Wikipedia:Reference desk/Archives/Science/2007 November 5

= November 5 =

classic (cliché) explosive detonator?
The popular image of explosive detonation (as seen in innumerable cartoons and Perils-of-Pauline-style movies) involves a box with a T-handled plunger which is forced down to initiate the explosion. (Presumably it was a specialized generator that generated an electric pulse, and fell out of use as compact, reliable batteries became available.) Anybody know what that box was called, or where our article on it is? Neither Plunger nor Detonator yield any clues. —Steve Summit (talk) 01:18, 5 November 2007 (UTC)


 * Answering my own question, a google search suggests it's a "Plunger detonator", indicating that there's at least one thing in this world that Wikipedia doesn't (yet) have an article on, after all... —Steve Summit (talk) 01:25, 5 November 2007 (UTC)


 * I think at least some of those generators were magnetos, but I have no citation and could be wrong.


 * Atlant 17:15, 5 November 2007 (UTC)
 * I've heard that too, and it's also in the Blasting cap article (well, at least being a dynamo of some sort). DMacks 18:18, 5 November 2007 (UTC)
 * Yeah, definitely. I used "generator" loosely, in the sense of "device that converts mechanical to electrical energy". —Steve Summit (talk) 00:41, 6 November 2007 (UTC)

In a number of World War II movies it is depicted that the plunger handle is first rotated (pivoting with its shaft as the axis) with a ratcheting noise, then raised and pushed in. Movies get a lot of things wrong, but this doesn't seem like the sort of thing they'd make up. And I take it to mean that the energy for the generator to generate its pulse comes from the release of a spring, which has to be wound up first. In that case the plunger is merely a trigger. Why use a plunger rather than a pushbutton, if so? Presumably because the long travel of the plunger makes it harder for someone to trigger it by accident. I also note that this type of trigger has a safety advantage over a simple battery system in that there is a separate arming step (winding up the spring).

Or perhaps some plungers would work that way and others would use the plunging action directly to supply the energy. I don't know.

--Anon, 06:06 UTC, November 6, 200... damn! 7!


 * Yes, to differentiate it from others its better known as a 'plunger detonator.' It's mode of operation is that the spring hold the plunger up against the 'shorting link' which guards against induced currents from nearby electric storms and such like from initiating an unscheduled detonation.  Quick depression of the plunger, spins a magneto which charges a capacitor and at the bottom of the stroke, a pair of contacts discharges the stored energy down the wires to the explosive detonator charges. As the magneto has mass, a far mount of force is required to be applied  perpendicular to the base, in order to spin it up from stationary. Therefore, either Colonel Nicholson intentionally fell onto the 'plunger detonator' squarely and thus avoiding it tipping over or Alec Guinness stumbled onto a cheaply made [[Theatrical property|

film prop]] or possibly both. Other types incorporate a crank handle to turn the magneto (like the old telephones one see's in old movies) to charge the capacitor  and separate switches to set the circuit and a button to fire. All done without the need for batteries.--Aspro (talk) 17:32, 6 July 2012 (UTC)

Magnetopneumodynamic Drive?
A Mythbusters episode featured some myths on "Free Energy". Among those debunked was a device called "The Lifter" which seemed to be creating an airflow by electrically charging air and thereby lifting itself. Apart from the debunked myth, could this be the basis of a propulsion system, say for LTA craft? I can't find this aspect covered in the articles on Magnetodynamic drives and I wondered what kind of electric power output would be needed to produce useful thrust. Could any power plant create enough push by this means to move its own mass at a useful speed? 203.21.40.253 03:15, 5 November 2007 (UTC)


 * It's going to have to be about as powerful as a helicopter. It would be hard to charge this amount of air.  The demonstation version of this are very light and have the power source unsupported. Once you build something that can support itslef in thin air, it will be easy to move it by tilting to one side. Graeme Bartlett 03:40, 5 November 2007 (UTC)


 * I believe that Wikipedia has an article on these: Ionocraft. --Carnildo 23:24, 5 November 2007 (UTC)

Thankyou both. I didn't realise "the lifter" was in Wikipedia.203.21.40.253 02:38, 6 November 2007 (UTC)

archeology question about Magan, Sumer's source of copper and diorite
If there are extant copper items from before 2300bc at Ur, could chemistry or nuclear chemistry determine where the ore was mined, provided no mixing of different ores took place in the item?Rich 06:17, 13 November 2006 (UT130.86.14.87 03:35, 5 November 2007 (UTC)Rich 03:37, 5 November 2007 (UTC)
 * You may be able to check for trace elements to get an idea of the ore used. Graeme Bartlett 03:52, 5 November 2007 (UTC)
 * It depends on if the copper has been processed. If it was still in ore, elemental analysis should give pretty strong evidence.  If it has been processed, some sort of isotope analysis might be your only hope, although as Graem says, analysis of trace elements within the copper might help. But processing might change the element ratios.  Although you could always process ore from multiple sources the way you think it was processed in the past and then compare for any differences in isotopes and trace elemental composition (experimental archaeology). That actually sounds like fun to me :) --Bennybp 05:59, 5 November 2007 (UTC)

deoxidizing
how do u deoxidize metals? —Preceding unsigned comment added by 216.103.183.127 (talk) 03:38, 5 November 2007 (UTC)
 * You could use the method of heating the oxide with charcoal, or coal as in steel manufacture. You could use electrolytic methods, as in zinc or aluminium.  On the small scale you may reduce by using a powder of another more electronegative metal, such as aluminium. Graeme Bartlett 03:44, 5 November 2007 (UTC)
 * Of course, you might want to be careful abound that last one, lest you end up with a thermite reaction. shoy  (words words) 14:27, 5 November 2007 (UTC)
 * By the way, "deoxidizing" is usually referred to as reduction. -- 21:08, 5 November 2007 (UTC) —Preceding unsigned comment added by 128.104.112.105 (talk)

How do you control snails in an aquarium ?
Does anyone have suggestions for control of unwanted snail populations in a fresh water aquarium other than chemicals harmful to tropical fish or use of clown loaches, etc. Sugessted to me is the use of aquarium salt which is supposted to be healthy for fresh water fish, but will it control snails in the recommeded concentration suggested for promoting health of fish? This at first seems possibly helpful since we know salt will dry up land snails.74.170.217.65 03:42, 5 November 2007 (UTC)
 * I would not recommend putting any salt in a fresh water aquarium. Just fish out the unwanted snails by hand or in a little strainer, they can't get away very fast. Graeme Bartlett 03:46, 5 November 2007 (UTC)


 * Is it impractical to mechanically sort out and remove the mature snails (several times)? Also, why remove them? We allow a reasonable population of snails to grow in our aquarium in order to keep the glass and plants clean, and the action of the fish eating the snail egg masses seems to keep the population of snails in check.


 * Atlant 17:19, 5 November 2007 (UTC)


 * Google gives plenty of useful-looking hits for aquarium snail control. —Ilmari Karonen (talk) 19:03, 5 November 2007 (UTC)


 * Very large numbers of snails in an aquarium are generally a sign of overfeeding. Feeding only what your fish can eat in a couple of minutes and removing any uneaten food will help keep their numbers in check. Try placing a lettuce leaf or cucmber slice in the tank overnight to attract snails and make it easier to remove them. In general, salt isn't good for freshwater fish, and low levels aren't likely to be effective against snails anyway. --Pseudogastromyzon 16:48, 9 November 2007 (UTC)


 * Would it not be better to look at this WP article and then start planting garlic? Wast not – want not.--Aspro (talk) 17:47, 6 July 2012 (UTC)

question about erotic asphyxiation-a mirror effect?
Since phylogeny can indicate guesses about ontogeny, instead of a bilateral symmetry guess, I want to make a vertical symmetry guess-- Since things in the throat such as the adam's apple get larger at the same time private parts are increasing in size (during puberty), is it possible some of the same or closely related hormones are involved? If so, couldn't whatever structures and types of nerve endings that are responsible for feelings of sexual pleasure exist in the neck region as well as the genital region?Rich 11:02, 25 October 2006 (UTC)--This would not be so different to what can happen to carpal tunnel sufferers (bilateral symmetry here):A person gets carpal tunnel in her right hand from scooping ice cream and decorating cakes at an ice cream parlor, and similar pain and weakness shows up in her left hand, though she hasn't stressed that hand.Rich 03:56, 5 November 2007 (UTC)


 * I don't think this works at all. There is a link between areas of sexual pleasure and position on the cortical homunculus, but this has little or nothing to do with puberty, in which males are affected noticeably by testosterone in areas such as the throat and genitals. The neck is a pleasure area primarily because (or the converse) it is sensitive, like the lips, face, etc. to the touch. It's very difficult to answer the question because it is hard to understand what you are asking, but I think the answer is going to be no. SamuelRiv 01:38, 6 November 2007 (UTC)

