The best answers address the question directly, and back up facts with wikilinks and links to sources. Do not edit others' comments and do not give any medical or legal advice.
This is siad to be Venus true color is it close to white with faint yellow. If I was orbiting Jupiter will the planet look like a pearl, always playing with color. Seen from Saturn's low magnitude will Saturn still be around blueish silver if I was orbiting planet. If I was far away from the planet, it will look darker, if I was clser to planet, it looks brighter. if I was orbit one foot away from Uranus, it's methane gas will still give glows of violet color since it's magnitude is 5. For Neptune, it would be essentially dim, since the magnitude is 8, I beleive I will still see a dark indigo color when I am orbiting the planet since it have little light far away, for Pluto, and it's other dwarfs, the surface will look black, even if I stad on it--Freewayguy 00:27, 30 October 2008 (UTC)[reply]
We discussed this stuff in some detail in your earlier question about Uranus's color. But what you are saying here is bogus. The 'magnitude' of an object depends on it's size as well as it's brightness. When you are up close to it - the size is irrelevant - so comparing the magnitude of these objects and using that to estimate surface brightness is pretty much meaningless. To do this right - compare the albedo divided square of the range of each of the objects from the sun. Do the comparison with the same numbers calculated for the Earth and you'll have a better idea of relative brightnesses from close to the planet. Both sets of data are available in the standardized info-boxes in the articles about each planet. SteveBaker (talk) 04:18, 30 October 2008 (UTC)[reply]
I don't think that you would see Pluto as black when you are on the surface, in the same way that the moon does not look black from earth, but a moon rock does when you have it on earth, and on the moon surface it looks bright grey. Pluto seems to be mostly an apricot colour. The light at Pluto may not be as dark as you think, instead it would be like an incandescent bulb, dim but still good enough to see colour. For Venus you are right it look white, you can see it with your own eyes. Graeme Bartlett (talk) 06:25, 30 October 2008 (UTC)[reply]
I've been to the moon-rock 'vault' at the NASA space center in Houston (it's open to visitors most days). You can see the actual moon rocks (LOTS of them!) in normal room lighting - and there is even one moon rock there that you can actually touch (although the surface of it is so covered with grease and dead human skin cells...I'm not sure you are actually getting in contact with it)! Those rocks are emphatically NOT black - they are mid-grey with very little color to them. So they match more or less what the moon looks like in the sky - with an albedo of 0.1 or so.
But here is the problem (and we talked about it before when the same OP asked about the color of Uranus): Human vision is a crappy way to measure brightness and color. We have eyes that adapt to the dark and to the very bright. So when you see Venus in a dark sky, it looks impossibly bright. But your dark-adapted eyes have shut down all of your color sensors and really wound up the "brightness" controls. So you can really only see in black and white and the fairly dim dot that is Venus is overloading the few 'pixels' in your retina because it's soaked in rhodopsin and the iris is wide open. This means that the light-sensitive cells that Venus impacts simply report "Ouch! Too bright!" and not much else. The atmosphere here on Earth is also scattering blue light due to the Raleigh and Mei scattering mechanisms...that leaches blue out of the image and further distorts any chance of getting good color information from distant objects. (Especially Venus which is only ever visible near the horizon where the atmospheric color distortions are greatest). Hence, Venus LOOKS white to the naked eye - an slightly yellowish in a telescope. When we fly a spacecraft up next to it or use the Hubble telescope - we don't have any of those annoying human visual wierdnesses - and the planet looks yellow.
So our OP asks "What color is it "really"?" - is it white or yellow?
Well, that's an utterly meaningless question. Humans can't even see yellow light properly - we don't have sensors for yellow light. We only notice it at all because it slightly stimulates our red and green sensors and we've decided to label that "red-and-green-together" sensation using the word "Yellow". However, small amounts of pure red and pure green light (such as you'd see in a photo of Venus on your computer screen) also appear "Yellow" - but for different reasons. If you stare for 30 seconds at a picture of the US (or British) flag - then look quickly over at a sheet of white paper, the paper "looks" like it has an orange and cyan flag hovering over it because our eyes have color-adapted to the strong reds and blues in the flag and take a few seconds to recover. So in orbit about Venus, our eyes would adapt to the colors and start to wash them out. So what we see and how the universe truly is are very different things - photos (either on photographic prints, or in CMYK magazine prints or RGB computer screens) have nothing like the range of colors that the planet actually has or that our eyes could potentially resolve (you simply cannot reproduce a really strong "cherry red" on a TV or computer screen for example). When NASA design a space probe - they need to capture specific data to determine chemical compositions, etc. So they may well decide to use a true yellow filter on their camera (so it really can tell the difference between a mixture or red and green light - which would appear dark - versus true yellow light - which would pass through the filter and look bright). So even the photo we took with a satellite is hopelessly "wrong" compared to what we'd see with our own eyes or with a more traditional RGB camera. Then it would depend on whether we needed to be dark-adapted to see it (in which case it would all be pretty much monochromatic) - or whether our eyes were overloaded by the brightness (in which case everything pretty much looks white). Hence it doesn't make a whole lot of sense to be asking about the "real" color of objects in space - where the lighting is so very different from here on Earth where our vision system evolved.
If you have two cars - an orange one and blue one. Park them out in the street. In daylight - they look orange and blue. At night (in the dark) they look light blue-ish grey and dark blue-ish grey. At night under sodium street lights - they look orange and black. At night under moonlight they look orange and blue again. If you have a weak-green sensor because you are mildly color-blind then the orange car looks red. If you have cataract surgery and lose the filtering ability of your corneas - then if the paint used on the orange car happens to be strongly reflective of UV for some reason and the blue car not so much so - and they both look to be different shades of blue in strong sunlight - but revert to orange and blue on cloudy days. If you stand 20 miles away from the cars and look at them through binoculars with the sun behind your back, the blue car looks darker than it did before and the orange car looks more pale - perhaps, almost yellow-ish. If you do the same thing with the sun in front of you then the blue car still looks darker but the orange car still looks even more intensely orange. What color are the cars "really"? Well, it's a meaningless question. By convention, we humans say that they are orange and blue because we have decided that normal daylight vision is what we're going to use to label the colors...but in space, there is no "normal daylight" - so that labelling scheme fails.
Hence questions about the "real" colors of planets are not ones we could (or should) answer - it falls into the realms of predictions and speculations. We should leave it up to the astronomers to create spectrograms of the light and print graphs in journals...or we should send a poet/artist along in a capsule to write movingly about the things he/she sees there and paint pictures that speak to us of the color impressions that person got.
Good answer, but a major mistake in there. We don't have red, green, and blue sensors in our eyes. The wavelength response of the three cone types is something like what's shown in this picture. The L (long wavelength) cone's peak sensitivity is actually in the yellow-green range, and it's as sensitive to blue-cyan frequencies as it is to red. But when reproducing colors we want to be able to stimulate the S, M, and L cones as independently as possible, and red (which stimulates L much more than M) is better for that than yellow (which stimulates L and M about equally). Blue stimulates S almost exclusively, and green preferentially stimulates M. Thus monochromatic red, green, and blue are useful for reproducing color. They're not good for capturing color, though. Monochromatic red, green, and blue filters throw away most of the spectral information that you need to determine the correct cone stimulus levels in the first place. To capture the perceived color reliably you need to use filters that match the cone response curves. Once you have the SML stimulus information you can derive from it the RGB intensities that will most accurately reproduce that stimulus. Of course, there are tons of details. The curves are somewhat different on different parts of the retina. Real cameras don't use the right curves. The eye compensates for ambient lighting so that white objects still look white even when illuminated by colored light, but this process doesn't work when you're viewing the photographs later in different lighting conditions. No set of three primaries can reproduce all SML stimulus triples, and on top of that the primaries used on typical computer monitors are highly suboptimal.
But the number one problem with making true-color astronomical images is not the difficulty, it's the pointlessness of it. There's nothing magical about human color vision. The particular cone types we evolved served us well in the environment we evolved in (I think the red-yellow-green distinction helps in finding ripe fruit). They're meaningless on Mars. True-color images aren't interesting to look at, and they aren't any more true to life than false-color images. Compare this false-color image and this "true-color" image. (I put "true-color" in quotes because the filters they used don't match the human cones, so the color calibration involves a certain amount of guesswork.) Our eyes don't do a good job of seeing what's interesting in these exotic environments, and it's ridiculous to copy their limitations in our technology when we can do better. That's what technology is for. -- BenRG (talk) 00:11, 31 October 2008 (UTC)[reply]
I would argue that "true color" images are "More true to life" than the false color ones. Imagine I sent my handy digital camera to Mars, snapped it a few pictures and brought it back to Earth. When I reviewed the images, the colors on the screen that I observed with my eyes would at least roughly match the colors I would have observed had I gone to Mars myself instead of sending my camera.
I completely grant that true color images are not nearly as scientifically useful. And perhaps even not worth the money required to capture accurately. But it's disingenuous to claim that there isn't an element of truth in true color images that a false color image lacks. There is a very real, common desire to know what faraway places would be like "if I were there". To satisfy this (rather unscientific) desire you need to know what things look like to human vision under natural lighting. (And perhaps what they would look like under what us earthlings would consider a white flashlight.) APL (talk) 18:41, 31 October 2008 (UTC)[reply]
Yeah, you're right. I suppose the images could even have scientific value as a preview of what future Mars colonists would see out their windows every day. I don't know whether your digital camera would reproduce the Martian colors accurately; I think they're calibrated for typical Terran lighting conditions. NASA's true-color images were made very carefully if this page is to be believed—they took all the data they had available (six frequencies), guessed the rest of the visible spectrum by cubic interpolation, then derived the XYZ coordinates from that and converted to sRGB or something closely resembling it. Reading that gives me more confidence in the accuracy of the colors. Some of the other descriptions I'd read gave the impression that they just took the blue, green, and infrared data and stuck it in the blue, green, and red channels and called it true color. -- BenRG (talk) 22:50, 31 October 2008 (UTC)[reply]
Jupiter's Great Red Spot On Earth
I've searched a lot of places but can't find anything that helps me answer...
Say that our planet was an Earth-sized Jupiter. (I.E. we're Jupiter, but not Jupiter-sized.) How big would The Great Red Spot be on here? -WarthogDemon 01:16, 30 October 2008 (UTC)
[reply]
Let's do a little math. According to our article on Jupiter, the great red spot varries in size, covering an area of 24–40,000 km × 12–14,000 km. Using the formula for the area of an ellipse (pi*a*b) we get an area of 9.04x109 - 1.7x1010 km2. The surface area of Jupiter, according to the article is 6.21796×1010 km2. Thus, at the smaller end of the scale, the red spot covers 14-27% of its surface. Given that Earth's land is about 29.2% of its surface, the great red spot would cover somewhere between 1/2 and all of the Earth's land area. As a further reference point, the Atlantic Ocean is 22% of Earth's surface area, which falls in the mid-point of the estimated sizes of the Great Red Spot. Thus, if transcribed onto Earth, it would be roughly the size of the Atlantic Ocean.
Someone can check my math on this, but it seems about right... --Jayron32.talk.contribs 02:07, 30 October 2008 (UTC)[reply]
Something must have gone wrong with the maths there. The Red Spot can't cover anywhere near 27% of Jupiter's surface, the picture on the Jupiter article shows that it covers a much smaller proportion (less than 5% I would argue by looking at the picture). According to Jupiter, the radius of the planet is 11 times larger than the radius of earth. From Atmosphere of Jupiter, the Red Spot's "dimensions are 24–40,000 km west–to–east and 12–14,000 km south–to–north." Divide them by 11 and you have the approximate equivalent. - Akamad (talk) 02:13, 30 October 2008 (UTC)[reply]
I double checked the maths, and the calculations are correct. There must be a problem with the numbers I used then; either the dimmensions of the Great Spot are too large, or the surface area given is too small. And divide by 11 wont work. If jupiter is 11 times larger, than its surface area is 112 times larger, so we would need to divide by 121. Dividing by 121 gives an Earth-scaled area of the great red spot as: 7.47x107 - 1.40x108 km2. Since Earth's surface area is given as: 5.10x108 in our article on Earth, that gives us an overall ratio of 14.6% - 27.4%, or the same thing I got by calculating it the other way. --Jayron32.talk.contribs 02:30, 30 October 2008 (UTC)[reply]
Sorry I meant divide the 24 - 40000 km by 11 and divide the 12 - 14000 km by 11 too. So you are dividing the area by 121. I think the problem in the maths was that you used 24000 km and 12000 km in the Pi*A*B equation. The numbers used should be half that (12000 and 6000) since the equation refers to the distance from the middle. See http://www.math.hmc.edu/funfacts/ffiles/10006.3.shtml. - Akamad (talk) 02:36, 30 October 2008 (UTC)[reply]
(I wrote this during and edit conflicted with above. We had the same thought at the same time) I assumed that a and b in the ellipse area equation were the major and minor DIAMETERS of the ellipse. Its not. Its the major and minor RADII of the ellipse. My answers were thus off by a factor of 4. Thus, the actual % area is 3.65% - 6.85%. Since the surface area of the earth is 5.10x108 km2, that gives us an "Earth-scaled" size of 18,615,000 - 34,935,000 km2. North America covers an area of 24,709,000 km2 , which falls dead in the middle of this range. Thus, the Great Red Spot is roughly the size of North America, scaled to Earth's dimmensions. --Jayron32.talk.contribs 02:39, 30 October 2008 (UTC)[reply]
OK - move aside - let a professional through here. OMFG! This answer is a train wreck!
Great_Red_Spot#Great_Red_Spot says "Its dimensions are 24–40,000 km west–to–east and 12–14,000 km south–to–north." - so diameters - not radii. Jupiter has a radius of 71,500 km. Earth has a radius of 6,380 km - so to convert dimensions on Jupiter to "Earth scale" you've gotta multiply by 6380/71500 which is 0.09 - or for mental arithmetic: Divide Jupiter-linear-dimensions by 11 to get Earth-linear-dimensions. So an "Earth scale" spot is 2,200 to 3,600km by 1100km to 1300km. Since there are big error bars in the original data for the spot size - let's cheat and pretend it's a rectangle of the smaller size...that way we avoid all of the ikky ellipse math stuff. So the area is roughly 2200x1100 = 2.4 million square kilometers.
Now - for comparisons: According to List_of_continents#Area_and_population, North America covers 24 million square kilometers - so I don't know how you arrived at "the size of North America"...that's wrong by a factor of 10! (Which is bloody obvious if you compare a picture of Jupiter and Earth scaled to similar sizes!)....so a third the size of Australia...or Texas plus Alaska...or somewhere between Sudan and Algeria...the drainage area of the Black Sea...I dunno.
The image (at right) was made by taking two NASA photos - one of Earth, the other of Jupiter. I resized the two images to be identical in size - then overlaid one onto the other. Finally I erased all of Jupiter EXCEPT the red spot. So - here is an image of what the OP is imagining. Notice in the top of the image we have Africa. The red spot looks to be maybe four times the area of Madagascar - which is half a million square kilometers - so two million seems about right (although it's a pretty fuzzy "spot" - so there is plenty of room for error)...anyway - it's NOTHING LIKE the size of North America.
Yes, that's why I was asking. For a size comaprison. Sweet answer! Thanks. :) -WarthogDemon 16:46, 30 October 2008 (UTC)[reply]
Great job! Edison (talk) 04:26, 30 October 2008 (UTC)[reply]
The original question described a counterfactual situation ("we're Jupiter, but not Jupiter-sized"). In answering, we have to figure out what exactly that means. To me the obvious interpretation is that the relevant linear dimensions are reduced in the same proportion, as if making a scale model. That's what Steve did. The initial derailment that started the train wreck earlier was to try working with areas, which of course vary as the square of the linear dimensions. --Anonymous, 06:00:00 UTC, October 30.00000 :-), 2008.
Yes - it's a very common error to assume that since "A is 1/11th the diameter of B" that "The area of A is 1/11th of B" (when in fact it's the SQUARE of the linear dimensions - so A is 1/121th the area of B) and that "The volume of A is 1/11th of B" (when it's really the CUBE of the linear dimensions - so A is 1/1331th the volume of B). If I had $1 for every time I'd seen that mistake made I'd have...well, actually, maybe just enough for lunch today. The trouble is that the word "size" is vague - so you hear things like "Jupiter is 11 times bigger than the Earth" and "Jupiter is 1300 times bigger than the Earth" - both of which are true in some fuzzy-thinking way. That's why I was so careful to say "Divide Jupiter-linear-dimensions by 11 to get Earth-linear-dimensions." in my answer. SteveBaker (talk) 13:12, 30 October 2008 (UTC)[reply]
The trouble is, physics isn't scale-invariant, so it's really hopeless to conceive of an "Earth-sized Jupiter". The physics that formed and sustains the Red Spot, whatever it is, wouldn't form a scale-model Red Spot on an Earth-sized planet. I don't think an Earth-sized gas "giant" can exist in any case since it wouldn't have enough self-gravity to hold it together. So the only way to understand this question is as a visualization aid: to get a feel for the size of the Red Spot, scale it down to something more familiar. Personally, though, I find these comparisons singularly unhelpful. (As the saying goes, there is so much sand in Northern Africa that if it were spread out it would completely cover the Sahara desert.) -- BenRG (talk) 12:58, 30 October 2008 (UTC)[reply]
Yeah, I was curious about a size comparison. I understand how a Great Red Spot couldn't exist on Earth. (Though hurricane speeds can get pretty close to the same wind speeds.) And plus, if I put my question further and said what if we had the Great Red Spot composed of the same materials, it wouldn't last long: hydrogen-rich storm in an oxygen-rich atmosphere? Nope, nope, nope. :) -WarthogDemon 16:46, 30 October 2008 (UTC)[reply]
For the record, SteveBaker rules. Thank you for clearing up my math mess. Your answer looks far more reasonable than mine. --Jayron32.talk.contribs 13:11, 30 October 2008 (UTC)[reply]
That's true - but sometimes it helps people to bring vast or tiny things to "human scales" in order to think about them. Saying that the spot is "big" isn't helpful - and saying that it's 40,000 km across when Jupiter itself is the largest planet in the solar system doesn't give you a feeling for it either. But knowing that (compared to the size of the planet) it's like a third the size of Australia really gives you the strong idea that this is a really big thing. On the other hand - compared to the size of the planet - it's not that much bigger than the "great white spots" we get a couple of dozen times a year here on Earth. (We call them hurricanes and cyclones). Those can be up to 1000km in diameter - which (proportionate to the size of the planet) is only about half the size of the Great Red Spot. What's different about our hurricanes is that they can't sustain themselves over land - so they inevitably fizzle out after a week or two. Jupiter has no land masses - so there is really nothing to stop the spot from staying pretty much together for (at least) hundreds of years - we don't know whether it's truly a permanent feature. The Great Dark Spot on Neptunes southern hemisphere was a similar kind of storm - and it fizzled out sometime between 1989 and 1994, to be replaced by another one in Neptune's northern hemisphere. Saturn has shown similar features (eg Dragon Storm (astronomy)). SteveBaker (talk) 13:12, 30 October 2008 (UTC)[reply]
Exactly. I was wondering, "Sure it's big to us. But if to an (theoretical) alien on Jupiter, would it be big to him/her/it?" -WarthogDemon 16:46, 30 October 2008 (UTC)[reply]
Well, that probably depends on the size of the alien more than the size of the planet. People have occasionally speculated that the Giant Red Spot IS an alien! But since Jupiter has no solid surface - anything living there must live in a gaseous environment - so it has to complete it's entire life-cycle flying or floating or something. The most likely form of such creatures would be massive solar-powered gas-bags floating around - and they could easily need to be very large indeed. So perhaps the spot doesn't seem all that big to them after all. SteveBaker (talk) 00:39, 31 October 2008 (UTC)[reply]
LANDFILLS - why are garbage cells covered with a layer of soil?
Having read the landfill page, I see that individual cells are covered with a layer of soil or in some cases another material. Innumerable other google-found webpages explaining landfills mention the same process. However, I can find no direct explanation as to WHY this is done?
Thank you.
To trap all that rubbish in a contained way. It will reduce smell, reduce vermin and scavengers, stop plastic bags blowing in the wind, and speed decay. Graeme Bartlett (talk) 06:08, 30 October 2008 (UTC)[reply]
Sounds like a technique for composting on an industrial scale. And here[1] we go... Julia Rossi (talk) 08:43, 30 October 2008 (UTC)[reply]
To close the top is sometimes done to prevent rain water going in. The water will be contaminated and has a chance to reach ground water. Other possibility is air thight closing to collect the natural gas from decomposition within the landfill. You also get rid of the smell and the animals lifing in an open landfill (rats seagulls).--Stone (talk) 11:15, 30 October 2008 (UTC)[reply]
Also, gas (methane) from the landfill is sometimes collected for use as a fuel...the soil helps to trap this in. The main reason is to keep smells and litter in and vermin outGaryReggae (talk) 12:59, 30 October 2008 (UTC)[reply]
And to provide a chance for grass to grow - maybe eventually trees - to eventually turn the area back into something useful. SteveBaker (talk) 13:19, 30 October 2008 (UTC)[reply]
I'm the original poster, and I wanted to say thank you. :-)
The decomposing organic matter produces methane, and if the landfill is not adequately vented by perforated pipes driven through it or other means, the methane can work its way through the ground and come out in people's basements. Sealing the top of the landfill might increase the likelihood of this. Edison (talk) 19:14, 30 October 2008 (UTC)[reply]
Careful Steve! When the landfill is ultimately covered and landscaped, then yes grass can grow (although you want to be careful with trees due to the roots). But just covering each cell with soil is done at the end of each day as the landfill develops, for all the reasons given above. You're likely to be putting another layer of rubbish on top of that soil tomorrow, so there's no time for grass yet! 79.66.32.150 (talk) 21:12, 30 October 2008 (UTC)[reply]
This one has me stump
How the hell do you even go about solving problems like this. By the way I have not looked at the answer.
Think to yourself what it would look like if you were pouring the liquid out. Or even better try an actual glass. Dmcq (talk) 11:06, 30 October 2008 (UTC)[reply]
Ah! I think I got it. It's a trick question. There is a measuring device. It is called the water or the water level. Using the water level as a measuring device, measure out half the volume of water in the cylinder. 122.107.157.9 (talk) 11:07, 30 October 2008 (UTC)[reply]
Did you understand what Dmcq was saying? You still need to know a way to measure exactly half. You can't just eyeball it from the glass when it's level. If you don't get it, read his statement more carefully and think Nil Einne (talk) 12:31, 30 October 2008 (UTC)[reply]
As you very slowly pour the water out, there will come a point when the surface of the water just touches the bottom of the glass (and also just the lip of the glass on the opposite side) - at that moment - it's exactly half-full....like this:
| /|
| /~|
Air--> | /~~| <--Water
| /~~~|
|/~~~~|
(Well - technically - you'll have interesting issues with the meniscus - but it's good enough for a simple puzzle) SteveBaker (talk) 12:48, 30 October 2008 (UTC)[reply]
That's one way to solve it. Another would be to completely fill the glass, and then get an identical glass and pour the water from the full one to the empty one until they both have equal amounts. --Russoc4 (talk) 19:59, 30 October 2008 (UTC)[reply]
Or you could get REALLY crazy. You could put the glass into a larger sealed container whose overall volume would allow the evaporation of the water to proceed until the vapor pressure of the water and partial pressure of the water vapor in the larger container were in equilibrium. Per the ideal gas law, you would only need to know the initial amount of water in the container you started with, and as long as you maintain a constant temperature, you make the volume larger container such a size as to allow exactly 1/2 of the original volume of water to evaporate. Its a whole bunch of algebra, but its certainly doable... --Jayron32.talk.contribs 20:13, 30 October 2008 (UTC)[reply]
And how does he measure all that? --Russoc4 (talk) 00:11, 31 October 2008 (UTC)[reply]
There's not much to measure really. Just maintain a constant temperature, and the ratio of the size of the larger, air-tight container should be some ratio of the size of the smaller, water filled cylander. This ratio is dependent ONLY on temperature and nothing else, so as long as you maintain a constant temperature, there is some ratio of large box/smaller cylander which will cause exactly 1/2 of the water to evaporate. You don't even need to know the volume of the smaller cylander; you just need to build a box that has a volume that is some number of times larger than that cylander. Here, let me work it out for you. At, say, 25oC, the vapor pressure of water, using this site: [2] to calculate, is 0.0312 atm. Now, once the partial pressure water vapor in the air is equal to this pressure, the water stops evaporating. So, lets assume, to make the calculations easier, that our cylander is 1 liter. So, we want 500 mL of water to evaporate. The density of water being 1 g/mL that makes this water have a mass of 500 grams. Divide by the molar mass of water (18 grams/mole) to give us 500/18 = 27.8 moles of water vapor. Now, by the ideal gas law, PV=nRT or for our purposes V=nRT/P, where V is the volume of the box we need, n=27.8 (moles of water vapor), R = .08206 L*atm/mol*K (the Gas constant), T = 298 K (25oC), and P = .0312 atm. Solve and you get V = 21789 liters. Now, the ratio of the amount of water to the size of the box should be constant, since less water would need a proprotionally smaller box, while all the other numbers remain constant. So as long as the box is exactly 21789 times the size of the cylinder of water, and assuming of course the air in the box was fully dry (leave a dessicant in there for a few days, then remove it right before putting the cyilnder in it), once the system equilibrates, the cylinder will be EXACTLY 1/2 empty. Oh, and for our 1-liter example, it IS a pretty big box. There are 1000 liters in a cubic meter, so the box is 21.789 cubic meters, or if a perfect cube would be 2.79 meters to a side, or about the size of the average bathroom. To answer your question, the ONLY measurement you need to make is the temperature. The ratio of the volumes is ONLY depedndent on this number. Once you know that ratio of volumes, you can simply create a box that is that much bigger than the cylinder. I never said it was an EASY solution, from a practical standpoint, but who cares about being practical. Plus, unlike the "tip the glass to the diagonal" solution, this one doesn't have the pesky meniscus problem. --Jayron32.talk.contribs 02:43, 31 October 2008 (UTC)[reply]
All of these ideas (apart from my 'tip the glass' suggestion) fail miserably because the problem states that you don't have a measuring device of any kind. If you are going to argue that getting the temperature just right in a particularly-dimensioned box doesn't constitute using "a measuring device" then I might as well say "I'll just take a second glass of exactly half the height of the original but of the same diameter, fill it to the brim and carefully pour the contents into the first glass" - which is vastly easier and gets you to the correct answer much more realistically. But I'd argue that the terms of the question say you have a glass - and water - and absolutely nothing else of known dimensions or other definite properties - since anything like that confers the ability to measure. If you're allowed to invent your own devices to help - then there are easier and more direct ways. SteveBaker (talk) 18:17, 31 October 2008 (UTC)[reply]
Oh, you are entirely right. I was just having fun coming up with the most rediculous and esoteric way to remove half of the water from the glass. Your method of using the diagonal of the glass is, of course, the only scrupulously correct way. My solution had an air of Rube Goldberg to it, and I was just goofing. --Jayron32.talk.contribs 19:02, 31 October 2008 (UTC)[reply]
Pay someone to deal with the problem. That way you do not need a maeasuring device. -Arch dude (talk) 01:37, 1 November 2008 (UTC)[reply]
There is a tradition at some US college or other that every year the following question is always asked on their 1st year general science term paper: "Given an accurate barometer, how do you determine the height of a tall building?" - the "correct" answer is obvious - but there has come a tradition of awarding extra marks for "other" answers. So, for example, one may climb to the top of the building, drop the accurate barometer over the edge and count the number of seconds for it to hit the ground - and thus determine the height. Or one could tie the barometer onto a length of string and use it as a pendulum - and by accurately timing a large number of swings, determine the variation in the force of gravity at the top and bottom of the building - and thereby determine it's height. However, the neatest solution is that you take the barometer to the custodian and say "I'll give you this beautiful (and highly accurate) barometer, if you'll tell me the height of the building". SteveBaker (talk) 02:07, 1 November 2008 (UTC)[reply]
On a pedantic level, visual perception when tilting the cylindrical container certainly is a conceptual measuring device. Clearly, you are - visually - measuring the property of the surface of the liquid in relation to the side walls / bottom of the cylinder.
