Wikipedia:Reference desk/Archives/Science/2010 April 23

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April 23

Eyjafjallajökull: Tephra color

Some images and videos of the recent eruption show tephra with distinct black or white coloring. I have two questions about this:

• What is the difference in composition between the differently colored tephra?
• Why are the two spatially separated instead of being one big gray cloud ? Also some videos show purely white or mostly black ash clouds; why does the composition and mix seemingly change with time ?

Abecedare (talk) 02:49, 23 April 2010 (UTC)

Just a WAG, but the white doesn't look like tephra, it looks more like cloud, i.e. condensed water vapor, which may be forming at the boundary conditions between the hot air surrounging the ejecta and the cold, damp air due to melting ice and/or the local humidity. Hot + cold + water vapor = cloud, so that may be more of what is happening with the white stuff. The black is the pyroclastic material itself. --Jayron32 02:59, 23 April 2010 (UTC)

Query: WAG="Wild ass guess"? --220.101.28.25 (talk) 03:08, 23 April 2010 (UTC)

That's right. StuRat (talk) 13:50, 23 April 2010 (UTC)

That could be the case, especially since the volcano is/was topped by a glacier, which would be a prime source for immense amounts of steam. That would also explain the spatial delineation, for the temperature in the immediate vicinity of the erupted ash would be too high to allow for steam condensation and cloud formation. Does anyone know for sure ? Abecedare (talk) 03:24, 23 April 2010 (UTC)

There have been several reports that the white clouds are water vapour and the darker clouds are ash. I can't find one offhand - but it's very clear that this is what's going on. SteveBaker (talk) 12:55, 23 April 2010 (UTC)

Not to be too pedantic, but the clouds are not water vapor. Vapor is a gas, which is invisible. The clouds in the pictures, like all clouds and fog, is an aerosol of liquid water droplets suspended in the air. It is the product of condensing vapor, that is of the water gas collecting into tiny microscopic droplets, that makes clouds visible as white puffy things. --Jayron32 00:53, 24 April 2010 (UTC)

Invertebrate stomach

The article on the stomach does not describe its distribution outside of the vertebrates. The link from Chordata to digestive canal incorrectly redirects to human anatomy so that is of little help. Echinoderms are said to have "stomachs" but it seems doubtful that that structure is homologous with the human stomach. Could someone knowledgeable about this subject help me fill in this gap in Wikipedia? -Craig Pemberton 03:50, 23 April 2010 (UTC)

Be bold. DRosenbach ^{(Talk | Contribs)} 14:32, 23 April 2010 (UTC)

Milk protein denaturation

Why is NOT the protein in milk coagulated/denatured on boiling? I am not sure if the question is already asked, please let me know. - Anandh, chennai —Preceding unsigned comment added by 125.21.50.214 (talk) 04:53, 23 April 2010 (UTC)

In of milk, the primary protein is casein. The Wikipedia article on casein itself describes the reason why it does not coagulate. --Jayron32 05:10, 23 April 2010 (UTC)

Thanks. The reason for not being denatured is given but coagulation part is vague. "Casein is not coagulated by heat" but WHY? In industries, an optimal temperature of 43 °C for 4-6 hours is used for preparation of curd (coagulation process?). I wish to know the relation between "In milk, casein is a salt of calcium" and coagulation. May i also know the function of casein? 125.21.50.214 (talk) 06:03, 23 April 2010 (UTC)

Since milk has only one function: nutrition, I would suspect that Casein is the structure it is for ease of digestion. Coagulation is caused by crosslinking between denatured proteins. Denaturing is specifically the loss of tertiary structure. Casein's peculiar organization (it has lots of proline and no cysteine) means that there really isn't any tertiary structure to speak of. It is the breaking of Disulfide bond from a single molecule and the random reforming of those bonds between neighboring molecules that leads to the crosslinking in coagulation. No cystein = no disulfide bonds = no coagulation upon denaturing. Casein, with lots of proline and no cystein, is basically a randomly wrapped somewhat floppy chain of peptides, with nothing holding into any particular tertiary structure. So there is nothing to denature there. The reason it is a calcium salt in milk is because casein's isoelectric pH is much lower than milk's native pH, meaning that it is a negative ion in milk. Being a negative ion, there needs to be a positive counterion which balances its charge, and the most common positive ion in milk is calcium. Hence, it is a salt of calcium in milk. --Jayron32 15:01, 23 April 2010 (UTC)

Cheese is created through heating with the addition of the enzyme rennet (originally sourced from the lining of animal stomaches) and usually addition of acid (sometimes directly in acid-set cheeses, more often indirectly as by-product of intentional bacteria growth) Yum, cheese! See cheesemaking for more including which cheeses must have mold as well. Rmhermen (talk) 13:32, 23 April 2010 (UTC)

Based on my experience with hot chocolate if you bring a pot of milk to boil it will develop a skin of denatured protein on the surface... cyclosarin (talk) 15:13, 24 April 2010 (UTC)

Why exactly do pet parrots mimic (or attempt to learn, if you believe that) human speech?

Is it basically them trying to fit in with humans? WP's talking bird article doesn't explain anything about why. Thanks. --95.148.106.230 (talk) 07:57, 23 April 2010 (UTC)

Birds mimic so that they can learn what sounds they should make, hopefully from more experienced birds of the same species. Graeme Bartlett (talk) 12:47, 23 April 2010 (UTC)

According to this source birds call or sing:

• Calling or singing to attract a mate.

• Calling or singing to establish the bird's territory

• As an indication of the readiness of either or both partners for mating activity

• Maintain a bond between male and female bird

• As a way of communication between parent and young

• As a means of warning it's[sic] mate or other members of the flock of danger

• As a means of gathering a flock together or finding each other

• As a means of encouragement to fellow flock members (such as the case of geese flying and calling to other members to keep up

• As a tactic of intimidation to predators or other birds

• Birds do practice their songs, calling and talking through repetition. Cuddlyable3 (talk) 12:59, 23 April 2010 (UTC)

To answer the Q, rather than talk about why birds sing in general, let me start by saying that some species of birds imitate all sounds they hear. They probably do this to impress potential mates with how fit they are, if they can imitate any sound they hear. This also applies to mimicry of human speech. Of course, if they are rewarded when practicing this (say with food), they may do it even when there's no mate around to impress. StuRat (talk) 13:46, 23 April 2010 (UTC)

Also, since parrots are social animals, when a bird is raised with humans his whole life, he thinks that he is human too. That is one reason they imitate us. --The High Fin Sperm Whale 18:24, 23 April 2010 (UTC)

Many parrot owners don't actually realize this - but pet parrots will often consider the human with which they interact with the most to be their mate. This is basically the reason behind the violent, jealous 'one person parrots'. --Kurt Shaped Box (talk) 04:41, 24 April 2010 (UTC)

See also: Alex (parrot). GeeJo ^(t)⁄_(c) • 19:07, 23 April 2010 (UTC)

Many birds mimic the sounds they hear in their environment, presumably as a means of making themselves more attractive for mating purposes. Also presumably, they have done this for thousands of years prior to the appearance of humans in their environment.

There was a fabulous episode of a TV series on this subject, I think by David Attenborough. One of the exhibits was a bird that had lived all its life in a forest in which logging was taking place. This bird was a brilliant mimic of the sound of a chain saw! Dolphin (t) 05:41, 24 April 2010 (UTC)

In most songbirds, the songs they sing are only partly genetically programmed. There is always a range of possibilities, and a bird learns to sing a specific song by imitating the songs it hears. In most species the range of things a bird will imitate are pretty narrow, but there is a lot of variability, and (as you know) there are some species such as parrots for which the range is extraordinarily wide. Looie496 (talk) 22:11, 25 April 2010 (UTC)

I don't know exactly where I read this but I believe that it's been mentioned on the desk by someone else before too (with a source), that parrots will use mimicry to communicate with specific members of their flock - they 'parrot' the subtle vocal characteristics of the bird they wish to 'talk' to/at. As an aside and in reference to the above, I once saw a YouTube video of a pet Budgerigar that had been hand-raised by humans from the egg - and his vocalizations were extremely strange. Aside from a generic tweet (which sounded un-budgielike, even to my tin ears) and the standard cackle (hard to describe - but it's the one that appears to come from deep in the throat, not the mouth), every other sound he made was constructed from snippets of human speech and noises heard around the home, all spliced together into a song, of sorts. It would be interesting to see what would happen if they placed a budgie with a standard upbringing in there with him - I don't know for certain but based on my personal knowledge of how other parrot species will react to 'humanized conspecifics', I'd imagine that the reaction would be something along the lines of complete bewilderment from both birds, followed by a very difficult process of acquaintance and acceptance, with much fighting. --Kurt Shaped Box (talk) 01:13, 26 April 2010 (UTC)

gravity-south pole

Is the value of gravity same all around the earth? Is that like things/creatures at the south pole has lesser gravity comparitively because it is at the bottom of the earth (seems like clinging to it, things will fall off):-)? How is the south pole affected by earth's rotation/revolution? Is gravity because of earth's rotation (too)? Is the escape velocity same all around the earth? I dont understand physics well!!!125.21.50.214 (talk) 11:29, 23 April 2010 (UTC) anandh.

see here--BozMo talk 11:37, 23 April 2010 (UTC)

The south pole is only the "bottom" of the Earth by modern mapmaking convention (some old maps put East at the top). Gravity doesn't care about up and down; it just pulls everything towards everything else, so there's nothing gravitationally special about the South Pole. Earth is by far the biggest thing near us and gravity is very weak, so, to a first approximation, gravity just pulls us towards the center of Earth.

