Wikipedia:Reference desk/Archives/Science/2009 May 28

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May 28

Cat physiology

Do cats enjoy chilled water in their bowl? My observation is that they do not, even on hot days. Is there a reason for this? Thanks. Viriditas (talk) 02:26, 28 May 2009 (UTC)

Maybe it is a matter of taste. Try putting identical amounts of room temp and refrigerated water in bowls, and check an hour later how much is left in each. Repeat the next day to make sure. Then try intermediate temps to find the ideal. Maybe someone can make sure that cats are not somehow harmed by cold water. Edison (talk) 03:37, 28 May 2009 (UTC)

Googling for 'cat cold water' finds stuff like this, with some cats demanding ice water from their human slaves. If you see evidence to the contrary then a matter of taste it must be. 62.78.198.48 (talk) 08:01, 28 May 2009 (UTC)

Water from the fridge usually has less oxygen in it than agitated water. If you keep it in a jug, shake the jug before pouring the water. On the other hand some cats prefer mud-puddle water to both tap and bottled water. They usually prefer their food an drink at room temp. Very cold food can upset their stomachs. That is why you shouldn't store cat food in the fridge. (..and don't reheat it in the microwave because that can harden cartilage and collagen pieces in the food and also upset their stomach.) Most of the time, all that will happen is that they'll throw up. They do that without much sign of later discomfort. (Also in case of hairballs.) Cleanup in aisle 2 :-) 71.236.24.129 (talk) 08:00, 28 May 2009 (UTC)

Cats are not as different to dogs as they like us to think. Hot dogs use their tongues for cooling. Cuddlyable3 (talk) 10:16, 28 May 2009 (UTC)

Tongues? Man, they really do put gross stuff in hot dogs. — DanielLC 14:52, 28 May 2009 (UTC)

• Even when our cat has a bowl full of water, he calls us to open up the kitchen door to allow him to go outside and drink rain water. (That cat is full of surprises...) - Mgm|^(talk) 09:57, 29 May 2009 (UTC)

I'm wondering how many cats the OP has observed. My experience with cats and dogs is that they are, like humans, individuals. The soup that my father calls too hot, my friend calls just right; my father once ridiculed me when I said that I didn't think lukewarm water was as thirst-quenching as cold water. It probably isn't any different with pets. They have food preferences (Precious my hot dog loves salmon, Obi my cool dog shares apples with me, and Houdini the dog of my heart utterly adored bananas), so why not temperature preferences as well? As long as what you're giving your cat isn't reheated or so cold as to cause stomach upset, as mentioned above, there's no reason you shouldn't indulge your pet's individuality as long as it's convenient for you. —Preceding unsigned comment added by 66.215.227.218 (talk) 22:34, 29 May 2009 (UTC)

Incubation Period

What is the incubation period of a common sore throat? Isaiasnaruto (talk) 03:26, 28 May 2009 (UTC)

Acute pharyngitis lists a variety of causes for throat inflammation. Any specific one you are interested in? Check out the articles referenced there in case they already have an answer. 62.78.198.48 (talk) 07:56, 28 May 2009 (UTC)

Depends on the pathogen; see Acute pharyngitis and common cold. The latter article gives an incubation period of 2-5 days for a viral infection of the upper respiratory tract. --Dr Dima (talk) 07:55, 28 May 2009 (UTC)

Sound ever transverse?

Our article on sound suggests that sound waves can be transverse when moving through solid media. However, some of my real-life sources inform me this is incorrect. Some clarification would be immensely helpful. —Anonymous Dissident^Talk 08:14, 28 May 2009 (UTC)

I assume your link is to transverse wave. Sound waves always need some kind of elastic media to travel in. There is no error in the Sound article about waves being transverse or longitudinal. I added to the Sound article information that transverse waves are at right angle to the direction of propagation. I hope that helps to clarify. Cuddlyable3 (talk) 10:07, 28 May 2009 (UTC)

(ec):Transverse or shear sound waves are possible in elastic solids. For example, in an earthquake the first seismic waves to arrive are the compressional (known as primary) P-waves followed by the slower transverse (known as secondary) S-waves. S-waves, however, do not pass through liquids and this property has allowed them to be used to show that the earth's Outer core is in a liquid state. Mikenorton (talk) 10:14, 28 May 2009 (UTC)

Yes, I agree. However, there can exist a transverse wave in a gas when the gas (plasma) is at least partially ionized and a magnetic field is present. It is called Alfvén wave. It is not a sound in the conventional sense, though. An ion sound wave (more generally, a magnetosonic wave) can also exist under the same conditions, but it is longitudinal rather than transverse. See Waves in plasma and follow the links for more details. --Dr Dima (talk) 18:02, 28 May 2009 (UTC)

Maximum optical zoom

Is there a limitation for the optical zooming, assuming vacuum case? And what is the maximum practical optical zoom ever made (For examples for telescope and camera purposes)? The reason I ask this question is because of some very high resolution imaging satellites. Thanks again for your help in advance --Email4mobile (talk) 10:15, 28 May 2009 (UTC).

To begin with, you seem to be making the common mistake of misusing the word zoom. The focal length of a lens is (among other things) what determines how large the things you're photographing will appear in the photograph. With a short focal length, or a "wide-angle lens", you might take in a whole landscape. With a long focal length lens, which is often a telephoto lens, you can fill the frame with a small songbird from some distance away.

A zoom lens is simply a lens that can change its focal length. You can have zoom lenses that are entirely wide-angle. Telescopes and earth-imaging satellites are not generally "zoom" optical systems. I think you want to know about upper limits on focal lengths, or the ability to resolve fine detail.

As you increase the focal length of an optical system, you also need to increase the diameter of the lens or mirror to maintain a reasonable f-number, or else you will end up with a very faint image. Increasing the diameter gets harder and harder the bigger you get; first there's the obvious expense of manufacturing a big lens or mirror, but there are also the engineering challenges of getting the lens or mirror to support its own weight without bending (which would ruin the optical quality), or the costs of launching all that weight in the case of orbiting telescopes or imaging satellites.

Furthermore, even if you increase the focal length and diameter, your ability to resolve fine detail when looking at space from the ground, or looking at the ground from space, is limited by atmospheric seeing. Have you ever seen some wavy distortion when you look over a hot grill? A similar phenomenon limits the images from telescopes. Looking up from the ground, your angular resolution is not likely to be much better than 1 arcsecond no matter how big your telescope, unless you use advanced technologies like adaptive optics. Looking down from space, the same phenomenon limits resolution on the ground to about 5 cm. -- Coneslayer (talk) 11:48, 28 May 2009 (UTC)

You do not need adaptive optics: lucky imaging works just as well. Combining several images of the same thing would also improve image quality: this is often used in digital photography, I forget the names of the techniques. Using just ultra-violet could improve resolution more. So if things like this could improve the resolution by - complete guess - ten times, then you are down to a resolution of .5cm. I suppose you would see faces at this resolution, perhaps identify people. The article about the 5cm resolution was written in 1966 - technology will have improved since then. 78.146.211.210 (talk) 23:40, 29 May 2009 (UTC)

Fisrt I'd like to thank you very much for correcting my wrong information about optical zoom; and second awfull thanks for all the valuable explanation summerized in your text :) Coneslayer --Email4mobile (talk) 12:00, 28 May 2009 (UTC).