Assume you are located in a space station with zero gravity in total darkness and reconsider your answer. --Cookatoo.ergo.ZooM (talk) 01:14, 2 November 2008 (UTC)[reply]
I added a subject header to your post. You may want to take time to read the guidelines if you want to receive a better response. You also should sign your post Nil Einne (talk) 12:31, 30 October 2008 (UTC)[reply]
There are three basic types of rock:
"Sedimentary" rocks (like sandstone and chalk) form as layers of mud and other 'stuff' accumulate at the bottoms of lakes and oceans ("sediments"). Over millions of years, enough layers build up that the weight of all of that stuff pressing down on the lower layers compresses them into rocks. Since the sands and other silts that make up sedimentary rocks came from older rocks that had been eroded by wind, rain, rivers, etc - it's often the case that pebbles and other small bits of other rocks get mixed up into the sedimentary rocks.
"Igneous" (volcanic) rocks form when lava or ash comes out of a volcano. As it cools, it turns into various kinds of rock. Sometimes, small bits of other rocks that got crushed up by the volcano end up mixed into the igneous rock.
"Metamorphic" rocks are formed when igneous or sedimentary rocks are crushed under yet more pressure from rocks in layers above them changes their form or composition (they change...or "metamorphose"). Some of the chemicals in a rock may get washed away by water flowing through them - and some rocks may have small voids and bubbles filled in by stuff deposited by flowing water. Some rocks get heated up by lava or by being so far underground - those undergo all sorts of chemical changes.
What element(s) are rocks actually made of? GaryReggae (talk) 12:57, 30 October 2008 (UTC)[reply]
See also Rock cycle for more info. Rocks are mostly various forms of silica and other silicon-containing compounds, though there are some other components that make for some sharp differences. The relative amounts of silica to other components will determine the differences between the rocks. --Jayron32.talk.contribs 13:04, 30 October 2008 (UTC)[reply]
Some rocks contain metals, either in a pure form like gold or in combination with oxygen or other substances like hematite(which contains iron), and these are called Ore. Edison (talk) 19:12, 30 October 2008 (UTC)[reply]
Mathematics
A delivery boy collected 5.35 pesos part in 5 centavo coins, 8 part in centavo coins. If the number of 5 centavo coins were 7 more than one-half the no. of 10 centavo coins, how many 5 centavo coins?
There is a mathematics reference desk located at Wikipedia:Reference desk/Mathematics, but if you post the question there you are going to get the same response I am going to tell you. Wikipedia is not here to do your homework for you. If you need help finding information, we can point you towards articles (like Currency of Mexico, which contains info on pesos and centavos. But seriously, you can push the buttons on your calculator by yourself... --Jayron32.talk.contribs 15:37, 30 October 2008 (UTC)[reply]
There is a standard method for this kind of question. Assign letters to all your unknowns (number of each type of coin) and then rewrite the problem as equations. You can then solve those equations to get the answer. --Tango (talk) 16:29, 30 October 2008 (UTC)[reply]
There is probably something wrong in the way you have rewritten/translated your problem, or else there is something wrong in the problem itself. As written, it's not solvable. The first sentence mentions five-centavo coins and centavo coins (i.e. one-centavo coins). The second sentence mentions ten-centavo coins and five-centavo coins. So you say you have three unknowns, but as far as I can see, you have only provided information for writing two equations. You need as many equations as you have unknowns. Also, the meaning of the first sentence is not clear. I don't understand what you mean by "8 part in centavo coins". However, if the first sentence should be "A delivery boy collected 5.35 pesos, partly in five-centavo coins, partly in ten-centavo coins", the problem can be solved as Tango suggested, by letting x be the number of five centavo coins, and y be the number of ten-centavo coins. I'll help you along by showing how you make the second sentence into an equation:
If the number of five-centavo coins were 7 more than one-half the number of ten-centavo coins
Just substitute x and y for the number of five- and ten-centavo coins:
If x were 7 more than one-half of y
Then replace the remaining words with numbers and the mathematical operators (= + - * / etc) that have the same meaning as the words:
x = 7 + 0.5 * y
Do the same thing with the first piece of information. Now you have two equations with two unknowns. Solve these, then you know the value of x and y. The answer to the question, "how many 5 centavo coins?", is the value of x. --NorwegianBluetalk 22:44, 30 October 2008 (UTC)[reply]
I'm guessing that the '8' is a typo for '&'. —Tamfang (talk) 00:08, 31 October 2008 (UTC)[reply]
menstruating women
My question is why women who are menstruating easily get or feel electrocuted once they simply touch a door knob or any thing that is made of metal?
That sounds unlikely to me. I can't see any reason for it. The chance of getting static shocks depends on what you're wearing (particularly your shoes), what kind of floor you walk on and also the weather (dry air doesn't conduct as well as humid air, so you can build up a charge easier). I can't see why it would depend on whether or not your menstruating. I guess it's possible that some women like to wear big fluffy jumpers when menstruating and that's what causes it, but that's about it. --Tango (talk) 18:22, 30 October 2008 (UTC)[reply]
It may be possible menstruating women are more sensitive to the sort of thing for some reason. But I agree with you it seems unlikely and there's no evidence so far to suggest otherwise. Nil Einne (talk) 12:46, 31 October 2008 (UTC)[reply]
Maybe they're grumpy, and stomp their feet more? :P DewiMorgan (talk) 03:41, 2 November 2008 (UTC)[reply]
Pay attention to the pi-bonding and the location of the hydrogen atoms in 3D space, and what effect that has on the strength of the C-H bond. Remember that an acid is any substance that easily loses an H+ ion, and that will be directly related to the strength of that C-H bond (i.e. the weaker the bond, the better acid it is). Another factor is the relative stability of the resulting carboanion (i.e. if you lose an H+ as an acid, you will leave behind a C- ion; and the pi-molecular orbitals in the triple bond system has an effect on the stability of that carboanion. --Jayron32.talk.contribs 18:19, 30 October 2008 (UTC)[reply]
This page here: [3] also contains lots of good info on the reactivity of alkynes (the class of compounds that acetylene is the smallest member). Read closely the section titled "Acidity of Terminal Alkynes". --Jayron32.talk.contribs 18:23, 30 October 2008 (UTC)[reply]
An sp hybridized carbon also has a higher electronegativity than sp2 and sp3, making the resulting carbanion relatively stable. --Russoc4 (talk) 20:01, 30 October 2008 (UTC)[reply]
"three-day malaria": would it call brain damage?
Hello. I'm playing Merlie Ryan in an adaptation of Carson McCuller's Ballad of the Sad Cafe. Merlie is known as "Crazy Merlie", and is generally the village idiot. In the book, it says he has the "three-day malaria", which means for two days he's dull and cross, then on the third day he livens up and has an idea or two, mostly foolish.
The entry for malaria says it can cause brain damage if you get it when you're young, so I'm assuming that's why he's foolish. But the play lasts for about 8 years. Could he have malaria the whole time? I thought you'd get better or get dead. And is it right that it might have caused some sort of cognitive problem? In the play he seems to be uninhibited, as if his sense of social appropriateness is missing. Might that come from the disease?
Slightly rambling question there, but I'd be grateful for any light anyone can shed on the effects of the disease.
To answer your second question, having a fever at an early age can cause developmental disabilities (Someone asked a related question a couple weeks ago). Mental retardation can present in a way where the individual lacks appropriate social skills. They actually have to have a deficit at least two of the following: communication, daily living skills, or social skills. -- MacAddct1984(talk • contribs) 21:12, 30 October 2008 (UTC)[reply]
(ec) Well, "three-day malaria" is "tertian malaria", which is that caused by Plasmodium vivax. The three-day cycle corresponds to the release of the merozoites from the liver and their invasion of red blood cells. Vivax malaria is not as bad as other forms of malaria, and is seldom fatal. The usual treatment is with chloroquine, which was developed in the 1930s -and was acknowledged as first line therapy since 1946 - I'm not cure if The Ballad of the Sad Cafe is explicitly set after this. But chloroquine alone doesn't cure the disease; to wipe out the liver infection primaquine is necessary, and this became available in the late 1940s, and wouldn't be widely available until after that, and so probably wouldn't figure in "Sad Cafe" published in 1951. So Merlie definitely would be expected to suffer from a chronic form of malaria that would last years and years. I don't think Merlie's foolishness is necessarily attributable to his malaria, though. But in answer to your specific question, absolutely he could have malaria the whole time. But no, people with malaria are not noted for being socially inappropriate in the way that, say, drunks, are. The brain damage in those who have it seems to result in cognitive difficulties: trouble in memory, in concentration, and learning. You could play Merlie as not caring much about social niceties because of his preoccupation with his own suffering; you could play him as unable to concentrate, with a short attention span; you could play him as mentally "slow". BTW, today we think of malaria as a disease of travellers, because it's been eradicated in the U.S. now, but in Merlie's time could certainly have been acquired here. - Nunh-huh 21:28, 30 October 2008 (UTC)[reply]
Thanks for the prompt replies! We have set it finishing in 1945, so none of the treatments mentioned would be available to him. And it's useful to know that he could have suffered for the whole time without actually dying. "Unable to concentrate" seems to match most with my impressions of the character, but it's the way she links the three-day cycle of the disease with his activity and behaviour that confuses me - two days cross and dull, then livens up on the third to have a few foolish ideas. I thought at first this was a poetic way of saying he had some form of bipolar condition, but given that three-day malaria is a genuine thing, this seems less likely. Maybe having a fever involves less time shivering in bed than it does in my imagination, or maybe it's feverish in the sense of a feverish imagination.
78.86.213.238 (talk) 22:45, 30 October 2008 (UTC)[reply]
Well, it would certainly be fever in the sense of increased body temperature, but not all fevers involve shivering in bed or cold sweats. In 1945, he would probably have been taking quinine, which is not terribly effective (especially as it had to be made from cinchona bark rather than synthesized in 1945) but would have given some relief. - Nunh-huh 01:14, 31 October 2008 (UTC)[reply]
There were some experiments with using malaria as a way to create fever and control syphilis, specifically neurosyphilis. The idea was that since malaria was a known quantity and would produce a fever that could be controlled by use of quinine, the patient would avoid the worst symptoms of the syphilis in exchange for the discomforts of malaria. Before you get too excited about the character's possible lurid past, the disease can be congenital (passed from mother to child). SDY (talk) 09:35, 2 November 2008 (UTC)[reply]
I caught a weasel in my house!
Well, its either a weasel or a ferrit (I thought it was a rat at first when I found it rummaging in my upturned kitchen bin and I was going to brain it with a claw hammer). The RSPCA man can't come to pick it up until tomorrow. I've put it in a cat carrier with some straw and given it water but what do I feed it? Sunflower seeds? Nuts? Hay? Carrots? They're similar to rabbits and other small rodents aren't they? --84.64.99.103 (talk) 21:54, 30 October 2008 (UTC)[reply]
If you check the articles Weasel & Ferret you'll see they are both carnivores! If you want to feed it (assuming you don't have any live mice around) I'd suggest raw unprocessed meat of some type. Exxolon (talk) 21:58, 30 October 2008 (UTC)[reply]
It could also be a Stoat. You might not want to keep a ferret in the house - they REALLY, REALLY STINK! Anyway - it won't die if it goes without food for 24 hours - and you know it just ate when you caught it. You aren't doing it any favors by getting it used to getting free handouts from humans - so you should probably avoid giving it anything at all. So long as it has water and fresh air - it'll be fine. SteveBaker (talk) 00:28, 31 October 2008 (UTC)[reply]
Depending on where you live, it could also be a fisher cat or any other of a number of mustelids. Still, they are pretty much requisite carnivors, like a cat, so if you threw some hambuger or something in there, it should be fine. Cat food would probably work too... --Jayron32.talk.contribs 02:23, 31 October 2008 (UTC)[reply]
Unless the RSPCA man is travelling an absurdly long way, the OP lives in Britain. 81.174.226.229 (talk) 10:09, 31 October 2008 (UTC)[reply]
Why not just let it go in the local woods where it can find its own food? I mean, unless it's injured I'd think the reason to call the RSPCA would be to catch it, which you took care of on your own, so why not release it on your own as well? --Shaggorama (talk) 05:58, 31 October 2008 (UTC)[reply]
Sorry, I should've made it clear. I'm quite sure that it's someone's pet. It's very tame. Either that or it's ill and weak (looks okay though). I fed it some beef last night and I gave it some cat food this morning. The guy is coming by to pick it up later. —Preceding unsigned comment added by 90.241.161.187 (talk) 11:54, 31 October 2008 (UTC)[reply]
Identification problem? - one is weasley recognizable because the other is stotally different, Chi-boom! Richard Avery (talk) 22:55, 31 October 2008 (UTC)[reply]
It's true...fi-shur, cat-egorically...fer it is just the same. Must he lied. SteveBaker (talk) 01:55, 1 November 2008 (UTC)[reply]
I realize you boys are fisher-ing for laughs here, but if your dad told you were funny, he must'a lied. Frankly, you otter be ashamed at your stoatally stinky puns, but I'll stop badgering you now that I've skunked you. Matt Deres (talk) 14:05, 1 November 2008 (UTC)[reply]
Just a quick update. The mustelid I found turned out to be a ferret and was definitely an escaped pet. She was only a youngster too. She had a few ticks and was a bit skinny but otherwise seemed to be in reasonable health on first inspection. She's been taken to the animal shelter and all being well, will be rehomed if they can't find her original owner (apparently, they don't have much of a problem rehoming ferrets). --84.64.31.41 (talk) 17:19, 1 November 2008 (UTC)[reply]
Drug interactions
I know that ibuprofen can decrease the effectiveness of atenolol in terms of it's antihypertensive properties, but I don't know the mechanism by which it does this. Any ideas? —Cyclonenim (talk · contribs · email) 22:43, 30 October 2008 (UTC)[reply]
I don't know exactly, but my initial guess is that ibuprofen might induce higher concentrations of the enzyme that metabolizes atenolol, therefore reducing the effectiveness of atenolol, assuming the parent compound is the active one. --Russoc4 (talk) 00:07, 31 October 2008 (UTC)[reply]
I'm pretty sure that atenolol is renally cleared, so that's not it. Also, ibuprofen reduces GFR (at moderate concentrations), which would be expected to reduce renal clearance (and increase atenolol concentration, all other things being equal). My guess is that the renal effects of ibuprofen would generally raise blood pressure, and that would counterbalance atenolol's effect. If there's a more direct mechanism, that would be interesting. --Scray (talk) 02:24, 31 October 2008 (UTC)[reply]
I had a further look around and found somewhere that it's an antagonistic effect due to NSAID-induced inhibition of renal prostaglandins, sodium and fluid retention. Thanks. —Cyclonenim (talk · contribs · email) 10:31, 31 October 2008 (UTC)[reply]
Yes, the effects you describe are the mechanism for the reduced GFR I noted, resulting in raised BP. --Scray (talk) 02:04, 1 November 2008 (UTC)[reply]
Yes, ibuprofen and other NSAIDs block prostanglandin synthesis, including PGE2. By the way, you know that beta-blockers are no longer recommended as treatment for hypertension? Axl¤[Talk] 11:13, 31 October 2008 (UTC)[reply]
The problem was initially flagged by this classic paper in the Lancet. Beta-blockers will reduce blood pressure equally well, but they do not prevent the undesirable outcome: stroke, as effectively. There have been several other papers showing similar findings. Here is the Cochrane review. The NICE guideline states "the cost-effect analysis... [supports] the clinical data in that beta-blockers are the class of drug least favoured, and CCBs and thiazide-type diuretics appear the most cost-effective choices in most scenarios". Beta-blockers are now fourth-line treatment. Axl¤[Talk] 11:37, 31 October 2008 (UTC)[reply]
That's 4th line as a a sole agent, I think most UK doctors would demote slightly further given that as multiple drugs are introduced, so patient's would typically already be on bendroflumethiazide... and thiazides in conjunction with atenolol is diabetogenic which I understood was final issue (on background of above cited findings of less good outcomes) - so likely alternative would be of an alpha blocker... but that's to digress away from avoiding NSAIDs in hypertensive patients, but also relevant to mention is that long term NSAIDs may cause deterioration in kidney function... David RubenTalk 02:21, 2 November 2008 (UTC)[reply]
preventing liver spots?
i'm 23 and my hands look fine, but I wouldn't like to have liver spots all over them when I'm 76. Do you think I can do anything (daily) or avoid doing something so I won't get them eventually?
I'm not asking for medical advice.
You could start by reading the article liver spots. It answers your question. --NorwegianBluetalk 23:26, 30 October 2008 (UTC)[reply]
My textbook says concentration of pure solids and liquids is taken as unity.But no explanation is given as to why.Can some1 please why is it taken so?
"Concentration" in what sort of units? If you are asking about %, it should make some sense that a pure sample of some chemical X is "100% X" based on the standard meaning of percent ("X is what fraction of the whole?"). But for concentrations that aren't just "fractional of the whole", it's clearly a false statement: 1 g of water is 1/18 mole and has a volume of 1 mL, so it most certainly does not have a molarity of 1 mol/mL. DMacks (talk) 23:58, 30 October 2008 (UTC)[reply]
It is because 1 part in 1 is that pure substance. And 0 parts in 1 of anything else. In reality what you may call pure sugar for example will have air between the crystals, and the density of the bulk material may be below that of a pure uniform crystal. They would be saying the concentration of H2O in water is 1 and the concentration of NaCl (or anything else) in pure water is 0. Graeme Bartlett (talk) 00:03, 31 October 2008 (UTC)[reply]
Actually, the above is not really the reason. It sounds good, but it doesn't get to the heart of the problem. The one could certainly calculate the "concentration" of a pure solid. It would merely be the density (grams/liter) divided by the molar mass (grams/mol). You would get mol/liter, which is of course concentration. After all, we can and do use concentrations of pure gases, and their calculation can be done essentially the same way. The same problems where a pure gas concentration is used as calculated, the pure solid concentration is treated as unity. This is not the same thing as being equal to one, but we'll get to that in a minute. The question is "Why do you need to know the concentration?". For the problems I am guessing you are doing, you are probably working in kinetics and equilibrium, that is the problems are largely dependent on the rate of reaction. The rate of a chemical reaction is dependent on the number of collisions occuring between the reactants. In gases and aqueous solutions, the reactants are spread out over a large space, so how often they colide is a direct function of how close together they are packed. If you double the number of molecules of a gas or an aqueous solution in a given space, the number of collisions doubles as well, because the molecules are forced closer together. Thus, changes in amounts effect changes in rate. Now, here's the thing with pure solids and pure liquids. They are condensed phases, which means that the molecules are already touching essentially. If you, say, double the number of molecules of a pure liquid, you don't effect the rate at which those molecules collide since those molecules can't be forced closer together. Thus, for questions that involve rates of reaction, the amounts of condensed phases don't affect the rate of the reaction. In our calculations, we ignore these amounts because they don't change the outcome. Ignoring them is the same as multiplying by 1 (since multiplying by 1 doesn't do anything at all). So we say that we treat them as "unity", but we could just as easily say we ignore them all together, because they don't affect the outcome. When you do an equilibrium calculation, well, the equilibrium is just a situation where the rates of the forward and reverse reactions are equal. Since equilibrium is determined by rate, and solids and liquids don't effect rate anyways, we can ignore these here too... --Jayron32.talk.contribs 02:18, 31 October 2008 (UTC)[reply]
As usual with context-less questions, there are many possible answers as you make different assumptions than others:) DMacks (talk) 03:19, 31 October 2008 (UTC)[reply]
Having been a chemistry teacher for 10 years, I think I am fairly qualified to make these assumptions. The only type of situations where one finds the statement "treat the concentrations of solids and liquids as unity" is in the kinteics and equilibrium chapters of your standard general chemistry textbook. Its the particular phrasing he used, and that he mentioned that it came from his textbook that cued me in on the kinds of problems he was working out. Trust me on this, he's working out rate law and equilibrium problems. --Jayron32.talk.contribs 03:26, 31 October 2008 (UTC)[reply]
Yup. The real problem is when they think that context doesn't matter, which is why I led with that caveat. Otherwise they get into my chemistry class and tell me "the concentration of water is 1" or "solvents don't have a concentration themselves" because that's what they were told, not knowing what the heck it actually means:( DMacks (talk) 04:04, 31 October 2008 (UTC)[reply]
Which is why I teach them the right contexts, see above. --Jayron32.talk.contribs 04:38, 31 October 2008 (UTC)[reply]
When working with reaction rate and equilibrium-type problems, you're not actually using the concentration of the substance, you are using the Activity (chemistry). This isn't an absolute measure, it's a dimensionless relative measure. Usually, the reference concentration is taken to be 1 mol/L, so that the activities match exactly with the concentration. However, this is not always the case, and very concentrated solutions can have activities which differ numerically from their molar concentration. In the case of solids, the activity doesn't change when increasing the amount of undissolved material. Thus the activities are constant, and are effectively rolled into the rate constant or equilibrium constant. The same thing happens with rates and equilibria in aqueous solution: the amount of water in most solutions is near constant (~55 M), and varies very little from one aqueous reaction to another, and is defined as unity. If you happened to be working in a solution where the concentration of water was significantly different from a normal aqueous solution (e.g. in a highly concentrated alcohol in water mix) you would have to explicitly account for the water concentration, and would have to use rate and equilibrium constants which account for this. -- 128.104.112.72 (talk) 15:51, 31 October 2008 (UTC)[reply]
October 31
Why is space so big?
I mean, isnt the distance just....overwhelming? You cant wrap your mind around it! Just think about how big a light year is. The distance that light travels in a freakin' year, that's what! That's 11,600,000 miles in just one minute! ....Wow Wow Wow...When we say that something is millions of light years away, I just...can't comprehend it.--Sunburned Baby (talk) 02:56, 31 October 2008 (UTC)[reply]
Space is so big because its been around for a long time. If we consider that the availible evidence tells us that the universe is expanding, and since we know about how fast it IS expanding and about how long it has been expanding, we get an estimate for how big the whole thing is. And the answer is REALLY FREAKING HUGE. No shit. I used to teach an Earth Science class, and for the astronomy unit, I would take the kids out to the football field to map out the solar system. If you put the sun at one goal (endzone or soccer goal, its about the same size) and put pluto/neptune at the other goal/endzone, then on that scale the sun is the size of a Quarter coin, and the earth is about the size of a speck of sand. And that's ONLY our solar system, which if scaled to such a size so that the galaxy could fit on a football field, the entire solar system would be a speck of sand. And if we put our galaxy on a football field scaled to teh size of our local group of galaxies, it would be a speck of sand, and so on and so on. Feeling insiginficant yet? --Jayron32.talk.contribs 03:14, 31 October 2008 (UTC)[reply]
Another issue is safety. From the Anthropic principle we know that we have not been wiped out by a gamma ray burst or stray star or black hole, so they have to be far away from us. Graeme Bartlett (talk) 03:17, 31 October 2008 (UTC)[reply]
I never know whether saying "the volume of the observable universe is around 3×1080 cubic meters" makes the size seem more or less comprehendable. At least I can actually consider how immense that is, rather than saying "larger than I can imagine", but then I have troubles imagining 1080. DMacks (talk) 04:11, 31 October 2008 (UTC)[reply]
Often when one gets a question like this it makes sense to invoke the anthropic principle and assert that if it weren't just so then life as we know it wouldn't be here to observe it. However I'm not sure if that is the case here. What if instead of being 3×108 m/s, the speed of light were only 3×104 m/s ? The visible universe would be 1/10000 the diameter it is now, but would it really matter? We'd expect our new universe to have room for ~1 galaxy, but who needs the other galaxies anyway? Satellite communication might suck, and microchips wouldn't be as speedy, but does life as we know it really require such a large c?
As far as I can tell, the answer would appear to be no. Are there any really fundemental downsides to envisioning a universe with a much slower speed of light (and hence a universe that grows much more slowly)? Dragons flight (talk) 04:28, 31 October 2008 (UTC)[reply]
The point is that the processes that created our galaxy require a universe with more than just our galaxy. Our galaxy exists only because the processes that create galaxies require a universe which is pretty much exactly the size it is now, with a fundamental speed of light equal to exactly what it does in our universe. If the laws were not so, the conditions would not exist to create the Universe as it is, with us studying it. Its not just about whether or not we could survive in a 1-galaxy universe with a slower speed of light; we could, its that such a universe could not have come into being in such a manner as to create the necessary conditions for life to exist. The Anthropic Principle is a bit of a tautology, but a useful one. --Jayron32.talk.contribs 04:45, 31 October 2008 (UTC)[reply]
That's merely an assertion, not an explanation. What about the big bang and structure formation requires lots of space? Galaxies nucleate from primordial density fluctuations that would presumably still exist. The necessary mass only comes from a sphere ~10 times wider than the ultimate disk of the galaxy itself. I don't see any reason all that other distant mass is actually necessary to forming a galaxy. As best I can tell, the dynamics of galaxy formation don't require the universe to be huge. Dragons flight (talk) 05:06, 31 October 2008 (UTC)[reply]
Having a small speed of light would also affect speed of gravity, and a galaxy may not form as big as we know it. Then you may find a lack of heavy elements needed to make planets and humans. We also need plenty of space to make a cold background in the sky, so that solar energy can drive life on earth. Graeme Bartlett (talk) 05:36, 31 October 2008 (UTC)[reply]
Look man, space is big. Really big. You just won't believe how vastly hugely mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space. Listen: When confronted by the sheer enormity of space, better minds than the ones responsible for this reference desk have faltered. Some invite you to consider for a moment a peanut in Reading and a small walnut in Johannesburg, and other dizzying concepts. The simple truth is that interstellar distances will not fit into the human imagination. :) --Shaggorama (talk) 05:51, 31 October 2008 (UTC)[reply]
I can easily envision space being much much much bigger say a googleplex times as wide or maybe another power or two than that. Why is it so small relative to us? Perhaps it just couldn't be any smaller. Dmcq (talk) 09:06, 31 October 2008 (UTC)[reply]
Big can be looked at in other ways too: which is more, stars in the Milky Way or cells in a single human brain? stars in the Universe or bacteria in the oceans? Franamax (talk) 09:33, 31 October 2008 (UTC)[reply]
My very quick research shows there are about 2-4 times as many stars in our galaxy as there are neurons in the human brain (I don't know about other cells). I have no idea how many bacteria there are in the oceans, though... --Tango (talk) 17:22, 31 October 2008 (UTC)[reply]
You need to be careful when considering what would happen if a physical constant were different. All the constants are interrelated, so if you're changing the speed of light you're going to have to change some others as well. What would happen will depend on which ones you change and in what way. There is a way of doing it (I don't remember the details) that results in pretty much no observable change at all because it results in atoms being 10,000 times smaller, and therefore everything else is 10,000 times smaller (that doesn't follow exactly, but I think the conclusion is still correct) so the time it takes for light to get from A to B is unchanged since A and B are just closer together. --Tango (talk) 10:43, 31 October 2008 (UTC)[reply]
"Space is big. You just won't believe how vastly, hugely, mind-bogglingly big it is. I mean, you may think it's a long way down the road to the chemist, but that's just peanuts to space." - Douglas Adams88.211.96.3 (talk) 11:25, 31 October 2008 (UTC)[reply]
Space is so big I totally didn't notice someone had a more complete version of this quote above me! 88.211.96.3 (talk) 11:46, 31 October 2008 (UTC)[reply]
Space is big to protect the rest of the universe from usAdambrowne666 (talk) 11:33, 31 October 2008 (UTC)[reply]
Which seems fairly complete. In the absence of faster-than-light technology, which seems unlikely to say the least, humans are just not really going to get very far as a species in space. Look upon "we'll colonize space!" proposals with a gimlet eye unless someone suggests a really plausible explanation of how we'd get significant numbers of people (e.g. significant breeding populations) anywhere useful within the lifetimes of those traveling. --98.217.8.46 (talk) 13:26, 31 October 2008 (UTC)[reply]
I believe the trick is NOT to try to do it in the lifetimes of the people inside. We need huge, landscaped, spinning (for artificial gravity) mini-worlds made from hollowed out objects from the 'belt - each with LARGE populations (thousands of people at a minimum). Power will have to be from fusion sources to keep the fuel supply compact enough - and the progress from one star to the next has to be expected to take thousands of years. It seems inevitable that such habitats will be needed in the future - and once there are enough of them in solar-orbit - it's only a matter of time until one of them takes on the trip. If you are living your life in such a place anyway - it may not make much difference to you whether you are orbiting the sun - or heading off to Alpha Centauri with no hope of arriving during your lifetime.