Dilmun and Bahrain,Sumer's apparent Garden of Eden-like myth and paradise for Utnapishtim
If it were a paradise for Utnapishtim, I surmise it might have suffered eco damage or at any rate ecological change since. Is there archeological or fossil etc. evidence that the island was previously more lush?Thanks,Rich 20:25, 6 December 2006 (UTC)Rich 04:07, 5 November 2007 (UTC)

decomposing
what happens when a mn oxide decomposes in water? —Preceding unsigned comment added by 216.103.183.127 (talk) 04:31, 5 November 2007 (UTC)
 * Mn oxides tend to go to MnO2 when exposed to water and air. Mn2O7 is a strongly oxidising substance. Graeme Bartlett 04:55, 5 November 2007 (UTC)

bicycle transportation system
I was checking out some proposals for alternative transportation systems and came across this one - BTS's Transglide 2000. Basically, it's an elevated, enclosed tunnel for cyclists, that uses fans and ducts to move air in the direction of travel at speeds about 30 km/h (although it is not actually specified). The point being that this huge reduction in wind resistance will allow riders to travel quite quickly while expending little energy, due to 90% of total resistance being attributable to wind resistance while travelling at 33 km/h. It sounds very interesting but it seems the main issue would be the huge amount of friction between propelled air and the tunnel walls, and the relatively large size of the tunnel and therefore large volume of air, requiring a prohibitively large use of energy (although as a proposal for a mass transportation system this energy usage should correctly be compared to vehicle or rail travel, not to standard bicycle travel). So my question is, can anyone with a good knowledge of mathematics/physics figure out exactly how much friction would play a part in this case? 220.34.254.226 05:22, 5 November 2007 (UTC)The dimensions of the tunnel are about 3.6 m by 4 m.


 * If you have gone all the trouble of building enclosed tunnels around places you might as well build a personal rapid transit system. It would not have any of the problems of the fans, and the rolling resistance is considerably lower, thus uses less energy. The only problem is that it's still "young technology" and the cost of building all the tracks around cities. --antilivedT 07:03, 5 November 2007 (UTC)
 * What's wrong with the idea of climbing into a capsule, pulling a lever and letting air tube conveyor system whisk you right to your desk at the office while you finish putting on your lipstick or brushing your teeth? Dichotomous 19:54, 5 November 2007 (UTC)

Beyond the universe theories.
What are the latest theories as to where outer space, beyond the known universe, leads to, and if it leads to infinity, what is infinity? Can the answers ever be obtained through science and our human senses, or do the answers lie in some other, i.e. spiritual or such, dimensional sense which we currently can't perceive? And are there any recent theories that maybe matter (universe) maybe doesn't really exist, and that reality is actually a concept not created by our human brains, but rather, again, a concept unfathomable by humans who in turn may not actually exist as we perceive ourselves by our "restricted" senses and resources? —Preceding unsigned comment added by 68.10.91.102 (talk) 06:25, 5 November 2007 (UTC)
 * Many of your questions seem to touch on topics that fall under the branch of philosophy called epistemology that aims to answer questions such as "What is knowledge?", "How is knowledge acquired?", and "What do people know?". I think that article and the empiricism article would be good starting points for your further reading in this area. The topic of infinity and whether or not it exists in this universe is covered in physical infinity and Shape of the Universe. Sancho 06:59, 5 November 2007 (UTC)
 * There's also a good course available online for free through MIT OpenCourseWare on the theory of knowledge: Sancho 07:03, 5 November 2007 (UTC)


 * Science can't answer those questions, because it can only study what can be observed and measured; but it can provide some ideas. Here are some that you might enjoy reading about: Multiverse, Many-worlds interpretation, String theory landscape, Chaotic inflation.  These are all ways that our observable universe might be embedded in something larger.  I'm not sure what you mean by the question about the universe not existing; perhaps something like The Matrix?  Religion and philosophy can also provide answers to these questions.  My religion teaches that reality is indeed real, and that the universe was created by a God who exists outside of it and independently of it.  God could be described as infinite in some ways.  In cosmology, the observable universe is finite in size and age, and has a limited life span.  There have been proposals for how to cram an infinite amount of experience into a finite universe (see Omega point (Tipler)), but those have not been widely accepted.  --Reuben 07:20, 5 November 2007 (UTC)


 * There is little if any physical evidence for there being anything "outside" of the universe, so questions about what if anything may lie outside of the universe aren’t solidly within the realm of mainstream science. Science generally only seeks to explain observable phenomena, and the mainstream views of scientists tend to be the simplest possible explanations of those phenomena.  The guiding principle here is Occam's razor, which states that that the simplest possible explanation is the one that’s the most likely to be correct.   A model of reality which includes there being something outside of the universe is more complicated than a model of reality that doesn’t, so an explanation that involves there being something outside of the universe is an explanation to be avoided if possible.  If at some time in the future, some phenomena are observed which are very difficult to explain unless there’s something outside of the universe, then questions about details of the nature of what exists outside the universe could become a solid branch of mainstream science.  There is no way of knowing for sure whether that will happen or not, but the simplest guess (and therefore the guess that according to Occam’s razor is most likely to be correct) is to assume that it won’t.


 * As to whether knowledge about whatever may lie outside of the universe can be achieved spiritually, Occam’s razor says no. There is no good experimental evidence which is simpler to explain by assuming that non-physical "spirits" exist, so the simplest explanation is to assume that spirits don’t exist.


 * As to the possibility that the universe doesn’t really exist, believing in such a possibility isn’t a very scientific outlook. It’s simplest to assume that the universe really does exist, so Occam’s razor says that we should just reject any notion that the universe might not really exist, unless and until there are some observable phenomena which are very difficult to explain without assuming that the universe doesn’t really exist.  MrRedact 09:06, 5 November 2007 (UTC)

May matter (universe) possibly not exist as we perceive it? Matter, dissected to its smallest part, is really energy (matter-atoms-strings ?), which cannot be seen by our human senses. Do humans only "see" this energy in the form of matter because our senses are restricted? Would a more advanced life form see physics more accurately than we, possibly "see" "matter" and universe as energy waves or something more profound? Would a more advanced perceiving life form see the actual meaning of "reality" in a much clearer (spiritual even) light, if, as is almost certain, there are aspects to physics that humans have not yet perceived?


 * Possibly, with consideration of extra dimensions and exotic matter, there could be life that perceives an entirely different (but not unknowable) universe than us. And we don't yet know the mechanism of choice in quantum probabilities, so there might be a world or dimension outside our own that shows a more deterministic scenario. You can speculate forever, but just remember that in this universe, our perception is limited by the nature of matter and energy--to observe, you must disturb--therefore there are fundamental limits to what anything can "know". SamuelRiv 15:24, 5 November 2007 (UTC)


 * I can't quite agree with "matter is really energy," since energy is one property that matter can have, but it doesn't tell the whole story. However, it is certainly true that we don't have an established, fundamental theory of everything.  But I don't think that means that the reality we see is any less real; that would be a sort of hyper-reductionism that needlessly throws away the complex, aggregate nature of things on the large scale.  Ten thousand years ago people could look at a flock of seagulls, without knowing anything about cells, organelles, molecules, atoms, baryons, electrons, quarks, strings, or quantum gravity.  Today we have learned a lot more about those things, but the flock of seagulls is no less real for it.  --Reuben 19:26, 5 November 2007 (UTC)

Could fat cells be originally, very long ago, cancer cells that made a deal?
After all, we now know that chloryphyll made a deal. Many parasites evolve to be less damaging, sometimes even symbiotic. Why not cancer too? The way fat cells are is reminiscent to me of cancer cells.Rich 06:42, 5 November 2007 (UTC)
 * I believe you mean chloroplasts. Incidently, mitochondria are also believed to be derived from captured bacteria-like organisms. However, both organelles have their own DNA and are transmitted as organelles from mother cell to daughter cell. Fat cells are like any other cell in the body and develop from normal stem cell precursors. The answer is no. -- Flyguy649 talk 06:51, 5 November 2007 (UTC)


 * Yeah, I did know about mitochondria. What I was thinking was if bacteria etc get co-opted, which are "foreigners", why can't a "homegrown traitor" or "rebel" like cancer? You can't be saying that cancers haven't ever descended from stem cells?Thanks,Rich 07:01, 6 November 2007 (UTC)
 * Out of curiosity, what about fat cells reminds you of cancer? Someguy1221 07:15, 5 November 2007 (UTC)