No problem... it's a complicated subject, and I glossed over a lot in the above discussion. You could spend all day reading the articles I linked to, and the related articles they link to. Feel free to stop back with follow-up questions. -- Coneslayer (talk) 12:15, 28 May 2009 (UTC)

Military satellites are known to be able to resolve down to 10cm - it is believed that they are able to recognise individual human faces, and there were claims in the 1970's that a satellite from that era could read license plates on cars...which I think means we're down to a centimeter or so. However, the very best stuff is classified - so the best we KNOW they can do is 10cm...which is about what you get on Google Maps in their high res city centers (although in that case the high-rez pictures come from Aerial photography - not satellites). SteveBaker (talk) 14:02, 28 May 2009 (UTC)

A limit comes from diffraction on the aperture. The larger your front lens is, the better is the limit resolution. Assuming a circular aperture (diameter $d$) and looking at objects close to the optical main axis, the Rayleigh's criterion (see the same link; its use is subjective and the limit is not rigid) says that from distance $\ell$ the smallest resolvable object can be $1.220{\tfrac {\lambda \ell }{d}}$ wide. $\lambda$ is the wavelength, thus, you can see sharper in blue than in red. With your eye's $d\approx 0.5\,\mathrm {cm}$ and green $\lambda \approx 530\,\mathrm {nm}$, from $\ell =10\,\mathrm {m}$ you can resolve two points up to $1.3\,\mathrm {mm}$ apart (try it, I have!). From a satellite's $\ell \approx 300\,\mathrm {km}$ and with a reasonable $d\approx 1\,\mathrm {m}$ (the same $\lambda$), we get $19.4\,\mathrm {cm}$, which really is about the resolution of the Google Earth satellite images: the better ones have already likely been taken from airplanes. — Pt _(T) 14:25, 28 May 2009 (UTC)

I would expect even the 20cm ones have been taken from planes. 20cm resolution from satellites is achievable, but it's not easy. --Tango (talk) 17:04, 28 May 2009 (UTC)

Respondents have assumed the OP is asking about the limit of a fixed telephoto lens. However zooming means changing the focal length of a lens while keeping the scene in focus. A limit to the ratio of a zoom lens is the increasing complexity of its design. Here is The World's First Triple Digit Zoom Lens Cuddlyable3 (talk) 10:32, 29 May 2009 (UTC)

the op might find the article superlens interesting.just-emery (talk) 17:09, 31 May 2009 (UTC)

Live Google Maps

With the current technology, is it possible to have a live Google Maps kind of thing, where we can zoom in on any part of planet earth to see people walking, birds flying, river flowing, traffic moving and sharks swimming? Is there any such service already in existence? I guess not, at least to such extreme level of precision. If not, when can we expect such thing (if ever) and how difficult is it to get there in comparison to where we are today. Thanks - DSachan (talk) 12:27, 28 May 2009 (UTC)

No, it isn't possible. The true-color images we see in Google Earth come from the imagery of a finite number of satellites, and (as I was surprised to learn) aerial photography. In order to have a "Live" Google Earth, you would need millions, if not billions, of satellites, all sending immense amounts of data per second, to be integrated and stitched in short enough time to be considered "live". I'm not sure that this will even be possible, never mind practical or worth the tremendous cost, for more than 100 years.

Now, if you're willing to sacrifice some spatial resolution, in a way we already have what you speak of: the GOES satellites send imagery at a resolution of a few kilometers every 15 minutes, and together have coverage of the entire planet (though the resolution declines as you approach the poles). I see no reason why in the near future we couldn't have near-real-time views at this spatial resolution, although I'm not sure anyone would be able to justify the cost.-RunningOnBrains^{(talk page)} 12:47, 28 May 2009 (UTC)

(edit conflict) Not now, and not likely. Imagery satellites are typically in orbits where they only pass over a particular point on the earth for a brief period, typically every few days. They cannot provide persistent motion imagery, nor image a particular location whenever you want. I was surprised to see in Satellite_imagery#Moving_images that a company planned to put an imaging satellite in geosynchronous orbit to provide ongoing live video; note, however, that because of the high orbit, the resolution would be very poor (250 meters). That's not good enough to see the kinds of things you're asking about. -- Coneslayer (talk) 12:52, 28 May 2009 (UTC)

Also - satellite photography has to be done on a more or less cloudless day - and if you want it to look any good, sometime close to midday. But the highest resolution commercial satellites produce really terrible spatial resolution - 5 meters, I believe. You can buy imagery from the Russian military at perhaps 1 meter accuracy. US military satellites can reach 10cm or better...but that imagery isn't for sale! There is a 'gentlemans agreement' amongst satellite photography sources not to sell better than 1 meter accuracy data to anyone other than government agencies because of the obvious privacy issues. (They chose that number because it makes recognition of individual humans impossible).

Aerial photography is therefore the only way to get high resolution imagery - and it's expensive.

So certainly, we're nowhere near even close to being able to do this. But even if we were - consider the bandwidth requirements. Most of the high res stuff in Google maps is about 10cm resolution. The surface of the earth covers 510,072,000 square kilometers - even if we ignore the oceans, that's still 148,940,000 square kilometers. At 10cm resolution, that's 14,894,000,000,000,000 pixels. About 8,000 of the largest hard drives you can buy. If we updated it every second, that's something like 24,000 terabytes per second! There is no known transmission medium that could possibly get even a tiny fraction of that from satellite down to the earth! This is so far away from being possible! Consider satellite TV - they typically have about 1.6 Gbits/second (per satellite) of down-stream bandwidth. It would take about a quarter of a million satellites of that kind of performance to transmit the data down to us...for the land alone. If you wanted to do the oceans too - you'd need a million satellites!

No! SteveBaker (talk) 13:56, 28 May 2009 (UTC)

FYI, you can buy commercial satellite imagery from US companies with sub-meter resolution these days. -- Coneslayer (talk) 14:00, 28 May 2009 (UTC)

You would need to make it on-demand - the satellites only transmit the data that is wanted at that moment (that would increase latency slightly, but not too much). The bandwidth isn't really a problem, it's the sheer number of satellites you would need to have constant global coverage. You could use fewer satellites by having them higher, but that would lower the resolution. Getting 10cm resolution from a geostationary satellite, for example, would require technology well beyond current level - you're probably talking decades until we can manage that. --Tango (talk) 14:06, 28 May 2009 (UTC)

Maybe what you want are webcams. Start with Webcampedia. You can certainly see all that stuff on webcams (including "sharkcam").--Shantavira|^{feed me} 14:22, 28 May 2009 (UTC)

Really what you want is to have access to security cameras, then in a place like Britain you could check on people all day long and with the need be secure against terrorism we'll hopefully soon have cameras and microphones inside the houses too, except for politicians of course because what they do is so sensitive. We could start with a law that all webcams are permanently accessible to the security forces at lease though you really need other people like for instance schools to be able to use them to make certain people are applying from the appropriate area. The more eyes are watching the less chance they have to get away with their crimes. RIPA details the advances Britain has made along these lines. Dmcq (talk) 15:33, 28 May 2009 (UTC)

Telescreen springs to mind. Smartse (talk) 17:11, 28 May 2009 (UTC)

See Talking CCTV - what a disgrace we have these in Britain! 78.147.139.18 (talk) 23:18, 28 May 2009 (UTC)

"If you have nothing to hide, then why worry?". Double plus good! Fribbler (talk) 15:58, 28 May 2009 (UTC)

You joke, but I remember a news story a year or two ago about a town (in the UK, I believe) that started broadcasting its CCTV on a local TV channel (so, CCTV is a misnomer, I guess!) so residents could help spot crimes as they occurring and inform the police. I don't know how successful it was or if the scheme is still running and can't find it now. --Tango (talk) 16:14, 28 May 2009 (UTC)

What?!? have you got a link? Smartse (talk) 17:11, 28 May 2009 (UTC)

As I said, I can't find it now. I'll have another look, though... --Tango (talk) 17:23, 28 May 2009 (UTC)

Here's the original news story,[1] and an update with comments.[2] Apparently the pilot scheme in Shoreditch has finished but a second phase is in the planning. Mikenorton (talk) 17:42, 28 May 2009 (UTC)