Now, earth's rotation does have an effect. The centrifugal force caused by Earth's rotation (same thing that causes your arms to be pulled out if you spin around in place fast) causes things to be lighter, the closer they get to the Equator. But things are only 0.3% lighter there than at the poles, so it's not something that you'd notice. Paul (Stansifer) 12:31, 23 April 2010 (UTC)

The shape of the earth has an effect too - the poles are closer to the center of the earth than the equator - hence more gravity there. There are also differences due to mountains - which get you further from the center (hence less gravity). Deposits of denser or less dense rock will also make a difference to local gravity. See Gravity anomaly, Physical geodesy SteveBaker (talk) 12:53, 23 April 2010 (UTC)

The radius of the Earth varies from 6,357 km at the poles to 6,378 km at the equator, and (6,378/6,357)² = 1.0066, so this reason only increases the gravity at the poles by 0.66% compared to the equator. Actually it'll be slightly less than that due to the pull of the equatorial bulge itself, but that's harder to compute. Combining that with the centrifugal effect, which is more accurately 0.35%, we see that you weigh no more than about 1% more when at the poles. --Anonymous, 03:45 UTC, April 23, 2010.

9 volt battery

I often test if 9 volt batteries are still good by touching them on my tongue and seeing if they give a small shock. Would touching a 9 volt battery to a hypothetical persons penis/clitoris produce an orgasmic effect? 82.43.89.71 (talk) 12:22, 23 April 2010 (UTC)

Wikipedia has an article on Nine-volt battery. Connecting the male and female terminals is inadvisable as it leads to premature discharge. Cuddlyable3 (talk) 12:50, 23 April 2010 (UTC)

Premature discharge? Cue rimshot. Kingsfold (talk) 16:14, 23 April 2010 (UTC)

No - if that worked then every sleeze-bag on the Internet would be selling devices that do exactly that. SteveBaker (talk) 13:01, 23 April 2010 (UTC)

That is quite independent of whether it works, and they do. --Stephan Schulz (talk) 13:48, 23 April 2010 (UTC)

See Erotic electrostimulation. PrimeHunter (talk) 16:24, 23 April 2010 (UTC)

Touching the device to the hypothetical person might constitute battery, but we cannot give legal advice. The current from the battery would depend on the resistance. Salt on the skin would likely lower the resistance. We do not seem to have an article on Salt and battery. Alessandro Volta tested his batteries (or "piles") in a similar manner, but by using other parts of his own body. This might be considered "self abuse," and if done to the eyes like by Volta, Ritter or Charles Darwin, might cause you to go blind. Some 19th century writers, going in the opposite direction, speculated that sexual intercourse might be pleasurable because of the electricity generated by the act. 19th century quack "doctors" did lots of truly scary electrical experiments, sticking electrodes about everywhere to prevent "spermatorrhoea," which should absolutely not be imitated. In the late 19th century doctors attempted to treat "female complaints" with electricity, either DC or AC, with mixed results. By the 1970's women started using batteries not directly but instead to power vibrators, and found this an effective way of obtaining orgasms[1]. Edison (talk) 22:30, 23 April 2010 (UTC)

The minute current may stimulate nerves in the genitals like it does to the tongue.This could technically simulate nerve impulses and thus fooling the body into having and orgasm.I highly do not recommend doing this as the genitals are one of the most sensitive organs in the human body and damage to them could be potentially irrepairable.

Global warming.

Cenozoic global temperatures (right-to-left)

This subject has me thoroughly confused! The sea level is rising, caused by melting ice, caused by global warming, caused by increase of carbon dioxide in the atmosphere. That is what it seems to me that scientists have stated. Am I right? If not, then ignore the rest! cdiac.esd.ornl.gov/trends/co2/contents.htm claims that atmospheric carbon dioxide concentration jumped from 275 ppm in 1750 to 367 ppm at present. A WHOLE WHOPPING 33%! TERRIBLE? But that is still only .0367% of what we breathe in. Of course I realize that the increase itself is increasing. BUT: mistupid.com.chemistry/aircomp. gives the present level as 330 ppm. Answers.com gives 380 ppm, Wikipedia gives 387 ppm and Physlink 314 ppm. And if I had searched further I would no doubt have found still different figures! AND: Whilst the increase from 1750 to Physlink is only 14%, the discrepancy between Wiki and Phys is an enormous 23%. When I did chem. anal. half a century ago, if I had come up with such varied answers, my employers would have kicked me out on the spot! LASTLY: National Geographic some years ago stated that (I think) some few million years ago the carbon dioxide in our atmosphere was 5x the present level. AND LOOK WHAT HAPPENED: WE DID!!!!!! Not feeling at all comfortable with a PC, nor with how to reply to an answer (vide my query re EMP weapons in Smolensk a few days ago), could some kind soul PLEASE tell me, step by step, how to go about this? Thank you!!!220.253.193.132 (talk) 13:01, 23 April 2010 (UTC)

I suggest you start with Carbon dioxide in Earth's atmosphere BozMo talk 13:05, 23 April 2010 (UTC)

Some points:

1) Yes, CO₂ levels were higher at times in Earth's history, but so were sea levels. The problem isn't really so much that we are headed to an inherently dangerous level of carbon dioxide, but that we have chosen to build on the shores of oceans around the world, which means that billions of people will be subject to increased flooding.

2) Yes, the level of carbon dioxide is a tiny portion of the atmosphere in total. If the atmosphere was all greenhouse gases, then we would have a planet like Venus, which would kill off all people (and most life) on Earth.

3) Variations in measurements around the Earth can be expected to be larger than those measured in a laboratory setting. There will be variations by location and date, as well as due to different measurement methods. However, all the numbers you listed show an increase; that's the most important part. StuRat (talk) 13:33, 23 April 2010 (UTC)

Just pointing out that StuRat in #1 above says "the problem" is coastal flooding, whereas of course there are many, many other problems. Our Effects of global warming article discusses some. If you take an eons-long view, then it probably doesn't matter to you that, for example, as this article discusses, higher temperatures in the Pacific Northwest are giving the bark beetle a longer seasonal life each year, which has allowed them to kill 10 times as many trees as they have historically — a million years from now, who's going to care about this particular problem, true; but there are knock-on effects from these problems of today that make a lot of people care today. Comet Tuttle (talk) 17:07, 23 April 2010 (UTC)

"...all the numbers you listed show an increase..." It's not like these guys have forgotten how to do statistics. Countless studies show a significant rise that can't be contributed to randomness. At this point in the debate it isn't really a question of whether CO2 is the culprit. It is, and it is making temperatures rise. What is still up for debate is hanging a world catastrophe on changing temperature. If you want to argue against Global Warming give them their entire argument save the global disaster. Yes CO2 is rising due to us, and yes it will probably impact the climate. No matter how strong the correlation of the data and no matter how certain we are that it is our own fault, these facts don't necessitate drastic climate changes that lead to a series of uncontrollable steps where very bad things happen.

Nowadays, you won't find too many reputable sources screaming Armageddon. They have backed off that claim for now, and for good reason. It is pretty uncertain what will happen in the future, even with all the data we have. However, I found a few claims on the Global Warming quite interesting:

"In a literature assessment, Smith and others concluded, with medium confidence, that:

-climate change would increase income inequalities between and within countries

-small increase in global mean temperature (up to 2 °C by 2100, measured against 1990 levels) would result in net negative market sector impacts in many developing countries and net positive market sector impacts in many developed countries

-the aggregate market sector impact (i.e., total impacts across all regions) of a small increase in global mean temperature would amount to plus or minus a few percent of world GDP."