 * a lot of things that i've been reading about, some of which i can't remember right now. One thing is how independent they seem. They choose to multiply when they're ready, w/o much control from elsewere. It seems they don't get culled often either.-(What is it called, when the body tells a cell to die?)I have heard fat cells send out "chemical signals" that initiate cancer elsewhere, like "weapons" it still has from an earlier time, and hasn't been disarmed or sufficiently reformed. An animal needs to use fat whether it wants to or not because of what it does--all other animals have it so like in an arm s race, it has to have it as well.Thanks,Rich 07:01, 6 November 2007 (UTC)
 * After chatting a bit, i remeber one big point: Fat is so uncomplicated, maybe the word should be "undifferentiated", like cancer cells. Can we thing of fat as an organ? Not that often I bet. At any rate it's less organlike than most things in an animal's body. Organs like bones sound so incredibly complicated and interact with stuff elsewhere much more than fat does.Rich 07:33, 6 November 2007 (UTC)***Another thing is that fat spreads everywhere, though with preferences-on fingers and toes of those with serious obesity.(Metastasis(or a toned down version of)anyone?)Also, fat cells are such aggressive survivors-you fast and your body, rightly or wrongly, burns muscle almost as much as fat, which suggests that it has a knack for getting an "unfair"(more than its contribution is worth) share of resources. Speculation-when an obese person loses some fat, where does the raging hunger originate-inside the person's brain, or from chemicals sent from fat cells to the brain to manipulate their host?--Thanks for listening, everyone.Rich 06:49, 9 November 2007 (UTC)
 * If there is any link, I'd expect it to be the other way around: perhaps some of the genes that get accidentally turned on when a cell becomes cancerous are normally expressed by fat cells. Or not; this is all just blue-sky speculation.  (By the way, the word you're looking for above is apoptosis or, more generally, programmed cell death.)  —Ilmari Karonen (talk) 19:47, 6 November 2007 (UTC)
 * Thanks for supplying the missing word. But isn't it normal for a cancer cell to express said genes? I need to ponder your suggestion some more, it sounds good, but if fat cells normally express those genes, then wouldn't it be the first way around? And aren't cancers in a sense "normal" as in "pervasive" though bad for us? But I like your speculation since it heads in the direction(at least to me)of: all tissues were originally coopted, subjugated "cancers", fat merely being a badder guy than most. And all these tissues are just waiting for a chance to break free and pursue their narrow short-term self-interest if they can just get some genes turned on-then plenty of division, no apoptosis for them. Like descendants of slime molds someday getting tyranny over constituent players but if the organism lives long enough a rebellion(cancer)is almost certain.(I am sure this is not anything original on my part.)Rich 06:49, 9 November 2007 (UTC)
 * Did someone say midichlorians?  Lanfear's Bane |  t  10:19, 5 November 2007 (UTC)
 * There's an extensive six-part documentary on them. -- Flyguy649 talk 15:28, 5 November 2007 (UTC)
 * Fat or lipid has been an essential part of life for all the living forms, cells use lipids in their cell membrane to create a waterproof partition. So if you want to look for a time without fat in life, it would have to before the appearance of cells. Graeme Bartlett 20:42, 5 November 2007 (UTC)


 * Yes, but I mean about fat cells, not merely lipids. Are fat cells, or some related thing or precursor, ever in plants?  ThanksRich 07:01, 6 November 2007 (UTC)
 * Some plants have oil in them. If you think about all those oil seed crops that you get vegetable oil from, peanuts, palm oil, rape seed, avocado, olives, coconut.  There are even algae that produce oil as a storage, and it is believed that these are the source of petroleum.  These are not a plant cancer, but a way to store energy in a compact way.  Some may use it as a float. Graeme Bartlett 20:48, 6 November 2007 (UTC)
 * If I understand your position then, you are saying that fat cells(as opposed to fats), at any rate, didn't appear until after animals appeared. Earlier I had thought you were indicating that the early origin of lipids precluded, in itself, the possibility that fat cells have a cancerous origin. Regards, 130.86.14.90 06:02, 9 November 2007 (UTC)Rich 06:10, 9 November 2007 (UTC)


 * Also--Surgery is used to remove cancer cells and also to remove fat cells in seriously obese people. I admit that's not a compelling parallel. But if in the future, doctors use chemotherapy and radiation to kill fat cells, then we'll really wonder if there is a connection.Rich 02:31, 15 November 2007 (UTC)

Helicopters in the rain
Moved from the Humanities Desk

What are common effects and problems encoutered by helicopters when flying in the rain and how does it affect the handling? Keria 18:16, 4 November 2007 (UTC)


 * This is not really a question in the area of the Humanities (history, politics, literature, religion, philosophy, law, finance, economics, art, music, and society). A better spot to ask may be the Science section of the Desk. --Lambiam 20:55, 4 November 2007 (UTC)
 * The problem with flying a helicopter in the rain isn't so much the rain itself as the associated conditions. Poor visibility and potentially high and unpredictable winds make such operation dangerous, and most users opt to not fly in such circumstances.  There's not a real concern that rain significantly diminishes the airworthiness of a helicopter, though. &mdash; Lomn 15:08, 5 November 2007 (UTC)
 * Jet engines are also designed to handle high levels of moisture and rain. Dichotomous 19:14, 5 November 2007 (UTC)
 * I think helicopters actually fly better in the rain since the air is usually of higher pressure.--Dacium 03:15, 6 November 2007 (UTC)
 * No, the air is usually of lower pressure. Icek 04:33, 6 November 2007 (UTC)


 * Yet the water turns to super-heat steam thus increasing power and efficiency.--Aspro (talk) 17:50, 6 July 2012 (UTC)

Think mechs will ever be used on the battlefield?
Think they can be practical? I think something smaller like powered armor (which is worn rather than piloted) or a smaller type of mech like the ones from Heavy Gear would work well if they moved as well as humans do. I guess the big advantage of bipedal armor over tanks would be their agility and all terrain movement. If made too big, those advantages would be diminished, but if kept small, they could work. 64.236.121.129 14:48, 5 November 2007 (UTC)


 * According to the dispersion theory of Trevor N. Dupuy in his attempts at quantifying the history of warfare (this guy is my hero of the social sciences), the answer would probably be no. It seems future wars (the theory only works for a total war scenario) require increased dispersion of manpower until battles are won entirely by nontraditional subversive techniques, with traditional manpower kept only to keep a check. That's just my interpretation of an extension where the theory breaks down (it approaches a singularity in the last 50 years with H-bombs and modern smart bombs). And then, of course, any electronic devices are extremely vulnerable to wear and tear and electronic warfare, which makes the high-tech soldier of the future seem very unlikely in my opinion. SamuelRiv 15:17, 5 November 2007 (UTC)
 * Umm, you have to define what you mean by "nontraditional subversive techniques", that doesn't mean much by itself. The "singularity" point is also meaningless. You have to clarify. I'm not sure how PA or small mecha are any more vulnerable to wear and tear than your average tank or vehicle. 64.236.121.129 15:24, 5 November 2007 (UTC)
 * I once read a story (I can't remember the name) about a galactic federation (or whatever) that lost a war because it's weapons were too high tech. -- MKnight  9989  15:32, 5 November 2007 (UTC)
 * What does that have to do with anything? Stay on topic please. 64.236.121.129 15:39, 5 November 2007 (UTC)
 * It goes along with what Samuel said about electronic devices being prone to failure. It's possible I suppose, but it seems like something that complicated would be difficult to 'soldier proof' -- MKnight  9989  15:42, 5 November 2007 (UTC)
 * Yea, I thought I addressed that already. 64.236.121.129 15:47, 5 November 2007 (UTC)
 * MKnight 9989 , you thinking of Star Wars? Ewoks with sticks. Yub yub. AT-ST problems? Get some tree trunks. Yeh, Yeh gira.  Lanfear's Bane  |  t  15:53, 5 November 2007 (UTC)


 * In all fairness, those walkers were crap to begin with. They were too big, and their movement was too static. They used gears and motors for leg movement. That's crap. Yes, they can walk, but they weren't agile, and couldn't move like a human or any other legged animal. Muscles need to be emulated properly in order to take full advantage of legs, and their full range of motion. If they were smaller, and moved like a human or even a horse, they would have been great. The chicken walker leg is also worthless for all terrain movement. 64.236.121.129 16:10, 5 November 2007 (UTC)
 * Yeah I think the All-Terrain was a slight exageration. AT-AT's were more stable (not a horse pun) and they didn't fare much better. Damn Snowspeeders. Rebel Scum are nothing if not innovative.  Lanfear's Bane |  t  16:16, 5 November 2007 (UTC)
 * The story you're thinking of is probably Superiority (short story) by Arthur C. Clarke. Clarityfiend 17:56, 5 November 2007 (UTC)
 * Or The Invincible by Stanisław Lem, one of the best science-fiction novels I have read. Mieciu K 00:34, 9 November 2007 (UTC)
 * The question is what kind of battlefield you are imagining. The late-20th century has not been characterized by wars of high-tech powers against high-tech powers; rather it is generally either high-tech powers against low-tech powers or low-tech powers against low-tech powers, if I can be very, very broad in my strokes. The last real war where all of the major participants were at a similar stage of high military technology was maybe the Korean War, maybe World War II, depending on how you categorize things.
 * In any case, let us think about the advantages and disadvantages of these approaches. Bi-pedal locomotion is indeed able to deal with more terrain, but it is generally much slower than wheeled or tracked locomotion. Personal mechanical armor is probably most effective against small arms fire; large bore fire or heavy explosives of any sort are going to tear limbs off or apply massive concussive force to the interior with great ease.
 * Now if we imagine a future generation of robotics far more advanced than what we have, where we are basically replacing humans with mechanical 'droids, then I could definitely see that as a political advantage although I am not sure about its military advantage. An army in which no soldiers have to die is one that can be deployed with far less problem of home-field protest, although the cost differential is going to be pretty unpleasant versus training a soldier and deploying a high-tech robot. But cost-differentials, of course, are not taken into much account even today—when we reply to car bombs with cruise missiles, we are spending billions of dollars to reply to a weapon that cost at most a few thousands dollars, at least almost nothing (here I am thinking of the African embassy bombings of the late 1990s which were replied to with about $2 billion worth of cruise missiles).
 * Anyway, just some things to think about. Is it possible? Maybe. But remember that we're probably not going to see two very high-tech superpowers go head-to-head anytime soon. So who is going to buy these robots, and who is going to deploy them, and where? The US already has high tech weapons it can't really use effectively; at the moment "mechs" strike me as not being terribly desirable for modern warfare. --24.147.86.187 15:53, 5 November 2007 (UTC)
 * Aren't the US already using guns mounted on tank-type tracks which are armor plated and remote controled in Irak? 80.200.238.237 16:36, 5 November 2007 (UTC)
 * I am not sure, but in the Misc. desk recently we were discussing motion sickness et al and someone mentioned that soldiers remote operating from a trailing vehicle quite often felt ill due to the different sensory inputs . And K and use a Q 80.200 boy.  Lanfear's Bane |  t  16:45, 5 November 2007 (UTC)
 * You also have to look at the issue from the logistics side of things. Tanks are relatively short in stature (M1A2 Abrams), whereas I'm a 'mech' would have to be relatively tall to be effective, making it more difficult to transport and deploy. -- MKnight  9989  13:12, 6 November 2007 (UTC)
 * Wow, it's so hard to talk to people who don't read your posts. Read my first post then realize why your post is irrelevant. I hate repeating myself 50 billion times. 64.236.121.129 14:59, 6 November 2007 (UTC)
 * I'm curious to see what advantages you think a mech would have over modern equipment, such as tanks. The army has been experimenting with powered armor, or at least researching it.  I think that would be much more feasible then a mecha for a number of reasons.  Your question is, are mecha practical.  I think the answer is no, because the potential advantages do not outweigh the certain costs and pitfalls.  Again, I would love your feedback as to what, exactly you think would be better about a mecha as opposed to a tank, or a soldier in combat armor. dcole 13:44, 8 November 2007 (UTC)

