Wikipedia:Reference desk/Science

Welcome to the science section
of the Wikipedia reference desk.

skip to bottom

Select a section:

• Computing
• Entertainment
• Humanities
• Language
• Mathematics
• Science
• Miscellaneous
• Archives

Want a faster answer?

Main page: Help searching Wikipedia

   

How can I get my question answered?

• Select the section of the desk that best fits the general topic of your question (see the navigation column to the right).
• Post your question to only one section, providing a short header that gives the topic of your question.
• Type '~~~~' (that is, four tilde characters) at the end – this signs and dates your contribution so we know who wrote what and when.
• Don't post personal contact information – it will be removed. Any answers will be provided here.
• Please be as specific as possible, and include all relevant context – the usefulness of answers may depend on the context.
• Note:
  • We don't answer (and may remove) questions that require medical diagnosis or legal advice.
  • We don't answer requests for opinions, predictions or debate.
  • We don't do your homework for you, though we'll help you past the stuck point.
  • We don't conduct original research or provide a free source of ideas, but we'll help you find information you need.

Ready? Ask a new question!

How do I answer a question?

Main page: Wikipedia:Reference desk/Guidelines

• The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.

See also:

• Teahouse
• Help desk
• Village pump
• Help manual

January 27

Best way to dissolve methane in a liquid that mixes with scintillation fluid

Hi,

I'd like to be able to "trap" 14-C methane in some kind of solvent so that I can mix that solvent with scintillation fluid and be able to determine radioactivity. What would be the ideal solvent for this situation? Ideally, I'd like a liquid that can trap all of the methane in the tube but also mixes with the scintillation fluid.

Thanks a lot for your help.

Ccarlst (talk) 03:50, 27 January 2011 (UTC)

Methane isn't going to be soluble to a great extent in any liquid (it is arguably more soluble in a nonpolar solvent like benzene than in water, but only in relative terms. Its not terribly soluble in either). Furthermore, even soluble gases will never completely dissolve in a liquid. Your best option is to react the methane with something, preserving its carbon, but making that carbon now bound to be part of a liquid compound rather than gaseous methane. I'm not sure how feasible it is based on the equipment you have availible, but something like Free radical halogenation would work; the article lists free radical halogenation as a method used most commonly to create chlorinated methanes like dichloromethane (methylene chloride) and trichloromethane (chloroform) both of which are actual liquids. --Jayron32 04:12, 27 January 2011 (UTC)

Try converting the methane to a methanide salt, which is soluble in polar anhydrous solvents. --Plasmic Physics (talk) 09:07, 27 January 2011 (UTC)

Yeah, but methanide salts would be much more difficult to work with than methyl halides. Alkyl salts are metastabile at best, I would expect all of them to be so highly alkaline as to be pyrophoric in air. The nice thing about methylene chloride is that it is fairly easy to work with (it is a low-boiling liquid, so you'd have to work in a cool room, but otherwise is very unreactive). --Jayron32 14:00, 27 January 2011 (UTC)

What's the source of the methane? Does the gas also contain other methane (not containing C-14) and is there anything else that does contain C-14? Google gives lots of literature hits for liquid scintillation of C-14 methane over the past few decades (sample search: 14c methane scintillation). Doesn't necessarily answer your direct question (as others have noted, it's "hard"), trying to figure out solutions to the larger situation. DMacks (talk) 09:36, 27 January 2011 (UTC)

At the moment, the source of the methane is a 1mCi vial I bought from American radiolabeled chemicals- well, at least they say is 1mCi with a specific activity of 50mci/mmol. The reason I am concerned and think that the 1mCi may be off is because according to my calculations, [1mCi X 1mmol/50 mCi X 22.4 ml/1mmol = 0.448 ml] the volume of methane I should have gotten should be around 0.5 ml, when in fact it came in a vial that looks to be about 6-7 ml. They claim there are no other gases there (and they are terrible about answering questions, so I have yet to find out if there is cold methane there too). So, I need a way to test that what they claim is there is actually what is in there. In the future, I was planning to use the 14-C methane in an experiment that is supposed to evolve 14-CO2, which I plan to trap using NaOH and then run in a scintillation counter. Thanks to everyone for your suggestions- it sounds like some of them would work well, but the problem is that it would be hard to do that kind of chemistry in a biology lab..Ccarlst (talk) 01:14, 29 January 2011 (UTC)

Of course, your 22.4 mL/mmol figure presumes the contents of the vial are at atmospheric pressure. It seems to me that if one were going to ship an expensive specialty gas in a small vial, it would be beneficial to have it well below atmospheric pressure so the pressure difference helps maintain the seal. Also, if the vial is supposed to produce a precise amount of radioactivity, they have to have some way to adjust the amount of gas they put in it, so they have to adjust the pressure anyway. Given that, they might as well have low pressure, and adjust the exact pressure when filling the vial, to hit the radioactivity target.--Srleffler (talk) 02:35, 29 January 2011 (UTC)

Geographic center of the world

Hi. I know that the geographic center of the contiguous United States is near Lebanon, Kansas {{coord|39.828175|-98.5795}} Could you, please, tell me the coordinates of the geographic center of the whole world? I searched the internet but couldn't find anything. If you don't know, could a science geek calculate the coordinates using a world map such as File:BlankMap-World6.svg and a good piece of software? --41.178.235.216 (talk) 03:50, 27 January 2011 (UTC)

To my admittedly sometimes muddled mind it seems there is no centre of the surface of a sphere. HiLo48 (talk) 03:54, 27 January 2011 (UTC)

There is, but it's not on the sphere. The center of mass of the earth is located, unsurprisingly, at the center of that sphere, not on its surface. The geographic center is defined as the center of mass of a uniform, two-dimensional cut out of the section of land in question. However, as you correctly note, it makes no sense when dealing with a sphere, only with the (planar approximation) of parts of that sphere does it make sense. --Jayron32 03:57, 27 January 2011 (UTC)

(edit conflict) I mean the center as if the whole world was flat (projected on a surface). It is probably some point in the Middle East but I need the exact coordinates. --41.178.235.216 (talk) 03:59, 27 January 2011 (UTC)

That involves some arbitrary map borders. To make the world appear flat on a map involves choosing edges, which don't actually exist, and flattening curved bits. HiLo48 (talk) 04:02, 27 January 2011 (UTC)

To expand, while a lot of maps do seem to have the Americas on the left, and Asia on the right, this one gives another perspective. HiLo48 (talk) 04:27, 27 January 2011 (UTC)

The proper way to calculate it over the whole globe is to use the (two-dimensional) circular mean. See also land hemisphere, which is nearly synonymous. --Tardis (talk) 05:02, 27 January 2011 (UTC)

For the centre of a conventionally made "flat" map, you're asking for the intersection of the prime meridian and the equator, this article has a story and pictures of a visit there (it's far out at sea off the coast of West Africa). Many world maps show more of the Northern than the Southern hemisphere, for such maps, the centre would be further north. I guess you could also calculate the centre of all the land masses in the world, this is maybe what's described in Tardis' post above. Jørgen (talk) 08:55, 27 January 2011 (UTC)

Further reading at Extreme_points_of_Earth#Center and geographical center.--Shantavira|^{feed me} 09:01, 27 January 2011 (UTC)

Greenwich, Mecca, or Jerusalem have been regarded as being the centre points of the world. At Greenwich you can stand astride the piece of metal the marks the boundry between the eastern and western hemispheres, and its where GMT comes from. 92.24.187.66 (talk) 12:21, 27 January 2011 (UTC)

Surely, the answer is wherever you are at that particular moment? --Dweller (talk) 14:25, 27 January 2011 (UTC)

Actually, the answer is wherever I am at that particular moment! --Stephan Schulz (talk) 17:17, 27 January 2011 (UTC)

I assume DWeller meant where you are. DMacks (talk) 17:25, 27 January 2011 (UTC)

Actually, I suspect it has something to do with the barycenter of the planet. Damn you, chocolate! --Stephan Schulz (talk) 17:33, 27 January 2011 (UTC)

Hmmm, despite the absurdity of it, this question is theoretically answerable. Imagine you make a globe where all the world's land surface is accurately represented by a homogeneous layer of material. Wrap it in a much lighter layer over the whole sphere to hold it together. Now put it on a smooth floor and let it roll to a stop. The point on the bottom should be "the center point of all land on earth", and the point on top should be "the center of all Earth's oceans". An industrious person could probably do this on a computer in a jiffy, but alas... Wnt (talk) 18:01, 27 January 2011 (UTC)

I think that method would find a centre very close to (but not exactly at) the centre of the land hemisphere mentioned above by Tardis. --Tango (talk) 22:12, 27 January 2011 (UTC)

According to this web page, "If you've ever wondered where the geographic center of the world's land area is, the coordinates are latitude 34 deg 26 min North and longitude 27 deg 19 min East. This puts it in the eastern Mediterranean Sea about halfway between Athens and Alexandria.".Looie496 (talk) 01:01, 28 January 2011 (UTC)

I wonder if what they mean by that is "the point at which the sum of the distance (along the surface) from there to the center of every 10 arc-minute² area of land (maybe defined as just "not-ocean"?) is minimized." WikiDao ☯ 01:32, 28 January 2011 (UTC)

If we define the problem as:

${\vec {x}}_{center}=\int _{-\pi /2}^{\pi /2}\int _{0}^{2\pi }{\vec {x}}(\theta ,\phi )\delta _{land}(\theta ,\phi )\,sin(\phi )d\theta d\phi$

Where $\delta _{land}(\theta ,\phi )$ equal 1 over land and zero otherwise, and then take the ray extending from the origin through ${\vec {x}}_{center}$, I get that it intersects the surface at 43.5222 N and 28.5470 E. That happens to be in Bulgaria at the edge of the Black Sea. That's a well-defined, non-trivial answer, though admittedly it is about as arbitrary and useless as any other answer. Dragons flight (talk) 05:04, 28 January 2011 (UTC)

That's actually the same definition that I had in mind above, though I had a well justified fear that I might foul up with three-dimensional polar coordinates, and I don't know where you found the delta(land) database.

To recap, the definitions so far cover:

• The center (barycenter) of the Earth
• The center of the land hemisphere drawn to contain the most land and least sea
• The location where you could site a "Transcontinental Congress" so that the total travel miles of delegates from evenly sized small districts throughout all the land on Earth (via great circle route) would be minimized
• The location directly above the spot deep inside the Earth where you could site the Transcontinental Congress so that the total teleportation miles of all delegates (via straight lines) would be minimized

To this I can imagine adding at least one more:

• The location directly above the spot where the barycenter of the Earth would be, if all volatiles (water, air, ice, maybe fossil carbon) were stripped away from the planet, as projected from the current barycenter.

This last one, in essence, is a way to average where the center of all the Earth's water is taking into account how deep the oceans are at each point, or where the center of all the Earth's land is taking into account how high the mountains are.

All these methods, except for the trivial answer of the barycenter, imply a dipole in the Earth between land and sea, with one centered at one spot and the other centered at the diametric opposite point.

What seems extra surprising to me is that there seems to be a close analogy between this and the philosophical issues of act utilitarianism (the "transcontinental congress" methods) and rule utilitarianism (the land hemisphere method); there are different ways of trying to decide on the "true" center depending on exactly how the "greater good" is defined. Wnt (talk) 06:11, 28 January 2011 (UTC)

For practical reasons I would add

• The location directly above the spot deep inside the Earth where you could site the Transcontinental Congress such that the sum of each delegate's squared teleportation miles would be minimized.

Least squares is a lot easier to compute, because it's just the arithmetic mean of all the land points in Cartesian coordiantes. To minimize the sum of absolute distances you'd probably need some kind of iterative approximation, and are we even sure that a local minimum would also be global? –Henning Makholm (talk) 06:37, 28 January 2011 (UTC)

Hmmm... I didn't think about that. I assumed that the "teleportation miles" (4th definition above) would work out to be the same as the average of all land areas as calculated by Dragons flight above, but is that true for the summed distance, or the summed squares of the distances, or...? Wnt (talk) 16:02, 28 January 2011 (UTC)

In one dimension it is easy to see that least squares gives the arithmetic mean, and least absolute distances gives the median. It is still the mean for least squares in higher dimension, but it is not clear to me that the median has a similarly nice generalization. –Henning Makholm (talk) 11:10, 29 January 2011 (UTC)

I don't understand the maths above, but the way I would do it would be for every point on the earth, you calculate the weighted sum (eg inverse square or whatever you choose) of the surface distance of every other point on the earth *provided* they are not more than half a circumference away, with 0 for water and 1 for land. Then the point with the highest weighted sum is the "centre of the world". What wrong with that? 92.29.125.152 (talk) 14:02, 30 January 2011 (UTC)

There is nothing wrong with it, except that it can be difficult to find the point with the best sum without doing an inordinate amount of work. (Note that nothing on a sphere is more than half a circumference away). Basically what we're discussing is which difference it makes to choose different formulas for the "weights" (in your terminology), since there are choices that makes it possible to find the resulting center with less effort than computing your sum for each possible point on the globe. –Henning Makholm (talk) 14:32, 30 January 2011 (UTC)

ORME Orbitally Rearranged Monoatomic Elements

There is some ideas on the web, but what is actually "Orbitally Rearranged Monoatomic Elements (ORME)"?, there is no information on english Wikipedia, usually it the best place to serch, would you explain please?Ghrmsn (talk) 06:23, 27 January 2011 (UTC)

It looks like it's not something real. One user attempted to write an article about it: User:Sloth_monkey/ORMEs and was deleted : Wikipedia:Articles_for_deletion/ORMEs and Wikipedia:Articles for deletion/Monatomic elements. Maybe you can glean some information from the deletion comments and the article draft. Ariel. (talk) 08:59, 27 January 2011 (UTC)

Actually it is true, there is information un many languages, although, I don't know why Wikipedia is not accepting this info. There is many more things less important or ridiculus, but not this, it is for real, probably some kind of goberment complot, trying to hide information.Ghrmsn (talk) 16:34, 28 January 2011 (UTC)

See WP:FRINGE and WP:RS for starters. DMacks (talk) 17:17, 28 January 2011 (UTC)

Mean distance in a square

Maths have always been my Achilles' heel, so I'm having trouble trying to figure out a problem with a square.

Let's imagine a big 100 sq. ft box divided into one hundred 1 sq. ft boxes. In the centre of each small box there is a candle. If I were to calculate the average distance from each candle to all other candles, would I get the same result for all the candles, or would there be a divergence depending on the location of the candles within the big box? Intuitively, I think candles located along the edges would have a greater average distance to all other candles, but I can't find a way to prove it mathematically.

