)

Cloned fingerprints

Would a genetic clone have the same fingerprints as the original? Mr Beans Backside (talk) 20:05, 12 May 2008 (UTC)

I seem to remember hearing that identical twins have different fingerprints, so I would expect a clone to have different prints too. --Tango (talk) 20:08, 12 May 2008 (UTC)

Similar but not identical.[29] There are lots of sources on this. Gwen Gale (talk) 20:18, 12 May 2008 (UTC)

Are fingerprints also dependent on environmental factors? Would that cause a sufficient difference for them to be distinguishable? Mr Beans Backside (talk) 20:24, 12 May 2008 (UTC)

Yes. Gwen Gale (talk) 20:26, 12 May 2008 (UTC)

Hi. On the other hand, irises are even more unique than fingerprints. Even identical twins will have different iris patterns. Hope this helps. Thanks. ~AH1^(TCU) 23:10, 12 May 2008 (UTC)

shortwave radio

hi, I am interested in buying a shortwave radio (not to transmit just to receive) but am interested in hearing ham radio too.

I am confused as to if i need ssb (short sideband??) with also usb, lsb and cw.

can someone clarify? also can i spend $100/£50 rather than a lot , if so please post a link.

thx —Preceding unsigned comment added by 78.144.146.123 (talk) 21:25, 12 May 2008 (UTC)

According to our article on Single-sideband modulation, you will need it to hear ham radio. See also sideband for more info on bands. As with most things, you get what you pay for, the cheaper radios seem to only receive normal shortwave broadcasts. You might also need a big antenna to pick up ham transmissions. Try googling "buy shortwave radio", there are hits for information and purchasing. Franamax (talk) 22:06, 12 May 2008 (UTC)

Just to get the terminology straight, if a radio is capable of receiving "Single Sideband" (SSB), it can receive either the "Upper Sideband" (USB) or the "Lower Sideband" (LSB). It can also receive Morse code ("continuous wave"/CW) transmissions. And I think any radio that can receive SSB (as used by most amateur radio operators) can also receive ordinary amplitude modulation (as used by most commercial and state-run shortwave radio stations. But not all AM radios can receive SSB; that takes extra circuitry in the receiver.

Atlant (talk) 00:33, 13 May 2008 (UTC)

Trivia note: if you're driving in Canada and see a license plate starting with "VE", that's a ham radio operator, the license number is their call-sign, they get it for free. Ram their car, you can ask them all sorts of questions while you wait for the police ;) Franamax (talk) 03:05, 13 May 2008 (UTC)

For several decades, amateur radio "hams" have used ssb for their voice transmissions, because it transmits farther for a given power limit and per government regulatins. Without SSB your receiver would only make their transmissions sound like Donald Duck. Look for a receiver with SSB. A Beat frequency oscillator (BFO) is needed to pick up Morse code transmissions. A radio which picks up SSB should also pick up CW (Morse code). Without the BFO capability, a radio would only pick up shortwave transmissions like goverenment radio stations (news, propaganda, etc). I have used a radio frequency signal generator with a non-ssb receiver to pick up ssb and cw transmissions, but I do not recommend it. Edison (talk) 04:34, 13 May 2008 (UTC)

Sociocultural evolution

Sociocultural evolution, the progression:  Hunter-gatherer bands → Social rank → tribes → Social stratification → chiefdoms → Neolithic Revolution →→→ Civilization: Agrarian society (Pre-industrial society): Agrarian villages → Towns → Cities → City-states → Nation-states →→ Industrial Revolution → (Modern) Industrial society →→ (Postmodern) Post-industrial society → Informational Revolution → Information society → Digital Revolution →→ Globalization → World government?

Is that correct?

The Transhumanist    21:30, 12 May 2008 (UTC)

you missed off this one:

http://en.wikipedia.org/wiki/United_Federation_of_Planets —Preceding unsigned comment added by 78.144.146.123 (talk) 22:13, 12 May 2008 (UTC)

Is it correct? Only if you assume evolution of this sort is both linear (non-branching) and teleological (driven towards a specific end). Neither of which are reasonable assumptions (or supported by evidence) in either biological or sociocultural evolution. --98.217.8.46 (talk) 00:41, 13 May 2008 (UTC)

The thing which might make World government inevitable is the failure of so many to have achieved the first tier and fewer the next and so on. -- Taxa (talk) 01:41, 13 May 2008 (UTC)

You missed out religion, which has always played a major role in social development (kings often relied on a priest-class to confirm their divine origins). That influence has varied through time and directed sociocultural evolution into several divergent paths. (Note, you can always play Civ3 to check your theory out:) Franamax (talk) 03:01, 13 May 2008 (UTC)

That seems more or less a correct hierarchy of least to most complex societies. Keep in mind that societies, as 98.217.8.46 implied, may move "backwards" so to speak. The collapse of the Roman Empire was a step back from the nation-state to the city state for parts of Europe. They may also skip steps. The Native American tribes have pretty much been absorbed into the American nation-state.

Durant has a hierarchy of his own going:

• family
• clan: a group of related families occupying a common tract of land, having the same totem, and governed by the same customs or laws
• tribe: a group of clans united under the same chief
• state: based on geographical contiguity rather than kinship
• ...