An alternative (which is perhaps more likely to be of interest and I'm fairly sure will happen in the next 100 years) is the "scan your brain - produce an exact software simulation of it - then die". "You" will continue to exist with all of your thoughts and memories intact inside a computer somewhere - presumably with some kind of robotic body with robotic senses. You feel like you are still "you" and your family and friends can easily tell it's still you - and you behave pretty much like any other human - albeit in that robotic body. Now we can do a couple of interesting things:
Shoot a small, unmanned probe to the next star. It's small - it gets there in 100 years and proceeds to drop off some handy robots. When it arrives, we transmit a colony of humans by radio or laser communications to the probe and thence to the robots. Elapsed journey time is at the speed of light - but to the traveller it would seem instantaneous. When you arrive, you live out your life in a robotic body - and if you want to return - you simply transmit yourself back again as another radio signal and you're home again in the blink of an eye. The travel time is still at the speed of light - so it's gonna take 4 years to go and 4 years to come back from Alpha Centauri - but 8 or 9 years away is not so terrible if you don't have to endure the journey.
Using a very small probe - shoot a computer and a robot body to the nearest star. But have the computer's clock rate be adjustable. When there is nothing much happening, it executes one instruction every second - when there is an emergency - or at the start and end of the journey - it runs at a few teraflops. Your brain can 'fast-forwards' through the boring parts and consume almost no energy - and zero other resources. When you arrive, you ramp the clock up to full speed and download yourself into the robotic body to do whatever exploration you fancy. Sure - it takes hundreds of years to get there and to get back again - but you won't die of old age and you won't get bored.
Once you can 'fast forward' your life through the boring bits and have your thoughts and memories transmitted and reconstructed at the speed of light - you can live as long as you want to - and there are a LOT of interesting possibilities.
A wonderful Star Trek-like solution, but the humans you imagine have little to do with any humans I have ever seen. Make a big dome, put a few thousand humans inside it, wait a few weeks and they'll be in a state of civil war, disrepair, disaster. I don't see us getting off this planet in any major way. The human race will, at some point, go extinct—of that there cannot be any question. Once you accept that it just becomes a question of when and where. --98.217.8.46 (talk) 21:12, 31 October 2008 (UTC)[reply]
There are plenty of remote groups of humans with populations under 1000 who manage just fine. The Pitcairn Islands had a rough start - but they survived and thrive today with almost no contact with the outside world and only just barely enough genetic diversity to keep going. I don't see the need for passimism in that regard. As for the "humanity" of the humans I imagine - well, I think what matters is our intellects - and what I suggest would preserve that in the purest way possible. You might think we couldn't survive that - yet wikipedians talk via the clunkiest links - form friendships - and seem in every way "human" - even though we rarely meet face to face. If my brain was merely simulated on a big computer - I don't see how you could possibly tell. SteveBaker (talk) 01:48, 1 November 2008 (UTC)[reply]
Sure, they have their problems - it's inevitable. But recall that I was responding to: "wait a few weeks and they'll be in a state of civil war, disrepair, disaster"...and after 200 years, the Pitcairns are not only NOT in a state of civil war, disrepair OR disaster - but they actually have a legal system, a school and so forth. I don't pretend that a community of a thousand humans heading off for a thousand years in the direction of Alpha Centauri wouldn't have problems - sure, there will be criminals, there will be horrible divisions about matters of policy - but they can deal with that if they have no alternative - and the Pitcairn Islanders are about as close to that situation as I can easily find information about. But small tribes out in the Amazon have also been found who have been more-or-less cut off from other humans for centuries and are doing OK. SteveBaker (talk) 17:41, 1 November 2008 (UTC)[reply]
This can't be allowed to pass unnoticed : "If [SteveBaker's] brain was merely simulated on a big computer - I don't see how you could possibly tell."APL (talk) 16:58, 1 November 2008 (UTC)[reply]
Photons and Phonons
In special relativity, light are waves, and the inertia of objects increase as the velocity of objects increase toward the speed of light. sound are also waves, so do the inertia of objects increase as their velocity increases towards the speed of sound? —Preceding unsigned comment added by Superwj5 (talk • contribs) 12:14, 31 October 2008 (UTC)[reply]
Short answer, no. You get interesting aerodynamic effects as you approach and pass the speed of sound (sonic booms, etc), but nothing relativistic. While light and sound are both waves, they are very different things - sound is compression waves in a medium (air, usually), light doesn't have a medium, it's just self-propagating electric and magnetic fields. Light is a fundamental feature of the universe, sound is just a consequence of vibrations in matter. --Tango (talk) 13:19, 31 October 2008 (UTC)[reply]
Bosenova
Does anybody even have any evidence what Bosenovae really are? Or at least some possibilities and guesses? I think they might have entered an unknown interaction and changed into sparticles, bosinos or dark matter or perhaps the magnetic field stuck some of the atoms into their Schwarchild radius in quantum gravity and Hawking radiated into other stuff? Do you have any idea what it is? —Preceding unsigned comment added by Superwj5 (talk • contribs) 12:22, 31 October 2008 (UTC)[reply]
Apart from what the Bosenova article says, no people don't know exactly. But you'll find proposed theories on it if you search arxiv.org and scholar.google.com. For instance, Phys. Rev. Lett. 89, 180403 (2002) Mean-Field Theory of Feshbach-Resonant Interactions in 85Rb Condensates implies 'rogue dissociation. For a definition, see arXiv:physics/0607075v1 but simply put the atoms in the bose einstein condensate spontaneously turns into molecules, which are then repelled. This process is more likely at certain densities than others. EverGreg (talk) 14:34, 31 October 2008 (UTC)[reply]
Why don't rockets work underwater? 98.221.85.188 (talk) 16:06, 31 October 2008 (UTC)[reply]
The basic principle will work - you throw something out the back you'll get an equal and opposite reaction pushing the rocket forwards. However, resistance from the water would make an underwater rocket extremely inefficient, probably to the point of being useless. The same is true of air, to a lesser extent, rockets are significantly more efficient in a vacuum than in the atmosphere. That's one of the reasons for taking off vertically and then going sideways to enter orbit, rather than taking off diagonally to start with - you spend less time in the atmosphere. Propulsion underwater usually involves taking in water from the front and expelling it out the back (eg. using a propeller), that turns out to be far more efficient that expelling rocket exhaust out the back. --Tango (talk) 16:37, 31 October 2008 (UTC)[reply]
Yeah, what are you guys talking about? Rockets work just fine under water. They just don't move as fast. Missiles are routinely launched from submarines underwater, and you can fire a fireworks rocket or Estes model rocket into a swimming pool and observe that it still works. ~Amatulić (talk) 21:01, 31 October 2008 (UTC)[reply]
Sure - the distinguishing difference between a rocket and a jet is that a rocket contains it's own oxidizer. Hence it likely burns just fine underwater. Gasses still shoot out of the back pretty quickly - and Newton's laws guarantee that if something shoots out of the back - it WILL go forwards. The only question is thrust-versus-drag ratios that will affect your accelleration and top speed underwater. SteveBaker (talk) 01:37, 1 November 2008 (UTC)[reply]
How to select motor rating for pure electric vehicle
(moved from Village pump).
If i want to replace a 150cc IC engine base two wheeler with an electric vehicle run by a direct drive motor what rating of motor will i have to use??? Is there a direct relation between cc and kW of the machine??? Any help please??? —Preceding unsigned comment added by LifestyleBangalore (talk • contribs) 16:38, 31 October 2008 (UTC)[reply]
Try to find an equivalent horsepower or kW rating. The cc number for an engine tells you very little about the power it can produce these days. It's a bit more complex than that though - electric motors have spectacular low-end torque - so you can get really great 0-60 times with a fairly wimpy little motor - but then find that your top speed sucks. That may not matter if you do lots of in-town driving and very little freeway - but it's easy to be fooled by those kinds of numbers. Also, without a gearbox, you need a very flat torque curve across the entire RPM range - electric motors are pretty good at that - but some are much better than others. SteveBaker (talk) 18:03, 31 October 2008 (UTC)[reply]
Customizable open office walls
What kind of walls can be used to divide an open office?--Mr.K.(talk) 18:20, 31 October 2008 (UTC)[reply]
They're usually referred to as "Office Partitions". A google search will get you loads of suppliers sites, and an image search lets you see the variety on offer. Fribbler (talk) 18:26, 31 October 2008 (UTC)[reply]
Not all open office dividers are "cubicles". My office is a donut design. The elevators, plumbing, and main cabling are in the middle. Offices are around the outside windows. They are divided using full-height walls and doors that appear to be real fixed walls. The advantage is that the maintenance people can move walls around to enlarge or divide offices as needed. -- kainaw™ 21:11, 31 October 2008 (UTC)[reply]
"Oh look, see, its not a square office, so your not a mindless paper-pushing drone like those people who have to work in cubicles. See, you mean something as an individual cuz you work in a round building!". Industrial psychology writ large... --Jayron32.talk.contribs 02:35, 1 November 2008 (UTC)[reply]
Is that worse than: We took out all the cubicle walls so you can see your coworkers all the time and have no privacy at all because who needs privacy when we're all one big happy family. -- kainaw™ 16:58, 1 November 2008 (UTC)[reply]
My perception of quality-of-life at the workplace has been largely independent of the various office layouts I have experienced. With large offices containing dozens or hundreds of employees with individual preferences, it will be hard to maximize the layout-to-happiness quotient (first you have to find some way to measure that). I tend to think that a lot of employees complain about all office layouts, and have no real motive other than whining. Nimur (talk) 18:30, 3 November 2008 (UTC)[reply]
In sci-fi, whenever there is an EMP everyone runs around frantically turning everything off. Does that actually help? If so, how? My understanding of the relevant physics suggests it wouldn't (and the unreliable sources I've found via google tend to agree), does anyone know for sure? --Tango (talk) 22:15, 31 October 2008 (UTC)[reply]
That makes as much sense as space ships executing banked turns in weightless vacuum, or having high-current power lines running behind display panels so they emit showers of sparks when something bad happens.
No, turning things off after an EMP event accomplishes nothing. It may help to power-off stuff before the pulse. In my industry, we can incorporate nuclear event detectors that cause critical equipment to switch off automatically, to protect them from EMP, and the equipment itself is designed to be "hardened" against such events in the first place. ~Amatulić (talk)
Sorry, I should have said "whenever there is *going to be* an EMP", obviously turning things off after they've been fried isn't going to help. --Tango (talk) 22:48, 31 October 2008 (UTC)[reply]
I think the OP is asking, "does EMP only affect things that are turned on in the first place". I mean, does turning things off change anything if they are not hardened to EMP in the first place? --98.217.8.46 (talk) 22:51, 31 October 2008 (UTC)[reply]
There is absolutely no doubt that EMP is "real". In the early 1960s, computers used clunky 'Ferrite core memory' technology. You could literally see the individual bits as little grey donuts threaded on wires. One interesting thing about core memory is that it's magnetic - and if you turn your computer off and back on again, it doesn't wipe the memory as happens with "DRAM" technology. As core memory became obsolete, the very last application of it was in military aircraft that were designed to deploy nuclear payloads. After they dropped "the bomb" - and turned around to get the heck out of there - the aircraft stood a chance of catching the EMP from it's own weapon. Hence they used core storage in their flight computers - so that the computer could be turned off and rebooted without losing a beat.
What an EMP does is to induce voltages in metal objects in its path. If you are close enough - and the geometry of the metal is just right - that voltage may be large enough to disrupt or destroy the circuit. Whether turning it off helps has to depend on an awful lot of things. Let's imagine some delicate piece of electronics with two LONG wires going off to a switch and a battery. If the wires lie in one pattern then the voltage will be induced between the battery/switch and the electronics - and both ends of the wire that contact the electronics could be at the same voltage - the electronics themselves might be small enough to to pick up any significant voltage at all. In that case, the electronics are probably undamaged. If we imagine another situation where two wires lead out of the electronics in opposite directions then the induced voltage could be large and fry the electronics instantly. If the switch happens to be up close to the electronics - and breaks the physical connection between the long wires and the electronics - then sure - turning it off beforehand ought to reduce the risk...but it's certainly not going to ensure it'll be undamaged. Turning the switch off AFTER the pulse has passed is obviously pointless though.
So - if you know an EMP is coming - I guess you should turn off anything you can get to in time - there is no guarantee it'll help - but then there is no guarantee that an EMP will destroy everything electronic/electrical anyway.
So the key thing is not so much to have things switched off as to have them unplugged (or otherwise isolated from the long wires), so if you have a laptop running off its battery, it's not going to matter whether it's on or off? --Tango (talk) 01:54, 1 November 2008 (UTC)[reply]
Yes exactly. Most things plugged into the power grid will likely be fried - an EMP crossing those mile-long power lines (or even the shorter ones that go into your house) induces one heck of a voltage. The longer the conductor, the more voltage induced for a given EMP. I think the "magic number" is 30 inches (76 cm) for nuke-level EMPs to damage sensitive electronics. Not sure what era's electronics that was for though. ArakunemTalk 14:47, 1 November 2008 (UTC)[reply]
In those sorts of stories no one ever runs around disconnecting antennas. Personally, I'd do that first. APL (talk) 16:47, 1 November 2008 (UTC)[reply]
Age of Aneurysms?
I'd like a little more information about aneurysms that I couldn't find in the article. First, what ages can get them? Can you even have them from birth? I know the article did mention men have a higher risk than young women, but would it still be reasonable for a teenage girl to have an aneurysm? Also, if they burst, does it always lead to death? Thanks for the help! 71.13.209.44 (talk) 22:40, 31 October 2008 (UTC)[reply]
Aneurysms can be present from any age, as far as I'm aware. I read a case study of a 1-month year old male who had one, so it is possible, but the risk increases significantly with age and aneurysms in paediatric patients are rare. If you're asking about teenage girls having aneurysms, and you are that teenage girl, I strongly suggest you seek the help of a doctor. It is possible for a teenage girl to have an aneurysm, but again, it'd be rare at such a young age. If an aneursym ruptures, a lot of factors can determine the outcome. Where was the aneurysm? Aneurysms in the brain feature high mortality rates, same with the aorta (this one in particular is incredibly high without prompt medical treatment). However, they do not always lead to death —Cyclonenim (talk · contribs · email) 23:15, 31 October 2008 (UTC)[reply]
No, I'm actually looking up some stuff for a friend's NaNoWriMo book! But thanks, that helped a lot! 71.13.209.44 (talk) 00:30, 1 November 2008 (UTC)[reply]
Wish your friend luck! I never won an edition of NanoWrimo, so if your friend does, they're already a step ahead of me. - Mgm|(talk) 22:31, 1 November 2008 (UTC)[reply]
November 1
Do chimpanzees and apes have menstrual periods?
I'm wondering if chimpanzees and apes/gorillas have menstrual periods like humans, or if they have an egg already ready and waiting, and if that is the case, do the females go into "heat" like cats and dogs?Cindycat (talk) 00:47, 1 November 2008 (UTC)[reply]
Its a good question. We have three articles on Chimps: Chimpanzee, which covers the genus Pan in general, and the two species of chimpanzee: the Common Chimpanzee and the Bonobo or pygmy chimpanzee. Chimpanzee females of both species exhibit what is called "genital swelling", an engorgement of the vulva, which is an indication of being ready to mate. Common Chimpanzees only exhibit this during fertile periods, while the Bonobo female is pretty much in a state of constant sexual readiness, regardless of fertility. However, our articles coverage on Chimpanzee sexual physiology is lacking, and I am not much of a zoologist, so I will have to defer to a more expert person beyond that. As far as Great Apes beyond the Chimps, well, 3 genus (Chimp, Gorilla, and Orangutan), 6 species, and about a dozen or so subspecies of Great Ape, and our articles there don't expand much on this either. --Jayron32.talk.contribs 02:30, 1 November 2008 (UTC)[reply]
This seems to be the best answer that the internet has to offer. Accordingly, only great apes would appear to have true menstrual flows, though many mammals have cycles where the uterine wall becomes receptive to implantation. In non-apes, that tissue is usually reabsorbed if no pregnancy occurs, with little or no overt blood loss. In a few species, blood loss is observed during ovulation (as distinct from menstruation). Dragons flight (talk) 05:27, 3 November 2008 (UTC)[reply]
When was the speed of sound broken (by man made object)
When was the speed of sound first broken by a man made object. No please do not give me the Chuck Yeager crap. 122.107.157.9 (talk) 02:13, 1 November 2008 (UTC)[reply]
When a bubble collapses - it moves at the speed of sound. Babies have blown saliva bubbles since the dawn of time. SteveBaker (talk) 03:15, 1 November 2008 (UTC)[reply]
Huh? Cite, please. Bubbles breaking don't make a sonic boom. Whips do. --Anonymous, 04:16 UTC, November 1, 2008.
Perhaps you haven't listened close enough. Ever wondered what makes a bubble 'pop'? Richard Avery (talk) 08:26, 1 November 2008 (UTC)[reply]
The escape of the slightly pressurized air inside? --Anon, 02:45 UTC, Nov. 2, 2008.
I suppose technically a finger joint is "a man made object" - but it's a bit of a stretch. SteveBaker (talk) 16:55, 2 November 2008 (UTC)[reply]
Why is Chuck Yeager crap? --Masamage♫ 16:57, 2 November 2008 (UTC)[reply]
What did you learn when you read the sound barrier article, which even has a "History" section? I assume there's at least some non-crap in there for you. DMacks (talk) 18:40, 2 November 2008 (UTC)[reply]
I think our OP merely means that while Yeager is widely credited to be the first person to break the sound barrier - his plane was not the first man-made object to go supersonic. SteveBaker (talk) 13:22, 4 November 2008 (UTC)[reply]
And if you study the history of his flight, you'll find that the Bell X-1 was patterned after the .50BMG machine-gun bullet -- an object that was well-known to go faster than sound. --Carnildo (talk) 00:45, 5 November 2008 (UTC)[reply]
Paleobotanist
who is the most published living paleobotanist today? —Preceding unsigned comment added by 76.4.150.238 (talk) 03:12, 1 November 2008 (UTC)[reply]
Can anyone give me suggestions or give me tips and things to look out for? I am building a ROV with a constraint of using these materials provided to me:
2 24" PVC pipes
10 L-joints
10 T-joints
3 motor mounts
The tethered ROV will be dropped and launched in a 50x25m pool. The ROV will pick up a metallic object using an electromagnet and will drop it on a target elsewhere in the pool. --hello, i'm a member | talk to me! 04:15, 1 November 2008 (UTC)[reply]
Well - clearly you can take 4 L-joints and 4 straight bits and make a rectangle. Do that twice and you have two rectangles. You can cut each of the straight bits in two and insert the 'top bar' of a T into the middle of each side of each rectangle. Now, use four more straight bits to connect together the verticals of the T's to make a cube. Fix on your motor mounts (I have no idea how - without a picture, it's hard to know - but you have two more T's and two more L's to make more structure if you need to make that mounting go more smoothely. I presume you have a way to control the speeds of the motors - and if you only have 3 motor mounts - then you probably only have 3 motors. I would put two on two sides of the ROV - pointing backwards - and one on the bottom - pointing downwards. By driving the bottom motor forwards or backwards - you can make the ROV rise or sink - by using the other two motors together - you can go forwards or backwards - and by driving one forwards and the other backwards, you'll be able to spin on the spot. The most important thing (IMHO) is to weigh your motors, batteries, electronics and other on-board stuff to figure out how much pipe you need to make the thing only JUST float. You can measure the outside diameter of the pipe and figure out how much water it displaces and make sure that your total displacement is slightly more than the weight of the machine itself. You don't want it to float too well because if you do, the "up/down" motor won't be powerful enough to make it sink. If you don't make it float well enough - then if something fails (and it will), it won't just naturally float to the surface. You're unlikely to get this exactly right the first time - so aim to make it float a bit more strongly at first - and you can always shorten the tubes to shave off a bit of bouyancy before you finally glue the whole thing together. SteveBaker (talk) 17:19, 1 November 2008 (UTC)[reply]
Thanks. How and where should I place my electromagnet? --hello, i'm a member | talk to me! 18:35, 1 November 2008 (UTC)[reply]
Without knowing what kind of attachment point you have - or the size of the thing you're trying to pick up - it's hard to know - but you need to be sure that the object doesn't unbalance the ROV when you pick it up because you don't have enough motors in the design to correct things if it ends up being (say) pointed downwards at 45 degrees. Your bouyancy calculations have to be a compromise between being neutrally bouyant WITH the object attached and WITHOUT the object being attached. If the object is very small/light then that may not matter at all - but if it's big and heavy compared to the ROV then it'll matter a lot. Ideally - you'd like the electromagnet to be at the bottom - in the center of the craft so it won't get unbalanced - but sadly, that's also where you'd like the vertical thruster to be - and they can't both be there! Can you let the electromagnet dangle on a wire a foot or so below the craft? That would be the simplest thing - and the end of the wire could then be pretty central to the ROV without disturbing the thrust from the vertical motor. There must be other parts allowed in the design - because your list doesn't include the motors or the propellors or the means to control them - you must be allowed things like cable-ties or electrical tape - and I'm sure you can use those to hold the electromagnet - or it's wires - to the structure. The critical thing that I'm trying to impart here is the vital necessity of the thing being slightly (but only slightly) positively bouyant - and being balanced, both when stationary and when thrusting and both with and without the load it has to carry. A little positive bouyancy is good because you'll be able to easily retrieve it when (not if!) it fails during testing - yet too much positive bouyancy will prevent the thing from being able to dive when the downward-pointing thruster is activated. Since your only source of bouyancy is the tubular structure of the ROV itself, you need to calculate that stuff up-front (don't guess!) and be prepared to tweak the lengths of the tubes until it floats absolutely how you want it to. Since you have limited amounts of tube - you need to start with them being a little longer than your calculations suggest so that you can cut them down as needed (you can shorten a tube - but you can't lengthen it again!)...make small adjustments until you home in on the perfect bouyancy. Similarly, the craft will be more stable if the weight is below the center-line (ie the center of gravity is below the center of bouyancy). In order to turn, you want the two thrust motors to be as far apart as you can make them horizontally - but as close to the center of bouyancy as possible so it'll drive smoothly forwards and backwards without pitching up or down. SteveBaker (talk) 15:44, 2 November 2008 (UTC)[reply]
Mechanical Puzzle
This has been bugging me. Say we have two identical cylinders A and B, with their axes parallel and set up to spin freely. Then gear them together so that B always spins through three times the angle A does. Procure a long strip of stretchy material (rubber band or something) and attach one end to A. Wrap it around A repeatedly, keeping a bit of tension so it doesn't slip off, and when you get to the end stretch it out and attached the loose end to B. Now, spin B to wind the rubber band off of A. Once it's wrapped around B, it will be three times as stretched out as it was when it was wrapped around A. So, if you let go, will it unwind? If so, with how much force? Black Carrot (talk) 07:39, 1 November 2008 (UTC)[reply]
Yes, it'll unwind with the same force as it was wound up. Just put on wheels, a seat steering and brake and you've got yourself a green vehicle for when fuel prices go up again :) Dmcq (talk) 10:23, 1 November 2008 (UTC)[reply]
OK - I agree - it'll unwind with approximately the force you used to wind it up - minus the losses due to overcoming friction. We can't calculate the force because you didn't tell us the properties of the rubber or the frictional forces involved. But before we all get too excited, think about this: It would work better (as an energy storage device) if B span 10 times as fast as A...100 times as fast...INFINITELY FASTER. So A stays exactly still and B rotates freely. The 'A' end of the rubber is simply fixed in space and winds around B as required. Well, that's exactly what a clockwork motor does. To do get the best out of real rubber, you need to understand that the force required to stetch is gets drastically more as the rubber gets close to its breaking point. So as your device gives up its energy, it produces most of it all in a rush at the start - then kinda fizzles out. The fix for that is to make the cylinders taper so that they wind around the biggest diameter at the start - and then to progressively narrower parts of the cylinder. This makes it easier to wind the thing and to provide a nice even power output for a given input. SteveBaker (talk) 16:49, 1 November 2008 (UTC)[reply]
I'm going out on a limb here, but I'm pretty sure that doesn't make any sense. The point of this setup is that only a small section of the rubber band is being adjusted at any time, and the rest is sitting still. The friction of the band against itself and the band against the cylinders requires that. The part that is being adjusted is only stretched out a small amount, well within the tolerance of this material. It's very different from holding one of the cylinders fixed and removing the gears, and there should be no loss of speed near the end. Black Carrot (talk) 19:11, 1 November 2008 (UTC)[reply]
In my read of this, the band will just unwind itself. It appears that the band is wrapped around A just enough to hold it there. Then, it is wound around B until it is "off of A". So, it is no longer attached to A. It is just wound around B. You end up with one end touching B and most of the band wound tightly around B. There is a free end now dangling. Before you even let go of the contraption, the band should quickly unwind itself off B. -- kainaw™ 02:51, 2 November 2008 (UTC)[reply]
Schwarzschild Radius
How do you even get the Schwarzschild Radius from General Relativity? —Preceding unsigned comment added by Superwj5 (talk • contribs) 11:20, 1 November 2008 (UTC)[reply]
Our article on Schwarzschild radius does not seem to show this derivation directly, but there are a list of references at the bottom of that article. These may lead you to some more detailed information. Also, we have articles on Gravitational singularity, Black hole, Event horizon, and on General relativity, all of which may have bits and pieces of the answer you are looking for. --Jayron32.talk.contribs 15:54, 1 November 2008 (UTC)[reply]
Well, you don't really need relativity to do that - good old Newton does just fine. The radius depends on the mass of the black hole - and a rough way to calculate it is the mass of the black hole divided by the mass of our sun multiplied by 3 (in kilometers). You can calculate it exactly: Use the mass to calculate escape velocity as a function of distance: v2=G.M/r and note that at the Schwarzschild radius, the escape velocity is the speed of light. So the radius is G.M/c2 (G is the universal gravitational constant). SteveBaker (talk) 16:27, 1 November 2008 (UTC)[reply]
You've missed out a 2. Newton's laws work even better if you get them right! ;) It's v2=2G.M/r and the Schwarzschild radius is 2GM/c2. --Tango (talk) 17:09, 1 November 2008 (UTC)[reply]
Ooops! My bad! Perhaps this explains why I haven't heard back from my superluminal probe out at GRO-J1655-40. ;-) SteveBaker (talk) 17:56, 1 November 2008 (UTC)[reply]
I believe in the articles it states that the derivation by Newton's math is technically incorrect for some reason. Mac Davis (talk) 00:25, 2 November 2008 (UTC)[reply]
Update: Ah, here's what it says: Note that although the result is correct, general relativity must be used to properly derive the Schwarzschild radius. It is only a coincidence that Newtonian physics produces the same result.Mac Davis (talk) 00:44, 2 November 2008 (UTC)[reply]
And that statement is unreferenced. Seriously, why are Newtonian physics inadequate, if they produce the same result? What kind of bullshit is that? --Jayron32.talk.contribs 01:09, 2 November 2008 (UTC)[reply]
Newtonian physics is an approximation that only holds under certain circumstances. Near a black hole isn't one of those circumstances, it just happens that the correction term is zero in this case by coincidence. An example of a very similar calculation where the coincidence doesn't work is when you look at orbits around a black hole. Using the same approach we could determine that the closest you can have a stable orbit around a black hole would be where the orbital velocity is the speed of light. Orbital velocity (for an object of negligible mass in a circular orbit) is , that would give a radius of , half the Schwarzschild radius (so you could have a stable orbit within the event horizon, but couldn't escape). General relativity, however, gives a last stable orbit a 1.5 times the Schwarzschild radius (I won't do the derivation here, mainly because it would take me too long to remember it), a completely different answer. So Newtonian physics gives the right answer to one question and the wrong answer to another very similar question - that's a pretty good reason to call the correct answer a coincidence. --Tango (talk) 01:43, 2 November 2008 (UTC)[reply]
I know that the Schwarzschild radius can be derived from Newton's laws and how, but my question is how in General Relativity!!!------The Successor of Physics 14:40, 3 November 2008 (UTC)
UK digital tv switchover
I have a friend who is keen to keep her old black-and-white television through the digital switchover as the licence is so much cheaper. Of course this tv doesn't have a scart socket, but apparently all she needs is a (Freeview) set-top box with an RF output rather than (or as well as) the usual scart. The official site lists several models of box that have this, but a couple of hours of searching brings up few on-line suppliers that have any of them in their catalogue, and none of those actually have any of those models in stock. Does anyone know for sure that these boxes are actually available? Or does anyone know of a gizmo that can convert the scart signal to RF for the aerial socket on the back of the television?--Shantavira|feed me 14:05, 1 November 2008 (UTC)[reply]
One possibility is to find a VCR with a scart socket for input and an aerial socket for output.