Thanks to whoever can help. Leptictidium (mt) 08:55, 27 January 2011 (UTC)

When you have a problem like this simplify it. Imagine a line with just 3 squares in it, and calculate the average distance for each of those 3 candles. Ariel. (talk) 09:04, 27 January 2011 (UTC)

It would be ideal for a simple Basic program, such as SmallBasic. 92.24.187.66 (talk) 12:54, 27 January 2011 (UTC)

It's not clear from your phrasing what geometry you mean, but you will get different answers for a 1X100 rectangle of boxes compared to 10X10. The issue at play here is the perimeter to area ratio, and more generally the notion of boundary_(topology). For instance, if you put the small boxes on the surface of a sphere (and measure distance along the same surface), then all candles would share the same mean distance to the others. SemanticMantis (talk) 15:06, 27 January 2011 (UTC)

First, it has been noted that there are 100x100 10x10 1 square foot boxes in a 100 square foot box. Regardless, this is a very simple program to write. The output for a 5x5 box is:

3.31  2.83  2.67  2.83  3.31 
2.83  2.31  2.14  2.31  2.83 
2.67  2.14  1.95  2.14  2.67 
2.83  2.31  2.14  2.31  2.83 
3.31  2.83  2.67  2.83  3.31

As you can see, the mean distance to all other candles is not constant. -- kainaw™ 15:19, 27 January 2011 (UTC)

It is interesting to see the calculations, thanks. Also, I think you mean 10X10 1 square foot boxes in a 100 square foot box :-) SemanticMantis (talk) 18:29, 27 January 2011 (UTC)

And in the limit (as you use smaller candles and pack more of them) the average distance from a corner is exactly twice the average distance from the center. This is because to compute the average distance from the center, you can cut the square into 4 smaller squares, and only consider one of them by symmetry. So the average distance from the center is the same as the average distance from the corner of a square with half sides. 98.248.42.252 (talk) 18:57, 29 January 2011 (UTC)

Religion, mental health and education

Is religion correlated more positively with mental health in people with higher education? I ask this because it would test my hypothesis that approaching the ultimate nature of humanity or the universe is hazardous to a person's mental health, and that religion is a way of defending against that hazard. (I agree with Richard Dawkins' assertion that religion itself is a mental illness, but I'm not sure I agree that it's a more severe mental illness than the alternative.) NeonMerlin 11:05, 27 January 2011 (UTC)

Who's to say what the "ultimate nature of humanity or the universe" is? I don't think physicists are more crazy than other people, except in cartoons. 92.24.187.66 (talk) 12:56, 27 January 2011 (UTC)

Is this the religious version of "You can't handle the truth"? HiLo48 (talk) 14:03, 27 January 2011 (UTC)

I read an article about this in the last few weeks; the author claimed that religion (particularly the fervent, born-again type) is measurably more popular among undergraduates at Britain's most prestigious universities than at other, less rarefied institutions. His interpretation was that unusually bright people under intellectual stress are more likely to turn to religion. Anecdotal and unscientific, but it did strike a chord. It could have been in The Guardian or maybe the Financial Times; I can't find anything online ATM but I'll try to dig up a reference for you. Karenjc 16:04, 27 January 2011 (UTC)

Sorry, tried hard but couldn't find the original article - my post-Christmas recycling binge seems to have claimed it. Karenjc 10:07, 28 January 2011 (UTC)

Interesting comments regarding "unusually bright" students turning more to religion. From what I've seen, most studies show a strong negative correlation between "intelligence" (as measured by IQ) and religious faith. -- Mesoderm (talk) 16:16, 27 January 2011 (UTC)

Yes, given the strong negative correlation between religiousness and intelligence, it presumably isn't those students' intelligence that's causing them to turn to religion, so much as their highly competitive, high-stress environment. And a high-stress environment does increase a person's risk for developing other forms of mental illness (see Causes of mental disorders), so a stress/religiousness correlation would seem to fit Dawkins' religion-as-mental-illness paradigm in at least that regard. Red Act (talk) 17:36, 27 January 2011 (UTC)

Were I to try and identify a confounding variable in the relationship between university status and proportion of students who are religious believers, I would look at the number of international students. High status universities in the UK attract international students from all over the world, including countries with much higher religious observance rates than the UK. Itsmejudith (talk) 15:50, 28 January 2011 (UTC)

Correlation is not causation (Propter hoc fallacy), and doubly so when dealing in false syllogisms. If I say "I love you, and I love cheese, therefore you are cheese" you can see the rediculous leaps of logic needed to reach that conclusion. However, I have no idea why, replacing random nouns and verbs in that statement, it suddenly becomes a reasonable proposition. Lets try it "Stress causes religiousity, and stress causes mental illness, therefore religiousity is mental illness." Nope, its still a patently stupid conclusion to reach. --Jayron32 18:05, 27 January 2011 (UTC)

I did not use that syllogism. You incorrectly extrapolated what you thought I meant from what I said. I will explain what I meant more clearly.

Biological contributions to the etiology of mental illnesses are of course very important, but to make the logical content of the following clearer, pretend that stress is the only cause of mental illness. Then if you take Dawkins' paradigm as being valid, you can use the syllogism "the cause of mental illness is stress, religiosity is a mental illness, therefore the cause of religiosity is stress" to predict that there is a positive correlation between stress and religiosity. So if a study shows that there really is a positive correlation between stress and religiosity, that suggests that the model of religiosity as a mental illness may have some predictive value, in that it could have enabled you to predict the positive stress/religiosity correlation ahead of time, from just knowing the cause of mental illness. This alone isn't enough to conclude that it's useful to model religiosity as a mental illness, since it may be purely coincidental that the religion-as-mental-illness paradigm led to the correct prediction that there is a positive stress/religiosity correlation. That's especially true because mental illness in reality has multiple causes, so one has to deal with messy correlations instead of clean Boolean logic as in the syllogism above. But this could validly be used as one element of a set of information used in determining how valuable it is to model religiosity as a mental illness. Red Act (talk) 21:13, 27 January 2011 (UTC)

There is a strong correlation between citing studies linking low IQ to a group of people 'and' your personal dislike of these groups. Quest09 (talk) 18:10, 27 January 2011 (UTC)

Red Act (talk) 21:15, 27 January 2011 (UTC)

This isn't quite what you asked for, but I did stumble across this study that attempted to measure the effect of religion on physical (rather than mental) health while also controlling for the effects of age, income, education, etc. They found that religious practice had a positive and statistically significant association with health even after controlling for other variables. (Probably not surprising.) However, they also found that those holding self-reported "conservative" ideologies were on average less healthy than those with moderate / liberal religious beliefs, even after controlling for other variables. They speculated that religious conservatives may be more reluctant to seek out medical treatment when problems arise. They also found that people with higher levels of education where more likely to engage in regular religious practices (e.g. praying, going to services, etc.), but paradoxically less likely to report feeling "closeness to God". Dragons flight (talk) 18:16, 27 January 2011 (UTC)

The elephant in the room here is, how do you define "mental health". I mean, Jesus and his followers undertook many actions that they pretty well could guess were going to get them nailed to a cross waiting for a cold, cruel end. Any competent mental health professional could argue that that made them "a threat to themselves or others", right? But it was about more than physical survival. Now a person can look at a far-gone mental patient and say that there the pattern of actions is totally pathological, not productive, not for some grand and noble purpose, but how can anyone accurately draw a precise line between what behavior is less than human and what is more than human? Wnt (talk) 06:23, 28 January 2011 (UTC)

Though the behavior of Jesus and the apostles is not really germane for talking about modern religion. Most practitioners are not founders. Practically zero Christians actually behave like Christ is supposed to have. --Mr.98 (talk) 20:16, 29 January 2011 (UTC)

Anal sex in the 1800s

I watched Total Eclipse (film) the other day and was confused about something. When Verlaine is in court and a doctor tests whether he was having anal sex, the doctor says there was proof that he was having both active and passive sex. I understand how the doctor could tell that Verlaine was having passive sex, but how could he ever know that Verlaine was also having active sex? Or were they just saying that to further incriminate him...? Thanks, this has been bothering me for some time! 129.3.178.228 (talk) 14:06, 27 January 2011 (UTC)

Was something like syphilis involved? (Which was common enough at the time) Wnt (talk) 18:11, 27 January 2011 (UTC)

I can't find anything saying he ever had syphilis, no. 129.3.151.117 (talk) 18:45, 27 January 2011 (UTC)

According to the article on Verlaine at French Wikipedia he did have syphilis. --Antiquary (talk) 23:39, 27 January 2011 (UTC)

I've heard first hand accounts about how doctors belonging to certain religious groups would tell adolescent males (from families that also belonged to that group) that they had "symptoms" of having masturbated so they should cut it out. Obviously, chances are the majority of males by a certain age have at least tried masturbation so the doctor wasn't really taking a wild guess. Maybe this was a similar case where they were just making a broad assumption, obviously chances were probably less but that doesn't change much. Vespine (talk) 00:12, 28 January 2011 (UTC)

Medical textbooks of that age did actually sometimes give lists of symptoms, as here. ("...circulatory disturbances of both motor and sensory nature; irritability; insubordination and outbursts of inexplicable anger... a decided bashfulness and reserve in society; averted gaze; and lack of manly bearing... a tendency to avoid company or the joining in youthful sports, but rather to retire alone or with a single companion, upon whom the suspicion of being an accomplice should rest; in study hours there is dullness, drowsiness, preoccupation, faraway gaze, and lack of application, with often pronounced weakness of memory and absent-mindedness..." and it goes on.) Marnanel (talk) 00:46, 28 January 2011 (UTC)

The doctor was talking bullshit obviously, he could not know that. --Lgriot (talk) 13:12, 28 January 2011 (UTC)

How long after the sex act did they perform the "test". I don't want to be gross, but bathing wasn't exactly a big thing in 19th century Paris, right? Matt Deres (talk) 22:39, 28 January 2011 (UTC)

Sky photography

I stumbled upon this image during one of my Wikipedia strolls, and I was surprised to learn that it was a photograph. It looked like a negative or even a diagram to me. To what purpose would an astronomer use such a picture as opposed to a more usual (to my lay eyes) photograph such as this one ? What are those "negative" images useful for ? Thank you, have a nice day. 130.79.160.112 (talk) 15:33, 27 January 2011 (UTC)

Many astronomers would find it simpler to pick faint black specks out of a white background than vice versa, particularly if you're working by hand rather than with digital photo processing equipment. — Lomn 15:47, 27 January 2011 (UTC)

Technically, it is the negative (or a print of a photograph of the original plate); the 'raw' image collected on film at the telescope would look exactly like that, as bright stars would create dark spots. From the standpoint of working with the image, it's usually easier to pick out a small dark spot on a white (or clear, on the original film/plate) background than it is to pick out a slightly-less-dark spot on a black background. (This applies both to manual examination and to automated discrimination.) When printed non-photographically, the negative version uses less toner (or ink), and is more forgiving of printing flaws. When annotating the image, it's much easier to add dark text and symbols to the clear background (particularly when dealing with physical copies of the image) than it would be with a positive image. TenOfAllTrades(talk) 16:32, 27 January 2011 (UTC)

When I was measuring faint structures in deformed minerals on electron micrographs (more decades ago than I care to remember) I always used the negatives directly - you always lose some information when you print. Mikenorton (talk) 18:11, 27 January 2011 (UTC)

(Edit Conflict) In addition to the previous answers, an important factor is that every time a non-digital image is processed (such as when making a positive print from an original negative) degredation of the image occurs. Similarly, every extra lens that an image has to pass through will reduce the inherent quality of the image. For these reasons, professional astronomers from the earliest use of telescopes and of astrophotography generally did not add an extra lens into their eyepieces usually necessary to convert the inverted image into an upright one, and worked with original negative plates (film tended to distort more so was not used for astrometry). Thus astronomers have always been used to dealing with such images, which also have the advantages previously described. 87.81.230.195 (talk) 18:16, 27 January 2011 (UTC)

Even just on my computer screen, I find it a lot easier to see faint spots when it is black-on-white than it is when it is white-on-black. I suspect the human eye is measurably better at the former than the latter. --Mr.98 (talk) 20:37, 27 January 2011 (UTC)

I asked a similar question while studying for my (astrophysics) degree. Yes, it is easier to pick out faint detail (pale grey wisps) against a light background. Also, you get less distortion/artifacts during measurements, if using the original (negative) photographic plate. Astronaut (talk) 16:06, 29 January 2011 (UTC)

Thank you very much for those explanations ! (says the OP on another computer) Have a nice day, 85.169.175.167 (talk) 17:23, 30 January 2011 (UTC)

incipient fusion

A google search suggests that in geology or materials science or something like that, there is a concept called "incipient fusion". But Wikipedia has no article with that title. Can someone say what it is?

There is a joke I heard many years ago, in which a school principal visits a class and tries to ascertain what they're learning. He asks the pupils what they would expect to find if they dug down to 4000 miles below the ground. Nobody could say anything. Then the teacher assisted. He asked them:

"What is the state of the center of the earth?"

They all responded in perfect unison:

"The center of the earth is in a state of incipient fusion."

Michael Hardy (talk) 19:10, 27 January 2011 (UTC)

I don't think that's a joke, it's just an incorrect fact. You can read the definition of "incipient" at Wiktionary. "Incipient" means that something is just starting. The material at the center of the Earth is part of the inner core, and is a solid (or solid-like) mass of mostly iron and nickel. Some scientists have speculated that radioactive or nuclear processes deep inside the Earth may contribute to the net planetary heat flux; but I have never heard a reasonable geologist pass off fusion as a plausible nuclear reaction occurring inside the Earth. Nimur (talk) 19:22, 27 January 2011 (UTC)

It is a joke, but it's true: It sometimes (often) happens that students learn to recite memorized answers to memorized questions, without understanding them. This is just parodying that phenomenon. Michael Hardy (talk) 19:35, 27 January 2011 (UTC)

And, "Nimur", you're missing the point. Nuclear fusion is obviously not what the word "fusion" refers to in this case, as you'll see if you google "incipient fusion" in quotes. It's about a different kind of fusion. "Fusion" generally means joining together. That can refer to lots of different things. Michael Hardy (talk) 19:36, 27 January 2011 (UTC)

Fusion originally means "melting" (hence Heat of fusion and Fuse (electrical)), and by extension to join by melting (and resolidifying). -- 119.31.126.67 (talk) 00:45, 31 January 2011 (UTC)

I never heard this one, but it ties in with the question about Jupiter that was asked last week or so - as very large gas giants approach brown dwarf status during their initial formation, one might say one expected "incipient fusion" near their centers? (Whereas Earth, with a big iron core, is not fusing anything, no matter what) My feeling on reading this is that the joke implies their teacher has drilled something into the kids which is just plainly wrong. Wnt (talk) 19:20, 27 January 2011 (UTC)

For earth-specific geological-scale nuclear reactions, see geothermal gradient - heat sources. Most of the (nuclear-related) heat is simple radioisotope decay - more like an RTG than a reactor. A few scientists speculate that there may be fission in the deep mantle, and many scientists believe isolated patches of Earth's crust have experienced natural nuclear fission. Nimur (talk) 19:25, 27 January 2011 (UTC)

I think this thread of discussion is going away from the OP's question. From the brief google search I did, incipient fusion seems to be to do with materials joining together, not with energy release as a result of nuclear fusion. --Tagishsimon (talk) 19:31, 27 January 2011 (UTC)

From an article on brick making "incipient fusion, when the clay particles become sufficiently soft to stick together in a mass when cooled" [1] --Tagishsimon (talk) 20:43, 27 January 2011 (UTC)

Thank you, Tagishsimon. (Amazing how Nimur and others missed the point so clumsily. I wonder if they know that nuclear fusion has only been known for less than a century but the word "fusion" is (obviously) much older than that.) Michael Hardy (talk) 00:50, 28 January 2011 (UTC)

Irrelevant here, I guess, but it might be worth pointing out that yet another meaning of "fusion" is simply melting, as seen in the term heat of fusion. --Anonymous, 11:27 UTC, January 28, 2011.

this reminds me of one of the messages in Richard Feynman's “Surely You’re Joking Mr. Feynman!”, which was that students should be taught to understand and not only to memorise. The OPs 'joke' is an example of what happens when taught only to memorise. see http://www.hpcnet.org/cgi-bin/global/a_bus_card.cgi?SiteID=305793 —Preceding unsigned comment added by 80.168.88.74 (talk) 13:47, 28 January 2011 (UTC)

Practicality of experimental procedure for measuring microwave wattage

Is there anything about the following procedure that in actual practice would make its results significantly inaccurate? Thanks in advance.

Procedure for finding the wattage of a microwave with no labeling whatsoever:

1) Place 0.1 kg (100 mL) of water in a beaker and measure the initial temperature T1.

2) Heat water in the microwave for 10 s.

3) Quickly measure temperature of water T2 and find dT = T2 - T1.

4) Calculate energy transferred to water Q = m*c*dT using c = 4.187e+3 J/kgK.

5) Divide Q by 10 to get wattage (J/s).