I think its dreadful that in some northern UK town - Middlesborough? - they have a tannoy system where the security droids can bark out commands at the public. I'm surprised that nobodies rioted about that yet, they would do in the south. Its truely 1984. Spy satellites - a few years ago I remember reading something about them. Many or most of them see in the ultraviolet, because that has least distortion through the atmosphere, as far as I recall. They can see fag packets. Most observation satellites see in various wavelengths and create false-colour images. True-colour visual wavelength images may be in the minority. I expect the cleverest satellites could use astronomy techniques in reverse, such as lucky imaging. 78.147.139.18 (talk) 23:09, 28 May 2009 (UTC)

The technology is available to "populate" Google Map-type images with computer generated moving vehicles and people. You can even be one of them, see Second life. Cuddlyable3 (talk) 10:19, 29 May 2009 (UTC)

Does heat contribute to production or increase in PCB's (Polychlorinated Biphenyls)

Can intense heat cause production of, or, an increase in the amount of Polychlorinated Biphenyls (PCBs) in new Non-PCB transformer oil over time?209.26.182.3 (talk) 14:52, 28 May 2009 (UTC)

Seems unlikely, but the chemists on the board can weigh in on the possiblity of PCB being created from the heating of mineral oil or silicone coolant. If a transformer once had PCB contaminated oil in it, but was flushed until it tested PCB-free, I supposed that operation at high temperature could free up a bit more PCB from the windings. There was a time when utilities allowed PCB to contaminate mineral oil cooled transformers by the common use of tanks and filter presses, so there were so many parts per billion of PCB found in equipment which did not start out with PCB or "Askarel" (trade-name). High temperatures reportedly caused PCB to turn to dioxin, which was supposed to be worse than PCB. Edison (talk) 19:06, 28 May 2009 (UTC)

No. As far as I know, no commonly-used transformer oil type (mineral, silicone, or fluorocarbon) contains any chlorine. It is therefore impossible for any chemcal reaction involving the oil to generate a polychlorinated biphenyl. TenOfAllTrades(talk) 19:23, 28 May 2009 (UTC)

What is needed to heal Humanity's ills?

Say by some great miracle, all religious/tribal/political countries/factions/groups in the world agreed to a 5 year truce with each other. Meaning, no violence, retaliation, nothing. What can humankind do during this time of peace to get reduce of world hunger, make education and healthcare more available to everyone? For instance, what should the US do first in this opportunity? I always thought that if everyone was well fed, had access to healthcare and all types of education, this world would be a very different place meaning less violence and more social awareness and a reduction of the human population. --Reticuli88 (talk) 16:35, 28 May 2009 (UTC)

Of course, from where do you get food, health care, or education? Those things require people to do work in order to provide people with them. Farmers need to grow food; truckers need to transport goods around, teachers have to, well, teach. So how do you recompense those people? Plus, if people receive food, shelter, education, and healthcare for absolutely no cost at all, then what is the motivation to work? Why should I be a teacher if I don't need any money to buy my own food and put my own kids through college? Why be a farmer if I have no motivation because I am so well taken care of I have no reason to work hard? See? Sometimes its not all that easy. --Jayron32.talk.contribs 16:53, 28 May 2009 (UTC)

Teachers and farmers are not doing it for the money. The motivation for work, real work, not digging ditches and cleaning toilets, comes from within. The concept that people are motivated to work hard because there is a carrot dangling in front of them doesn't address the fundamental problem. People like Abraham Maslow have addressed some aspects of this motivation, and John Neulinger proposed creating a society that was based not on work as we know it, but on work redefined as leisure, where leisure is pursued for its intrinsic reward. But the question proposed by the editor is flawed, since fear and "violence" from "religious/tribal/political countries/factions/groups" is encouraged at every level of society, and governments want their citizens to have as many people as possible to increase the tax base. We know that the higher the population density the more social and ecological problems result, from crime to mental illness, to pollution and resource extraction. In a world where people are treated as "consumers" (a recent invention of the last century) and where accumulating wealth is the highest human value, scarcity will be the result. The kind of "peace" that Reticuli88 talks about is an important issue for psychology. See also inner peace. Viriditas (talk) 21:00, 28 May 2009 (UTC)

Some teachers and farmers are not doing it for the money. At least, its easy for them to say that when they are recieving a living wage AND still have real pressures to do SOMETHING for work. The neat thing is that someone did the experiment and we actually have data on this. See Kolkhoz for what happened when farmer's WERE'NT doing it for the money any more. Strangely enough, the stopped farming really well, and an entire nation starved. People in collective (that is, on average) will only work as hard as they have to and no more. Individual, anecdotal examples exist of a person working harder just for the sheer joy of it. But in the bulk, people don't do that. --Jayron32.talk.contribs 00:37, 29 May 2009 (UTC)

Most teachers are not doing it for the money. They do it because they are interested in education and they tend to be "idealistic and altruistic" about why they teach.(Goodlad 2004:171-173) As for farmers in the modern world, "economic considerations now make it difficult for farmers to earn a living at farming, because farm costs have been rising much faster than farm income." For farmers in the United States, "the lifestyle was highly valued by older generations", and "people used to expect no more of a farm than to produce enough to feed themselves."(Diamond 2006:57-60) So it wasn't about money, it was about feeling good about your work and being able to be self-sufficient and raise your family. This is true for any profession. Why do mathematicians work hard at math? For the money? Of course not. They do it because they love it. Viriditas (talk) 03:21, 29 May 2009 (UTC)

You appear to be asking for a discussion about what might happen if some other rather impossible event were to occur. This is not a discussion forum. This is a reference desk. If you have a question that might possibly be something that has been studied and reported on in a respectable resource, please ask. If all you want is a discussion, please use one of the thousands of discussion forums available on the Internet. -- kainaw™ 17:02, 28 May 2009 (UTC)

Absolutely. We can refer you to a variety of philosophical, economic, and political theories, but this is not the place for a long and drawn-out discussion. Maybe you can start with utopia. That article is a great introduction and is full of links to numerous theories spanning the gamut from communism to fascism, feminism to individualism to mass annihilation. Personally, my favorite quote regarding utopia comes from an unlikely source, "The Khmer Rouge leadership boasted over the state-controlled radio that only one or two million people were needed to build the new agrarian communist utopia. As for the others, as their proverb put it, "To keep you is no benefit, to destroy you is no loss."" (Let me be clear - I don't condone this statement or the genocidal actions it represents - but I feel that it succinctly summarizes the problem that one man's utopia is not necessarily the same as the next). For virtually every atrocity historians can attribute to human activity, somebody thought it was a good idea. Nimur (talk) 17:11, 28 May 2009 (UTC)

It seems unlikely that poverty and crime would disappear with the end of war and conflict, even places that have known peace for many decades (Sweden?) have crime and poverty. In many places people do have free access to education and healthcare, but are still afflicted by the problems you mention to some degree (although hunger has been stamped out even among the poor among most of the industrialized world). I think historically urbanisation has reduced human birth rates much more effectively than eliminating war or reducing poverty. I think it should also be remembered that the well being of the world's people is improving, as described in this TED talk. To me, rather than an end to wars what the world really needs is good government. I would define that as largely transparent with as little corruption as possible, and being responsive to the populace without pandering to short sighted populism that is a problem even in the first world (like in, say, California). In my opinion a mostly free economic system is also paramount, as well as means for people to improve their status in society and better themselves, education as the great equaliser and all that. But while I think a world without wars is possible, a world without violence and theft is not, they seem to me inseperable from the human condition. TastyCakes (talk) 17:04, 28 May 2009 (UTC)

I agree with TastyCakes, corruption is the main thing to get rid of. If you achieve that, then I think hunger would all but disappear. Growing enough food to support the current world population isn't difficult, the problem is getting it where it is needed. Getting rid of hunger and poverty isn't likely to reduce violence, though. While some people are violent because they need to be to get the essentials to live, most people do it for reasons of power. There is always going to be a finite amount of power available so people will always fight over it (at all scales of existence - domestic violence is to do with power in a family, gangs fighting in the streets is about power in a particular sector of society, civil wars are about power in a country, regular wars are about power in a region, or even the world). --Tango (talk) 17:13, 28 May 2009 (UTC)