Conclusions like these point to a growing realization that it isn't very likely anything good will come of Global Warming, but the first one seems a little shaky. In my opinion, no one should be trying to speak this conclusively. It is very easy to be wrong when correlating broad trends with temperature. That should be your main line argument, not questioning the research.

Mrdeath5493 (talk) 17:16, 23 April 2010 (UTC)

So, according to you, positive market impact in most civilized countries is not a good thing?! 76.103.104.108 (talk) 01:49, 28 April 2010 (UTC)

Atmospheric CO₂ concentrations lower than 387 ppm are likely outdated. Global concentrations have increased more from 1800 to today (+107 ppm) than it has between the peak of the last ice age to 1800 (+100 ppm). ~AH1^(TCU) 21:40, 23 April 2010 (UTC)

Perpetual motion machine

In string theory, the basic building blocks of matter are said to be tiny vibrating strings. The frequency to which they vibrate determines their properties.

Where do they get the energy for this vibration? If they vibrate forever, they are perpetual motion machines. If they don't, what will the universe look like when all strings have ceased to vibrate? What will be these strings' properties? --13XIII (talk) 14:20, 23 April 2010 (UTC)

Note that only the type of perpetual motion machine where "you can pull energy out and still have it run forever" is impossible. Having an object move forever without removing energy is fine, in a frictionless environment. One of Newton's laws, after all, is that "An object in motion stays in motion, unless another force acts upon it". StuRat (talk) 14:47, 23 April 2010 (UTC)

But doesn't the movement itself remove energy from the string? Since vibration means mechanical oscillations about an equilibrium point, the string would vibrate back and forth. Accelerate back, decelerate, accelerate forth, decelerate, etc.--13XIII (talk) 15:22, 23 April 2010 (UTC)

No. Under Newtonian physics the vibration would give off heat, but strings are too small for those laws to apply. Quantum mechanics rules at those scales. StuRat (talk) 15:32, 23 April 2010 (UTC)

It is not necessary for something that appears to "vibrate" to be accelerating and decelerating. It could be an effect of dimensional perspective. Imagine a merry-go-round spinning. Due to your dimensional limitations, you cannot see the main mechanism. You can only see one horse on it. Further, you can only look it from the side and you cannot sense any sort of depth. What you end up seeing is a horse moving back and forth - but it is not accelerating/decelerating. It is rotating. -- kainaw™ 17:38, 23 April 2010 (UTC)

In a simple piano-string vibration...during acceleration towards equilibrium, the string gains kinetic energy. The acceleration comes from the potential energy of the string being away from equilibrium. During deceleration, the kinetic energy is converted back to potential energy as the string moves past the equilibrium state. There's no net loss of energy, just change of its form. DMacks (talk) 17:56, 23 April 2010 (UTC)

There certainly is a loss of energy from a vibrating piano string, some of which becomes air vibrations (sound). StuRat (talk) 19:34, 23 April 2010 (UTC)

Vibrating objects do radiate away their vibrational energy until they reach equilibrium with the environment. Quantum mechanically, though, the lowest energy state still has some vibrational motion, because of the uncertainty principle. Even in a vacuum, a system can remain in that vibrational state "forever" (though not really forever, because there are probably other allowed decays with extremely long half-lives, like spontaneous fusion or proton decay).

The other thing, though, is that the premise is false. The known particles aren't different vibrational states of strings (assuming that known physics can be reproduced within string theory at all, which still isn't known). They are different vibrational states of the vacuum, but that's already true in ordinary particle physics. It has nothing to do with the stringiness of the strings. I don't know why so many of the popularizations make a big deal about string vibration. Probably it's because then they can talk about the physics of music, a very old and well-understood topic, and pretend that they're teaching string theory. -- BenRG (talk) 19:28, 23 April 2010 (UTC)

If vibrators give off heat, that may explain my singed pubes.--79.76.130.158 (talk) 21:22, 23 April 2010 (UTC)

Atoms are constantly bouncing off each other, but they don't loose any energy by doing so. Energy lost by one atom is gained by another, which then goes to another - as long as no energy leaves the system, it can do this forever. Vibration is the same - it moves one way, stores energy in tension, then retrieves the energy on the way back, and does it over and over. As long as no energy is lost from the system it can do it forever. (With the macro objects friction steals energy.) The only reason perpetual motion machines don't work is that there is friction which steals energy. Otherwise they could actually go on forever (as long as you don't try to do anything with them.) Ariel. (talk) 22:34, 23 April 2010 (UTC)

You must also remember that the string theory is not a fix it all solution.There are many unanswered questions about it.

Antimatter bomb

Assuming equal amounts of fuel, would an antimatter bomb be more powerful than an atomic bomb? What would the explosion from an antimatter bomb look like? --71.144.122.18 (talk) 14:36, 23 April 2010 (UTC)

It would be on the order of 10,000 1000 times more powerful. If you decreased the amount of antimatter to get a similar yield, then it would probably look similar to an atomic bomb. However, a large anti-matter bomb, if it was possible, might rupture the crust of the Earth, causing volcanic effects absent in an atomic bomb. StuRat (talk) 14:42, 23 April 2010 (UTC)

How did you find your way here, without finding your way to Antimatter weapon first?--Aspro (talk) 14:46, 23 April 2010 (UTC)

Modern fission weapons will fission about 40% of their fuel; each atomic fission converts (roughly) 0.1% of its mass to energy; therefore about 0.04% of the total fuel mass is coverted to energy. (See Mass–energy equivalence#Efficiency.) Fusion weapons do better (efficiency-wise), converting about 0.3% of their fuel mass to energy. A matter-antimatter weapon, in contrast, ideally converts 100% of its fuel mass to energy. On a weight-for-weight basis – neglecting the mass of any containment, triggers, delivery system, etc. – the matter-antimatter bomb will deliver 300 times the energy of a thermonuclear fusion bomb and about 2500 times the energy of a fission bomb.

As for the appearance of the explosion, I'm not sure — perhaps StuRat has sources for his statements above? I'll note that the output of an antimatter bomb will (initially) consist of very high energy (~1 GeV) gamma rays, instead of the MeV gammas and hot plasma of a fission or fusion explosion; does someone know how efficiently that energy will couple into the bomb casing, or to adjacent air, earth, and buildings? My gut instinct is that for a ground burst of equivalant energy the appearance will be comparable (at any distance where an observer would live to tell about it), but I suspect there will be marked differences at very high altitude or in space (where escaping gamma rays won't be absorbed by surrounding matter). TenOfAllTrades(talk) 15:02, 23 April 2010 (UTC)

Shouldn't that 300 be 333 ? StuRat (talk) 15:13, 23 April 2010 (UTC)

It should be if you're making unreasonable assumptions about the precision o f the value 'about 0.3%', yes. Otherwise, no. TenOfAllTrades(talk) 16:23, 23 April 2010 (UTC)

According to Pastafarianism, will the universe be destroyed by equal amount of pasta and antipasta coming into contact with one another ? :-) StuRat (talk) 15:07, 23 April 2010 (UTC)

So does that mean that an antimatter bomb would have an effect for 10,000,000 kilometers in every direction, since the largest nuclear weapon caused destruction up to 1000 kilometers away? --71.144.122.18 (talk) 14:59, 23 April 2010 (UTC)

First of all, blast radius is not directly related to bomb energy yield. See blast radius. More often, yield energy is proportional to (blast radius)² or even in some cases, (blast radius)³. For the mathematically uninclined, this means that increasing the energy of the explosion will only increase the blast radius "a little bit." In fact, when modeling nuclear weapon yield, many practical, realistic estimates place the proportionality closer to E_yield = (blast radius)⁵: in other words, you need 100,000 times as much energy to generate a blast 10x as large (measured by spatial radius). More energy does mean more destruction in general, but the relationship defining "how much more" is very complicated. Nimur (talk) 15:21, 23 April 2010 (UTC)

No, not at all:

1) First, what nuclear weapon caused destruction 1000 km away ?

2) Let's use Ten's 300 times more powerful figure, since the maximum current bomb you refer to is likely a thermonuclear bomb, not a simple atomic bomb.

