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March 26

time

if I was using a telescope and looking at a clock 10 light minutes away, which I saw was 10 minutes behind mine, 8:50 and 9:00, respectively, and then started travelling to the clock, observing it the whole time, I know it depends on my speed, but what would I observe the clock doing in relation to mine; what time would the clock display? —Preceding unsigned comment added by 98.221.254.154 (talk) 01:21, 26 March 2011 (UTC)

Given that ly is mesurment of distance light travels in certain time you can easily calculate it, but the result depends solely on speed. At 10 minutes you'd see 10 minute delay, at nine minutes you'd see nine minute delay and so on upto no delay when you are at the clock. Assuming you travel at speed of light, it would be 9:10 when you reach the clock. While you're on your way you'd observe clock hands moving clockwise (i.e. not backwards in time) and the clock being behind in accordance to how far you are from the clock, so at 9:01 there would be 9 minute delay and you'd see that it is 9:52, 9:02-8:54, 9:03-8:56, 9:04-8:58, 9:05-9:00, 9:06-9:02, 9:07-9:04, 9:08-9:06, 9:09-9:08, 9:10-9:10 ~~Xil (talk) 04:39, 26 March 2011 (UTC)

The answer above neglects time dilation and problems with relativity of simultaneity. A good place to start trying to understand how these play a role is the twin paradox article. Dauto (talk) 13:39, 26 March 2011 (UTC)

The twin paradox is about acceleration. There is no need to assume any acceleration is going on in this problem. --Tango (talk) 15:35, 26 March 2011 (UTC)

The wording is somewhat ambiguous, but on first reading I assumed that "started travelling to the clock" meant that the observer was initially at rest with respect to the distant clock, and then accelerated as they "started travelling". I imagine Dauto made the same assumption. Gandalf61 (talk) 16:32, 26 March 2011 (UTC)

What about travelling at a fraction of the speed of light? —Preceding unsigned comment added by 98.221.254.154 (talk) 14:27, 26 March 2011 (UTC)

If you travel much slower than the speed of light (so it would take you several days to reach the clock), then we can ignore relativity and the solution is fairly simple. If the clock is 10 minutes behind yours now and we know it will exactly match yours when you arrive, then you must see it ticking faster than yours by such an amount that, in the time it takes you to reach the clock, it's ticked 10 minutes more than yours. If it took you 20 minutes to reach the clock (which is much too fast for us to neglect relativity, but it makes the maths easy!), your clock would have progressed 20 minutes and the other clock 30 minutes, so the other clock is ticking 1.5 times a second, from your point of view. If you take into account relativity, then your clocks wouldn't show the same time when they come together and the whole thing gets rather complicated. --Tango (talk) 15:35, 26 March 2011 (UTC)

If you don't take relativity into account, it probably could be be reduced to simple formula, similar to calculating when will two trains traveling towards each other at diffrent speeds meet, I find it hard to produce it without pen and paper, sorry. You would probably assume that all things except for your speed, which would be, x remain constant. Say if you would be traveling at half the light speed at 9:01 you would be 9.5 light minutes away from clock, so you would observe 9.5 minute delay and observe that time on the other clock is 8:51:30. I might be terribly wrong, but I don't see how relativity could make the answer any diffrent, if you are traveling at light speed. We assume that both the observer and the clock are in same state (not influenced by gravity or anything), we assume that the observer has never been at the clock (so twin paradox dosen't really apply, because it concerns traveling away and then back to a point of reference influenced by gravity etc.), his clock is synchronised with clock he observes and he does observe some effects of relativity as for him it appears that clock he monitors is delayed. If you have a diffrent idea on what would happen go ahead and tell us what he would observe ~~Xil (talk) 16:33, 26 March 2011 (UTC)

Twin paradox has nothing to do with gravity and it does apply here (half a trip still requires relative motion leading to time dilation). Dauto (talk) 17:07, 26 March 2011 (UTC)

So, here is the math. Let's say you move with a speed $v\,$ for a distance $d\,$. A time $t={\frac {d}{v}}\,$ elapses from the point of view of the clock you are looking at through the telescope which was initially synchronized with yours. Because of time dilation the time elapsed on your clock will be given by $t'={\frac {d}{\gamma v}}\,$, where $\gamma ={\frac {1}{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}\,$. Therefore when you finish the trip the two clocks won't be synchronized anymore and the difference between them will be $t-t'={\frac {d}{v}}\left(1-{\sqrt {1-{\frac {v^{2}}{c^{2}}}}}\right)\,$. Dauto (talk) 17:32, 26 March 2011 (UTC)

... isn't that the wrong way round? (Perhaps it depends on who is doing the observing.) Each observer sees the other clock moving more slowly, but their own clock moves at "standard rate". The effect is symmetric. Dbfirs 16:55, 27 March 2011 (UTC)

The effect is not symmetric because one of the clocks must accelerate to start approaching the other clock just like in the famous twin paradox situation. Dauto (talk)

Sorry, yes, I meant that the effect is symmetric whilst travelling at a constant relative speed. It is the effects of the acceleration that creates the paradox. Dbfirs 07:23, 28 March 2011 (UTC)

prediction

Is saying what I am going to do, and then doing it exactly as I described "predicting/manipulating the future"? Is answering someone's question before they ask it, because you know what they are thinking, "information travelling faster than light"? —Preceding unsigned comment added by 98.221.254.154 (talk) 03:22, 26 March 2011 (UTC)

No, and no, that is called intuition, categorised under psycology not relativity. Plasmic Physics (talk) 04:02, 26 March 2011 (UTC)

It is being able to control your own acctions to accomplish your goals and drawing on your expierience form numerous similar situations you've been in. You can do so with a large degree of certanty about what is going to happen, but that is not what people usualy describe as beeing able to predict and manipuate the future - if you could predict that your friend is going to get in car crash if he turns left and it happens it would be predicting future as you have no means to predict random accidents, if you convince your friend not to take that turn you are manipulating the future (but still we can never be certain that the crash would occur) ~~Xil (talk) 04:55, 26 March 2011 (UTC)

I would say that that is predicting the future, as there could be events which prevent you from doing what you planned. Of course, if you do keep the prediction, it's not very impressive. Similarly some psychics predict that there will be "unrest in the Middle East", and they don't deserve much of a prize for that prediction, either. StuRat (talk) 06:47, 26 March 2011 (UTC)

The second question could be generalized to "is simulation a potential means of time travel", and when phrased like that it sounds fairly reasonable (if confusing). 213.122.59.22 (talk) 08:12, 26 March 2011 (UTC)

Physics entire goal is the ability to make qualitative and quantitative prediction about the future, but it still flatly denies the possibility for superluminal information transfer. This should highlight how they are different. —Preceding unsigned comment added by 92.20.201.71 (talk) 11:01, 26 March 2011 (UTC)

Anything you do is manipulating the future. I'm not sure if it counts as predicting if it's something you have control over, but looking it up it seems to work you're still telling in advance, even if you have a hand in it. Answering someone's question before they ask it does not involve information traveling fast. They gave the information before-hand, if unintentionally. — DanielLC 05:47, 28 March 2011 (UTC)

Question about the sub-division of "g"?

Since "g" of an earth may be the combination of inter-gravitational forces between its masses of water, soil, rocks ......[on large scale]. Thus would there be any difference in "g" for the falling of an object due to the following different underlying masses

1- Just above the deepest and largest sea water (mass wise)

2- Just above shore or land close to the shore

if my question is not wrong?74.198.150.216 (talk) 04:53, 26 March 2011 (UTC)Eccentric Khattak#1-420

Yes, mass differences in the ground or water directly under an object will affect the local g by a measurable amount, but not an amount people would notice. StuRat (talk) 06:42, 26 March 2011 (UTC)

See Earth's gravity and geodesy for the study of Earth's gravity, and the GRACE and GOCE satellites which measure the local gravitation field. CS Miller (talk) 12:23, 26 March 2011 (UTC)

Also read our article on gravity anomaly. The gravity anomaly is the measured difference between the expected and actual value of the gravitational force. It is useful when exploring for underground minerals and hydrocarbons. Mapping the gravity anomaly is also useful for calibrating extremely precise aircraft avionics on autopilots and trackers. Usually, though, it is very expensive to perform large gravity mapping surveys, so most of the data isn't available for free on the internet. I did find this example through a web-search: this United States Geological Survey webpage, Airborne Gravity Survey and Ground Gravity in Afghanistan. Their website has scientific information, as well as photos of the aircraft and the equipment used to measure gravity very precisely. Note that you can see the gravity anomalies trend along the terrain and geology, correlating well with the mountainous regions and the river valleys. Other methods of gravity survey include satellite- and ground-based observation and mapping. Nimur (talk) 15:04, 26 March 2011 (UTC)

And for a satellite pair dedicate to gravitational mapping, see Gravity Recovery and Climate Experiment. -- 110.49.249.12 (talk) 23:57, 26 March 2011 (UTC)

Name/purpose for this railroad bridge feature.

What is the name/purpose for the extra set of rails between the main rails on a railroad bridge? They usually angle inward at the ends of the bridge. Here is a picture http://farm1.static.flickr.com/62/225549229_5dcf181f3b.jpg --71.98.72.247 (talk) 05:03, 26 March 2011 (UTC)

Just a guess, but could it be a safety feature, so that if the train jumps the rail, those will catch one set of wheels, so the cars won't be able to hit the sides of the bridge ? StuRat (talk) 06:39, 26 March 2011 (UTC)

Yes, it is called guard rail ~~Xil (talk) 12:00, 26 March 2011 (UTC)

Nice find. Note that the inward bend at the ends is so that a derailed train won't run into the end of the guard rail, making things even worse. StuRat (talk) 21:14, 26 March 2011 (UTC)

mosquito bites and race

Can anyone find information about why mosquitos prefer to feed on Europeans than Africans? My own research has found that when sleeping in the same bed, I get bitten all over, whereas my friend does not at all. The scientist in me can't work out why it is the case, what is it about mzungus that they find so tasty? Thanks 41.138.85.43 (talk) 11:33, 26 March 2011 (UTC)

Isn't it possible that certain people attract or dis-tract mosquitos more than others. Some people simply do not get bitten. Your presumption that they avoid Africans is mis-placed if it's based solely on the fact that mosquitos are more attracted to you than your one African friend. 220.244.35.181 (talk) 11:47, 26 March 2011 (UTC)

The huge number of Africans who contract mosquito borne diseases such as malaria also belies your theory. Roger (talk) 12:13, 26 March 2011 (UTC)

No, his/her argument is that Africans are less likely to be bitten by mosquitoes than Europeans are. Malaria rampant areas are virtually free of Europeans, so your counterargument doesn't stand. That said, his/her argument is still fallacious, as it is a plain dicto simpliciter.--Netheril96 (talk) 12:55, 26 March 2011 (UTC)

I have heard the same "mosquitoes like the white skin" story. There are also various stories running around the Internet^[1] saying that mosquitoes prefer blondes to brunettes, and blondes are rare in Africa. But I also wonder if there are any differences in the probability that an individual mosquito bite will turn out to be itchy - whether due to enzymatic reaction, immune tolerance, or some kind of mental desensitization. For that last, after all, you see so many scenes of people in Africa with flies crawling on them that will make an American squirm just watching the video. I wonder if it's so different from being accustomed to tolerate cold weather. Wnt (talk) 15:44, 26 March 2011 (UTC)

The first mosquito bites 9f the summer are the most itchiest. You build a tolerance but you also lose it without exposure. --85.78.197.19 (talk) 08:29, 27 March 2011 (UTC)

I don't think this is a safe generalization: there are also white people who seem to get bitten a lot less than other white people. The fact is that mosquitoes are sensitive to a pretty wide range of chemicals, and the specifics are not at all well understood. Even the mechanism of the most widely used repellent, DEET, is not all that clearly understood. Until recently the prevailing theory was that it blocks the ability of the mosquitoes to sense the chemical that attracts them, but anybody who uses it in the field can easily see that it has a strong repulsive effect. Looie496 (talk) 17:00, 26 March 2011 (UTC)

Certainly a sample size of n=2 is not adequate for drawing such a conclusion. You and your friend different in things other than just race, presumably, including clothing, deodorant, shampoo, diet, etc., even blood type. How much of that matters to mosquitos, I know not, but isolating race as the only variable is surely fallacious in this case. --Mr.98 (talk) 18:05, 26 March 2011 (UTC)

Two major attractors for mosquitoes are heat and water vapor. It could simply be that you sweat more. --Carnildo (talk) 22:01, 29 March 2011 (UTC)

Fission products in environment => nuclear reactor breach?

If radioacctive iodine has been found in the environment, is that conclusive evidence that at least one of the Japanese nuclear reactor pressure vessels has split or cracked open, or could it come from the stored fuel rods? Thanks 92.29.127.59 (talk) 15:13, 26 March 2011 (UTC)

It most likely comes from the spent fuel rods. Dauto (talk) 16:58, 26 March 2011 (UTC)

A rough guess: if it is Iodine-131, that probably means it is from the reactor (it is a short-lived fission product and its existence would only be significant in a reactor that had recently been running). If it is Iodine-129, it could be either. But the older the fuel, the more Iodine-129 you'd find, so significant amounts of it would probably be more indicative of a spent fuel pool breach. But I am not a physicist. --Mr.98 (talk) 18:01, 26 March 2011 (UTC)

The report discussed here seems to say it is indeed Iodine-131 that has been found, and that it suggests Reactor 3's containment has been breached. So there you go. --Mr.98 (talk) 18:08, 26 March 2011 (UTC)

(ec) No one can know from afar what really happens but iodine decays very quickly and is only produced by fission or neutron capture so it looks improbable that it comes from spent fuel rods. As far as I understand the pressure vessels are not absolutely tight but have valves that regulate pressure. So my idea is that some fuel rods are damaged and the fission reaction is partly going on, producing new iodine that is released from the containment via safety valves. 77.3.187.97 (talk) 18:16, 26 March 2011 (UTC)

The fission has stopped definitely. If they open the security valve to reduce pressure you vent iodine, there is enough iodine in the reactor even after four or five half lives.--Stone (talk) 18:20, 26 March 2011 (UTC)

I admit that I don't know how much total iodine is inside the core and how much has been released but how would you know that the fission has stopped "definitely"? 77.3.187.97 (talk) 18:29, 26 March 2011 (UTC)

The fission is only working with the moderator (water) and without the control rods. Two possible cases: It is very hot and the water is gone -- no chance for fission. Everything is molten -- No reaction, because you have a molten block with no water inside. Two last point the neutronradiation would have been detected and without cooling the reactor would simply melt away if not only decay heat but also the much higher heat production of fission would be present.--Stone (talk) 19:23, 26 March 2011 (UTC)

OK, I see your point(s). If there is no other type of moderator (as graphite like it was used in Chernobyl), fission would stop. But if there was some problems with the control rods (? jammed from the earth quake and not completely inserted ?), wouldn't fission resume when new cooling water was inserted? Of course, only partially, not full scale as in normal operation. Another question: how would one detect neutron radiation from within a water filled containment? Wouldn't even the concrete of the containment shield that completely? 77.3.187.97 (talk) 20:11, 26 March 2011 (UTC)

The control rods were inserted after the earth quake before the tsunami. The reactor always stays within a very thin margin of criticality where the secondary neutrons are used to keep control. If something goes really critical you leave this safe way and get a bomb like explosion.--Stone (talk) 20:57, 26 March 2011 (UTC)

To be clear, that's nothing like a thermonuclear bomb, however. StuRat (talk) 21:54, 26 March 2011 (UTC)

A slow fission reactor cannot undergo a "bomb like explosion". You get lots of radiation and heat, and maybe a small explosion, but nothing on the order of a fission bomb. --Mr.98 (talk) 22:14, 26 March 2011 (UTC)

Not a nuclear bomb explosion scale, but a explosion more like a small grenade. The conversion rate in a nuclear bomb is high while it is low in a criticality accident. But it is enough to produce enough heat to divide the critical mass into separate parts.--Stone (talk) 08:38, 27 March 2011 (UTC)

Surely you can see the need to clarify what one means by a "bomb like explosion" when one is talking about critical masses. Most people still think nuclear plants can go off like nuclear weapons, which is not true. They have their own problems, but that's not one of them. --Mr.98 (talk) 10:06, 27 March 2011 (UTC)

As I understand it, the control rods were actually inserted before the earthquake: Japan's earthquake warning system gave the reactors about 30 seconds' warning of the quake, so the reactors were shut down before the shaking started. --Carnildo (talk) 22:06, 29 March 2011 (UTC)

Does symbolic actions make people change their behaviour?

Today's Earth Hour and the discussion of the pros and cons of it made me wonder what research there is about whether people who participate in some symbolic action (like signing a petition or wearing a button) are more or less likely to do something more substantial for the same cause (like donating money and time or sacrificing some of their comfort). I recall reading at least ten years ago about some study that seemed to show a positive correlation, but I don't remember it well. Sjö (talk) 18:25, 26 March 2011 (UTC)

I think so, it opens them up to Cognitive dissonance. 92.29.127.59 (talk) 19:03, 26 March 2011 (UTC)

You think they are more or less likely to do something? And do you know of any research about it?Sjö (talk) 19:27, 26 March 2011 (UTC)

The article mentions the Ben Franklin effect for example, and that cites some papers. 92.29.127.59 (talk) 19:37, 26 March 2011 (UTC)

Note that correlation doesn't mean causation. That is, observing Earth hour doesn't necessarily make them more environmentally responsible. It's probably the other way around, that people who already were environmentally responsible are those who choose to observe Earth hour. Then there's also the possibility that non-environmentalists might do Earth day just so they can say "I've done my part, now I am done". StuRat (talk) 19:29, 26 March 2011 (UTC)

The article gives some data developed by the experiment. Presumably, policy makers could use this in decisions - e.g., how much greenhouse gas can be avoided if monopoly utilities are allowed to run amuck and raise prices 200%, which allows them to feel better about taking the campaign contribution. Wnt (talk) 21:26, 26 March 2011 (UTC)

Is that assuming that any power which can be cut for an hour can also be cut permanently ? That's completely untrue. I can cut my heat for an hour, but if I cut it permanently my pipes would freeze in winter (as would I). StuRat (talk) 21:51, 26 March 2011 (UTC)

A resounding "yes". Symbolic actions are extremely powerful in terms of effecting human behaviour.It is the human mind's suseptability to symbolism that produces the Ra-Ra to the flag,the puchase of a new car when when the old one is still good,The badge and button wearing, choice of dress style,The Symbolic identification of ones self for others to see. The very identification of homo-sapiens as distinct from earlier hominids is based largely on appreciation of symbolism. The earliest known symbolism,"art"about seventy thousand years ago marks the generally accepted transition to modern humans. Symbolism effects not only the person taking the action but also those who witness it. I suggest you look up the acheivements of public manipulation through symbolism acheived by "Edward Bernayse" throughout most of the twentieth century. I beleive that will give you a much fuller appreciation of the power of symbolism.Phalcor (talk) 17:01, 27 March 2011 (UTC)

I suggest reading "Public relations" published 1952 and "The engineering of consent" 1955.Phalcor (talk) 19:08, 27 March 2011 (UTC)

How about Man and His Symbols by Carl Jung ? StuRat (talk) 19:10, 27 March 2011 (UTC)

collecting water ... using oil

Does this idea violate any laws of thermodynamics? Suppose that air is not saturated -- i.e. evaporation for a naked body of water should be faster than condensation. Suppose I place a large bowl with a large surface area, full of oil.

