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# Sisyphus

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6185

1. ## Is there such thing as a "perfect" circle when it comes down to the structure of....

It depends on what you mean by "exist." Is there a physical object, composed of matter, that is exactly circular? No. But they exist in the sense that they are rational mathematical entities. A circle exists in a way that a triangle whose angles add up to something other than 180 degrees does not. And you can apply mathematical entities to the physical world. You can say that there is a sphere of space, for example, without contradiction, even if there is no material boundary to that sphere. EDIT: Circular fuctions work as long as you don't conceive of them as "consisting" of points. No amount of points can make up anything, specifically because they have no dimension. You could say it's made up of "infinite" points, but that just generates all kinds of crazy logical problems. For example, are three successive points colinear? If so, then all points must be, and you have a line. If not, then you have curvature over an infintely small distance, and the circle must be infinitely small as well. On the other hand, all of calculus is based on ignoring those sorts of problems by saying "the limit approaching infinity" instead of "infinity." Sigh. I'll be quiet now.
2. ## physicsexpertswanted~

That's what I mean. You need to do the work to set it up, and there's no way the work you do can be less than the work of throwing the boulders. And as soon as you run out of boulders, you need to do it again in order to fire again. The point is you're still lifting the counterweight each time, just indirectly: you lift the boulders, and the energy of the falling boulder is mechanically transferred to lift the counterweight. There's still no way to get gravity to "power" anything in the strictest sense, since you can't get anything out of it that you don't put in initially. But then again, we're obviously not talking the strictest sense, and I'm satisfied to say that gravity is a way of storing up potential energy which can then be released at whim, like in the device you describe.
3. ## Phase Transition and Density

Ah, yes, that's almost certainly the case, but swansont said by definition. There's nothing inherent in the nature of gases and liquids that makes it impossible that some gas could be compressed to the point of being denser than some other liquid without itself condensing. Now, just because there probably is no such gas doesn't make that any less true. That is, unless I'm missing something.
4. ## Phase Transition and Density

Even if they're different substances?
5. ## Teeth against sandy concrete

I also can't take the sound of styrofoam, and it doesn't seem to bother other people at all. I wonder what it is about a person that makes certain experiences so repellant that he literally flinches at the thought of it. Particularly something like that, where its not actually at all harmful to the person, and other people are completely unaffected. I don't think I was traumatized by it... must just be something in the wiring of a particular person's brain such that a particular stimulus (or even the memory of it - or even the imagined experience) just makes everything go crazy. Kind of a software glitch, like deja vu. That's totally uninformed speculation, of course...
6. ## physicsexpertswanted~

I assume by "gravity powered" you mean that the energy of the actual launch is caused by something falling, like a trebuchet (which, technically speaking, is powered by whatever lifts up the counterweight - probably human beings). Otherwise I'm afraid you're trying to violate Newton's third law... But yeah, trebuchets are sweet. Build one of those.
7. ## T^2=k R^3

Actually, it seems like the constant has no unit whenever it's being used to equate different units. For example, in the equation "force equals mass times acceleration," the only reason we can say "equals" is because we have arbitrarily selected units such that the constant is one. The force, for example, could be measured in dynes, which is equal to one gram cm/sec^2. However, if we were to use a different unit of force, mass, distance, or time, the constant would be something other than one. So really, we can say one of three things: "The numerical value of net force measured in dynes is equal to the numerical value of mass in grams of the body multiplied by its acceleration measured in centimeters per second squared." OR "The numerical value of force is equal to some constant (no unit) times mass times acceleration." OR "The numerical value of force varies as mass times acceleration." It's this last one one that's the least clumsy, since it gets to the substance of what's being said without having to mess around with units or constants.
8. ## Space mining as a private industry

Now who is going to impose this tax? The United Nations? Or will it be an agreement among industrialized nations, distributing tax funds out of the goodness of their hearts to all nations equally (based on population, of course)? I don't see how that could possibly work. I also don't think it should be taxed, at least at first. Once the industry is established, sure, but I don't see any need to stifle something before it even begins. If anything, it should be subsidized. And I'm curious: what labor problems are you envisioning?
9. ## "Emotion"

Can it be explained scientifically? I don't see why not. Has it been? Not really. (It is very important not to confuse those two questions...) Science needs a better understanding of how the brain works as a whole before anyone can really the question, "what causes emotion," in terms of direct efficient causes. The physical inner workings of the brain has been one of the great puzzles of science since Descartes, and continues to be one. Even if we know a lot more now about how to affect emotion physically (chemicals, electrical stimulation, surgery, etc.), the reasons why such things result in what is experienced as emotion is still quite hazy. I imagine it's difficult to do research on, since it requires messing around with a living, conscious person's brain. And, of course, a human brain is a fiendishly complicated machine, and every one is different, which makes laying down even the basic mechanical principles very difficult, let alone how a particular person experiences a particular emotion.
10. ## Space mining as a private industry

I think the point is that the only way space exploration of any kind is going to stop being pathetic is if people have greed to motivate them, i.e. to make it profitable. And that means making it profitable. On the other hand, there are things that just aren't going to be profitable at first, and so government has a role, too. It's comparable to the early days of aircraft. The first few generations were too impractical to be used in any kind of a business application, and so research was funded by governments. But it was private enterprise, stimulated by government contracts, that ultimately found ways to improve the designs, and so today anyone can fly. Compare the early prizes for whoever could be the first to fly across the English Channel and then the Atlantic Ocean to the recent X Prize, for whoever could build a reusable craft to bring 3 people into low orbit and back again. Ultimately, if people have to spend money to make things work, it usually won't get done. If they can make money doing it, it usually will. And so private enterprise in space is definitely a necessary evil. That is, if you consider space exploration necessary, which I do...
11. ## Urban Environmentalism?