76.27.175.80 (talk) 19:15, 27 January 2011 (UTC)

It sounds plausible, but it will need experimental checking. For example, this is a net measurement of the wattage absorbed by the water, but the microwave packaging probably gives a gross wattage to make it sound bigger, and so as not to overly dwell on whatever losses occur in the walls of the oven, etc. Packaging for food probably follows the manufacturer's packaging.

And of course, be sure to stir the water thoroughly. Wnt (talk) 19:24, 27 January 2011 (UTC)

100 mL of water beaker might not be enough to get average energy (assuming a standard kitchen-sized microwave oven, with a cavity of a few 10s of cm in each dimension). One of the reasons ovens now have carousels and other waveguide tricks is because the microwaves are not evenly distributed in the cavity (and these tricks only partially compensate). The plausible values for a household model do not cover that large a range, so you need to make sure you are not sitting in a particularly high-energy or low-energy region (being in a cool spot could create noticeable experimental error). How does your approximately 4x4x6 cm sample compare to the wavelength of microwaves, and are you likely have Nyquist–Shannon sampling theorem problems? DMacks (talk) 19:47, 27 January 2011 (UTC)

You want as big a ΔT as possible without errors from evaporation. So you need to do some preliminary experiments to see how fast the water heats up. A big hint: you don't really want the water to go above 60 °C (140 °F), or you'll have all sorts of practical problems in the measurements, not to mention safety issues if you're doing this as a class experiment. But don't restrict yourself to 10 seconds heating, you might get better results from a longer time. Physchim62 (talk) 19:59, 27 January 2011 (UTC)

In addition to any experimental error in finding the average power delivered to the food, you must also consider what the power will be used for. Naturally the oven will not be 100% efficient, so the power delivered to the food is less than the power drawn from the electrical mains. If you are trying to determine whether the circuit breaker supplying the oven is adequate, this must be allowed for. Also, recipies that mention the power of the oven might refer to the actual power delivered to food, or to the power drawn from the mains; you will have to figure out which meaning the recipie uses before deciding upon any modification to the recipie. Jc3s5h (talk) 20:04, 27 January 2011 (UTC)

It would be interesting to correlate the calculated absorbed energy with the actual calculated electrical draw (an ammeter on the mains line and its voltage). I don't know the typical efficiency of a consumer-grade magnetron, but that sounds like something one could find in a library or online reference (maybe even the spec sheet of an actual device?). And then consider that there are one or more motors and lights being powered in addition to the microwave source itself. Gauge the overall efficiency of the oven as a food-heating device. DMacks (talk) 20:15, 27 January 2011 (UTC)

I checked an old microwave cookbook I've got lying around, and the test there is:

1. Place two cups (500 ml) of room-temperature water in the microwave.
2. Set the microwave for a long period of time (ten minutes or more).
3. Measure the time until the water starts boiling.
4. Find the nearest time in the cookbook's chart. This gives the approximate wattage of the microwave.

Unfortunately, the page containing the chart is missing.

This procedure has some practical advantages over yours: the greater quantity of water increases absorbtion of microwaves, while the greater heating time makes for a more accurate measure of temperature (and the use of "boiling point" means you don't need a thermometer, but does introduce errors from evaporation). --Carnildo (talk) 00:49, 28 January 2011 (UTC)

Thanks all for the responses. I tried out the experiment as I described it, but with 500 mL (0.5 kg)and for 90 s. The rotating carousel carried the pyrex pitcher over a good volume of the space in the microwave continuously, so I assume I got a good sampling of whatever "hot" and "dead" zones there were in the microwave. The initial temp was 15.6 C and the final was 48.9 C for a dT of 33.3 K. So the total energy was 69.7e+3 J which over 90 s comes to about 774.6 W. I found the documentation for the microwave, which claims it's an 1100 W microwave, which, if it's true, means that it was about 70.4% efficient at putting its energy into my water. ~70% seems realistic to me, and not knowing what kind of stuff people will be putting into their microwaves, it seems logical for the manufacturer to advertise the wattage made available instead of any estimated final wattage absorbed by the food. 76.27.175.80 (talk) 17:51, 28 January 2011 (UTC)

Have you repeated the experiment, not just with the same water volume and time to see if you get the same temperature change, but with different water volumes and times to see if you get the same computed value? -- 119.31.121.84 (talk) 02:16, 31 January 2011 (UTC)

For maximum power transfer from the waveguide to the water, the water in the cavity (oven space) must present a matched load to the waveguide. In this case, the same energy will be dissipated in the water load as in the anode of the magnetron. Im not sure how microwave ovens powers are specified: Is it the maximum power that can be transferred into a matched load?--92.25.98.49 (talk) 23:05, 28 January 2011 (UTC)

Marketing can usually be counted on to trumpet the best case scenario. 76.27.175.80 (talk) 20:26, 29 January 2011 (UTC)

Safe to store water in garage?

We have some blue 55-gallon water barrels to store water for an emergency. I have heard that you should not store these in the garage because of gasoline fumes (assuming your car is in the garage). Are there some authoritative sources that state that water barrels should not be in the garage? I cannot find any. All I can find is to make sure the barrels are not sitting directly on concrete. Thanks, Alanraywiki (talk) 20:05, 27 January 2011 (UTC)

Don't both your drinking water barrels, and any gas cans you have laying around, have lids that seal? APL (talk) 20:27, 27 January 2011 (UTC)

Yes, the water barrels are well sealed. The plastic on the barrels is thick. I think the permeability of the plastic may be the concern. But, I can't find any sources to corroborate. Alanraywiki (talk) 20:39, 27 January 2011 (UTC)

The LD50 of gasoline would require a 75 kilo person to drink about 1.5 liters of it to have a 50% chance of dying. That's a lot of gas to seep through thick plastic to even get in the ballpark. Like using non-food-grade barrels for this kind of thing, it seems like a minor concern if you change the water now and then and don't make a habit of undergoing emergencies. --Sean 20:55, 27 January 2011 (UTC)

The LD/50 isn't the only issue with gasoline toxicity, I'm pretty certain people have been seriously injured by less due to chemical burning of the esophagus and stomach. The listed symptoms at drugs.com seem to confirm this: abdominal pain, bloody stool, vomiting (with possible hematoemesis), throat swelling, difficulty breathing, ect. It also says expected treatment will probably include an endoscopy to check for burns. That said, to the original question, with that much water in an impermeable container I wouldn't worry personally, the only problem if a small amount of vapor did seep in would be one of taste. Keep in mind that garages typically aren't innundated with fumes and are far from airtight. 65.29.47.55 (talk) 21:40, 27 January 2011 (UTC)

I cannot see the logic of the alleged problem. Gasoline isn't that sneaky. HiLo48 (talk) 21:04, 27 January 2011 (UTC)

Maybe they mean the exhaust fumes? And maybe it's not a "it will kill you" but a "it will taste really unpleasant" thing. Just guesses. Vespine (talk) 21:31, 27 January 2011 (UTC)

With small amounts of gasoline, I'd be more worried about carcinogenicity than acute toxicity. Gas contains significant amount of benzene.

The scary thing about carcinogens is that you can never be sure whether they've hurt you or not. With a lot the standard acute poisons, say cyanide or strychnine or carbon monoxide, if you live 48 hours, you're probably over the hump (not a guarantee, I suppose, but the major concern is over). With benzene, who knows? It could come back to haunt you years later.

(That's not to say that the acute poisons are actually better. In an emergency situation where I had to drink contaminated water to live, I'd probably pick the one with gas in it over the one with cyanide.) --Trovatore (talk) 06:36, 28 January 2011 (UTC)

If you're in the sort of emergency where you need hundreds of gallons of fresh water that you can't get any other way, minor contamination from exhaust fumes would be the least of your worries! Physchim62 (talk) 10:52, 28 January 2011 (UTC)

Why can't the barrels be placed on concrete? If water is in a closed, non-permeable container (which all water barrels should be, at least here in Finland), the placement shouldn't matter at all. Of course you do'nt want them to freeze or get a funny taste from sitting in direct sunlight. --Albval (talk) 10:29, 28 January 2011 (UTC)

Smallest meaningful length

Hello. The Planck length is the length scale at which the structure of spacetime becomes dominated by quantum effects. But, unlike the Planck time, it is not seen as the smallest unit which can exist. What is the smallest possible distance which can exist? Thank you. Leptictidium (mt) 20:42, 27 January 2011 (UTC)

Sorry to be pedantic, but you'll have to qualify the meaning of 'exist' in this context. For example, operating under mathematical realism, the so-called 'real numbers' are actual real entities, and there is no such thing as a smallest distance, i.e. there is no smallest positive real number. You may be interested in exotic types of math where true infinitesimals exist.SemanticMantis (talk) 21:28, 27 January 2011 (UTC)

As is touched on in the last paragraph of Planck time#Physical significance, and the first paragraph of Planck length#Physical significance, the physical significance, if any, of either one of those quantities is debatable. There are various theories that predict various things, but physicists really do not yet have a solid understanding of what goes on at that scale or smaller. Red Act (talk) 21:38, 27 January 2011 (UTC)

Possibly, a smaller distance than the planck length cannot be measured due to quantumn effects. To discuss smaller distances would not make sense, as it is impossible to distinguish fractions of this distance from each other. Like quantumn super position, you can't measure it, but it does exist; smaller distances cannot be measured with any certainty, but they do exist, for different reasons of course.

Statistics play a major role, you're simply cannot be certain of the absolute length, if it is smaller than the planck length.

If the planck length is the smallest quantisisable distance, then would that put a cap on the maximum energy of a photon which can be quantisised? --Plasmic Physics (talk) 22:26, 27 January 2011 (UTC)

Yes, there's an energy limit. The nature of a photon as we currently understand it wouldn't make sense at energies above the Planck scale. Red Act (talk) 22:56, 27 January 2011 (UTC)

Isn't the photon-as-we-know it supposed to last only up to the electroweak scale (far below Planck)? –Henning Makholm (talk) 00:46, 28 January 2011 (UTC)

I'm way out of my depth here, but after reading electroweak interaction and electroweak epoch, and noting that the expected mass of the Higgs boson is around that of the electroweak scale (so that energies higher than that can't necessarily be made to "disappear" by just doing a Lorentz boost), and reading that in theories with extra dimensions, the fundamental scale of gravity is lowered from the Planck scale to the electroweak scale[2] (again making it impossible to make higher energies "disappear" with a simple Lorentz boost), I'm thinking you're probably right. Red Act (talk) 01:47, 28 January 2011 (UTC)

What you said about energies higher than the electroweak scale not being boostable is not correct. I don't understand how you got to that conclusion but I know it is not correct. 71.101.41.73 (talk) 04:46, 28 January 2011 (UTC)

The link above says that in theories involving extra dimensions, the fundamental scale of gravity is lowered from the Planck scale to the electroweak scale. My thinking was that whenever you get to a scale where you need to take gravity into account in any way, you can't simply apply a boost to the description of a high-energy photon such that in the new frame of reference, the high-energy photon simply looks like a normal low-energy photon. The point being that gravity isn't something that takes place within a simple Minkowski space (although linearized gravity can be treated that way), so expecting to be able to apply an arbitrary Lorentz transformation at that scale and have the physics look the same would seem iffy at best. But like I said above, I'm way out of my depth here. I think I've got a decent grasp of general relativity and non-relativistic quantum mechanics, but I don't even really understand quantum field theory, much less physics beyond the standard model, so if I'm full of shit on this one, I'm completely unsurprised. Red Act (talk) 06:32, 28 January 2011 (UTC)

My ignorance is of about the same order as yours, but what I think I understand is that the problem is not with the photon humming along all by itself through the vacuum, but what happens when it interacts with something else. In the latter case it is meaningful to ask about the energy in the center-of-mass frame. I think the electroweak interaction article says that when this energy is high enough, pertubation-based QED loses validity, and you need to treat the photon as a superposition of W° and B° bosons, which have different interactions. But my grasp of spontaneous symmetry breaking is infinitely fuzzy and heuristic, so don't take any of that as gospel. –Henning Makholm (talk) 07:18, 28 January 2011 (UTC)

Doesn't the energy of a photon depend on your point of reference? — DanielLC 03:11, 30 January 2011 (UTC)

Well, that's certainly true in general when considering a photon traveling through a flat vacuum. What I was trying to look at was the scale at which "flat" breaks down, and what Henning was considering is a situation where "vacuum" doesn't apply (in which case the energy is taken to mean as measured in the center of mass frame). Red Act (talk) 08:53, 30 January 2011 (UTC)

It's far from clear that "smaller distances cannot be measured…but they do exist". String theory postulates additional dimensions that might come into play at distances around the Planck length (nobody really knows), and at least most if not all of the extra dimensions are probably compactified, although I think one or more additional large dimension(s) haven't quite been conclusively ruled out, and even the standard four dimensions of spacetime use a metric tensor that isn't even positive definite. So our whole intuitive Euclidean notion of "distance" may well work very poorly at that scale. Red Act (talk) 23:47, 27 January 2011 (UTC)

January 28

Artemisia absinthium

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. --~~~~

I'm not going to argue this one, because my feeling was that we couldn't have answered it anyway. For most uncommon herbal remedies too little research has been done to tell whether the herb itself is safe or effective, let alone in combination with specific pharmaceuticals. Wnt (talk) 06:27, 28 January 2011 (UTC)

Chemistry and Calculus

Hello. I am in intermediate chemistry at my high school right now. Unlike most of my peers, however, I have already got a solid grasp of calculus. What is a good book for understanding chemistry with the involved calculus (for example, in entropy or enthalpy)? I would like a book to cover chemistry from the very basics (down to Lewis theory even) up because I am only in intermediate chemistry right now. I have had some physics but also not from a calculus perspective. Thanks. 24.92.70.160 (talk) 02:35, 28 January 2011 (UTC)

Sounds like what you need is a thermodynamics textbook. The one I used in college for chemical engineering was by Smith, Van Ness, and Abbott. --shoy (reactions) 03:52, 28 January 2011 (UTC)

Any college-level physical chemistry book should be chock-full-o-calculus. Find the nearest used college book store, or look online for a used book; you can get one on the cheap. --Jayron32 04:16, 28 January 2011 (UTC)

Hadron collisions

Would the collisions be the same (or show the same information)if, instead of TWO atoms colliding AT each other linearly, there were four or eight atoms colliding in the same symmetrical way? —Preceding unsigned comment added by 98.221.254.154 (talk) 05:30, 28 January 2011 (UTC)

In theory it would be the same, as long as you had balanced collisions so there was no leftover momentum. But in practice the messier the collision the harder it is to extract good data from the experiment. Plus it would be nearly impossible to get the timing exactly right. Ariel. (talk) 06:58, 28 January 2011 (UTC)

Does having one linear collision as opposed to a "multi-atomic implosion" also limit the data you can gather? —Preceding unsigned comment added by 165.212.189.187 (talk) 14:41, 28 January 2011 (UTC)

I'm not sure I understand the difference between this and the original question. Essentially, the LHC is all about high energy and high luminosity (collision rate). They collect insane amounts of very noisy data and plug it into subtle statistical models to search for new phenomena. The type of collision doesn't matter too much, except that (as Ariel said) the more complicated it is, the noisier the data you collect. Proton-proton collisions are already complicated and a "multi-atomic implosion" would be worse. Also, in practice it's impossible to arrange collisions of three or more particles. The LHC doesn't aim particles at each other; it just crosses two particle beams and lets them collide as they may. If you crossed three or more beams, the overwhelming majority of collisions would still involve only two particles. -- BenRG (talk) 04:59, 30 January 2011 (UTC)

Firing a gun underwater

What factors determine whether a gun (pistol, assault rifle, whatever) can be successfully fired underwater, or will simply explode as soon as the trigger is pulled? --Kurt Shaped Box (talk) 10:04, 28 January 2011 (UTC)