Suppose water occasionally does condense on the oil. Some of the water will re-evaporate, but some will sink to the bottom -- and a pool of water starts to collect at the bottom of the oil, unlikely to evaporate. Over time, I will accumulate more and more water. Is any law of thermodynamics being violated here? (Or does the oil conceivably become warmer and warmer, lowering likelihood of condensation with each new water being condensed?) AFAIK, oil is acting only like a heterogeneous nucleation-promoting catalyst -- it shouldn't change the equilibrium constant.

It occurs to me that agitation might allow faster introduction of water vapor into the oil, upon which it condenses. This would expend work, which would conceivably then allow the equilibrium constant to change. I however did not study heat engines and chemistry in my general chemistry classes. Are there any relations between mechanical agitation and work -- and say the amount of water I can extract from the air? John Riemann Soong (talk) 18:32, 26 March 2011 (UTC)

I don't see any inherent reason why the first approach would violate thermodynamics laws. However, as a practical matter, the few molecules of water which would condense on the oil would evaporate again before they formed drops large enough to overcome the surface tension and sink to the bottom. Therefore, I think a significant temperature difference would be required to get it to work. Perhaps in the morning, if the bowl of oil was in the shade, and stayed cool for some time, water from the warmer air would condense in sufficient quantities to form drops that would sink to the bottom. However, note that oil isn't required for this. You can have a large funnel to which dew will adhere in the morning, then drip down into a bottle at the bottom. The small hole at the top of the bottle slows to evaporation rate back out of the bottle. You could, I suppose, put some oil in the bottle too, to further slow the evaporation rate, but then you'd have oil mixed in with your water, and the oil might go rancid. As for agitation, that would likely just produce a mixture, like you get when you shake up salad dressing. It would eventually settle out, but it could take many hours or days. Also, the energy used might better be spent on a dehumidifier to collect your water. StuRat (talk) 19:22, 26 March 2011 (UTC)

I'm thinking about the law of microscopic reversibility. I've changed the conditions to favour one direction of the reaction over the other, and so I've distorted the equilibrium somehow. John Riemann Soong (talk) 20:52, 26 March 2011 (UTC)

Like Maxwell's Demon ? StuRat (talk) 21:12, 26 March 2011 (UTC)

Yes. The energy of the environment hasn't changed has it? Neither the energy of the condensed water. (per mol) John Riemann Soong (talk) 21:13, 26 March 2011 (UTC)

In concept you're introducing some energy when the water droplet falls under the oil (if you come up with a way to make this work). So it's not a true Maxwell's Demon, but one using energy to do sorting. Wnt (talk) 21:29, 26 March 2011 (UTC)

The experiment you've described, unfortunately, isn't realistic. As StuRat notes, if the oil is in thermal equilibrium with the humid air, and the air (and oil) are both at a temperature higher than the dew point, then macroscopic amounts of water will never condense out on the oil's surface. You certainly won't ever get droplets large and heavy enough to overcome the surface tension of the oil in order to sink to the bottom.

Even if you start out with water below the layer of oil, the system will still return to the 'proper' equilibrium eventually; you've neglected to consider that water's solubility in oil is low but not zero. There will be a (very slow) transfer of water out of the liquid phase, into the oil-dissolved phase, and back into vapour. (Depending on the temperature and thickness of the oil layer, this is a process which could require months, years, or centuries, but it will happen.) This evaporation through the oil will continue until the air reaches 100% humidity for the temperatures, or until the supply of liquid water is exhausted. Agitation will speed this process, in that it will speed the equilibration of water across the water-oil and oil-air interfaces. TenOfAllTrades(talk) 04:37, 27 March 2011 (UTC)

And apart from all the other technicalities, from a purely practical standpoint. Having experienced on more than one occasion a sudden camping trip, I can tell you that to collect a useful amount of water by natural condensation (no matter how you do it) will require a surface area much, much,much,much,much greater than a large large bowl.Phalcor (talk) 19:36, 27 March 2011 (UTC)

Solution to the colatitude part of Schrödinger in a Hydrogen atom

For some research I'm doing, I'm trying to work through the derivation of the solution to the Hydrogen wavefunction to garner a better understanding of the mathematics behind it. In my searches, I've found that not many people include a detailed explanation of the math behind the differential equation involved in the colatitude ($\theta$) part; most textbooks or informational sources that I've found have simply said something along the lines of, "This is a very hard differential equation. Here's the answer:" I know the final answer comes out to be the associated Legendre function, but I would like to know how this is derived.

I did find, this, however. This page outlines how to set up the differential equation, and this page shows how to solve it. I understand the first page entirely, but I'm caught up on the second page. Specifically, the part when the author expands the nth derivative to obtain Equation 3.3. My questions

1. Why does the author switch from trying derivatives of $(1-x^{2})^{n}$ to trying those of $(x^{2}-1)^{n}$? My first thought was to get the sign of the middle term to match the original DE, but when he derives the (n+1)th derivative, the sign changes due to the fact that n-(n+1)=-1, so I don't really see why he chooses that as his function. Can anyone explain that?
2. Where the sum comes from in the (n+1)th derivative?
3. I think there's a typo in Equations 3.3 and 3.4.. Should the derivative operators not be ${\frac {d^{n}}{dx^{n}}}$ instead of ${\frac {d^{2}}{dx^{n}}}$?
4. Also, I don't understand Equation 3.4.. Why can we just randomly throw in the ${\frac {1}{2^{n}n!}}$ term?

Thanks for the help!--Dudemanfellabra (talk) 18:35, 26 March 2011 (UTC)

You might have better luck searching for discussions of the spherical harmonic differential equation. It's reasonable enough for discussions of the hydrogen atom to skip the spherical harmonic part, since the spherical harmonics are an area of study in their own right.

I'll attempt to answer your questions: 1. I think he tries $(1-x^{2})^{n}$ first, and then, since that doesn't quite work, tries $(x^{2}-1)^{n}$ instead. Trial and error (informed by long experience) is one of the most useful techniques for solving differential equations. 2. I think this comes from a sum of the coefficients of $2(n-1)xw',2(n-2)xw'',2(n-3)xw''',\ldots$. If you do a few derivatives by hand you should see what's going on. Note that $w^{n}$ is a typo; it should be $w^{(n)}$. 3. Yes, that's another typo. 4. You're defining a separate function for each $n$, and these functions are only meaningful up to a constant factor, so it's fine to throw in a factor that depends only on $n$. -- BenRG (talk) 21:03, 26 March 2011 (UTC)

The standard practice of solving (associate) Legendre polynomial equation is power series method.The current Wiki article on that method is incomplete as it only pertains to nonsingular equations, which is almost useless when you encounter special functions. You may find several textbooks on mathematical physics most useful.--Netheril96 (talk) 16:33, 27 March 2011 (UTC)

another current

could we ever ever find another type of current something like oscillating current or rotating current instead of alternating or direct current. Is there only ac and dc? Is there such a thing as magnetic current with magnetic monopoles flowing and that creating a electric field — Preceding unsigned comment added by Lufc88 (talk • contribs) 19:29, 26 March 2011 (UTC)

Well, there's only the possibilities of current being constant (DC) or variable (AC). However, a variable current could vary in different ways. You could have other frequencies, a square wave or sawtooth wave, versus sinusoidal, etc. You could also have the amplitude of the wave stay positive or negative over the entire cycle, versus alternating between them, but I don't see much advantage in that. In any case you can change the voltage or amperage or wattage, independent on the carrier wave used. StuRat (talk) 20:16, 26 March 2011 (UTC)

As far as we're aware, there is no such thing as a magnetic monopole, so you couldn't have a current of them. If magnetic monopoles do exist, then I guess it would be possible. --Tango (talk) 20:26, 26 March 2011 (UTC)

Well, the current described in Magnetic monopole#"Monopoles" in condensed-matter systems is sort of like what is requested, no? Wnt (talk) 21:33, 26 March 2011 (UTC)

Sort of but not really. Real magnetic monopoles have never been found but the theoretical motivation for their possible existence is fairly strong. Dauto (talk) 21:36, 26 March 2011 (UTC)

Noah's Ark

Is the story of Noah's Ark possible? Could two of each animal really fit into a ship that size? —Preceding unsigned comment added by 68.181.201.26 (talk) 20:04, 26 March 2011 (UTC)

Depends on what you mean by "each". If "each" means counting separately each group identified by modern science as a distinct species, the answer is definitely "no". Staecker (talk) 20:09, 26 March 2011 (UTC)

What is possible, however, is them taking some livestock and such on board so they would have a starting point to rebuild after a regional flood (not a worldwide flood, of course). So, there could be a grain of truth there. StuRat (talk) 20:12, 26 March 2011 (UTC)

If you take "each" to mean some arbitrary level between genus and kingdom, then you could fit them and perhaps even the feed necessary for them. John Woodmorappe wrote a book in which he calculated that it was possible if you brought one pair of each "kind", as he put it, and in some cases only brought young animals. His work has been harshly criticized [2] [3], also by other creationists [4].Sjö (talk) 21:23, 26 March 2011 (UTC)

And, of course, there would be no way to get all the species we have now, from that, unless you assume that God made it happen. In this case, why did God need Noah's Ark ? StuRat (talk) 22:34, 26 March 2011 (UTC)

Judaism holds that it was a miracle. Even by the time of the Talmud it was known that it could not have been done by ordinary effort. The text supports this as well (Genesis 7-8 and 7-9) - the animals went in, not Noah took them in. The reason God needed Noah was that the ark was an attempt to get the rest of the people to repent by building an ark so publicly (which is also why it took so long to build). Additionally it's the same reason man needs to plant seeds, rather than just have food appear. Ariel. (talk) 02:08, 27 March 2011 (UTC)

That would make for a really small effective founder population though. John Riemann Soong (talk) 20:57, 26 March 2011 (UTC)

It seems impossible to collect and store away a million species of beetle, for example. But the biological species concept is a construct of modern science, not faith. (For comparison, it's written that God cursed the serpent to crawl on its belly. Which serpent?) And if you allow for arbitrary divine intervention, you can suppose that the beetles all arrived on their own, or were transported on a divine wind, or needed no food, or could occupy the same physical space, or could produce offspring with different genetic codes - obviously, once God gets involved, the laws of physics are kind of out the window. Wnt (talk) 21:39, 26 March 2011 (UTC)

A further problem with Noah's-Ark-As-Fact argued here is the people side of things. "Noah, his wife, his three sons, and their wives" would have had to work overtime to populate the all the emerging civilizations from China to South America in double quick time. Biblical scholars have calculated the date of the Flood to the 25th century BC, just when the Pyramid of Khafre was being built. Alansplodge (talk) 22:59, 26 March 2011 (UTC)

The secret here seems to be the " and their wives " part. How do you know how many wives they had? 212.169.190.116 (talk) 00:06, 27 March 2011 (UTC)

Hmmm.. Probably several million... Alansplodge (talk) 01:11, 27 March 2011 (UTC)

That would seem a bit pointless at least for Noah. According to Noah he died 350 years after the flood. Even if he was screwing a wife every hour (on average) for the whole 350 years that would only be 3068100 wives with none of them more then once over the 350 years even if the wife didn't get pregnant. One woman every hour for 350 years seems a little extreme even if he was like horny teenager all those years. Nil Einne (talk) 11:06, 27 March 2011 (UTC)

Check this. I asked a similar question last year and got some really interesting, in depth answers. It was suggested, from a rough calculation that we could build a ship large enough to carry two of every land animal (in fact we have built much larger ships) - and that the dimensions given in the Bible are not wholly unreasonable for the task on a purely volumetric level. It's the 'keeping everything alive for 40 days and 40 nights' bit and the technology level of the time that's the major problem. --Kurt Shaped Box (talk) 22:54, 26 March 2011 (UTC)

Would you need more than 2 animals of each species to repopulate the planet to avoid inbreeding? A Quest For Knowledge (talk) 23:01, 26 March 2011 (UTC)

Yes, far more. StuRat (talk) 23:06, 26 March 2011 (UTC)

Not only 40 days, but a little over a year. 40 days and 40 nights is how long it rained and then it took some time for the water to retreat. Which makes it even harder to store the necessary feed.Sjö (talk) 08:27, 27 March 2011 (UTC)

It depends on whether you mean a planetary flood, or a "known world" flood as defined for the writers of the story. It seems quite possible that a major flood could have struck the fertile crescent and Noah could have built a ship that could have held an arbitrarily large number of the local megafauna from that area. Or, even more likely, that the story could date from oral tradition about the flooding of the Black Sea (see Black Sea deluge theory) which may have been the source of many middle-eastern flood stories. --Jayron32 23:38, 26 March 2011 (UTC)

It was the Noah's Ark story that first began to turn me away from religion. My Sunday School teachers wanted to have me believe it literally, then when I questioned the logic of that, started to tell me all sorts of variations. I realised that there was an unlimited number of these variations, and that if every piece of the Bible needed that level of interpretation, one could be certain of nothing it contained. HiLo48 (talk) 00:20, 27 March 2011 (UTC)

I've never understood why people try to explain miracles and still stay within the religion! If it's not a miracle then what's the basis for your religion? Someone can't just come and say "I'm God's messenger, listen to me" - you have to prove it, by indisputable miracles, not just interesting coincidences and fancy words. Ariel. (talk) 02:11, 27 March 2011 (UTC)

And this theologian held that a belief in miracles is atheistic. What's the worth of a god who doesn't play by the rules? DuncanHill (talk) 08:11, 27 March 2011 (UTC)

This has certainly been discussed here before. APL (talk) 02:30, 27 March 2011 (UTC)

Why do people keep stating that all the animals were in twos? See Genesis 7:2-3. Three pairs to mate and one to watch.--Shantavira|^{feed me} 08:06, 27 March 2011 (UTC)

Um, it doesn't say that. The 7 is only the clean (i.e. kosher) animals (and birds). However it is ambiguous if it means 7 pairs (i.e. 14) or 7 animals (14 seems more correct). Says nothing about one to watch. Ariel. (talk) 09:05, 27 March 2011 (UTC)

Have you ever been around livestock? 6 females and 1 male works perfectly fine. Googlemeister (talk) 16:33, 28 March 2011 (UTC)

Where did all the water go? Imagine Reason (talk) 02:22, 29 March 2011 (UTC)

And where did it come from? I doubt there's enough water on Earth to flood the whole planet. A Quest For Knowledge (talk) 18:20, 29 March 2011 (UTC)

how did engineers calculate loads and stresses before the arrival of Newtonian physics and calculus?

I'm thinking Greeks, Romans -- Gothic architects who built those flying buttresses, etc. What mathematical tools did they use for their calculations? Did they build little models and then assumed the forces would scale? When building really large monuments for example, and some engineer came up with some experimental idea, how did the ancients test their ideas? Presumably there was a great deal of trial and error involved, but I usually don't hear about ancient engineering disasters. John Riemann Soong (talk) 20:56, 26 March 2011 (UTC)

There would be little sign left of most ancient engineering disasters, since the materials are likely to have been reused or eroded since then, and the rulers wouldn't be likely to record their failures in writing. One exception I know of is some ancient Egyptian pyramids which are now just piles of rubble. Another is some Easter Island statues that seem to have been abandoned before finished, due to cracks, etc. StuRat (talk) 20:59, 26 March 2011 (UTC)

Also note that, just as Newtonian physics is technically "wrong", but is still useful in many cases as an approximation of quantum mechanics and relativity, earlier models may have been "wrong", but still useful tools. And note that they don't have to understand why a particular model works, just that it works, to use it for good results. Finally, they likely just allowed more of a margin for error, if there was more uncertainty in their calculation methods, by using thicker beams, bigger stones, etc., than were actually needed. This might actually explain why some of their projects lasted so long. Roman aqueducts may not have been meant to last for thousands of years, but the calcs they made might have made them seem less stable than they really were, which they then compensated for by over-engineering them, especially once the larger margin-of-error is considered. StuRat (talk) 21:04, 26 March 2011 (UTC)

Well, I don't know of a source that deals with the topic comprehensively, but there were quite a number of Gothic cathedral projects that either fell down as they were being constructed or didn't last very long. Looie496 (talk) 21:14, 26 March 2011 (UTC)

What mathematical techniques did the ancients use? In building monumental projects did they ever make use of advanced Euclidean geometry and infinite regressions? I note the ancients talk of Diophantine equations and explored relatively intricate problems. I suppose the idea of the Riemann sum actually went way back? Did the ancients use to do something like approximate an integral by simply splitting up the problem into tiny easy to calculate approximations? Did mathematics drive engineering, or did engineering problems drive mathematics? John Riemann Soong (talk) 21:18, 26 March 2011 (UTC)

One approach which requires very little math is to construct different scaled models. If the 1/10th scale model supports 10 times the weight of the 1/100th scale model, it's reasonable to assume that the full-scale model will support 10 times that weight. If the 1/10th scale only supports twice as much weight, then the full-sized project is likely to only support twice that. Certainly not perfect, but might give them a good ball-park estimate. StuRat (talk) 21:28, 26 March 2011 (UTC)

I am not sure if that actually works like that Stu. Think about this. How would the world work if everything on earth was a 1 5,000 scale model of a different planet? What fantastic biological properties would be needed in order for 5 mile tall beings to be able to travel at speeds of 60,000 mph (equal to a human running at around 12 mph)? What kind of fantastic material properties would be needed to build a 1,000 mile high skyscraper? Googlemeister (talk) 20:15, 28 March 2011 (UTC)

The usual cautions about extrapolation apply. That is, you don't want to just measure the results off a 1/5000 scale model and assume that everything will scale up. If, however, you also make a 1/500, 1/50, and a 1/5 scale model, and they all work well, it's a good guess that the full scale model will, too. In the case of land animals, we have ample evidence that they run into size problems around the size of the largest dinosaurs. Marine animals can get somewhat larger, because their weight is supported by water, but there's still a limit, far shot of 5 miles long. StuRat (talk) 21:11, 28 March 2011 (UTC)

My understanding is that the tools of Gothic architecture and Romanesque architecture were developed with a mix of very non-general theories and practical experience. They had functional theories of arches, for example, long before they had the calculus. They worked with new ideas on smaller structures before using them on big ones. They no doubt had their failures, as well. --Mr.98 (talk) 22:12, 26 March 2011 (UTC)