It seems like all you need is a simple format adaptor for the jacks, these sort of gizmos are widely availible in the U.S. at Radio Shack stores, which are somewhat ubiquitous (its hard to find a strip mall built in the last 30 years withOUT a Radio Shack). Whatever the UK equivalent electronics store is will likely have sales people who may be able to match you up with the right equipment. It is likely a $5.00 adaptor will make it so that ANY digital converter box will make her TV work just fine... --Jayron32.talk.contribs 15:50, 1 November 2008 (UTC)[reply]
I'm guessing you don't know what a 'SCART' socket is! (This particular HORRIBLE standard is unknown in the US - which is "A Good Thing") SteveBaker (talk) 16:29, 1 November 2008 (UTC)[reply]
Holy crap that is an awful piece of junk. this was designed by the French. No wonder the French designed it. How did this become industry standard? In the U.S., we have relatively simple-to-work-with AV connectors, including RCA connectors and Coaxial cable and the like. The different sorts of connectors generally interconvert with a simple adaptor. No wonder this is a problem in the U.K. Ugh... --Jayron32.talk.contribs 16:55, 1 November 2008 (UTC)[reply]
Thanks, and yes, scart plugs are dreadful things. They have to be wiggled vigorously in and wiggled vigorously out. Anyway, I think the UK equivalent to Radio Shack is Maplin Electronics. I get lots of stuff there but I haven't been able to find a scart-RF converter there so I assumed they weren't possible. If anyone can show me a product code for such a thing I'd be grateful.--Shantavira|feed me 18:05, 1 November 2008 (UTC)[reply]
What's truly impressive about the gargantuan SCART plug is that they are an absolute bitch to plug in - really tough to pull out - yet somehow they manage to spontaneously fall out without any provocation whatever. SteveBaker (talk) 18:15, 1 November 2008 (UTC)[reply]
Anyone who hates SCART will read this and think "Crickey! That's just the part of the iceberg above the water". They are truly a disgusting invention, I wish we could switch over to something else. —Cyclonenim (talk · contribs · email) 18:54, 1 November 2008 (UTC)[reply]
Just a guess, but it wouldn't surprise me if you could find such units at Tesco or Asda. Also try http://www.superfi.co.uk/index.cfm/page/moreinfo.cfm/Product_ID/4720/source/kelkoo which I found on kelkoo using "freeview rf output" and manually filtering out the expensive ones or ones with no rf output. (Oh yes - check it really is rf output and not just rf loopthru) -- SGBailey (talk) 22:47, 1 November 2008 (UTC)[reply]
Scart isn't that bad really IMO, I find they rarely come out accidently and aren't that hard to connect and disconnect (certianly less hassle than the FIVE phono plugs two of which are often the same color that are needed for component video and audio). And it's simple for the user, one standard cable between thier TV and the peice of AV equipment and job done.
And yes you CAN get scart to RF converters (e.g. http://www.maplin.co.uk/module.aspx?moduleno=33050 ) but they aren't cheap (partly because just like a composite to RF adaptor for the US they need active electronics. partly because they are an item that few people need since AV equipment kept the RF outputs for many years after new TVs got scart inputs) it will almost certainly be cheaper and easier to get a freeview box with RF output built in (such as one of those linked on that freeview.co.uk page the guy above mentioned).
From my U.S. perspective, the problem with SCART seems to be that its using a sledgehammer to do a Ball-peen hammer job. I mean, what is the need for a 21-pin connector for AV equipment. In the U.S., surround-sound, High def home theaters are run using 5 cables: 1 video and 4 audio channels, and RCA or RF cables work fine for these applications. Even more modern standards, like S-video use at most 9 pins for 2-way video communication. Seriously, whoever decided that was a good idea needs to be given a good stern talking to... --Jayron32.talk.contribs 00:52, 2 November 2008 (UTC)[reply]
S-video isn't that great is it? It's only Y/C. SCART supports RGB while admitedly YPbPr is now becoming more popular, I presume it seemed a fine idea at the time. And none of those provide data signalling. Personally I've never used SCART other then with adapters (I've had devices with SCART output but no SCART TVs) but it seems fine to me, provided all devices have them. Definitely simpler then 3 cables for video which is needed for component/RGB in most other cases + at least 1 audio for mono direction (x2 if you want bi directional=8 cables). Incidentally my experience with adapters is similar to anon. They aren't that hard to plug in. They aren't that secure either mind you but then again, nor is svideo and at least the pins are a lot more difficult to damage (unlike svideo) Nil Einne (talk) 07:59, 2 November 2008 (UTC)[reply]
But that's half the problem - SOME SCART devices support RGB - some support component - but some don't - and a few support both standards on the same connections with switches or menu options to configure them - so when you connect two gizmo's together, you have no clue whether it'll work - and no clue what form of video they'll be exchanging if they DO work. The cables themselves often leave out conductors in an effort to make them more flexible - resulting in cables that don't work when you connect them between devices that (against all odds) would have worked had all of the necessary wires been there. Separate cables at least let you SEE what's connected to what. A 21 wire connection might just about be bearable ordinarily - but because these are analog video signals, they have to be coaxially shielded - resulting in either monsterously thick cables - or cables that invite noisy connections - or cables with missing conductors. But my main complaint is the sheer mechanical ineptitude of the design and the overall chunkiness of the thing. Try fitting a SCART plug onto the side of a sexxy slimline laptop! When I lived in the UK, I used to need to push my TV up against the wall to save space - but the scart plug itself is over an inch deep - it has a stiff strain relief behind that - which adds another inch - and the cable itself needs about a 3" arc to bend through 90 degrees - so my TV has to be SIX INCHES from the wall! Compare to my US TV which has a recessed panel with the connections on it and the thin cables and short connectors are such that the TV can go right back against the wall with no gap at all. I dare not think of the ugliness of a flat panel TV with SCART connections! SteveBaker (talk) 15:26, 2 November 2008 (UTC)[reply]
According to the SCART article, the vast majority of modern devices do support RGB. Some also support component (but since it was a later addition it's not required nor should be expected). I don't know whether talking about laptops or flat panel TVs is fair, after all, these things were invented in the 1977 (and was the first standard evidentally). It's not as if 25 pin serial or parallel connectors are fun and they are new (I think) then SCART. If you want to argue that SCART is outdated and should die, I would agree, but then I don't find that S-video + audio or three component + 2 audio x 2 (okay that isn't quite fair since RGB isn't bidirectional) for is great either. Ultimately everything is moving to digital, or should provided the studios don't go too nuts about copy protection so all of these nasty cables will die but I personally having used them all to some extent don't find either of them that great, they each have their advantages and disadvantages. I think a lot of people do find SCART a lot easier then the large multitude of cables you otherwise need despite the other issues that can arise. Perhaps alternatives would have been better but I suspect until recently definitely, the advantages were probably minimal to not make it worth such a confusing switch. Even now, it seems most don't consider it worth it [4]Nil Einne (talk) 14:38, 3 November 2008 (UTC) Nil Einne (talk) 14:19, 3 November 2008 (UTC)[reply]
Frankly, at this point, 10GHz Ethernet would be a great standard...in fact, I'd like everything to support that - my toaster, my MP3 player, my doorbell - and TV, radio, etc...everything. SteveBaker (talk) 19:19, 3 November 2008 (UTC)[reply]
Glaciation during an ice age - source of the ice?
Hi. I'm wondering, during a glacial period, where does the ice actually come from? This seems like an obvious question, but right now I have two opposing ideas, and I could not find information on Wikipedia or the Internet. When an ice age begins, is the expansion of the glaciers caused by extra snow piling over time after being evaporated from the ocean? Or, could some of the ice be frozen from the surface of the ocean, increasing ice mass near the shore and reducing sea level? Or, is it a combination of both? It seems that nowadays, glaciers retreat because of warmth and sublimation, and they grow because of extra snow deposited on it. However, for the glaciers to grow quickly, the snow would need very high evaporation rates from the ocean, but isn't that supposed to happen during warm periods, not cold ones? I know Snowball Earth was supposed to have been started when extra rain washing the carbon dioxide out of the atmosphere (could that happen in a globally-warmed world?), but Pleistocene ice ages are supposed to be started by cold weather from Milakovich cycles, not rain washing the CO2 away? If the freezing of the ocean adding to the ice pack as a negative feedback occured, does that mean the ice pack could have left some brackish water behind while it melted, buried in the deepest regions of the Great Lakes? What is the current scientific view on where the ice came from? Thanks. ~AH1(TCU) 17:05, 1 November 2008 (UTC)[reply]
Take a look at the glacier article. Definitely formed from snow under high pressure. Sea-ice is different, it is much thinner than glaciers and is saline, unlike glacial ice which produces fresh water. SpinningSpark 18:30, 1 November 2008 (UTC)[reply]
Actually, sea ice is mostly fresh too. When water freezes, the ice crystals don't have space for salt molecules, so the salt stays behind in the increasingly salty liquid phase. If freezing is fast it is possible for the salt to be trapped in the frozen ice, as pockets of brine surrounded by freshwater ice. Over time, though, if subjected to thermal cycling or pressure (say from a thick layer of ice) the brine pockets merge and eventually are expelled from the ice. The increase in salinity due to brine rejection from freezing ice is one of the driving forces behind the thermohaline circulation (see also polar ice packs for more info). -- 128.104.112.72 (talk) 19:43, 1 November 2008 (UTC)[reply]
Type of ammunition ?
I found an old rifle shell (the bullet had been fired). The bottom is stamped "1907" and it appears generally identical to an 8 mm Mauser shell except for one unusual feature. Unlike an ordinary rifle shell that necks down once (where the bullet is joined to the shell), this shell necks down twice and appears to be made to be joined to a bullet 4 mm in diameter. The shell was found in an area where the French and German armies squared off during World War II, and a couple of 1930-s era 8 mm Mauser shells were nearby. Anybody know what kind of ammunition this might be ? --91.32.103.137 (talk) 18:40, 1 November 2008 (UTC)[reply]
A bit similar, but the second "neck" on the shell I have is 15 mm long. I wondered if it is some kind of a blank round but from what I can find the Germans were using crimped blank rounds, at least in World War II. —Preceding unsigned comment added by 91.32.105.90 (talk) 11:02, 2 November 2008 (UTC)[reply]
This is hardly a science question - you'd do better to ask it on the Miscellaneous desk. SteveBaker (talk) 15:10, 2 November 2008 (UTC)[reply]
Hypothetical Noble Gas
My Chemistry teacher is having my class make potential elements and describe their properties. Most of the properties should be based on the typical behavior in the group we put them in-the group I've chosen is the Noble Gases. My question: how many elements would be in the currently non-existent periods 8 and up? Is it 18 or 32? I'm mainly confused over whether such periods would have a collection similar to the Lanthanides and the Actinides.71.34.48.41 (talk) 19:58, 1 November 2008 (UTC)[reply]
Maybe this extended periodic table will help: [5] --Russoc4 (talk) 20:05, 1 November 2008 (UTC)[reply]
Are you sure that table is correct? Can anyone else vouch for it? 71.34.48.41 (talk) 21:44, 1 November 2008 (UTC)[reply]
We have an article on the periodic table and noble gases. Just go and take a look and come back with a more specific question if you need to. - Mgm|(talk) 22:22, 1 November 2008 (UTC)[reply]
There are some embedded assumptions about the filling order of f and g shells that we really have no way to test. So the placement of superactinides and the like on those extended charts may not really reflect their chemistry. Of course on the other hand, if those atoms can be created at all they are probably are so unstable that they would never have any demonstrable chemistry anyway. Dragons flight (talk) 23:20, 1 November 2008 (UTC)[reply]
On the other hand, there are some hypothesis that some huge elements (the atomic number 132 sticks in my head for some reason) may become significantly more stable than their lighter counterparts, having half-lives that may make it possible to do some real chemistry with them. However, for the purpose of this educational activity, being scrupulously correct is probably not all that important. The idea is to gain a fuller understanding for the importance behind the organization of the period table in order to predict "hypothetical" undiscovered elements, much in the way that Mendeleev used his table to predict the properties of the as-yet-undiscovered elements such as Gallium and Germanium. Sometimes, the importance of teaching this lesson requires that we fudge the real facts, especially at the high school level. See Mendeleev's predicted elements for more info on this... --Jayron32.talk.contribs 00:44, 2 November 2008 (UTC)[reply]
THAT'S IT! Thanks for finding that article Tango. I knew I wasn't crazy... --Jayron32.talk.contribs 02:37, 2 November 2008 (UTC)[reply]
According to this article from Nature, the average velocity of the 1s electron is (Z/137)*c. This to me implies that while it may be possible to create a stable nucleus of high atomic weight, it's not possible to have an actual atom (i.e. populated electron shells) above Z=136. Also, as that point is approached, relativistic contraction of the orbital sizes (and possibly relativistic increase in mass?) would radically alter the chemistry, so assuming that properties will remain similar as you go down the column of the periodic table might not be safe. Franamax (talk) 08:14, 2 November 2008 (UTC)[reply]
I haven't read the article, but is that formula actually expected to hold for heavy atoms? Isn't it more likely that a derivation including relativity (which is easier said than done) would just result in a different formula (which reduces to that one in the non-relativistic case)? --Tango (talk) 13:42, 2 November 2008 (UTC)[reply]
Of course the formula is not expected to hold. For relativistic speeds, use relativistic physics. Use the Dirac equation instead of the Schrödinger equation and the speeds will be below c for arbitrarily large Z. Icek (talk) 15:14, 2 November 2008 (UTC)[reply]
Well gee, the paper is titled Relativistic effects in homogeneous gold catalysis, so you'd think they may have used relativistic physics, wouldn't you? The box where "Relativistic effects" is explained has "In 1928 Dirac developed a new equation..." and goes on to use that equation. The example they use is Hg, where the 1s electron is at 58% of c. I can send a copy of the paper, drop me an email. Franamax (talk) 20:50, 2 November 2008 (UTC)[reply]
Sorry - I was wrong, the Dirac equation is actually not sufficient, and one needs quantum electrodynamics in order to compute the ground state for Z > 137 (Z >= 1/α). Btw, the Nature paper is freely available here. Icek (talk) 23:01, 3 November 2008 (UTC) := Just check the Janet periodic table and yuo'll see that the next two periods each have 50 elements ending in atomic numbers 170 and then 220 (for the nobel gasses). You also might want to check the images in Talk:Nuclear model about how to build a model of them.WFPM (talk) 18:49, 9 November 2008 (UTC)[reply]
Alright, thanks. I could also use help with finding a basic chemical property that a noble gas might have, but I know that's pushing the "We don't do your homework" policy. 71.34.48.41 (talk) 18:15, 2 November 2008 (UTC)[reply]
Note: I already have one about how noble gases rarely react due to their full outermost electron shells.71.34.48.41 (talk) 18:26, 2 November 2008 (UTC) :=Nobel gasses have the common property of having all the periods completely filled within the atomic nucleus. The next element has to be an add on involving the creation of a new period of elements. The next period will be 4 elements longer than the previous second 50 element period, and thus involve 72 additional elements. WFPM (talk) 19:03, 9 November 2008 (UTC)[reply]
Why aren't there better batteries for portable devices?
How far away are we from having really good, long-lasting batteries for our cell phones, iPods, laptops, etc? Batteries that will last through--I don't know--maybe a day, two days or a week of continuous use. Has there been any progress in this area?--69.114.164.38 (talk) 21:41, 1 November 2008 (UTC)[reply]
I think we are quite along way form that. Recently memory as decreased in size and cost, unfortunately this is not possible for batteries. Batteries use a chemical reaction to work; trying to improve this is extremely hard.
Inductive charging allows for an electronic device to be charging with out an electronic connection - the electronic device just has to sit on the charger. This will probably be integrated into tables so your battery will be charging when you’re using you laptop or other electronic device.
Although I say it is hard to improve batteries, there have been great developments for batteries. We don't notice these improvements because we are taking more and more power from the batteries, for example a laptop 5 years ago might have had a 2 hour battery-life, now a new laptop might also have a 2 hour battery-life but now it has to run many more power-intensive programs, WiFi, bluetooth etc.
W.i.k.i.p.e.d.i.a - Reference desk guy (talk) 22:00, 1 November 2008 (UTC)[reply]
See also Micropower, which covers other techniques like microturbines powered by liquid fuel to run electronic devices far longer than batteries can. Edison (talk) 00:43, 2 November 2008 (UTC)[reply]
We do keep hearing of batteries that can be formed like plastics, so the casing of the unit could also be its power supply. But these keep not appearing in commercial products, so seem to be yet another futurologists' pipedream. —Preceding unsigned comment added by DewiMorgan (talk • contribs) 02:58, 2 November 2008 (UTC)[reply]
Do you mean Lithium-ion polymer battery? They can be shaped to fit various weird shapes, although they can't yet replace the casing itself. MaxVT (talk) 17:26, 2 November 2008 (UTC)[reply]
Indeed a simple mobile phone has an excellent battery life (particularly standby), and some people prefer them. For those of us who do like (and use) a colour screen, data connection, camera, music etc of course it's not going to last that long. 1 or more days of continous use is a bit unresonable though we're not talking about Moore's law here, I don't think it's likely battery capacity doubles every 18 months Nil Einne (talk) 08:14, 2 November 2008 (UTC)[reply]
I remember reading an article within the last year or so about some new form of batter that would last years. Unfortunately, that's all I can remember. 67.184.14.87 (talk) 10:39, 2 November 2008 (UTC)[reply]
I very much doubt that's always the case. I'm not even sure it's often the case - why do you ask? What makes you think that's the case? --Tango (talk) 22:11, 1 November 2008 (UTC)[reply]
Body temperature varies during the day, in a regular pattern, both in healthy humans and in humans suffering from a viral infection. Temperature usually goes up in the afternoon, but not at night. Fever article has some information. --Dr Dima (talk) 23:16, 1 November 2008 (UTC)[reply]
Well,the reason I asked is that I have a flu and during the day I always have life 37.2 or something on those measures, but at night it usually goes up to 38.5. —Preceding unsigned comment added by 87.116.154.181 (talk) 23:41, 1 November 2008 (UTC)[reply]
Are you taking paracetamol or anything similar? If so, that ought to lower your fever, in which case when you take the drugs will affect when your fever is at its worst. If you take the drugs as soon as you get up and then regularly during the day, but don't take any at night, that would probably explain what you're seeing. Of course, if the unexplained changes in body temperature persist, you should seek professional medical advice - it could be indicative of something serious (I don't know of any such things, but I haven't spent 6 years in med school, so I can't say for certain that it isn't something serious). --Tango (talk) 23:45, 1 November 2008 (UTC)[reply]
Well, it's simply not true that when you have influenza "body temperature always goes up during the night and you feel worse then during the day": that's the way you're experiencing, but when the diurnal variation of the symptoms of influenza were studied, it was found that 'the average temperature increased during this illness and ... nasal secretion and the temperature increase were greatest in the early morning'. I suppose this might be interpreted as the temperature "going up" during the night. Part of the reason for differences might be that your normal diurnal variation may be different from other peoples. But most people, apparently, have the greatest temperature and worst symptoms in the morning. [6] - Nunh-huh 01:56, 2 November 2008 (UTC)[reply]
your nervous syztem winds down the sympathetic system and fires up the parasympathetic system at night, as you go into rest mode and out of active mode. as a result, your attention is shifted to your internal stimuli, rather than external stimuli in the world. sick people tend to feel more miserable at night. Gzuckier (talk) 16:55, 3 November 2008 (UTC)[reply]
Using cat litter to defuse potency of medicines/pills
Recently, going through my now deceased great aunt's things, her daughter had to dispose of the numerous medicines she was on. (She had cancer if this helps.) She bought cat littler, and put the pills in the cat litter to remove their potency.
I'd never heard of this before. My questions: 1. Why does this work? From reading the article about what it does to the feces, I gather there's some sort of chemical reaction, but am not sure what. And, 2. Is this something that can be done with any medicine? Or just the anti-cancer stuff? Would it work on every kind of drug; could the police place illegal drugs in kitty littlr before disposing of it once it's been used as evidence? (now that I think about it, I would guess they do; they have to do something to it.)Somebody or his brother (talk) 22:30, 1 November 2008 (UTC)[reply]
Cat litter should have negligible impact on most dry, solid medications. Cat litter is sometimes recommended as a way to process liquid medications though. This has more to do with turning the liquids into an unpalatable solid than with actually breaking down the medication. Dragons flight (talk) 23:10, 1 November 2008 (UTC)[reply]
Sounds very questionable to me. Take the pills to your local pharmacy, I'm sure they'll dispose of them for you. --Tango (talk) 23:41, 1 November 2008 (UTC)[reply]
Indeed, pharmacies must have procedures on hand to dispose of expired medications; they would probably add your great aunts pills to the next batch that goes out. I would really recommend that you do that. Attempting to dispose of these on your own is dangerous, and homespun methods of "reducing their potency" seem like a bad idea as well... --Jayron32.talk.contribs 00:37, 2 November 2008 (UTC)[reply]
The US Office of National Drug Control Policy recommends: "Mixing prescription drugs with an undesirable substance, such as used coffee grounds or kitty litter, and putting them in impermeable, non-descript containers, such as empty cans or sealable bags, will further ensure the drugs are not diverted." [7] I think that should be read as "such as used ... kitty litter" - the kitty litter isn't there to do anything to the drugs, it's there to make them unappealing enough to discourage junkies from snagging discarded drugs from the trash and abusing them. Slightly nutty and paranoid, sure, but that's drug control policies these days. -- 128.104.112.72 (talk) 01:11, 2 November 2008 (UTC)[reply]
If memory serves, the official advice in the UK is to take all expired or unneeded drugs to a pharmacy to be disposed of. That page seems to suggest that some pharmacies in the US won't take them. The UK system seems better to me - far simpler (a list of drugs that need to be flushed down the toilet is far too confusing for anyone to actually follow it). --Tango (talk) 01:48, 2 November 2008 (UTC)[reply]
If you let people flush them down the toilet, some news idiot with a need for a story will get someone to do an analysis of the water. Then, they'll find something like 1 part per trillion of Prozac in the water and the next morning's headline will be "City Water is Full of Prescription Drugs including Prozac!" -- kainaw™ 02:33, 2 November 2008 (UTC)[reply]
Actually drugs flushed down toilets appears to be a genuine concern [8]. Also this version of the guidelines 128 mentioned don't say anything about junkies. They talk about pets and children. This one does however [9]. In any case, I agree with Tango. I don't know why the US doesn't just follow what's done in the UK, NZ, Australia [10][11], and large parts of Canada [12] and get pharmacies to deal with expired drugs. (IIRC, last time this came up the consensus was few pharmcies in the US would deal with expired medication and from Googling this appears to be the case) Nil Einne (talk) 07:45, 2 November 2008 (UTC)[reply]
Just speculating, but it may have something to do with the way the DEA tracks scheduled (controlled) drugs. If they expect a "chain of custody" and a full account of all drugs received or distributed, having "stuff somebody brought in" would create discrepancies in the records. For things that don't have addict issues, it's probably set at a state level by a board of pharmacy how they keep track of things. Some references that might be interesting: [ONDCP's recommendations], [rules for a state (Oregon) board of pharmacy]. Just from the standpoint of process control, bringing the medications back into the pharmacy creates a burden of making sure that they don't get mixed up with prescriptions to be issued. Creating opportunities for medication errors is considered harmful. SDY (talk) 10:02, 2 November 2008 (UTC)[reply]
Surely a pharmcy has to keep good track of their medications anyway don't they? It's not as if they have all their medication in one big tin and choose whatever looks good (at least I hope it's not). So it seems to me it doesn't make that much more problem. After all, giving someone warfarin instead of vitamin K tablets is already serious enough. Even if you're talking about the same drugs, I presume pharmcies still often have to keep track of probably more then one quantity of the drug with different expiry dates. In other words, it may add a small risk and yes that risk may be catatrophic, but surely it's only minute unless the pharmcy already has shit systems anyway in which case you have other things to worry about. Drug control wise, sure it does add another element to deal with but are dodgy pharmcies really such a problem in the US. Here the greater concern is with people robbing pharmacies from what I can tell. Nil Einne (talk) 15:01, 3 November 2008 (UTC)[reply]
If you believe that junkie won't consume drugs because they have to weed through cat poop and piss to get them, well, you are sorely mistaken. Drug adicts often do far worse to get a "fix" and, for the kind of person who will hunt through the landfill to get drugs, a little shit and piss is not going to stop them... --Jayron32.talk.contribs 02:41, 2 November 2008 (UTC)[reply]
Think the toilet scene in Trainspotting, but it may make them harder to find at the tip/dump. Next headline: Dumpster baron recycles pharmaceuticals and makes a motza! Julia Rossi (talk) 22:46, 2 November 2008 (UTC)[reply]
My local pharmacy has a sign on the wall about this. It says to remove and destroy all labels, mix liquids with kitty litter or kitchen waste, crush pills and open gelatin capsules, and mix everything together into a nasty mess that is unrecognizable. Then put it in the trash, not the toilet. 134.174.21.5 (talk) 01:42, 7 November 2008 (UTC)[reply]
November 2
Carboniferous
What caused the high oxygen content of the atmosphere in the carboniferous period? 24.77.21.240 (talk) 00:25, 2 November 2008 (UTC)[reply]
Try our article titled Carboniferous period which contains lots of good information. The first reference at the bottom of the article is a link to a journal article titled "Atmospheric Oxygen, Giant Paleozoic Insects and the Evolution of Aerial Locomotor Performance." You could follow that link, or any of the other references, should our article not contain the information you are seeking. As an alternate source, may I suggest that you look in the textbook that your teacher gave you at the start of the class, or perhaps you could review the notes you wrote down the day that your teacher discussed this in class. Cheers! --Jayron32.talk.contribs 00:35, 2 November 2008 (UTC)[reply]
The question is then: What caused the low oxygen content of the current atmosphere? Who burnt so much coal and where is the resulting CO2 (presumably in carbonates)? Maybe subduction and vulcanism (how does coal react in the asthenosphere?). Icek (talk) 14:06, 2 November 2008 (UTC)[reply]
Coal has only been burnt in significant quantities since the industrial revolution, I doubt that's had any noticeable effect on oxygen levels. My guess would be simply an increase in animal life (with the resulting CO2 being dissolved in oceans, stored in carbonates, fossilised, etc.). --Tango (talk) 16:06, 2 November 2008 (UTC)[reply]
No, large-scale burning of coal probably happened in the Permian and many people now think the PETM was coal related as well. Coal can be ignited in situ by volcanism, or where it intersects the surface by wildfires/lightning. Even today, underground coal fires probably represent a few percent or carbon emission, and some coal fires, like Australia's Burning Mountain, have persisted for thousands of years. Though biological processes for dealing with lignin were surely necessary, much of the fall of atmospheric oxygen is thought to be connected to the erosion and oxidation (either by burning or by microbial consumption) of Carboniferous organic deposits during the Permian. Lower sea levels (drying out swampy areas and exposing recently buried organics) and higher volcanism in the Permian helped make that possible.