Mythbusters episode 51 tested four modern firearms. "The entire gun had to be completely submerged in water—all pockets of air must be removed—in order to prevent a possible explosion when fired." No gulls were harmed in the testing of this myth. Clarityfiend (talk) 10:22, 28 January 2011 (UTC)

I have been told that a firearm will explode (burst the barrel or the breach, with danger to the shooter) if anything but air is in the barrel: a bullet which did not leave the barrel due to poor discharge of powder, snow, mud, someone's finger. Mythbusters "disproved" this for a shotgun they tested, but rifles and pistols are not modern shotguns, and older weapons may not have been made to the same standard. WW2 veterans have told me that keeping barrels clean was highly emphasized, to prevent the barrel bursting. Water is so much denser than air that when a bullet traveling 1000 feet per second strikes it it would seem to be as immoveable as concrete. So it is surprising that the bullet somehow instantly pushed the water out of the way without a pressure buildup which bursts the barrel, if the other plugs mentioned would cause the barrel to burst on some firearms. Rifles and pistils sometimes blow up for no known reason, so water filling the barrel would push a marginal barrel over the edge. Edison (talk) 17:07, 28 January 2011 (UTC)

From looking on YouTube (of course there are going to be videos of guys firing guns underwater on there!), various Glocks seem to manage just fine, as does the AR-15 and the Ruger LCP - though the bullet's range is something like 4 feet, or less. The Mythbusters ep (also on YouTube) proved that being shot underwater at this range would probably still be lethal (I guess that you'd have to go for a contact shot, or close to it to be certain). Heh, wonder if SpecOps ever do this? --Kurt Shaped Box (talk) 17:35, 28 January 2011 (UTC)

Naturally there is an article APS_amphibious_rifle --80.176.225.249 (talk) 18:27, 28 January 2011 (UTC)

It is perfectly possible (if not especially advisable) to fire a well-made gun underwater without an explosion, as is stated above. Firing a gun that is only PARTIALLY filled with water might be more of an issue. On the other hand, even the mythbusters tests didn't use frangible rounds: many (if not most) civillian bullets are meant to expand when they hit flesh. Flesh being very similar in density to water, I'd suspect a hollowpoint or JHP round might start to mushroom in the barrel underwater. 65.29.47.55 (talk) 00:55, 29 January 2011 (UTC)

When a gun or rifle of any kind is fired the propellant burns completely (or almost completely) before the projectile leaves the barrel. While the projectile is still in the barrel the barrel is being subjected to maximum pressure available from burning the propellant, and yet the barrel doesn't explode. Clearly, barrels are sufficiently strong to withstand maximum pressure available from burning the propellant. Inserting water, mud or any other solid object into the barrel does not somehow increase the energy available from burning the propellant so there is no reason to expect that doing so will cause the barrel to explode. Dolphin (t) 05:33, 30 January 2011 (UTC)

Full name for invertebrate zoologist "von Linstow" active late C19, early C20?

Resolved

Hi all,
Have I mentioned that my pet peeve is binomial authorities without corresponding biographies? OK. So, "von Linstow" is the binomial authority for Telosentis exiguus. He also appears to be the binomial authority for nematodes hosted in "Salties" Crocodylus johnstoni and Crocodylus porosus.
All that said, who is this "von Linstow" guy? --Shirt58 (talk) 11:57, 28 January 2011 (UTC)

According to this book, his initials are OFB. Hope it helps. --Albval (talk) 12:03, 28 January 2011 (UTC)

And after some more google-searching the guy should be this Otto Friedrich Bernhard Von Linstow (page in Finnish) --Albval (talk) 12:09, 28 January 2011 (UTC)

The above link is to a Finish book shop, for ISBN 9781103982332. Both the Finish bookshop and Amazon indicate that the book is in English, however, the title and front-cover are in a Germanic language. CS Miller (talk) 12:57, 28 January 2011 (UTC)

The book is about helminths, which would agree with Shirt58's original request. CS Miller (talk) 13:02, 28 January 2011 (UTC)

(EC)This gives his dates and the dates of publication of his main work Compendium Der Helminthologie: Ein Verzeichniss Der Bekannten Helminthen, Die Frei Oder in Thierisch. Mikenorton (talk) 13:06, 28 January 2011 (UTC)

His book is on Archive.org, oddly enough. He is listed as a "Stabsarzt," which I believe is an Army medical officer. Seems like an obscure guy who happened to write one of these obscure compendiums that named a few new species? --Mr.98 (talk) 13:43, 28 January 2011 (UTC)

I think so too; he was probably an army doctor with an interest in helminths. Here are some more publications of his; he wrote more than that one book. Ucucha 14:15, 28 January 2011 (UTC)

Wikispecies have what looks to be a very comprehensive list of taxon authorities and a tiny stub on him. (I wish I had known about this last time you asked!) SmartSE (talk) 18:51, 28 January 2011 (UTC)

A biography says that he was born 17. October 1842 in Itzehoe received his medical phD 1864 in Kiel and worked as military doctor in Hameln later in Göttingen he published his book Compendium der Helminthology in 1878 in Hannover and died 3. May 1816 in Göttingen.--Stone (talk) 21:16, 28 January 2011 (UTC)

Oh we have an article Otto Friedrich Bernhard Von Linstow.--Stone (talk) 22:06, 28 January 2011 (UTC)

Resolved. Now, if we can turn our attention to the species H. finlandicus, endemic to Albval's Finland... :-) --Shirt58 (talk) 12:19, 29 January 2011 (UTC)

Fuel efficiency

I know that natural gas and propane both burn cleaner than gasoline but are they as "fuel efficient" as gasoline (i.e. all things being equal, will one get the same "MPG" with NG and Propane as one would with gasoline)? 74.198.17.84 (talk) 14:34, 28 January 2011 (UTC)

There is no way for all things to be equal. Which is why we have MPGe. Rmhermen (talk) 15:41, 28 January 2011 (UTC)

The most similar fuel commonly used to power cars is Liquefied Petroleum Gas, which contains mostly butane or propane: efficiency is around 25% worse with LPG compared to gasoline.[3] --Colapeninsula (talk) 15:56, 28 January 2011 (UTC)

If we're strictly talking propane and natural gas, and comparing "miles per gallon" (really, "energy per volume"), then the comparison is a no-contest win for Gasoline. Have a look at energy density - there are many ways to measure energy "per ___": energy per mass, per volume, per dollar, and so on. This chart of energy density in materials can be sorted by mass- and volume- density. Nimur (talk) 18:14, 28 January 2011 (UTC)

LPG is as the poster above says around 25% less efficient, but in the UK it's compensated for (at least financially) by being about half the price of petrol (gasoline) so you still come out ahead in terms of cost per mile. Downside of course is the installation cost and the loss of space for a spare wheel or in the boot. Exxolon (talk) 16:42, 29 January 2011 (UTC)

Can vets determine the cause of death in a hamster?

Topic says it all. ScienceApe (talk) 15:27, 28 January 2011 (UTC)

In principle, a veterinarian can conduct or order virtually all of the same diagnostic tests during a hamster necrospy that a pathologist would perform as part of a human autopsy. With a certain number of caveats, there is a lot of common ground among most mammals from the level of biochemistry right up to tissue structure.

In practice, there are limitations caused by the smaller size of the animal (it is more difficult to examine and conclusively describe fractures of the smaller bones, less blood and other tissue is available for destructive tests, etc.); the vet may have less access to certain items of specialized equipment, and the resources available for conducting animal necropsies may be limited; and the body of literature and reference materials for diagnosing cause of death may be more limited in animal forensics than it is for humans. As with humans, some causes of death in animals are easier to conclusively diagnose than others. TenOfAllTrades(talk) 15:53, 28 January 2011 (UTC)

Pragmatically, hamsters are fairly disposable as pets. At the outside, they live maybe 3 years. A hamster that lived into his fifth year would be positively Methusalah-like on a Hamster scale. While that does nothing to lessen the emotional loss for someone that suffers the loss of a pet, it does explain why, even if technically feasible, it probably doesn't happen with any regularity that one would autopsy a dead pet which, if it was older than a year and a half, was already beating the average... --Jayron32 17:51, 28 January 2011 (UTC)

In vaguely the same ballpark, my dad had his dead rabbit necropsied. He was very close to her (nursed her back from cancer and an op that involved basically lifting all her innards out, cutting out/off the bad bits, then putting them back in - she lived for another three years after) and he wanted to know what had happened. He just asked the vet to do it. Heart attack, as it turned out. --Kurt Shaped Box (talk) 18:01, 28 January 2011 (UTC)

Yes, they can, if you want to pay a lot of money. Small mammals have been dissected and studied micropically for a long time. Robert Koch in the 1870's would give mice anthrax, then dissect them and examine the liver, lungs, etc microscopically to determine the cause of death. Today medical researchers use mice, hamsters, guinea pigs, etc to study all sorts of infections, cancer, and other ailments, and routinely dissect them postmortem and study sections microscopically and in comparable ways to what a human autopsy involves. It is just not done that often for dead pets, due to the cost. Edison (talk) 21:08, 28 January 2011 (UTC)

Though if you're a hamster breeder, or have a large collection of fancy hamsters, it may be worthwhile to order (and pay for) a necropsy if your beasties start dropping dead inexplicably at a young age. --Kurt Shaped Box (talk) 00:40, 29 January 2011 (UTC)

If the gas pressure decreases what happens with temperature?

What happens with the temperature when the pressure of a gas decreases? I'd like to know this for my job, but it doesn't make sense for me. For example if we have steam at 1.3 MPa and 192 Celsius (just above saturation), according to WolframAlpha, its enthalpy is 2788 kJ/kg (http://www.wolframalpha.com/input/?i=enthalpy+water+at+1.3+MPa+and+192+Celsius). If the pressure would decrease, and I assume the temperature is constant, to 1.0 MPa its enthalpy would be 2809 kJ/kg (http://www.wolframalpha.com/input/?i=enthalpy+water+at+1.0+MPa+and+192+Celsius). So the energy increases which seems strange to me. I thought the energy would decrease when the gas loses pressure. Will the gas temperature actually drop for the energy to be constant or decrease? In my example it is steam in a power plant that passes through a valve and there the pressure drops. Assuming no loss of heat to the surroundings. Wikifantast (talk) 15:36, 28 January 2011 (UTC)

See Ideal gas law. Looie496 (talk) 18:44, 28 January 2011 (UTC)

An assumption is wrong; unless the valve does work on the steam, the energy in the steam can't increase. So, either the steam is no longer at 192 celsius, or work was performed on it (in the form of heat transfer, or some other method). If exactly zero energy was transferred, and there was absolutely no change in volume, the temperature will change (per the pressure-temperature law; with that temperature, you should find an exactly equal enthalpy on both sides of the valve. In reality, energy should be lost: work was performed by the steam as it passes through the valve: some percentage of steam cavitated, liquified, condensed, changed volume, and lost heat to the walls of the valve and pipe. So energy was lost through that process. We should expect a temperature change to account for both the adiabatic- (ideal gas law) and non-conservative work (energy loss to surroundings). Why do you believe the temperature would be constant on both sides of the valve? Have you instrumented the steam-temperature on both sides? Nimur (talk) 19:27, 28 January 2011 (UTC)

Thank you. I think then that both the volume and temperature will change too. At 184 Celsius Wolfram Alpha says the energy is the same[4]. I have no data of the temperature on both sides. But intuitively it seemed to me that the temperature could stay constant although the pressure dropped through the valve; pV/T could still be constant if the volume increased (density decreased). Wolfram Alpha also calculates the density.

In reality of course there will always be heat loss to the ambient (non-conservative work) but I guess you can assume it is zero. Wikifantast (talk) 21:37, 28 January 2011 (UTC)

please explain binary stars in simpler language than the article

I am trying to understand how binary star systems work with planets. 1. how close are the two binary stars? would it be like the sun and jupiter, or the sun and pluto, or the sun and alpha centori? 2. would the planets orbit both stars or just one? 3. in stars wars on luke's planet there are two suns in the sky of the same size not too far from each other. does this mean the stars are very close or one is a lot bigger than the other? would luke's planet be orbiting one or both of them? 4. if you are on a planet orbiting just one of the stars, and the other one is far away, does it look like another star in the sky? is there a way you could tell it is your binary sun? for example, i know you can tell other planets from stars because they sometimes move backwards in the sky. would the sun you are not orbiting do the same? Many thanks. —Preceding unsigned comment added by 74.14.13.241 (talk) 15:43, 28 January 2011 (UTC)

Let's simplify the problem first. 1) Any two objects orbit the Barycenter of the two objects. The barycenter is the center of mass of the two object system. For the earth-sun system, the barycenter is NOT the center of the sun. It is inside the sun, but off-center by a small amount. So it is technically incorrect to say that any one object orbits another; the two objects oribit around a point on a line between their individual centers of mass, which is located relative to their relative masses. The effect is really obvious when the objects are close enough in mass so that the barycenter lies outside of either object; this happens in the Pluto - Charon system. This works exactly the same regardless of the composition of the two objects; so two chunks of rock (like Pluto-Charon or Earth-Moon), a planet-star system (like Earth-Sun) or a binary star system. The way the two objects move is the same. 2) The major problem with adding a planet to the system is that you create an n-body problem, which is not stable; that is there is no way to predict the relative motion of all three bodies in the long term, even given their initial locations and velocities. --Jayron32 16:14, 28 January 2011 (UTC)

(e/c) Binary systems vary a lot in terms of the size of stars and the distance between them. This page discusses a stable system similar to that around Tatooine where stars are on average 23 AU apart, which is slightly more than the distance from Earth to Uranus.

The Wikipedia page on binary stars says it is possible for a planet to either orbit a single sun or to orbit both, depending on how close the stars and planet are. The example I mention above assumes the planet orbits only one star, at a distance of less than 3 AU (a bit more than the distance between the sun and Mars). Orbitting a single star would probably be a bit more hospitable for human life.

The distance from the planet to the farther star would be far less than between the sun and the next nearest star (our sun is 250,000 AU from the next-nearest star), so assuming the farther-away star was a similar size to the sun, it would look much brighter than any star but much smaller and dimmer than our sun. --Colapeninsula (talk) 16:23, 28 January 2011 (UTC)

Thank you and thank you. that helps to visulize it. Jayron do you mean that a planet like tattoone is not possible because it would keep moving a different distance from the suns and get too hot or cold for life? Because colapeninsula says it can be stable? That is interesting you would always be able to tell you are in a binary system because there are two things brighter than the stars. --74.14.13.241 —Preceding unsigned comment added by 74.14.13.241 (talk) 17:39, 28 January 2011 (UTC)

You can carefully construct 3-body problems like Tatooine so that they can be stable over fairly long periods; so yes, it is technically possible to do so. It would be rare, but of course not impossible, that such an arrangement could arise naturally. --Jayron32 17:47, 28 January 2011 (UTC)

Sorry, I just read colapeninsula's link that says the planet like tattoine would have billions of years before it moved enough to make it unhabatable. thanks again for the help. (talk) —Preceding undated comment added 17:43, 28 January 2011 (UTC).