And of course, they did have their documented failures, such as famously, Beauvais Cathedral, which pretty much marked the end of Gothic architecture's relationship with "bigger is better" mentalities. —Preceding unsigned comment added by 92.20.201.71 (talk) 22:20, 26 March 2011 (UTC)

Flying buttress says "Early flying buttresses tended to be far heavier than is required for the static loads involved ... Later architects progressively refined these designs and slimmed down the flyers", and it also has a "remedial" section which mentions how they were sometimes retrofitted. I think there is a much more famous example of this than the parish church in the article - there's at least one cathedral which had buttresses added after construction - but I can't remember where it is. Fonthill Abbey's tower collapsed several times, but that was because William Thomas Beckford was incredibly rich and in a hurry, and willfully negligent in designing it. 213.122.22.239 (talk) 22:19, 26 March 2011 (UTC)

Wells Cathedral's dominating interior "scissor arch", which cuts the interior space in two, was a 14th century retrofit to prevent the tower from collapsing. —Preceding unsigned comment added by 92.20.201.71 (talk) 22:29, 26 March 2011 (UTC)

(ec) Not everything in the Principia was new. I think that ancient people had a good quantitative understanding of weight, normal forces, and static friction, which are all you need to build stone structures that stay up. You don't need a concept of acceleration or even velocity. The stones are your atoms, and there are only finitely many stones, so you don't need calculus. You do need vectors, which the ancient Greeks already had. -- BenRG (talk) 22:23, 26 March 2011 (UTC)

There's also just plain old experimentation; i.e. instead of calculating what might work, you just go ahead and build it, and if it doesn't, you try something different. The Bent pyramid shows such experimentation "on the fly". When the pyramid's slope angle proved unstable, the builders simply adjusted it mid construction to make it work. There are likely dozens of long lost and forgotten pyramids which failed before the ideal angle and construction methods were tripped upon when building the Pyramids at Giza. The same is likely true of other great construction projects (castles, cathedrals, fortresses, city walls, etc.) Mostly trial and error, and then if it works repeat it... --Jayron32 23:31, 26 March 2011 (UTC)

Agreed. The spire of Lincoln Cathedral fell down in 1237 when it was less than 10 years old. It was replaced with a bigger one - said to have been 160 metres high, making it the tallest structure in the world, but that was blown down in a storm in 1548. They got the hint - it was never replaced. Another factor is that medieval masons verbally passed the tricks of the trade on to their successors in secret. Each mason therefore had generations of practical knowledge of what worked and what didn't, filed away in his head. The passing-on of secret information in this way survives symbolically in modern Freemasonry. Alansplodge (talk) 15:36, 27 March 2011 (UTC)

Many cathedrals fell down, probably churches also. Georgian houses were badly built and often fell down. Only the good ones have survived. Many buildings in the third-world fall down. 2.97.210.137 (talk) 21:44, 27 March 2011 (UTC)

Double Recombination

Hello. A wild-type female fruit fly mates with a yellow, chocolate, cut male (all traits recessive). The percentage of progeny of various types is as follows:

• 40.53% cho, y⁺, ct⁺
• 7.85% cho, y, ct⁺
• 1.84% cho, y, ct
• 0.05% cho, y⁺, ct
• 0.03% cho⁺, y, ct⁺
• 2.08% cho⁺, y⁺, ct⁺
• 8.07% cho⁺, y⁺, ct
• 39.55% cho⁺, y, ct

I determined that the ct gene is in the middle. Is the distance between y and ct 84 cM or 16 cM? How can I calculate the expected percentage of double recombinants? Thanks in advance. --Mayfare (talk) 21:44, 26 March 2011 (UTC)

I ran across [5] but for some reason I'm having trouble finding a good simple Web-based site for this sort of calculation (see LOD score).

Now to go over the genes one-by-one. First, let's work out the raw recombination fractions. 40.53 + 0.05 + 0.03 + 39.55 = 80.16% (cho+, y OR cho, y+), 7.85% + 1.84 + 2.08 + 8.07 = 19.84% (cho, y OR cho+, y+) 40.53 + 7.85 + 8.07 + 39.55 = 96.00% (cho, ct+ OR cho+, ct), 1.84 + 0.05 + 0.03 + 2.08 = 4.00% (cho, ct OR cho+, ct+) 40.53 + 1.84 + 2.08 + 39.55 = 84.00% (y, ct OR y+, ct+), 7.85 + 0.05 + 0.03 + 8.07 = 16.00% (y+, ct OR y, ct+)

Now with just the raw fractions it's pretty obvious that cho and ct are close together, with y probably closer to ct than to cho. How probably is where the finer analysis comes in. Note that there's no "84 cM" result possible - you can't get more than a 50/50 ratio. The alleles are labeled + or mutant to distinguish them, but what they are labelled doesn't actually matter. It's apparent that they started as cho, y+, ct+ and cho+, y, ct chromosomes at the beginning (the two main unrecombined types coming out of the cross.

The next thing we'd like to know is the working out of the mapping function. Kosambi's mapping function seems to be pretty popular in Drosophila; Haldane's mapping function is a simpler version that ignores that one crossover might affect the probability of another. See [6]. Now according to [7], m = 1/4 ln [(1+2r)/(1-2r) for 0 <= r < 0.5 (m = map distance, r = recombination). So 16% adjusts to 16.58 map units, 4% adjusts to 4.00 map units, and 19.84% adjusts to 21.00 map units. That gives us a basic suggestion that we have y <- 16.58 -> ct <- 4.00 -> cho. Because this is (I assume) a homework problem, this adds up nicely to y <- 20.58 -> cho as opposed to 21.00 calculated, and the double recombinants y+ ct cho and y ct+ cho+ are in fact very uncommon (the latter source gives a way to use double recombinants to work out the order more precisely). Still, a good program could maximize the LOD scores for a more precise result, and give a better idea of the confidence of the mapping. Wnt (talk) 23:21, 26 March 2011 (UTC)

Math and radiation

Is 1.76 × 10E18 50% more than 1.3 × 10E17? Looks like about 100% to me. If not what is this author talking about: [8]. 75.41.110.200 (talk) 23:15, 26 March 2011 (UTC)

It's actually 13.54 times more (or 1354%). Perhaps the number of days each burned figures into their calcs ? StuRat (talk) 23:22, 26 March 2011 (UTC)

Be careful with your "more". It's 13.54 times as much or 1254% more. -- 110.49.251.220 (talk) 11:05, 27 March 2011 (UTC)

He's saying Fukushima emitted "1.3 × 10e17 becquerels per day", and saying that "In the 10 days it burned, Chernobyl put out 1.76 × 10e18 becquerels". So he's comparing the daily rate of Fukushima vs the 10-day rate of Chernobyl. If you assume Fukushima's rate was constant over 10 days, it would have emitted 1.3 x 10e18 over the same 10 day period. So the two 10e18 cancel out, and you're left with the ratio 1.3:1.76, which is (roughly) "50 per cent more". -- Finlay McWalter ☻ Talk 23:26, 26 March 2011 (UTC)

Calling 35.4% more "roughly 50%" is rather sloppy. StuRat (talk) 00:31, 27 March 2011 (UTC)

If we take the full quote, he says "1.2 to 1.3 × 10e17". Using the lower bound the ratio is 1.2:1.76, which is 46% more. -- Finlay McWalter ☻ Talk 00:40, 27 March 2011 (UTC)

Fuse interrupted during oven use

During baking, the fuse of my apartment went off. I have no doubt that the oven is to blame. Is it secure to turn the oven on again or will the fuse go off again and again? 212.169.191.85 (talk) 23:43, 26 March 2011 (UTC)

Fuse going off may have resulted in some other electrical devices turning off, however if it is not the case it will indeed go off again ~~Xil (talk) 00:13, 27 March 2011 (UTC)

By "fuse", do you mean a circuit breaker ? A fuse only works once. If the oven was the only thing on the circuit and it made the circuit breaker pop, it's likely to do it again. StuRat (talk) 00:16, 27 March 2011 (UTC)

yes, I mean circuit breaker, and not a proper fuse. Well, but maybe, it went off because I was using the oven for a relative long time. 212.169.190.116 (talk) 00:19, 27 March 2011 (UTC)

Length of time should only matter if you are running the circuit over its rated load. Circuit breakers don't actually trip at the stated number. The greater the overage the faster they trip. If you run just slightly over, it can take a very long time (hours even) to trip. I would attempt to find out what other devices are on the circuit, because an oven should be the only device on the circuit! Then add up all the labeled power draws, and compare to the circuit breaker. Ariel. (talk) 02:26, 27 March 2011 (UTC)

Your options are to get an oven which draws less power (including spikes), switch it to a circuit which can handle more, or upgrade the present circuit. You could also replace the circuit breaker, it might just be overly sensitive (popping below the rated limit). A more risky approach is to change the circuit breaker to one which allows more power to be drawn. This can cause a fire, though, so only an electrician who knows how much that circuit can handle (and the entire fuse box) should do that. StuRat (talk) 00:29, 27 March 2011 (UTC)

It should be possible to acctualy calculate if it will happen - I believe you sum power in watts of all devices turned on and divide it by 220 (also watts) and you get how many amperes this set up produces, if it is greater than safe limit of the circuit breaker it will go off ~~Xil (talk) 01:35, 27 March 2011 (UTC)

It's not quite as simple as that, because the power demands of each device aren't constant. If all the spikes hit at once, you can have a problem with a circuit that seemed fine before. StuRat (talk) 02:02, 27 March 2011 (UTC)

I don't see why leaving a stove on for a long time would draw more current than turning it on for a short period. In fact, an already-hot oven might draw less current on average than one that's heating up from a cold start.

If it trips again, you may have a problem with your wiring. I suggest talking to the landlord about it. APL (talk) 02:28, 27 March 2011 (UTC)

See my reply a bit higher up, but basically circuit breakers don't trip immediately at their rated setpoint, there is a time * overage lag. Ariel. (talk) 02:52, 27 March 2011 (UTC)

I can understand the delay mechanism for a slight overload of an old-fashioned fuse, but how would a delay be implemented mechanically in a modern circuit-breaker? Dbfirs 07:02, 27 March 2011 (UTC)

A bimetallic strip take time to warm up.Circuit_breaker#Thermal_magnetic_circuit_breaker--Aspro (talk) 09:03, 27 March 2011 (UTC)

I have seen these inside appliances, but didn't know that they are a secondary trip in mains installations? Dbfirs 16:45, 27 March 2011 (UTC)

March 27

Is all life on earth decended from a common ancestor

According to the article Last universal ancestor, "A universal common ancestor is at least 10²⁸⁶⁰ times more probable than having multiple ancestors…"

Does this infer that the probability that all life on earth is decended from a common ancestor is 10²⁸⁶⁰ times more likely than the tree of life containing more than one starting point (i.e. more than one transition from none life to life)? It seems a startlingly large number if it implies that say plants and animals could not have evolved separately.

I think that must be the chances that every species began independently, or something silly like that. StuRat (talk) 00:17, 27 March 2011 (UTC)

That's exactly what it is stating. You would have to read the original source to understand where it comes from and what were their assumptions. Does it surprise you that plants, animals, fungi, bacteria, etc ... all have a common ancestor? Dauto (talk) 00:45, 27 March 2011 (UTC)

You mean "imply", not "infer" (very common error). I understand it to mean 10²⁸⁶⁰ times more probable than the scenario in which there was more than one starting point for life. Grammatically, it's not a great sentence. "having" is awkward... it's a dangling participle, or something like that... 86.179.115.46 (talk) 00:48, 27 March 2011 (UTC)

That figure of 10²⁸⁶⁰ suggests a degree of mathematical precision that is not realistic. The source is a print one, so difficult to check. I would prefer that the statement was softened somewhat to something like "A universal common ancestor is far more probable than having multiple ancestors…" HiLo48 (talk) 00:54, 27 March 2011 (UTC)

Looie's Law: Any probability less than 1 in 10⁶ is meaningless, because there is always at least one chance in a million that you make a mistake in working out the answer. Looie496 (talk) 01:36, 27 March 2011 (UTC)

Yea, when I hear of DNA matches to within one chance in a trillion, I always wonder what the real chance is of a false positive, when you include the chance the technician accidentally tested the same sample twice. StuRat (talk) 02:00, 27 March 2011 (UTC)

It is conceivable that there could be multiple origins of life, yet still all life shares a common ancestor. For example, there could have been a simple self-perpetuating lipid vesicle with some basic amino acid polymers, and a self-perpetuating RNAzyme, and the two became symbionts of one another. Or there might have been two original simple RNAs that merged into a single genome. But what's pretty clear is that a ribosome is found in any known kind of modern life capable of reproducing itself, and those ribosome sequences are similar by more than just chance. Wnt (talk) 02:34, 27 March 2011 (UTC)

It's likely that mitochondria are a separate life form that at some point became part of our cells, since they have their own genetic code. However, them and our cells probably both had a common origin further back. StuRat (talk) 04:52, 27 March 2011 (UTC)

Note that mitochondria have their own ribosomes - you can even tell from sequence and structure that they're the bacterial type rather than the eukaryotic type. Wnt (talk) 22:58, 27 March 2011 (UTC)

The number looks meaningless to me. They seem (based on the quote in our article - the paper is behind a paywall, so I can't read it) to have constructed several models and examined how likely our current observations are under each model. You can't convert that to the probability of each model being true without some prior probabilities and I can't see where they would get them. --Tango (talk) 14:30, 27 March 2011 (UTC)

I think that Paul Davies has suggested that there may exist life forms separate from our branch right now on Earth that we haven't managed to detect. Count Iblis (talk) 14:38, 27 March 2011 (UTC)

I suppose eventually it will come down to at exactly WHAT point do we call it life? I think the common misconception might be that there would have had to be a truly one off unique, even miraculous event which lead to all life. But I don't believe that's necessarily the case, there was probably LOTS of instances of "whatever it was" that led to life, and some of those elements might have "come together" to form the "proto-life" many times, only to "die out" later, possibly much later. All that we can be fairly certain of is that there would have been one "lineage" which all living things today can be traced back through, that's the universal common ancestor, but there could have been countless other "false starts" and "dead ends". Having said that, I wouldn't personally 100% rule out that some strange extremophile might still be found from a different original lineage, I think it's quite unlikely at this stage, but not 0%..Vespine (talk) 00:55, 28 March 2011 (UTC)

Relativity Question

Is it possible for a pulse in the following case to deviate from it's original path.

For simplicity let a spaceship is moving with 0.9c from east to west relative to the following observer on asteroid.

Dimension of the spaceship are

Width = 2 light second, Length = 10 meter (adjusted with length contraction)

An observer on asteroid (not co-moving) in the middle of east and west fire a pulse perpendicular to direction of spaceship such that after sometime the same pulse strike the longitudinal side of ship during it's passage by asteroid.

For ONBOARDB observer:

A pulse enter at one longitudinal side, travel inside for two second and then out through the other longitudinal side.

For observer on ASTERIOD:

1- A pulse will change it's direction from its original path after entering the ship

2- A pulse will travel for sometime inside ship but not perpendicular to the direction of ship

3- A pulse will start traveling again in straight line after leaving the ship but this time not on it's original straight line (which was before striking the ship). 68.147.41.231 (talk) 07:00, 27 March 2011 (UTC)Eccentric Khattak#1-420 ---- [GO]

The angle of the light beam is different with respect to the two different rest frames. The difference is given by the relativistic aberration formula. If, with respect to the asteroid rest frame, the light beam is perpendicular to the ship's motion, it will enter the ship and collide almost immediately with the back of the ship. With respect to the ship rest frame, it will be sharply angled toward the back of the ship and, again, hit the back almost immediately. -- BenRG (talk) 07:28, 27 March 2011 (UTC)

Getting rid of hazardous nuclear plant parts

If there is a decay heat even after the reactor's shutdown, the best way seems to dismantle the most dangerous parts of Fukushima plant, such as fuel rods and take them hell away or just destroy. Why this is not being done?--89.76.224.253 (talk) 09:56, 27 March 2011 (UTC)

They're too hot to take away right now — that's the whole problem. And "destroy" them how — bombing them, essentially spreading them into the air? Dump cement on them and hope for the best? These aren't prudent strategies. The latter is what you do when you've truly given up on reducing the radiation levels. Once things are "cool" enough to move, yes, they'll be dismantled, put into safe places, disposed of, cleaned up, and so forth. But you can't do that until you've gotten them to reasonable temperatures, and let some of the worst of that radiation dissipate (which is why the spent fuel was being kept in those pools in the first place).--Mr.98 (talk) 10:03, 27 March 2011 (UTC)

It takes about 5 - 10 years before you can place them in Dry cask storage. BTW, the reactors that were already shut down were just supposed to be temporary shutdowns while they did maintenance. They don't want to "destroy" or get rid of anything. They just want to shut it down, let the radiation fade, do their maintenance, then start them back up. Ariel. (talk) 11:49, 27 March 2011 (UTC)

In normal maintenance, yes. But just to be clear, it has been announced that Fukushima I will never reopen after the accidents.[9] Rmhermen (talk) 15:32, 27 March 2011 (UTC)

Well, the region will be probably way too contaminated. On the top of that, that will be a huge PR problem for the owners. 212.169.186.168 (talk) 18:52, 27 March 2011 (UTC)

Agreed. Restarting plants, of the same design and in the same location, as those that just failed so miserably, wouldn't be popular. StuRat (talk) 18:57, 27 March 2011 (UTC)

That didn't stop them at Chernobyl. While the reactor that melted down obviously wasn't restarted (there wasn't much of a reactor left by the end), the other reactors on the same site continued to operate for more than 14 years. Of course, the political situation was a little different. --Tango (talk) 20:53, 27 March 2011 (UTC)

Quite different. Still, the obviously reckless attitude of the Soviet Union towards their people's safety may have been a contributing factor in it's disintegration, by robbing it of the public support it needed when challenges from Gorbachev and then Yeltzin appeared. StuRat (talk) 22:55, 27 March 2011 (UTC)

Not wanting to be too pedantic, but Chernobyl took place on Gorbachev's watch. The handling of it was a colossal blunder on his part. It certainly did lead to vast distrust of the Soviet officials, especially amongst Ukrainians. Today its memory and experience are a major part of the post-Soviet identity of Ukrainians, Belarussians, and others in the affected area. It's also generally odd to talk about the Soviets losing public support when challenged by Gorbachev — Gorby was the Soviet Union. His efforts at reform opened up attacks from others — like Yeltsin, among others — that eventually led to the USSR falling apart. But that was not in any way Gorbachev's goal: he was trying to be a reformer, not a revolutionary. He really did believe in the USSR and Communism, at the time. --Mr.98 (talk) 00:37, 28 March 2011 (UTC)

Gorby wasn't in power when the unsafe plant was built. And, in his case, the hard-liners might have retained control if they had more of the public behind them. (And hard-liners dropping dead every few minutes helped Gorby out, too.) StuRat (talk) 04:15, 28 March 2011 (UTC)

Q:If there is a decay heat even after the reactor's shutdown, the best way seems to dismantle the most dangerous parts of Fukushima plant, such as fuel rods and take them hell away or just destroy. Why this is not being done?