3) (See Nimur's comments above about blast radii.) StuRat (talk) 15:26, 23 April 2010 (UTC)

The Tsar Bomba makes claims that it broke windows and was felt 1000 km away, but those claims are uncited. The mesured zone of total destrucion was a much smaller 35 km radius. Googlemeister (talk) 15:45, 23 April 2010 (UTC)

Also note one practical effect of the diminishing returns from larger bombs is that many small bombs are far more destructive than one big bomb, where the total mass of explosives is equivalent. StuRat (talk) 15:57, 23 April 2010 (UTC)

So what would the blast radius be of an antimatter bomb with 500,000 kg of fuel (roughly 20 times Tsar Bomba)? Ignore the problems with building and dropping such a bomb, because this is for a sci-fi story which takes place far enough in the future that they've been solved. --71.144.122.18 (talk) 16:38, 23 April 2010 (UTC)

The bomb won't be 100% efficient as a lot of the energy will be lost in the form of neutrinos. Protons and anti-protons consist of quarks, so you get mesons when they decay. But then you can get mesons consisting of a quark and the anti partner of another type of quark. This will then decay into a muon and a neutrino. The energy lost in the form of neutrinos should be easy to estimate, the article on the antimatter bomb gives a figure of 60%.

Now, I think the effects of explosions should be universal in the sense that whenever you deposit a large amount of energy very quickly in some small volume, then the effects far away from that region should not strongly depend on the details of how that energy was deposited in a first approximation.

This then means that you can just as well use this calculator to compute the effects of an asteroid impact with the same kinetic energy. You should then, of course, disregard typical effects associated with impacts, like that of ejecta. But perhaps an underground explosion would be similar also in these respects. Count Iblis (talk) 17:14, 23 April 2010 (UTC)

For example, a 3*10^11 Megaton TNT explosion should cause the following effects at 10,000 km distance. The seismic effects should be:

The major seismic shaking will arrive at approximately 2000 seconds. Richter Scale Magnitude: 12.3 (This is greater than any earthquake in recorded history) Mercalli Scale Intensity at a distance of 10000 km:

VI. Felt by all, many frightened. Some heavy furniture moved; a few instances of fallen plaster. Damage slight.

VII. Damage negligible in buildings of good design and construction; slight to moderate in well-built ordinary structures; considerable damage in poorly built or badly designed structures; some chimneys broken.

The effects of the air blast should be:

The air blast will arrive at approximately 30300 seconds. Peak Overpressure: 295000 Pa = 2.95 bars = 41.9 psi Max wind velocity: 370 m/s = 828 mph Sound Intensity: 109 dB (May cause ear pain) Damage Description:

Multistory wall-bearing buildings will collapse.

Wood frame buildings will almost completely collapse.

Multistory steel-framed office-type buildings will suffer extreme frame distortion, incipient collapse.

Highway truss bridges will collapse.

Glass windows will shatter.

Up to 90 percent of trees blown down; remainder stripped of branches and leaves.

Count Iblis (talk) 17:29, 23 April 2010 (UTC)

If Iblis's math is correct on the amount of Mtons, then this blast would exceed the power of the Chicxulub crater impact that allegedly killed the dinosaurs by 3000x. Googlemeister (talk) 18:24, 23 April 2010 (UTC)

Just one small note. It's not correct that if a perfectly efficient antimatter bomb was possible, it would convert 100% of the mass of the antimatter into energy. The correct number is 200%, since an equal amount of normal matter would necessarily be converted. --Anonymous, 03:51 UTC, April 24, 2010.

Also, (unlike a nuclear fission/fusion bomb) it's certain that 100% of the antimatter will react with regular matter and be converted to energy - it's not like there could be antimatter 'left over' that could be scattered as fallout - as is the case with an atom bomb. So in that sense, it is 100% efficient. The issue is whether the resulting energy is emitted in ways considered useful for destruction of the target. That's where the difficulty lies. Also, a less-than-fully-efficient atomic bomb may actually cause you enemy more trouble because 'dirty fallout' that's still full of radioactive plutonium/uranium could easily kill more people and cause a larger area to be uninhabitable than a 'clean' bomb that would convert 100% of radioactive material into unreactive byproduct. SteveBaker (talk) 16:48, 24 April 2010 (UTC)

Like Steve just said , antimatter bobs are highly efficient when compared to modern day nuclear fusion/fission bomb.It would theoretically covert 100% of its mass into energy. This is theoretically true but if your look at it in a practical standpoint it will not release 100% of its energy.A extremely minute amount of antimatter may still remain.And to answer the original question ; Yes.An antimatter bomb would be immensely powerful when compared to a standard nuclear fission/fusion bomb as almost 100% of its matter is turned into energy.Modern nuclear fusion/fission bombs only covert a little of their mass to energy.This would potentially make antimatter bombs fallout free weapons .The intense radiation maybe bigger that anything we have seen, basically could sterilize anything in the blast radius

Penguins

How would the creationists today explain the flightless yet winged penguins? --Reticuli88 (talk) 14:44, 23 April 2010 (UTC)

I don't think that any explanation beyond "That's just the way God made it" is necessary for some people. --Jayron32 14:49, 23 April 2010 (UTC)

They use the wings to help them swim. --71.144.122.18 (talk) 14:52, 23 April 2010 (UTC)

Perhaps they evolved to survive The Deluge? Nimur (talk) 15:24, 23 April 2010 (UTC)

Maybe they would rather formulate it "God works in mysterious ways" if others try to point out seemingly illogical things. PrimeHunter (talk) 16:47, 23 April 2010 (UTC)

Or better yet "Who are you to question God ?", which implies that it's a sin to question God, and by extension God's representatives (the Church). StuRat (talk) 17:33, 23 April 2010 (UTC)

Us creationists take the easy way out of tough questions :)) Rimush (talk) 17:38, 23 April 2010 (UTC)

Penguin wings are anything but useless. They couldn't swim without them. --The High Fin Sperm Whale 18:21, 23 April 2010 (UTC)

See for example [2] and [3]. Gabbe (talk) 19:01, 23 April 2010 (UTC)

If you call the wings "flippers" then their construction makes pretty good sense from either point of view.APL (talk) 21:23, 23 April 2010 (UTC)

The whole problem here is that creationism is a pseudo-science. It claims the trappings of a science without following the scientific method (that's the definition of a pseudo-science). Because of that, creationists can just make up any story they like - they are (evidently) not required to provide proof of anything they say in order to keep their believers happy. Hence, asking these kinds of questions doesn't really allow you to prove or disprove anything whatever. SteveBaker (talk) 01:00, 24 April 2010 (UTC)

No explanation is necessary. I mean, their wings are used for balance, and for swimming. Just because they can't use them to lift off, it doesn't mean that they weren't invented by The Deity, or what have you. Besides, in the deadly Antarctic winter, having longer extremities is not good for your survival prospects. You want short little stubby wings so you don't lose copious amounts of body heat. Vranak (talk) 14:30, 24 April 2010 (UTC)

Well, that's not really true. Science can explain why penguins are birds - they evolved from other birds. They have wings because that's what birds have. They have evolved some features for survival in the extreme cold, others for swimming and so on...but (interestingly) they have not lost all of the features that birds evolved for flying (wings - and the huge chest muscles required to flap them). We can completely explain more or less every aspect of why a penguin is like a penguin is. The trouble for the ID "explanation" is to ask why penguins are like birds at all. Why don't they have propellers or water jet engines like a jet ski? The ID/creationism approach doesn't offer any degree of explanation whatever...the answer can only be "because the designer decided to do it that way". Since this designer produces some extraordinarily crappy designs sometimes - we have to wonder at his/her/its' sanity. I think an explanation is required - and the ability for science to provide one is a compelling thing. Why choose to believe a pseudoscience that can't explain a single fact about the nature of plants and animals beyond "well, just because the designer did it that way". That's a crappy system! I could understand choosing an "intelligent design" answer if there were no credible alternative - and that's why intelligent people believe in it hundreds of years ago when we had no better explanation. But now we have a really comprehensive, elegant explanation that fits all of the facts perfectly, choosing the ID/creationism answer is no more than pathetic dogmatism. SteveBaker (talk) 01:45, 25 April 2010 (UTC)

Creationists might point out that on board Noah's Ark there were two examples of every genus of bird. While Noah was waiting for some sign that the water had receded sufficiently to expose a few trees, all the birds remained in their cages on board. However, one breeding pair managed to sneak away! These were the first penguins! There were no trees to be seen so eventually they ended up in the water and had to keep swimming. They swam south and kept going until they reached the southern hemisphere (which is where the penguins live.) By the time they arrived in the southern hemisphere they were damn good swimmers and they never felt the need to fly again. And that is why there are penguins, to this very day. Dolphin (t) 11:32, 25 April 2010 (UTC)

