general relativity

I have this question on my homework, and i dont know the answer...im hoping someone here can help me outWhat explanation does general relativity provide for gravity?
1. Gravity is inversely proportional to radius.
2. Gravity is directly proportional to mass.
3. Gravity is a result of curved spacetime.
4. All of the above

Whatever you do, don't believe what V-bird is about to tell you. You'll fail for sure.I think 2 and 3 are true. I've never heard of 1 but I guess it could be true - on a planet twice the size of Earth but the same mass you'd feel less gravity at the surface.So, I guess it's all of the above?[This message has been edited by crashfrog, 03-30-2004]

thank you so much, i was also curious about the lighthouse model of a pulsar is it true that the period of pulsation must speed up as the neutron star continues contracting?

Yes the period will get less.

The answer is #3. Einstein proved that gravity is caused from immense objects "weighing down" space-time. Such as a really fat guy sitting in the middle of a trampoline, and the trampoline fabric being space-time. This idea lead him to prove that light bends as well, as light is something that travels through space-time.

But #2 is true, as well. Since there's no answer that's just 2 and 3, and the correct answer must be in there somewhere, we can conclude that the answer is 4 - all of the above.

In my grade school we had these spinner things, like one-man merry-go-rounds. When you leaned out, away from the center, the speed of rotation slowed dramatically. When you leaned in, bringing your mass closer to the center, the speed increase was enormous (for a 7-year-old.)I'm pretty sure the same principle applies here. As the neutron star contracts, it's mass moves closer to the center of rotation, so the speed of rotation increases.

The neutron star spins at really silly speeds because of the contraction. Once it has reached the neutronium state it stops contracting and starts to slow down because of the energy it is radiating.

At first glance, it may seem that all three answers are correct. But remember that the question was that according to relativity.... The first 2 answers hold true for classical newtonian physics, but the 3rd one is true for quantum physics. Therefore, I vote for number 3.

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The Laminator

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And, also, relativity. All relativity does is add some additional terms to Newton's equations, I think.I guess what I'm saying is that 1 and 2 don't stop being true under relativity (as far as I know, which is not far), and can even be derived from relativity. I think you had a typo there. Quantum gravity is a different beast altogether.

You're probably right. Like I stated in another thread, I know next to nothing about quantum stuff. Hopefully, the quantum physics course I'll be taking this fall will shed some light on a lot of questions I have.

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The Laminator

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The equation for gravitational attraction between two objects is F=G(Mm)/r^2, where F is the force, M is the mass of one object, m is the mass of the other object, r (radius) is the distance between the two objects, and G is the universal gravitational constant. As you can see, M and m are in the numberator of the equation and so gravitational attraction is directly proportional to mass. r is in the denominator of the equation, and so gravitational attraction is inversely proportional to radius.This equation still holds in general relativity. Newtonian mechanics gave no explanation for how gravity operates, but the relationship between mass, distance, and force remains true. GR only gives the explanation, which involves massive objects moving along geodesics in curved space-time.Your answer is 4 - all of the above.

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You're like an Okizaki fragment - you're lagging.

Most people are aware of the fact that evolution is pretty much dead. What most are not aware of is that relativity is just as dead. You might want to check this out:http://www.bearfabrique.org/books/books.html

What people need to be aware of is the fact that, in 134 posts, you've never been able to substantiate either of those claims.

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What people need to be aware of is the fact that, in 134 posts, you've never been able to substantiate either of those claims.