Oh, and yes scientists do measure the small decline in atmospheric oxygen (ususally expressed as the O2/N2 ratio) since the onset of the anthropogenic burning of fossil carbon. Since the atmosphere is 20% oxygen, the loss of a fraction of 1% isn't a big deal so far. Dragons flight (talk) 16:59, 2 November 2008 (UTC)[reply]
There was natural burning of coal, yes. Since the question was "who" I assumed it was just asking about human burning. --Tango (talk) 18:33, 2 November 2008 (UTC)[reply]
i think we're all off on a tangent here; where did all the oxygen come from, is "plants and cyanobacteria". Gzuckier (talk) 16:58, 3 November 2008 (UTC)[reply]
That wasn't the question, though. The question was what caused the high oxygen content during that time period. I think a fair interpretation of that question is "Why were the oxygen levels higher then than they are now?" --Tango (talk) 16:59, 3 November 2008 (UTC)[reply]
Just to clarify: I am pursuing this for my own interests, and my question is "Why was there more oxygen during the carboniferous than now?" —Preceding unsigned comment added by 24.77.21.240 (talk) 02:50, 4 November 2008 (UTC)[reply]
Geography buffs needed...
<removed> This is not a question. The reference desk does not appreciate being spammed with advertising - even if you're advertising a Wikipedia project. SteveBaker (talk) 15:01, 2 November 2008 (UTC)[reply]
Lovebirds and loneliness
Whilst it's a total myth that Lovebirds will wither and die if kept alone, I was wondering if long-term isolation in these birds is any more psychologically damaging than it is for other species, considering the extremely close social bonds they form and their super-affectionate natures. Anyone know? I'm just thinking about a particular male Peach-faced Lovebird that lives alone in a 30m x 30m aviary at a bird collection near where I live (actually, he *is* the bird collection at present!). --Kurt Shaped Box (talk) 01:44, 2 November 2008 (UTC)[reply]
Actually, most animals, if kept alone and unsocialized, general develop serious psychological problems, often referred to as Stereotypy. The sort of things where you see caged birds plucking all their feather's out, or bears in a zoo repeatedly pacing a small path despite having a large enclosure, are usually the result of the psychological damage done to social animals when they are kept in isolation for extended periods of time. --Jayron32.talk.contribs 02:35, 2 November 2008 (UTC)[reply]
Human children sitting in a foetal position rocking backwards and forwards. --Tango (talk) 13:38, 2 November 2008 (UTC)[reply]
Yeah, I'm (mostly) aware of all the above. I was wondering if Lovebirds specifically were any more susceptible to these problems, given that their entire raison d'être seems to be to stand as close as physically possible to other Lovebirds and snuggle. --Kurt Shaped Box (talk) 21:51, 2 November 2008 (UTC)[reply]
Well, if intervention is required, Christmas is coming up and you might like to give it a present/expand the collection. Maybe it would simply enjoy company in the form of other types of birds instead of rattling around in 302 metres by itself. Is there foliage/rocks, landscaping there as well? Give out a few hints perhaps, in the interest of plumage preservation at least... Julia Rossi (talk) 22:40, 2 November 2008 (UTC)[reply]
Yep, I was actually considering making a donation to enable them to buy some more lovebirds. They used to have loads of them in that enclosure but a combination of financial problems, disease, a lack of hens and the passage of time has significantly reduced the numbers. They've only got three Cockatiels now, in a (different) aviary built for 30 or more (their Zebra Finches are breeding like Zebra Finches, however).
FWIW, the Lovebird looks okay physically and seemed quite content to fly around and swing/gnaw on branches (the aviary has several trees and shrubs within). He comes to the bars and tweets whenever anyone approaches, so I guess that he's feeling somewhat lonely... --Kurt Shaped Box (talk) 22:58, 2 November 2008 (UTC)[reply]
Birds often interact with a mirror in thae cage. If they were humans, they might spend hours editing Wikipedia for a simulation of human interaction. Edison (talk) 03:50, 3 November 2008 (UTC)[reply]
parrots in general are pretty social.Gzuckier (talk) 16:59, 3 November 2008 (UTC)[reply]
pH
why ph value is not greater than 14 —Preceding unsigned comment added by Sush2luv (talk • contribs) 02:00, 2 November 2008 (UTC)[reply]
According to PH#Explanation, it is possible to have a substance with a pH greater than 14 (or less than 0), it's just unusual. There is nothing in the definition that creates an absolute maximum at 14. --Tango (talk) 02:12, 2 November 2008 (UTC)[reply]
Lots of solutions, not all that unusual, have pH's larger than 14 or less than 0. Also, it should be noted that substances can't have a pH, since pH is only measureable as a function of how the substance acts while in a water solution. pH is something which is a function of both of the substance and the concentration of that substance in water. I can, for example, create a solution of Acetic acid which has a lower pH (and this is more acidic) than a solution of Hydrochloric acid, even though acetic acid is a weaker acid than is hydrochloric (it has a higher pKa, or acid dissociation constant, than does hydrochloric).
The source of the 0-7-14 scale, incidentally, is not arbitrary; it has to do with a concept known as the autoionization of water, if you read that article it explains how pH is derived from this... --Jayron32.talk.contribs 02:30, 2 November 2008 (UTC)[reply]
Are you sure you don't have that inequality backwards? --Tardis (talk) 15:56, 2 November 2008 (UTC)[reply]
Nope, pKa is the negative logarithm of the Ka. Thus acids with lower Ka's produce MORE hydronium ions in solution, and thus are more acidic. Lower pKa = higher Ka = more acidic... pKa is often more convenient to work with than Ka because it is then on the same logarithmic scale as is pH... --Jayron32.talk.contribs 18:21, 2 November 2008 (UTC)[reply]
Sorry; I completely ignored the p and decided you were talking about the constants themselves. --Tardis (talk) 03:12, 4 November 2008 (UTC)[reply]
Atmosphere Seperation
Resolved
If there are many different gases in earths atmosphere why do they not seperate? Sediments seperate over time but gases don't seem to. Oxygen is heavier that nitrogen so why should it be mixed? —Preceding unsigned comment added by 202.154.155.124 (talk) 06:42, 2 November 2008 (UTC)[reply]
Perhaps it is due to air currents and air turbulence. Air currents are caused by air temperature differences that result from the sun striking the earth more obliquely toward the poles. Near the equator the warm air rises and returns toward the poles at a high altitude. This has a mixing effect for the gases. Also, mountains, hills, trees, and friction with the ground, all create air turbulence near the ground. Uneven heating of the air over land, sea, desert,and vegetation, also enters into it, causing air currents and mixing. As for sediment, the sedimentary particles have a greater specific gravity than water, resulting in their tendency to settle on the bottom. However, turbulence in rivers causes muddy waters all along the river's course. When the relatively still sea is reached, the particles may settle to create a delta. If there is no delta at the mouth of a muddy river, it is because coastal currents sweep the sediment away. —Preceding unsigned comment added by 98.17.34.3 (talk) 13:59, 2 November 2008 (UTC)[reply]
Gases diffuse into each other readily (technically each one effuses), which leads to mixing even if there weren't externally-driven air currents, because all molecules are always in a state of motion. Actually *all* things do this, but Graham's law explains that lighter particles do so more rapidly. Remember that gases move as individual molecules instead of solids (large aggregates of molecules). Once mixed, there is usually some intermolecular attraction that helps keep them mixed and mixing is favored by the increased entropy. Some mixtures of gases do separate, but it requires that they have a relatively large difference in molecular mass and do not have much if any intermolecular attraction. DMacks (talk) 18:32, 2 November 2008 (UTC)[reply]
For all practical purposes, diffusion is irrelevant to the atmosphere. Atmospheric mixing is totally dominated by wind and turbulence, which is also the reason that the atmosphere stays mixed. Dragons flight (talk) 18:44, 2 November 2008 (UTC)[reply]
So if you take a bit of air and put it in a special container, shielding fully from any turbulence (a kind of perfect container on earth at 1G with no movement in the ground, and fully sealed), will it seperate in layers of different gases after a long period? If yes, do we know how long? --Lgriot (talk) 01:26, 3 November 2008 (UTC)[reply]
For containers of practical sizes and gases at room temperature, there will be a small partial separation: i.e. a little more of the heavy gases at the bottom and little more of the light gases at the top. The diffusion time scale in absolutely still air will be , where l is the characteristic length of the system. After a few times the diffusion time scale one would expect the air to have separated to the degree it is able, but it would not be a big effect. Plugging in large length scales will show how diffusion is so much slower than wind and turbulence when it comes to rearranging air. Dragons flight (talk) 01:48, 3 November 2008 (UTC)[reply]
What is the "characteristic length of the system"? Sorry I am only a curious layman ... Would that be the height in most containers (say a cylinder standing upright)? Also would l be expressed in centimetres like the volume? BTW, I had assumed s is a number of seconds, but now it seems it doesn't make sense, since the number of seconds is what we are trying to find out, so it can't be on the right of the formula. --Lgriot (talk) 00:30, 4 November 2008 (UTC)[reply]
The cm and s in that formula are "centimeter" and "second", not some count of them. l is the original length over which the gases are mixed and can be expressed in whatever units you like, but you have to divide by the units. I personally find it confusing to make the units be part of using the formula rather than part of writing it, but if it helps you can read that formula as "the number of seconds in the characteristic time of stratification is 5 times the square of the number of centimeters long the system is". --Tardis (talk) 03:20, 4 November 2008 (UTC)[reply]
Ok so please correct me if I am wrong: if my container is a standing cylinder with a diameter of 12cm, the number of seconds would be 720 seconds? I still don't understand the notion of "(characteristic) length of the system". I searched for "characteristic length", "length of a system", "length", but that does not give me anything. --Lgriot (talk) 00:42, 5 November 2008 (UTC)[reply]
It's probably easiest to take the diameter of the object as its characteristic length. But by diameter I meant the greatest distance between any two points in it, so how tall is your cylinder? For l=12 cm, your answer is correct. --Tardis (talk) 01:23, 5 November 2008 (UTC)[reply]
Ok, thanks, I understand. --Lgriot (talk) 03:54, 5 November 2008 (UTC)[reply]
what is the use of garlic?
what is the use of garlic? —Preceding unsigned comment added by 59.180.153.7 (talk) 08:16, 2 November 2008 (UTC)[reply]
Antibacterial properties. --Lenticel(talk) 00:47, 3 November 2008 (UTC)[reply]
Stops people from hanging around talking to you for too long. Freshens up the armpits. (And makes things de-licious) Ooh, ooh, roast and put on toast! Franamax (talk) 08:22, 3 November 2008 (UTC)[reply]
In polymer science, what is meant by "an unperturbed chain"?
Thanks —Preceding unsigned comment added by 87.67.14.94 (talk) 11:27, 2 November 2008 (UTC)[reply]
Need Resources - Can you help?
I am studying a scientific degree at the moment but I also have a keen interest in Association Football. Are there any sources of information I can use to find scientific studies of association football, like pubmed for medicine? I am particularly looking for statistical evidences and scientific tactical analyses, or anything like this. Donek (talk) 14:39, 2 November 2008 (UTC)[reply]
Efficacy of multi-sensory room.
I wanted to ask if there are any studies about the effect of these very expensive rooms on children with special needs especially those that approach the vegetable side. My gut feeling about it is that it is an expensive those of hope for the parents but I would like to educate my opinion if possible, thanks.Bastard Soap (talk) 17:02, 2 November 2008 (UTC)[reply]
Discovering intelligent extraterrestrial life
I recall reading somewhere that based off an estimation of the Drake equation and the amount of signals analyzed by SETI, there was a year by which we could hypothetically discover intelligent extraterrestrial life. Does anybody have this figure? Thanks in advance.
QWERTY | Dvorak 17:22, 2 November 2008 (UTC)[reply]
Estimates of the parameters for the Drake equation vary enormously, so any such time estimate is going to be very approximate (and it's just a statistical expectation, not an actual prediction). --Tango (talk) 18:42, 2 November 2008 (UTC)[reply]
In principle - that ought to be a prediction we could make. The Drake equation(s) (there are several variations on the original idea) are a correct statement of how many alien civilisations ought to be 'out there'. All of the variations basically involve multiplying together between half a dozen and a dozen numbers. The trouble it that most of those numbers have HUGE error bars on them. When you multiply numbers with doubt associated with them - the amount of doubt goes up rapidly. Our article points out that any answer between 0.05 and 5,000 civilisations per galaxy is reasonable given 'educated guesses' for the values of the terms that we don't know.
There are terms in the Drake equation like "The number of years between a civilisation starting to broadcast messages to the stars and it's eventual downfall". We have no clue what that number is. Humans are not really capable of broadcasting that far - so the value for that term in the equation might be anywhere between zero and a hundred million years and we have no way to get a more accurate estimate. Since so many of the terms in the Drake equation are as hard to pin down as that one, any use of the resulting number to predict how long SETI might take is similarly vague.
Worst still, (as it's always worth-while pointing out), if you took the most powerful radio transmitter mankind has ever built and put it on the star that's nearest to our sun - SETI's equipment would not be sensitive enough to detect it. The nearest star is only 4 light years away - and radio waves get weaker as a function of the square of the distance. So if there were (say) just a couple of other civilisations in our 100,000 light-years-wide galaxy, then they could easily be 40,000 light years away - using transmitters like ours and producing a signal 100 million times weaker than SETI can detect! So it's perfectly possible that SETI simply isn't sensitive enough to pick up any of the messages that 5,000 alien species are screaming at us every day and from every direction in the sky!
It's also possible that we're somehow searching in the wrong manner. If the aliens habitually use 'spread-spectrum' radio techniques - or communicate with lasers rather than radio waves - then the radio-based SETI search will never find them.
There's no way to get any sort of accurate estimate since we have no idea how common life is, let alone intelligent life. The only thing we can for certain is that in our own solor system, there is only one planet with intelligent life. I'm not sure if it's fair to count Earth because if we didn't exist, we wouldn't even be here to ask the question. Once you exclude Earth, the number of known intelligent civilizations is zero, which puts the result of the Drake equation at zero. We may very well be alone in the universe. 67.184.14.87 (talk) 23:01, 2 November 2008 (UTC)[reply]
I read somewhere "I think a true sign that intelligent life exists somewhere else is that we havn't been contacted." —Preceding unsigned comment added by 202.154.155.124 (talk) 04:46, 3 November 2008 (UTC)[reply]
Is this where you read it? —Angr 12:42, 3 November 2008 (UTC)[reply]
I think it's FAR too soon to assert that we are the only intelligent species in the solar system. There is plenty of scope for creatures living in the deep oceans under the ice of Europa - or on Titan. The only thing we know for sure is that if they ARE intelligent, they either cannot or choose not to transmit powerful, distinct radio signals at us and they do not build huge, visible cities. If a civilisation of water-dwelling creatures lived on Europa, they would be unable to see the sky or the stars because of tens of kilometers of ice over their heads. They would perhaps not have invented telescopes - never have realised that there is anything above the ice - and certainly never have tried to transmit message through it. That doesn't mean they couldn't be intelligent and have a rich and interesting society.
That's the problem with the Drake equation - we don't know the very first thing about what is or is not possible in terms of life...let alone intelligent life...let alone intelligent life with big-assed radio transmitters and a curiosity about life elsewhere. SteveBaker (talk) 19:15, 3 November 2008 (UTC)[reply]
Viscous hot water
Why does boiling water sound more "viscous" or "thicker" when you pour it than cold water? —Angr 18:44, 2 November 2008 (UTC)[reply]
I'm not sure about "sound" but every other fluid that comes to mind is more viscous at lower temperatures. You could try the Viscosity article, but it is simply an atrocious violation of WP:MTAA. SDY (talk) 20:32, 2 November 2008 (UTC)[reply]
Well, there's a reason I put "viscous" in scare quotes. I'm not saying it is necessarily actually more viscous by the scientific definition, just that when you pour just-boiled water from a tea kettle into a teacup, the sound the water makes is somehow "thicker" than if you pour cold water in. —Angr 21:10, 2 November 2008 (UTC)[reply]
I guess so, yeah. I'm sorry I'm not being very scientific about my description; I was hoping this was such a well-known phenomenon everyone else would know what I was talking about. Am I the only person here who has noticed for his entire life that very hot water sounds different when it pours than cold water? —Angr 21:58, 2 November 2008 (UTC)[reply]
Hot water has a lower density than cold water; so it makes sense that hot water would have a different resonant pitch than cold water would... --Jayron32.talk.contribs 23:14, 2 November 2008 (UTC)[reply]
Pouring very hot water into a container brings the liquid into contact with a (microscopically) rough surface, encouraging the formation of bubbles of water vapour. The formation and rapid collapse of these bubbles probably alters the sound. (I'm not sure that density differences in the liquid could account for the change in sound; water is only about 3% less dense at 95°C than at 4°C.) TenOfAllTrades(talk) 23:31, 2 November 2008 (UTC)[reply]
This thought actually occurred to me the other day and with a bit of Googling I found out that water is actually less viscous at higher temperatures, so the sound it makes is different. One source claimed the viscosity fell of particularly quickly close to boiling point, but our Viscosity article seems to suggest a linear relationship. Either way, my understanding is that it's this decrease in viscosity that results in the difference in sound between pouring hot water and pouring cold water. Maelin (Talk | Contribs) 01:49, 3 November 2008 (UTC)[reply]
Okay, then it's just my subjective impression that hot water sounds "thicker" even though actually it's less viscous. It makes sense that water that's about to become steam would be less viscous than water that's about to become ice. —Angr 06:25, 3 November 2008 (UTC)[reply]
i know what you mean; it makes more gloopy noises. i think it's because cavitation is more pronounced near the boiling point, and that's what you/me are hearing. Gzuckier (talk) 17:05, 3 November 2008 (UTC)[reply]
ZENN electrical motor
What type of AC motor is in the ZENN? Is it a wound rotor, squirrel cage, synchronous or switched reluctance motor? I believe the motor is made by Advanced Motor & Drives, p/n ACX-2043. --jcmaco (talk) 20:58, 2 November 2008 (UTC)[reply]
According to your link at environmentalmotors, it's a "3 Phase AC motor by Advanced Motors & Drives -- ACX 2043". That's an interesting method, since it's powered by a DC battery / ultracapacitor. I'm not sure why someone would build a 3-phase inverter into the powerline, rather than use a straight DC motor. We had a thread a little while ago here about why lawnmowers rectify single-phase AC to DC - and I wasn't all that clear on why they did that either. I made a small chase, because I had thought that AC motors developed more torque than DC, but my ship ran onto the rock of hard numbers. AM&D claims their designs to provide exceptional torque.
In any event, the AM&D website discusses their "standard AC motors" and various brush features. This sounds to me very much like a wound rotor. The site also prominently invites you to make direct contact, so that may be the best way to go.
The ZENN website may have info but I bailed out of it - someone decided that the best paradigm for web users used to clicking through pages was to introduce the concept of a "book" that you have to click-hold-drag the pages of, just so you could read their wonderful story, like Daddy used to tell you. OMG that's bad!
They're both pretty small companies, a direct approach might be best. Please report back here with any results! Franamax (talk) 08:17, 3 November 2008 (UTC)[reply]
Organic Functional Group Interconversion
Is there a simple way to convert a phenol group to a phenyl bromide? For a general example, can toluene be converted to bromobenzene? For a more specific example, can p-hydroxyaniline be converted to p-bromoaniline? Somehow I think that it's not possible, especially with an NH2 group activating the benzene ring, but I was just wondering. --Russoc4 (talk) 21:54, 2 November 2008 (UTC)[reply]
Larock lists a dozen refs for "ArOH→ArX", all involving things that could be considered strong electrophiles/Lewis acids. Looks like lots involve transiently deriving the OH into a leaving group, not sure if they formally would go by addition–elimination or elimination–addition. Your question is kinda weird though…there's no phenol in toluene (did you mean "phenyl"?) and where did the methyl of toluene go in the bromobenzene you expect to get? But for the very specific case you mention, wonder if reduction to aniline then very simple p-selective electrophilic aromatic substitution to get the halogen? DMacks (talk) 02:06, 4 November 2008 (UTC)[reply]
Library scanner things
When entering or leaving the library, when I walk through those things that scan to see if you're stealing books, and I'm wearing my iPod, there is a sudden intense squealing in my ears. If I take the earphones out of my ears before passing through, then put them back in on the other side, I hear no such thing. What causes this? Is it in any way damaging to my iPod? Cherry Red Toenails (talk) 22:56, 2 November 2008 (UTC)[reply]
From our article on Electronic article surveillance, I notice that these devices work by emitting radiowaves at certain frequencies. Maybe this is what you are hearing. Nanonic (talk) 23:03, 2 November 2008 (UTC)[reply]
I'd be more worried about your ears then your iPod. If you did want to worry about some object that isn't part of you, I'd worry more about the earphones Nil Einne (talk) 11:27, 3 November 2008 (UTC)[reply]
I didn't ask about my ears for fear of bringing down the "NO MEDICAL ADVICE" vultures. =P I thought asking about the iPod might give me a clue though. And I figured it was some kind of electromagnetic thing, but wasn't sure what. The article you suggested helped though, thanks. Cherry Red Toenails (talk) 16:32, 3 November 2008 (UTC)[reply]
I don't think you need any medical advice beyond common sense - if the sound hurts your ears, take the earphones out before going through. If it doesn't hurt, then it probably isn't any worse than all the other loud noises you are exposed to on a regular basis, especially since it lasts a fraction of a second. --Tango (talk) 16:38, 3 November 2008 (UTC)[reply]
if it is that loud, i would worry about generating high voltage/currents in circuits such that the ipod isn't designed for, possibly frying something in the Ipod; but if it didn't actually fry it, then i'd stop worrying. Gzuckier (talk) 17:07, 3 November 2008 (UTC)[reply]
In case of a very high ferritin value (900+) for a long period of time (year+),not due to iron overload (ruled out by transferrin/iron), is there a list of possible diseases?
I understand high ferritin+ESR+CRP is a "nonspecific inflammation", but is there a protocol for treating this?
Mathityahu (talk) 00:34, 3 November 2008 (UTC)[reply]
No. Longstanding elevated ferritin in the absence of hemochromatosis is a marker of a chronic disease. The health carers would aim to diagnose and treat the underlying disease. Axl ¤ [Talk] 07:27, 3 November 2008 (UTC)[reply]
Biological Condition of Not Being Able to Sing
I once read, while studying for my music degree, that there is a rare condition that precludes an individual from the ability to sing. I cannot recall the name of that condition and would like to know what it is so that I can research it and learn more. I believe, for the most part, that if you can talk you can sing and would like to research this "rare condition" further. My clouded memory gives me the word "amesia" for the, but I cannot find that word in Wikipedia or any other dictionary that I have checked, so assume it is probably
not the correct word. Does anyone know more? I have hit a dead end in my research on the web.Kschwacog (talk) 01:18, 3 November 2008 (UTC)[reply]
Note that amusia is an inability to mentally process music, not really a physical problem with the voice that precludes the ability to sing. Being monotone could be a result of amusia (the person can't hear notes, so doesn't produce them). It is also a result of lack of voice control - with many possible causes. A rather famous example is Julie Andrews. After throat surgery, she claimed to have lost the ability to sing. -- kainaw™ 03:09, 3 November 2008 (UTC)[reply]
<meow>You can't lose what you never had.</meow> —Angr 09:53, 3 November 2008 (UTC)[reply]
We are not amused. Edison (talk) 03:46, 3 November 2008 (UTC)[reply]
I was half expecting that the one-word answer to "not being able to sing" would be "Franamax". In fact, I'd propose it as an alternate definition... Franamax (talk) 07:46, 3 November 2008 (UTC)[reply]
Franamax has raised the issue of someone who knowingly can't sing (taking you at your word here). Does an "amusia" type realise the problem, ie, can hear music but can't sing it? Hope you know what i mean. Sorry Kainaw, you got it and variations. Julia Rossi (talk) 10:32, 3 November 2008 (UTC)[reply]
Stephen Fry has written that, although he can hear music vividly in his mind, when he tries to sing nothing comes out. You might ask him ;) —Tamfang (talk) 17:04, 3 November 2008 (UTC)[reply]
Our article on Tone deafness notes, "Being tone deaf is having difficulty or being unable to correctly hear relative differences between notes; however, in common usage, it refers to a person's inability to reproduce them accurately. The latter inability is most often caused by lack of musical training or education and not actual tone deafness." In colloquial usage, the inability to reproduce musical tones is often called "tone deafness"; though this colloquial usage is generally unrelated to the real medical condition called amusia. --Jayron32.talk.contribs 17:14, 3 November 2008 (UTC)[reply]
'Intensity' of dreams
Why is it that dreams are far more intense/realistic/emotional than real life? ie why can you experience far more pleasure/fear/happiness in dreams than in waking life?--GreenSpigot (talk) 02:26, 3 November 2008 (UTC)[reply]
Perhaps because your "dream senses" are not distracted by external stimuli so they are completely devoted to the sensations that your dream provides. Besides, the suspension of disbelief is over the top in dreams unless you learn how to snap out of it.--Lenticel(talk) 02:57, 3 November 2008 (UTC)[reply]
(edcon)For some of us, it's the opposite though this[13] in the article says anxiety is a common feature of dreams. That could also depend on age and development, and personality. Julia Rossi (talk) 03:00, 3 November 2008 (UTC)[reply]
It is not a given or accepted conclusion that dreams are in fact more intense, realistic, or emotional than real life. In the rare cases when dreams are remembered in detail, they may be related to the day's actual experiences, as those experiences are related to previous experiences and desires. Edison (talk) 03:46, 3 November 2008 (UTC)[reply]
I haven't remembered a dream in quite a few years, and even the one I did remember then was quite prosaic and uninteresting. So I'd have to dispute your assumption, maybe for some they are bright and vivid but for others they aren't. Dmcq (talk) 13:03, 4 November 2008 (UTC)[reply]
cognitive power of a feline
a domesticated cat sees a kitchen counter. It knows to get on that counter it must jump. Once the cat is on the counter can it determine that BECAUSE it jumped it is on the counter? Thanks, 32.149.68.21 (talk) 03:16, 3 November 2008 (UTC)[reply]
My cat won't jump on the counter normally. However, if he smells ham, he jumps on the counter and eats the ham (until required to stop). I'm not able to say whether he KNOWS he is on the counter BECAUSE he knows he jumped or BECAUSE he knows he is now able to eat the ham. He certainly know that jumping on the counter is a prerequisite to eating ham. CBHA (talk) 04:28, 3 November 2008 (UTC)[reply]
The question is unanswerable, because we have no way to "see" into a cat's cognitive processes. What allows us to understand what Humans are thinking is that they can tell us. Language allows one to describe ones own thought processes. As yet, no cat has ever explained their behavior to us... --Jayron32.talk.contribs 13:29, 3 November 2008 (UTC)[reply]
The real question is why my cat keeps drinking the dirty water out of my dishes in the sink, when he's got a nice bowl of clean water next to his food? -- MacAddct1984(talk • contribs) 15:32, 3 November 2008 (UTC)[reply]
Oh, that's easy. "Wild" water that you find always tastes better than the domesticated water your human puts out for you. Every cat knows that. —Angr 15:42, 3 November 2008 (UTC)[reply]
yeah, cats prefer yucky water. i also find that the more disgusting their cat food is, the more they like it. Gzuckier (talk) 17:09, 3 November 2008 (UTC)[reply]
Seeing my black cat curled up on a black blanket, I wonder whether anyone has experimented to see whether cats are aware of their own color and the availability of camouflage, e.g. by letting black cats and white cats choose favorite spots in a room whose walls and floor are half white and half black. —Tamfang (talk) 17:15, 3 November 2008 (UTC)[reply]
That's strange. The cats I've had usually prefer spots where they are the least camouflaged, so that the hair they leave behind is maximally visible. In other words, black cats should prefer white sofas and rugs, and vice versa. —Angr 18:42, 3 November 2008 (UTC)[reply]
Yes - but that's just their natural tendency to wish to modify their environment. Rolling around on a white rug while shedding fur is a sure way to convert the annoyingly contrasty rug into something that's a PERFECT match for one's own fur - and therefore a great place to be camoflaged. SteveBaker (talk) 18:58, 3 November 2008 (UTC)[reply]
Or it could be that they are "marking their territory" which would show a preference for non-camoflaged backgrounds... The better the contrast, the more their fur is likely to stand out, and announce to the world "This is my territory, and all the females you find here belong to ME". That could be a good genetic survival strategy in and of itself, no? --Jayron32.talk.contribs 06:00, 4 November 2008 (UTC)[reply]
I'll put a white blanket on my bed and see what happens. —Tamfang (talk) 03:08, 4 November 2008 (UTC)[reply]
You'll have to put a black blanket on as well (if there isn't one already), to eliminate the fact that your cat just prefers the blanket instead of the bed. -- MacAddct1984(talk • contribs) 18:25, 4 November 2008 (UTC)[reply]
You'll need to blindfold yourself when you put the two blankets out or this won't be a double-blind experiment. The cat can't be allowed to know that you'd much prefer it to sleep on the dark blanket. SteveBaker (talk) 20:43, 4 November 2008 (UTC)[reply]
I can fold the blankets so that the bed is half-and-half; but it's trickier to arrange things so that he has a choice on the foot of the bed, his favorite spot. —Tamfang (talk) 17:19, 5 November 2008 (UTC)[reply]
Lizard Question
Do lizards lay eggs from which baby lizards hatch, or do lizards give birth to live babies, or do some approach the question of reproduction one way and some the other? CBHA (talk) 03:44, 3 November 2008 (UTC)[reply]
How many video game references can you find in the Arecibo message?