Can we keep Tatooine from getting too close to a star by putting it in a Lagrangian point? I guess if you want to see both suns in the sky at the same time it would have to be points L4 or L5, unless it's possible to orbit around the L2 point (the article implies that it's possible). —Preceding unsigned comment added by 205.193.96.10 (talk) 21:03, 28 January 2011 (UTC)

The "orbits" around L1-L3 are not completely stable. They require small amounts of station keeping, which is easy for a spacecraft like the Solar and Heliospheric Observatory, but impossible for a planet. The other problem is the relative masses of the objects. L4 and L5 are only stable if the larger of the two objects (in this case, the two stars) is 25 times more massive than the smaller. That can happen if you have a binary system of a blue supergiant and a red dwarf, but you aren't going to get two sun-like stars with that kind of difference in mass. The other problem is that the object at the L4 or L5 point has to have a very small mass - small enough not to have any noticeable effect on the other two bodies (the stars). I'm not sure quite sure how small the body must be, but I suspect a planet would be much too large, especially since one of the stars is, because of the 25 ratio thing, required to be very small. --Tango (talk) 20:56, 29 January 2011 (UTC)

You might find HD 188753 interesting. Astronaut (talk) 16:23, 29 January 2011 (UTC)

ear piercing

When you pierce your ears is anything dying or is it just being pushe to a new location?Accdude92 (talk) 16:35, 28 January 2011 (UTC)

Surely at least some cells are ruptured by the act of piercing, though that article doesn't discuss piercing trauma very much at all. Comet Tuttle (talk) 17:46, 28 January 2011 (UTC)

Agree. In addition to the many types of skin and subcutaneous tissue cells that would be directly crushed during piercing, trauma to blood vessels will result in some bleeding, and the cells leaking from the laceration will die quickly. -- Scray (talk) 19:25, 28 January 2011 (UTC)

Hmmm. Why is it that ear piercings done with a piercing gun don't tend to bleed (or if they do, in such a tiny volume as to be unnoticeable)? This is my experience, as well as that of others I've discussed it with. --Kurt Shaped Box (talk) 19:29, 28 January 2011 (UTC)

I would guess that they are designed to apply pressure on both sides of the puncture, in a standardized way. The challenge has been to do so with an instrument that can be cleaned properly between victimscustomers. -- Scray (talk) 23:50, 28 January 2011 (UTC)

Personally, I'd recommend that anyone who fancies a piercing goes to an *experienced*, *competent* (shop around, ask questions - they're pros, they don't mind) piercer who uses a needle and an autoclave. I know it's a highly politicized subject (some piercers basically consider those guns to be the devil's spunk and seem genuinely furious that they exist) - but I'm simply stating this from my own personal experience with ear and eyebrow piercings (been considering a bridge piercing on and off for a couple of years) - and the healing thereof. Plus, you're not restricted to a stud for your first piece of metal. --Kurt Shaped Box (talk) 00:58, 29 January 2011 (UTC)

Also, is the a time when closing of the piercing is impossible?Accdude92 (talk) 17:26, 31 January 2011 (UTC)

Physics, conservation of linear momentum-collisions

2 bodies make elastic head-on collision on smooth horizontal table kept in car. Do u expect change in result, if the car is accelerated on a horizontal road because of the non-inertial character of the frame? Does the equation " Velocity of separation = velocity of approach" remains valid in accelerating car? Does the equation " Final momentum = initial momentum " remain valid in the accelerating car?

.....with proper reasons.

—Preceding unsigned comment added by 122.169.145.208 (talk) 17:20, 28 January 2011 (UTC)

Please do your own homework.

Welcome to the Wikipedia Reference Desk. Your question appears to be a homework question. I apologize if this is a misinterpretation, but it is our aim here not to do people's homework for them, but to merely aid them in doing it themselves. Letting someone else do your homework does not help you learn nearly as much as doing it yourself. Please attempt to solve the problem or answer the question yourself first. If you need help with a specific part of your homework, feel free to tell us where you are stuck and ask for help. If you need help grasping the concept of a problem, by all means let us know. DMacks (talk) 17:29, 28 January 2011 (UTC)

No this isn't a home work question! I saw this question while I was going through the book "Concepts of physics 1" by H.C.Verma. I know that in inertial frame, momentum and kinetic energy are very much conserved in this case but I couldn't decide myself whether momentum is conserved or not. I think its not conserved as pseudo force acts. But just I need clarification whether my thinking is correct or not. I am not confident about my answer, so I put this question here, but not for the sake of completing the homework! Hope you answer this ....

Yes, you are right, the pseudo-force acts, but the collision takes a very short amount of time to happen and since the change in momentum is given by dP = F dt, unless the pseudo-force is very strong (very high acceleration), the change in momentum is likely small enough that it can be considered negligible in which case all the usual rules of thumb for solving collision problems still apply. 71.101.41.73 (talk) 16:30, 30 January 2011 (UTC)

Aside the obvious answer

How can I find out if a sheet of glass is toughened (without actually breaking it)? --BozMo talk 17:31, 28 January 2011 (UTC)

A polarizing filter will help you see if there are strains in the glass. Here's a reference, The Identification of Toughened Glass using Polarized Light (1973). You can also use a web-search for comparative images: here's a sample Google query. Nimur (talk) 18:00, 28 January 2011 (UTC)

(EC) As per Toughened glass#Properties, the strain pattern resulting from tempering can be observed with polarized light or by using a pair of polarizing sun glasses. Red Act (talk) 18:05, 28 January 2011 (UTC)

In case anyone doesn't have access to the article I linked, here's a summary of the "methods" section: place the glass-under-test between two crossed polarizer filters, and illuminate from behind with white light. Rotate the polarizer filters. If you see an iridescent color-behavior that has a periodicity with each 90-degree rotation of the polarizer-filter, you have toughened glass; if you simply see a variation in light intensity, you have annealed glass. A few caveats exist, related to whether your glass has any fracture surfaces, that are described in detail in the paper I just linked and elsewhere on the web. Nimur (talk) 18:08, 28 January 2011 (UTC)

I'd consider the obvious answer to be to contact the manufacturer. I doubt anyone would sell toughened glass without advertising it as such. What are the circumstances you're trying to figure it out under? — DanielLC 03:03, 30 January 2011 (UTC)

Obviously he's asking out of doing research for a breaking and entering robbery job. In this case, calling the building's owner and ask whether he had toughened windows installed is not exactly an option... 62.166.201.27 (talk) 13:31, 31 January 2011 (UTC)

A hydrogen bomb in an undersea volcano= add new land?

If a fusion bomb was placed in an undersea volcano, would it induce an eruption so massive that this volcano will spew out enough lava to permanently break the sea level and become an island?

Surtsey happened naturally, and Japan and Taiwan is in an epic land crunch for real estate so this would be an instantaneous way to reclaim more real-estate from the sea, wouldn't it?

By the way, I think the results might be better if the bomb was made to explode upside-down. Instead of a mushroom cloud, how about a mushroom laccolith under the volcano's base? Therefore, how can a bomb be made to explode a mushroom cloud into the earth instead of up in the sky? --129.130.32.220 (talk) 20:07, 28 January 2011 (UTC)

I'll add that to the list of crazy ideas I've seen on those pages over the years. BTW, there is no such thing as an upside down explosion. The mushroom goes up because hot air rises. 71.101.41.73 (talk) 20:37, 28 January 2011 (UTC)

Yes, the idea of an upside-down explosion is just confused. The explosion of a nuclear blast is just a sphere of fire and blast. It rises because it is hot.

You could shape the blast, probably, to fire more energy in one direction than another, though. These sorts of schemes were considered in developing Project Orion. It strikes me as probably doable, though whether that would hep or not, I don't know.

As for the geology of it, I have no clue. There were worries in the 1980s that sufficiently large underground nuclear tests could induce seismic and possibly volcanic activity (see, e.g. Amchitka). But this didn't happen. But it wasn't meant to happen, either — it's not clear to me that you couldn't do it on purpose. It should be noted, though, that Japan is probably the last place on Earth that would ever embrace Plowshares-like projects. Their disinclination to mess with nukes goes pretty deep!

There is nothing on this topic in The constructive uses of nuclear explosives (1968), which is sort of a catch-all book of proposals for "fun" and "peaceful" things you could do with nukes. --Mr.98 (talk) 20:55, 28 January 2011 (UTC)

How could one prevent the bomb from melting or being disrupted by the heat while placing it "in a volcano?" Place it in a shell of Unobtanium? Edison (talk) 21:01, 28 January 2011 (UTC)

Heh, heh, Edison, Tungsten has a higher melting point than the temperature of lava, IIRC. We just have to get it thrown in there deep enough (by a tungsten drill, maybe?) and have it detonate by a timer or a switch. --70.179.181.251 (talk) 06:03, 29 January 2011 (UTC)

Presumably you wouldn't put it in the lava itself, but near it. E.g. to the right of the label "3" in this diagram, or something like that. But I am not a geologist. --Mr.98 (talk) 21:05, 28 January 2011 (UTC)

For perspective, consider reading about human-induced seismicity. Most induced seismic response is the result of many years of continuous changes in the overburden or fluid-pressure, due to extraction of solid or liquid material during mining, water-well extraction, or fossil-fuel extraction. Nimur (talk) 21:04, 28 January 2011 (UTC)

Even if it could work (I am pretty sure it couldn't, but lets play a game and pretend that it could), what would be the point? I am pretty sure that the lava would become impregnated with lots of highly radioactive fallout from the bomb you just set off; great, so you have new land but its so radioactive to be unlivable. What good is that? That of course ignore the point that even the most powerful thermonuclear devices pale in comparison to the power of geologic events. A single volcanic eruption or earthquake packs many times the wallop of an H-bomb. I'm pretty sure if you put the entire world's nuclear arsenal in one place and set it off all at once, it wouldn't even be as big as the 1980 eruption of Mount St. Helens, which while impressive was not uncommonly so, at least on a geologic scale. The main blast which caused the collapse of the north face of the mountain moved about 1/20th of a cubic mile of earth, an unimaginably large chunk of solid rock to be pulverized to dust. I just can't see a bomb doing that kind of work. --Jayron32 21:14, 28 January 2011 (UTC)

To be fair, nobody is saying that the bomb would have the force of a volcano, just that it could be used to trigger one. I'm not sure that's not impossible. The trick about energy release is that it matters how much is released in how small a volume. An earthquake releases a huge amount of energy but over long distances. The sun releases an unfathomable amount of energy but it does so over such a diffuse distance and time scale that we perceive it as a warm bath, not a searing flame. I think there are probably geological situations where a properly placed, sufficiently large thermonuclear detonation could act as a catalyst for a much larger volcanic eruption. It's not necessarily the case that fallout would be mixed into the magma itself — there might be clever ways to make the eruption contain the bomb blast (e.g. bury it even while it erupts upwards). But I don't know much about volcanos, to be sure. --Mr.98 (talk) 21:27, 28 January 2011 (UTC)

Actually Mount St. Helens released "only" about 24 Megatons of energy which is somewhat less than the largest hydrogen bomb ever detonated. The Krakatoa eruption, one of the largest eruptions in recorded history, was about 200 Megatons of energy. So, volcanoes are somewhat larger than but on the same order as hydrogen bombs. Of course the energy is released in very different ways, which does make a significant difference with respect to the impacts it has. Dragons flight (talk) 21:36, 28 January 2011 (UTC)

It's worth noting that Krakatoa's explosion left less land above the sea than before. And Mt St Helens got smaller when it exploded. Guaranteeing more land would be a challenge. HiLo48 (talk) 21:58, 28 January 2011 (UTC)

True to a point, but keep in mind that the goal would be to take the internal parts of the mountain and spread them out in order to create a structure with more surface area and less height. Still, Mt. St. Helens is a good example in many ways. Even if it had been surrounded by water, and somehow did end up with water above sea level, mixed ash is not really an ideal building material. And it strikes me that for all of the effort, the amount of land is still not going to be that useful by human standards. (And again, I'm wary about comparing nukes to volcanos in terms of explosive force, anyway, because the time scales are usually quite different, and the effects that correspond are quite different.) --Mr.98 (talk) 20:12, 29 January 2011 (UTC)

I'm not certain that the demand for new land in Japan is any higher than it is in New York. Though they have enormously high population densities in the biggest cities, due to most of the land being unusably steep (Japan#Geography), they also have a falling population size, and 6,852 little islands that already exist. The most significant reason for the high population of cities is that a large number of people want to live close together. Is Izu Ōshima so crowded that they need a second one? Land reclamation does say that 20% of Tokyo Bay has been reclaimed, but land that's contiguous with Tokyo must be worth a lot more than land which is offshore and radioactive. 81.131.22.166 (talk) 23:25, 28 January 2011 (UTC)

January 29

Sweet crude oil

I was in class and my prof mentioned that there is a type of crude oil called Sweet crude oil, and he said that workers would actually taste the oil. Isn't oil toxic? Wouldn't tasting it be detrimental to their health? ScienceApe (talk) 02:34, 29 January 2011 (UTC)

According to this document from the Oil Spill Academic Task Force of the State of Florida, "In the 19th century, oil workers would taste and smell small amount [sic] of oil to determine its quality." Clarityfiend (talk) 02:56, 29 January 2011 (UTC)

Many geologists are rather partial to having the occasional lick of anything that looks (or smells) interesting. DuncanHill (talk) 03:07, 29 January 2011 (UTC)

It looks like geologists like to put dirt in their mouth for several purposes, also to evaluate a sample's texture. See, for example, siltstone or, regarding oil, old formation evaluation tools to detect oil and gas by grounding the well cuttings between their teeth. They "tasted to see if crude oil was present", according to that article, unreferenced. Other sources seem to suggest it was for detecting texture, not taste. ---Sluzzelin talk 05:06, 29 January 2011 (UTC)

Tasting this oil is not detrimental to the health? ScienceApe (talk) 16:25, 29 January 2011 (UTC)

No one is claiming that! This (commercial) site lists some figures and hazards, toxicity in case of ingestion or skin contact included. The data are referenced. They don't directly answer your question, but it's pretty clear this isn't something you want to try at home, and certainly not repeatedly. Some of the long-term hazards from doing this repeatedly, such as carcinogenicity, probably couldn't have been detected soon enough to make a connection, at the time. (I wanted to point you to an article on the history of occupational health and safety, but, judging from the few articles that link to Bernardino Ramazzini, we have no such article, nor is it well-covered in any of the history sections). ---Sluzzelin talk 16:53, 29 January 2011 (UTC)

The level of benzene in crude oil before cracking is not very large, and cancer is definitely not guaranteed - though no level of exposure is truly acceptable. But bear in mind that petroleum was taken as a "medicine" in Western countries at a time when its use for fuel was obscure if not forgotten. Wnt (talk) 21:39, 29 January 2011 (UTC)

giving m₂=0 for newton formula

what happens for field when we give m₂=0 for newton gravity formula.(G) a. mohammadzade —Preceding unsigned comment added by 78.38.28.3 (talk) 11:26, 29 January 2011 (UTC)

See the article about Newton's law of universal gravitation which is expressed by the equation

$F=G{\frac {m_{1}m_{2}}{r^{2}}}\$

Any real physical object has mass, but if a hypothetical object had zero mass it would have no gravitational attraction to any other object. Cuddlyable3 (talk) 15:23, 29 January 2011 (UTC)

Well, there would at least be zero gravitational force acting on the zero mass object. But from F=ma (Newton's second law), calculating what acceleration results when an object with zero mass is acted upon by a zero force results in the indeterminate form a=0/0, so you can't conclude that the zero-mass object experiences no acceleration. What works better in this case is to combine Newton's two equations to give

$a_{2}=G{\frac {m_{1}}{r^{2}}}\$,

where a₂ is the acceleration of the object you're calculating the acceleration of, and m₁ is the mass of the other object. That combined equation avoids the indeterminate form when m₂=0, and helps lead toward the more appropriate understanding of gravity as involving a coordinate acceleration as is produced by a fictitious force, rather than being a real force, as per Einstein's equivalence principle. As per that combined equation, a theoretical zero-mass object will still experience the same acceleration due to gravity as an object with nonzero mass, even though there is no force acting on it. Red Act (talk) 18:06, 29 January 2011 (UTC)

Yes, except that equation arises by dividing by zero. The best we can say in the Newtonian theory is that following the ordinary acceleration of gravity is the limiting behavior as the mass of a body goes towards zero. However, if there were any force acting on the body except for gravity, that force would completely dominate its behavior when its mass gets small enough. It could be a force that is so tiny that its effect is not observable for anything but massless bodies, and so the Newtonian theory cannot actually predict that massless objects move with the acceleration you quote (that is, "predict" in the sense that it would automatically falsify the theory to find a massless object that did not move so).