That makes no sense whatever! Firstly, (as creationists are keen on pointing out) in their world view species most certainly don't change over time - they are created by god/the-designer and don't change from that point onwards. The idea that one pair of (presumably duck-like) birds swam so far and so long that they changed into penguins implies a kind of Lamarkism - it would be tantamount to agreeing with evolution! Most ID/creationist types don't deny that the form that plants and animals take is determined by their genes - they simply refuse to believe that those genes change over time. A few will grudgingly concede that genes may be lost over time - but none of them will agree that genes are ever added or improved over time - because that would require evolution. So I don't really see how creationists could logically subscribe to this view of how penguins came about (although anything is possible since logic is never their strong point). Furthermore, that kind of thing is easy to disprove - for example: A hundred generations of humans have learned to read - and practiced reading all their lives - yet not one child has ever been born with an innate ability to read. That kind of evidence is why Lamarkism is so out of favor these days. SteveBaker (talk) 18:47, 25 April 2010 (UTC)

Dolphin51's Noah's ark story is a joke. At least I hope it was meant as a joke, since it's not true. And BTW the Noah's ark is specifically considered as a miracle, and not something that could actually be made, so logical arguments about its existence are meaningless. Ariel. (talk) 05:46, 26 April 2010 (UTC)

Ariel is right. It was my attempt at humour. Dolphin (t) 11:34, 26 April 2010 (UTC)

These are the steps of the scientific method:

Ask a Question Do Background Research Construct a Hypothesis Test Your Hypothesis by Doing an Experiment Analyze Your Data and Draw a Conclusion Communicate Your Results

You cannot do an experiment to recreate life, whether you are a creationist or an evolutionist. This relegates the area of origins to the realm of philosophy. Neither creation nor evolution can be proved in a laboratory. The scientific method does not apply in this area. You would need to search for evidence to see which system gets the weight of proof.

Just a note: The story of Noah's Ark is true. Animals could have easily fit in the ark. The wood was durable, and the sealant would work well. It is not hard to build a covered raft, which is what Noah's Ark was. Animals that could have been too big to fit on the ark, such as dinosaurs, could have been led on when young.

Why did the penguin have to adapt to the cold Antarctic? They could have been created to be able to cope with extreme cold. Species could also undergo inbreeding. All of the birds which didn't have the proper genes would die in the cold, while the "freak" birds that had extra feathers survived and reproduced.

The complexity of life shows the presence of a Creator, not random scrambling of genes.

Where is the proof for evolution? Did someone reproduce it in a lab?

If anyone wants to make further comments on a creation/evolution discussion, feel free to use my talk page. --Cheminterest (talk) 21:21, 26 April 2010 (UTC)

Exoplanet naming scheme

Why do there seem to be two schemes of naming exoplanets? Science fiction has named planets "Name of star I", "Name of star II", "Name of star III"... for many decades now. Real exoplanets, however, are named "Name of star b", "Name of star c", "Name of star d"... Why is this? There has been a simple naming scheme for decades, so why was a new one invented instead? JIP | Talk 15:16, 23 April 2010 (UTC)

• Extra-solar planets from the Institute of Physics Reports on Progress in Physics (2000) has this to say: "Object names such as 70 Vir (for 70 Virginis) reflect standard astronomical (constellation-based) nomenclature, while other designations reflect discovery catalogues or techniques variously labelled with catalogue running numbers (e.g. HD 114762) or according to celestial coordinates (e.g. PSR 1257 + 12). The International Astronomical Union is in the process of formulating recommendations for the nomenclature of extra-solar planets (cf Warren and Dickel 1998), meanwhile the de facto custom denotes (multiple) planets around star X as X b, c, . . . , according to discovery sequence."
• Following the reference above, W.H. Warren, from the United States Naval Observatory / NASA Marshall Space Flight Center / Hughes STX, had this to say to the IAU General Assembly in 1997: Nomenclature for Extrasolar Substellar Objects: A New Challenge _{HTML version}. Primarily the issue lies in defining a unique and unambiguous way to refer to a specific object which is currently on the edge of detection. If somebody else detects "something else", which might actually be found later to be the same substellar object, we must find a way to ensure that two independent nomenclatures can somehow merge together.

Ultimately, the problem is one of consistency. We don't really know what we are looking at when we see a "stellar wobble," for example. Because extrasolar planets are on the current edge of detectability, we can't be certain of the parameters (including orbital distance, or even sequence number from the star, in the case of multi-planet extrasolar systems). So, to be sure that we refer to the same object, the name is determined by when it is first observed, rather than some parameter (like distance from its star). After significant scientific observation, we might find that (the hypothetical) α-Vir-a, discovered before (hypothetical) α-Vir-b and α-Vir-c, actually lies between those two in orbital radius. Nimur (talk) 15:50, 23 April 2010 (UTC)

Does this mean that extrasolar objects are, when they are first discovered, named with letters, and after they have been confirmed to be planets and their order is known, they get Roman numerals, but it's just that in real life, we have never actually got to the confirmation stage? If this is the case, then I can see the point. But why do the letters start with b? If it's to allow for a to be discovered later, why don't they start in the middle of the alphabet then? JIP | Talk 20:10, 23 April 2010 (UTC)

The method of naming planets with Roman numerals is contained only in science fiction. Even if the order were known for certain, the letter designation would still be used. As the convention of using Roman numerals preceded the discovery of the first extrasolar planets, we can see it as an attempted guess at future planetary nomenclature that, so far, has not panned out. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 20:37, 23 April 2010 (UTC)

I think in response to JIP's question about starting with b - this is because in some conventions, α-Vir-a refers to the star, in other words, to the "primary" at α-Vir. α-Vir-b therefore refers to the first substellar object (either an extrasolar planet, a brown dwarf, or some other "UFO") detected at the location of the α-Vir system. I agree that this nomenclature is not ideal. Nimur (talk) 22:23, 23 April 2010 (UTC)

The star already has a designation: α-Vir. Why make α-Vir-a mean the same thing? Or does α-Vir refer to the entire system? JIP | Talk 06:45, 24 April 2010 (UTC)

In binary systems (those that have two stars) that have only one designation like this, the two stars are givin capital letters so there's α-Virginis A and B. In this sense, the designation for the system is "α-Virginis" and that of the star is A, B, etc. I'm not sure why exoplanet nomenclature starts with b. It's possible that the scheme originally assumed that the principal body would be A/a and subsequent bodies would be B/b, C/c, but then we have examples like 16 Cygni Bb, 30 Arietis Bb, and HD 178911 Bb. BTW, "α-Virginis a" would be the designation of a planet orbiting both α-Virginis A and α-Virginis B (since that is a binary system) though I don't believe this kind of orbit has been detected yet. — Ƶ§œš¹ _{[aɪm ˈfɹ̠ˤʷɛ̃ɾ̃ˡi]} 19:23, 24 April 2010 (UTC)

III

What does the (III) in something like Nickel(III) mean? —Preceding unsigned comment added by 76.230.229.37 (talk) 15:23, 23 April 2010 (UTC)

That is called the oxidation state, and is roughly derived from a simplified description of the number of electrons exchanged in the ionic bond. Nimur (talk) 15:26, 23 April 2010 (UTC)

In other words, it refers to a nickel atom with three less electrons than neutral nickel, or alternately a +3 oxidation state. Most metals have multiple oxidation states, so it is usually necessary to indicate which oxidation state a metal has in a particular compound (for example, to distinguish between a +2 charged nickel ion and a +3 charged nickel ion). The roman numeral is omitted in unambguous cases, which are basically group IA and IIA metals, and a few random other ones (Aluminum is always +3, Zinc is always +2, and silver is always +1, so we omit the roman numerals for those as well). Other than IA, IIA, Aluminum, Zinc, and Silver, you should always include the roman numeral beside the metal name in a compound to indicate which oxidation state the metal is in. --Jayron32 15:33, 23 April 2010 (UTC)

The use of Roman numerals in parentheses following a chemical element's name of symbol is part of Stock nomenclature, a naming system for chemical species.