theoretical yield
How do I figure out the theoretical yield of a substance? -- MKnight  9989  15:10, 5 November 2007 (UTC)


 * Sounds like homework. Here's a hint: think about how much reactant you need, and how much you have, and try to maximize the amount you can get from your reaction equation. In short, multiply both sides. SamuelRiv 15:19, 5 November 2007 (UTC)
 * I know how much reactant I have and how much product I end up with (actual yield), but I don't understand what calculations relate the two to theoretical yeild. -- MKnight  9989  15:37, 5 November 2007 (UTC)


 * Theoretical yield is how much you get if everything go perfectly, everything reacts, and reacts the way it's supposed to (Yield (chemistry)). Someguy1221 16:22, 5 November 2007 (UTC)

Amazing little horned garden spider


What kind of amazing little horned spider is this? Found it. Spiny orb-weaver

In addition to its horns its web has UV reflective tuffs and its web is attached to Earth at three points:


 * 1) branch of tree; 12 feet from ground,
 * 2) middle rail of fence; 2 feet sideways and 3.5 feet from ground,
 * 3) near end of stacked pipe; 10 feet from attachment point 1 and 7 feet from attachment point 2.

Attachments are anchored at each point by 2 to 5 strands. Orb is only 9 inches in diameter.

Second question... How did this little spider reach these three different attachment points? I can see maybe wind to the tree branch and to one of the other attachment points but what about the 3rd? Did the spider crawl all the way back up the tree branch after the first attachment and then go for the second, or what?

Dichotomous 15:51, 5 November 2007 (UTC)
 * I'd love to see an insect-person to back this up, but I had heard that they throw some silk into the air, and just hope it grabs on to somewhere useful. --Mdwyer 22:02, 5 November 2007 (UTC)


 * Spider silk is extremely thin, and thus has high wind-resistance (compared to its mass). That would make throwing silk an unlikely scenario for long distances, as it would slow down incredibly fast. It would also make it hang at very opposite of steep angle, so it could conceivably just get two threads grounded, then suspend itself on a piece of silk and get blown to the side. This is all speculation, though. — Daniel 01:59, 6 November 2007 (UTC)
 * From the spider web article: "The spider effectively utilizes the wind to carry its initial adhesive thread. With some luck the silk is released from its spinners and carried by the wind to a suitable adherable surface. When it sticks to a surface the spider will carefully walk over the thread and strengthen it with a second thread." -- MacAddct &#xF8FF; 1984 (talk &#149; contribs) 05:56, 6 November 2007 (UTC)

Which is the best alternative to gasoline for cars, hypothetically
I don't mean right now, but in the future. From what I read of the articles, I think battery-electric cars potentially are the best. They have the best efficiency when you think of it from taking energy from a nuclear powerplant, then shooting that energy into a battery. Stuff like hydrogen, requires making hydrogen which is inefficient.

In terms of using that energy, I read that battery electric cars are equivilant to say 100-200 miles per gallon, if do all the conversions and compare them to ICE cars.

They don't use any explosive liquid like hydrogen or gasoline, although the batteries can explode possibly... Still, I think they are safer.

Batteries can have good performance, 0-60 in 4 seconds, top speeds of over 200 miles per hour. I'm sure these stats can improve in time too. Range right now is a problem I think though. 200-300 miles is the best ranges I heard for some good Bat cars. ICE cars tend to have a range of 400 miles on a full tank of gas. I think with improvements in batteries, Bat cars can be extended to 400 miles though.

Bat cars are quiet.

Bat cars release no emmisions.

Bat cars benefit from regenerative braking.

Maybe the only negatives would be, they are harder to repair (but I think that has more to do with stupid mechanics who are only knowledgable on ICE cars), more expensive (although in the long run, it'll be less expensive, and ICE cars perform better in extreme temperatures like extreme hot or cold.

What do you peeps think of my assessments? 64.236.121.129 16:06, 5 November 2007 (UTC)


 * ...and just how did you come to these assessments? Dichotomous 16:12, 5 November 2007 (UTC)
 * From the articles dude. 64.236.121.129 16:16, 5 November 2007 (UTC)
 * dude...? Dichotomous 17:29, 5 November 2007 (UTC)
 * "some good Bat cars.". See Batmobile.  Lanfear's Bane |  t  16:18, 5 November 2007 (UTC)
 * peeps...  Clem   16:26, 5 November 2007 (UTC)


 * Quick thoughts: I don't think the inefficiency of making hydrogen is a big deal if you're supposing widespread clean nuclear power. I find it a more relevant objection if you're burning tons of dirty fuels to manufacture clean fuels.  Quiet (to the degree of electrics) is a debateable benefit.  The hearing-impaired community is already concerned by Priuses and the like, and I feel that modern cars are quite capable of being generally quiet so long as their owners don't modify them to be noisy.  Emissions are no more a concern with hydrogen than electric, and any hybrid system benefits from regenerative braking, too.  Finally, your discussion about range omits a key point.  A tank-fueled car, regardless of single-tank range, can just refuel in five minutes.  An electric car cannot.  Consequently, "range" means entirely different things for the two car types.  &mdash; Lomn 17:01, 5 November 2007 (UTC)


 * Why waste energy with inefficiencies? Why bother when there is a more efficient alternative? You're just wasting energy that could be used otherwise. Quiet is just a nice bi-product. I don't think we are going to go out of our way to make noisy cars just for the hearing-impaired, that's just silly. What would be the point anyway? They want loud cars so they can hear them? That's stupid. Yes, modern cars can be quiet, but they also use gasoline, which is the problem isn't it? Remember what we are talking about dude. Yep, hydrogen produces no harmful emissions, but they are worse because of the inefficiencies I mentioned before remember? They also require platinum in their engines, which drives up the price, and makes increases the demand for platinum, thus raising its price. Such a scenario can be avoided with batteries. Yep, any hybrid can benefit from regenerative braking, but so far all of your points merely match the capabilities of a Bat car, rather than exceeding them. That's what we are talking about here, the best of the alternatives.


 * Recharge times are gradually improving, with some rechargers capable of recharging spent batteries in minutes. But there are also ways around that like recharging over night at home while you are sleeping, or having recharge stations at offices. If all you do with your car is drive to work, and it's a reasonable distance, you can just recharge at home overnight. But yes, recharge time is an issue, but it's an issue that can be improved. 64.236.121.129 18:11, 5 November 2007 (UTC)


 * The question of inefficiency is "does the inefficiency matter?" If you're assuming widespread clean nuclear power, then my answer is "no".  I think, given that supposition, hydrogen is a perfectly viable fuel and far easier to engineer than superquickcharge batteries.  If battery charge times are on par with other refuel times, then sure, it's a great solution -- I'm just not prepared to make that leap.  You're dead-on with overnight chargers being adequate for the vast majority of car use, but I find the idea of a car that does what I need 95% of the time but cannot do what I need for the other 5% (e.g. long range driving) to be an unacceptable car. Additionally, there's the problem of battery space and weight with pure-battery cars; hybrids are significantly more efficient in those terms.  As for my points matching those of battery cars, yes.  That was exactly my point -- to note that a battery-only car does not hold exclusive advantages in those regards.  &mdash; Lomn 18:23, 5 November 2007 (UTC)


 * Two things, we don't have widespread clean nuclear power, so we still have to be realistic about where our energy is coming from. And second, even if we did, it's still a waste of energy, so why bother waste it with inefficiencies when hydrogen cars do not have any benefits over Bat cars? You are making a really big assumption when you say hydrogen is a viable fuel and far easier to engineer than batteries. You gotta back that up. Otherwise that's just a blank, meaningless statement.