How is this a science question? Seems like a forum topic anyway - i don't think anyone in the world could answer this, let alone the reference desk.YobMod 17:16, 28 May 2009 (UTC)

That's a strange answer. Many people have attempted to answer this question, particularly in the fields of psychology and engineering. Buckminster Fuller, Paolo Soleri, and K. Eric Drexler come to mind, but the list is much larger than that. Futures studies addresses these types of questions, and Reticuli88 should be pointed in that direction. Viriditas (talk) 20:38, 28 May 2009 (UTC)

That some people who have approached philosophical questions happen to have had scientific backgrounds does not make the question about science. All we have is speculation - where are the testable hypotheses? The consequences of an impossible situation can not be scientifically explored. Eg, Stevebaker's reply after this suggests people reproduce more after a war. It may be true , but with only one example and absolutely no controlled studies, it is not a scientific answer (not that he claimed it to be, except by putting it on the science ref desk). I predict that world-peace would inspire an hysterical epidemic of religiosity, resulting in a huge drop in birth-rate as people prepare for the Rapture. The fact that i have 2 degrees in sciences does not make that a scientific prediction.YobMod 12:53, 29 May 2009 (UTC)

Let's try to find some generalities that might apply to this hypothetical situation: When wars end - people make more babies. The present 'baby boomer' generation are the consequences of the end of the second world war. So I'd expect one consequence of the end of all of these conflicts would be a jump in world population. That's really not a good thing. SteveBaker (talk) 21:52, 28 May 2009 (UTC)

I suspect if there really were a five year truce, many people would use this period to, well, stockpile weapons, train armies, and spy on their enemies. Otherwise, when the five years are up, they're going to get trampled by their enemies who have been busy doing the same. Dcoetzee 21:59, 28 May 2009 (UTC)

As to why Dcoetzee's answer is probably the best one, see Game theory. There are four outcomes here: Both nations disarm, Nation A does and Nation B does not; Nation A does not and Nation B does, and no one disarms. This is a classic Nash equilibrium whereby the best possible outcome (all countries disarm) cannot be reached because two of the three other outcomes (one country disarming while the other does not) is so catastrophic for the peacenik nation that the fourth option (both countries stockpile weapons) is the only stable equilibrium. Its a classic case of the prisoner's dilemma. See also Balance of terror for the classic application of the prisoner's dilemma to military strategy. --Jayron32.talk.contribs 00:31, 29 May 2009 (UTC)

The problem is that this is NOT a prisoner's dilemma situation. At worst, it's a "Continuously iterated prisoner's dilemma" - the same test happens over and over and you can learn from what happened in previous rounds. At best, it's not a prisoner's dilemma at all - because the players can communicate. That radically shifts the results. SteveBaker (talk) 01:54, 29 May 2009 (UTC)

Except that the communication is meaningless. You can TELL the other nation you want to reduce your armaments together, but do you TRUST your enemy? If you don't trust what they tell you, its just as good as not talking at all. And the net result is ultimately the same; the payoff matrix for the "Do we build weapons or not" game is identical to the prisoner's dilemma payoff matrix, and you ultimately always end up with the same equilibrium result. Both look like this:

	Disarm	Stockpile Weapons
Disarm	WIN BIG/WIN BIG	WIN BIG/LOSE BIGGER
Stockpile Weapons	LOSE BIGGER/WIN BIG	WIN A LITTLE/WIN A LITTLE

See Peace war game, which discusses (with refs) exactly what I was talking about. --Jayron32.talk.contribs 02:03, 29 May 2009 (UTC)

NO!!!!!! it's not like that! You've completely failed to understand what the prisoner's dilemma teaches us.

In the true prisoner's dilemma you have no information about how the other person is behaving right now or is likely to behave in the future. So you have no information on which to make your decision. It's also an all-or-nothing thing. In the disarmament scenario - you can slowly ramp down your arms production and watch to make sure that the other guy does the same thing - every round of defense-funding decision-making becomes another game of prisoner's dilemma. Hence it's an ITERATED version - and game theory predicts utterly different conclusions under those situations (read the article AGAIN!). In an iterated system, your chart looks like this:

	Reduce armaments by 1%	Increase armambents by 1%
Reduce armaments by 1%	Win a modest amount/Win a tiny amount	Win a tiny amount/Lose a tiny amount
Increase armaments by 1%	Lose a tiny amount/Win a tiny amount	Lose a tiny amount/Lose a tiny amount

You can even look back at how the other guy has been doing in the past. If he rearms a bit when he says that he won't - you can arm yourself a little more as 'punishment' in the next round. In this "iterated" prisoner's dilemma, there is a clear strategy that always works - as demonstrated by a very famous computer simulation/game (which you can find out about in the article). "Tit for Tat". You start out as "Mr Nice Guy" - but if/when the other guy screws you over - you punish him on the following round - then you go back to being Mr Nice Guy. That stategy is utterly unbeatable over the longer term when there is no communication between players other than the game results. But even more than that - if you have communication, you can try to make it clear the rules by which you are playing - with openness in your processes (everyone can see your military expenditure budget BEFORE that gets turned into weapons manufacture) - then it becomes clear that you are playing Mr Nice Guy - and your opponents can benefit by doing the same.

So this is NOT the classic Prisoner's Dilemma - unless you play the game like North Korea currently is (which is closer to the classical version of the game - and has results that are probably going to play out very soon). North Korea's government see this as a one-off event because their stability is at risk and they know that if they screw up - the could be deposed and there is no second chance...their insular policies and closed borders mean that there is none of the information flow needed for a communicative/iterative version of Prisoner's Dilemma - and the consequences are exactly as game theory predicts.

When people cooperate and are open - you get things like the de-escalation towards the end of the cold war. But that only happens if you talk to each other and regard it as an iterated game and not a one-off. That requires a stable political system - and explains why stable/open governments spend less time at war than unstable/closed governments.

SteveBaker (talk) 14:47, 29 May 2009 (UTC)

This reminds me of that Jack Handy quote:

I can picture in my mind a world without war, a world without hate. And I can picture us attacking that world, because they'd never expect it.[3]. TastyCakes (talk) 20:18, 29 May 2009 (UTC)

"An excess of virtue is to be feared more than an excess of vice because only the latter is subject to the moderation of conscience." I devoutly hope not to see the so-called great miracle that the OP anticipates would give an opportunity to impose a US-centric one-size-fits-all ideology on everyone. But a "reduction of the human population" can be done in many ways, few of them nice. Cuddlyable3 (talk) 10:08, 29 May 2009 (UTC)

Well there you have it, I think the consensus is we should have a big war or preferably a plague that decimates us. Perhaps I'll build a huge robot that goes WARNING!!! WARNING!!! CRUSH!!! KILL!!! DESTROY!!! as it goes about its work. Dmcq (talk) 15:13, 29 May 2009 (UTC)

Would it have red glowing eyes? I think it should. SteveBaker (talk) 22:15, 29 May 2009 (UTC)

The trouble, Reticuli88, is that just about any good-hearted person basically knows what we would all have to do to cut the nonsense and play nice (and basically, it consists of everyone, well, deciding to cut the nonsense and play nice) - but getting everyone to implement the solution all at once? Impossible. - AJ —Preceding unsigned comment added by 66.215.227.218 (talk) 22:15, 29 May 2009 (UTC)

Robert LeFevre (i think) pointed out the difference between negative rights and positive rights thus: If everyone suddenly resolved to refrain from force and fraud, negative rights would immediately be satisfied (except for human error); but even that miracle is not enough to fulfill positive rights, even if we agree on what those rights are, because no one knows enough about what other people need.