Ben (talk) 15:45, 23 April 2010 (UTC)

When did chemistry textbooks used in high school switch from some other nomenclature (like prefixes to indicate oxidation state) to the Roman numerals? I seem to recall a different system. Edison (talk) 22:21, 23 April 2010 (UTC)

The older system used the "-ic" and "-ous" suffixes for the oxidation states. Thus, Cu¹⁺ = cuprous and Cu²⁺ = cupric. The problem with that system is that its relative to the element in question; so while Cu²⁺ = cupric, Fe²⁺ = ferrous (since Fe³⁺ = Ferric). So, you still can't tell from the name directly what the actual oxidation state is. However Copper(I) and Copper(II) are unambiguous. Plus, what do you do with an element like Manganese, which has at least 3 common oxidation states (2+, 4+, and 7+) and a slew of other less common, but documented ones. The roman numeral system is MUCH clearer. --Jayron32 00:45, 24 April 2010 (UTC)

IUPAC has been standardizing nomenclature and advocating for standardized chemistry education since around 1913 - but I can't find a definitive date for the introduction and mainstreaming of the roman-numeral system for inorganic compound names. Textbooks may have changed many years after recommendations were made. I learned both systems, and I strongly prefer the numeric system - the "ic"/"ous" system requires much more memorization. As far as elements with more than two oxidation states, there are additional prefixes: per- and hypo-, and there are also common names for certain compounds (for iron oxide, there is ferric and ferrous oxide, also known by common names, including wustite, hemtatite, magnetite, maghemite, and so on). This system reeks of the alchemic origin of chemistry - cryptic code-words and poorly-explained, vaguely latin-ish prefixes and suffixes to designate astrological significances loosely tied to the specific process for generating specific compounds. Nimur (talk) 06:03, 24 April 2010 (UTC)

So the old chemistry set bottles labelled "Cupric Sulphate" and "Ferric Ammonium Sulphate" would now be called what? Edison (talk) 03:28, 25 April 2010 (UTC)

Copper(II) sulfate and Ammonium iron(III) sulfate, respectively. Interestingly, both Cupric sulphate and Ferric ammonium sulfate (but not Ferric Ammonium sulphate) redirect to the correct articles. Buddy431 (talk) 05:27, 25 April 2010 (UTC)

Sulphate is used in Britain, while sulfate is used in America. Neither of them is wrong. --Cheminterest (talk) 21:24, 26 April 2010 (UTC)

Now there is a redirect from Ferric ammonium sulphate to the more pedestrian term. Edison (talk) 02:23, 27 April 2010 (UTC)

The basic assumptions of GR

The basic assumptions of GR are not clear. Steven Weinberg discussed this in his 1972 text. One assumption is nonlinearity. Imagine a satellite attracted to the earth and the sun. In Newtonian theory, the force on the satellite is the vector sum of the forces due to the earth and the sun. According to Weinberg, the force would contain a third term, the attraction to the gravitational fields of the sun and the earth. It is not clear how one calculates this force, nor has anyone tried to verify it. It is critical that we discuss basic assumptions. —Preceding unsigned comment added by Sanford123445 (talk • contribs) 18:14, 23 April 2010 (UTC)

I'm sorry, what is your question? Gabbe (talk) 18:51, 23 April 2010 (UTC)

In newtonian physics, gravity is considered instantaneous, and the force is directly toward the object. In relativity gravitational force moves at the speed of light, so the force is actually directed to where the object was, not necessarily where it is now. Frame-dragging can also cause the direction of gravitational force to be different from where newtonian physics expects. I hope I understood your question. Ariel. (talk) 22:49, 23 April 2010 (UTC)

Again and again and again, critics of GR describe gravity as a "force." In the context of GR, gravity is not a force. It is amazing that this simple point is so hard to grasp: in Einstein's General Relativity, GRAVITY IS NOT -- REPEAT IS NOT -- A "FORCE." Why is it so hard to assimilate this extremely simple, straightforward statement? Repeat after me: in GR, gravity is not a force.63.17.40.87 (talk) 02:38, 26 April 2010 (UTC)

Empty balloons

Ignoring the casing, how much extra buoyancy would a rigid balloon "filled" with a perfect vacuum give over, say, a hydrogen or helium balloon? And since I'm here, a follow-up question: Ignoring the prohibitive cost and availability issues, could you construct a buoyant "vacuum balloon" out of carbon nanotubes which would remain rigid against atmospheric pressure? GeeJo ^(t)⁄_(c) • 18:27, 23 April 2010 (UTC)

Looks like the density of helium is 0.2 g/L, and the density of air is 1.2 g/L. This means that helium is already around 85% as buoyant as vacuum. Hydrogen is around 0.1 g/L, which is even closer. Paul (Stansifer) 18:42, 23 April 2010 (UTC)

There have been a number of lengthy discussions here about this topic. here is one from 2006 and here is one from 2007. APL (talk) 19:19, 23 April 2010 (UTC)

And "ignoring the casing" completely changes things. If you count the casing, the extra buoyancy is totally negated by the container needed. It's difficult to even get a vacuum balloon that's lighter than air, much less lighter than a hydrogen balloon. StuRat (talk) 19:26, 23 April 2010 (UTC)

I asked myself this question once, many years ago. So, in different units:

1000 cubic feet of a vacuum has a lifting power of 80.7 lbs.

1000 cubic feet of hydrogen has a lifting power of 76 lbs.

1000 cubic feet of helium has a lifting power of 74 lbs.

The shell would have to therefore need weigh no more than 4,7 lbs. just to equal the lifting power of hydrogen. I came to the conclusion that using Carbon fiber-reinforced polymer (there was no such thing as nano-tubes back then) it would just be possible to construct a sphere of 1000 cubic feet displacement, with enough strength to withstand a mild vacuum. However, it would be very susceptible to suffering from sudden and catastrophic crushing if it was subjected to the slightest deformation. In other words: providing that the skin was in 'pure' compression -it would withstand atmospheric pressure. Larger spheres would of course displace a larger ratio of air for the given mass of carbon fibre skin. Yet the vulnerability of the skin to crumpling, makes any likelihood that this would be practical proposition outside of a laboratory very remote, to my mind at least. Carbon nano-tubes promise to be stronger and more ridged but I imagine that even hydrogen would be safer to use in any practical application. Also, because of the higher pressure differential present with a vacuum system, it would also lose buoyancy faster than hydrogen and helium. A helium dirigible takes a long time (days) to lose noticeable lift due to a puncture. I later had thought that it would be better to replace the air with water vapour. A slug of ²³⁸plutonium (plus lead shielding) would produce enough joules of heat to keep a large version of such a craft, aloft for years. Hey! and it would be immune to volcanic ash. --Aspro (talk) 19:56, 23 April 2010 (UTC)

Also, you said "mild vacuum", which I would take to mean a pressure lower than 1 atmosphere but significantly higher than 0. To get the extra bit of lifting power, you need something pretty close to a true vacuum or else you might just as well use hydrogen. --Anonymous, 03:55 UTC, April 24, 2010.

I just used the word 'mild' to indicate it was to the practical limitation one faces due to the plastic 'out-gassing' and I have no recollection now of what that was, nor what we could achieve with fibre bonding resins such as epoxy. The difference though, is a loss of lift which is a magnitude or more too small to bother about. Another problem that appears when trying to scale up to larger sizes, is that being under compression the skin will tend to resonate. This would be in the form of waves, with the direction of amplitude on radial axes. The number of waves dependant on the size and thickness of the skin(and air density, etc., etc.). Then there is the problem that greater air pressure at the bottom will tend to flatten the sphere at that end. This causes peek of higher stress around some of the resonance nodes. All this modelling convinced me, that the only application where these new materials have made a real contribution to mankind is than we can now buy some really good fishing rods.--Aspro (talk) 08:57, 24 April 2010 (UTC)

Number of mammals in the world

I was curious how many mammals there are in the world, not species, but individual citizens of my class, from the smallest infant bat to the largest blue whale. My estimates would put it in the billions, assuming that most mammalian species have less than a million members and there are at most 50 mammalian species as populous as us, but that's basically a guess.--Prosfilaes (talk) 18:53, 23 April 2010 (UTC)

I don't have a source, but I recall hearing that the mouse / rat is the most populous kind of mammal with ~200 billion individuals. Dragons flight (talk) 18:58, 23 April 2010 (UTC)

For the more common domestic mammals, there are 1.3 billion cows, 0.4 billion dogs, 2 billion pigs, and 1 billion sheep. As you can see, these numbers are totally swamped by small mammals like mice and rats. Googlemeister (talk) 19:04, 23 April 2010 (UTC)

 ! These sorts of numbers should not be proliferated without a source! Nimur (talk) 22:24, 23 April 2010 (UTC)

Laugh. I'm inclined to agree. Vranak (talk)

See Cattle, Dog, Pig, and Sheep. Googlemeister (talk) 13:47, 26 April 2010 (UTC)

Which is interesting, if a little problematic without a definition of which type of kind we're talking about. But given that, I'd guess I'm looking at under a trillion mammals, all told, unless there are way more squirrels and bats than I'd assume.--Prosfilaes (talk) 19:13, 23 April 2010 (UTC)

Oil Depth

How deep down and wide does an oil patch or field have to be to be considered worthwhile to drill? —Preceding unsigned comment added by 71.137.251.25 (talk) 19:40, 23 April 2010 (UTC)