 * Battery space and weight doesn't matter if the performance numbers are still good. The numbers I gave before are for real Bat cars. Hybrids are significantly more efficient in those terms you say? What the hell does that mean? You gotta clarify your points dude. You are making a lot of blank, empty statements that don't really mean anything.


 * Yep, but I never said bat cars hold exclusive to those advantages did I? So you are arguing a strawman here. What I'm looking for is, what do the other ICE alternatives have over Bat cars, if anything. The recharge issue seems to be the only thing you can think of, but that's already being addressed. 64.236.121.129 18:36, 5 November 2007 (UTC)
 * Re: space/weight: have you ever seen how little cargo space remains in an all-electric car? It's preposterous!  Hybrids require a far smaller battery pack; thus, they are more efficient in that regard.  Aside from that, this looks like another case of you expecting to have your assumptions parroted back to you.  A nuclear electricity source (which you originally suggested) is too-forward-thinking, a lack of quick-recharge isn't forward-thinking enough, even though it's already "being addressed" -- whatever that means....
 * Clearly there's no legitimate request for commentary or criticism here. &mdash; Lomn 19:09, 5 November 2007 (UTC)


 * Hmm, what kind of cargo do you want to haul exactly? I don't think the average person needs to haul much stuff usually. I'm mostly talking about transporting people, and most people just use their car to get to work. Fair enough, a hybrid might carry more cargo, but that's it really. Aww, you're mad again. Well that's your option ^^. 64.236.121.129 19:34, 5 November 2007 (UTC)


 * I drive a MINI Cooper - for a while it was the smallest car you could buy in the USA. People continually ask me how I manage without the storage space.  I point out that the volume of the trunk is about 20% bigger than a large-sized Kroger shopping cart - I measured it to be sure.  So when you go to the store - if it fits in the cart, it'll fit in the trunk. Then of course you can fold down the back seats and get tons more space.  I think people always assume they need vastly more space than they actually do.  The times when difficulties arise are when I need to buy an awful lot of wood from the DIY store - or take the entire family on a camping trip.  But ask yourself just how often you ACTUALLY do that.  I reckon 10 times a year...tops.  So I rent a larger car from Hertz - or I make use the honking great truck that Home Depot will rent you for $18 for a couple of hours if you spend $50 or more at their store.  Yeah, this costs money - but the fact that my car is using half the amount of gas on the other 355 days of the year totally annihilates any consideration of that.  Lots of people I know with two kids have a 7 seat SUV.  When I ask why, they claim to have to transport the kid's friends on occasions...OK...but you own two cars - take both of them!  Again, there are plenty of creative ways to handle the RARE occasions where you need more than 4 seats and more than a shopping-cart-worth of luggage space.  The more people who did this, the cheaper it would be to rent bigger vehicles when you needed them.  Something like the Zipcar approach is what we need here.  A group of 100 families living in the same neighbourhood could comfortably share the ownership, maintenance and depreciation of (say) a half a dozen SUV's and half a dozen pickup trucks - and have each family own their own dinky little SmartCars and MINI's for commuting and light shopping trips. SteveBaker 04:21, 7 November 2007 (UTC)


 * Since you asked for a hypothetical future solution, I vote for a very small fusion reactor driving a Sterling engine driving an electric generator, in turn driving one electric motor per wheel, with supercapacitor buffering to account for peak accelleration and regenerative braking. No pollution except for heat, and no need to refuel for the life of the car, service interval limited by wear on the tires. -Arch dude 17:45, 5 November 2007 (UTC)


 * I'm assuming you are being facetious, but I'll address it anyway. Too expensive, and we also don't have practical, working fusion reactors, let alone one small enough to fit in a car. This is something that might happen in 1000 years, rather than the foreseeable future. 64.236.121.129 18:11, 5 November 2007 (UTC)


 * Too expensive? My hypothetical micro-fusion reactors can be had 3 for a dollar at Sam's Imaginary Energy Emporium.  On a more serious note, if we did have practically limitless, cheap, clean energy, there are many other technologies and products that would suddenly become very cheap as well.  Dragons flight 19:06, 5 November 2007 (UTC)


 * Yea, but who's talking about limitless energy? We are talking about alternative power sources for cars. 64.236.121.129 19:34, 5 November 2007 (UTC)


 * Some work is being done to breed organisms that can ferment an entire maize plant into ethanol, instead of just the kernels. That could make ethanol much more attractive than it is today. --Gerry Ashton 22:25, 5 November 2007 (UTC)


 * Nuclear fusion is far from being a clean or safe energy source anyway. It may be a bit cleaner and safer than fission, but it's still not something you want in your car. One of the arguments against Pons and Fleischmann's claims of cold fusion was that if it had really been fusion they'd both have been killed. -- BenRG 17:16, 6 November 2007 (UTC)


 * Going back to the original question, do you (64.236.121.129) want to back up those two assertions "batteries have the best efficiency" and "making hydrogen is inefficient"?
 * Batteries are horribly inefficient. They're heavy, they take time to charge, they're limited in their discharge rate, and they have a finite number of charge/discharge cycles.  Also they can be dangerous, can require large amounts of energy and toxic chemicals to manufacture, and can be difficult to dispose of.
 * Even if you assume a perfect battery, charging it with plant-generated electricity and then discharging it in an electric car is precisely as efficient as manufacturing hydrogen using plant-generated electricity and then burning it in a hydrogen-fueled car. If the batteries are anything less than 100% perfect, hydrogen is more efficient, not less. —Steve Summit (talk) 03:12, 6 November 2007 (UTC)


 * Uhh no, I don't wana back up those assertions because I'm not having a debate. I just wana know what people think is the best alternative to ICE cars. I'm just going on what the article on bat cars says. It said that bat cars are far more efficient than hydrogen cars when you take into account the inefficient process of making hydrogen.


 * Those are some fair points, but you need to clarify a few things. Yes they are heavy, but how does their total weight compare to an ICE engine or Hydrogen engine? I'm assuming they are all quite heavy. Charge time is certainly an issue, but some of the newer bat cars have very good charge time. What do you mean by "discharge rate", I don't understand that. Yes, charge/discharge cycles can be an issue, but I heard that this can be solved simply by leasing the batteries rather than selling them. You simply return them for new ones, once they run dead.


 * Huh. That's not what the article on bat cars says. It says the process of making hydrogen is less efficient. Read the article then get back to me. 64.236.121.129 14:56, 6 November 2007 (UTC)


 * Sorry, which article? —Steve Summit (talk) 19:40, 6 November 2007 (UTC)


 * Exactly. You have to remember that the electricity to charge these battery powered vehicles has to come from somewhere.  If you cut all of the pollution from cars, but end up making even more pollution at the power plants you'd need to power all those cars, you're actually worse off in the end, not better.  Keep in mind that you're wasting the power that is lost in an inefficient conversion from fuel to electricity, during transmission, electricity to battery, during storage, and battery back to electricity.  Unfortunately, going directly from gasoline is currently much more efficient.  Hopefully battery research will help solve this problem, but progress in this field tends to be quite slow.  Keep in mind that the batteries themselves pose pollution risks, and need to be disposed of properly as well.  You have to look at the whole process from start to finish to determine what pollutes less.  The "best" alternative to cars depends on the situation, but walking or taking a bike are both good alternatives in some cases. --  Hi  Ev  04:01, 6 November 2007 (UTC)


 * Hmm, not all power plants pollute. Nuclear power for example. Yes we use mostly coal right now, but at least the possibility exists for clean alternatives that provide vast amounts of power. Huh? That contradicts what the article on bat cars says dude. The article says that bat cars are much more efficient. Didn't you bother to read it? It says that the process of sending energy into the battery is about 80% efficient. Then from there, the use of that energy is equivilant to about 100-200 miles per gallon. That's what the article says dude. Don't blame me, blame the article if it's wrong. Batteries can be recycled though.