If this were a discussion forum, which it isn't, I'd assert that most of the world's poverty and deprivation is caused by states' active prevention of economic activity. Religious and tribal antagonisms are usually only a pretext for the political class to consolidate their control and exploitation. —Tamfang (talk) 19:14, 3 June 2009 (UTC)

Cerebral Hemispheric Dominance

Is this article correct? I thought that it's a myth. —Preceding unsigned comment added by 194.90.167.67 (talk) 18:22, 28 May 2009 (UTC)

Well, it does read like an essay and not like an encyclopedia article. I'll give it a thorough look through later. Livewireo (talk) 18:30, 28 May 2009 (UTC)

And its been written almost entirely by one editor who has only made edits to the article. Livewireo (talk) 18:34, 28 May 2009 (UTC)

Would a redirect to Lateralization of brain function be more appropriate here? It would seem that the two articles cover much the same topic, and the Lateralization of brain function article is much better written... --Jayron32.talk.contribs 02:10, 29 May 2009 (UTC)

You're going to throw away an entire article that someone went to great trouble to write simply because of the writing style. Talk about judging a book by its cover. Further, laterization and dominance are 2 different subjects. I'm sure that volumes could be written on dominance but if it redirects to a completely different article then it will get relegated to a mere paragraph or two, Wikipedia is merging too many articles and is becoming much less useful because of it. just-emery (talk) 17:16, 31 May 2009 (UTC)

Beware the labor theory of value; no matter how much trouble someone spends on writing twaddle, it remains twaddle. Besides, it appears that Julie.summey has spent only two hours on Wikipedia, so she might well not notice if it's undone. —Tamfang (talk) 22:19, 3 June 2009 (UTC)

If you disagree with the article then why not help edit it? Also the article has a discussion page for the editers to discuss questions like this.just-emery (talk) 17:30, 31 May 2009 (UTC)

Motor Oil

My car's owners manual recommends using 10W-30 grade. I have a case of 10W-40 which I would like to blend with another grade so the mix is approximate to 10W-30. Can I do this? What other grade do I need to buy, and what proportions do I need to use? —Preceding unsigned comment added by 75.36.216.34 (talk) 18:46, 28 May 2009 (UTC)

With very rare exception, it is always best to follow the owner's manual's reccommendation. Is it possible to simply return the oil to the place of pruchase and exchange it for the correct weight? That would easier and less costly than buying more oil and then having to mix the two. cheers, 10draftsdeep (talk) 19:01, 28 May 2009 (UTC)

In general, you can't just mix different grades of commercial motor oils and expect them to work appropriately. We have information on the grades of motor oil at Motor oil#Grades. One difficulty you'd face in mixing oils is that oils with designations such as 10W-30 or 10-W40 are multi-grade oils, meaning that they have special additives which allow them to perform like different oil grades at different temperatures. Matching the exact performance characteristics at differing temperatures would thus be very difficult. Even matching a single weight oil wouldn't be trivial, as the number designations are based on the kinematic viscosity of the oil, which isn't going to be linearly additive (that is, mixing equal part 10 weight oil and 30 weight oil is not going to get you the equivalent of 20 weight oil), especially when potential non-newtonian fluid behavior is taken into account. Leave motor-oil mixing to the professionals, who have proper test lab facilities. -- 128.104.112.106 (talk) 19:37, 28 May 2009 (UTC)

All of that is technically correct, as it should be in an encyclopedia. That said, though, the odds of negative consequences from tossing one quart of 10W40 into your engine now and then are "slim to nil".

10W40 will be slightly more viscous when hot. If you have an old enough engine, where you're actually burning through a quart of oil periodically, then a bit more viscosity is not a bad thing. At the other end of the calendar, the 10W components are "close enough" for winter use.

So, it's a case of theory vs practice. Theoretically, don't do it. Practically, it don't make much difference.

--DaHorsesMouth (talk) 20:31, 28 May 2009 (UTC)

Drain the old oil and do a proper full oil change using, if you want, your supply of 10W-40. Your engine will thank you. That is better than experimenting blindly with a mix of two oils that become increasingly different in viscosity as the engine heats, and they might not even stay blended. Change the oil filter too.Cuddlyable3 (talk) 09:54, 29 May 2009 (UTC)

I have mixed different oil viscosities several times, with no perceptible harm to my engine. Oil grades cover a range of viscosities... some 10W30 oils are a bit thicker/thinner than others. Your engine will not grenade if you are a little bit off in your mixing skills. That said, the simplest solution would be to return the oil for the proper grade if possible. If not, adding a quart or two of 10W40 to each oil change should be quite safe. 75.157.28.248 (talk) 20:15, 29 May 2009 (UTC)

Poor TV picture improves a lot when VCR on

I live in an area with a low signal strength. I have a 20db (as far as I recall) signal amplifier between the tv and the aerials coaxil cable. Even so, sometimes the image becomes very hazy and difficult to see - it looks exactly as I would expect from a low signal strength. But when I press the appropriate button on my remote, the TV takes the aerial input via a VCR, and the picture becomes perfect, crystal clear! So the signal goes aerial - 20db amplifier - VCR - scart lead - tv. Yes, I still have and use a VCR.

My question is - is this simply due to the VCR adding some extra amplification to the 20db amplifier? Or could there be some other reason? Could I get the same result by buying an even more powerful signal amplifier, or by putting two in series? I assume that although the signal is weak, the signal/noise ratio must be good. It is several times cheaper to buy a new amplifier than upgrade the tv aerial. A subsidary question is why the signal seems to be much worse for several minutes at a time, and then improve again? 78.147.151.201 (talk) 21:25, 28 May 2009 (UTC)

Does your aerial go into your VCR or tv first? I would expect that whichever is the system that gets the 'mains' aerial would be the one that gets the best reception. Also are you definitely taking the signal from the best location? I know where I am I can get a couple of different signals - my strongest one being from Emley Moor. It may be that you should check that to make-sure as well. Perhaps your VCR has better decoding/system than your tv? My old digi-box is much worse than my new one, even though the aerial hasn't changed. ny156uk (talk) 22:57, 28 May 2009 (UTC)

The aerial goes into the VCR first, and then there is another short coaxil cable from the VCR to the TV, as well as a scart cable that is in use when the VCR is on. But you still get a picture when the VCR is turned off. I thought the aerial signal just went straight though the VCR without being changed in any way. The aerial is definately pointed at the nearest and best transmitter, which is some way away. I have not bought a digital radio because the signal is not good enough, and the tv signal is not good enough for digital tv either. 78.147.139.18 (talk) 23:37, 28 May 2009 (UTC)

So you have the coax from the aerial going through a splitter with one output going to your TV and the other going to your VCR? I'm betting a poor quality splitter. It's pretty common for cheap splitters to give a better signal to one output than to the other. Especially the old fashioned T shaped ones. APL (talk) 01:11, 29 May 2009 (UTC)

No, the signal goes to the VCR, then through the VCR to the TV. I imagine there is merely a plain connection between the in and out coaxial sockets. It still functions when the VCR is off. The same thing happened when I used other VCRs. 84.13.164.142 (talk) 09:10, 29 May 2009 (UTC)

Not to be picky on this, but do you live in an area that is undergoing mandatory transfer to Digital TV? In the U.S. for example, all over-the-air analog televison will cease on June 12, 2009. I believe the UK and Canada have 2-3 more years; but it may be something to think on as analog TV becomes less and less availible. --Jayron32.talk.contribs 00:22, 29 May 2009 (UTC)

See also Digital television transition. --Jayron32.talk.contribs 00:23, 29 May 2009 (UTC)

I am well aware that this area will convert to digital tv in the future. But that does not have any bearing on the current problem. As I mentioned, the TV signal is currently too weak to allow recieving digital tv. I think the signal strength is going to be increased when the digital switchover occurs in this region, so hopefully I will be able to get it then. TV is not very important to me. 84.13.164.142 (talk) 09:34, 29 May 2009 (UTC)

Geolocate puts this poster in Liverpool. (Which brings to mind a different question: Does the UK still have television police? I recall years ago seeing a story where authorities were tossing televisions out of second-story windows if the owner didn't have the proper paperwork.) -- Tcncv (talk) 01:22, 29 May 2009 (UTC)

Well - you're exaggerating wildly...but the essentials are true. In the UK, the free (and advert-free) BBC television and radio stations (probably the highest quality broadcast anywhere in the world) are funded by the "Television License" - effectively a tax. If you have a television - you have to buy a license. I forget how much it is - but we're talking over 100 pounds a year. It's not funded from central government taxation because the BBC is required to be independant from the government in order that they may criticize them and hold politicians feet to the fire without being concerned about having their funding withdrawn. Hence, lots of people don't pay the license fee.