How many video game references can you find in the Arecibo message? In the middle, there's a blue and white guitar from Guitar Hero. Below that is the human in Berzerk. Finally, at the bottom is one of the space invaders. 67.184.14.87 (talk) 04:15, 3 November 2008 (UTC)[reply]
The red dude who has fallen into a hole in the white platform is from Lode Runner--that makes it only 10 years impossible to be what it actually represents instead of 30:)DMacks (talk) 05:35, 3 November 2008 (UTC)[reply]
Oops, thought we were still talking about Guitar Hero, not Berzerk...completely forgot about that game! DMacks (talk) 05:50, 3 November 2008 (UTC)[reply]
charging objects..
I have been given an assignment. 8 point electrical charges are placed at the corners of a cube and another point electrical charge is placed at the centre of the sphere. I have to experimentally show that the 9th electric charge will not be in stable equilibrium. I have a theoretical explanation for that using Gauss's law. To do it experimentally, I thought I will use charged (conducting)spheres as point charges. I can charge a sphere using induction method. Is there any other way to charge a sphere?Please help. Also, suggest some ways to place the spheres at the corners of a cube. —Preceding unsigned comment added by 210.212.187.69 (talk) 04:28, 3 November 2008 (UTC)[reply]
without having the gumption to work on it, my instinct is to start with 1/rsquared being countered by the cosine of the angle between the middle point and the corner point and the middle point and the center of the side. i have no idea whether that will get you the right answer or even in the general direction of the right answer. Gzuckier (talk) 17:13, 3 November 2008 (UTC)[reply]
He/she has already solved the theoretical problem—the question is about actually doing the experiment. -- BenRG (talk) 21:18, 3 November 2008 (UTC)[reply]
Ahh, you're talking about electrical charges. When the original question opened with setting charges at the corners of a cube, I thought y'all were trying to blast your way into a vault or something. (How can the charge in the center of the sphere be unstable if you're going to blow the whole thing to smithereens anyway.....)
Good thing I wasn't the first person to try to reply! --DaHorsesMouth (talk) 23:08, 3 November 2008 (UTC)[reply]
This will sound weird, but what do you mean by "seen"? You can see DNA with the naked eye if you have enough, but it would just be some whitish goo. On the chromosome article, you can see a micrograph of chromosomes, which we know are each a double strand (essentially 2 molecules of DNA, with some other structural components) but all you can see is their overall shape. To see evidence of the helix or base-pairs, I think you'd need X-ray crystallography or a similar "not direct visualization" technique. DMacks (talk) 06:14, 3 November 2008 (UTC)[reply]
Let me rephrase it, are there microscopes that can magnify until the DNA looks like the way it's pictured in illustrations? DahiJynnuByzzuf (talk •
Again, it depends how detailed an illustration you mean (sort-of-elongated-thing, helix, ladder-rungs, actual sugars and bases and atoms, etc.). If you mean a specific type, would be helpful for us to be able to see "what you really mean" specifically (maybe a URL or image from a wikipedia page?). See above where I gave several answers for several levels of detail. DMacks (talk) 09:30, 3 November 2008 (UTC)[reply]
Hasn't Dmacks already answered that question in the first post? The answer is no Nil Einne (talk) 11:00, 3 November 2008 (UTC)[reply]
No, but the second best thing, seeing the chromosomes as they'r commonly depicted in textbooks, is sortof possible. See picture.EverGreg (talk) 12:13, 3 November 2008 (UTC)[reply]Mitosis of a cell. The blue strings are chromosomes. Probably pictured using confocal microscopy or some other Fluorescence microscope.
An ordinary light microscope can't possibly 'see' things that are smaller than roughly the wavelength of the light they are using...which is around 500 nanometers. A DNA molecule is around 2 nanometers wide - each "rung" in the ladder is only 0.2 nanometers long - but there are 200 million of them in just one chromosome. So an entire chromosome is 200,000 nanometers long - but only 2 nanometers wide. So clearly, you can't see the molecule as a little twisted ladder in a light microscope - but DNA molecules are twisted and coiled many times over - so an entire DNA molecule ought to be just about visible in the best light microscope you could imagine. However, in a 'typical' light microscope - you won't see a thing.
A 'transmission' electron microscope (TEM) uses teeny-tiny electrons instead of big fat light waves - so a really good one can just about see things about 1 nanometer across. Most are not that good. So even in the best TEM won't see enough detail to see a spiral ladder. At best, you get a two-pixel wide spiral with rungs that are far too small to see.
A 'scanning' electron microscope (SEM) can see individual atoms - but only under special circumstances - such as when they are in 'bulk' form. Picking out a single strand of DNA is not the kind of thing they do well.
So the answer is "No". Sorry! SteveBaker (talk) 18:53, 3 November 2008 (UTC)[reply]
Calcium Bicarbonate does not exist in solid form, therefore these must be fake right? —Preceding unsigned comment added by 72.130.237.183 (talk) 07:18, 3 November 2008 (UTC)[reply]
Someone suggested their gelatine balls. Whatever the case, the person is either bullshitting or confused. Going by the comments, I'm really not sure but leaning towards bullshitting Nil Einne (talk) 10:54, 3 November 2008 (UTC)[reply]
Actually considering how many people are repeating the same thing, I'm guessing this is some sort of dumb joke aimed at people who don't know chemistry hoping to get them to waste time and make a fool of themselves by looking for calcium bicarbonate. The premise is nonsensical anyway. How can you claim they are water balls when you dumb so much crap into the water to get the balls? Nil Einne (talk) 13:18, 3 November 2008 (UTC)[reply]
Why do lovebirds cuddle up to each other?
Is it only the bird that they're in a relationship with that they cuddle up to or do lovebirds just like to get close to each other in general? --90.240.85.78 (talk) 08:18, 3 November 2008 (UTC)[reply]
Well, not clear but the article says, Lovebirds "are a social and affectionate small parrot," happy to preen their favourite (human) people and "the name Lovebird stems from these parrots' strong, monogamous pair bonding and the long periods of time in which paired birds will spend [sitting] beside one another." Small flocks a speciality too. So it looks like they are socially friendly but cuddly to close companions. Julia Rossi (talk) 10:42, 3 November 2008 (UTC)[reply]
Power 8
I have just come up with the term "Power 8" in Airbus article. I did not find any article regarding Power 8. What is meaning of power 8? Thank you--202.168.229.245 (talk) 09:28, 3 November 2008 (UTC)[reply]
According to Airbus#2007 restructuring it's Airbus's hip-sounding name for a plan to lay off thousands of workers and sell or close three plants. —Angr 09:49, 3 November 2008 (UTC)[reply]
Why do plants use chlorophyll?
Why do plants use chlorophyll which is a green pigment? Wouldn't it be more useful to use a red pigment so that red light, which is of a high wavelength and thus low energy, is the only light not used? Taking it further, couldn't they use a black pigment? Are there any reasons or theories for why chlorophyll is used? --RMFan1 (talk) 12:03, 3 November 2008 (UTC)[reply]
I think it's because of what wavelengths the sun is brightest at. I don't know the details. --Tango (talk) 12:22, 3 November 2008 (UTC)[reply]
With evolution it's always very difficult to answer 'why'. It could be just chance. Remember evolution doesn't have a set goal or intelligence. It doesn't know what's best. These speculations [20][21] may interest you. This Yahoo answer [22] is rather good too IMHO. My gut feeling is it would be difficult for a pigment to absorb the entire spectrum (it's obviously possible but it's not so easy for it to happen by pure chance). Very likely, any change to absorb more in the green area would reduce absorption in the blue region which will likely make the plant less efficient. You could use a different pigment (and plants do have different pigments) but this adds another layer of complexity and cost to the plant (remember as well the pigment may compete against the existing pigments to some extent) so unless the tradeoff with having this new pigment makes up for itself, it's not likely to survive. But particularly if this new pigment arises late in the game, your existing pigments are already good enough that it's not easy for this new pigment to provide an advantage to the plant. Remember as well that you need to use the energy effectively, if your just absorbing it but not converting it to chemical energy you just end up with a hot plant. However this is just idle speculation, it's one of the many things we will probably never know why Nil Einne (talk) 13:08, 3 November 2008 (UTC)[reply]
You may also be interested in [23] which has the absorption spectra of various pigments Nil Einne (talk) 14:46, 3 November 2008 (UTC)[reply]
The photoelectric effect implies that chemical reactions involving light can't just use any frequency it likes. If the energy needed to liberate an electron equals say, the yellow wavelength, no amount of red light will do. Similarly, blue light might excite electrons at other places in the process that should not have been excited, ruining the chemical reaction. When taking efficiency of the process into account or what building blocks it requires, chlorophyll might come out on top. (Chlorophyll by the way comes in different types that absorbs different wavelengths) The issue is not settled though, according to [24] which speculates that chlorophyll might have been a historical accident from when algae competed against green-absorbing organisms in the ocean. EverGreg (talk) 14:03, 3 November 2008 (UTC)[reply]
earthworms
I want to now how does the earthworms eat? —Preceding unsigned comment added by 204.108.96.22 (talk) 15:59, 3 November 2008 (UTC)[reply]
Our article on earthworms has some sentances about this, in the "anatomy" section. There is also a bit in the section "Locomotion and importance to soil". Also, the earthworm article contains links to many more articles about specific families of Earthworms; there is may be more details in those articles if you do some snooping around... --Jayron32.talk.contribs 17:06, 3 November 2008 (UTC)[reply]
Preventing inbreeding among critically endangered animals
I read,via a featured yahoo article (here [25]), about the rare sighting and photographing of a Far Eastern Leopard (i.e., the Amur Leopard) wherein concern was expressed on the matter of probable genetic defects arising due to inbreeding among the critically low population of Amur leopards. What methods could/do the scientists use to prevent these defects when attempting to revive the population of a critically endangered species?--Leif edling (talk) 17:19, 3 November 2008 (UTC)[reply]
You could do selective breeding and perhaps some sort of 'genetic compatibility testing' (similar to the way Genetic testing is sometimes used to test for compatibility of couples in some small ethnic groups e.g. [26]). If you want to go ever further, you could use in vitro fertilisation coupled with preimplantation genetic diagnosis. Trouble is, these methods are rather labour intensive (particularly if the population is over a resonable large range) and require you to regularly interfere in the wild population (not something you want to do when there are few members left). In particular, the first method requires you to either intefere in mate choice somehow or to use artifical insemination (and hope other males, e.g. the female leopards well mate, don't kill the offspring or more successfully inseminate the female then you). The second method, presuming you don't want to subject the female to prolonged captivity, requires you to capture the female several times and hope the female doesn't get inseminated before you extract the unfertilised eggs (actually I wonder if you might have no choice but to hold the female, at least for a few days when she nears her period of fertility). Also, presuming you follow the system used in humans of using more embryons then would normally occur to increase the odds, you run the risk of killing the female unless you find a way to interfere in her giving birth if necessary (which carries its own risks). Even then, I suspect you'd still likely have low odds of success requiring you to repeat the process several times. Plus there's still the problem of how males will react (edit: I see from the article there are only 20-30 left in the wild, I presume then they are largely solitary, if the male mate doesn't hang around at all then this shouldn't be an issue). I've never heard of anyone seriously propose these methods except perhaps for breeding captive animals (perhaps for the eventual reintroduction into the wild). I believe the Chinese are doing some stuff with Pandas, but that's more about actually getting them to breed I think and only with ones in cativity. In any case, our best bet is to just prevent this happening in the first place (yes I know this doesn't help with the Amurs). Nil Einne (talk) 17:50, 3 November 2008 (UTC)[reply]
N.B. These problems will be lessened somewhat if you capture and hold your subjects in captivity rather then allowing them to stay in the wild, but this brings its own problems and is likely to be extremely controversial. Also, I read in the Amur Leopard article that there are existing Amur leopards in captivity and these would likely already be selectively bred but I doubt there's much support for bringing any of the wild specimens into play. The only (remote) possibility IMHO is males could be tranquilised and sperm samples taken and this used with the ones already in captivity. Nil Einne (talk) 17:54, 3 November 2008 (UTC)[reply]
Also, captive breeding programs can introduce problems when there is TOO much "genetic diversity" in the breeding population. C.f.orangutans. Early captive breeding programs focused on genetic diversity by interbreeding different populations of orangutan; later genetic studies showed that these populations were likely seperate species, so it called into question the viability of the "crossbreed" orangutans; the different populations were likely different enough to be uniquely adapted to their seperate environments, and it was determined that releasing the hybrid orangutans back into the wild was too risky. The population of orangs at the National Zoo in Washington, D.C. consist of these hybrids; they are currently part of the National Zoo's primate language lab... --Jayron32.talk.contribs 02:17, 4 November 2008 (UTC)[reply]
Is there a difference between emperical evidence and observational evidence?
Is there a difference between emperical evidence and observational evidence or can these terms be used interchangeably? 216.239.234.196 (talk) 18:25, 3 November 2008 (UTC)[reply]
I'd say they were interchangeable. --Tango (talk) 18:29, 3 November 2008 (UTC)[reply]
I smoke Marijuana daily. After voting tomorrow, I intend to give blood. Will the THC in my blood cause my donation to be discarded? --Unshelled Peanuts (talk) 18:30, 3 November 2008 (UTC)[reply]
In some countries, you are told not to give blood if you take illegal drugs, even those that are smoked or taken orally. If you take such drugs nasally or intravenously, most countries will have rules that say you shouldn't donate blood. I'm not aware of any country where blood centers test the blood for THC or other drugs. --NorwegianBluetalk 19:02, 3 November 2008 (UTC)[reply]
This says it's acceptable, at this particular institution, "as long as you are not under the influence of marijuana at the time of donation". It may well vary at other centres both nationally and internationally. —Cyclonenim (talk · contribs · email) 19:04, 3 November 2008 (UTC)[reply]
Some people's blood is thrown out automatically anyway, even if they don't take drugs. —Angr 19:09, 3 November 2008 (UTC)[reply]
How is that relevent to the question? It'll probably just spark debate. —Cyclonenim (talk · contribs · email) 19:13, 3 November 2008 (UTC)[reply]
I am quitely pondering the contact high for the guy who receives this blood later on... For some reason, the idea is mildly amusing to me... --Jayron32.talk.contribs 19:42, 3 November 2008 (UTC)[reply]
Not as inexplicably mildly amusing as the recipient would find:) DMacks (talk) 01:57, 4 November 2008 (UTC)[reply]
Maybe I had a blood transfusion recently... Maybe that explains my mild amusement... --Jayron32.talk.contribs 02:05, 4 November 2008 (UTC)[reply]
It might also explain forgetting that you had a transfusion recently. —Tamfang (talk) 04:35, 4 November 2008 (UTC)[reply]
Generally, though, if the blood bank doesn't ask a question about illicit drug use in general (not specifically IV drugs), they didn't care about it in the first place and won't throw out the blood. THC and marijuana consumption are not considered to be "of interest" for blood safety, the only drugs that are always a concern are IV ones (since that's an infection route for HIV and hepatitis). Some blood banks have stricter policies, but they're not recommended (at least by any guidelines I've seen). If you're too stoned to give a straight answer or remember what else you might have done, that might be a problem, but the same is true for alcohol. SDY (talk) 22:37, 4 November 2008 (UTC)[reply]
Why Earth's rotation slows down?
I was just reading about how leap seconds are added to the UTC time because Earth's rotation is slowing down. Has this been happening since the Big Bang or does it increase and decrease in cycles? If not a cycle, wouldn't Earth eventually stop rotating? Elfalem (talk) 20:16, 3 November 2008 (UTC)[reply]
Currently the spin rate changes due to friction of tides. The angular momentum is transferred to the moon. This slowing probably started when the moon was created and would have been happening ever since. The Moon would once have been much closer to the earth, with a day only lasting a few hours. Eventually when the day is as long as a lunar month the moon and earth will be tidally locked and there will be no more effect from this. The sun however also causes tides that slows down the earth's spin too. Graeme Bartlett (talk) 20:40, 3 November 2008 (UTC)[reply]
As for "stop rotating", it depends on what your frame of reference is. Consider the moon which, being tidally locked, is a useful illustration of what Earth would eventually act like. To an Earth-bound observer, the moon appears not to rotate (only one face is ever shown). However, if you were to take an extraterrestrial top-down viewpoint, you'd see that the moon actually has one rotation per orbital revolution. The Earth is likewise moving towards such an end state. — Lomn 20:54, 3 November 2008 (UTC)[reply]
Actually, I think most of the slowdown is due to post-glacial rebound, the land that was weighed down by glaciers is rebounding which moves mass away from the centre of rotation. Just like putting your arms out while spinning on the spot, that slows down the rotation. Tidal friction does slow the Earth's rotation, but very slowly. --Tango (talk) 21:22, 3 November 2008 (UTC)[reply]
I've done some calculations (feel free to check my maths) - the current rate of slowing is around 1.7ms per century. Even rounding to to 2ms per century in the approx 5 billion years life of the Sun the earth will only have lost just over 50% of it's rotational speed (my calculations give a result of a day of 52 hours or so) - so no, the earth will not 'stop' rotating in it's lifetime - it will be swallowed by the Sun before that. Exxolon (talk) 00:08, 4 November 2008 (UTC)[reply]
Hmm - further calculations. Currently the earth takes 86,400 seconds to rotate one revolution. At the 1.7ms slowdown per century my calculations indicate it will take over 5 TRILLION years for the earth to stop rotating. Exxolon (talk) 14:15, 4 November 2008 (UTC)[reply]
Leap-seconds are subtle. We don't need them because "earth is slowing down." We need them because earth has alraedy slowed down since the date at which we defined the second. If the earth were to suddenly quit slowing down and remain at its current rotational rate, we would still need leap seconds: as a clock, earth is running a bit slow. To keep in sync, we need about one leap second every 18 months. Since earth continues to slow down, leap seconds will become more frequent. -Arch dude (talk) 14:46, 4 November 2008 (UTC)[reply]
The universe is 13.8 billion years old. The Earth is 4.5 billion years old. I think it's safe to say that the Earth has not been slowing down since the big bang. — DanielLC 16:21, 4 November 2008 (UTC)[reply]
Are there any legitimate scientific alternatives to evolution?
Are there any legitimate alternative scientific explanations to evolution? For example, for the causes of global warming, solar variation is a legitimate alternative scientific hypothesis. Are there anything similar alternatives to evolution? 216.239.234.196 (talk) 20:48, 3 November 2008 (UTC)[reply]
I don't like to respond to one question by asking another but I think it important in this case to ask: What do you mean by "legitimate?
For example, do you mean:
It seemed plausible when first considered, but did not stand up to serious scrutiny?
It seems plausible even after serious consideration, but has been shown to be incorrect?
It is a thoroughly "respectable" theory that has not been disproven, and provides as good an explanation of the known facts?
The question is akin to asking "Are there any legitimate alternative scientific explanations to the motion of the sun in the sky?" Sure, at one point in history, people believed that the sun moved around the earth. Evolution is such a basic concept, it is no less accepted than is the heliocentric solar system is. --Jayron32.talk.contribs 21:31, 3 November 2008 (UTC)[reply]
A key point to make about evolution is that it isn't just a way of explaining observations, it's a logical consequence of life as we know it. If you have lifeforms that reproduce in a way that has a possibility of random mutations (which we do, there's no real doubt about that bit), then evolution is going to happen, it's obvious. The only question is whether or not evolution is sufficient to explain the variety and complexity of the lifeforms we observe. As for alternative answers to that question, I've never heard of any that would qualify as scientific (ie. falsifiable, fit observations and aren't so extremely complicated and unlikely that Occam's Razor rejects them without a second thought). --Tango (talk) 21:32, 3 November 2008 (UTC)[reply]
(I'm the OP on a different PC) If it helps, if you look the global warming article, it states:
"Some other hypotheses departing from the consensus view have been suggested to explain most of the temperature increase. One such hypothesis proposes that warming may be the result of variations in solar activity."
I'm just wondering if there are any competing explanations to evolution, even if not accepted by the consensus of current scientists. 67.184.14.87 (talk) 22:40, 3 November 2008 (UTC)[reply]
I'm pretty sure the answer is "no". There are variations on the theory, but I don't think anyone has suggested anything significantly different that is actually based on science. --Tango (talk) 22:47, 3 November 2008 (UTC)[reply]
It depends on how you define evolution. Lamarckism is a form of evolution, but it is very different from Darwin's inheritance with variation/survival of the fittest. It's also thoroughly refuted (but, in a certain sense, nice - if you father worked out, you get to be stronger ;-). But no, in modern biology there is no competing theory to evolution, and I'd expect that all new theories would be refinements, not replacements, of evolution. --Stephan Schulz (talk) 23:03, 3 November 2008 (UTC)[reply]
Let's put it this way. There is a lot of variety to life on earth and a fossil record which seems to imply some sort of shared descent. The best scientific explanation of that is some form of evolution—currently evolution by natural selection as articulated by the modern synthesis is the chief candidate for that, but that is relatively recent (1930s; before that Darwinism was thought to have been a dead-end when it comes to the specific mechanism of evolution). Are there other explanations? The only two that any people have put out is some form of special creation (a supernaturalistic intervention) or that extraterrestrials have somehow seeded the planet and manipulated the gene pool (a naturalistic invention). Neither of these theories are scientific as neither are testable, though one could imagine a world in which the latter became possible to test (aliens arrive, thank us for all the hard work). --98.217.8.46 (talk) 02:00, 4 November 2008 (UTC)[reply]
Once you get your head around evolution - you rapidly realise that there is no way it cannot happen. If there is:
Occasional variation in the genetic makeup of individuals...
...that is passed on from parent to child organism...
...and which influences the ability of the organism to produce offspring...
...then there is no way for there NOT to be evolution.
Since all of those things are demonstrably true - then there simply MUST be evolutionary change. The only questions for which an alternative theory might be postulated is whether evolution actually accounts for all of the variation we see - (it seems that it does) and whether it provides some kind of mechanism for how life appeared from non-living things (maybe...maybe not...the jury is still out on that one). But there can't be reasonable doubt about whether things evolve - it's really simple to demonstrate in a laboratory - it happens every day with things like drug-resistant diseases and rats that become immune to rat poison. Now that we've recognised the mechanism happening in life-forms, we can now see it appearing in other settings - the idea that 'memes' are evolving ideas that pass from brain to brain along various communications channels - changing as that happens is an interesting variation on the idea. I would argue that the current financial crisis is the consequence of businesses evolving more and more tightly tuned business practices over the course of time without the pressure of legal limitations to force them to evolve in ways we'd like. You can even argue that (for example) dogs have "evolved" to be suitable pets for humans because our selective breeding of them is merely another influence on their ability to reproduce. It doesn't matter whether aliens manipulated our genes - the aliens had to have evolved at some point (or the meta-aliens who created the aliens...or...). Even if creationism/intelligent-design (a seriously whacked-out theory if ever there was one) turned out to be true - evolution must ALSO be true - because we can see it in action - we can make it happen whenever we choose to do so - and it behaves as we would predict it should when we do those experiments. Hence creationism/ID could only ever be a supplement to the theory of evolution - it can't replace it. SteveBaker (talk) 05:14, 4 November 2008 (UTC)[reply]
You may compare the situation to physics. We have Einsteins theory of gravitation and then there's legitimate alternative theories on gravitation. But there's no alternative to gravitation. In biology there's lots of theories that go beyond school-book texts on evolution and some of them even conflict between each other, such as, genetic drift, Terry Deacons ideas about the Bengalese finch, the theory of punctuated equilibrium, even an almost-lamarckism theory on how certain traits are being transferred, but all of these incorporate darwin's theories. This is a common situation in science, compare for instance with how Newton's laws of gravity is included in Einstein's theory. EverGreg (talk) 09:20, 4 November 2008 (UTC)[reply]
These misunderstandings mainly come from two different definitions of the word theory. In common language, people use the word "theory" to mean what scientsists call a "hypothesis", which is an as-yet-untested idea (Like "I have a theory about why so-and-so happens.."). The deal is, this is NOT AT ALL what a scientific theory is. A scientific theory is best desribed as a productive framework of ideas. By productive, it means you can work within it and remain both logically and observationally consistant. To put it in another way, a theory is a logical explanation which provides a framework for understanding various related observations. So we have Atomic theory which contains all we know about the atom, from a chemists framework. It isn't that there are alternatives to Atomic Theory seriously being considered; it is a widely accepted framework of ideas, and chemists can do productive work within it. Atomic theory is constantly being modified by new discoveries, but as a coherant realm of thought it is quite solid and useful. Evolution theory is no less a complete and productive framework of thought... --Jayron32.talk.contribs 18:46, 4 November 2008 (UTC)[reply]
That's why I used the word 'explanation' in the OP. 216.239.234.196 (talk) 19:52, 4 November 2008 (UTC)[reply]
Mesoscaphe
The noted oceanographer and submersible designer Jacques Piccard recently passed away. In the Wikipedia article on him he is credited with the design of the bathyscaphe Trieste. He is also credited with the design of the mesoscaphe Ben Franklin (PX-15) and commanded the mission in 1969. There is no reference or link to "mesoscaphe" in Wikipedia. What is a "mesoscaphe" and how is it difference from a bathyscaphe?