 * I think that this discussion is turning into an attack on bat cars which is not what I intended. I was asking what do the other ICE car alternatives have over bat cars. This, first and foremost, is what I'm interested in. 64.236.121.129 14:56, 6 November 2007 (UTC)


 * No, "the article" (by which I'm assuming you mean battery electric vehicle) says that almost half the energy is lost simply due to inefficiencies in battery charging, and I don't see it claiming it's "80% efficient" anywhere (which would contradict the part I just pointed out.) The article does not include the efficiency of the original creation of that electricity nor the loss during transmission either.  Coal is normally converted into power at about 36-38% efficiency (see here), about 7.2-7.4% of that is lost in transmission (see here), and half of that is lost in charging, which (if I calculated it correctly) means you're at about 17.15% fuel efficiency at that point.  Gasoline engines have about 30% efficiency and diesel engines have about 45% efficiency (see here).  The efficiency of BEVs is much higher than gasoline or diesel if you ignore the initial loss at the power plant and in transmission, but I don't think that's a fair comparison because it basically assumes the electricity is created with 100% efficiency.  So, in terms of fuel efficiency, which is what I was talking about, diesel wins by a wide margin.  However, coal/electricity is much cheaper than gasoline currently, so a BEV is more efficient economically speaking, in terms of miles per currency unit.  But remember supply and demand, if everyone switches to BEVs, power demand will go up, and electricity cost will most likely to go up with it (probably driving down gasoline costs as well.)  Also, that does not include the added initial expense of buying a BEV vs. a gasoline/diesel vehicle, so it might take a while before you reap any economic benefits.  In the end, I guess it all depends on what kind of efficiency you're talking about and how you calculate it.  (Note: I have a nagging suspicion that I made an error somewhere in this, but I just can't put my finger on what it is.) --  Hi  Ev  22:43, 6 November 2007 (UTC)


 * We're not "attacking" battery-powered cars; we're just issuing a few sober pronouncements on their imperfections. This is the Science desk, and we have to treat things as they are, based on logic and evidence, not on how we wish they were or what sounds nice, based on emotions.
 * The big problem is -- and I'm speaking here as a scientist, not a Detroit-apologist -- is that from most standpoints, cars powered by internal-combustion engines fueled by liquid hydrocarbons are extremely good. The energy density of gasoline is extremely high, the engines can be built compactly and cheaply, and the fuel is just sitting there in the ground (so to speak).
 * There's a reason we're all driving gasoline-powered cars, and it's not some kind of shady conspiracy. It's simple scientific and economic fact.
 * So when you ask, "what do the other internal-combustion alternatives have over battery-powered cars", there are two problems with the question: (1) there aren't really any other alternatives, and (2) in most respects, the battery-powered cars don't have anything over the internal-combustion ones, either. We can't agree with you that batteries are the best alternative to gasoline, because they aren't a very good alternative.  We can't tell you what we like better, because there isn't anything better.
 * (Now, before seventeen rabid environmentalists descend en masse and rip me a new one for daring to suggest that gasoline-powered cars are "good", hold on. Don't get me wrong; I'm a rabid environmentalist, too.  Of course I understand that sucking that nice energy-dense liquid fuel up out of the ground isn't sustainable.  Of course I understand that the emissions are ruinous.  But I also understand that providing individualized transportation any other way is a really, really hard problem.  Just having every driver on the planet buy a Prius or an EV1 ain't gonna solve it.  An earthshaking revolution in the energy density, rechargeability, and weight of batteries would help solve it, and I'm hoping for that revolution, too, but I'm not sure we can count on it.) —Steve Summit (talk) 02:53, 7 November 2007 (UTC)


 * The problem with the future of cars is how to get there from here. Electric cars could work if we had a non-polluting source of electricity with enough capacity - but we don't - yet.  Even if we did have enough solar/wind/tide/hydro/nuclear power, we have a problem with the technology.  We can't cram enough batteries into a car to make it go far enough between recharges - and recharging takes FAR too long.


 * However, problems of range could be solved if we wanted to. Batteries could be mounted on a little cart that you pulled out from the back of the car and exchanged for a fully charged set at battery exchange garages along the side of the road.  Every couple of hundred miles, you'd pull into a battery station - pull a lever to drop the battery cart out onto it's little wheels, pull it over to the attendant who would swap your dead batteries for a freshly charged set and charge you whatever the going rate is.  The battery packs would belong to some national chain who would have stacks and stacks of them 'out back' recharging.  Having to 'refill your batteries' would take about the same time as filling up your gas tank and you'd have a similar range between stops.   But until such things exist, we can't do that - and until we do that, such things can't (economically) exist.  So (annoyingly) that won't work.  Similar problems exist with hydrogen powered cars.  So that won't happen either.


 * Reluctantly, I think plant-based ethanol is the way forward. It uses all of our existing technology - the same gas stations, most of the same cars - it's even been proven on a large scale in Brazil and it definitely works.  The only problem is that we're using corn to make the Ethanol with and that's a REALLY stupid idea brought about by US politics and the farming lobby.  We need to use more efficient plants - that we can use nearly 100% of the plant to do the production with.  There are promising kinds of plants but because all of the research money is going into corn-based ethanol, that's not going to work either.  Heck we've even raised tariffs to prevent the more efficient sugar-cane-based ethanol from being imported!  Anyway if we can use the right plant, this is a carbon-neutral way forward that fits with the distribution networks we have.


 * Mostly what we need is more efficient cars. My car is not a hybrid - it's a MINI Cooper - and it gets 40 miles per gallon - it's fast and it's comfortable and it's fun to drive and it'll go 140mph.  The new version does even better MPG because it does the 'stopping the engine when at a stop light' thing.  The next generation after that gets a form of regenerative braking where the initial accelleration of the car from a stop is driven by the starter motor until the energy stored from braking is used up and the main gas engine starts - that'll get you 50 to 60mpg in city driving without messing around with batteries and hybrids and such.  We need to get rid of the 20mpg cars and trucks that are being driven by commuters - that's just insane.  If everyone who drives a 20mpg car were to buy a 40mpg car the next time they buy something new, we'd have HALVED the problem of automotive pollution within 5 years.  Instead, we have new "Hybrid technology" SUV's and trucks that claim 26mpg...geez...well, that helped a lot!


 * SteveBaker 18:27, 6 November 2007 (UTC)

So did anyone ever figure out which article 64.236.121.129 was talking about that alleged that "the process of making hydrogen is less efficient"? —Steve Summit (talk) 21:18, 7 November 2007 (UTC)


 * thumb

Well, you did say hypothetically speaking... --Aspro (talk) 18:05, 6 July 2012 (UTC)
 * Non polluting
 * Quiet
 * Totally recyclable

Stiff neck
Is it possible to insert structures into the neck to prevent strangulation? Has it been done before? 81.242.90.27 17:42, 5 November 2007 (UTC)


 * I don't know, but wouldn't it be easier just to wear a suit of powered armor if it's such an issue? 64.236.121.129 18:41, 5 November 2007 (UTC)
 * Oh. Then no-one wouold try to strangle you. It's for James Bond. 80.200.239.55 19:35, 5 November 2007 (UTC)
 * Slightly off topic, but we did exercises in Kung Fu to strengthen the neck muscles (neck turning I believe it was called). The instructors showed that with enough practice it works against a lot of choking techniques, and you can even take punches/strikes there. And no surgery required! There are some movies of monks putting ropes around their necks and just hanging there.  It takes a while though; I never got that far. --Bennybp 21:00, 5 November 2007 (UTC)
 * It is a common movie plot device to wear some sort of device to fake a hanging. The problem is that in most hangings, the cause of death is a broken spine -- not strangulation. --Mdwyer 22:00, 5 November 2007 (UTC)
 * No, that's not correct. The way a broken neck kills you is through asphyxia (there's no way for the "breathe" signals to get from your brain to your lungs). But when you're hanged, even if the signals could get through, it wouldn't help you, because the blood can't leave your brain, so there's no room for oxygenated blood to come in and replace it.
 * Hanging is quite a horrific way to die. People have this notion that as soon as the neck breaks the victim is unconscious, but there's simply no good reason to believe that. All it does is prevent him from jerking around and alerting the onlookers to his suffering. --Trovatore 22:07, 5 November 2007 (UTC)
 * They'd still be able to move their head, wouldn't they? I've heard beheaded people could, but I haven't seen either. Also, it's still probably better than cancer, as it's much, much shorter. — Daniel 01:46, 6 November 2007 (UTC)
 * After having my carotid artery accidentally blocked in a judo match a few years ago (very very briefly), I assure you that the cessation of blood flow to the brain knocks you out essentially instantaneously. Albert Pierrepoint mentioned in his memoirs (very good read) that the pulse stops immediately after a long drop hanging, and I'd take his word over most laymen. Of course, the American tradition of strangulation hanging is another story. GeeJo (t)⁄(c) &bull; 15:59, 6 November 2007 (UTC)

about IR
what is the infrared absorption frequency of phosphorous-oxygen bonds? —Preceding unsigned comment added by Dinkysweet (talk • contribs) 17:45, 5 November 2007 (UTC)

Depends single vs double, ionic vs covalent ("what's attached to the O if it's single-bonded to P"), etc. DMacks 18:08, 5 November 2007 (UTC)

is the california fire still burning?
California_wildfires_of_October_2007 could use an update —Preceding unsigned comment added by 85.238.88.73 (talk) 18:03, 5 November 2007 (UTC)
 * I believe technically some remnants are still burning. As of today, the state of California said the fires were "under control".
 * Reference:
 * I have updated the article accordingly. Johntex\talk 20:55, 6 November 2007 (UTC)

Down insulation
A friend of mine is an avid & experienced outdoorsperson, and tells me that it's widely known that down jackets or vests should be worn under other layers, because "down's insulating power comes from the temperature difference between heat of your body and the outside cold". In other words, she says that if you wore wool or synthetics under down, you would be colder than vice versa, because the down won't insulate if it's cold. It's possible that I'm not representing her explanation fairly.