In order to enforce the system, there are 'Television detector vans' that drive around to houses that don't have TV licenses and they use a directional antenna to pick up secondary radio waves created in the process of decoding the TV signal. They can detect to a fair degree of accuracy where the TV is in the house. Armed with this information, they can come to your door and demand to see your TV license - and if you don't have one, you get fined. I suppose it's possible that they might be empowered to confiscate your TV if you continually break the law - but that's not a common thing. No - they certainly don't toss your TV out of second floor windows!! And no, they aren't police officers - they are tax collectors.

Americans are frequently horrified at this concept. But I should explain that the process is essentially no different from the car taxes you pay in the USA for the privilege of driving on the public roads. If you get stopped for not having your car tax paid up to date - you get fined...same deal if you get caught operating a TV without a license in the UK. It's arguably unfair that you pay the same car tax whether you drive 100 miles a year in a tiny MINI Cooper or 100,000 miles a year in a honking great SUV. It's arguably unfair that you pay the same TV license no matter how much you watch the BBC...but that's life. Having experienced US "free" television - I can tell you that the TV license is an absolute bargin. SteveBaker (talk) 01:42, 29 May 2009 (UTC)

Well, there's a difference, though. When you're driving on public roads, you are, not to belabor the point, driving on the public roads. You're taking up space that could be used by other drivers. When you're just sitting in your private space, intercepting the EM radiation that the government shoots through you whether you like it or not, it's hard to argue that you're putting any burden on that resource. --Trovatore (talk) 03:08, 29 May 2009 (UTC)

As with many things American, SteveBaker, "your mileage may vary" as the expression goes. In Michigan, your classic MINI (pre-1983) would have a license fee based on weight but your new one would have been charged based on MSRP price. I don't know of any states that charge by mileage yet although I have heard of such proposals. Rmhermen (talk) 05:54, 29 May 2009 (UTC)

...but if everyone use that as an argument then a much greater burden is placed upon the people that are willing to pay. It's more about fairness than about whether you are using a finite resource. --antilived^{T | C | G} 03:58, 29 May 2009 (UTC)

Not being allowed to listen to electromagnetic radiation that someone sends through your residence is a bit like not being allowed to listen to a loud argument by the couple living in the next apartment, or not being allowed to read a flyer thrust through your mail slot. If they don't want you to enjoy the broadcast, they should not send it into your property. (Just a Yank view of things.) Edison (talk) 04:42, 29 May 2009 (UTC)

Edison - If the BBC encoded the signal and charged you a monthly/annual fee for use of a decoder/their decoding algorithm would that be better? Essentially that's what pay satellite tv companies such as Sky tv do. Seems that the bbc method is better in my view (though obvious sky is through satellites but they work to receive signals in much the same way). ny156uk (talk) 07:39, 29 May 2009 (UTC)

In my opinion, yes, the encryption option is much better. For one thing, if you wanted to use your TV only to watch private stations, and not the BBC at all, you could do that and not pay for the BBC. (There are private TV stations in Britain, right? I haven't been there in a couple decades and I don't think I watched any TV while I was there, but I thought I had heard that by now there were private stations. If not, well, you could watch Dutch or French TV.) --Trovatore (talk) 10:13, 29 May 2009 (UTC)

The worst thing about the current BBC license system is that if you do not watch tv, do not have any tv in the house, do not watch it on the internet either, and thus are not required to pay the license fee, then you still get frequently and truely harrassed by many threatening letters commanding you with threats to buy a liscense. The letters really are upsetting and even when you tell the licensing people that you do not have a license, then the threatening and hysterical letters keep on coming. 84.13.164.142 (talk) 09:16, 29 May 2009 (UTC)

Yes, we Americans have the pleasure of watching 12–15 minutes of commercials every hour. I actually think there are advantages to the British system. Several shows are rebroadcast on our PBS stations or are picked up on some of our cable networks. I especially like the science and technology coverage. Most of the best are of British origin. And it is refreshing to see a comedy that is based on wit rather than the slapstick, and dramas that don't feel compelled to lead with some sexually suggestive scenario as if there were no other way to get the audiences attention. Of course I realize that what we see is a non-representative fraction of British broadcasting. I'm sure you have your trashy shows too. But in general, I can see there are advantages to the pay system – more emphasis on quality that there would be in the pursuit of the advertising dollar. (POV alert!) We on the other hand have Lost – a drag-u-drama with no apparent plot, that seems made up from week to week, but for some reason has a huge loyal following. (Diving for cover now.)

Oh, and I do clearly remember seeing a television tossed from a window, bouncing off a porch (?) roof, and crashing to the sidewalk below. Likely part of some high publicity enforcement back in the 70's. They had the electronic detection trucks then too. -- Tcncv (talk) 05:27, 29 May 2009 (UTC)

Getting back to the original questions... 84.13.164.142 (talk) 09:10, 29 May 2009 (UTC)

The OP's TV takes its signal at its aerial connector when the VCR is off and at its SCART connector when the VCR is on. Possibly the tuner or i.f. signal amplifier stages in the TV (which are bypassed by a SCART input) are failing. Older TVs with mechanical tuners, and the dual-standard 405/625 TVs once sold in the UK, are plagued by unreliable switch contacts. Cuddlyable3 (talk) 09:45, 29 May 2009 (UTC)

The TV is a year or two old. 405 transittion ended decades ago, so a TV capable of recieving 405 would be a musuem piece. 84.13.164.142 (talk) 09:47, 29 May 2009 (UTC)

Tuner - that's an interesting point. Could it be that the VCRs tuner is more tuned in than the TVs tuner is? That the problems are caused by the Tvs tuning drifting off? When listening exclusively to one channel only on FM radio, the tuner often seems to need adjusting. Perhaps the tuning is affected by day or night. 84.13.164.142 (talk) 12:15, 29 May 2009 (UTC)

Problem probably solved. The coxial cable socket on the Durabrand tv seems to have a loose connection with the internal circiutry, and I can reproduce the bad picture if I wriggle it around. So I will take the back off and see if I can tighten something up without electrocuting myself from the capacitors. 78.146.211.210 (talk) 21:05, 29 May 2009 (UTC)

Coaxial aerial sockets are a weak point on many TVs. They are often held by solder to a printed circuit board and the solder joint fails because of mechanical stress. Cuddlyable3 (talk) 18:40, 30 May 2009 (UTC)

determining diet via feces

It is my understanding that biologists can determine an animal's diet via examining it's feces (I'm sure it is a bit more complicated than that). What I'm wondering is if scientists can tell if an animal is a herbivore, carnivore or omnivore by examining fossilized feces? In other words can we tell what the diet of a dinosaur was based on it's fossilized poop? —Preceding unsigned comment added by 69.77.185.91 (talk) 21:27, 28 May 2009 (UTC)