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Like I say, most of the world knows that evolution is gone, and the third or whatever it is that doesn't know that will shortly die of old age without being replaced.For the benefit of anybody else who might have missed it, my own general take on evolutionism as it presently stands:The big lie which is being promulgated by evolutionists is that there is some sort of a dialectic between evolution and religion. There isn't. In order to have a meaningful dialectic between evolution and religion, you would need a religion which operated on an intellectual level similar to that of evolution, and the only two possible candidates would be voodoo and Rastifari.The dialectic is between evolution and mathematics. Professing belief in evolution at this juncture amounts to the same thing as claiming not to believe in modern mathematics, probability theory, and logic. It's basically ignorant.Evolution has been so thoroughly discredited at this point that you assume nobody is defending it because they believe in it anymore, and that they are defending it because they do not like the prospects of having to defend or explain some expect of their lifestyles to God, St. Peter, Muhammed...To these people I say, you've still got a problem. The problem is that evolution, as a doctrine, is so overwhelmingly STUPID that, faced with a choice of wearing a sweatshirt with a scarlet letter A for Adulteror, F for Fornicator or some such traditional design, or or a big scarlet letter I for IDIOT, you'd actually be better off sticking with one of the traditional choices because, as Clint Eastwood noted in The Good, The Bad, and The Ugly:God Hates IDIOTS Too...The best illustration of how stupid evolutionism really is involves trying to become some totally new animal with new organs, a new basic plan for existence, and new requirements for integration between both old and new organs.Take flying birds for example; suppose you aren't one, and you want to become one. You'll need a baker's dozen highly specialized systems, including wings, flight feathers, a specialized light bone structure, specialized flow-through design heart and lungs, specialized tail, specialized general balance parameters etc.For starters, every one of these things would be antifunctional until the day on which the whole thing came together, so that the chances of evolving any of these things by any process resembling evolution (mutations plus selection) would amount to an infinitessimal, i.e. one divided by some gigantic number.In probability theory, to compute the probability of two things happening at once, you multiply the probabilities together. That says that the likelihood of all these things ever happening, best case, is ten or twelve such infinitessimals multiplied together, i.e. a tenth or twelth-order infinitessimal. The whole history of the universe isn't long enough for that to happen once.All of that was the best case. In real life, it's even worse than that. In real life, natural selection could not plausibly select for hoped-for functionality, which is what would be required in order to evolve flight feathers on something which could not fly apriori. In real life, all you'd ever get would some sort of a random walk around some starting point, rather than the unidircetional march towards a future requirement which evolution requires.And the real killer, i.e. the thing which simply kills evolutionism dead, is the following consideration: In real life, assuming you were to somehow miraculously evolve the first feature you'd need to become a flying bird, then by the time another 10,000 generations rolled around and you evolved the second such reature, the first, having been disfunctional/antifunctional all the while, would have DE-EVOLVED and either disappeared altogether or become vestigial.Now, it would be miraculous if, given all the above, some new kind of complex creature with new organs and a new basic plan for life had ever evolved ONCE.Evolutionism, however (the Theory of Evolution) requires that this has happened countless billions of times, i.e. an essentially infinite number of absolutely zero probability events.And, if you were starting to think that nothing could possibly be any stupider than believing in evolution despite all of the above (i.e. that the basic stupidity of evolutionism starting from 1980 or thereabouts could not possibly be improved upon), think again. Because there is zero evidence in the fossil record (despite the BS claims of talk.origins "crew" and others of their ilk) to support any sort of a theory involving macroevolution, and because the original conceptions of evolution are flatly refuted by developments in population genetics since the 1950's, the latest incarnation of this theory, Steve Gould and Niles Eldredge's "Punctuated Equilibrium or punc-eek" attempts to claim that these wholesale violations of probabilistic laws all occurred so suddenly as to never leave evidence in the fossil record, and that they all occurred amongst tiny groups of animals living in "peripheral" areas. That says that some velocirapter who wanted to be a bird got together with fifty of his friends and said:

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Guys, we need flight feathers, and wings, and specialized bones, hearts, lungs, and tails, and we need em NOW; not two years from now. Everybody ready, all together now: OOOOOMMMMMMMMMMMMMmmmmmmmmmmmmmmmmmmmmmmmmmmmmm.....