I have a basic understanding of thermodynamics, and this doesn't make much sense to me. Her explanation of down's special properties sound like a definition of insulation in general. It seems like the delta-T across the down will determine its insulating power, whether that temperature difference is between skin and an inner shell, or between air and a underlayer. Can anyone explain this apparent discrepancy?

Secondly, according to our article, down insulates more poorly when moist or compressed, wouldn't you want it further away from your perspiring body, and uncompressed by outer layers? jeﬀjon 18:33, 5 November 2007 (UTC)
 * I think you are right. The insulation should be just as effective as the outer layer and this may even be preferred due to the lack of compression.  I think if you go to a sporting-goods / camping store, you will see that most of the down-insulated garments are designed for outer-wear. They are too bulky to go under other layers, in general. Johntex\talk 20:37, 6 November 2007 (UTC)

How do I tell white gold or platinum jewelry from stainless steel?
How do I tell white gold or platinum jewelry from stainless steel? If I have some jewelry, don't know where it came from, and think it could be made of either one of these three, how do I find out which one? I mean aside from some really complicated thing at the chemist. William Ortiz 18:41, 5 November 2007 (UTC)


 * An easy first step: some types of stainless steel are magnetic, so if a magnet is attracted to it, it definitely isn't gold or platinum. If the magnet isn't attracted, though, you haven't proved anything. jeﬀjon 18:44, 5 November 2007 (UTC)

Maybe if you live in an area where there are stereotypically gold-hungry ethnicities, you could dangle it conspicuously and see if they have gold-lust in their eyes. Note: I'm basing this on myself, since I belong to such an ethnicity. My eyes not only twinkle, but get a little teary. —Preceding unsigned comment added by 85.238.88.73 (talk) 19:10, 5 November 2007 (UTC)
 * Most gold jewelry has the karat written on it somewhere (ie 14K, 18K, 10K, etc.).Josborne2382 19:17, 5 November 2007 (UTC)

Like the apocryphal story of Archimedes and the crown, you can determine the density of the material using the item's weight and volume. The weight is easy, if you have an accurate enough scale. The volume can be determined by immersion in water, but it might be tricky if the item is small. -- Coneslayer 20:40, 5 November 2007 (UTC)


 * A sufficiently clever counterfeiter could use a metal heavier than gold and leave a hollow space to fool the density test, so you'll also want to measure its moment of inertia ;-) Someguy1221 22:06, 5 November 2007 (UTC)


 * A clever counterfeiter uses tungsten which has nearly the same density as gold. Icek 04:24, 6 November 2007 (UTC)

Would stainless steel have "stainless steel" or some variant written on it? Would platinum jewelry? Does platinum jewelry have karats or something similar? William Ortiz 21:49, 5 November 2007 (UTC)

Why don't you just take it to a jeweller and ask his/her opinion? Exxolon 21:54, 5 November 2007 (UTC)


 * If it dissolves in mercury, it was gold; if it dissolves in hydrochloric acid, it was steel; if it catalyzes hydrogenation of olefins, it's platinum? Alternately, there are various more formal metallurgical tests. Various spectroscopic techniques could work too. Depends how much you have and how destructively you're willing to test it. DMacks 23:11, 5 November 2007 (UTC)

Auger electron spectroscopy could answer the question.

Atlant 00:28, 6 November 2007 (UTC)


 * This alone will only tell you about the composition of the surface (about 1 nm depth). Icek 04:24, 6 November 2007 (UTC)

I have stainless steel silverware and that stuff is not magnetic. I hear stainless steel jewelry is made from Surgical stainless steel -- is that magnetic? William Ortiz 10:49, 6 November 2007 (UTC)
 * According to my nipple, no it is not magnetic (within my ability to notice a force with a couple of nice little Nd magnets). Also according to my piercer, though I still avoid certain fun toys. Eldereft 20:30, 7 November 2007 (UTC)

Maybe I'm missing something obvious, but it seems to me that the easiest way to tell whether what you have is stainless steel or platinum/gold, etc. is the radically different hardnesses. Most steel (stainless or not) will be far harder than gold, silver, platinum, etc. Matt Deres 18:59, 9 November 2007 (UTC)


 * Platinum is fairly hard. And of course most jewelery is made from alloys, complicating things somewhat. Pragmatically, most precious metal pieces will carry mark describing the precious metal content - if you don't know how to read it, a good jeweler will. This will probably be faster, cheaper, and less destructive than most experiments. --Stephan Schulz 00:19, 12 November 2007 (UTC)


 * If you heat stainless and platinum up to dull red then let it cool, stainless will leave an oxide discolouration, platinum wont. (if it is a ring -take it off your finger before doing this).--Aspro (talk) 18:14, 6 July 2012 (UTC)

Oil consumption versus oil creation
Where can I find a graph or chart that compares the consumption of crude oil with crude oil creation. I would expect it to be on the order of like a barrel of crude every ten years versus however many million or billion consumed per day. Dichotomous 19:05, 5 November 2007 (UTC)
 * Consumption of petroleum (also known as crude oil) is currently about 84 million barrels per day. The current creation of petroleum is almost certainly much faster than a barrel every ten years.  A barrel of petroleum created every ten years since the origin of life on this planet about 3.5 billion years ago would only come to about 350 million barrels.  But petroleum reserves, not counting oil sands, are currently at about 1.2 trillion barrels.  Dividing 1.2 trillion barrels by 3.5 billion years puts a worst-case lower bound of a least a barrel created per day, and probably considerably more.


 * It'd be very difficult to have a bar chart showing how petroleum creation compares to petroleum consumption. If the bar showing petroleum consumption is a few inches tall, the bar showing petroleum creation would have to be thinner than the thinnest line that a printer can print.  MrRedact 20:09, 5 November 2007 (UTC)


 * I don't think we honestly know what the rate of creation is. A reasonable guess might be something like:


 * C = A / Y
 * Where:
 * C = The creation rate.
 * A = The amount of oil that had formed before we started digging it up.
 * Y = The number of years it took to form.


 * We know that oil is formed from the simplest algea in the ocean - which have been down there (presumably) forming the stuff for 3 billion years - so Y=3,000,000,000 years.  I think it's fair to say that there were once about 3 trillion barrels of economically usable oil (ie not mixed up with sand and oil shales and such) and about twice that amount if we include the (currently) uneconomic stuff so A=3,000,000,000,000 barrels.


 * That says that it's probably forming at a rate of C = 3 trillion barrels / 3 billion years = 1,000 barrels per year - let's say 3 barrels per day of economically usable oil (perhaps 6 barrels per day that of the other stuff). We're currently using close to 90 million barrels a day.  Which means we're using it up about 30 million times faster than it's forming.  (Jeez! Even I'm surprised by that number!)


 * Of course this makes two very dangerous assumptions - one is that every drop that was ever formed was available for us to dig up. That's unlikely because much of it must have been subducted due to continental drift and such.  So that would make the estimate for present production rates higher than I just calculated - perhaps if we're really optimistic, 1,000 times faster.  On the other hand, I'm also assuming that conditions have always been right for oil formation - and indeed that the conditions are still right.  That's also a difficult thing to know and could push my estimate either up or down - but not by very much compared to thirty million!


 * But one thing is for absolute certain - we're using the stuff up at a rate at least a few thousand times faster than it's being created - and perhaps a millions of times faster. Fast enough that it's irrelevent that more is being formed.  3 barrels a day isn't enough for anything useful!


 * Even if I'm wildly off the mark. Suppose we were using it up only ten times faster than it's being formed, we'd still run out in roughly the same amount of time!   But that simply can't be true.  Nobody is going to claim that all this oil we dug up last year is only 100 years or so old (we'd certainly notice new oil formations popping up all the time if it was that fast - and some really simple carbon-dating would tell us that!)  So for sure we'll run out reasonably soon if we carry on using it at the present rate.  However, as has been said here several times before - if you turn all of the oil we have into CO2, global warming will easily kill the planet.  Hence running out is simply not possible - the planet would be dead long before we could manage that.  So let's worry about global warming instead please.


 * SteveBaker 20:32, 5 November 2007 (UTC)


 * Generation, migration, and accumulation of oil depend on a huge number of variables. It is entirely possible (though quite unlikely) that no oil is presently being generated, anywhere on earth. The proper source rocks have to be buried to the proper depth for the proper length of time. A good source rock has 1% organic material in it; an outstanding source rock has 5%. The oil window (the depth where oil can be generated) is around 7000 to 15,000 feet below the surface, with variations. Then circumstances must exist for the generated oil to migrate through rocks to a point of accumulation in a trap. All this will typically take millions rather than thousands of years for significant accumulations. The largest fields in Saudi Arabia, for example, are thought to have taken tens of millions (50-80 million, I think – sorry I don’t have the reference at hand) to be generated, to migrate, and to accumulate.