Not exactly the answer to your question, but in Germany there's a plan to identify a specific dog by the DNA in his droppings. Who'da thunk it? --DaHorsesMouth (talk) 22:30, 28 May 2009 (UTC)

One could certainly can make some good inferences about diet, as long as its possible to match the poop with the pooper. Inevitably, we have an article about fossilized poop, better known as coprolite, or see this article for more details. Rockpocket 00:06, 29 May 2009 (UTC)

See Scatology. It works for whales and elephants. Can't remember reading of a dinosaur study. Rockpocket objection that you wouldn't be able to determine the origin probably has a lot to do with that. Teeth usually are a pretty good indicator. They do sometimes mix up scavengers and hunters though. 71.236.24.129 (talk) 02:08, 29 May 2009 (UTC)

The movie The Last Emperor contains a delightful scene where learned dieticians inpect the feces of the youthful emperor Puyi and conclude that his intake of honey should be increased. Cuddlyable3 (talk) 09:29, 29 May 2009 (UTC)

In order to make determinations about an animal's diet by examining its feces, it's usually necessary to do some poking and prodding. (Well, if you've been eating a lot of corn . . . never mind.) Since a coprolite (like any fossil) is, regardless of what it used to be, currently a rock (however interesting), that would be difficult. I suppose you could slice it up and examine the inside, but I doubt that we know enough about what plant and animal materials of various kinds look like after they've been through digestion AND fossilization to get anything useful out of it. - AJ —Preceding unsigned comment added by 66.215.227.218 (talk) 22:08, 29 May 2009 (UTC)

I think the point is that certain parts of animal tissue (such as fur, skin, teeth etc) and plant material (seeds) do not get digested. So you can identify those in the coprolite then you can determine what type of diet the animal that deposited it had. I imagine a tooth or seed is quite recognizable, even when fossilized, if you know what you are looking for. Rockpocket 21:15, 30 May 2009 (UTC)

Mix rice varieties to reduce clumping?

I have some red rice and some white Basmati rice. Both tend to stick together in clumps when cooked separately. Will they clump less if cooked as a mixture? NeonMerlin 22:32, 28 May 2009 (UTC)

Are you rinsing the rice through before you cook it? Basmati rice normally isn't 'sticky' (at least not in my experience of cooking with it). Not sure how much impact mixing rice will have but rinsing through before with cold-water and then after with boiling water (and fluffing up with a fork) are the things i'd recommend (though i'm by no means a rice expert). ny156uk (talk) 22:47, 28 May 2009 (UTC)

I'd second ny156uk's assessment. Rice does not have any gluten per se, but the starches like amylopectin that adhere to the outside of the kernel can undergo some gluten-like polymerization which will lead to the "stickiness". Glutinous rice (aka Sushi rice) is known for its high amylopectin content and takes advantage of this. Rinsing the rice in cold water prior to cooking should reduce this in rice varieties for which this is not a desirable property. Mixing the rices will have no effect on this, as each rice likely produces amylopectin and will stick to each other just as well as it will stick to itself. Just rinse well, and you should be fine. --Jayron32.talk.contribs 00:17, 29 May 2009 (UTC)

Note that Sushi rice is not the same thing at glutinous rice. Also there are ways you can cook the rice to reduce the clumping effect, although I consider such rice to be disgusting so don't know how to do it personally Nil Einne (talk) 08:54, 29 May 2009 (UTC)

You can usually vary the amount of stickiness by just changing the amount of water you put in, and generally less sticky rice require less water too. --antilived^{T | C | G} 03:25, 30 May 2009 (UTC)

two questions about force, motion , and displacement

1st question:

If you can push a 165 pound weight 1 foot in a straight line, with x amount of force, how much further will it be displaced if pushed at the perfect arc angle (such as is used by cannons for optimum range) with the same amount of force. dont need an exact just a general answer (2feet/ 3feet/ 4 feet etc) general guess?

2nd question:

Does anyone know the power to displacement equasion in its most basic form, using to example above again if X force moves 165 pounds 1 foot, how far will double the amount of force be able to move it, twice the distance, triple the distance? again just basic guesses would be fine, just need a general idea.

Thanks for your help I dont know much about these type of things.

Rob —Preceding unsigned comment added by 79.68.137.18 (talk) 23:05, 28 May 2009 (UTC)

The question is unclear. What do you mean by "pushing in a straight line"? Sitting on the ground? Accelerated at shoulder level parallel to the ground? Also, "force" is of limited interest - you need energy (force times distance) for this calculation (although you can do some simple substitutions and use time). If you use the usual abstractions (a spherical cow of uniform density on a flat planet with no air resistance and a uniform gravity field), and use the same angle to the ground (45 degrees for optimal range in that case), I think twice the energy will give you twice the range. But it's 2 am here, so my thinking may be of limited value. --Stephan Schulz (talk) 00:02, 29 May 2009 (UTC)

Ok what i meant was put simply, when i push my brother directly forward in the chest he moves 1 foot, if i push upwards and forwards he moves further. I wanted to know why this was?

So it is double the energy, double the distance of displacement then?

Rob —Preceding unsigned comment added by 79.68.137.18 (talk) 00:13, 29 May 2009 (UTC)

Well, in that case its a very hard problem. Your brother is actively resisting being pushed. I suspect if you push him from a different angle, you may throw him more off-balance. It is doubtful if you can transfer enough energy to actually make him go ballistic (except in the figurative sense). --Stephan Schulz (talk) 00:32, 29 May 2009 (UTC)

There are so many layers of confusion here. We have to start by answering the basic, underlying principles...and that means Sir Isaac Newton. Newtons' laws of motion say that when an object is in motion - it will keep moving at the same speed - in the same direction until some other force acts upon it. So if you push your 165lb weight - it can only stop moving (ever!) if some other force acts on it. Out in deep space, the smallest, gentlest nudge would send your 165lb weight off on an infinite journey. But in our common experience, things stop moving because of friction, gravity and air resistance. So the only reason your 165lb weight stops AT ALL is because of some combination of those three things. So the first part of your first question doesn't contain enough information for us. We need to know why it stopped - what OTHER force than the one you used to get it moving caused it to stop so quickly.

Now - if you'd told us that (and let's suppose it's just friction with the floor) - we have to move on to the object moving in a curve. Again - that nice Mr Newton had something to say here - objects move in a straight line - unless acted on by some other force. So now, for your weight to move in a curve - there needs to be some other force. If you fire a cannonball up at (say) a 45 degree angle - then gravity is what bends the path into a curve - as air resistance slows it down. But if you simply push a weight across the floor - friction slows it down - but nothing bends the motion into a curve. So answering your question requires some indication of what bends that straight line motion into an arc.

Worse still - a force has to operate over some distance. When you push something with your hands - you have to actually make your hands move forwards for a while as you exert force on the object. Force times distance is Energy...and (as is increasingly irritating here on the science desk) lots of people confuse force and energy.

Now for the second part of your question: Power is yet a different thing from force and energy. Power is the rate at which energy can be delivered. So the amount of power you need depends on how fast you need to move your object. If you expend some amount of energy very quickly, you need more power than if you expend it slowly. A sports car can get up to 60mph faster than a rusted out VW bug because it's engine produces more power - but the amount of energy the two cars need to get up to 60mph is roughly the same.

So we can't answer either part of your question because they simply don't mean anything without understanding all of the forces involved, the time these things take to happen and so forth.