That will depend on a lot of factors, so we can't give a very satisfactory numeric answer. Some considerations are; pressure of the oil in the well (higher pressure means less cost to get oil out), price oil is expected to fetch when production comes online (if you have a higher sale price, you can be less efficient), level of impurities in the oil (it costs money to get out stuff you don't want), viscosity of the oil (high viscosity needs to be heated for it to flow well), transport distance to refinery (cheaper to ship oil 5 miles then 500) and method of transport (pipeline, ship etc... cost different amounts). Costs are higher for offshore oil, and while a small patch might be worthwhile if it is 200 ft down, the same patch would not be worthwhile if it was 8,000 ft down, or under 2000 feet of water. Googlemeister (talk) 19:50, 23 April 2010 (UTC)

The ease with which the oil can be produced is crucial to the viability of an oil accumulation, this will depend on both the nature of the oil (light v. heavy) and the permeability of the rock that forms the reservoir. There have been very large oil discoveries that are unlikely ever to be produced due to poor reservoir permeability, such as the Ellida discovery offshore Norway, lots of excitement at the time [4] but no indication that it will ever be produced.[5] Mikenorton (talk) 21:45, 23 April 2010 (UTC)

Hydrocarbon exploration is the task of guessing how much oil is under the ground. Of course, it is almost always easier to get oil if it is shallow. If the oil flows to the surface, that's even better! If it's very deep underground, it's much more expensive to locate and extract it. So, a very complicated set of estimations takes place when somebody thinks they have found some oil, especially if it's very deep underground. Remember, we don't ever really know how much oil is underground until we drill it and extract it; and drilling costs money - so the whole process always boils down to "do we think there is enough oil to outweigh the cost of drilling?"

First, the location is determined as carefully as possible, using a combination of geology, stratigraphy, seismic imaging, exploration wells, and dumb luck. (The percentage of each ingredient varies from company to company, and region to region - in some parts of Saudi Arabia, you don't even really need to look, and wildcat wells, drilled at purely random locations by wealthy oilmen who enjoy casino roulette games, turn up wet often enough to be profitable). Other people do not like making financial decisions based on guess-work, so they prefer a scientifically-informed guess.

In geologically interesting parts of the world, like the Gulf of Mexico, the oil is very deep and far below the water and hidden underneath pesky salt diapirs. The probability of finding petroleum under 4 miles of seafloor below an 8000 foot deep ocean is very low, unless you know where to look. That is where the magic of seismic imaging comes in: using extremely low frequency sound waves, a sonic image of the rock layers is produced, and with a little geology and a lot of luck, you might be able to identify a reservoir. Next, a series of 3D models are designed to estimate how much fluid could possibly have been produced in that region, and the physics of the flow is modeled with very large computers. These extremely accurate numerical physics calculations that are basically giant "for-loops" modeling the fluid dynamics of the entire reservoir over many possible parameters; or focusing the seismic images; and so on. The software can take many months to run, meanwhile earning millions of dollars of profit for contract geophysical processing companies. When the programs are done, the results are plotted on to huge reels of paper (well, it's all digital now, but some still print out the seismic). Next, a geologist uses colored pencil on these printouts and draws the edges of where they believe the reservoir is. Then a numerical physicist computes a precision volume integral bounded by the color pencil sketch, and a petrophysicist multiplies this resulting volume by a porosity value and an extraction factor ("percentage efficiency" of getting oil out of the ground). We now know "how much oil is in the reservoir." If the fluid physics matches the seismic images, a businessman makes a risk analysis and decides whether the color-pencil drawings and the numerical calculations are probably correct. If they are all in order, things move on to the next step. Now the business man calls his economics team, who guess what the price of oil is going to be for the next few years. And the petroleum engineers look at the geophysical results and estimate what kind of expensive technology is needed to drill this prospect, and how quickly the oil can be brought out of the ground. An easy decision is made: if the total value of the volume of extractable oil, integrated over the production curve estimate for the next few years, will cost less than building the rig and operating the boats, then the well will be profitable. At this point, the businessman responsible for this prospect calls up his boss and asks to borrow the company's 600 million dollar drilling rig to float out to his new hydrocarbon prospect. If things go great, the physicists and geologists were right, the well is wet and oil and natural gas flow. If the contractors are lucky, nothing goes wrong and nobody dies in a horrible fiery explosion and the $600 million dollar rig doesn't sink, creating loss of life, an ecological catastrophe and an economic disaster, and everbody profits. Nimur (talk) 15:26, 24 April 2010 (UTC)

Of course, if the oil accumulation is too shallow, you may have to worry about biodegradation of the oil.

As a geologist, I'd just like to point out that I've only used my coloured pencils twice in the last ten years, I spend my days sat in front of a computer workstation where I look at, and interpret the seismic images using specialist software that's been around for more than 20 years. Mikenorton (talk) 15:40, 24 April 2010 (UTC)

I admit it was an unfair jab at the geologists; really I intended to point out the ironic juxtaposition of extremely accurate and extremely inaccurate techniques in the estimation of geologic and economic risk parameters. Everybody, including the physicists, engineers, and economists, have a few "color pencils" in their toolbox to draw over the uncertain estimates. Nimur (talk) 15:46, 24 April 2010 (UTC)

That's OK, I've worked with lots of geophysicists over the years, some of them have difficulty coping with the often enormous uncertainty involved in the geological model, whereas geologists are used to that sort of thing - I was once asked to estimate the age of the formation at the bottom of a proposed well and I replied "definitely Phanerozoic", meaning that I wasn't even sure whether it would be Mesozoic or Paleozoic, but that's just how it is sometimes in frontier exploration. Mikenorton (talk) 15:56, 24 April 2010 (UTC)

GLYCOLYSIS video(s) in µm/Å-scale

Ok, I'm just learning about GLYCOLYSIS today. I'm watching many of the 10 Step Processes done in excellent 3D graphs and chartworks. My question, and note, I don't know a thing about Microscopy. Just naming off some randoms here: Transmission Electron Microscopy Area (TEM), or Positron emission tomography (PET). These types or others, do we even have the capability to watch the 10 Steps of Glycolysis, and/or just basic MitochondriaWorks with Microscopy/Video? If I'm doing video searches, if there are such videos, what to type on me search? Cheers, --i am the kwisatz haderach (talk) 19:57, 23 April 2010 (UTC)

an example of what kind of videos I'm looking for is this youtube vid done on CELL BIOLOGY by:phoenixfilmandvideo. It was made back in 1981, and has a very Cecile B. Demille 10 Commandments-like Narrator. It's chunking together basic Cell Biology infos in just 17 mins. The Microscopy parts, he just skims over. I'm looking for videos where it breaks down each segment, with way smaller in there. Even if not on the Nets, do you have an suggestions on pretty good Biology DVD's with MUCHO-MUCHO ELECTRON MICROSCOPY FEEDS? --i am the kwisatz haderach (talk) 22:39, 23 April 2010 (UTC)

What's the point in some reflexes?

I can see how some reflexes e.g. how the pupils react to changes in light are beneficial to us. But others, I can't see how they would convey any evolutionary advantage at all! For example the knee jerk reflex, the brachioradialis reflex... how can reflexes such as these help our survival? Thanks RichYPE (talk) 20:15, 23 April 2010 (UTC)

I believe they're side-effects of other, more useful reflexes. For instance the knee-jerk reflex is part of the feedback loop that helps us stand upright without consciously worrying about balance. Unfortunately, The Patellar reflex article only dedicates about a sentence and a half to this. APL (talk) 21:14, 23 April 2010 (UTC)

As I understand it, the knee-jerk reflex triggers naturally every time you take a step, causing your lower leg to extend and therefore exert a force to support your weight. It is an essential part of walking. This doesn't mean that every reflex has a function, though -- some might be relics of evolutionary history. Looie496 (talk) 23:25, 23 April 2010 (UTC)

Hi guys thanks for your responses, are there any sources you can cite as I would like to look into this further. Thanks RichYPE (talk) 15:45, 24 April 2010 (UTC)

I would say that all reflexes are protective by definition as they are instinctive in a physiologic way. The knee-jerk reflex is a just a great example of a reflex that has been misappropriated by the nomenclature, in that we call it a knee-jerk because of the way in which it as a reflex, as representative of all or most reflexes are working in the body. But if you're standing against a wall and you doze off and your knees buckle, your quadriceps is extended by the pulling motion of the tendon over the knee area and your Golgi tendon organ is activated by this tension. It then sends a message for your quadriceps to flex, thereby re-establishing equilibrium. DRosenbach ^{(Talk | Contribs)} 02:24, 25 April 2010 (UTC)

Most reflexes have a use, even though they might not be fully understood.--Cheminterest (talk) 21:26, 26 April 2010 (UTC)

Abdomen

Is there a term for the area of abdomen between the belly button and the groin? (ie the bit that hangs below your belt)--79.76.130.158 (talk) 21:27, 23 April 2010 (UTC)