And actually, the massless objects we know (that is, photons) do not experimentally behave in gravity fields like Newton says they ought to. They are deflected by more than the Newtonian limit, thanks to GR and space curvature. –Henning Makholm (talk) 01:30, 30 January 2011 (UTC)

Perhaps I should have given more emphasis to the requirement that the above equation would only apply in the case of there being absolutely no (nongravitational) forces acting on the object, either forces that are now known or that might be discovered in the future (or perhaps even some physical phenomenon discovered in the future that results in a proper acceleration but can't be expressed as a force). But I did end the post with the phrase "even though there is no force acting on it", so that limitation should have at least been rather clearly apparent at that point, even if it hadn't been obvious enough before then.

Newtonian gravity as an approximation to general relativity falls apart at high relative speeds, regardless of whether or not the object in question has a nonzero mass. And the approximation falls apart at high speed for even geometrical considerations alone, so the approximation's breakdown can't just be fixed by special relativistic corrections to the mass. So I was treating the question as pertaining to a hypothetical zero-mass object moving at low speed, since behavior at low speed is the only condition under which any discussion of Newtonian gravity has any validity at all. So the behavior of photons is irrelevant to the hypothetical situation that I was considering.

The equation above is the correct equation for the (coordinate) acceleration due to gravity of low speed objects in the absence of any (real) forces in the weak-field approximation as predicted by general relativity, and the equation above can be derived using general relativity without ever taking the object's mass into account (assuming the mass isn't large enough to itself cause nonnegligible curvature of spacetime). The geodesic followed by a object experiencing no real forces is completely governed by the geometry of the spacetime on which the object is traveling; the object's mass has nothing to do with it. So there isn't a division by zero involved if you derive the equation using general relativity.

Indeed, any other behavior for even an object of zero mass would be nonsensical for even geometrical considerations alone. In the absence of any real forces, the object must have a zero proper acceleration, because the local isotropy of space would prevent the object from having any way to even choose a direction in which to accelerate. And if the object has no proper acceleration, the only other "acceleration" the object can have is the coordinate "acceleration" of the object's local inertial frame with respect to the chosen noninertial coordinate system. And the coordinate "acceleration" is a purely mathematical device that has nothing to do with actual physics, so any physical properties of an object like whether or not it has a mass is irrelevant to the expression of the magnitude of the coordinate acceleration as expressed in the equation above.

As with any fictitious force, the apparent acceleration of objects under the "influence" of gravity is most appropriately viewed as more fundamentally being a coordinate acceleration, that only looks like a "force" if you artificially multiply that acceleration by an object's mass. That's the general relativistic perspective, and that's actually the entire reason why I pointed out in my earlier post how gravity can be described as being an acceleration, with any notion of a "gravitational force" being removed. I wasn't trying to fully explore the acceleration of a hypothetical low speed massless particle that might actually be discovered in the future. So bringing up tiny additional forces that might be discovered in the future and what-not is really tangential to my intended point. Red Act (talk) 08:06, 30 January 2011 (UTC)

Anal orgasm

Is it possible for woman to have orgasm from anal stimulation alone, and how is it distinct from vaginal orgasm? --78.150.235.125 (talk) 11:43, 29 January 2011 (UTC)

Orgasm#Anal_stimulation provides some referenced information for this and this Slate article may also be useful. SmartSE (talk) 12:34, 29 January 2011 (UTC)

Balloons

How much force upward does a balloon exert? I recently saw Up, and I know getting a house airborne would be impossible, but I am curious as to how much helium would be needed to lift a person or a basket. And how about hydrogen balloons? What is hydrogen and helium's lifting power per square inch? --T H F S W (T · C · E) 18:15, 29 January 2011 (UTC)

Per square inch it's zero ;-). The molecular weight of Hydrogen (H_{2) is 2 g/mol, the molecular weight of Helium (He) is 4 g/mol, and the average molecular weight of air is 80%*28+20%*32 (for Nitrogen and Oxygen, both diatomic gases), or just shy of 29g/mol. So one mol of Hydrogen can lift 27g, one mol of helium can lift 25g. One mol of gas under standard condition occupies 22.4l, so the lifting power of either gas is about 1g/l or 1 kg/m³. Of course, that is the gross lift - for the net lifting capacity, you need to subtract the weight of the balloon. If you need more exact numbers, apply a calculator ;-) --Stephan Schulz (talk) 18:27, 29 January 2011 (UTC)}

There was the interesting case of Lawnchair Larry, who dared in 1982 to try this experiement "at home". He attached 45 helium-filled weather balloons to a lawn chair in his back yard and flew to an altitude of over 15,000 ft! (Asked why he did it, he replied, "[Because] a man can't just sit around.";) WikiDao ☯ 18:28, 29 January 2011 (UTC)

OK, thanks, I'll start collecting weather balloons! Joke - for now.--T H F S W (T · C · E) 18:48, 29 January 2011 (UTC)

N.B. his "honorable mention" at the Darwin Awards...;) WikiDao ☯ 19:36, 29 January 2011 (UTC)

Anyone know the area of a normal party balloon? And @Stephen, yeah, I meant a cubic inch. Heh heh. --T H F S W (T · C · E) 19:58, 29 January 2011 (UTC)

You're a quick study, right? ;-). Do you mean the surface area or the projection onto the ground? Or do you actually mean the volume? A 30 cm ballon has a volume of around 14 l. It weights maybe 1.5 g, so it can lift around 12 g. --Stephan Schulz (talk) 21:16, 29 January 2011 (UTC)

In real units. 1000 cubic foot of hydrogen at STP will lift 74 lb. So a cubic foot balloon is err.. I think 1.184 ounces of lift. Helium has a lift of 72 lb per 1000 cu ft.--Aspro (talk) 21:29, 29 January 2011 (UTC)

Fully saturated moist air weighs only 5/8 of dry air and is very much cheaper than H or He. You can create some by burning (say) propane or butane gas in a large bag. That will also heat it and increase the lift still further. Thinks.... If one were to leave said bag open at the bottom you could keep it hot by continuously burning more gas. Hey! I wonder if Microsoft has patented this idea yet? --Aspro (talk) 21:47, 29 January 2011 (UTC)

While water vapor (gaseous H₂O) is about 5/8 the mass of an equivalent volume of dry air at the same temperature and pressure, it's highly incorrect to say that moist air is 5/8 that of dry air. Humidity notes that at 30°C, saturated air contains 30 g per cubic meter of water, which equates to at most 18 g of lift per cubic meter. This compares to an air density of 1.164 kg/m³, so humid air would be at most 1.5% lighter than dry air. This compares to the ca. 80g/m³ lift you get by heating 15°C air to 35°C (cf. Density of air). It's true that if you had an equivalent volume of water vapor at the same temperature and pressure, you'd get 3/8ths lift from it, but at temperatures below 100°C, that's not possible, as all the water would condense, and you'd have a deflated container [5], or a partial vacuum. -- 174.21.236.191 (talk) 00:25, 30 January 2011 (UTC)

Quite right -the lift is pitiful. Maybe instead, a sealed balloon of pure water vapour, fabricated from aluminium foil backed bubble-wrap, with argon filled bubbles to reduce conductive heat loss. Then a small radioisotope heater unit to maintain the vapour at ≥100 deg C temperature. --Aspro (talk) 18:32, 30 January 2011 (UTC)

Of course, the weight of the balloon itself also has to be lifted. My intuition says that a single large balloon should require less gas to lift the same weight than a large number of small ones, although this is not 100% obvious, because the large balloon might need to be thicker. Anyway, balloonists normally do use a single large balloon, so it makes sense that that's best. (The great airships like the Hindenburg did use separate gasbags within an outer cover, but I think that was mainly in order to contain the effects of any damage.) --Anonymous, 00:05 UTC, January 30, 2011.

While not an WP:RS, this forum thread reckons 60lbs per square foot of living space, or 120lb per square foot of footprint for a house is the approx weight. Exxolon (talk) 16:55, 30 January 2011 (UTC)

Buckminster Fuller went as far as to propose airborne towns.--Aspro (talk) 18:21, 30 January 2011 (UTC)

Graphite

In graphite, are the layers stacked so that the carbon atoms in one layer are directly on top of the carbon atoms in the lower layer, or are they over the centers of the other layer's hexagonal holes? --75.15.161.185 (talk) 19:39, 29 January 2011 (UTC)

The latter. See: graphite. Dragons flight (talk) 19:41, 29 January 2011 (UTC)

Converting ohm to siemens

I'm doing a science project on the electrical conductivity of different materials. I have an ohmmeter and know how to convert ohms to siemens. The problem is, I'm testing piece of rubber and the reading just shows up as 1 on the 2M setting. How would I convert this value? Writing down 1 [S/m] doesn't seem correct. —Preceding unsigned comment added by 68.230.183.227 (talk) 19:49, 29 January 2011 (UTC)

A multimeter reading of "1" typically means the value is unmeasurable because it is beyond the range of that meter. Since you put the multimeter on 2 MΩ, you know that the resistance of the rubber is greater than that (R > 2 MΩ), so the conductance is less than (1÷(2 MΩ) = 500 nS), so G < 500 nS. --Link ^(t•c•m) 21:04, 29 January 2011 (UTC)

I talked with my dad and he basically said the same thing. Thank you so much though. —Preceding unsigned comment added by 68.230.183.227 (talk) 21:51, 29 January 2011 (UTC)

Central American Bat Identification

8.70780°N 83.49300°W / 8.70780; -83.49300

I recently photographed this individual roosting on a tree trunk, approx 8-10feet above ground level. Accompanied by one other individual, roosting a few feet above. Osa Peninsula, Costa Rica. Hopefully those lines of white pale fur are destinctive, thanks in advance Benjamint 22:36, 29 January 2011 (UTC)

Looks very like the bats shown in this query, which have been identified by a respondant as either Lesser Sac-winged bats (Saccopteryx leptura) or Greater Sac-winged bats (Saccopteryx bilineata). 87.81.230.195 (talk) 02:45, 30 January 2011 (UTC)

January 30

My Honda Accord will be 10 years old this year. Why no rust?

Some junked antique cars are coated with rust, and I've read that they've rusted rather quick.

Yet my 2001-model has almost 130,000 miles so how does it remain rust-free anyhow? --70.179.181.251 (talk) 00:12, 30 January 2011 (UTC)

There are lots of factors that cause different amounts of rusting. If you maintained your car very well, and didn't drive it on a lot of salted roads, I would not expect it to rust. All of our cars have been far older than that when we got rid of them, and other than a tiny spot, I can't remember any rust on any of them. Of course, it could be rusting in places that you don't see, but even that's not a guarantee. Basically: it depends on a lot of different things. I cannot tell you why your car specifically is not rusting, but I can surmise why a car might not rust after ten years. Falconus^{p t c} 03:14, 30 January 2011 (UTC)

At least in Germany, it's now standard for most new cars to have a fully zinc galvanized body, which makes rust a very rare occurrence. Toyota started the wide-spread use of galvanized steel in Europe in 1992, and seems to use it more or less universally since 2000. Car-makers now have the technology to nearly completely eliminate rust as a problem, although not all use it to the same degree (arguably, there is no reason for outstanding longevity if cars are retired for obsolescence reasons after 10 years anyways). --Stephan Schulz (talk) 09:19, 30 January 2011 (UTC)

Sorry, my mind misread Honda for Toyota. I don't know when exactly which Honda models started using galvanized steel, but from what I could find online it should be in a similar time frame.--Stephan Schulz (talk) 12:05, 30 January 2011 (UTC)

As above - modern cars rustproofing is a lot better than before. If you're driving in a dry climate without lots of rain, snow or ice the car's bodyshell will not degrade very much. Exxolon (talk) 16:38, 30 January 2011 (UTC)

Short answer: It's a Honda. :P Roger (talk) 17:38, 30 January 2011 (UTC)

How do I customize GPS navigation voices?

I think the voices that vehicles give through their embedded GPS navigation systems should reflect their ages and nationalities. At least the voices of the vehicles I plan to drive, anyway. Moreover, I'd also like some kind of subroutine that will "age"/deepen the voice of the navigation system as the vehicle ages.

For example, if I buy a used 2005 Volvo XC90 in 2013, how do I get the navigation program to voice out the directions sounding like a Swedish boy?

I think if I drive a Hyundai, the GPS voice should have a Korean accent. If I drive a Fiat, an Italian accent, etc. Moreover, their voices should reflect the date of the car's manufacture. (I won't have to worry too much about how silly they'd sound because I don't plan to buy vehicles newer than 5 years old anyway. It saves a bucketload of $$$ buying used.) --70.179.181.251 (talk) 00:12, 30 January 2011 (UTC)

I think most commercial GPS systems do not synthesize their voice phonemically; they simply play back a series of sampled words. So you would need to (1) pay a voice actor with your desired voice and accent to record a complete vocabulary for the navigation system, (2) rent a voice recording studio for him/her to do it in, (3) pay the manufacturer of the GPS system to help you get the new vocabulary into the box's firmware, as if it was a new language localization. The latter is not an off-the-shelf service; you could easily be looking at $10,000 or more here, and expect to pay in advance. Repeat everything whenever you think the voice ought to change due to the car aging.

Oh, and the GPS manufacturer may not even want to touch this unless you promise that they won't get sued if you let somebody borrow your car and they misunderstand the GPS directions and end up in a river and drown, and they may want you to back this promise with a bank guarantee or a fully paid up indemnity insurance policy, which isn't cheap either, and then you'll also want to pay a lawyer to go over the promise before you sign it, to make sure you're not accidentally signing away your firstborn.

It may be cheaper if you start out with an open-source navigation system running on off-the-shelf laptop or smartphone hardware, though in that case you'd need to hire a freelancer or consultant to do the heavy lifting (you can legally do it yourself, but if you had the skills to do so you wouldn't have to ask here), and that would still set you back at least several thousand dollars in addition to the actor's fee, and you'd risk getting a less stable and feature-rich system than a commercial GPS solution. –Henning Makholm (talk) 02:29, 30 January 2011 (UTC)

Henning is right about commercial sat nav systems, but there is an alternative: the free navigation app from Google, available on Android smartphones. It uses the Google text-to-speech (TTS) engine, which is customisable in principle since it's open source. How you would do it in practice, though, I have no idea. Also, it's currently only available in the USA and the UK. The British one sounds as you would expect the Bride of Frankenstein to sound. It tries to synthesise place names phonetically, often getting them wrong, but you can usually work out what it's trying to say. --Heron (talk)

Standalone GPS systems are easy to customise as long as you have voice samples in a compatible format and the master list that tells the system there's a voice there and which sample to play for each situation. If you could access the memory of an integrated system it should be possible to do the same. Exxolon (talk) 16:36, 30 January 2011 (UTC)

Vocal synthesizers, not voice actors.

Problem is, I'm not looking for actors' voice samples. I'm looking for vocal synthesis Aren't there vocal synthesizing programs that enable me to change any vocal recording to that of a desired age? Why can't I just convert the existing recordings to those instead?

(And if I do get a vocal synthesizer, how do I also change the accent to that of a desired country's?) --70.179.181.251 (talk) 17:08, 30 January 2011 (UTC)

This might be more of a question for the computer desk. Most SatNav vendors have a wide range of voices that can be downloaded from their website, some free, some purchased. The files are easy to install, simply copied to the SatNav flash drive. However, the data is not in a publicly published standard so it will not usually be possible to create your own without collaboration with the manufacturer. As Heron said, many devices use sampled voices rather than synthesis so there would be no way of programming in a variant synthesiser, there is just no facility. The best you could do would be to access the analogue audio going to the speaker (which will probably involve taking your satnav apart) and feeding it through a voice disguiser, suitably adjusted for the effect you are looking for. SpinningSpark 19:38, 30 January 2011 (UTC)

GPS satnav system are just not set up for this. If you connect one to your PC and browse it, you'll find a folder for the voices. Each subfolder contains all the samples needed to construct all the sentences ever needed and a file telling the satnav which sample to play when it needs to make that particular part of a sentence. Looking back at your original post it looks like you want the GPS to reflect the cars "personality" for want of a better term - an integrated SatNav with a voice that's appropiate for the car make, model and age - no manufacturer will bother doing this - it's a lot of expensive work for a demand that's just not there. It would be just about possible to do this manually assuming you could find or record samples in the relevant accent, timbre, elocution etc and access the satnav memory - you could then manually set the voice to match the car. However you'd have to do this manually for each make/model you wanted to do - there's no way to do it automatically. You'd also have to periodically replace the samples manually if you wanted to reflect the age of the car - there's no way for the satnav to switch samples based on the age of the car. This really isn't going anywhere. Exxolon (talk) 01:04, 31 January 2011 (UTC)

What's at the edge of a piece of diamond or graphite?