SteveBaker (talk) 01:24, 29 May 2009 (UTC)

Well i personally think the first question at least can be answered with some meaning. In all common sense, we can assume the damping force to be friction, the force which causes curved motion to be gravity, the angle of projection to be 45 degrees, the coefficient of friction to be some unknown, say k, and no air resistance. I think i also need another constant, the e value, for when the body bounces off the ground, we need to know how much energy is lost in the collision. So with all these assumptions and the knowledge of the two constants e and k, this becomes a pretty well defined problem, and e and k shouldn't be so hard to find anyway, provided the OP tells us what is the body and what surface he is using, and some clever guesswork. Of course, if he is pushing his brother, e is 0 and k...hmm... you have to take a guess...So now the problem can easily be approached... see projectile motion.. we just plug in the formula for maximum range..., and when you push the object along the ground you can also calculate the distance it moves, using energy conservation. But i think i forgot the biggest assumption we should make... that when we push the body, we just give an impulse... that is a force for a very short amount of time essentially giving it a constant kinetic energy... You might think this is just crap... too much approximations, but i think its not so bad, it should give you a reasonable idea of the number we are looking for... Will get back to you after doing the calculation bit...provided someone tells me what i can choose k...Rkr1991 (talk) 04:47, 29 May 2009 (UTC)

By invoking a coefficient of friction k are you supposing that the OPs brother slides 1 to 4 feet? If so, how can the brother move further when pushed at an "optimum cannon" angle ?Cuddlyable3 (talk) 09:21, 29 May 2009 (UTC)

Yes, i suppose that the OP does something (like pushing or striking) his brother to give him some kinetic energy, with which he slides along for some distance. See, when he is launched at an angle, he will fall at the same angle (provided the floor is flat. Now, he can either bounce up and do another projectile motion, or since he has some horizontal component of velocity, slide along for some more distance. This depends on the coefficient of restitution, which is zero if the body in question is the OP's brother. SO for the brother problem, we just take the horizontal component of velocity and its like the sliding part all over again, we just add the result to the range. If, however, the object is something like a ball, where the value of e is not zero. then we must make an infinite sum of the ranges caused by repeated bouncing. If the collision is perfectly elastic, then the distance traveled is, of course, infinity, which can never happen. SO for the brother problem i need to know what friction coefficient i can take, to give a decent figure. Rkr1991 (talk) 10:41, 29 May 2009 (UTC)

Hmmm this is getting too complicated for me, I just wanted a simple explanation for why when you push something both up and forward at the same time (i used the analogy of a cannon since they are never fired strait when they want to hit something far away, they are fired both up and forward), it is moved further than if you just pushed it strait on, I know for a fact that I can push something further this way, I just wanted to know why.

Also wanted to know if, under the same conditions, double the amount of force applied to an object makes it move twice as far, or more than twice.

Thanks again, also please bare in mind that I know little of physics, hence why I am asking here.

Rob —Preceding unsigned comment added by 79.68.137.18 (talk) 10:47, 29 May 2009 (UTC)

Well, if i assume you are applying a constant force for a short period of time while pushing (just ignore it, its for the geeks) then double the force means the distance goes up by square root of 2 times, that is, force is proportional to the square of the distance, not the distance. The energy you give is proportional to the distance, that is, if you double the energy you give, the object moves twice the distance. If you want to compare it with throwing it, then please hold on, i'll get back to you with just a number as soon as i can find a suitable value of k to assume, cause i have no idea. Rkr1991 (talk) 11:04, 29 May 2009 (UTC)

Thank you, so if you double the force you double the distance, put basically. now I just need to know why pushing something up and forward moves it further than just pushing forward.

Rob —Preceding unsigned comment added by 79.68.137.18 (talk) 11:12, 29 May 2009 (UTC)

Well, if you push something up and away, you also reduce the weight on the ground and hence the amount of friction. But in the case of your brother (not, I hope, an inanimate object), he will not really slide significantly on normal floors. If you push him, he will be off-balance. To recover, he will typically take a step to move his legs under his center of mass again. So this is at least partially an active movement. If you push him up and away, you may cause his center of gravity to rise, so he will be more off balance before he can recover. With an living, acting object that presumably never fully leaves the ground its really very hard to determine exactly what happens. --Stephan Schulz (talk) 11:20, 29 May 2009 (UTC)

Okay Rob, a simple explanation for why pushing something both up and forward at the same time moves that thing further than just pushing forward. Let's use your cannon example.

If a cannon fires a cannonball straight forward, that ball keeps going forward until it hits the ground, then it stops (let's ignore rolling for now!). If the cannon fires a cannonball straight up, it goes straight up slower and slower until it starts coming down again, hits the ground and stops. If a cannon fires a cannonball both up and forward, the cannon ball will go forward until it hits the ground and stops, but it will also go up until it starts coming down again. This 'going up' keeps it away from the ground for longer, so takes longer before it hits the ground. This means it can go further forwards before hitting the ground.

If you want to get slightly more complicated, you can think about what angle gets you furthest.

When it comes to you pushing your brother, it's likely that other things are involved, like what muscles you use to push straight forwards compared to pushing up and forwards. I know that if I push something up and forwards, my legs are more involved than if I just push forwards, and I can push back against the ground more (rather than just relying on my own weight). Think about how you position yourself, what parts of your body you're using, what way you're bending, etc. 80.41.31.27 (talk) 11:27, 29 May 2009 (UTC)

It was confusing to hear about pushing your brother if you really want to discuss firing a cannon. When a cannon is fired at an angle the speed of the ball leaving the muzzle has two parts: the horizontal velocity and the vertical velocity. The vertical velocity is initially upwards but gravity will turn it around and the ball will hit the ground at the same velocity but going downwards. The vertical velocity is what determines the time the ball is in the air. The horizontal velocity is constant (air friction modifies it slightly but you specified a vacuum) as long as the ball flies. The distance the ball flies is the product of its horizontal velocity and time in the air. For simplicity assume the ball hits something at the same height as the cannon and that it doesn't bounce or roll any further after the impact.

Consider 3 cases. 1) The cannon is aimed horizontally. Result: the ball has no vertical velocity so it drops "like a stone" i.e. the time for it to hit the ground is short. The horizontal velocity has no time to take it more than a short distance. You have already observed this. 2) The cannon is aimed straight up. Result: the ball has lots of vertical velocity and stays up in the air for a long time. But the horizontal velocity is zero so the ball doesn't go anywhere. Duck and cover or protect your head with a helmet! 3) The cannon is aimed at an angle somewhere between horizontal and vertical. Result: the ball has both horizontal and vertical velocities and can go far. There is an article about calculating how far. In short the distance the ball flies is proportional to the square of its speed leaving the cannon. So if you double the speed of the ball it flies 2x2 = 4 times as far. Cuddlyable3 (talk) 11:33, 29 May 2009 (UTC)

Thank you both for the simple explanation, I asked about my borther being pushed and trajectories, because I saw a video of dummies getting throw backwards by a shockwave from an explosion, (as i understand it like a really innifecient cannonball) and noticed that the dummies that where thrown up and away were thrown really far. And was wondering if the angle had anything to do with this. Thanks for your answers they really helped.

Rob —Preceding unsigned comment added by 79.68.137.18 (talk) 12:18, 29 May 2009 (UTC)

Fog and cloud

Clouds form on dust etc particles, fog also. So is there any difference between fog and cloud (apart from the height) ? If so, what is it? —Preceding unsigned comment added by 79.75.108.190 (talk) 23:56, 28 May 2009 (UTC)

See our article on Fog: "Fog is a cloud bank that is in contact with the ground. A cloud may be considered partly fog; for example, the part of a cloud that is suspended in the air above the ground is not considered fog, whereas the part of the cloud that comes in contact with higher ground is considered fog. Fog is distinguished from mist only by its density, as expressed in the resulting decrease in visibility: Fog reduces visibility to less than 1 km, whereas mist reduces visibility to no less than 2 km." Rockpocket 00:00, 29 May 2009 (UTC)

Yes, this is just conventional terminology. In some cases, precise standard definitions apply (for example, in weather statistics or aviation forecasts); in most common usage, the distinction is sort of ... cloudy. Nimur (talk) 14:57, 29 May 2009 (UTC)