Garybirk (talk) 20:58, 3 November 2008 (UTC)[reply]
One would assume that the mesoscaphe was so called because it was designed for exploration at levels not as deep as those reachable by a bathyscaphe. Bathy- comes from the Greek word for "deep"; meso- from the Greek word for "middle." Deor (talk) 23:10, 3 November 2008 (UTC)[reply]
Imaginary helium balloon
If you had an imaginary balloon and tied it to a small car, about how many cubic feet of helium would you need to fill it with to make the car float? Louis Waweru Talk 21:48, 3 November 2008 (UTC)[reply]
I don't know any way of working this out, but for some reason I imagine even if you filled the whole car with helium, it would not lift. I imagine the mass of the car is too great. —Cyclonenim (talk · contribs · email) 21:49, 3 November 2008 (UTC)[reply]
Helium, at standard temperature and pressure, has a density of 0.1786 g/L. The density of air (again at STP) is 1.2754 g/L. Consequently, you get about 1.1 grams of lift per liter of helium. Assuming a 1000kg car, you'd need about 900 000 liters of helium -- a spherical balloon some 12 meters in diameter (and that's ignoring the mass of the balloon and other associated hardware). — Lomn 21:56, 3 November 2008 (UTC)[reply]
Thank you for the grams/liters number. This was a very nice answer. Louis Waweru Talk 22:12, 3 November 2008 (UTC)[reply]
FYI, what you typed rendered as 4/(3pi)*12^3 -- pi is on the wrong side of 4/3, and you cubed the diameter rather than the radius. — Lomn 14:23, 4 November 2008 (UTC)[reply]
Are you sure you typed the numbers in right? I get 905 m3. --Tango (talk) 00:04, 4 November 2008 (UTC)[reply]
That was just an estimate. A spherical 900,000 liter volume is about 12 m diameter. So is 905 m3 ~Amatulić (talk) 00:06, 4 November 2008 (UTC)\[reply]
So if you want to REALLY be sure to do it, just make the balloon 12.5 meters. BTW, the calculation can be seen empirically with such objects as blimps. Compare the size of the balloon to the size of the car it is carrying. I am sure that the balloon in a blimp is more than adequate (i.e. its SO big that it contains MUCH more helium than needed) but it does give you an idea of scale... --Jayron32.talk.contribs 03:49, 4 November 2008 (UTC)[reply]
905 is greater than 900, so 12 meters already has a margin of error. The blimps can't contain too much extra helium, otherwise they would just float up - all the extra helium has to be balanced by extra ballast (which can be dumped in an emergency to gain more lift - they'll certainly have some ballast, but I'm not how much is typical). --Tango (talk) 19:18, 4 November 2008 (UTC)[reply]
That's at STP, the helium is under compression from the balloon so it will take an even larger diameter. -- Mad031683 (talk) 18:09, 4 November 2008 (UTC)[reply]
The depends what kind of balloon you have. Helium party balloons are often made of foil (stops them going flat as fast, I think - presumably helium, being smaller than oxygen and nitrogen, gets through the holes in rubber faster) which isn't very elastic at all so there is virtually no compression. I'm not really sure what blimps, etc., are made of, but I doubt they involve much compression. --Tango (talk) 19:18, 4 November 2008 (UTC)[reply]
Imaginary balloons aren't very good at holding helium ;) 137.108.145.10 (talk) 14:18, 5 November 2008 (UTC)[reply]
observing the dead cat
Forgive me if I'm interpreting this wrong..
The article says the cat "is placed in a sealed box shielded against environmentally induced quantum decoherence".. but isn't the question moot because it's impossible to shield against quantum decoherence? If the cat dies then its mass is concentrated closer to the bottom of the box than if it were standing up.. so light will gravitationally lens around the box slightly differently.. 71.176.167.123 (talk) 22:52, 3 November 2008 (UTC)[reply]
That's why it is a thought experiment. The cat is perfectly spherical, of uniform density, and the box is in free fall ;-). --Stephan Schulz (talk) 23:05, 3 November 2008 (UTC)[reply]
That's an interesting introduction bringing gravity into the problem. If there was a proper theory that combined quantum mechanics and gravitation then one would probably be able to have a superposition where he mass was at the bottom and where the mass was in the middle. I don't think it works out very well at present though - have to hand over to someone who knows more about that. (An applied mathematician considering milk production: consider a spherical cow...) Dmcq (talk) 23:08, 3 November 2008 (UTC)[reply]
Schrödinger's cat, like many thought experiments, involve assumptions to get the point across. Maxwell's demon, for example, assumes the existence of a massless door that requires no energy to open and close. You do have a novel way of determining the position of the cat through gravitational lensing, but this still tells you nothing about the living state, only whether the cat is standing up or lying down. For the purpose of this experiment, assume the box is too cramped for the cat to move. ~Amatulić (talk) 23:11, 3 November 2008 (UTC)[reply]
See Spherical cow. The origin of the term is supposed to be that people from agriculture went to someone from the physics department at the University of Illinois to see if the folks there could help with a problem of decreasing milk production [27]. Edison (talk) 04:02, 4 November 2008 (UTC)[reply]
Essentially, if you put the 50% killing mechanism and a cat, into an impossible magic box. Something impossible happens to the cat. Perhaps not as shocking as Schrodinger meant it to be, but it's still useful as a thought experiment and teaching tool. APL (talk) 14:07, 4 November 2008 (UTC)[reply]
I remember reading an article on here where they pointed out that a small gravitational effect can be masked by the quantum effects on the scale, or something to that effect. I doubt it would do much at that scale, but that's only one of the reasons the quantum waveform would collapse if this thought experiment were actually carried out. — DanielLC 16:14, 4 November 2008 (UTC)[reply]
Personally - I've always felt that that thought experiment doesn't go far enough. Consider that the experimenter and his wife start the day together. The experimenter goes into completely enclosed lab and starts the cat experiment. At the end of the day, he plans to phone home and chat with his wife to tell her how his day went. He's a sensitive fellow and is rather fond of cats - so while he doesn't know whether the cat is alive or dead, he's in a simple, single state of not knowing. But when he opens the box to discover what happened...far from the quantum state of the cat changing - HIS state changes. He is now in an entangled state between being happy that the cat is OK - or being devastated that it died. Not until he phones home does his state become coherent The enclosed box with the cat inside that is either dead or not dead depending on whether an atom decayed or not - is completely analogous to the experimenter inside the sealed lab with either a dead or live cat that makes him either sad or happy...his happiness state is just as much determined by that single atomic-scale event as is the cat's morbidity...except that there is a longer delay before it happens to him. However, we may argue that when he phones home, all he's REALLY doing is pulling his wife and the telephone lines between them into the same entanglement as the cat and the atom. It's not unreasonable to imagine ripples of entanglement spreading outwards to other parts of the planet and eventually, to the entire universe. The fact that the position of the cat in the box causes gravitational disturbances simply means that the entanglement spread out at the speed of light - rather than at the speed that the researcher would call his wife...it's no different in principle. This is the most powerful argument for the 'many worlds' interpretation IMHO. SteveBaker (talk) 20:37, 4 November 2008 (UTC)[reply]
That is an interpretation I've heard before. I think "observation" is roughly defined, in that interpretation, as something sufficient to trigger that rapid expansion of the entanglement (presumably speed of light, or marginally slower). --Tango (talk) 00:37, 5 November 2008 (UTC)[reply]
I don't really see that supporting the many worlds theory. It seems more like a matter of frame of reference. If you're the researcher before he opens the box or the wife before he phones home, the state of the cat is undefined; it IS either alive or dead to an observer inside the box/lab, but for the researcher/wife the universe from their frame of reference is not a function of the state of the cat. 71.176.167.123 (talk) 16:45, 5 November 2008 (UTC)[reply]
I see it as supporting many worlds as follows: If the entanglement spreads out when "observed" (to include the observer into the entanglement) rather than "collapsing" as so often explained - then eventually, the entire universe is in a state of entanglement with the cat's demise/survival causing different consequences for each state. The scientist is so upset at the death of the cat that he commits suicide, he never invents the magic CO2 absorbing substance that would have saved the world from global warming. The scientist finds the cat is alive and is inspired to go on to save the world. So the entire planet is in superposition between being globally warmed or not. This effect can spread - much like the "butterfly effect" to result in all of everything being in superposition based on that one atom either decaying or not. Since two completely separate versions of the universe are now "superimposed" with no way for one to influence the other - we now have two parallel universes. In reality, every atomic decay or other random quantum event causes the universe to be in an entangled state - and that entanglement can only (it seems) spread outwards at something like the speed of light. So for all PRACTICAL purposes, you have parallel worlds. The only way to avoid that is with the idea that "observing" causes a collapse of the entanglement. That's OK when it's a cat in a box - but if you'll allow me to push the thought experiment out to being an entire planet that's either entangled - then I think you have many-worlds whether you like it or not. SteveBaker (talk) 20:18, 5 November 2008 (UTC)[reply]
November 4
Religion, sci-fi and the brain
Has there been any study into whether reading science fiction or fantasy releases neurochemicals, or activates areas of the brain, associated with religious or spiritual experience, and if so whether the extent to which this so is correlated with the reader's opinion of the work? NeonMerlin 03:59, 4 November 2008 (UTC)[reply]
Thermodynamics
We already know that the temperature of something gives off different color. For example, a blacksmith can just look at the color of a horseshoe and tell how hot it is. It can be yellow or red or even white if it is really really really hot. We can also look at our sun and make intelligent guesses. My question is, is it possible to heat up something soooooo much that it might actually become black?69.224.117.143 (talk) 05:04, 4 November 2008 (UTC)[reply]
Black isn't a color of light something can emit, it's the absence of light. A horseshoe can certainly be heated up until it's black...room temperature (although it's actually still emitting light, just too far infrared to see. See black body to understand how the color of incandescence corresponds to temperature. DMacks (talk) 05:16, 4 November 2008 (UTC)[reply]
So what you're probably thinking is that as the temperature rises - so the color shifts up the spectrum from infrared - through red, yellow, blue and then off into ultraviolet - so that the object would once again appear black? If that's what you're thinking then this sentence from black body should help: "So, as temperature increases, the glow color changes from red to yellow to white to blue. Even as the peak wavelength moves into the ultra-violet, enough radiation continues to be emitted in the blue wavelengths that the body will continue to appear blue. It will never become invisible — indeed, the radiation of visible light increases monotonically with temperature.". So while the PEAK of the radiation may well be off into the ultraviolet - you still see increasing amounts of visible light - so the object just continues to get more and more brightly white - even as the UV is invisibly frying your skin. This is evident because (for example) as you heat a piece of iron, it goes from red to yellow to white. It doesn't ever glow green. That's because the red and yellow light didn't go away as the frequency of the peak shifted upwards - so that even when there is a noticable amount of green light being generated - there is enough red still present to make it look yellow - and as the peak shifts towards blue, there is still enough red and green to make it look white. SteveBaker (talk) 20:24, 4 November 2008 (UTC)[reply]
Functional Group effects on the acidity of a compound
What effects do funcational groups alcohol, carboxylic acids and halogens, as well as the number of hydrocarbons have on the acididyt of a compound.
How can you identify, given the structural formaula, which compound is most/least acidic.
Generally, the presense of electron-withdrawing groups will tend to weaken the C-H bond at neighboring carbon atoms (the so-called "alpha" position), thereby making those positions slightly more acidic. For compounds such as Acetylacetone aka 2,4-pentadione, the hydrogens on the carbon between the carboxyl groups are sufficiently acidic enough to be removed by sodium hydroxide; most C-H bonds are unaffected by NaOH... Although, you should probably do your own homework... --Jayron32.talk.contribs 06:13, 4 November 2008 (UTC)[reply]
Robo-thugs
In the North Hollywood shootout, 17 cops and civilians were shot but not a single one was killed. Is it a "thankful" side-effect by the bad guys' use of armor-piercing rounds? I mean anti-personnel rounds (e.g., hollow-point bullets) may shatter upon impact and blow up inside the human body. Armor-piercing rounds may create clean-cut wounds that are less damaging. -- Toytoy (talk) 07:39, 4 November 2008 (UTC)[reply]
I've no idea about ones that blow-up inside the body but anything that goes through will presumably leave a pretty hefty exit-wound, and will potentially cause plenty of damage. I suspect that a key factor would've been the speed with which the victims of the gunshots were treated (were ambulances on stand-by at the scene for example), along with perhaps a bit of luck regarding the placement of the wound on the body. 194.221.133.226 (talk) 11:20, 4 November 2008 (UTC)[reply]
Not an expert on bullet wounds, but I'm using the resources at hand here. The article on ballistic trauma says that rifles typically do more damage than hand-guns, although hollow-point bullets are more damaging than full metal jackets. There are many factors involved, however, as already mentioned. The police acted quickly and effectively in this case, and many people were hit through cover by armor-piercing bullets, which may or may not have reduced the severity of wounds; people in cover would also be hit by ricochets, again at lower velocity, or in bodily extremities. Looking at typical shootouts, such as 1986 FBI Miami shootout or Tyler courthouse shooting, once fire has been returned, fatal shots by criminals (even from rifle or carbine) were typically from very close range. The lesson being that unless you have a clear shot at a stationary target, it's surprisingly hard to shoot someone dead (assuming medical care is on hand).--Maltelauridsbrigge (talk) 16:03, 4 November 2008 (UTC)[reply]
(ec)Armor-piercing rounds definitely do less damage than hollow points or heavier, slower moving slugs like a .45. AP rounds pass through the human body and hardly slow down, while a hollow point breaks up and delivers all of its energy into the target. I'd say the AP rounds helped but it was really just incredible luck that no one got hit in a vital organ and quick respone by emergency services.-- Mad031683 (talk) 16:08, 4 November 2008 (UTC)[reply]
It may also have helped that the cops very soon discovered that they couldn't do any damage to the shooters because of the incredible amount of armor they were wearing. This may have prompted them to stay in cover so that the perps couldn't see them to aim at (of course those AP rounds would go right through a cop car like it wasn't there - so people would still get hit - just not with any degree of accuracy). This view is kinda backed up from the video footage. SteveBaker (talk) 20:20, 4 November 2008 (UTC)[reply]
environmental issues
why is there a need to reorient the values that people hold concern the environment based on the development of environmental ethics on a social perspective? —Preceding unsigned comment added by 121.97.4.2 (talk) 08:21, 4 November 2008 (UTC)[reply]
This is not a science question. Prehaps you should post this question to the humanities section of the reference desk. 122.107.228.237 (talk) 08:45, 4 November 2008 (UTC)[reply]
If this is as much a homework question as it appears, you can test the teacher by answering the question "Is there a need..." instead of "Why is there a need...". -- kainaw™ 18:10, 4 November 2008 (UTC)[reply]
Descendants of Abraham
Just out of personal curiosity - assuming hypothetically that Abraham was a real person who lived 1800 BC and really had 8 sons (sadly there's no record of daughters), would pretty much everyone in the western world be descended from him? Is there a way to calculate something like this? —Preceding unsigned comment added by Vultur (talk • contribs) 09:26, 4 November 2008 (UTC)[reply]
Surprisingly, possibly yes. Some native American populations have been fairly isolated (as have native Australian ones - what is "the western world" for you?). But there are some gene flow models that make a most recent common ancestor somewhere between the 6th and the 1st millenia BCE plausible. With an extremely naive approach, 1800 BCE is about 1300 generations ago, so you could have up to 2130 (1.361e39) ancestors. Compare that to the world population of maybe 40 million (4e6) back in 1800 BCE, and you can get an impression of how much intermixing of lineages has taken place. You might want to look at our articles on Y-chromosomal Adam and Mitochondrial Eve, as well, although these deal with much more limited lines of descent. Another interesting point is the Ghengis Khan Effect, which gives an idea of how fast a gene can spread. --Stephan Schulz (talk) 10:14, 4 November 2008 (UTC)[reply]
Do fairness creams really work?
Is there any scientific evidence to the efficacy of fairness creams? I am asking this because there is a barrage of fairness creams being introduced into the market for men as well as women where I live and I want to know if these companies are all just taking the consumers for a ride. I don't need one myself, but I am curious if they work at all, given that it is a massive industry. I looked but I couldn't find any information on the skin pigmentation article. Thanks. 124.30.235.62 (talk) 10:31, 4 November 2008 (UTC)[reply]
Thanks! I read that. So it looks like there is some scientific basis to skin whitening products. That's good to know, I suspected the compnaies were selling just wuga wuga to the people :P 125.21.165.158 (talk) 11:53, 4 November 2008 (UTC)[reply]
That such products CAN exist does not mean that any one producte WILL work as promised... some really ARE just "snake oil". --Jayron32.talk.contribs 12:10, 4 November 2008 (UTC)[reply]
Noble and Ig Nobel for same work?
Has anyone ever won both a Nobel Prize and an Ig Nobel prize for the same work? —Preceding unsigned comment added by 82.124.209.97 (talk) 12:58, 4 November 2008 (UTC)[reply]
So, that would be the real challenege, wouldn't it. The person to do that would be the first in the history of the world. Tell me, what are some possible tracks I could pursue? Are some fields of inquiry inherently more ridiculous than others? What are some quite ridiculous real Nobel prizes that have been given -- I'm thinking of Kissinger's Nobel Peace Prize! —Preceding unsigned comment added by 82.124.209.97 (talk) 13:24, 4 November 2008 (UTC)[reply]
Might be tough. Even assuming you could get a Nobel for a silly enough topic, AIR tends to choose rather obscure bits of research for award. A nobel prize winning contribution might be too high-profile to make effective comedy. APL (talk) 14:11, 4 November 2008 (UTC)[reply]
Trust me, compared to getting the Nobel - sneaking in a piece of silliness to win the IgNobel is going to be a piece of cake! SteveBaker (talk) 14:57, 4 November 2008 (UTC)[reply]
I think you'd have to go the other way: get Ig for something silly, then find it's actually based on a groundbreaking and novel principle that gets extended into a Nobel. Like what if this year's soda/sperm result led to discovery of a whole new cell-surface receptor class that 1) happened to be responsible for the soda effect and also 2) were responsible for various parts of the sperm/egg fusion process? DMacks (talk) 16:41, 4 November 2008 (UTC)[reply]
Wow, talk about "takes a village"! APL, SteveBaker, and Dmack, your advice combines perfectly THUS: "Do groundbreaking research that is Nobel-prize worthy. Publish ONLY the silly parts of it, leading your research to seem utterly pointless! Win the Ig Nobel. Publish the rest and win the Nobel!" What do you think? —Preceding unsigned comment added by 82.124.214.224 (talk) 19:06, 4 November 2008 (UTC)[reply]
Sounds like a plan! Be sure to mention us in one or both of your acceptance speeches!APL (talk) 20:01, 4 November 2008 (UTC)[reply]
If you could swing getting a job at CERN, you could find the Higgs boson, which would get you in the running for the Nobel, but then in a wacky mixup lose it again, which will surely get you the IgNobel! --Sean 19:34, 4 November 2008 (UTC)[reply]
I could see how you could lose a Higgs boson. I mean they may be kinda heavy as these things go - but they are still small enough to fall through a hole in the pocket of your rented tux on the way to the ceremony. There you'd be in front of all of those serious scientists - they'd hand you the check and the pretty medal...then SOMEONE with a red sash over his shoulders is sure to say "Well, show it to us then!"...and there you are up on the stage, searching through all of your pockets looking for the darned thing. That's EXACTLY the kind of thing that'll get you your IgNobel though. SteveBaker (talk) 20:16, 4 November 2008 (UTC)[reply]
It sounds like you're speaking from experience. My condolences. :( —Preceding unsigned comment added by 82.124.214.224 (talk) 21:22, 4 November 2008 (UTC)[reply]
Nobel prizes are typically awarded long after the work is done: Makoto Kobayashi and Toshihide Maskawa won the Physics prize this year for work published in 1973, 35 years ago. The Ig Nobel prizes have only been awarded since 1991 and tend to reflect recent research (e.g. Jacques Benveniste won Ig Nobel Chemistry in 1991 for work published in 1988). So while nobody has won both yet, give them a chance!--Maltelauridsbrigge (talk) 15:08, 5 November 2008 (UTC)[reply]
Suspensions
I'm looking for examples of commercial situations where there is a need to keep solid particles suspended in a water-based solution. The only two I've come up with so far is Drilling mud and hydroseeding. I'm not interested in food applications. My thanks if you can think of any. ike9898 (talk) 15:14, 4 November 2008 (UTC)[reply]
Huh. For some reason, I barely remember asking that before. Thanks. ike9898 (talk) 01:08, 5 November 2008 (UTC)[reply]
Slurry will give you some further leads. Rmhermen (talk) 21:27, 5 November 2008 (UTC)[reply]
Does anyone know
the names of Claude Cohen-Tannoudji's parents, a french physicist, and a Nobel Prize
laureate in Physics ? BentzyCo (talk) 17:53, 4 November 2008 (UTC)[reply]
Functional morphology
Could someone give me a brief overview of functional morphology and its purposes? The best resource I can find online is [28] which doesn't go into much detail. 81.154.63.120 (talk) 17:57, 4 November 2008 (UTC)[reply]
Sounds to me like someone is coining a new term for an old word. Morphology (biology) deals with the shape of things, ignoring function. Physiology deals with the function. So, it sounds to me like "functional morphology" is either a bad way to say "physiology" or a way to blur the lines between physiology and morphology. -- kainaw™ 18:08, 4 November 2008 (UTC)[reply]
Yeah, but doesn't physiology deal with systemic function? It could be a difference of focus... Like in physiology you look at the operation of the circulatory system, but in functional morphology, you focus on how the shape and organization of say, the heart, effects its operation? Just a WAG here... --Jayron32.talk.contribs 18:48, 4 November 2008 (UTC)[reply]
I'm hoping that is it - a blur between physiology and morphology. I don't like it when someone just gives a new name to something that already has a popular name. -- kainaw™ 22:29, 4 November 2008 (UTC)[reply]
According to the website,
"Functional morphology focuses on the link between animal form and performance. Gaining insight in the precise way in which biological machinery performs under relevant conditions is of primary importance. Detailed morphological and morphometric study, movement analysis, dynamographics, electromyographic recordings, registration of physiological processes (like measuring respiration rates…), performance measurements, etc, all belong to the functional morphological repertoire."
A 2-tonne mass restson a horizontalsurface.Calculate the horizontal force,in kilonewtons,required to move this at a uniform speed along the surface if the coefficient of kinetic friction is 0.35. —Preceding unsigned comment added by 213.193.61.145 (talk) 19:51, 4 November 2008 (UTC)[reply]
OK, I did the calculation. Now what? Edison (talk) 19:53, 4 November 2008 (UTC)[reply]
Just to clarify what Edison is saying: Do your own homework. Chances are, you were taught how to do questions like this some time in the week prior to the homework being set (you see, that's how homework works...). --Tango (talk) 19:54, 4 November 2008 (UTC)[reply]
(And it's a ridiculous question anyway because out here in the real world, the surface area matters as well as the mass and the coefficient of friction...however, what they teach in schools about friction is the way you're supposed to answer it...right or wrong.) SteveBaker (talk) 20:09, 4 November 2008 (UTC)[reply]
Well, High School physics is merely an arithmetic and algebra class. It teaches the discipline of actually reading problems and applying the information in problems to formulas, choosing the correct formula, etc. etc. Its basically 9 months of "how to read and solve word problems, with an occasional lab thrown in". Not that this is not a skill that is important, or that we don't want our students to learn, but we need to understand, before noting the lack-of-applicability, the context in which high school learning is markedly different than learning in the college or grad school classroom... --Jayron32.talk.contribs 20:15, 4 November 2008 (UTC)[reply]
Surely the coefficient of friction is a function of the surface area of contact, among other things? Algebraist 20:13, 4 November 2008 (UTC)[reply]
I realize this question sounds as though it came directly from a school assignment. I also know that it is reference desk policy not to answer such questions. However, I think it might have sufficed to state this policy, without going on to knock the person who posted the question here, the teacher who (presumably) set the question, and their entire school system. CBHA (talk) 20:40, 4 November 2008 (UTC)[reply]
Well, the school system fulfills an extremely valuable service, but it needs a few knocks (well, mostly the funding agencies need it, but one has to start somewhere). Man, just imagine living in a state that spends as much on education as on the military... --Stephan Schulz (talk) 20:51, 4 November 2008 (UTC)[reply]
I didn't knock any teacher or school system at all. High school classes by necessity teach different material than college classes, not least of which is related to the congnitive readiness of the average 16-year old with regards to certain concepts being different than that of the average 21-year old. You wouldn't teach a 4-year old how to perform logarithmic calculations, but that doesn't mean that you cannot teach basic math concepts which are developmentally appropriate. Likewise, you have to teach students in high school basic skills before they can learn how to tackle the more realistic problems. I was just reminding those that were criticizing the "realism" of a typical high school physics problem that the purposes of a high school physics curriculum are, by necessity of the kind of student in those classes, quite different than the purposes of a college-level physics class. It is not a bad thing that the school is considering the developmental level of the students it teaches. On the contrary, this is a Good Thing! --Jayron32.talk.contribs 21:15, 4 November 2008 (UTC)[reply]
FWIW, I enjoy reading the discussions here and learn a lot from reading everyone's take. 216.239.234.196 (talk) 21:38, 4 November 2008 (UTC)[reply]
To answer Algebraist's question: No, in the ideal, abstract world, friction does not depend on surface area. Abstract friction is a function of both surface area and weight per unit surface area, so if the same weight is spread over a larger surface area, then each sqare centimeter contributes less friction. Therefore, the surface area cancels out and only the weight remains. The student must still do the math. -Arch dude (talk) 22:37, 4 November 2008 (UTC)[reply]
I watched a Mythbusters' episode last night where they interleaved the pages of two phone books and then tried to pull them apart. It took two large tanks to pull them apart again. If friction did not depend on surface area then it would be no different from stacking one book on top of the other - and you can push them apart with your little finger. This is by far the clearest demonstration of how very wrong (even "misleading") the 'approximation' they teach in schools truly is. People argue that "well, it's just an exercise for the kids" - but just look at some of the HUGE debates we've had over this in the past from people who've taken that approximation with them into adulthood and are treating it as a fact on a par with Newton's laws! Generally, I'm all for keeping things simple and manageable for kids - but this is an egregious example. Another one that upsets me is the claim that airplanes fly because of the longer path that air takes over the top surface of an airfoil compared to the bottom. Some things NEED to be fixed. SteveBaker (talk) 00:59, 5 November 2008 (UTC)[reply]
Actually, in the phone book case there is a self-reinforcing mechanical feedback that increases pressure far beyond that of gravity. --Stephan Schulz (talk) 01:21, 5 November 2008 (UTC)[reply]
Let's treat the phone book example using the grossly oversimplified theoretical model.There are roughly 2000 interacting surfaces. The bottom-most surface has the entire weight of both phone books bearing on it. the next surface has Wx.9995 bearing on it. the next has Wx.999 bearing on it, and so on until the top surface has Wx.0005 bearing on it. Summing all of this, we would expect the interleaved phone books to exhibit 1000 times the friction that non-interleaved phone books exhibit. If the coefficient of friction for newsprint (i.e., what phonebook pages is made of) is .5, and each phone book weighs 1 kilogram. Then the theoretical force would be 1000Kg. If you place a one-liter bottle of milk on top, the theoretical force would be 2000Kg.Yes, there are a lot of real-world effects in this experiment, but ordinary theoretical model explaines a lot of the phonebook phenomenon. -Arch dude (talk) 04:12, 5 November 2008 (UTC)[reply]
I thought Jayron32's reply was the most favorable statement to existing institutions and teaching methods I've seen on the issue. Mac Davis (talk) 00:07, 5 November 2008 (UTC)[reply]
I agree. It's certainly not the fault of the school or (in the main) the teachers. It's the curriculum. If standardized testing says that there is a definitive, easy-to-calculate answer to the question our OP asks - then they NEED to teach that - both for their own sake - and the short-term needs of the children. The place to lay the blame is in the school boards where books are chosen and curriculums are laid down. School math and science books in the USA are almost all atrocious. If you have kids with an interest in science - go out and buy Feynman's trilogy of lectures on Physics - and as soon as they are able to understand it - dig in! SteveBaker (talk) 00:59, 5 November 2008 (UTC)[reply]
Shouldn't we be given the value of gravitational attraction? Would the answer vary if it were on Earth at the poles or the equator, or if it were of the Moon or Mars? Or on the International Space Station? Things actually get moved at all those locations. Edison (talk) 06:09, 5 November 2008 (UTC)[reply]
The websites for Bad Astronomy, Bad Meteorology, and Bad Chemistry have (unfortunately) a huge number of examples of horrible attempts at explaining science, usually as a result of "simplifying" the process so that the dumb kids will understand it. The problem of course being that after being taught something incorrectly, it's extremely hard to un-learn it, even given boatloads of evidence. The personal hangup for me was the one about how cold air doesn't hold as much water as warm air does. After reading the proper explanation in the link above, I saw at once that he was correct, but couldn't get my head around exactly why it mattered for the longest time. The air isn't holding the water! Matt Deres (talk) 16:10, 5 November 2008 (UTC)[reply]
Compound
A compound is defined as a substance consisting of two or more different elements chemically bonded together. But can "compound" also be used to refer to things like O2 and O3 in the sense that they are different compounds of the same element? --RMFan1 (talk) 23:02, 4 November 2008 (UTC)[reply]
No, a compound is always multiple elements. O2 and O3 are molecules, which is something entirely different from a compound (for example, some compounds are molecules while others are ionic compounds and still others are network solids). The correct term for the relationship between O2 and O3 is allotrope, which refers to chemically distinct forms of an element. --Jayron32.talk.contribs 23:05, 4 November 2008 (UTC)[reply]
Mercury surface temp.