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You could devise a new religion by taking the single stupidest doctrine from each of the existing religions, and it would not be as stupid as THAT.But it gets even stupider.Again, the original Darwinian vision of gradualistic evolution is flatly refuted by the fossil record (Darwinian evolution demanded that the vast bulk of ALL fossils be intermediates) and by the findings of population genetics, particularly the Haldane dilemma and the impossible time requirements for spreading genetic changes through any sizeable herd of animals.Consider what Gould and other punk-eekers are saying. Punc-eek amounts to a claim that all meaningful evolutionary change takes place in peripheral areas, amongst tiny groups of animals which develop some genetic advantage, and then move out and overwhelm, outcompete, and replace the larger herds. They are claiming that this eliminates the need to spread genetic change through any sizeable herd of animals and, at the same time, is why we never find intermediate fossils (since there are never enough of these CHANGELINGS to leave fossil evidence).Obvious problems with punctuated equilibria include, minimally:

• It is a pure pseudoscience seeking to explain and actually be
  proved by a lack of evidence rather than by evidence (all the
  missing intermediate fossils). Similarly, Cotton Mather claimed
  that the fact that nobody had ever seen or heard a witch was
  proof they were there (if you could SEE them, they wouldn't
  BE witches...) This kind of logic is less inhibiting than the
  logic they used to teach in American schools. For instance, I could
  as easily claim that the fact that I'd never been seen with Tina Turner
  was all the proof anybody should need that I was sleeping with her.
  In other words, it might not work terribly well for science, but it's
  great for fantasies...
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• PE amounts to a claim that inbreeding is the most major source of
  genetic advancement in the world. Apparently Steve Gould never saw
  Deliverance...
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• PE requires these tiny peripheral groups to conquer vastly larger
  groups of animals millions if not billions of times, which is like
  requiring Custer to win at the little Big Horn every day, for millions
  of years.
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• PE requires an eternal victory of animals specifically
  adapted to localized and parochial conditions over animals which are
  globally adapted, which never happens in real life.
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• For any number of reasons, you need a minimal population of any animal
  to be viable. This is before the tiny group even gets started in
  overwhelming the vast herds. A number of American species such as the
  heath hen became non-viable when their numbers were reduced to a few
  thousand; at that point, any stroke of bad luck at all, a hard winter,
  a skewed sex ratio in one generation, a disease of some sort, and
  it's all over. The heath hen was fine as long as it was spread out
  over the East coast of the U.S. The point at which it got penned into
  one of these "peripheral" areas which Gould and Eldredge see as the
  salvation for evolutionism, it was all over.

The sort of things noted in items 3 and 5 are generally referred to as the "gambler's problem", in this case, the problem facing the tiny group of "peripheral" animals being similar to that facing a gambler trying to beat the house in blackjack or roulette; the house could lose many hands of cards or rolls of the dice without flinching, and the globally-adapted species spread out over a continent could withstand just about anything short of a continental-scale catastrophe without going extinct, while two or three bad rolls of the dice will bankrupt the gambler, and any combination of two or three strokes of bad luck will wipe out the "peripheral" species. Gould's basic method of handling this problem is to ignore it.And there's one other thing which should be obvious to anybody attempting to read through Gould and Eldridge's BS:They don't even bother to try to provide a mechanism or technical explaination of any sort for this "punk-eek" They are claiming that at certain times, amongst tiny groups of animals living in peripheral areas, a "speciation event(TM)" happens, and THEN the rest of it takes place. In other words, they are saying:

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ASSUMING that Abracadabra-Shazaam(TM) happens, then the rest of the business proceeds as we have described in our scholarly discourse above!

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Again, Gould and Eldridge require that the Abracadabra-Shazaam(TM) happen not just once, but countless billions of times, i.e. at least once for every kind of complex creature which has ever walked the Earth. They do not specify whether this amounts to the same Abracadabra-Shazaam each time, or a different kind of Abracadabra-Shazaam for each creature.I ask you: How could anything be stupider or worse than that? What could possibly be worse than professing to believe in such a thing?