This is what they will do... eventually. To do this however, they need to have electrical power restored to the equipment that extracts the rods from the core so as to place them in the spent fuel ponds. Obviously, it helps to have the working area decontaminated as well and this too will take time. Also, with the restoration of power, radioactive water (in the ponds and else where) can be passed through ion exchange material to remove the radioactive isotopes and thus bring down the exposure suffered by the recovery workers still further. If any fuel rod have partly melted in the core, they can be left in situ. Any residual heat from these will only be a small fraction of the current heat output (this is said without knowing if or how much meltdown has occurred). After the fuel rods have cooled sufficiently, they could then be shipped off (to say England) for processing. The Fukushima plant can be mothballed until such time that the radiation has decade to a level that permits the buildings on the site to be demolished and reclaimed for reuse. So in answer to your question, they can't remove the rods from the pile until they get these other things get done. --Aspro (talk) 21:40, 27 March 2011 (UTC)

It may be years before the rods are removed from the reactors. At Three Mile Island, it was six years before the reactor was defueled, although a different political climate and lessons already learned might shorten that. Japan does it own reprocessing with its own risks. (See Tokaimura nuclear accident) But it is unclear if melted-down rods covered in boron and sea salt can be successfully or economically reprocessed. Rmhermen (talk) 22:34, 27 March 2011 (UTC)

There is no mechanism for removing the fuel rods without opening the containment. These slides show the process. Opening the containment would release massive amounts of radioactive steam at an explosive pressure. There are also large quantities of hydrogen (rather explosive when in contact with air) in that steam. --Swedmann (talk) 20:29, 31 March 2011 (UTC)

Galactic rotation

Please see Talk:Andromeda_Galaxy#Rotational_velocities_must_be_wrong. I expect people here can give a better answer to the one I did. (Feel free to copy the question and my response over here if you think that's the better approach.) --Tango (talk) 12:04, 27 March 2011 (UTC)

That rotation curve looks wrong to me too. It's based on a 40 year old paper that fits observation to a polynomial. That paper indicates the possibility that a shallower inner minimum (of about 125 km/s) might also be a good fit to the observations and I think that the shallower minimum makes more sense from the dynamical point of view. A more recent source might be valuable to help solve this inconsistency. Dauto (talk) 15:41, 27 March 2011 (UTC)

The statement in the article refers to Fig. 9 in this paper. There are several data points that indicate a (narrow) dip down to below 100 km/s. This is regardless of the polynomial that is fitted to the observations (sic!). I haven't looked for newer data yet, but I point out that the dip should be located within the bulge of Andromeda, i.e. in a region that might well be supported by random motion rather than ordered rotation. --Wrongfilter (talk) 17:35, 27 March 2011 (UTC)

snow on tree flowers

So my school's trees are blooming.....and then it snowed last night, putting about half an inch on the ground. Are these flowers (that grow on trees) likely to die? =( John Riemann Soong (talk) 12:46, 27 March 2011 (UTC)

Will early bloomers likely deploy antifreeze agents in their flowers ? Some of the flowers are covered in snow. John Riemann Soong (talk) 12:55, 27 March 2011 (UTC)

I was just discussing this with my husband. We have a camellia about to bloom. At the same stage last year there was a sharp frost which resulted in the flowers being blighted and either rotting completely, or developing brown edges to them. I think it all depends on (a) the amount of frost and (b) the makeup of the flower. Some flowers are more waxy than others, and these flowers seem not to be too troubled with frosts.--TammyMoet (talk) 13:36, 27 March 2011 (UTC)

Note that flowers being covered in snow may actually insulate them from colder air. That may or may not be enough to save them, though. StuRat (talk) 19:00, 27 March 2011 (UTC)

Well the lowest temp was -0.5C. The snow later melted in the day when it shot to +5C. The snow covered the flowers for 4-8 hours though. John Riemann Soong (talk) 03:21, 28 March 2011 (UTC)

They might be OK then. Cross your fingers. StuRat (talk) 04:04, 28 March 2011 (UTC)

Speed of light question

If a car could travel as fast as the speed of light and it turned on its headlights, would it illuminate the road ahead?

[email address removed]

90.213.120.18 (talk) 18:12, 27 March 2011 (UTC)

I've removed your email address to prevent you getting spammed - we'll respond here. A car couldn't travel as fast as the speed of light, since nothing with mass can, so that is a meaningless question. A car travelling at 99.9% of the speed of light would still see the road being lit by its headlights normally. Light always appears to move at the same speed relative to you, regardless of how fast you are moving. That seems very strange, but it is true. --Tango (talk) 18:52, 27 March 2011 (UTC)

Calling it "a meaningless question" is imprecise enough to be well-nigh a meaningless statement. The core of the issue with the question is that in order to realize the premise of the question, one would have to posit that the laws of physics were different from the way we understand them now. So the answer to the question would depend heavily on how one adjusted the laws of physics to allow for it to happen. (So the question is not so much "meaningless", as it is "underspecified" - as Dauto hints, one can extract great meaning from the question if one looks at what you need to do to the laws of physics to make everything work out.) - That said, while we can't answer the question exactly as written for *at* the speed of light, we can make a slight but mathematically rigorous alteration, and look at what happens as one approaches the speed of light in the limit (mathematics). For the answer to that physically allowed and practically identical question, we find that the passengers in the car, as well as observers on the side of the road, will always see light coming from the headlights traveling at the speed of light. However, in the limit, length contraction means that the length of the road will appear to shrink towards nothingness for the passengers in the car (as the length of the car shrinks towards nothingness for observers on the side of the road). The effect of this is that in the limit, there is no "road ahead" for the passenger, as all points on the path of the car shrink to virtually the same point (that is, all points are an infinitesimally small distance away from each other). For the observer on the side of the road, the light from the headlights travels at the speed of light, but so (less an infinitesimal delta) does the car, so the light reaches a given point on the road ahead only an infinitesimal fraction of a second before the car does. Again, this really isn't "the road ahead" so much as "the road immediately in front of". Whether you call this "lit by its headlights normally" is highly dependent on what you consider to be normal. -- 174.24.203.209 (talk) 20:57, 27 March 2011 (UTC)

In short, the laws of physics are the same in every inertial frame. To the passengers in the car, light still goes at the speed of light, but the road is length contracted. However one should probably note that the passengers velocity in their frame is still zero, and they are no closer to the speed of light than when they started. So the extent to which the anyone has "approached the speed of light in the limit" is questionable. —Preceding unsigned comment added by 92.20.201.71 (talk) 22:37, 27 March 2011 (UTC)

Right, any particular observer is always at rest with respect to themselves. The thought experiment above was for what happens when the car-road relative velocity approaches the speed of light in the limit. That is, what happens when the velocity of the car approaches the speed of light for an observer on the side of the road, and what happens when the speed of the road passing under the car approaches the speed of light for the passenger of the car - which happens to be the same event, just observed from different perspectives. I may have been a little unclear by switching back and forth between perspectives. You are correct that, while observers on the side of the road see the car approach the speed of light, and thus approach zero length due to length contraction, the passengers see the car at zero relative velocity, so they don't see any length contraction of the car, thus maintaining the ample leg room one would expect from a modern subcompact. -- 174.24.203.209 (talk) 15:55, 28 March 2011 (UTC)

What Tango said is correct. I just want to add that Einstein sited that question and other similar questions as inspiration for his theoretical investigations that eventually lead to the development of relativity. Dauto (talk)

Indeed. He had a famous thought experiment about "riding" a beam of light. --Tango (talk) 20:54, 27 March 2011 (UTC)

Thanks guys, that Einstein, what a gezzer eh!90.213.120.18 (talk) 19:25, 29 March 2011 (UTC)

Tourmaline in hair care appliances

I notice a lot of heated hair styling equipment (blow dryers, flat irons, curling irons) tout the fact they are coated with or contain tourmaline. Yet the entry on the mineral doesn't give any clue to why this would be a benefit to products like that. Any ideas? --70.167.58.6 (talk) 19:27, 27 March 2011 (UTC)

The main term used seems to be 'tourmaline ceramic', which is probably a ceramic made by sintering tourmaline powder (that's a guess of course). Lots of wild claims about being a great source of negative ions - whatever that's supposed to mean, see here. Mikenorton (talk) 20:19, 27 March 2011 (UTC)

Tourmaline is a sort of gemstone because it has hardness 7. If you had sand in your hair it shouldn't scratch a tourmaline coated surface. But I have no idea if that's the real reason. Wnt (talk) 23:03, 27 March 2011 (UTC)

Tourmaline has a strong Pyroelectric effect and gives a charge separation when heated. Presumably this gives off ions in the airflow and that stops electrostatic build up in the hair. Graeme Bartlett (talk) 20:54, 29 March 2011 (UTC)

Blossoming wild shrubs in SE England

Today in the countryside of south east england I saw many example of white flowering bushes in the hedgerows. They did not have any thorns or spikes so I think that means they could not be hawthorns or sloes. They had five-petalled flowers. What could they have been? One of them at least that I looked at closely looked slightly pinkish, due to things (sorry my botanical vocabluary is not very good) adjacent to the white blossoms which were begining to burst out from the buds.

I also saw some pink blossom on what I think was a cultivated shrub, what could that have been please, at this time of year? Thanks —Preceding unsigned comment added by 2.97.210.137 (talk) 21:03, 27 March 2011 (UTC)

Could you take a photo, and upload it to flickr, imgshack or similar? It would help the botanists here id it for you. CS Miller (talk) 21:32, 27 March 2011 (UTC)

They looked like hawthorns except they did not have any spikes or thorns. The leaves must have been different. The ones I recall seeing were a simple leaf shape with a serrated edge. 2.97.210.137 (talk) 21:48, 27 March 2011 (UTC)

Perhaps a damson or a cherry plum, they're some of the earliest blossoms and can be found in hedgerows. Mikenorton (talk) 22:17, 27 March 2011 (UTC)

Almost certainly Blackthorn. A cold snap in March is called a Blackthorn Winter because it coincides with the hedges being white with their blossom. Hawthorn blossoms in late April - also known as "Mayflowers" (it hasn't realised that we changed to the Gregorian calendar a while ago). There very often aren't thorns on new blackthorn growth. I think you're unlikely to find many damson hedges in England although damson is a very close relative of blackthorn - they're both from the Prunus family. Alansplodge (talk) 00:30, 28 March 2011 (UTC)

We have damson bushes growing in one of the hedgerows on the Sussex farm where I live, and there are quite a few others in neighbouring hedgerows, but they're doubtless escapes from the damson orchards around here. Wild blackthorn, of course, is very common indeed in most parts of England. Both blackthorn and damson blossom have just begun to appear during the past three or four days hereabouts, and they fit the OP's description of the wild bush. --Antiquary (talk) 17:58, 28 March 2011 (UTC)

Except blackthorn has lots of thorns, so it's unlikely to be his shrub with no thorns or spikes! As for the pink blossom on a cultivated plant, very likely to be a cherry, they are in blossom right now here in Sussex. DuncanHill (talk) 18:05, 28 March 2011 (UTC)

Prunus avium, the wild cherry, occurs in hedgerows around here, and is in blossom now. DuncanHill (talk) 18:14, 28 March 2011 (UTC)

angular momentum in beta decay

Fermi beta decay is usually done without accounting for spin. The relevant term is the DOS of the final state, so:

If a spin-S particle decays into two particles spin s₁ and s₂, how does one account for this in the DOS of the final state. Is it just increased by a factor (2S+1) as this is the number of ways of aligning s₁ and s₂ to make s₁ + s₂ = S. (Is that right?) —Preceding unsigned comment added by 92.20.201.71 (talk) 22:28, 27 March 2011 (UTC)

I don't know about Fermi beta decay, but normal beta decay makes 3 particles electron, antineutrino and whatever the decay product is. Graeme Bartlett (talk) 07:37, 28 March 2011 (UTC)

Fermi beta decay and normal beta decay are the same thing. Dauto (talk) 13:58, 28 March 2011 (UTC)

I assume that by DOS you mean density of states. Yes there is a factor of (2S+1) when the density of states is calculated. I don't know what you mean by "Fermi beta decay is usually done without accounting for spin." As far as I know, spin is always taken into consideration. Dauto (talk) 13:58, 28 March 2011 (UTC)

Movement inside the body cavity

When I "suck it in" -- what is "it" and where does it go? I find even with a full breath in my lungs I can still "suck in" my gut a fair bit (though less), so it can't all be lung expansion/contraction. The Masked Booby (talk) 22:41, 27 March 2011 (UTC)

External intercostal muscles can flare (lift, like a bucket handle) the ribs to increase the volume of the thorax. If the epiglottis is closed then air cannot enter the lungs (to balance the pressure difference between the newly-reduced-pressure thorax versus the outside atmosphere). If the diaphragm is relaxed, the relatively-mobile abdominal contents have greater pressure from outside than the thorax, thereby tending to move them into the thoracic cavity. Abdominal muscles, including the rectus abdominis and obliques (abdominal internal oblique muscle, abdominal external oblique muscle) can also play a role in pushing abdominal contents up against the diaphragm. -- Scray (talk) 01:06, 28 March 2011 (UTC)

Pinhole glasses v. sunglasses

I do not like wearing sunglasses as they make colours look grey or other tints. Do pinhole glasses reduce the amount of light while still letting you see colours? Are they suitable to use as sunglasses? Thanks 2.97.210.137 (talk) 23:02, 27 March 2011 (UTC)

Only colored lenses change the color. You need to get photo-grey sunglasses. They shouldn't change or reduce the color. (Except that colors in shadows might not be bright enough to distinguish anymore, but that's also true of pin-hole glasses, which will also reduce peripheral vision.) StuRat (talk) 23:11, 27 March 2011 (UTC)

Depends on what you're doing. If you're just looking around, then sturat is right. I've used (photo.grey) for many years in tropical sun (Guatemala) and they have only minimal effect on colors. but if you're doing something that requires only a narrow field of vision, such as painting pictures in sunlight, then color perception is important and pinholes might be better.Note also that photo grey get darker in sunlight and lighter in shade. very convenient but they are usually more expensive.Phalcor (talk) 05:13, 28 March 2011 (UTC)

March 28

Melting point of graphite: Lower in Japan?

This article says that graphite plugs in the Kukushima Daichi reactors "start to melt" at 350 C. That seems implausible, since graphite is used in various applications in a solid state at much higher temperatures, as in arc lights. Could graphite really melt at 350 Celsius? The Graphite article does not appear to state a melting temperature. Edison (talk) 00:05, 28 March 2011 (UTC)

That article actually says 350°F, which is even lower (177°C). That does seem to be a mistake. According to this article: [10], graphite melts (technically it sublimes, or turns to vapor) at around 3652-3697°C. This assumes normal atmospheric pressure though, could that be the difference ? StuRat (talk) 00:29, 28 March 2011 (UTC)

My guess is the "graphite plugs" are not made of pure graphite, but have something else in them which is what does the melting. Our carbon article says that carbon in normal atmospheric pressures doesn't even HAVE a melting point as it sublimates at about 3900 K. Even given that, 177 deg C still sounds wrong. Vespine (talk) 00:36, 28 March 2011 (UTC)

Another thought, could the plugs come loose, due to contraction and/or expansion ? They wouldn't need gravity to pull them out, if water can then get underneath them and turn to steam. This certainly isn't "melting", but some reporter could possible get confused and call it that. StuRat (talk) 01:24, 28 March 2011 (UTC)

Yep. my book (columbia enc.) gives carbon (12 that is)melt.pt 3550 C. gas off 4827 C. definitely sounds like journalistic error or typo.Phalcor (talk) 04:01, 28 March 2011 (UTC)

Carbon-graphite impregnated epoxy resin sealing rings are widely used in industry and the epoxy breaks down around 350 deg... and a few degrees less if it is wet heat. They don't melt, they become soft and crumbly and start to smell very unpleasant. Fairwinds (oh the irony) have posted a diagram of the projected radioactive leak path.--Aspro (talk) 10:11, 28 March 2011 (UTC)

Is that 350° F or 350° C ? In either case, it seems rather reckless to use a material so poorly suited to withstand the maximum temperature. StuRat (talk) 20:57, 28 March 2011 (UTC)

350F. In a boiling-water reactor, it is theoretically impossible for the temperature to get above 212F, so a hundred-degree safety margin would be plenty. Unfortunately, theory and practice are busy disagreeing right now... --Carnildo (talk) 22:49, 29 March 2011 (UTC)

Only at atmospheric pressure. At around 3.5 atmospheres, the boiling temp goes up to 350° F (do reactors explode before they reach that pressure ?). Not allowing for the possibility of water leaking out and/or becoming pressurized in the reactor core seems rather negligent. Their "theory" appears to be that nothing will ever go wrong. StuRat (talk) 23:03, 29 March 2011 (UTC)

car (celebrities registration of)

can i register a car under a fake name like celebrities do? — Preceding unsigned comment added by Wdk789 (talk • contribs) 05:43, 28 March 2011 (UTC)

What country are you in? Anyway, do celebrities do this, or register the car under their agent's name? I've made the title more descriptive. CS Miller (talk) 06:11, 28 March 2011 (UTC)

us — Preceding unsigned comment added by Wdk789 (talk • contribs) 07:15, 28 March 2011 (UTC)

If you're in the U.S. no. you need identification proof/documentation.190.148.135.138 (talk) 07:25, 28 March 2011 (UTC) reformatted last response. Richard Avery (talk) 08:01, 28 March 2011 (UTC)

As of a decade ago (last time I had to care), it was possible in California for someone other than the legal owner of a car to submit the registration paperwork provided that the legal owner signed the forms and all other necessary documentation was provided. You have to show up in person to get a driver's license, but someone else could submit registration paperwork. Not sure if that is still the case, or whether different rules apply in different states. Dragons flight (talk) 08:51, 28 March 2011 (UTC)

In the UK a vehicle is registered at the DVLA in the name of its "Registered Keeper", who need not be the owner, but is responsible for paying the Vehicle Excise Duty on it, ensuring it's ensured, etc. AndrewWTaylor (talk) 19:45, 28 March 2011 (UTC)

Do you really need the driver's license? What if you don't drive your own car yourself? Can a car be registered at the name of company? 212.169.184.189 (talk) 02:18, 29 March 2011 (UTC)