Left lower quadrant (abdomen) or right lower quadrant (abdomen)? ~AH1^(TCU) 21:33, 23 April 2010 (UTC)

The supra pubic area? —Preceding unsigned comment added by 86.4.186.107 (talk) 21:52, 23 April 2010 (UTC)

Wait, you wear your belt around your belly button? I thought belts were worn just over the hips. —Preceding unsigned comment added by 99.254.8.208 (talk) 22:24, 23 April 2010 (UTC)

MY wife and I have this debate. I wear my pants around my hips, and her waistband crosses her belly button. Its apparently not a settled matter... --Jayron32 00:31, 24 April 2010 (UTC)

Hypogastrium --Arcadian (talk) 00:40, 24 April 2010 (UTC)

Ok then, what is the reason for protruding hypogastrium in older women, when they are not necessarily fat?--79.76.130.158 (talk) 11:28, 24 April 2010 (UTC)

Poor tone of abd muscles, esp from previous stretching during pregnancy. It's called a paunch. Also fat, even when limbs are not obviously fat. alteripse (talk) 11:34, 24 April 2010 (UTC)

Ok how can this tone be improved? Sit ups?--79.76.130.158 (talk) 12:52, 24 April 2010 (UTC)

Yes, though crunches may be better. See also leg raise. Abdominoplasty (surgical procedure) is also a rather drastic possibility. --220.101.28.25 (talk) 18:53, 24 April 2010 (UTC)

scuba

how long air will a scuba tank give u? and what compression is used on it? —Preceding unsigned comment added by Tom12350 (talk • contribs) 22:13, 23 April 2010 (UTC)

Diving_cylinder#Breathing_Time --Aspro (talk) 22:24, 23 April 2010 (UTC)

Note that your dive time is usually limited not by the air in your tank, but by your careful adherence to the dive tables or to your dive computer; you have to come up before decompression sickness becomes inevitable. Here is a long FAQ about tank filling, with a little picture of their fill station, and lot of information for technical diving. Comet Tuttle (talk) 22:38, 23 April 2010 (UTC)

The pressure is about 2,900 to 4,400 psi. Ariel. (talk) 22:53, 23 April 2010 (UTC)

The OP seem to be asking for a ball park sort of generalisation. Since a lot of people never get beyond trashing around ( a technical term for a certain swimming style) in depths of no more than 30 feet, for some 20 minutes at a time, on a 70 l tank. Adherence to decompress times is unlikely to take up much time at all. Beyond this however, it is as Comet Tuttle above points out – a more complex question.--Aspro (talk) 23:00, 23 April 2010 (UTC)

yes i just need a generalization. i heard that but it might be hard to control the flow of 2000 PSI tank? does it use a flow regulator? —Preceding unsigned comment added by Tom12350 (talk • contribs) 00:00, 24 April 2010 (UTC)

SCUBA specifically refers to the combination of a pressurized tank and a diving regulator. I have seen an instructor breathe out of an unregulated cylinder by carefully cracking the valve (which is stupid and dangerous). If you dive to shallow depths (where the fun stuff is, anyway), you can get as much as 40 minutes or an hour out of a 3000 psi tank. Your breathe-rate varies by at least a factor of two based on how calm and controlled you are - inexperienced divers waste air and run out long before they otherwise would. At greater depths, you typically consume air faster (because the regulated pressure is higher); but this also depends on controlled breathing. It is possible, but dangerous, to breathe less often when you are breathing high pressure air - your oxygen partial pressure is higher and you can "survive" longer off of each breath; this extends the down-time, but contributes to a variety of hazardous conditions, including decompression sickness. If you need more down-time, technical divers carry multiple bottles and/or use other gas mixes. As has been pointed out, in most deep dives, the limiting factor is not quantity of air, but safety due to compression hazard and nitrogen narcosis, oxygen toxicity, and decompression sickness. Nimur (talk) 01:52, 24 April 2010 (UTC)

The person at the lower right just breathed out.

where does the air you breathe out go? also why is it dangerous to breathe out of a unregulated cylinder ?

To question 1: It depends on whether or not you are using a rebreather or an open-circuit Scuba set. Rebreathers trap exhaled gas, while in open-circuit systems your exhaled breath just bubbles away. And breathing from an unregulated cylinder is very dangerous because it is unregulated. A sudden burst of high-pressure air into your head can cause all sorts of damage to your lungs and breathing system. Having your lungs pop like a balloon because you opened the valve on the cylinder too far doesn't sound like a good idea. Also consider the Newton's third law of motion problems with opening the valve too far. Doesn't sound like fun to me... --Jayron32 04:36, 24 April 2010 (UTC)

Of course our article Scuba diving will be of interest. Comet Tuttle (talk) 06:33, 24 April 2010 (UTC)

how does the air "just bubble away. " is there an exit valve? what about on the scuba fireman where?

The mouthpiece has a second set of valves, including a demand valve and a backpressure valve. The diagrams in our article illustrate how complicated all of this is - but basically, the air is delivered at the correct pressure when you breathe in; and when you breathe out, those valves close and your exhaled air blows out an outlet valve and bubbles into the water. The design of all of these valves is necessarily complicated to make sure that both the correct pressure is delivered, and that water is unable to flow into the mouth or the air tank. Nimur (talk) 22:46, 24 April 2010 (UTC)

The 'U' in 'SCUBA' stands for "underwater" (Self Contained Underwater Breathing Apparatus) - so the things that firemen wear isn't SCUBA gear. SteveBaker (talk) 01:21, 25 April 2010 (UTC)

muscle fuel

I can start walking any time I want, so there must be some sort of fuel stored in each individual muscle cell, ready to be used any time. I can keep walking for hours at a time, or I can run for ten minutes, before I have to stop. Did the muscle cells start with enough fuel in each one to work for that long, or are they being refuelled through the blood while I'm walking? If they are being refuelled, is there a fuel storage area in my body where I keep the extra fuel after digesting it but before distributing it to a cell? —Preceding unsigned comment added by 99.254.8.208 (talk) 22:18, 23 April 2010 (UTC)

Now that's a good question. Look at Glycogen and Mitochondrion.--Aspro (talk) 22:32, 23 April 2010 (UTC)

Aerobic vs. anaerobic exercise may be helpful as well. Short runs are typically anaerobic sprinting, while long, endured exercise is more commonly aerobic. These are qualitatively different metabolic processes and utilize different biochemistry to release energy. Nimur (talk) 01:55, 24 April 2010 (UTC)

THe only usable form of energy is adenosine triphosphate. Glycogen and glucose only form and reform the hydrogen bond between the last two phosphate ions. 99.13.216.93 (talk) 02:34, 24 April 2010 (UTC)

True, but ATP is the last step in many long processes which produce energy for cells. Its like saying that your lights come on because you flip the switch on the wall, and then ignore the process that got the energy to the switch. ATP is the ultimate source of energy for cells, but the role of substances like Glucose and Glycogen in the transport and storage of energy cannot and should not be understated. --Jayron32 03:17, 24 April 2010 (UTC)

The fuel is glycogen and it's stored in your muscles and liver. So in that case, the fuel storage area will be the liver. Your body refuels its glycogen reserves by converting stored fat in the body. --41.177.6.108 (talk) 09:31, 24 April 2010 (UTC)

Fat is not to any significant extent converted to glucose (which is a necessary intermediate for making glycogen). See Glyconeogenesis, especially the section Entering the pathway. The glycerol part of triglycerides can be converted to glucose, but the fatty acids cannot. --NorwegianBlue ^talk 10:12, 24 April 2010 (UTC)

Yet it seems I can exhaust the supply in the muscles and liver by jogging for an hour, and some refuelling in the form of juice or other sugar is needed for continued exertion. Is it like a car with a very small gas tank? Edison (talk) 03:32, 25 April 2010 (UTC)

I believe your observation is due to the following effect: Fatty acids are broken down through beta oxidation to the two-carbon acetyl-group (in the form of acetyl-CoA), which combines with oxaloacetate, as the first step of the citric acid cycle. Oxaloacetate and the other intermediates of the citric acid cycle are not consumed in the cycle itself, but may be used as fuel through other biochemical pathways. During prolonged excercise, the level of citric acid cycle intermediates decreases (see), leading to less efficient oxidation of acetyl-CoA, and therefore less efficient usage of fat as fuel. Intake of carbohydrates will lead to production of citric acid cycle intermediates, and again allow you to burn fat more efficiently. There may be a bit of OR/speculation in the above, I would have liked to have sourced it better. --NorwegianBlue ^talk 10:49, 25 April 2010 (UTC)