 * Steve’s calculations are interesting – just one comment: there is virtually no oil present today that is thought to have been generated at a time longer ago than about 1 billion years, and the vast majority was generated less than 400 million years ago. There just was not enough algae to create source rocks. Also, any such old oil that was generated would be very unlikely to have survived to the present, owing to tectonic activity destroying traps. It is difficult to know for certain when oil is generated, but one measure is by looking at the (usually younger) rocks in which the oil is trapped. In the US, at least 75-80% of all the oil is or was in rocks younger than about 320 million years old. The rocks that generated it would not likely be all that much older (with, of course, some exceptions). Cheers Geologyguy 20:52, 5 November 2007 (UTC)


 * Googling "petroleum creation rate" only turned up one page of questionable reliability, but according to that one page, the algae out of which our current petroleum reserves developed grew during the carboniferous period, which was only about 60 million years long. Dividing about 3 trillion barrels by 60 million years comes to about 140 barrels per day.  But even with this somewhat higher estimate, we’re still using it up almost a million times faster than it’s being created, so petroleum certainly can’t be viewed as anything close to being a renewable resource!


 * If on a bar chart you used the thinnest possible line that a 300 DPI laser printer can draw to represent the petroleum creation rate, the corresponding bar to represent the petroleum consumption rate would have to be about 166 feet tall! That's more than half the length of a football field.  MrRedact 21:11, 5 November 2007 (UTC)


 * The statement on that web page implying that all of today's oil was generated from the Carboniferous is waaaayyyy too simplistic. Most of the oil in Saudi Arabia, and much of that in Russia, is of Jurassic age, for example, while much of California's oil was generated by plants that died during Tertiary time. Nonetheless what MrRedact says is correct. Cheers Geologyguy 21:23, 5 November 2007 (UTC)


 * Pssst. Carboniferous is 300+ million years ago.  Dragons flight 22:53, 5 November 2007 (UTC)
 * Yes, I know. I said that the Carboniferous was only 60 million years long, and didn’t say anything about how long ago it was.  For the crude estimate, it made sense to divide by the duration of the Carboniferous, not by how long it's been since then.  For example, algae that lived just 1000 years ago has lived since the Carboniferous, but it will likely be many millions of years until the median time at which it contributes to usable petroleum reserves.  ("Usable by whom" is a good question, since Homo sapiens are unlikely to even exist anymore by that time.)  MrRedact 23:53, 5 November 2007 (UTC)


 * D'oh. I simply misread your comment above.  Dragons flight 23:58, 5 November 2007 (UTC)


 * As I said at the outset, we really don't know what the answer is - but even the most optimistic numbers are going to indicate that we're digging the stuff up at least tens of thousands of times faster than it's being re-formed. If we have 1.2 trillion barrels and we're using it up at 86 million barrels per day then if none is being re-formed, then we run out in 38 years.  If it's re-forming at even 1/10th of the rate we're using it (which it cannot by any stretch of the imagination be doing) then we run out in 42 years...big deal!  So it really doesn't matter how fast it's being formed - none, 3 barrels a day, 100 barrels a day, 8 million barrels a day - it makes essentially no difference to the amount of time we have left.


 * But this ENTIRELY misses the point. Let's forget global warming.  Let's do a much simpler back-of-envelope calculation.  When you burn a barrel of oil you get (in round figures) 400kg of CO2 gas.  So what happens if we burn all of the oil we have left, including oil shales and every drop we can extract as we get desperate after 40-ish years?  A hundred years from now, we'll have utterly run out after burning 4 trillion barrels altogether.  Crunch the numbers: we'll have dumped perhaps 1.8x1015kg of CO2 into the air.  The earth has 5x1018kg of atmosphere - so we'll have pushed the amount of CO2 from 0.038% of the air to 0.075%.  But that's not counting the other things like coal and natural gas that we're currently burning - which would probably push that to 0.1% or 1000 ppm.  At those concentrations more than 20% of people will experience breathing difficulties, headaches & nausea!  In actual fact, since CO2 is a heavy gas, it's likely there would be much higher densities at lower altitudes where we all live - in all likelyhood it would be reaching 2000ppm - which is enough to cause severe symptoms in nearly everyone.  The effects on other animals is unthinkable.


 * More serious still (but harder to prove with back-of-envelope math) is global warming. Those effects are already kicking in to a frankly unacceptable degree with CO2 levels only 35% higher than 'normal'.  Just think about what happens if we have three times the natural amount!


 * Truly, it's irrelevent how much oil is being re-formed. With the most optimistic estimates, it's negligable - and in any case, we won't run out because we'll have killed the planet LONG before we use it all up.  —Preceding unsigned comment added by SteveBaker (talk • contribs) 03:13, 6 November 2007 (UTC)

Carbon cycle fluxes
The number being asked for above is one that I'd very much like to have. For that matter, I've been trying to locate values for the exchange terms in the carbon cycle more generally. Approximating it at as roughly 5 reservoirs: land-based biosphere, atmosphere, oceans, crustal rocks and fossil fuels; I have been trying to get some citable numbers for the annual pairwise exchanges of carbon between each of these in the modern era.

Some terms are fairly easy. We burn about 7 GtC of fossil fuels a year, i.e. the fossil fuel -> atmosphere flux. Also, the major terms such as ocean -> atmosphere, atmosphere -> ocean, atmosphere -> biosphere, biosphere -> atmosphere, etc. are of sufficient interest that numbers (at least fuzzy ones) are out there (including ones in the figure at carbon cycle). However I have had considerable difficulty getting citations for the minor terms, e.g. biosphere -> fossil fuels, biosphere -> crustal rocks, terrestial biosphere -> oceans, oceans -> fossil fuels, etc. (I suppose one could technically define all fossil fuels as coming from carbon in crustal rocks, but I would prefer to seperate terrestial and oceanic carbon sources.)

If anyone can help in nailing down these fluxes in a rigourously citable way, it would be much appreciated. Dragons flight 22:53, 5 November 2007 (UTC)

Thanks!
Allow me to thank each one of you for your extensive responses to this question. Since it was mentioned that global warming is a far more serious issue than disrespect for the amount of time it would take to renew oil as a resource once it is gone. A question about global warming comes to mind which I will post shortly along with another question about oil production. Thanks again. I've made a copy of your responses in case the Wikipedia runs out of funds!

Dichotomous 04:24, 6 November 2007 (UTC)

Photon Energies
In general (i.e. not refering to any particular substance) can photons be created with any possible energy or are there only particular energies they can take (i.e. some sort of planck scale) —Preceding unsigned comment added by 172.200.188.149 (talk) 20:43, 5 November 2007 (UTC)
 * $$E = \frac{hc}{\lambda},$$ Wavelength (lambda) is the only variable there, and I guess it would be quantized in units of planck length. So the inverse of a photon's energy is quantized.  Or I'm wrong, I don't know.  Someguy1221 20:56, 5 November 2007 (UTC)
 * Photon energy isn't quantized in the standard model, nor (as far as I know) in string theory or loop quantum gravity. The Planck length is not a quantum of length. There are hints that there is a quantum of area (comparable to the Planck area), but not of length or time or mass. -- BenRG 21:42, 5 November 2007 (UTC)

Tapeworm
Is it medically possible to have a tapeworm infection and not know it? Has there been any documented cases of people having tapeworm for long periods of time? --WonderFran 21:16, 5 November 2007 (UTC)


 * Yes, although the symptoms will exist, some don't act on them. There have been cases where tapeworms lived inside people for many years. 64.236.121.129 21:27, 5 November 2007 (UTC)


 * If you believe you have a tapeworm, see a doctor. The symptoms of most GI-tract disorders are pretty much the same (many sharing symptoms with heart attacks).  From a gas bubble to a tapeworm to a viral infection, pains and discomfort should be diagnosed by a doctor. --  k a i n a w &trade; 23:48, 5 November 2007 (UTC)


 * The Wikipedia article on tapeworms says "infestations are usually asymptomatic", which means a person won't know right away they have one. It also says they can grow to be 15 to 30 feet long, and that will take some time. The Mayo Clinic link at the bottom of the Wikipedia article is very thorough regarding the medical aspects. As for a documented case, I think doctor-patient confidentiality would make that hard to find, but the facts speak for themselves. --Milkbreath 00:07, 6 November 2007 (UTC)

Once an infected person takes the medication to treat tapeworm, does the tapeworm exit the body they way I think it does?! ew! --WonderFran 00:31, 6 November 2007 (UTC)
 * If the way you are thinking of is "in pieces, and dead", then yes :) And yes, the orifice is the one you think.  Would you have it any other way? - Nunh-huh 00:42, 6 November 2007 (UTC)
 * Well, there's always the old, pre-medication way, which involved sitting naked in a body-temperature water bath, and waiting... —Steve Summit (talk) 02:08, 6 November 2007 (UTC)
 * While holding a nice piece of blue cheese close to your bumhole. Gotta entice those wormy worms out somehow. Then grab the worm firmly by the ears and give him / her a firm telling off and issue an eviction notice. This is not medical advice.  Lanfear's Bane |  t  16:21, 6 November 2007 (UTC)