Pressurized storage of liquids

Suppose we have a 1 litre container of water (or any other drinkable liquid). Is it theoretically possible to pressurize the container to, say, 300 ml capacity so that this smaller container would still be able to contain 1 litre of water (something like black hole)? Specifically, is there any material capable to withstand the associated water pressure while being flexible enough to allow the needed external pressure?--89.76.224.253 (talk) 10:05, 28 March 2011 (UTC)

It's doubtful. You would need a pressure of at least 7.333×10^9 Pa (Hope I did the math right.) Which is a pretty immense pressure. But since the bulk modulus of water is non-linear with pressure, the real pressure is probably much much higher. I can't find info on how non-linear. Ariel. (talk) 10:57, 28 March 2011 (UTC)

I remember seeing an old film clip about what must have been the Bathysphere or Benthoscope returning from the deeps after a test run. When its hatch bolts were gingerly loosened, a huge quanity of water gushed out under pressure, seemingly several times the volume of the sphere. So, yes. In fact anyone could do this - throw a 1l weighted plastic bottle of water into the deep ocean, and when it eventually reaches the bottom it should be considerably crushed. 92.15.14.99 (talk) 11:56, 28 March 2011 (UTC)

Nah, that's incorrect. Even at the bottom of the ocean water density increases by just a few percent. Dauto (talk) 14:46, 28 March 2011 (UTC)

Got any evidence for that please? 92.15.14.99 (talk) 15:10, 28 March 2011 (UTC)

Properties of water#Compressibility. DMacks (talk) 15:35, 28 March 2011 (UTC)

I saw what I saw. The Challenger Deep is about 11km deep. 92.15.14.4 (talk) 20:24, 28 March 2011 (UTC)

You saw what you saw and you don't know what you saw. At that depth the density will still be only a few percent higher. Dauto (talk) 20:44, 28 March 2011 (UTC)

Probably an optical illusion. A thin curtain of water mixed with air to form bubbles might look like a lot more than it really is. StuRat (talk) 20:54, 28 March 2011 (UTC)

On reflection it may have been the air inside that became very compressed and forced the water out, and the sphere wall could have been thinner than I expected. 92.29.126.172 (talk) 13:41, 29 March 2011 (UTC)

Now you're making sense. Dauto (talk) 13:56, 30 March 2011 (UTC)

Methanopropylenes

Hi. I recently had a dream about "methanopropylene" (I know, I'm so weird). The name could refer to either a propylene plastic impermeable to polar methano-molecules such as methanol in gaseous or liquid form and to chemicals produced by methanogens, or polymers derived from methanols. The only Google item I could find relavent to my topic, in fact the only website in existance remotely related was this, but any idea what type of chemical methanopropylenes would constitute and what potential they have? Thanks. ~AH1^(TCU) 11:46, 28 March 2011 (UTC)

School time lays long in the past and probably they also changed the way to name things, but when I hear of methanopropylene I think of H₂C=C(CH₃)-CH₃, that is propylene where the middle H is substituted by CH₃. I know the CH₃ would be in the middle for otherwise the longest unforked C-chain would consist of 4 C-atoms and the basic name would be derived from butan and it would be butylene. 77.3.138.240 (talk) 13:17, 28 March 2011 (UTC)

That would be methylpropylene (IUPAC name methylpropene); the methano- prefix isn't very common, but it does show up in the names of some amino acids, like 2,4-methanoproline and 2,4-methanoglutamic acid, see [11]. In these cases, methano- refers to a bicyclo system with a cyclopropane ring as part of it; "methano-" means you have bonded one carbon to two neighboring carbons in the main, named chain or molecule. Under that derivation, methanopropylene would likely be an alternate name for Methylcyclopropane. --Jayron32 14:19, 28 March 2011 (UTC)

So that methano-ethane would be equivalent to cyclopropane? 77.3.138.240 (talk) 14:42, 28 March 2011 (UTC)

Actually, probably methanoethylene, as the compound would be formed from ethylene (IUPAC name ethene) rather than ethane, which is pretty much unreactive. As I said above, the methano- prefix is non standard, and you wouldn't find the term in any IUPAC-standard name, AFAIK. --Jayron32 00:07, 29 March 2011 (UTC)

time 2

in my March 26 question about "time", most of the answers talk about watching a distant clock move (pass time) at some multiple of my clock. Wouldn't that mean that as I approach the clock the light is getting to me faster than c? —Preceding unsigned comment added by 165.212.189.187 (talk) 13:45, 28 March 2011 (UTC)

The light is not approaching you (i.e. as measured in your frame) faster than c. However, if there is another observer who sees you moving toward the light source, then because in his frame the speed of light is also c (no contradiction here because time is not absolute), he would see that the distance between where in his frame the light front is, and where you are, is shriking faster than c, however this is not a relative speed, so there is no contradiction with relativity here.

I think it would be a good exercise for you to work out this in detail and derive the Lorentz transform equations, it is quite easy to do. Count Iblis (talk) 14:17, 28 March 2011 (UTC)

So what explains me observing the minute hand of the distant clock move faster than mine, does mine slow down? —Preceding unsigned comment added by 165.212.189.187 (talk) 15:13, 28 March 2011 (UTC)

Dominant effect: As you are approaching the clock, the time needed for the light to travel from the clock to your eyes is becoming less. So, the time delay diminshes as a function of time, making the clock look like moving faster. This is just the classical doppler effect. There is then a small relativistic correction to this because of time dilation. Count Iblis (talk) 16:21, 28 March 2011 (UTC)

Cow dung to absorb gamma rays

A leading newspaper from India, quoting a physics professor, says that "Cow dung, in fact, can absorb all the three rays -- alpha, beta and gamma... If the outer walls of houses are coated with thick layers of cow dung, it will absorb the gamma rays and in turn people would be safe". Does anyone know how thick should be be this cow dung coating to make people inside the house safe(in the context of a radiation accident). 14.139.128.14 (talk) 13:46, 28 March 2011 (UTC)

Dung consists mostly of water and carbon of some form. I estimate that about 10cm would be sufficient to protect from neutron radiation (as long as you can keep the dung from drying). As for alpha and beta radiation, I cannot imagine any building wall, be it concrete, wood, glass or plastic that can be thin enough to not also protect from this kind of radiation. The best protection from gamma rays is dense matter with heavy nuclei. I doubt heavily that dung can protect from it, unless several meters thick. Any shielding whatsoever could not protect from radioactive materials coming in with air, food and water. To put it short: I think that's plain nonsense. If you would use pig dung instead, you could at least assure that no one gets hurt by radiation inside the building because everyone would have left due to the smell. 77.3.138.240 (talk) 14:27, 28 March 2011 (UTC)

Concur with the above, cow dung would not offer more protection then soil of the same thickness against gamma radiation. I smell BS. Googlemeister (talk) 16:20, 28 March 2011 (UTC)

Very, very literally BS. SDY (talk) 19:12, 28 March 2011 (UTC)

Also bogus/nonsense claims? DMacks (talk) 16:25, 28 March 2011 (UTC)

The article is nonsense. And on top of that direct radiation is not something anyone needs to worry about unless they are building (or working in) a reactor. Even if cow dung was a miracle shield, and blocked radiation 100% it would be worthless. The problem is ingesting radioactive elements - the resulting radiation is internal, not external. Ariel. (talk) 21:47, 28 March 2011 (UTC)

Psychology of spending

I wonder if there's a name for the thing I'm thinking about. I see a small one-serving pack of M&M's on the shelf at the store selling for $1.35 and could easily imagine people having no problem with that and buying it. But if I imagine myself trying to sell that pack for that much as an individual or even buying the same from another individual, that price feels too high. But it's the same exact product. It's not that it's used- I get that there's probably an association between individuals and used objects, but I still get this feeling if it's still sealed. Is there a name for the feeling that if it's a real business doing the selling, the higher prices than what I'd ever pay an individual are OK? 20.137.18.50 (talk) 14:29, 28 March 2011 (UTC)

In the same vein, some people (i.e. me) prefer buying electronics or appliances at a large retail supplier to buying them at a small independent one (unless the price premium is TOO great), despite the fact that the products are identical and would be under the same warranty from the same manufacturer. It's the same for brick-and-mortar vs online stores. I'd be interested to read the replies. Zunaid 15:13, 28 March 2011 (UTC)

If what you describe amounts to "I'd pay $1.35 for these M&M's from a reliable retailer like MegaLoMart, but if I were buying them off a dodgy geezer like 20.137.18.50 I'd expect they're either rubbish or hooky, so I'd want a major discount" then that would be Halo effect. Similarly one can buy stuff from Fortnum and Mason that's much the same as you'd get from Tesco, but at a significantly higher price, which I think is called "brand premium". -- Finlay McWalter ☻ Talk 15:14, 28 March 2011 (UTC)

Expanding on that, I'd also point to information asymmetry, The Market for Lemons, and the notion of "the bad driving out the good" in a market. If a random stranger offers to sell me candy, I don't know anything about him, his storage practices, his inventory turnover, or his approach to hygiene. He may or may not have an incentive to keep me happy as a customer; is he interested in repeat business, and is there any way for me to assess that? Because I don't have access to all that information – whereas I can make (better) guesses about it for a regular retailer – I am apt to discount the perceived value of the candy. TenOfAllTrades(talk) 16:43, 28 March 2011 (UTC)

The stuff you can buy in Harrods is the same as what you can buy elsewhere at cheaper prices. Same with many other shops. 92.15.14.4 (talk) 20:10, 28 March 2011 (UTC)

Physics of insect wings

Can someone can translate the equations from here to math equations (you know, <math>) on Wikipedia so I can include them in the article, Wing (insect)? Bugboy52.4 ¦ =-= 17:04, 28 March 2011 (UTC)

$h={\frac {g(\Delta t^{2})}{2}}$ and $\Delta t^{2}=\left({\frac {2h}{g}}\right)^{\frac {1}{2}}$ are what the first two say, but surely it doesn't mean that? I think Δt is intended in the second one. (I'm also not sure how to do bigger brackets than one line's worth.) Changed. Grandiose (me, talk, contribs) 17:16, 28 March 2011 (UTC)

You're right. The units are inconsistent. The equation should read $\Delta t=\left({\frac {2h}{g}}\right)^{\frac {1}{2}}$. Dauto (talk) 17:38, 28 March 2011 (UTC)

Thank you! And one more thing, if you can, there are a few mentioned after about elasticity, can you do those two? Bugboy52.4 ¦ =-= 17:41, 28 March 2011 (UTC)

Which page? Looks like it might be on 78 or 79, which aren't available on that preview (for me, at least). [The first two equations are straightforward rearrangements of each other; might not both be useful depending on context.]Grandiose (me, talk, contribs) 17:53, 28 March 2011 (UTC)

79 I believe. Bugboy52.4 ¦ =-= 18:05, 28 March 2011 (UTC)

I wasn't able to access page 79 in that edition using Google Books (too many people tried, perhaps?), but I was able to access the second edition of that book on Amazon, and searching for "elasticity" led to this equation (eq. 6.11, in section 6.5 "Elasticity of Wings") for the energy E stored in the stretched resilin:

$E={\frac {1}{2}}{\frac {YA\Delta \ell ^{2}}{\ell }}$

Is that what you needed? -- Scray (talk) 00:15, 29 March 2011 (UTC)

Wonderful, what pages can you get with Amazon, I'm going to look more to find those pages. Bugboy52.4 ¦ =-= 01:36, 29 March 2011 (UTC)

Just search for the book, then "Look inside", and search for a term. You can choose the hit you want to view and you'll see a couple of adjacent pages. No doubt they'll be on to you if you access too many... -- Scray (talk) 01:59, 29 March 2011 (UTC)

Headlights of a spaceship if turned on relative to two different observers

Lat a spaceship with its remote controlled headlights is moving with 0.9c relative to observer on asteroid who is not co-moving.

1- Onboard observer turned on the headlights of his spaceship with the help of a remote control device by sending a signal (pulse) from the back of ship to it's front

2- While due to the high speed of ship a signal (pulse) will still be moving inside the ship relative to asteroid observer.

Thus would the headlights be turned on at the same time for both onboard and asteroid observers if the perception distances are ignorable

Perception distances: The distance travelled by headlight

b/w headlights and onboard observers AND b/w headlights and asteroid observer 68.147.41.231 (talk) 17:52, 28 March 2011 (UTC)Eccentric Khattak#1-420------[GO]

See relativity of simultaneity for a discussion about this kind of thing. --Tango (talk) 22:17, 28 March 2011 (UTC)

I asked above in regard to sub section " The train and the platform thought eperiment" of the article. I got unsatisfactory answers from forums therefore still its difficult for me to the fathom.

The same senario but the other way

Let aforementioned remotely control spaceship is moving with 0.9c relative to stationary observer on asteroid. Onboard observer sends a stoping signal (pulse) from the back of ship to it's front with the help of a remote control device.

1- For onboard observer: A pulse would hit the front and thus stopped the ship earlier than asteroid's observer

2- While due to the high speed of ship a pulse will still be moving inside the ship relative to asteroid observer

Since a pulse would arrived the front at two different timing relative to aforementioned observers therefore would the ship be stopped at the same time at the front of asteroid for both observers.

The purpose of this post is to share knowledge and shouldn’t be considered offensive.68.147.41.231 (talk) 00:15, 31 March 2011 (UTC)Eccentric Khattak#1-420

Vanadium oxidation

Does it make the pentoxide or vanadium(IV) oxide? --98.221.179.18 (talk) 18:35, 28 March 2011 (UTC)

Vanadium oxide indicates both the (4+) and (5+) oxides, along with several others, as well as the possibility of non-stoichiometric oxides, indicating multiple oxidation states within a single crystal lattice. --Jayron32 00:03, 29 March 2011 (UTC)

Game theory: paying ransom

Imagine that something worth $1000 has been stolen. The thief demands $900 from you. You thing: OK, I pay, it's still $100 on my favor. After you pay, the thief demands $900 again. Do you pay again? It's still $100 cheaper than buying anew. (the first $900 are now sunk costs). Quest09 (talk) 18:45, 28 March 2011 (UTC)

If your country takes your taxes but still refuses to protect your property rights then you should consider hiring Juri Kalashnikov instead of paying indefinite ransom . (Millions for defense, but not one cent for tribute) 77.3.138.240 (talk) 19:22, 28 March 2011 (UTC)

What's missing from this apparent paradox is an assessment of risk. That resolves the paradox.

In the first scenario, let's say you were 95% certain that the ransom would be honored. That puts you at a $950 'expected' payout on your $900 investment.

During the second ransom, you know that your original assessment of the risk was wrong. Now you're much less sure that the ransom will be honored. Let's say now you're only 25% certain that they'll honor the second random after not honoring the first ransom. That gives you a $250 'expected' payout on a $900 investment. Clearly you should walk away.

In other words, the sunk-cost doesn't carry over from one 'round' to the next, but previous 'rounds' do change your expectations of how the other party will act.

(This all assumes that there's no better options available. For example, If you believe that there's a 50% chance that law enforcement can retrieve your item at no cost to you, then that is the correct choice because it offers an expected $500 profit.) APL (talk) 19:39, 28 March 2011 (UTC)

(ec) 50 percent chance of law enforcement? "Har Har Har" Excuse me, from what I personally experienced in Germany, my advice is: forget about it. 77.3.138.240 (talk) 19:50, 28 March 2011 (UTC)

As an alternative, the money that would have been spent on the ransom could also be spent in hiring private detectives and/or posting a reward. If the payment is contingent upon the item being recovered, then you are guaranteed that some effort will be made to recover the object, unlike with police, who may not much care about such a tiny item, since they won't get a share. StuRat (talk) 22:30, 28 March 2011 (UTC)

I wouldn't say your assessment of the risk was wrong. If you had thought there was a 100% chance they would give you your money, then you would have been wrong, but just because the 1 in 20 chance happened doesn't mean it was more likely than 1 in 20. We're not talking about a random occurance, anyway, we're talking about a definite thing (either they are planning to give you your money or they aren't - they aren't going to toss a coin to decide), just one that you have incomplete information about. Getting additional information doesn't mean you made a mistake before. --Tango (talk) 22:26, 28 March 2011 (UTC)

If you were aware of the idea of sunk costs then you could, but the kidnappers refusal to return the goods the first time would give you a lot of information about them, so you would probably think they would repeat the same trick again, and refuse. A clever thief would ask for a lesser amount the second time, to tempt you. I think J. Paul Getty was probably right about refusing to pay a ransom for John Paul Getty III. 92.15.14.4 (talk) 20:01, 28 March 2011 (UTC)

Isn't the original theft already a "sunk cost"? Would you trust a random person, who admits that he is a thief, who offers to sell you $1000 worth of goods for $900? Additionally, of course, one worries that by doing business with a scam artist, he is branded as a sucker - just like buying something from a spammer. Conversely, an attack on the thief that succeeds has substantial prestige value. Wnt (talk) 01:44, 29 March 2011 (UTC)

"Conversely, an attack on the thief that succeeds has substantial prestige value." What kind of attack did you have in mind? How would this help you get your stuff back? Its usual to do the paying of the ransom secretly, so being seen as a sucker or gaining prestige would not apply. 92.29.126.172 (talk) 13:51, 29 March 2011 (UTC)

The secret might get out, or that same thief might target you again, or tell one of his thief friends about it, who then target you. So, the cost of the increased future likelihood of theft must be considered in the equation. The original theft could even be a test case, to see how you react to ransom demands, so the thief will know whether to go ahead with kidnapping your kids, as planned. StuRat (talk) 18:19, 29 March 2011 (UTC)

In a law-abiding society one might pay the thief with an exploding dye-pack and a police pursuit, or in a less lawful one, with a pipe bomb; either way, the ensuing damage to the thief is apt to become known and dissuade further attacks. Wnt (talk) 03:43, 30 March 2011 (UTC)

Never heard of revenge or vendetta? 92.15.1.33 (talk) 16:20, 30 March 2011 (UTC)

Smart kidnappers know not to return "the goods" (if at all) until they have completely gotten away, by telling you where to go pick it up. They might also use an innocent "patsy" to pick up "a package somebody left for me". StuRat (talk) 05:05, 30 March 2011 (UTC)

You learnt that off the movies. 92.15.1.33 (talk) 16:20, 30 March 2011 (UTC)

And so did the smart kidnappers. StuRat (talk) 16:24, 30 March 2011 (UTC)

Question regarding extraterrestrial radio pulses

I was watching an interview with Arthur C. Clarke (co-writer of 2001: A Space Odyssey) before the movie's 1968 premier in which he said:

"In the last few weeks there has been tremendous excitement among the astronomers over the extraordinarily precise and rhythmic radio pulses coming from the direction of a point between Vega and Altair. Which may yet turn out to have a natural explanation, but its periodicity and characteristics are so extraordinary that no explanation as yet seems very feasible."