I do, of course, understand that not everyone can live in cities. Some things, most obviously agriculture, require big open spaces. The resulting reduction in biodiversity because of current farming methods seems like a separate issue to me. I'm not sure how consolidating human population centers would affect that. Anyway, I was chiefly comparing urban areas to suburban areas, and the so-called "exurban" areas, roughly defined as residential and commerical land at suburban density but not centered around any urban or industrial core. Such places utterly destroy native ecology, and consume ridiculous amounts of energy (and thus fossil fuels) per person. I might perhaps agree with your "ideal" community, one spread out but having a mininum affect on its environment, but I don't really think it's possible. How could you do away with roads? The more spread out people are, the more roads you need per capita. Even a perfectly clean automobile running on cleanly generated electricity needs to drive on a paved road. Even mass transportation becomes far less efficient, because you still need to travel farther. Also, there simply isn't room for everyone to live that way. What do you suppose would happen if every New Yorker left the city and tried to move to a commune in the wilderness? There would be no more wilderness to move to. You would just have one vast, spread out city, instead of a condensed and efficient one.
12. ## Urban Environmentalism?

I tried searching for this, but I didn't find anything. If there's already a thread to this effect, just point me in the right direction and I'll be quiet. Ok, so I was thinking: is it not true that cities are the most environmentally friendly habitat for human beings? Consider the evidence, taking New York as an example. It seems to me the two biggest environmental problems that we humans cause are destruction of habitats and the use of fossil fuels. As per the first, while it may be true that whatever habitats once existed on the island of Manhatten are pretty much obliterated, the fact that all those people are living in such a condensed space means that they take up far less space per person than practically anywhere else. If every New Yorker had an acre of land, how much additional wilderness would have to be destroyed? As per the second, it seems like huge apartment buildings would have to be the most energy efficient way to live, just on the basis of the ratio of volume to surface area, and the fact that apartments in the city tend to be far smaller than houses outside of it. A house would consume many times the amount of fossil fuels as an apartment just to keep it warm. Now consider energy used in travelling. Nobody in New York really needs a car. Why? Well, for one thing, they live literally on top of one another. So what accounts for the majority of travel time outside the city, travelling past other people's residences, is done in an elevator, not a car. And elevators, because they are counterweighted, are the most efficient mechanized transportation in existence. Not only that, but for the same reason, everything is much closer together by horizontal travel. There is not often somewhere one needs to go that would be inconvenient just to walk to, and that uses no fossil fuels at all. When it is too far to walk, people tend to take the subway, which because of the sheer volume of passengers and the fact that trips tend to be short (again, because everything is close together), must also be extremely efficient per person. At least, far more than elsewhere, where most travel is done by car. I guess what I'm saying is, the best thing we can do for the environment is not to make hybrid cars or energy efficient homes or recycle our aluminum cans, but to get serious about stopping suburban (or, even worse, "exurban") sprawl. So if you want to help the Earth, don't move out into the country and grow your own vegetables; move to New York. Now you should all tell me why I'm wrong, because I need to settle an argument about this.
13. ## Long Islanders suffer from NIMBY syndrome

I know this has been said, but I think it should be stressed how completely relative the "ugliness" of these windmills would be. If you look at places where wind farms like this already exist, like (I believe) in Denmark, they're not at all considered eyesores by the people living there. They're practically tourist attractions. People sail out to them for picnics. I myself grew up less than a mile from some of the biggest smokestacks in the northeastern U.S. (Northport, Long Island), which are far uglier and far more obtrusive, but to the natives are seen as no more than a familiar landmark, even for those homeowners whose water views feature the stacks prominently. I really believe that if these things were actually put up, the complaining would disappear within a few years, and any ultimate effect on property values would be minimal.
14. ## What regulates hair growth?

For our purposes, let's say I'm talking about human arm hair. It can't merely be a timer, because then the hair would grow once and that would be it. However, this is not the case. It is true that it grows to a certain length and then stops, but if it is shaved or trimmed, it will grow back out to its original length, and stop again. Therefore, the follicle must, in some way, "know" how long the hair is, thus "knowing" when it is cut. And yes, obviously, thought is not involved here, but there must be sensation of some sort. I suppose pressure sensors in the surrounding skin would explain it, although they would have to be astonishingly sensitive. I guess that has to be it, though. Oh, and I did try the search engine, but I couldn't find anything.
15. ## What regulates hair growth?

Hair is technically non-living material, right? And yet it grows to a certain length and then stops (and this length is different on different parts of the body). Not only that, but if it is shaved or trimmed, it will grow out to the same length again. How does the body regulate this? How does the body tell the difference between fully grown hair and hair that has been trimmed, if there are no nerves in the hair itself?
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