Or other lattice compounds, for that matter. Unlike molecular compounds, the atoms on the edge would have unpaired electrons, so what do they do? Do they just bond with random hydrogen or oxygen atoms from the air? --75.15.161.185 (talk) 03:17, 30 January 2011 (UTC)

Yes --Plasmic Physics (talk) 03:33, 30 January 2011 (UTC)

See in particular material properties of diamond, which contains some discussion of which terminators they typically end up with. Apparently we have nothing similar for graphite (I wonder whether it would be an acute problem there -- because the orbitals are hybridized throughout the graphite layer, the burden of lacking an electron could be shared among many more atoms than in a small radical. On the other hand, it appears that a phenyl anion is not considered aromatic, so perhaps the edge atoms are not allowed to just borrow their missing electron). –Henning Makholm (talk) 04:23, 30 January 2011 (UTC)

What if it's formed in a vacuum by vapor deposition? --75.15.161.185 (talk) 13:24, 30 January 2011 (UTC)

Then it would appear that the graphite has no choice but to grow with unpaired electrons at the edges, wouldn't it? As far as I can search, the most abundant molecules in carbon vapor are things like :C=C: and :C=C=C: which have more unpaired electrons than they have atoms, so it would still be a net win for them to join a growing graphite sheet, even if the sheet does not terminate nicely. –Henning Makholm (talk) 14:44, 30 January 2011 (UTC)

fruit

If a fruit falls from a tree and no animal eats it, will the fruit aid in the seed in growing? —Preceding unsigned comment added by 92.3.157.72 (talk) 03:35, 30 January 2011 (UTC)

If the fruit is not eaten by an animal, it's likely to rot before the growth season starts anyway. And even if it miraculously avoids rotting, the seedling would have to absorb the sugars from the fruit through its root, and it's far from clear that it would be up to that task -- the root epidermis would have to express specialized membrane transport proteins for this, and likely has no evolutionary reason to think trying that might be a good idea. It's even possible that the osmotic pressure of the sugar would make it difficult for the seedling to absorb enough water to grow. –Henning Makholm (talk) 04:55, 30 January 2011 (UTC)

Wait, surely the fruit rotting is a good thing, as now the seeds are sitting in a small amount of compost? I don't think any theory of fruits and seeds proposes that the seeds make use of the unrotted fruit. I'm sure many plants rely on animals eating the fruit to disperse the seeds, but that seems far from the only purpose of fruit in all non-cultivated plants: there are fruits with protective systems to prevent them being eaten, for example. And some apples, for instance, do rot where they sit without being eaten, and then the apple seed grows in the apple-enriched earth: there doesn't need to be only one benefit to something. 86.164.58.119 (talk) 10:33, 30 January 2011 (UTC)

This is a common misconception; the main purpose of fruits is not to provision seeds. Generally speaking, the purpose fruit serves a plant is to disperse the seeds via animals. This is a classic mutualistic interaction, because it benefits both the plant and the animal. SemanticMantis (talk) 05:33, 30 January 2011 (UTC)

And where fruits contain poison normally the poison is only present until the fruit is ripe or it is only in the nut or it is poisonous to some mammals rather than birds for instance so the seed gets widely dispersed. Dmcq (talk) 11:01, 30 January 2011 (UTC)

What is the point of the rough almost armoured coat on a lychee? This coat or rind seems "designed" to prevent animals from eating it. Thanks 92.29.125.152 (talk) 14:09, 30 January 2011 (UTC)

Plants often 'target' a certain animal to disperse their fruit. In the case of the lychee, the shell may keep out insects or mice, but allow a bird to eat the fruit and carry it farther. SemanticMantis (talk) 14:17, 30 January 2011 (UTC)

Dmcq mentioned something similar (before the OP's question) and there are also chillis and durians as other examples of targeting the right dispersal agent/animal. Nil Einne (talk) 15:14, 30 January 2011 (UTC)

the temperature of crab nebula

i had read any subject in scientific american that the temperature of nebula of such crab is 10⁴ degrees centigrade . i want to know if that is so or i have forgotten. --78.38.28.3 (talk) 06:22, 30 January 2011 (UTC)a.mohammadzade

I've fixed the formatting so that the question is more easily readable. Mitch Ames (talk) 06:27, 30 January 2011 (UTC)

According to our Crab Nebula article:

In visible light, the Crab Nebula consists of a broadly oval-shaped mass of filaments ... The filaments' temperatures are typically between 11,000 and 18,000 K ...

10⁴ degrees Centigrade is about 10,000 Kelvin, so the visible part of the nebula is about 10⁴ °C. Mitch Ames (talk) 06:35, 30 January 2011 (UTC)

ok thanks alot .then for recent observation the crab nebula is accelerating particles . is there any nucleic reaction in such clouds?--A.mohammadzade (talk) 06:57, 30 January 2011 (UTC) — Preceding unsigned comment added by A.mohammadzade (talk • contribs) 06:49, 30 January 2011 (UTC)</spanTemplate:Unsigned -->

Note that "temperature" is fairly misleading in this setting. The crab nebula is a high-quality vaccum by our standards. So while the average energy of molecules in the nebula is high (that defines "temperature"), the energy density is extremely low. You could sit inside the nebula in a space suit forever, and still loose more energy from your thermal radiation at ~300K than you would take in from the rare interaction with one of the "hot" particles. The nebula is a recent supernova remnant. Supernovae often generate a lot of (in absolute terms) very heavy radioactive elements. So I'm fairly certain that there still is a measurable amount of nuclear fission going on in the nebula. I don't think there is an appreciable amount of fusion, though. --Stephan Schulz (talk) 09:27, 30 January 2011 (UTC)

Tidal Locking Formula

Dear Wikipedia

I emailed Dr. Burns at Cornell University (e-mail address removed). He said that he had a quick look for formula 2 [which has 10 to the 10 years on the end of it] and it is not in the book cited on the wiki page. http://en.wikipedia.org/wiki/Tidal_locking#Timescale

Would Dr. Peale know? (e-mail address removed)

I have removed e-mail addresses in the above, as per the policy at the top of this page. Red Act (talk) 09:35, 30 January 2011 (UTC)

The formula you seem to be referring to is not cited to a book at all. Which book is it missing from? Do you contend that the formula is wrong? –Henning Makholm (talk) 11:34, 30 January 2011 (UTC)

Can anyone provide clear, simple answers to these Mandelbrot Set questions needed

1. I’ve heard that the Set is connected I gather this means it has no islands. Does that mean you could go from any point on it to any other point without lifting your pencil? But could you do it without crossing any other line?

2. I see great electric lightning type tendrils coming from the main body. Are these lines or do they have have some kind of width? With the tendrils, I have seen images where they extend many times further than the diameter of the main body. How far is the longest one/

3. Also on tendrils coming from the main body, I notice that they seem to be more violent and extensive at the poles of the three main bodies, and that more sub MD sets are clustered there. Is this true, or do I just imagine that there are areas more conducive for such activity?

4. On the tendrils, sometimes a sub-MD appears. How does this happen? Why does a tendril go on normally and then suddenly explode into a full MD. Is there some value in the code which, when it is encountered, explodes it into a whole new set?

5. It says in the article that the MD is self-similar, but unlike Koch’s snowflake and others, you can’t make a priori predictions as to what will be happening down levels deeper. I’m told that this means that the volume enclosed by the set can’t be calculated except within limits. Is this true?

6.There seems to be no shape or line in this set which looks like anything in Nature, expect superficially. There are no circles or lines. I noticed in images that the lance of the MD seems to have something like a straight line, or gradually curved one, and that the fractal activity there appears less complex. Are there areas of the Set where complexity is reduced compared to other areas? Can this complexity scale be measured? Myles325a (talk) 11:57, 30 January 2011 (UTC)

1: Yes, when we say it is connected, it means you could (in principle) draw a line from one point in the set to any other point in the set, without leaving the set or lifting your pencil. SemanticMantis (talk) 14:55, 30 January 2011 (UTC)

5: Basically, yes. Note that the Mandelbrot set is not self-similar in the same strong sense that the Koch curve is. There is at the moment no exact area known for the Mandelbrot set, but we can (in principle) calculate it as precisely as we choose. Related is the idea of the Coastline problem, which is often paraphrased as "The length you get when measuring a coastline depends on the length of your measuring stick". SemanticMantis (talk) 16:18, 30 January 2011 (UTC)

6: It is interesting you say no shapes that look like 'nature', and then mention circles and lines. It is true there are no perfect circles or lines in the (boundary of) the Mandelbrot set, but there are also very few circles or lines in nature (i.e. the physical world). In fact, many sources mention that things like clouds, mountains, or islands are better described by fractal geometry than Euclidean. SemanticMantis (talk) 14:14, 30 January 2011 (UTC)

4: There is no why. The set is what it is. There is no secret input value hidden in the code. In fact, the code is incredibly simple. 71.101.41.73 (talk) 16:34, 30 January 2011 (UTC)

Delivery

during the delivery of a child the child does not get harrased or injured while passing through the pelvic girdle? — Preceding unsigned comment added by Joshuki (talk • contribs) 12:15, 30 January 2011 (UTC)

See Birth trauma (physical) for some types of physical injury that the child can sustain during delivery. As for harassment, I think the risk is low. Staecker (talk) 13:56, 30 January 2011 (UTC)

What do nebulae look like in visible light?

What would a nebula look like if you were inside it on a spaceship? --75.15.161.185 (talk) 13:26, 30 January 2011 (UTC)

It depends on the nebula. For interstellar clouds, in most cases, it would be invisible. Matter is very diffuse in these nebulae. The Great Andromeda Nebula would presumably look a lot like the Milky Way from the inside. --Stephan Schulz (talk) 13:35, 30 January 2011 (UTC)

Would it ever look like the dense, glowing fog/clouds used in TV shows like Star Trek? --75.15.161.185 (talk) 15:11, 30 January 2011 (UTC)

Only if you use a positronic scan with reversed polarity. --Stephan Schulz (talk) 15:43, 30 January 2011 (UTC)

Make it so, Mr. Broccoli. --Anonymous, 03:52, January 31, 2011.

cell sonicator

is there any other cell distruption method, other than sonicator ? —Preceding unsigned comment added by 115.242.140.78 (talk) 15:24, 30 January 2011 (UTC)

Yes, there are a number of different options. The optimal method will depend a lot on your ultimate goal and what you want to do with your cell lysate. As it turns out, we have a very interesting article entitled cell disruption that would be a good place to start. --- Medical geneticist (talk) 15:38, 30 January 2011 (UTC)

A scientific test to determine if Blacks are dumber than Whites

If we wanted to design an thorough scientific experiment (and ignoring all ethical considerations) to determine if Blacks are dumber than Whites for purely GENETIC reasons alone, how would we design the experiment? I came up with the following experiment, please tell me if this is a good experiment (ignoring ethical considerations) with proper controls.

The sample size of each group is unclear to me at this point. Suggestions on minimum sample size would be helpful.

1 group of newborn Blacks with at least 90% of their DNA can be traced to Sub Saharan Africa. Divided into two subgroups, one half is intact, the other half has their skin bleached. Half of the intact newborns, and half of the bleached newborns are placed into adoptive parents that live in upper class society. The race of all the parents should be white. The other half of intact and bleached newborns should be placed into adoptive parents that live in lower class society in the inner city. The race of all the parents should be black.

1 group of newborn Whites with at least 90% of their DNA can be traced to Europe. Divided into two subgroups, one half is intact, the other half has their skin darkened (not sure how this can be accomplished, but lets assume that it can be). Half of the intact newborns, and half of the darkened newborns are placed into adoptive parents that live in upper class society in the suburbs. The race of all the parents should be white. The other half of intact and darkened newborns should be placed into adoptive parents that live in lower class society in the inner city. The race of all the parents should be black.

As they all grow up, they should be given IQ tests at different time intervals, and their academic performance should be measured. This experiment would last for several decades.

The bleached and darkened newborns are there as controls. If the bleached Black newborns performed as well as intact Whites in their respective socio-economic levels, it would prove that intelligence is determined from purely external factors, and not determined by genetics.

How is my experiment? Suggestions? Are there any unnecessary groups? What should be changed? Etc ScienceApe (talk) 16:53, 30 January 2011 (UTC)

Well (gritting my teeth and trying to ignore the offensive wording of parts of the question), to have a properly controlled experiment, the participants need to be blind to the status of the subjects. You can't make a person from sub-Saharan Africa look caucasian, or vice versa, merely by bleaching or darkening skin, so I don't see how that would be possible. Going beyond this, the fact that sub-Saharan Africa comprises more human genetic variability than the entire rest of the world put together makes experiments of this sort a bit silly, in my opinion. It's like asking whether mammals are smarter than dogs. Looie496 (talk) 17:58, 30 January 2011 (UTC)

(edit conflict) Here at the RD/S we routinely rebuff, for good reason, "scientific" questions built on speculative assumptions ("what if you traveled at 1.5 times c for 5 years in an elliptical path, returning to your starting point..."). This one is in that category for multiple reasons, aside from the patently offensive premise and wording on which it's built (the hypothesis, as stated, is clearly one-sided). We have insufficient scientific basis for (i) how representative these study groups would be of the overall population on which you build the premise, (ii) that the groups could be sufficiently blinded to the study assignments, (iii) that there are "bleaching"/"darkening" procedures that would eliminate racial characteristics giving rise to bias, (iv) that adoption itself does not fundamentally alter linkages among key variables - thus making the adoptive placements an invalid surrogate for race reversal, (v) IQ tests and current measures of "academic performance" are valid measures of intelligence. More importantly, we do not have a basis for believing that these children would not be harmed in the course of this research, so it's unethical as proposed. Bottom line, this proposal is offensive, unethical, and unscientific. -- Scray (talk) 18:06, 30 January 2011 (UTC)

I've put a hat on this, a better idea would be to propose something without the given variables, but the same idea. Tofutwitch11 ^(TALK) 18:11, 30 January 2011 (UTC)

What are "blacks"? What are "whites"? We need a much better definition of terminology before we can proceed. Bus stop (talk) 18:11, 30 January 2011 (UTC)

I have hatted it. Tofutwitch11 ^(TALK) 18:12, 30 January 2011 (UTC)

In the world of science, is there anything that is as taboo as this subject? 88.112.59.31 (talk) 18:45, 30 January 2011 (UTC)

I don't think the word "taboo" is perfectly applicable here. The fundamental problem, IMHO, is that "race" is a social construct, and "intelligence" as broadly defined is impossible to measure (currently). So, science is a very poor domain in which to address the intersection of race and intelligence, and the attempts to do so end up embroiled in meta-discussion. -- Scray (talk) 18:55, 30 January 2011 (UTC)

It's not "taboo". It requires definition. What are we trying to find out? "Blacks" and "whites" are meaningless terms. "Intelligence"—what is "intelligence"? Bus stop (talk) 18:56, 30 January 2011 (UTC)

Interracial cookie. Bus stop (talk) 19:00, 30 January 2011 (UTC)