I'm picking up some references to 1967 signals picked up from Vega and Altair...but whatever happened? Have these been explained? Thanks. WordyGirl90 19:44, 28 March 2011 (UTC)

The timing and location look right for it to refer to the first pulsar to be discovered. AndrewWTaylor (talk) 19:49, 28 March 2011 (UTC)

There was the Wow! signal But that was in 1977, not in 1967. Googlemeister (talk) 19:50, 28 March 2011 (UTC)

The LGM-1 was from 1967 and is probably what Clarke was talking about. Googlemeister (talk) 19:56, 28 March 2011 (UTC)

That would have to be it...correct constellation, too. Thanks :) WordyGirl90 20:19, 28 March 2011 (UTC)

Interface for communicating with blind people

Hi all. I'm writing a short novel where the protagonist, who is blind, uses a technological device that accurately scans his surroundings and sends this information back to him. The problem is that I can't imagine exactly how I would transmit this information to the blind user. Using a synthetic voice would interfere with 'real', useful sounds. Maybe using a pad in the hand with vibrations/pressure/heat that conveys this information? Please, help me with my brainstorming! Thank you very much. --Bliviinc (talk) 21:49, 28 March 2011 (UTC)

There were experiments that had a head-mounted grayscale camera. It converted the image to sound by scanning a line at time. Left-to-right was represented by low tones to the left, and high tones to the right; black was quiet for that frequency, white was loud. I'm not sure how the start of each frame was represented; lets say a click.

Thus

• A vertical line white line on a black background is a solid tone; lower in tone to the left
• A horizontal line is sudden burst of white noise, the rest is silence. The closer to the click the higher up the line is.
• A top-left to bottom-right line is a rising tone
• A top-right to bottom-left line is a descending tone.

From memory, the experiments were successful enough for the subjects to navigate using the device. I'm not sure if there were different sounds (views) for each ear or not. It probably started with the same tones to each ear if there was eventually two cameras/tones. CS Miller (talk) 22:08, 28 March 2011 (UTC)

How about a device that has little bumps that raise up to form the equivalent of a black and white image of the room ? There already exists a device which raises bumps to form Braille letters. As an alternative, instead of the bumps being raised based on the darkness/lightness of the object, they could be raised or lowered based on distance from the device, to created a 3D image of the room, at perhaps 1/1000th the depth of the room (it would be nice if this ratio was adjustable for large and small rooms). Since the blind person would be constantly running their hand over it, it should be washable, as it would accumulate oils and dirt. Perhaps a removable flexible surface on top could be washed or replaced, as needed, with the expensive "guts" remaining dry. StuRat (talk) 22:20, 28 March 2011 (UTC)

I recall a TV show featuring someone blind from birth who had developed his own sense of echo location, making his own audible clicks. If someone has been blind from birth, their senses have had a longer time to compensate for the loss of sight. PЄTЄRS J V ►TALK 22:25, 28 March 2011 (UTC)

I recall a similar TV show. I remember a young boy finding and identifying a fire hydrant by clicking. --Tango (talk) 22:48, 28 March 2011 (UTC)

Personally, I'd think the smell of dog pee might be a clue. :-) StuRat (talk) 22:53, 28 March 2011 (UTC)

This site: http://www.seeingwithsound.com/ they have a demo and you can practice playing tic-tac-toe by sound alone. Ariel. (talk) 22:58, 28 March 2011 (UTC)

That's a heck of a lot less challenging than navigating through a room, though. StuRat (talk) 23:00, 28 March 2011 (UTC)

The tic-tac-toe is just a demo for sighted people. The device is actually used for navigating rooms. Ariel. (talk) 23:20, 28 March 2011 (UTC)

A device far cooler then using sound already exists. Vespine (talk) 23:04, 28 March 2011 (UTC)

Great ideas!! I particularly like your idea, StuRat. Apparently, a big problem blind people face and that most "navigating aid" devices can't detect are slopes and steps, instead of massive obstacles. How would you communicate those to the user with your bump-grid? --Bliviinc (talk) 23:40, 28 March 2011 (UTC)

Well, if the difference in height of the bumps wasn't enough when looking at the whole staircase or slope, perhaps it could be focused on an individual step or section of the ramp, and would automatically scale the depth so that the closest objects in the view had bumps 100% up, and those farthest away in that view would have bumps 100% down. StuRat (talk) 23:54, 28 March 2011 (UTC)

I think that the main problem is detecting those on the fly, without having to stop and focus on them. Maybe additional, always-zoomed bumps? --Bliviinc (talk) 23:59, 28 March 2011 (UTC)

Just to be explicit, the bump-grid concept is actually the basis of the device that Vespine pointed to above. Looie496 (talk) 00:01, 29 March 2011 (UTC)

I also once read about a blind guy who could use echo like a bat, but I suppose that while all people can use echolocation to some extent only chosen few can use it to navigate. How about full body suit that warms or puts pressure on persons skin if it senses an obstecle right in front of that spot and the pressure/warmth varies in strenght depending on how close the object is? Also assuming blindnes isn't caused by brain damage artifical eyes or neural interface could work (we're talking sci-fi short story, right?). ~~Xil (talk) 00:20, 29 March 2011 (UTC)

Actually, no, they already have that. But it's black-and-white, low res, and requires surgery and training, so not ready for mass-marketing yet. StuRat (talk) 00:31, 29 March 2011 (UTC)

You mean artifical eye? I am aware, but the technology has only just started to develop and there seems to be some promise in it. OP said it is for a story, but hasn't given any further details on setting of his story, so I am assuming it is sci-fi i.e. that it dosen't need to exist or must be producable with current technology ~~Xil (talk) 01:13, 30 March 2011 (UTC)

Wikipedia has an article about corner reflectors. -- Wavelength (talk) 15:08, 29 March 2011 (UTC)

How does that relate to the question ? StuRat (talk) 18:16, 29 March 2011 (UTC)

Radar is a technological device, and staircases have corners. -- Wavelength (talk) 19:25, 29 March 2011 (UTC)

So you're suggesting use of radar ? I don't think this question is about getting the room shape info into a device, it's about conveying that info to a blind person. That's the tricky bit. StuRat (talk) 20:39, 29 March 2011 (UTC)

That information can be conveyed by audible signals. (See Geiger counter.)

—Wavelength (talk) 21:48, 29 March 2011 (UTC)

[I am correcting my punctuation. -- Wavelength (talk) 21:50, 29 March 2011 (UTC)]

But how, precisely ? Would you point a beam in various directions and know the distance in that direction from the frequency of the sounds ? Such a system would work, but would also be very slow to use. I have difficulty imagining how a brain not designed for echo-location could use hearing to instantly "see" an entire room in the way that our eyes do. StuRat (talk) 05:02, 30 March 2011 (UTC)

Our Britches (monkey) article is about a monkey, liberated by the ALF, whose eyes had been sewn shut at birth and he had been made to wear a "substitute sensory device". Comet Tuttle (talk) 18:36, 29 March 2011 (UTC)

It says "sonar device", sounds like echolocation again, it does though mention the device being version of "sonicguide", I googled it didn't find anything in particular, but it seems to be sound emiting device attached to cane, here's a similar device: [12] ~~Xil (talk) 01:13, 30 March 2011 (UTC)

March 29

Rendering Equations

I've been trying to lean how to render equations instead of having to ask. Why doesn't this render png? On my browser it appears as html.Bugboy52.4 ¦ =-= 03:34, 29 March 2011 (UTC)

${\text{Work}}=F_{av}\times d={\text{2Wd}}$

How about this:

${\text{Work}}=F_{av}\times d={\text{2Wd}}\,\!$

Courtesy of Help:Math#Forced PNG rendering. DMacks (talk) 03:48, 29 March 2011 (UTC)

What about

Failed to parse (syntax error): {\displaystyle \text {E}=\text {mgh}=0.1\times980\times10^{−2}=0.98\text {erg}}

Its not rendering, what am I doing wrong? Bugboy52.4 ¦ =-= 03:53, 29 March 2011 (UTC)

The minus sign in your "-2" is not an ordinary minus sign, it is some sort of fancy dash. The math mode parser does not know how to handle it. If you use an ordinary minus sign, it will render:

${\text{E}}={\text{mgh}}=0.1\times 980\times 10^{-2}=0.98{\text{erg}}$

Looie496 (talk) 04:22, 29 March 2011 (UTC)

Someone please copy this to WP:VPT so the developers know about it. 99.2.149.161 (talk) 17:30, 29 March 2011 (UTC)

The developers will tell you that the TeX parser is fully compliant - and that this behavior is correct. You have entered invalid syntax that is not a valid equation. Unicode (and therefore MediaWiki and its TeX parser) specifies a different interpretation for − and - though the glyphs look similar in most standard Windows, *nix, and Mac fonts. (Consider reading the characters in a hex editor). Read about character duplication in Unicode, which is slightly technical. Nimur (talk) 19:41, 29 March 2011 (UTC)

A test where E. Coli is not exceeding 3/g ???

Under Australian legislation, ready-to-eat meat products must not have E.coli exceeding "3/g"
But it doesn't specify what the unit of measurement is, 3 what???
3 Colony-forming_units?
3 single Bacterium?
^{I have contacted the Food Authority and they will come back to me within 10 days. I have also contacted laboratories but their sales people don't know.}
220.244.35.181 (talk) 05:02, 29 March 2011 (UTC)

Based on this I think it means 3 single Bacteria (per gram). Ariel. (talk) 07:04, 29 March 2011 (UTC)

Thanks, I did come across that paper, but I'm afraid it's no clearer - it doesn't state what test it uses - the test could use a different scale altogether. I'm not a food scientist (or any scientist for that matter) but it was impression that meat products can have thousands if not millions of bacteria - it seems absurd to me that you'd only find "3" micro-scopic bacteria of E. coli on a single gram. 220.244.35.181 (talk) 09:27, 29 March 2011 (UTC)

Reading this [13] report, it seems it may be common to give the number in log10. So "3" actually means "10^3". That's still not a lot though, maybe it just puts a cap on the required measurement sensitivity. If you had say 20 bacteria per gram, you may have had to incubate them for a long time before you could detect them, while a thousand bacteria per gram can be detected just in time to stop a meat shipment. But this is just my speculations. EverGreg (talk) 12:51, 30 March 2011 (UTC)

What percentage of the atoms in our bodies were born in the hearts of dying stars?

Based on this table detailing the Chemical makeup of the human body, what percentage of our atomic composition (not mass) was created as a result of the death of stars? Flaming Ferrari (talk) 06:03, 29 March 2011 (UTC)

It's almost impossible to speculate. Just about any element lighter than iron can be created by Stellar nucleosynthesis; heavier elements than iron are thought to arise from supernovae. However, given all of the various ways that a star may "die"; even if we just consider supernovae, a large percentage of all elements are likely scattered from them, even small elements like hydrogen, so just about any of the atoms in your body could have come from "dying stars"; and since two atoms of the same element and isotope are literally indistinguishable, there's no telling where they came from. --Jayron32 06:23, 29 March 2011 (UTC)

This sounds like a homework question to me. I'd guess that the instructor means for you to figure that everything but hydrogen "was created as a result of the death of stars". So, that's 90% of the mass of a human, but you can do the math to figure out the "percentage of our atomic composition" (which I assume means by count of atoms). Since hydrogen is the lightest element, the count of hydrogen atoms should be considerably more than 10% of the body. If you want to do the math here, we'll check your work. StuRat (talk) 07:16, 29 March 2011 (UTC)

A homework question where the lecturer refers the students to a Wikipedia table? Things have gone downhill since I left academia five years ago! --TammyMoet (talk) 07:57, 29 March 2011 (UTC)

They may have found that on their own, but don't know how to get the answer to the HW question from it. StuRat (talk) 08:55, 29 March 2011 (UTC)

Wikipedia has come on a lot in five years. We hope. Itsmejudith (talk) 16:16, 29 March 2011 (UTC)

A significant part of the Lithium also originates from BBN. Count Iblis (talk) 14:06, 29 March 2011 (UTC)

True, but lithium (and helium, the other major non-radioactive elemental product of Big Bang nucleosynthesis) have no known biological function, and are present in the body in negligibly trace amounts. TenOfAllTrades(talk) 14:29, 29 March 2011 (UTC)

Maybe you should count everything heavier than (or at least as heavy as) lithium and at least as light as iron, because it is hard to think of a supernova's exploding shell as a heart. But then again, most stellar nucleosynthesis takes place when most people would not say the star is dying, but the supernova does, so maybe you should count everything heavier than iron. But don't supernovae synthesize some proportion of light elements, too? Does anyone have a good idea what that proportion may be? 99.2.149.161 (talk) 17:49, 29 March 2011 (UTC)

There's the issue of when elements are created, and also when they are released. Even if somewhat heavier elements are created before the death of a star, if they languish in the star's core, they aren't available biologically. From my experience with sloppy homework (and test) questions, it wouldn't surprise me a bit if the instructor is conflating those elements created by a star's death with those released by it. Unfortunately, with such sloppy questions, figuring out what the instructor really meant to ask is often the most difficult part of the problem. StuRat (talk) 18:09, 29 March 2011 (UTC)

part 2

A.mohammadzade let me ask this again ,as all know the huge part of our body contains water and the protein which made our meat is made of hydro carbon .Calcium element is about 15 percent and iron is in our blood and so zinc and Natherium ,... The first interstellar cloud which made sun and solar system might had hydrogen and helium so the last effects of dust came from novas and supernovae mixed to this cloud and the nebula had some thermodynamic conditions to made water and chemical matters , hydrocarbons made in earth specially condition which made the life .and first nebula did not be able to produce carbon and oxygen , which made 23percent of earth mass and 21%of air ,and several metals and silicates in earth crust are oxidized .

I want you my friends not to say died star for super novae they made life and they are absent in sky and send pulses and notice: Some body used to say something about the black holes but I prefer to say about super novas , the first one shows death and being mystery the second one is about the life and being alive .it had send oxygen and carbon ,so calcium and iron here to made our life(akbar mohammadzade)

 :--78.38.28.3 (talk) 04:08, 30 March 2011 (UTC)

I moved this from your new post on the same topic. It should all be kept together. StuRat (talk) 04:21, 30 March 2011 (UTC)

gas heat

my furnace is AC ready but has no AC hooked up to it. my repair guy said i have to clean that part too. how do i do that? — Preceding unsigned comment added by Wdk789 (talk • contribs) 07:03, 29 March 2011 (UTC)

When you say AC do you mean Air Conditioning or AC electricity? Ariel. (talk) 07:08, 29 March 2011 (UTC)

Air Conditioning — Preceding unsigned comment added by Wdk789 (talk • contribs) 07:17, 29 March 2011 (UTC)

So you have a point where the A/C unit will tie in to the duct-work of a forced-air gas furnace, and need it cleaned ? If it's a matter of cleaning out a duct, I'd use some kind of a mop in the open end. I'd use it dry to get the dust out. Wear work clothes and a dust mask while you do this, or you may be in for a coughing fit. Also, turn the furnace off shortly before you do this, as the duct-work might be hot where it connects. Note that there are companies that clean ducts, if you don't want to do it yourself. StuRat (talk) 07:22, 29 March 2011 (UTC)

Could you fit a model V12 or W16 onto a motor scooter and make it really work?

See, this is a real-working model V12: http://www.youtube.com/watch?v=0V_2v-ol1EU

And this is a W16, intended to be a 1/5th scale model of the Bugatti Veyron engine: http://www.youtube.com/watch?v=-DijdisWkAE

Are the horsepowers divided by their scales? Therefore, if the W16 has 1001 HP, would the fully-working 1/5th scale model have 200.2 HP? If so, how well would a 200.2 HP engine work on your everyday commuter motor scooter?

Regardless, what kind of ride would you get by putting those miniature versions of the Über engines into a motor scooter? What would your top speed be from there on out, as well as the acceleration, noise and fuel mileage? --70.179.169.115 (talk) 07:54, 29 March 2011 (UTC)

I don't know if the simplistic approach to working out the horsepower is right, but even if it is, since the engine is three-dimensional you'd want the inverse cube, which is 1/5th times 1/5th, making 1/25th the horsepower. Wait, or do I mean 1/5th times 1/5th times 1/5th (1/125). It will be disappointing, anyway. 213.122.57.127 (talk) 08:31, 29 March 2011 (UTC)

It would be the cube of 1/5, since the engine displacement volume is related to horsepower. So that would be 1/125th of 1001 HP, or approximately 8 HP, if it worked. However, internal combustion engines aren't very scalable (unless you change the number of cylinders along with the scale). So, while a 3 cylinder engine with that displacement might work well, a 16 cylinder engine would probably barely run, because all those moving cylinders would increase friction relative to the 3 cylinder engine, but without the displacement needed to overcome it. Of course, there are other things to change, too, such as the compression ratio and revs per minute, to get better performance out of the smaller engine. StuRat (talk) 08:47, 29 March 2011 (UTC)

Neutron star matter, on Earth

So let's say some Star Trek like genius, in the 53rd century AD, creates a technology that can grab neutron star matter without it decaying in any way. So the United Federation of Planets decides to go grab some, and transport it back to Earth.

Once at Earth, the matter is released as-is into the Earth's atmosphere. What would the reaction be? of:

1. The Quark-gluon plasma at the center (density: ~6-8 trillion pounds per teaspoon)
2. The crust (density: ~10 thousand pounds per teaspoon, and ten billion times stronger than steal, at least at the immense pressure on the neutron star itself).

Magog the Ogre (talk) 17:16, 29 March 2011 (UTC)

Some potentially useful discussion along similar lines was discussed not too long ago, though it doesn't address your question directly. --Mr.98 (talk) 19:09, 29 March 2011 (UTC)

Oh, neat. From what I can see, regarding the thickest of the matter:

• If it were to remain in this neat sci-fi vessel we have, and not explode, it would barrel a whole to the center of the earth, sucking massive amounts of matter in its wake, and surely causing earthquakes, volcanic eruptions, and all sorts of other havoc.
• If it were released suddenly into the air, it would be the equivalent of a nasty nuclear bomb; however, given that it would keep exploding for a good time, it quite likely could destroy all life on Earth.