I'm sure he goes on, though I haven't gotten very far in The Story of Civilization. — Ƶ§œš¹ _{[aɪm ˈfɻɛ̃ⁿdˡi]} 05:45, 13 May 2008 (UTC)

An excellent read along with The Story of Philosophy. 71.100.14.205 (talk) 11:02, 13 May 2008 (UTC)

Brown versus green (fuel/CO₂ versus O₂ production)

Suppose I have 50 acres covered with a 15 year old stand of pine trees (another 5 years of growth needed to become suitable for harvest as lumber) for which I'm offered a certain amount to harvest now. The amount of the offer sounds reasonable but a higher reward might be possible from firewood than lumber. Before I make a decision I need to know how much energy and carbon dioxide the stand can produce and how much oxygen will be lost in order to make the right green decision. Is there a template I can use to facilitate this analysis or is all this talk about green just meaningless theory? 71.100.14.205 (talk) 22:02, 12 May 2008 (UTC)

If you want to reduce CO₂, then lumber is the way to go. If you burn the wood, all the CO₂ gets released back into the atmosphere, if you keep it as wood, it's stored up. --Tango (talk) 10:47, 13 May 2008 (UTC)

Unfortunately economics have to be made part of the equation such as in maximizing the profit by using the energy availability as a positive and the co2 output as a negative. A template for determining the amount of timber per acre would probably help. 71.100.14.205 (talk) 11:27, 13 May 2008 (UTC)

Ergonomics of press-up exercise

Are press-ups an ergonomic exercise or do they cause undue strain on the wrists? ----Seans Potato Business 22:04, 12 May 2008 (UTC)

May 13

Can my macaw breed with his macaw?

Mine: Female hyacinth macaw

My friend's: Male red and green macaw

Supposing that the two birds get along and eventually pair up, will they be able to breed? --81.77.245.65 (talk) 00:21, 13 May 2008 (UTC)

I'm no expert, but it should work. Hyacinths are reported to be very difficult to breed, though. Considering that our page lists hyacinth macaws as endangered, wouldn't you rather want to see if a zoo or breeder in the area has a male hyacinth and breed yours with that one? Just a suggestion. -71.236.23.111 (talk) 01:44, 13 May 2008 (UTC)

I don't think so. They aren't even in the same genus. bibliomaniac15 04:22, 13 May 2008 (UTC)

Bird hybrid has a couple of examples. Somewhere it said that different genera don't breed in nature, but some mate successfully in captivity. It would just be a pity in this case because the species needs the contribution of every surviving member for genetic diversity. Hope you'll decide to get a suitable hyacinth gentlemen for her. Lisa4edit (talk) 05:37, 13 May 2008 (UTC)

Animal stripes

<moved from misc desk>
Do baby tigers, leopards, and zebras get more stripes or spots as they grow older, or do the stripes and spots they are born with get bigger? Mr Beans Backside (talk) 19:07, 12 May 2008 (UTC)

Push/press ups with equipment

Following the ergonomic question above, I was wondering why people recommend using equipment for pushups, say holding small dumbells to the floor. Does this technique work different muscle sets or is it a ploy to sell more equipment? Julia Rossi (talk) 02:13, 13 May 2008 (UTC)

Personally, hands flat on the floor stresses the wrists more than using little things with handles which allow the hands to be more curved. Edison (talk) 04:27, 13 May 2008 (UTC)

Thanks Edison. Julia Rossi (talk) 09:58, 13 May 2008 (UTC)

help in cleaning up a dog's skull

Hi what steps should I take to clean up a skull that I found. here are the specifics:

1. Found half-buried in sand used for construction (the greyish one)
2. Most of the skull is dark brown in color. An unburied part is cracked and whitish.
3. The lower jaw is missing.
4. My female co-worker was disgusted when I picked it up and kept it.
5. It looks like a dog's skull, about 15-20 cm long.
6. It still has teeth.
7. It smells funky but I can't find any flesh clinging to it. No idea regarding the brain though

I want to make it sparkling white and tough to boot. I hope the ingridients that you would reccomend are easily found and cheap.--Lenticel ^(talk) 06:03, 13 May 2008 (UTC)

For a similar question in March 08[30] and preserving a rabbit's skeleton in Feb 08 here[31] with one of the answers as ants ants ants. On a documentary I saw a forensic scientist using detergent with its enzymes or whatever, breaking down pig's parts, but don't remember that it mentioned skeletons, only ways of getting rid of bodily crime evidence. Julia Rossi (talk) 06:16, 13 May 2008 (UTC)

You should win a prize for hitting on a topic for an article missing from wikipedia. Our articles mention "preparation" and "preparator", but there's no page. Taxidermy doesn't cover it. Pathologists' Assistant I thought was a very odd link from the German wikipedia, which does have and article. --Lisa4edit (talk) 06:24, 13 May 2008 (UTC)

Then there's google[32] cleaning your own animal bones by soaking in water with some detergent and more – like how to clean a skull (taking care not to overdo things) here[33]. This article has really clean white skulls. All common ingredients and cheap as so good luck, Julia Rossi (talk) 06:33, 13 May 2008 (UTC)

I like the last two sources. I'll have a sparkling skull in no time. Thanks!--Lenticel ^(talk) 07:05, 13 May 2008 (UTC)

hydrocarbons

what is the formula for finding how many isomers a hydrocarbon has? —Preceding unsigned comment added by 41.204.224.23 (talk) 10:20, 13 May 2008 (UTC)

Homework alert. Read the notice at the top of the page, we will not do your homework for you. Regards, CycloneNimrod^Talk? 12:09, 13 May 2008 (UTC)

Current in capacitor and nature of magnetic fields

I have a difficulty understanding how current passes between an insulator in capacitors. Also what exactly is the nature of magnetic fields? What passes in flux lines? Is it a particle, a massless thing with momentum? Or something else entirely? Bastard Soap (talk) 10:48, 13 May 2008 (UTC)