See Race and intelligence. Further discussion in this realm is unlikely to be fruitful. --Jayron32 19:14, 30 January 2011 (UTC)

I'm unclear as to why this has been hatted, except for the idea that any discussion of the topic is verboten. The OP has clearly indicated that the experiment is fanciful — he is just asking whether it would actually be useful to ferreting out the answers, or if there are methodological problems. I think there are methodological problems (the entire thing is reliant on a 19th-century vision of both race and the nature/nurture debate). But I don't see why we can't talk about that. I suppose it could be viewed as troll food, but I'm wary about preemptively labeling topics that just because they are controversial. --Mr.98 (talk) 20:39, 30 January 2011 (UTC)

But the OP labelled it in the section title with the hypothesis of Blacks are dumber than Whites. That's not a good start. I'd like to see the objective reasoning behind that. And, as Looie496 said, we need this to be a double blind experiment. I would need to hear a lot more about how that was going to happen. HiLo48 (talk) 21:00, 30 January 2011 (UTC)

It's a HYPOTHESIS. A hypothesis isn't meant to be true; it's meant to be tested, and possibly refuted, by the experiment. If a hypothesis is known to be true, it wouldn't be a hypothesis, and there would be no point in performing the experiment. --99.237.234.245 (talk) 21:04, 30 January 2011 (UTC)

Have fun! --Jayron32 20:51, 30 January 2011 (UTC)

Yes, but he could have titled the question as "A scientific test to determine if Whites are dumber than Blacks" as well, but he didn't. Why not? Clearly there is some underlining bigotry here. I agree that instead of hatting it we should discuss it openly and show why such a study (even as a hypothetical study) is unlikely to prove anything useful. Dauto (talk) 21:10, 30 January 2011 (UTC)

What about if we reformulate the question into correlation between IQ and skin color? The second can be measured, and if someone manages to measure the first, we can plot the data... Quest09 (talk) 21:16, 30 January 2011 (UTC)

Take young children from their parents and have them raised by adoptive parents? It has been done before, many times, with tragic consequences for which the Australian parliament has apologised. See Stolen Generations#Australian federal parliament apology. Dolphin (t) 21:42, 30 January 2011 (UTC)

Just a reminder - Jayron32 provided a useful link to our article Race and intelligence, which provides a thoughtful treatment of many of the issues. That would be a great starting point, if this discussion is to be fruitful at all. I'm sure that article could be improved, as well, if someone has lots of energy. -- Scray (talk) 21:46, 30 January 2011 (UTC)

The answer is that no valid scientific experiments can be done on this, because neither race nor intelligence have useful operational definitions. You could perhaps perform a study to compare the performance on standardized tests of people with various amounts of certain skin pigments, and see if there is some correlation. However, this scientific dead-end was abandoned at the beginning of the 20th century, and I don't see why one would want to waste their time with it. I'm not sure why one would suspect that skin pigments would affect test performance. As people have suggested, you might want to take a look at Race and intelligence, where you can learn more about experiments that have been done, as well as allof the bad science that's been done by people trying to prove that "Blacks are dumber than whites". -- Mesoderm (talk) 21:56, 30 January 2011 (UTC)

BTW, A lot of the responses above have been predicated on the fact that race can not be found in DNA, or that race is a social construct. This is not true, see here: http://blogs.discovermagazine.com/gnxp/2010/12/to-classify-humanity-is-not-that-hard/ Ariel. (talk) 22:53, 30 January 2011 (UTC)

It is certainly possible to classify humans based on genetics, however those classifications would not correspond with the usual concept of "race". The article you link to mentioned this: "The various phenotypically “black” peoples of the world, Africans, Melanesians, and some South Asians, do not cluster together. Rather, all non-Africans are separated from Africans by the largest component of variance within the data set." --Tango (talk) 23:17, 30 January 2011 (UTC)

Why are you only using upper class white parents and poor black parents? If you want to eliminate the effect of wealth from your study (which you need to do), you need to have white and black parents with a wide range of wealths. --Tango (talk) 23:17, 30 January 2011 (UTC)

Yikes, I didn't think I would be accused of being a racist. If it makes any difference to anyone, I have dark skin myself and I was sick of racist bigots claiming that black people are dumber than whites. They kept saying how there isn't a black nation on the planet that is modern, that the bell curve for black's performance on IQ tests is worse, that Africa isn't as technologically advanced as white nations because they are inferior, etc, etc. Just awful things, and I was so sick of it, I wanted to at least conceive of a real scientific test that would at least provide some evidence that what they are saying simply is not true. But I want it to be as accurate as possible with proper controlls, so please try to indulge me for the sake of argument. How would I do this if we had no ethical considerations stopping us? ScienceApe (talk) 00:13, 31 January 2011 (UTC)

I want to expand on someone's concern above about IQ tests. They do not measure smartness and dumbness. They measure the ability to score well on IQ tests. HiLo48 (talk) 00:34, 31 January 2011 (UTC)

How to remove glue?

I was building a Heller Ariane 5 model rocket when, due to defective assembly instructions, I glued together the two halves of the fuel tank before I was supposed to. Now I need to unglue them without risking damage to the structure, so ideally I'd like to remove the glue without applying force on the model. Is it OK to submerge the model in hot water and wait for the glue to decompose?

I am using standard tube glue. Thanks everyone. Leptictidium (mt) 18:01, 30 January 2011 (UTC)

"standard tube glue" is not very specific, but in context I assume you're referring to the glue generally used for plastic models, i.e. butanone-based adhesive. There are de-bonding agents sold in hobby stores for this purpose; I'm not confident that hot water will achieve the results you want because butanone works by dissolving a bit of the polystyrene and allowing the two parts to fuse, but if it won't damage your model then you could try it. -- Scray (talk) 18:33, 30 January 2011 (UTC)

I am not sure what the best way to proceed would be. One thing that comes to mind is to allow the two glued halves to remain glued together, and then to cut them apart with a tool like a Dremel rotary tool. Of course this is a very expensive approach, so you will probably want to consider other alternatives. But I just thought I'd mention the possibility of this. I really don't know much about the exact situation. But I know sometimes glues can be difficult to reverse once they have set. Bus stop (talk) 18:40, 30 January 2011 (UTC)

You can possibly try to carefully pry them apart with an old style plain razor blade. Be careful with the remaining 9 fingers! --Stephan Schulz (talk) 19:27, 30 January 2011 (UTC)

Acetone (i.e. nail polish remover) is often useful for dissolving glues. Use a cotton swab to spread some (liberally) over the glued area, and then after it's had a few minutes to work, take a razorblade to it. It might only dissolve partway through the glue the first time -- if so, cut in as deep into the glue as you can, and then apply more acetone and repeat. -- Mesoderm (talk) 19:34, 30 January 2011 (UTC)

Note that if we're talking about a welding glue like butanone, which is really a solvent as I noted above, then any solvent that can dissolve the joint may damage, weaken, or at least deface the material with which you're working. Any "liberal" application might be tested on a throw-away piece of the same material to ensure you get the results you desire. -- Scray (talk) 21:20, 30 January 2011 (UTC)

To answer your question properly you're going to have to tell us what "standard tube glue" is. Ariel. (talk) 22:45, 30 January 2011 (UTC)

EEK! I would be especially careful of acetone as it could dissolve more then just the glue! Solvents can soak into the plastic and melt them or soften them to the point where they become impossible to set. I would try the very careful razor approach. Vespine (talk) 01:23, 31 January 2011 (UTC)

Thanks to all for pointing this out -- I've used acetone to remove glue in the past without problems, but I'll definitely be more careful in the future. What types of plastics specifically do you have to worry about? -- Mesoderm (talk) 02:23, 31 January 2011 (UTC)

Codeine and its counterparts

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis, prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. If you have a question about drugs to take if you have an allergy, please ask a physician or pharmacist.

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the Reference Desk's talk page. If you have a question about drugs to take if you have an allergy, please ask a physician or pharmacist.--~~~~

I have taken this discussion to the Ref Desk talk page. Bielle (talk) 22:14, 30 January 2011 (UTC)

Highbeam's offer of scientific magazines

Does Highbeam have many top scientific magazines among its offer? Quest09 (talk) 21:04, 30 January 2011 (UTC)

Here's a list of the science magazines they have. Red Act (talk) 21:12, 30 January 2011 (UTC)

Well, I can't seem to find any which is really highly prestigious.Quest09 (talk) 21:18, 30 January 2011 (UTC)

Agree - no first-tier journals. The latter are a bit hard to define dogmatically, but ScienceWatch, Eigenfactor, and Science Gateway have lists that might be relevant. -- Scray (talk) 21:40, 30 January 2011 (UTC)

Big alignment

I heard that our solar system and all the planets and the sun will be aligned with the center of the milky way galaxy in next year if so will this be noticeable. --93.107.73.219 (talk) 21:11, 30 January 2011 (UTC)

• It's not the case, and it wouldn't be noticeable everyday effects even if it were. After the moon and the sun, the gravitational effect of heavenly bodies on the Earth is basically negligible. Jupiter is the next most significant, and you've never been affected by its gravity nor observed the effects of such, and we align with Jupiter roughly once a year. — Lomn 21:45, 30 January 2011 (UTC)
• This is just part of the 2012 Hoax. A large part of the sordid story is at 2012_phenomenon#Galactic_alignment. In short, there is no particularly exciting multiple conjunction in 2012. The Earth, the Sun, and the galactic center line up roughly once per year. --Stephan Schulz (talk) 21:52, 30 January 2011 (UTC)

Subterranean flows of water (contains spoiler of Philip Pullman's The Tiger in the Well)

Starting on page 265 of Philip Pullman's The Tiger in the Well is talk of subterranean rivers and springs and whatnot. Mentions of houses crumbling into such bodies of water (and sewage and other wastes) after storms seem to be based on historical fact. Where can I read more about this phenomenon, both as a matter of fact and of history. Thanks. 66.108.223.179 (talk) 23:06, 30 January 2011 (UTC)

See Underground river, Sinkhole, Cenote and be sure to follow the "See Also" links from those articles. Ariel. (talk) 02:03, 31 January 2011 (UTC)

Star formation

Is it right that stars can blow up and their remains recondense to form new stars? Is it also right that this cycle cannot continue forever but must gradually wind down? —Preceding unsigned comment added by 86.135.27.52 (talk) 00:03, 31 January 2011 (UTC)

In two words, yes and yes. in more words, i'm not sure where to start, perhaps with Stellar evolution and entropy.. feel free to come back if you have any more specific questions. Vespine (talk) 00:19, 31 January 2011 (UTC)

Also take a look at Metallicity. As stars age, they burn Hydrogen into heavier elements. When they "blow up" (into red giants, or even supernovae), some or all of the material of the star is ejected from the star. This can become part of a later population of stars. But not all of the ejected material is Hydrogen. The heavy elements have a number of interesting effects (they catalyse different fusion processes in the star), but, in particular, they cannot themselves fuse in the same way Hydrogen does. Eventually, a region of space will run out of Hydrogen to form stars from. --Stephan Schulz (talk) 00:32, 31 January 2011 (UTC)

(Edit Conflicts) Yes to both questions.

As is detailed in Star formation (surprise!), stars form from condensing clouds of interstellar gases and dust. Some of the gases are left over from the initial creation of the universe in the Big Bang, but this only made Hydrogen (H) and Helium (He) (and maybe a little Lithium (Li)): all other gases and (non H/He) dust have been created by nuclear fusion processes within stars (see Stellar nucleosynthesis) and then dispersed when they exploded as novae or supernovae; some of the H and He will also have been cycled through those stars without being consumed in nuclear fusion.

However, only a small proportion of stars explode. Most (see Stellar evolution) simply use up all their nuclear fuel and then gradually cool down (although the Universe has not yet existed long enough for any of the resultant white dwarfs to stop glowing from their fusion-created heat). Also, some of the material forms not stars but planets and associated materials, which do not get redispersed much. Even when a star does explode, some of its material usually remain concentrated as a white dwarf, neutron star or black hole.

Because these processes 'lock up' some of the universe's material, the amount available for forming new generations of stars is continually diminishing, and will (presumably) eventually run out. When that happens no new stars will form, no fusion will occur, and all the white dwarfs, planetary material, and so on will gradually cool down by radiation which will heat up the colder interstellar (and intergalactic) clouds until everything in the universe is at a uniform (very low) temperature - this is called the Heat death of the universe.

However, the Heat death scenario assumes that the universe eventually stops its expansion and becomes static. If it continues to expand indefinitely, the result may instead be what is called the 'Big Freeze', which may not look much different. If however the universe stops expanding and begins to contract, it may be able to restart star formation for a while before eventually coalescing into a Big Crunch, after which the prognosis is unclear. 87.81.230.195 (talk) 00:43, 31 January 2011 (UTC)

• Thanks for the great answers! I have one more question... does anyone have any clue about the maximum number of times that any material will be recycled through different stars? I'm not expecting an exact answer, but something more along the lines of whether the answer is 3 or one million... 86.135.27.52 (talk) 00:56, 31 January 2011 (UTC)

Depending on how you define "material", closer to 3 (I'd put it somewhere from 10 to 100). The percentage of hydrogen fused by a star varies based on the mass of a star. The sun will fuse, ballpark, 10-20% of its hydrogen, with larger stars fusing less and smaller ones fusing more (red dwarfs, being convective, fuse nearly all of their hydrogen, albeit on much longer time frames). As for the "depending" -- well, a good chunk of that fused hydrogen, now helium, will get fused later on, either in that star or reconstituted in another future star. Is it still the same material? Still, though, there is a finite number of fusion progressions available before net energy becomes negative. Much of those heavy elements end up as the starting mass for black holes. Now, granted, at the end of all this, you can still have the material out and about somewhere (Earth's heavy elements are basically all supernova ash), and so you can get outlier cases where a bit of material cycles as unburnable stellar ash over and over and over, but odds are that a black hole will vacuum it up sooner or later. — Lomn 02:15, 31 January 2011 (UTC)

color changing mug

A Chemical Engineering org I worked with gave me this wonderful mug. It's black but when you pour hot coffee in it, it changes color and reveals the group's logo. Any idea how it works? --Lenticel ^(talk) 01:31, 31 January 2011 (UTC)

My guess is the mug uses thermochromic liquid crystals, making it a kind of liquid crystal thermometer, similar to a mood ring. Red Act (talk) 01:47, 31 January 2011 (UTC)

Thanks for the explanation--Lenticel ^(talk) 02:39, 31 January 2011 (UTC)

By the way, if it's like the ones my wife and I bought about 20 years ago, be careful how you wash it. We found that the thermochromic layer was not well bonded to the mug and was very easily damaged. Of course, the technology may have improved since then. Incidentally, on ours that layer was black at room temperature and turned clear with heat, revealing the pattern painted underneath. --Anonymous, 04:00 UTC, January 31, 2011.

Identify unknown mineral

Hi. I have a very small sample of a mineral, and need some help in identifying it. I have discerned the following properties:

• Type: Non-metallic
• Colour: Red to reddish-brown
• Crystal shape: Nearly amorphous, some flat sides, slightly irregular
• Morphology: Tar-like appearance, may have layers, smooth with creases
• Rock form: Igneous appearance, two 'parallelogram' sides (opposite at angle), two long nearly 'triangular' sides (opposite), one rhombus-like 'trapezoidial' side, one small 'triangle' side (opposite aforementioned)
• Angles: 50° to 130°
• Other minerals: At least two, one may be quartz, other mineral is greenish-brownish-black and earthy striated appearance
• Mohs hardness: >6.0 (scratches stainless steel and glass)
• Lustre: Waxy or resinous
• Diaphaneity: Translucent to opaque
• Specific gravity: ~3 - 5 (imprecise method)
• Reactions: No visible reaction w/ brown vinegar

Any idea what the mineral might be? Thanks. ~AH1^(TCU) 03:30, 31 January 2011 (UTC)

Damiana

does Damiana lower testosterone like weed does