For the less dense stuff: maybe just a really big explosion that could kill a lot of people? Magog the Ogre (talk) 20:47, 29 March 2011 (UTC)

At STP, what is the predicted density of a neutron gas. Does a neutron gas have a theoretical triple point? Plasmic Physics (talk) 03:23, 30 March 2011 (UTC)

There isn't any predicted information like that. Neutronium is a term which was coined, conjecturally, for such standard conditions neutron-based matter, but no known substances exist, and there isn't a lot of reliable prediction for what it would look like if it did. The Wikipedia article actually covers this well, at least in noting that no one seriously considers it a likely form of matter, except in some very exotic conditions. The other type of neutron matter, known as Neutron-degenerate matter literally cannot exist at STP, as it requires the literally astronomical pressures in a neutron star to exist. If that matter were to be brought to STP, it would rapidly convert to normal (proton-electron-neutron) matter of some sort, likely mostly hydrogen, deuterium, and helium. --Jayron32 05:21, 30 March 2011 (UTC)

I don't really know what ot make of your answer - I googled "neutron gas", and one result described a low density neutron gas produced for the purposes of a projectile target for a particle physics experiment. For clarification, I'm not refering to degenerate states of matter, but simply a bulk sample of neutrons in a closed container with movable walls. The result did't answer my questions, if you were going to ask. Plasmic Physics (talk) 12:08, 30 March 2011 (UTC)

While I'm at it, here's another one: since neutrons have no atomic orbitals, is there any substance that can contain such a hypothetical gas of neutrons, wouldn't the gas simply diffuse through the walls of the container within a matter of hours? Plasmic Physics (talk) 12:13, 30 March 2011 (UTC)

Hypothetically, neutrons would not be subject to intermolecular forces, since they are both neutral and extremely hard (i.e. nonpolarizable). In other words, they aren't subject to even London dispersion forces, generally held to be the weakest of the common Van der Waals forces regulating the formation of non-gasseous phases of matter. If we were to consider a bulk gas composed of nothing but neutrons which was also at atmospheric densities, there are literally no forces at all which could act, at any temperature, even infinitessimally close to absolute zero, which could cause the neutrons to form a condensed phase. So, there would literally be no triple point, because there are no forces acting to cause neutrons to attract to one another. Collecting low-temperature neutrons like this to even make such a gas is likely impossible; but even if you could it would never be anything but a gas. --Jayron32 13:02, 30 March 2011 (UTC)

The neutrons are made of quarks, right? Quarks have charges, right? Would that make the neutrons slightly polar? So, if the temperature brought within a picokelvin above absolute zero, wouldn't they form transient atractions to one another? Plasmic Physics (talk) 13:12, 30 March 2011 (UTC)

I was about to say no, but reviewing Neutron#Structure_and_geometry_of_charge_distribution_within_the_neutron, it seems that very recent research suggests that there is a non-uniform charge distribution within a neutron, implying that they would be subject to something akin to London dispersion forces, so perhaps at such tiny temperatures (femtokelvin? attokelvin) there may be some time when induced charge seperation could generate a condensed, low-energy, low-pressure form of neutron matter; akin to a neutron liquid or neutron solid. The problem is, we have no reliable way to predict behavior at that level; at the distances that would be required for such tiny forces to work, the electromagnetic force, which would be responsible for solid or liquid formation, is actually much weaker than the nuclear forces which regulate things like quark interactions and internucleon interactions. In other words, at the distance you would need to bring many neutrons together in order to have them be attracted enough to form anything like a condensed phase of normal atomic matter, the situation is so drastically different than even for the smallest atoms. Consider that Hydrogen has a van Der Waals radius of 120 pm; this is the roughly scale of the minimum interatomic distances present in a condensed phase. The Wikipedia article on the neutron doesn't contain any information on its size, but this document calculates a radius of about 1 femtometer, or roughly 1/100,000 the radius of a hydrogen atom. So your hypothetical neutron solid would, once again, be under the influence of forces other than the electromagnetic force, which is sorta the definition of degenerate matter in the first place. In other words, low-temperature neutronium solid wouldn't be a solid under the normal definition of a solid, insofar as it obeys the odd laws of physics regulating degenerate matter rather than that of normal matter. So, once again, there is no hypothetical "normal matter" condensed phase substance composed of neutrons alone. There may be a neutron gas, but it will not condense to form solids or liquids which resemble, in any meaningful way, a real solid or liquid. --Jayron32 14:02, 30 March 2011 (UTC)

The neutron is "supposed" to have a Neutron electric dipole moment according with theoretical models, but that moment is so small that no experiment has ever been able to detect it. Dauto (talk) 19:21, 30 March 2011 (UTC)

Ok, I believe you, there is only one phase in the classical sense for a neutron gas due to the lack of interaction taking place however, interneucleon forces may or may not cause a condensate like phase to form (degenerate matter). What about my other question, concerning its diffusuability through solids? Plasmic Physics (talk) 23:47, 30 March 2011 (UTC)

What did the retired US Air Force nuclear missile commanders tell the National Press Club?

What's the most reliable summary of this? Specifically I am looking for something with the number of retired officials confirming the incidents, whether there are any incidents reported that vary substantially from the typical report, and the date ranges for each of the incidents. 99.2.149.161 (talk) 17:36, 29 March 2011 (UTC)

That article describes a book, written by a space alien enthusiast. It seems he read about, or attended, a September 2010 press conference, where a retired Air Force officer did make explicit reference to extra-terrestrial life.

But overall, this is just a space-alien enthusiast, who read about, and then created a mangled and contorted version of, a much more benign press version of reality; and then added several generic, probably totally-fictional stock-descriptions about extra-terrestrial encounters. In the 1940s and 1950s, as the threat of nuclear war became real, military brass set up loads of early warning systems: RADARs and other aerial surveillance systems. The plan, part of the Mutually Assured Destruction strategy, was to monitor the sky for anything that looked like an incoming bomber or missile - and if we saw one, we'd blow away the Soviet Union with a full-scale missile strike. (Obviously, this was a bad idea)..

Now, as anyone who has ever used technology of any kind can tell you, electronics have "glitches" sometimes. RADARs often report false-positives - "glitches" - noise, due to electronics and atmospheric effects. (When a RADAR picks displays an unknown dot, it is an "unidentified flying object", right?) So, as the NORAD and SAC commanders and strategists realized that their RADARs had glitches, they realized that they couldn't sustain a "fire all missiles" response to every little static-noise burst.

Our space-alien enthusiasts gladly pick up on Project Blue Book: the Air Force systematically studied UFOs, and then decided to close all further investigations - well, let's step back and read that one more time. After years of policy that required escalating every static noise burst to the President so he could decide whether to nuke the Russians, the Air Force finally realized that there was such a thing as electronic noise, and that not every RADAR pulse was actually an enemy aircraft or missile (or extraterrestrial space-ship). The presence of "UFOs" required bringing our nuclear response to a reasonable level. Nimur (talk) 14:32, 30 March 2011 (UTC)

Is that a fair characterization of what took place at the National Press Club? Is it true or not that "several" retired USAF officials said that they had personally witnessed nuclear ICBMs deactivating at the same time that UFOs were being reported above ground at the same facilities? If so, exactly how many officials and how many separate incidents were there? Over what time period did these incidents occur? Is it true that such incidents have also been reported by former USSR officials? I am baffled that even UFO enthusiasts do not seem to be following this story as closely as I'd expect them to. I just want a reliable summary. 99.2.149.161 (talk) 21:19, 30 March 2011 (UTC)

What experimental recreational drug am I thinking of?

Resolved

I remember reading a news article a year or two ago (I think) about a company that was trying to create a recreational drug that would get you high, but without side-effects, and with an antidote that you could take should you need to become sober quickly. Does anyone know what I'm thinking of? A Quest For Knowledge (talk) 17:41, 29 March 2011 (UTC)

Nevermind. I found it.[14] A Quest For Knowledge (talk) 20:03, 29 March 2011 (UTC)

Identify my skull

Could anyone help to identify this skull (assuming it is a skull). It was found in rocky hills in Oman; the absence of obvious front-facing eyes is puzzling; it's very light and has what look like air pockets, so possibly a bird? Thanks for any help! Henry^Flower 18:07, 29 March 2011 (UTC)

• 
  side view
• 
  bottom view
• 
  rear view
• 
  eye socket remnant?
• 
  brain case
• 
  the nose

If it lacks eye holes, are you sure it's a skull, as opposed to some other bone ? StuRat (talk) 18:12, 29 March 2011 (UTC)

Not at all sure, no. :) On the other hand, I have no idea what other bone it could be; it is basically round and hollow, with a hole at the back which looks like a spinal cord would go through it; and there might have been an eye socket in the broken part (though then the eyes would have been looking to the side and slightly backwards. Henry^Flower 18:17, 29 March 2011 (UTC)

Yes, it's a skull (you can see the distinctive suture lines), but we'd need more pictures to be sure of what exactly it came from. Based on the general roundness, size, and the area it was found, I'm thinking it's a species of monkey. Matt Deres (talk) 18:57, 29 March 2011 (UTC)

(EC)I can't help with ID, but I think you're on the wrong track with the "lack of eyes" idea. Keep in mind that your specimen is highly damaged, whatever it is. Look at this raccoon skull:[15], and this gerbil skull [16]. Basically, these animals' eyes are well outside the main brain-case enclosure. It could be that what you have is a similarly shaped skull, and the thin bits of bone arch that surround the eye socket have broken off. It's hard to tell from your pictures, but I think the side view may show remnants of such bones. SemanticMantis (talk) 18:59, 29 March 2011 (UTC)

Yes, it's definitely a skull, and definitely very badly damaged -- you really only have a small part of it. It looks to me to be a mammal skull, from a pretty good-sized mammal. One possibility may be a dog. Looie496 (talk) 19:09, 29 March 2011 (UTC)

If there are any teeth left, a close shot of those might be very helpful. Googlemeister (talk) 19:41, 29 March 2011 (UTC)

The round hole at the front made me think of some sort of anteater, something like this doesn't look too dissimilar, has a similar "lack" of obvious eye holes. Having a quick look it seems like there are anteaters in Oman. Vespine (talk) 23:11, 29 March 2011 (UTC)

Hmm well, ok, i'm wrong about the anteater in Oman, seems like they're only in south america.. How about armadillos ? Vespine (talk) 23:21, 29 March 2011 (UTC)

That's the back, so the hole is for the spinal cord. StuRat (talk) 23:18, 29 March 2011 (UTC)

Aaah! Yes, i was looking at it wrong, sorry... but anyway the links I posted show that lack of "obvious" eye holes are not necessarily a problem. Vespine (talk) 23:22, 29 March 2011 (UTC)

I'm really curious now! I don't think it looks rodent, canine or rabbit, what other "common" animals are there in Oman? Vespine (talk) 23:25, 29 March 2011 (UTC)

It would help to know what kind of soil or rock strata it was found in. then we might have an idea whether we're trying to match with a modern (familiar) animal or something else. Also does it seem to be actual bone or rock,as in fossil?190.148.134.128 (talk) 00:32, 30 March 2011 (UTC)

also what is front or back seems at this point to be conjecture.190.148.134.128 (talk) 00:56, 30 March 2011 (UTC)

It's light and has air pockets, i think it's obviously bone, not a fossil. The main problem I think is the OP has not given a good frontal photo showing the nasal area and the jaw structure on the underside photo is badly out of focus, these areas in particular would probably reveal a lot more unique detail. Vespine (talk) 01:02, 30 March 2011 (UTC)

I'm trying to find fauna local to the region but not much luck. There's an awesome feline called a caracal but the skull looks very different, as does a local wolf, hyena and several antelope or goat like animals. I don't think it's a bird or a a lizard, or a rodent, my guess is some sort of mammal but I'm really stumped without some better photos. Just for clarification, you do mean Oman the country on the Arabian peninsula, not some other town somewhere like Paris Texas or something. Vespine (talk) 01:18, 30 March 2011 (UTC)

The nasal area is missing, as is most of the upper jaw. This is really just the back of the skull, and not even all of that. Looie496 (talk) 03:07, 30 March 2011 (UTC)

Thanks for all the ideas! In answer to a few points:

- SemanticMantis, your point about the eyes seems to be along the right lines - the racoon skull is quite similar. Presumably not an actual racoon here in Oman, though there must be something similar.

- I've added a few more photos showing the (probable) remnants of the eye sockets, inside, and what's left of the front/nasal area.

- For what it's worth, this page has photos of various animals from the author's travels (mostly in Oman).

- It's definitely bone, not a fossil. It was in a rocky desert area, altitude about 500m.

Even if we can't identify it for certain, at least is slightly less of a mystery to me now. :) Henry^Flower 03:24, 30 March 2011 (UTC)

AH, I see now. In the first out of focus photo I actually thought those might be tooth socket remnants but it's obvious that whole upper jaw area is worn away.. I take back what I said about it not being a rabbit or rodent, in fact, if you use your imagination, it could be a rabbit, or maybe more likely a hare, if you look at a picture like this and use your imagination to deteriorate the missing parts, it's not extremely dissimilar. Vespine (talk) 04:54, 30 March 2011 (UTC)

My guess would be a Mustelid but without an indication of size it's very hard to be more specific. If it is clearly too big to be a Mustelid I would change my "vote" to Canid. Roger (talk) 12:51, 30 March 2011 (UTC)

I don't think it's a rabbit: the spinal cord hole in the rabbit skulls I've seen is in the base (the head sitting on top of the body); I imagine a hare is the same. This one has the hole in the rear of the skull, which would seem to imply a more horizontal body posture, which in turn would fit with the idea of a weasel-type thing. The skull (or rather the bit I have) is about 7-8cm, so maybe something a bit bigger than a pine marten. Henry^Flower 16:46, 30 March 2011 (UTC)

If I can get a bit nosy: what in the world were you doing in Oman? I can't think of any reason whatsoever to be a tourist in that country. Unless you live there, which also seems unlikely to me. Magog the Ogre (talk) 17:02, 30 March 2011 (UTC)

See Tourism in Oman. Are you confusing Oman with Yemen perhaps? Looie496 (talk) 17:20, 30 March 2011 (UTC)

Didn't they used to be the same country? Regardless, I can't imagine traveling halfway around the world to a part of the world quite hostile to westerners (of which I am one), to go touring in the middle of the desert. Then again, I live in the US, so maybe that will cause some differences. And to each his own (maybe Oman has a great industry I don't know), but I still don't understand why someone else would do it. Magog the Ogre (talk) 19:54, 30 March 2011 (UTC)

We're way off topic here, but the two are quite different. Oman is a country with 2.7 million inhabitants and a per-capita GDP of about $14,000. Yemen is a country with about 22 million inhabitants and a per-capita GDP of less than $1000 -- i.e., one of the poorest countries on earth. Oman is politically stable and welcoming to westerners. Yemen is a hotbed of turmoil and a dangerous place to visit. Looie496 (talk) 20:50, 30 March 2011 (UTC)

carbon-dioxide atmosphere

I have a long list of questions for an idea that I've been thinking about. But I will stick with the first because it may negate the rest. I only mention this because this question surely seems nonsensical... Assume that a lot of carbon dioxide was added to the Earth's atmosphere. Along with this, there would be extensive global warming. So, it is safe to assume sulfer dioxide would be be produced in excess. Is there a point at which excessive heavy gasses (ie: carbon dioxide and sulfer dioxide) would settle to the lower elevations on Earth and the lighter atmosphere consisting of oxygen and nitrogen would float above that? Obviously, there would be a mixed area. I'm really asking if oxygen can be pushed up higher than it is now due to heavier gasses in the atmosphere - or, will the oxygen remain where it is and just mix with the heavier gasses? -- kainaw™ 19:51, 29 March 2011 (UTC)

We have many different gases in the atmosphere now, and they generally seem to mix rather than form distinct layers. Yes, the concentrations of the various gases does vary a bit by altitude, but, other than the pressure differences, the air on the top of Everest is basically the same as at sea level, because winds continuously mix them up. I'd suspect that winds would be even stronger on a hotter Earth, since heat differences drive winds, so this "mixing bowl" effect would remain. StuRat (talk) 20:32, 29 March 2011 (UTC)

It's because the atmosphere is clear to a lot of radiation, which is then absorbed by the ground thus bottom heating the atmosphere and preventing stable stratification. If the atmosphere was opaque to most radiation, stable stratification could be a possibility. —Preceding unsigned comment added by 92.20.201.71 (talk) 20:57, 29 March 2011 (UTC)

Well, the atmosphere does show quasi-stable stratification, but the strata are relatively thick: troposphere, stratosphere, ionosphere, etc. Within the troposphere there is very extensive mixing due to the fact that solar radiation heats it from the bottom -- this mixing rapidly undoes any separation that may start to arise from differences in density. Note that there have been epochs of geological history when CO2 concentrations were up to 100 or more times higher than today. Looie496 (talk) 21:26, 29 March 2011 (UTC)

One might consider that even with all the lower level mixing there is a surprising degree of stratification.for example ozone being triatomic oxygen O3 is way up there, in the mesosphere if I remember correctly.and we all know how important that is. I don't know what you're theory is but you might pursue it further.190.148.134.128 (talk) 01:21, 30 March 2011 (UTC)

Hi there, i just fixed up 128's reply, please don't manually indent your replies but instead use : at the start of your contribution (have a look at the other replies to see how it works). A manual indent has a different function in wiki formatting. Vespine (talk) 01:27, 30 March 2011 (UTC)

Thank you "vespine". I must explain that I am a really old guy and the computer is a new tool to me. I have no idea what "manual indent" means because I don't speak computorese. you're probably quite young and can't imagine how this can be possible because you probably have grown up with a computor. It sounds to me that you're saying I must read the other entries and agree with them, but I can't believe that. I'm not trying to be a smart ass. please tell me what I did wrong in plain english.190.148.134.128 (talk) 02:22, 30 March 2011 (UTC)

"Manual indent" means starting a line with spaces. If you want a line to be indented in Wikipedia, you should start it with a series of colons, such as "::::::". (I have fixed your previous line.) Looie496 (talk) 03:02, 30 March 2011 (UTC)

And, just to demonstrate:

                      this is a manual indent.

We do use that, but not when we just want regular text, it's reserved for special things. For example, it's sometimes used to make diagrams. StuRat (talk) 03:19, 30 March 2011 (UTC)

It should be noted that in high enough concentrations, carbon dioxide does settle, see Lake_Nyos#The_1986_disaster for an example of what happens when it does. However, this is quite a different scenario from atmospheric carbon dioxide. Essentially what happened at Lake Nyos was a bubble of pure carbon dioxide was "burped" out of the earth; this CO2 had very little mixing with the atmosphere, and so it suffocated the entire region. Atmospheric CO2 accounts for less than one part per thousand (see Atmosphere_of_Earth#Composition). According to Hypercapnia (the medical term for too much CO2), severe effects on humans don't set in until 10 kPa, or about 10% of the air, though minor effects set it at lower concentrations. Even assuming that some medical problems set in at 1% CO2, that would still require there to be 30X as much CO2 in the atmosphere as there is now. Even at those concentrations, there is sufficient circulation in the troposphere to assure complete mixing, even in the face of gravitational seperation. --Jayron32 03:33, 30 March 2011 (UTC)

According to scale height, each gas has its own scale height above 100 km due to diffusion. Wnt (talk) 03:39, 30 March 2011 (UTC)

Yes, but there is a big difference between what happens way up at 100 km and what happens in the much denser, and much more well mixed, troposphere... --Jayron32 03:45, 30 March 2011 (UTC)

Thanks for the answers. It appears that stratification is inhibited by heat that radiates from the planet surface. So, to get stratification to work well, radiant heat must be limited. Low-level greenhouse gasses will assist in two ways. First, they will reflect much of the solar radiation before it reaches the surface. Then, they will absorb and reflect heat before it reaches very high into the atmosphere. I think that studying temperatures on Venus will help me get a good idea of how well that will work. -- kainaw™ 12:15, 30 March 2011 (UTC)

Superallowed beta decay.