What's the peak high of Mercury's surface over daytime, is it 430 C or 805 F, well I seen source said 510 C or 950 F. Is the average daytime temp about like 280 C or 580 F some said 350 C or 660 F. Will it's night peak dive as far as -220 C or -350 F, some books have siad it. I can be surprise the way Mercury's temp range so deep, it's because lack of atmosp, that's why the disc color is gray or silver.--FRWY 23:28, 4 November 2008 (UTC)[reply]
The different numbers may be because they are measuring slightly different things. There's midday temperature on the equator which will be the highest value, average midday temp over all latitudes, average equator temp during the whole day, average temp over the whole day over all latitudes, etc. You need to check precisely what is being quoted in order to compare figures from different sources. The large difference between day and night is, indeed, due to the lack of an atmosphere. --Tango (talk) 23:40, 4 November 2008 (UTC)[reply]
Some sources like this said Mercury's peak high is over 900 F or 500 C, and it's peak low is lower than -200 C or -330 F. Is Venus hotter or Mercury. i thought Venus' average is around like 470 C or 870 F. Venus is always that hot because of the poison yellow gas and thick atmosp heat totally overcast with greenhouse effect.--FRWY 00:18, 5 November 2008 (UTC)[reply]
If memory serves, Venus is hotter due to the greenhouse effect more than compensating for the greater distance from the Sun. It's certainly hotter on average, since it maintains its temperature during the night, which Mercury doesn't. --Tango (talk) 00:33, 5 November 2008 (UTC)[reply]
November 5
Do Angel fish come from Africa or South America?
I knew the commonvariety angel fish is a member of the cichlid family, but thought it to be of the African cichlid variety. In watching an informational TV show, I heard theirs were from the Amazon, not the Nile or, more likely, one of the 3 lakes of Africa where nearly all the available, more common variety Africans in stores can be acquired today.
Question: Do Angel fish come from Africa or South America?Vaylem (talk)
Hi Vaylem, the freshwater angelfish article is here (not to be confused with the Marine angelfish group. The intro makes it "All Pterophyllum species originate from the Amazon River basin in tropical South America." Read on, I might have missed something, Julia Rossi (talk) 08:31, 5 November 2008 (UTC)[reply]
Arrow shields
I seem to recall seeing in some depiction of medieval warfare a portable wooden wall used by sieging armies to protect against archers (especially when they were in a protected position and could not simply be attacked). Assuming that I didn't dream it, what are these implements called and where might I find more information about them? --Tardis (talk) 02:11, 5 November 2008 (UTC)[reply]
No, you didn't dream them. They come in many forms, with various names, including tortoise, cat, weasel and sow (the last giving rise to the famous quote "the sow has farrowed" when the Scots destroyed the English sow at Berwick in 1319). Some stand alone, others form part of an engine (such as a ram). Siege engine offers a poor start. A web search offers a lot of disinformation as well as good stuff, but Bradbury's Companion is a good start. Minor info can be found in various books such as this. Konstantion Nossov's Ancient and Medieval siege Weapons ISBN 186227343X is good, if you can get hold of a copy. Gwinva (talk) 03:09, 5 November 2008 (UTC)[reply]
Inspired by the above-linked page on the TV Tropes Wiki: can one assume that a microwave-cooked item intended to be cooked at N minutes at 1/M power would cook equally well in N/M minutes at full power? If not, what factors in the microwave's working or the food itself make the difference? 69.107.248.192 (talk) 03:17, 5 November 2008 (UTC)[reply]
I expect there will be a clear failure of time-intensity reciprocity when the duration is too long. (This is true of vision and of photography). Edison (talk) 06:05, 5 November 2008 (UTC)[reply]
If the only method of heating was via the excitation of polar molecules (water and carbohydrates) by the microwave, then you may have a case. However, lots of heat is transfered via other methods, principly conduction within the food you are cooking. For some foods, cooking at longer times under lower power settings is indeed more efficient than cooking at shorter times at full power, since the process of conduction can be rather slow. Also, there is a difference in how the power is applied. Many microwaves don't simply emit a constant energy at lower power, what they do is oscilate between on and off states given the power setting. Thus, at 50% power, the microwave may run at full power for 10 seconds, then off for 10 seconds, and so on, while at 75% power, they may run on for 15 seconds and off for 5. Some do have variable power magnetrons, and can directly apply lower power at a constant rate, so the type of microwave oven will greatly effect how it heats the food at different power settings. --Jayron32.talk.contribs 17:25, 5 November 2008 (UTC)[reply]
The problem is with the evenness of cooking. The reflection of the microwaves off of the metal lining of the oven causes interference of the waves - and that means that the cooking is rather uneven. If you cook for a short period on full power then the energy cooks some parts of the food too much and other parts too little. Running for a longer period at lower power has two benefits: Firstly the turntable rotates more times - resulting in more opportunities for every part to be moved through some of the hotter regions - secondly (more importantly, I suspect) is to allow heat from the hotter areas to be conducted through to the colder areas. This is especially important when defrosting food because ice is a good insulator and the heat doesn't flow easily from the hot, watery, melted bits into the solid, frozen bits. Hence, defrost at low power - and (in most ovens) with frequent stops and starts to allow time for the food's temperature to equalise before zapping it some more. You can easily demonstrate this 'patchiness' by either turning off the turntable - or flipping the turntable upside-down so it doesn't rotate anymore - then get some of those chocolate chips that you'd put in cakes or cookies and make a neat little row of them across he middle of the oven. Zap them (at full power) for maybe 20 seconds and then quickly look inside to see what what happened. You'll find that at intervals of about 6 centimeters, there are chips that didn't melt - and in-between there are chips that are just a puddle of chocolate. This is cool because at 12.5 GHz (the frequency of the microwaves) - the wavelength of the radio waves is 12cm. The turntable helps that a bit - but the food close to the center of the turntable doesn't move around much (imagine those 6cm hotspots in a stationary pattern) so it's not a perfect solution. Where possible, I always put things I'm cooking as far from the center of the turntable as I can - so it cooks more evenly. But cooking on lower power for more time works well too. SteveBaker (talk) 17:58, 5 November 2008 (UTC)[reply]
Violation of conservation of mass in positron emission???
In positron emission, a proton decays into a neutron, electron, and neutrino. Since the mass of a proton is less than that of a neutron, does that mean that energy is converted into mass in the reaction? Beta decay#β+ decay says that some of the binding energy goes into converting a proton into a neutron, but that's not really what I'm looking for. So, does the extra mass result from the conversion of energy into mass? --70.242.149.190 (talk) 03:44, 5 November 2008 (UTC)[reply]
an isolated proton is essentially stable. It does not "decay" into neutron, positron, and neutrino, unless you provide energy for the process. Even a proton plus an electron will not combine into a neutron plus neutrino without additional energy being provided. Indeed, if was occurring spontaneously, most of hydrogen in the Universe would have long decayed by electron capture; which, luckily, is not the case. In a beta-plus decay (positron emission) and in electron capture processes the required energy is supplied by the other constituents of the decaying atom. --Dr Dima (talk) 08:48, 5 November 2008 (UTC)[reply]
Short answer: yes. Axl ¤ [Talk] 21:48, 5 November 2008 (UTC)[reply]
The strength of a monkey
How strong is a gorilla or a chimpanzee? That's a very generic question, I know, but could you still give me some idea? What is the highest recorded level, the lowest recorded level of strength? Who holds those records? How strong are they compared to strong, very well physically developed humans? Thanks. —Preceding unsigned comment added by 24.7.36.125 (talk) 07:20, 5 November 2008 (UTC)[reply]
The article Chimpanzee mentions: "the average chimpanzee has over 5 times the upper-body strength of a human male". In Gorilla "Adult males range in height from 165-175 cm (5 ft 5 in – 5 ft 9 in), and in weight from 140–204.5 kg (310–450 lb). " Taller than females and much heavier. So fairly intimidating implications for humans, though google gets comments that human strength moves such as weightlifting maybe are not matched by a gorilla for whatever reasons. Yeah, right. Julia Rossi (talk) 07:39, 5 November 2008 (UTC)[reply]
Just to be pedantic chimps and gorillas are apes not monkeys. Interestingly it looks like chimps have much faster reactions as well as being much stronger. Basically it looks like speed and strength have taken second place to intelligence for us. Dmcq (talk) 13:48, 5 November 2008 (UTC)[reply]
Yeah, chimps can and will kick your ass. Common Chimpanzees can, especially in captivity, become agressive and mean. There was a zoo/park about a mile from where I grew up, Benson's Wild Animal Farm. They had a chimp in a cage who was known, in fits of rage, to tear an inflated basketball in half with his bear hands. I wouldn't want to tangle with that. Bonobos are supposedly more docile and less aggressive, supposedly more suited to human interaction, that is, if you can keep them from humping everything in sight. But AFAIK, their strength is equally as formidable, so I don't think I'd want to mess with a Bonobo in a bad mood either. --Jayron32.talk.contribs 17:16, 5 November 2008 (UTC)[reply]
the JFK shot
I was watching a movie with a story that revolved around the notion that a rifle could be fired to hit a minuscule target a mile away,do rifles that accurate and powerful exist ? —Preceding unsigned comment added by Blak thot (talk • contribs) 08:33, 5 November 2008 (UTC)[reply]
How minuscule a target? According to sniper, people have been killed by rifle fire at ranges of well over a mile. Algebraist 08:54, 5 November 2008 (UTC)[reply]
The difficulty over that distance is that the wind takes a massive toll on accuracy. If conditions are at all erratic (wind shifting at all) then you'll miss by a huge margin. --98.217.8.46 (talk) 13:39, 5 November 2008 (UTC)[reply]
When I was in the Marines, I had to qualify every year on the rifle range, which included accurately hitting a black circle about the size of a human head from 500m (about 1/3 mile) using an old crappy M-16 with no scope of any kind. Weather conditions were not considered - I had to qualify if it was nice our or if there was a hurricane blowing in. Given a scope and a good rifle, hitting the same target from a mile would be trivial. -- kainaw™ 13:43, 5 November 2008 (UTC)[reply]
The question of target motion should also be considered. Even a supersonic bullet will take two or three seconds to cross a mile distance. Can the shooter accurately predict where the target will be? — Lomn 14:14, 5 November 2008 (UTC)[reply]
From Sniper rifle#Accuracy, the FBI spec for sniper rifles is an accuracy of at least 0.5 minutes of arc (MOA). At 1 mile (1600 meters), that's a target circle of about the same size as a human head. More expensive weapons can have an accuracy of 0.25 MOA or better. Subject to the conditions above regarding wind and target motion, hitting a human head from a mile away is readily achievable with commercially-available rifles.
For the purposes of a movie, the odds can also be improved by luck, the opportunity to take multiple shots, and artistic license. (For reference, incidentally, JFK was shot from the book depository window 265 feet (81 meters) away. With any moderately well-maintained rifle, in clear weather, and a slow-moving target, the shot wouldn't be difficult.) TenOfAllTrades(talk) 14:42, 5 November 2008 (UTC)[reply]
If you are ever in the area - you can visit the museum and look out of the window next to the one that the shot was supposedly taken from (the actual window is behind a glass partition so you can't get to it). It certainly looks do-able - but having to escape through that building seems awfully tricky. But now go and actually stand on the grassy knoll - behind the fence...it's extremely compelling. The shot looks a million times easier - the escape route is really convenient - everything about it seems WAY better. Although all of the evidence does seem to point to the book repository as the place the shots came from - I've gotta say that if I were planning it - I'd want to be standing on the grassy knoll. SteveBaker (talk) 17:41, 5 November 2008 (UTC)[reply]
I read this New York Times article on Model M82A1 .50 BMG (12.7 x 99mm) sniper rifle,[29] which was a really great read. Throughout the article they talk about hitting targets from about 2 miles away. At that range, not only do you have to take into account wind speed, but the coriolis effect. The rifle itself, bullets "fired from single-shot or semiautomatic rifles, it exits the muzzle at about 3,000 feet per second, has an effective range of 7,500 yards -- or more than four miles -- and at interim distances can do a stupendous amount of damage." -- MacAddct1984(talk • contribs) 19:12, 5 November 2008 (UTC)[reply]
Coriolis effect, really? That sounds implausible to me. Do you have a source for that? Friday(talk) 19:27, 5 November 2008 (UTC)[reply]
It sounds implausible to me, too. The effect would probably only be a few millimetres at most over that kind of time and distance. --Tango (talk) 19:44, 5 November 2008 (UTC)[reply]
My back-of-the envelope calculation suggests the coriolis force could create an error on the order of 5 ft. That's an error you'd want to take into account. Algebraist 19:51, 5 November 2008 (UTC)[reply]
Best I could find with my quick 5 minute search is this. I do concede that it may be more hype than fact, especially when things like wind speed have much greater effect. -- MacAddct1984(talk • contribs) 20:16, 5 November 2008 (UTC)[reply]
I get 4 feet, so certainly of an order you would need to account for (that's the maximum, obviously it depends on your latitude and what direction you are firing it). You learn something every day. --Tango (talk) 22:53, 5 November 2008 (UTC)[reply]
Temperature of mixture of methanol and water
Hello all,
I'd like to calculate the temperature of a mixture of equal volumes of -80C methanol and RT water. I get -17C when I use:
nm x Cm x |Tim-Tf|= nw x Cw x |Tiw-Tf|.
But I'm wondering whether I need to adjust for energy of dissolution (I don't know if that's a real term) or something like that? How would you solve this problem? Thanks! 141.14.217.217 (talk) 08:47, 5 November 2008 (UTC)[reply]
Hi could someone please give me a hand with this question - its driving me mad!
Question: Calculate the force needed to break a nylon wire with a diameter of 0.8mm. The breaking stress of nylon is 5x107Pa.
Ok so this is what I've done so far:
Recognised that to calculate the force needed to break the wire is calculated by multiplying the Breaking stress by the Cross sectional area.
Then I calculated the cross sectional area by doing: Pi x 0.4 x 0.4 = 0.502 mm2. To convert this into metres squared I simply divided 0.502 by 1,000 to give 5.02X10-4m2. Whereas my textbook says the answer is 5.02x10-7m2. Whats going on there?
Finally To calculate the force required I multiplied the force needed to break the wire by the cross sectional area: 5x107 x 5.02x10-4 = 25,100 Newtons - whereas my textbook gives the answer 25.1 N.
The problem is with your area calculation and conversion. First, change the 0.4mm to m before multiplying - notice that you have to divide each radius by 1000 to convert to m. If you find area first, then convert, you need to take into account that the unit is square mm (mm*mm) and convert accordingly.PhySusie (talk) 15:48, 5 November 2008 (UTC)[reply]
Thanks a lot :)
Ancient bateria in ice
As you may know, some glaciers are melting as a consequence of global warming. What I notice is that, these glaciers are formed million years ago. When the water froze at ancient times, bubbles inside may trap some ancient bateria in it. It should not be amazed that some bateria are still surviving, because they are strong enough to adapt the low-temperature environment.
The problem is that, after all these years of seperation, if these bateria are released during the melting of glaciers, can modern organisms be immune to them?
Will they become some sort of super germ?--Lowerlowerhk (talk) 14:53, 5 November 2008 (UTC)--Lowerlowerhk (talk) 14:53, 5 November 2008 (UTC)[reply]
Bacteria that have evolved to survive in temperatures well below 0 C are unlikely to do very well in the human body at 37 C. There are millions, perhaps billions, of species of bacteria to be found on the earth (estimates from Wikipedia article), so a few more highly-specialised species are unlikely to add much peril. Currently scientists are investigating the bacteria in Lake Vostok under the Antarctic icecap which may have been trapped there for 500,000 years, but they are more concerned with preventing contamination from outside than in stopping the bacteria escaping and killing us. --Maltelauridsbrigge (talk) 15:37, 5 November 2008 (UTC)[reply]
I could be wrong, but given that the bacteria has been isolated for such a long time and thus have not been exposed to the rest of the world, I would guess that we're more dangerous to them than they are to us. Think Native Americans (who were isolated from the rest of the world) and European explorers. 216.239.234.196 (talk) 16:00, 5 November 2008 (UTC)[reply]
I love this question! I guess it depends whether they've been living in the ice or somehow been hibernating. If the former - then they'll have evolved so spectacularly to living in that extreme niche that they'll likely die as soon as the ice melts. If the latter (more likely to be true of a virus than a bacterium) - then they may still be in severe trouble because all of the things they evolved to do are no longer optimal. If they evolved in a period when there was much more oxygen in the air - or when there were no flowering plants or grasses - then they might be unable to rely on a high density of whatever plants were around back then. It's a really interesting question though - and it's definitely something worth thinking about. Someone out there must be studying these things. SteveBaker (talk) 17:33, 5 November 2008 (UTC)[reply]
Bacteria in ice don't evolve. Being in ice is a prison that doesn't allow the bacteria to grow or divide at all. A fraction of the bacteria (perhaps ~1%) that fall onto glaciers are able to adapt to the cold by expressing cold-tolerant proteins and mechanisms that already exist in their genomes. Under the right conditions, some bacteria can remain viable even after 100s of thousands of years imprisoned in ice. In general these bacteria pose no risk to anyone and are only slightly older versions of existing strains.
Bacteria beneath ice, i.e. in sub-glacial lakes and soils, do have opportunities to grow and evolve. The oldest of these environments might have been isolated for tens of millions of years, providing plenty of time for profound evolution. However those bugs would have adapted to a very cold, low nutrient environment, and are unlikely to be dangerous to warm-blooded creatures like ourselves. Also, scientists are coming to realize that there are a lot of sub-glacial streams and rivers that may allow bacteria from under the ice reach the ocean. So it is possible that some of these bacteria are being released all of the time, with no visible consequences. Dragons flight (talk) 18:12, 5 November 2008 (UTC)[reply]
Dead pigeon
I have a dead pigeon in my back yard. If I bury it, how deep do I need to go? WAYB (talk) 15:56, 5 November 2008 (UTC)[reply]
9 to 12 inches, then firmed down should be plenty to prevent anything from digging it up. 86.4.187.55 (talk) 16:17, 5 November 2008 (UTC)[reply]
Don't touch it though - that whole "bird flu" thing hasn't gone away. Use something with a decent length of handle to drop it into the hole. SteveBaker (talk) 17:28, 5 November 2008 (UTC)[reply]
Why would a dead animal have avian influenza? Viruses require living hosts. I'd be more concerned about other diseases involving bacteria. But Steve's point stands, put a bag over your hands or something so you're not making direct contact. —Cyclonenim (talk · contribs · email) 23:53, 5 November 2008 (UTC)[reply]
In many jurisdictions, local animal control officers will come and dispose of the remains of dead wild animals for free. This is because dead animals can pose a significant human health risk. Pigeons are especially likely to carry diseases that are transmissible to humans, so I would treat it with care. Dragons flight (talk) 17:58, 5 November 2008 (UTC)[reply]
Effect of Ultraviolet (UVA) on Crystal Growth Versus Visible Light
Since it is known that the shorter the wavelength the greater the "penetration" into an object (organic or inorganic. For example, xrays or gamma rays. In the case of high or frequent xrays and gamma rays this causes damage or mutations in oarganic substances.
Based on this premise, am I correct that UVA would effect the growth on crystals (from a liquid solution)in a way different from visible life. The effect could be accelerated, slower growth and/or effecting the crystals' structure. Am I on the right track?
Thank you
JM
Not sure that it will. The damage that high-energy radiation does to, say, living tissue is also a function of the complexity of the tissue; there's a lot of really large, really finicky compounds that don't take well to being bombarded with high energy. Crystal growth is actually a relatively simple process; I don't see where the energy of light is likely to effect it in any meaningful way. Crystal growth is largely a function of a few factors; the rate of cooling of the solvent, rate of evaporation of solvent, availibility of nucleation sites, etc. will all effect crystal growth. I just don't see where light enters into the picture in any meaningful way.--Jayron32.talk.contribs 17:45, 5 November 2008 (UTC)[reply]
I'm inclined to agree with Jayron32. About the only way that UV exposure is likely to affect crystal growth is to hinder it, by breaking down the molecule that you were hoping to crystallize. (Not a serious problem with simple, stable compounds like sodium chloride, but more trouble for fragile biomolecules like proteins]].) In principle, I suppose that insoluble breakdown products could also act as nucleation sites for crystal formation, but that's more likely to give you a sludgy amorphous mess of uselessly tiny crystallites. TenOfAllTrades(talk) 23:15, 5 November 2008 (UTC)[reply]
I read of an experiment where citrine and aquamarine crystals were subject to 8% black light (test group). They had dendritic crystals form in that group where no dendrite crystals were found in the control group without UV light. The person believedthat UV radiation had an energizing effect on the sensitivity of the crystals.
Would crystals of copper sulfate possibly have this effect?
JM
Space trash
Reading this story about a dumped refrigeration unit falling to Earth, I noticed that the item took 469 days to come down. That sounds like a very long time for a large piece of junk to be a potential hazard in orbit. I would have thought astronaut Clayton Anderson would have stood on top of it and pushed it towards the Earth as hard as possible using his feet. As a rough guesstimate, I would think he could get it to a velocity of ~1 m/s towards the Earth's surface - getting the fridge approx 300 km closer to Earth (and well into the atmosphere) in just a few days. So, have I got my rough guestimate of the astronaut's strength terribly wrong, or did he just push it aside gently (perhaps due to some NASA dumping policy)? Astronaut (talk) 18:12, 5 November 2008 (UTC)[reply]
The object weighed 635 kg. Let's say with his space suit, etc. he might weigh around 150 kg? If he uses a force to accelerate a mass one direction at 1 m/s, how fast is he going to accelerate himself (with 1/4 the mass) in the other direction? He would then have to use some sort of energy to keep from flying off into outer space. Even if he leaned against the space station (a much more massive object), there's still the equal-and-opposite force problem, which would have to be counteracted to avoid changing the orbit. Better to just strap a small thruster onto the tank and launch it to avoid altering the motion of "everything else" too. DMacks (talk) 19:36, 5 November 2008 (UTC)[reply]
It was thrown (literally) by the station's robotic arm at about 30 cm/s. Dragons flight (talk) 20:29, 5 November 2008 (UTC)[reply]
There is so much space debris about, one more piece for a little over a year doesn't make a lot of difference. Also, applying forces to objects in orbit doesn't work quite as you would expect, I think you would be better off pushing it backwards, rather than down. --Tango (talk) 19:40, 5 November 2008 (UTC)[reply]
Well, for one, a push yielding 1 m/s down isn't actually "down". The trash gets closer to Earth on one side of its orbit, but not on the other. What that describes is more or less a partial transfer orbit. Per our orbital mechanics article:
If a brief rocket firing is made at only one point in the satellite's orbit, it will return to that same point on each subsequent orbit, though the rest of its path will change. Thus to move from one circular orbit to another, at least two brief firings are needed.
As a result, you can't simply say that the object moves towards Earth at 1 m/s. Ultimately, atmospheric drag is the primary force responsible for re-entry. The junk doesn't have the booster rockets that the ISS does, so it crashes. — Lomn 19:41, 5 November 2008 (UTC)[reply]
If you push is hard enough, it would still work since it would skim the atmosphere (or, rather, a thicker part of the atmosphere - the ISS is still well within the exosphere) once an orbit at perigee and that would lower the apogee until enough of the orbit is in the atmosphere for it to deorbit. --Tango (talk) 19:47, 5 November 2008 (UTC)[reply]
Right. But the point is, it's not just a matter of "push it downward at 1 m/s and it will continue descending toward the Earth at 1 m/s indefinitely", as the previous poster seemed to think. The push just puts it into a different orbit. If the original orbit is circular, the best technique is to push backwards along the orbit, which will make it an ellipse with the apogee where you did the push and a lower perigee on the other side. Make the perigee low enough and the orbit will decay reasonably fast. I don't have time to attempt the math now, but it would take a fair bit more than a 1 m/s push to produce a substantial lowering of the perigee. --Anonymous, 23:14 UTC, November 5, 2008.
As space debris goes, this one isn't much of a problem. It's big, it's easy to track, and it isn't surrounded by a cloud of small particles. Avoiding it is simply a matter of not intersecting its orbit when the refrigeration unit is there. --Carnildo (talk) 22:25, 5 November 2008 (UTC)[reply]
Neptune and Pluto disc color
Since Neptune is 1.5 times farther away from sun than Uranus, it would be 1000 times dimmer than Earth, and Pluto is 2000 times dimmer than Earth how can Neptune still get vivid blue color, and Pluto get apricot color. Bartlett gave me this gives the ture color of planets. I thought Neptune suppose to be dark indigo and almost look nothing 300 meters from space, just feel a swirling mass is coming to me almost black until I come like severals of miles down. Pluto's surface suppose to be almost BLACK, oribting by Pluto's surface I thuoght I will just see a ground over a black-out homes over a deep midnight with no light. --FRWY 23:31, 5 November 2008 (UTC)[reply]
Resolved