Superallowed transitions seems to be defined as those between members of an isotopic spin multiplet.

How could a beta decay not be between members of an isotopic spin multiplet? Since it is a weak interaction surely the number of quarks and hence total isospin will be conserved? So what is the difference between allowed and superallowed transitions? —Preceding unsigned comment added by 92.20.201.71 (talk) 20:29, 29 March 2011 (UTC)

OP: Is it just that nuclear spin doesn't change? In which case how is a superallowed transition different from a pure fermi transition? —Preceding unsigned comment added by 92.20.201.71 (talk) 20:46, 29 March 2011 (UTC)

You stated "the number of quarks and hence total isospin will be conserved?". That's not true. The total isospin can change. Dauto (talk) 21:00, 29 March 2011 (UTC)

up and down quarks both have I=1/2. I don't understand. —Preceding unsigned comment added by 92.20.201.71 (talk) 21:05, 29 March 2011 (UTC)

What don't you understand? We might be able to explain if you let us know. Dauto (talk) 02:14, 30 March 2011 (UTC)

Ok so my understanding was that nuclear isospin multiplets all had the same I and different values of I₃. And that beta decay acted essentially as the creation/annihilation operator I^±. And that since the operator I^± cant get you out of the spin multiplet, all beta decay must be between isospin multiplet states. This appears to be in contradiction with the above statement I was troubled by about superallowed states, and your statement that I can change. So I'd be glad if you could help me grasp the nature of my misunderstanding. Thanks. —Preceding unsigned comment added by 92.20.201.71 (talk) 02:34, 30 March 2011 (UTC)

Let me state upfront that my specialty is with particle physics, not nuclear physics. Your understanding is approximately correct and that's why beta-decays that violate the principle you describe must pay a penalty and will be less probable than naively expected. You must keep in mind that unlike weak isospin, isospin is not an exact symmetry. Dauto (talk) 04:08, 30 March 2011 (UTC)

What kind of beta decays are the ones that break the symmetry? Is it just beta decay which changes a quantum number other than I₃, such as when the neutrino and beta particle make a spin triplet and nuclear spin changes? Sorry, I may be asking tedious questions as I only started nuclear and particle this year so I do not have a condensed understanding of the subjects. —Preceding unsigned comment added by 92.20.201.71 (talk) 20:05, 30 March 2011 (UTC)

ingesting radiation

I am confused as to the reporting concerning the dangers of the current Japanese Radiation problem.

To my very basic knowledge it will be really bad to ingest any radioactive substance even on a small scale as it will spit out beta,gamma or alpha for a lifetime which would harm the body's cells . Hence absorption into the body is the real danger, this will occur via the food chain or inhalation.

I am not sure if the media reporting is referring to "safe" levels of radiation as "safe if you do not ingest/breath it in" in other words the level is safe "at a distance" outside of the body.

In a similar way you can say that Americium in a smoke detector is at a perfectly safe level but if you ate it it would be very bad for you as you are then having a permanent amount of Americium absorbed into your body. —Preceding unsigned comment added by 2.97.155.22 (talk) 21:32, 29 March 2011 (UTC)

It is important to distinguish between "radiation" and "radioactive substances". Radiation reduces very quickly with distance so the radiation being emitted by the reactors in Japan is only potentially harmful for the people working on them. The big risks are associated with radioactive particles escaping, since they can travel great distances and, as you say, be ingested. The big fears at the moment are with water outside the reactors that has been found to contain radioactive particles. As for the media, they usually don't know what they are talking about. They talk about both radiation and radioactivity, but don't always distinguish between them. --Tango (talk) 21:55, 29 March 2011 (UTC)

EC, See Sievert and Gray (unit). Your understanding comes from the fact that ionising radiation has zero risk when the source is at a sufficient distance. However, a suitably small amount of even a potent alpha source, can still be safely consumed. Basically when the scientists say it is safe, it is safe. —Preceding unsigned comment added by 92.20.201.71 (talk) 22:03, 29 March 2011 (UTC)

What happens to you if a radioactive substance gets into your body depends on a lot of things, not just its nuclear properties but also its chemical and biological ones, and mode of administration. For example a very tiny amount of plutonium in your lung is very likely to give you lung cancer. However it might not harm you if you ate it, because it's poorly absorbed (no warranty on this! I will not be responsible for anything that happens to you). See plutonium#toxicity.

Similarly iodine-131 is extra dangerous because of its tendency to concentrate in the thyroid gland, and strontium-90 because it is chemically similar to calcium and is incorporated into bone. --Trovatore (talk) 22:05, 29 March 2011 (UTC)

You are correct that most descriptions of "safe" radiation are about acute exposure, not chronic. Acute exposure is the kind of radiation that'll give you radiation sickness — it's most of what this chart is about. Unfortunately, for 99% of the people concerned, this is not the kind of radiation hazard they are going to be exposed to, because very high levels of radiation are quite rare and usually quite localized (e.g. right around the reactor). The chronic risks are from elements with long half-lives and corresponding low energy radiation, but when ingested can cause a lot of internal damage over time.

Why is this distinction not usually made? Ignorance, probably. Mixed with that lovely impulse by the scientists and engineers to assert that the general public is worried about nothing. But also because discussing chronic exposure requires a lot more specificity about the particular risks you've got in mind, and frankly even the experts are often very poor at breaking these down into separate issues. As Trovatore points out, it really depends on the substances in question and how they get into you. Some radioactive substances through some pathways flush out of the body with no harm. Some deposit themselves in your bones or thyroid or what have you, and can do a lot of damage.

I would not be comfortable if it was just the media telling me it was safe — it is clear that most journalists do not even begin the know what "safe" and "dangerous" means in the context of radiation. I would parse very closely the statements by officials and engineers — they often will say things like, it is safe for you to be in an area, but don't eat anything that grows there. There are also complicating factors — being exposed to radon gas by itself, for example, will have very little effect on your long term lung cancer risk. But if you smoke a cigarette in an area with high amounts of radon, you end up with all sorts of compounding factors and your risk goes up by a huge amount. --Mr.98 (talk) 22:21, 29 March 2011 (UTC)

March 30

Spreading mineral matters on earth

The general oxidation of earth crust might be after the time once the earth surface was molten ,the outer crust material complex and the location of mines such as aluminum and Ferro and copper in Alp -Himalaya belt shows us that thoroughly it was our earth surface molten for about 800 million years , and when any asteroid with mineral matters hinted our earth it had to be molten and spread on earth surface.(A. mohammadzade ) --78.38.28.3 (talk) 05:15, 30 March 2011 (UTC)

Is there a question here ? StuRat (talk) 05:23, 30 March 2011 (UTC)

Also, let me suggest that you also post in your native language (and tell us what it is), as we might be able to translate it better than you. Your English is barely readable. For example, "Coeur" isn't an English word. It means heart in French, but that seems wrong in this context. Did you mean copper ? StuRat (talk) 05:26, 30 March 2011 (UTC)

I can't find a question, but the OP may find useful information on the cooling of the earth at History of the Earth and Hadean Eon. The asteroid impacts he is talking about occuring during Earth's molten phase happened during the Late Heavy Bombardment period. The ancient cores of continents, believed to date from the Hadean, are called Cratons. The location of ore deposits and how they formed are complex geochemical processes known as Ore genesis. All of the links I provided here should answer any questions the OP may have, given the various statements he made. --Jayron32 05:29, 30 March 2011 (UTC)

the continues spreading shows the question about the subject late heavy bombardment say me about this ,and first earth creation .--78.38.28.3 (talk) 05:36, 30 March 2011 (UTC)a. mohammadzade THANK YOU

Please post your question in your own language as your English, which I suspect is a machine translation, is unintelligible. Roger (talk) 13:19, 30 March 2011 (UTC)

His IP suggests he is from Iran. At any rate my guess is that he wants to know is if meteorite strikes have any relation to current composition of Earth's crust (i.e. have they changed location of minerals and metals in it) ~~Xil (talk) 15:37, 30 March 2011 (UTC)

If so, he might be interested in our article on the Sudbury Basin. Matt Deres (talk) 18:35, 30 March 2011 (UTC)

How do you ask him to post in Farsi, in Farsi? 92.15.1.33 (talk) 16:17, 30 March 2011 (UTC)

I will post a request for assistance at the Language RefDesk. Roger (talk) 16:32, 30 March 2011 (UTC)

Milligram scale

We cannot offer you instructions on compounding pharmaceutical products. Please speak with your doctor or pharmacist if you would like to be able to safely adjust the dosages of your medication. TenOfAllTrades(talk) 22:44, 30 March 2011 (UTC)
The following discussion has been closed. Please do not modify it.
This question is a bit unorthodox, I realize, but: where can I get a scale that will accurately measure within 1mg? I am willing to pay no more than $100, $150 if I get really desperate. I looked on Amazon and found a lot of cheap ones that aren't precise at the 1mg level, which is unacceptable for me. And I see some more expensive ones but they don't have enough reviews for me to tell how well they'll work. I am willing to buy online, although buying locally would be even more ideal. Magog the Ogre (talk) 16:59, 30 March 2011 (UTC) What do you need the top end of the scale to be? Googlemeister (talk) 18:19, 30 March 2011 (UTC) Ugh, it turns out I have misread! I need it to be accurate to .01 mg, which I know is ridiculously precise, and probably not something I could find easily on the market. But to answer your question: no more than a few milligrams. Magog the Ogre (talk) 18:32, 30 March 2011 (UTC) You need an analytical balance. You 'might' be able to get a secondhand one on Ebay. A basic balance is not really going to be good enough though so make sure it has the resolution you need. What are you trying to weigh? There might be an easier way to achieve the end result --Aspro (talk) 19:04, 30 March 2011 (UTC) Ouch. A balance with a 10 microgram resolution is going to be costly, whether new or used. In the price regime you're describing, you just can't get precision equipment unless a) it's in need of major repairs; or b) you're buying it from someone who doesn't have a clue what it's worth. Properly packing and shipping a microgram balance is probably going to eat a good chunk of your budget, on top of whatever you pay for the instrument. Scientific American did run a column describing how to construct your own balance with your desired precision. If you're good with your hands, you can do it with less than fifty dollars in parts: [17]. The addition of a microcontroller allows you to automate the readout and tare funcions, and still can ring in under $100: [18]. TenOfAllTrades(talk) 19:11, 30 March 2011 (UTC) Re: Aspro: I am trying to measure my prescribed medication which I am splitting (the minimum dosage is .25mg, and I am cutting it in fourths, leaving ~.06 mg/dose; if I am off by even about 25%, I suffer undesirable side effects until my next dosage; my body is amazingly sensitive to tiny changes in chemistry... I can get pretty buzzed off just one beer for example). You will note I am not asking for medical advice (I've already talked to my doctor); I am asking about a scale. Magog the Ogre (talk) 19:58, 30 March 2011 (UTC) The cheapest one I can find after a (brief) search is about $1000. I would suggest asking your doctor if he can provide your medication in something like a pill which can be easily cut into quarters by hand. Or perhaps ask your local college/university if they have some old scales they're about to throw out? 50.92.121.76 (talk) 20:15, 30 March 2011 (UTC) I hope you realise that a pill containing .25mg active ingredient actually weighs substantially more than that. The bulk of the tablet consists of sugar, chalk or another non-bioactive carrier. If it was pure active ingredient the tablet would be like a tiny speck of dust. If you are unable to divide it accurately enough you could try disolving the tablet and then dividing the solution by volume - the more water you use the more precisely you can divide it: .25mg active ingredient disolved into 100cc of water would result in 2.5 microgrammes per cc. Syringes or pippetes that can accurately measure 0.1cc are widely available and dirt cheap. Roger (talk) 20:36, 30 March 2011 (UTC) Re: 50.*: a good idea; i have local contacts in a very large university chemistry department. Doesn't mean I'll get it though! Re: Dodger67: that is an extremely good idea which hadn't occurred to me. Unfortunately, according to the local Wikipedia article, "when crushed in water it will not fully dissolve." I may have to ask my chemist friend about the solubility though. Magog the Ogre (talk) 20:59, 30 March 2011 (UTC) Wow. As detailed as Erowid is about this stuff, they give neither the gross weight of the pill nor the composition of the oral solution form in which it is sold. Wnt (talk) 21:49, 30 March 2011 (UTC)

I can't be bothered with the elaborate brown rice recipes.

Is it still worthwhile to eat brown rice when I can't be bothered to cook it for a long time? 12.40.220.253 (talk) 17:21, 30 March 2011 (UTC)

It sounds like you are asking if it's OK to eat raw rice. Dauto (talk) 18:54, 30 March 2011 (UTC)

If you can be bothered to walk round the supermarket you can find it ready cooked – just needs two minutes in the microwave.--Aspro (talk) 18:55, 30 March 2011 (UTC)

Yes it is, the fibre is very good for you. The way I make rice is: add half a cup of rice and a full cup of boiling water to a saucepan. Bring back to the boil, then reduce the heat and simmer for 20-25 minutes (depends on the rice - could be 25mins for wholemeal, but down to only 15 for white or easy-cook rice - follow packet instructions). Check the saucepan from time to time to make sure it is not boiling dry. I use a timer to measure the time, as it is essential to remove the saucepan before it gets too dry and starts to burn. You can add chopped vegetables at the beginning, but this can introduce more moisture which may need draining off five minutes or so before the end. Best to be watching the saucepan for the last 5 minutes so that you can get the rice as dry as you wish, without burning. I prefer moist soft rice. 92.15.1.33 (talk) 20:47, 30 March 2011 (UTC)

I was surprised when I had some Chinese and Malaysian borders at my place a couple of years ago, when they told me that NO ASIANS these days cook rice as described above. They ALL use rice cookers. And when I bought one, I could see why. They cost about nothing (say $20). you just put the rice in, cover it with water by a couple of fingers, put the glass top on, and turn it on. It will cook the rice perfectly, then switch off to "keep warm" mode. There is nothing to do at all, and the rice is ALWAYS perfect! I never use anything else now. No chance for burning or undercooking, and the cooker keeps the rice warm for hours. Try it. All the Asians use it, and they are the canniest buyers I know. Myles325a (talk) 00:12, 31 March 2011 (UTC)

Protein subunit names vs gene names?

Hi, I had a question about how it is that protein subunits get their names. I was under the impression that if an operon had the structure (for example, in the case of the perchlorate reductase enzyme) pcrABCD, the subunits would be alpha, beta, gamma, and delta (respectively). However, I just noticed that in the case of another enzyme, methane monooxygenase, the pmoCAB operon encodes gamma, beta, and alpha, respectively. So, how is it that biochemists name subunits? Is it not supposed to correlate with the genes (i.e., why is "A" not the alpha subunit?) Thanks for your help. Ccarlst (talk) 22:05, 30 March 2011 (UTC)

Acceleration and relativity

So using the Newtonian a = F/m it would seem an object could be accelerated to any speed. What is the relativistic equation that is asymptotic at the speed of light?   jorgenev (talk) 22:05, 30 March 2011

Four-force —Preceding unsigned comment added by 92.20.201.71 (talk) 22:51, 30 March 2011 (UTC)

(edit conflict):Our article Mass in special relativity explains that the apparent mass M at speed v is given by $M=m/{\sqrt {1-v^{2}/c^{2}}}$ (though this equation is not the best way to look at the situation). The acceleration is thus $a=F{\sqrt {1-v^{2}/c^{2}}}/m$ and gradually reduces towards zero as the speed approaches that of light. Dbfirs 23:00, 30 March 2011 (UTC)

Antimatter, antigravity, spacetime, retrocausality, and antispace

Warning: Risk of cosmological brain spasms or nonexistent headaches

Hi. Does antimatter have positive or negative mass? Assuming it has negative mass, we could depict its effect on the curvature of spacetime as a flat sheet as an object causing an upward dent in this fabric from antigravity, rather than a downward dent produced by normal matter. Using this representation, could we conclude that the collision of a piece of matter and antimatter represents the overlapping of a positive and a negative dent, therby causing the two warping areas to collide and annihilate? Would this be similar to standing waves cancelling out each other, in this case each respective object's mass/antimass, and would this send out gravitational waves? Or, would the idea of each having the other object's respective antigravity cause some kind of gravitational repulsion? Since spacetime is the modern interpretation for interwoven space and time, would antimatter cause negative time to occur in addition to causing a negative gravitational "space-dent"? Could antimatter fuel thus have the capacity for time travel alongside massive propulsion? Also, considering that antimatter produces antigravity as an assumption, would the graviton theory apply to "negative gravitons" or regular gravitons going inward? If a negative and positive graviton were to intersect, what would ensue? Creating negative time from antimatter would enable backward flow of time, and in fact there is some preliminary laboratory evidence of retrocausality. In this scenario, do the occurence of future events cause past events, or do the un-occurrence of future events un-cause past events to un-materialize? When a forward-time-flowing mass of matter and a negative-time-flowing negative mass of antimatter collide, do their respective time reflections cause the collision to un-occur, or does time stop before each object collides into the other? From the relativistic view of one object, it would take an infinite amount of time for the other object to approach whereas it takes very little time to an outside observer. Would this be similar to the theory that time stops for objects entering black holes, which is also proposed by the varying speed of light hypothesis? Or, would this mean that in a quantum mechanics sense, the objects have both simultaneously annihilated and stopped their annhilation but neither outcome has taken place due to the lack of an observer? Does that mean that black holes are the unity of matter and antimatter confined so that their produced energy are converted to mass as time stops the explosive reaction and release of rest energy from taking place? Similarly, could this explain the paradox of an object entering a black hole and coming out in the past in a different trajectory as to knock the original object away from the black hole's path so that the original event could never have taken place, by realizing the past post-entrance object as one quantum half of the original object so that they merge and two digressional paths occur? Could any event in the universe, even for a fraction of Plank time, cause the black hole-type dent in spacetime to reach so infinitely deep that it comes around on the other side ("around" the ultra-dimensions of the universe, even if flat) and connects into itself like an infinite regression wormhole? Finally, would a "dent" made in space by antimatter cause the object to take up negative space, so that its dimensions are, say, -2 cm in diameter (and would this also cause "in" to be an infinite directional dimension similar to "out", which does not end until the edge of space is reached)? Does this potential for anti-spacetime have any potential implications, or does this hypothetical description reduce relevance to cosmological nonsense? Thanks. ~AH1^(TCU) 23:33, 30 March 2011 (UTC)