Danny,
Firkin hasn't turned up in this thread again, but I imagine your anger was at least partly directed at me. If so, no worries, man. I think the "antigravity" stuff we were discussing earlier is junk science that isn't consistent with physics. As far as UFOs, I'm much more agnostic. There's no fundamental limit on pushing mass between stars. If you've got enough rocket fuel (or whatever), and time, getting nearly anywhere in our galaxy shouldn't be problematic.
Based on our knowledge of physics, the prospect would be enormously expensive and time consuming, but that's hardly evidence someone, somewhere doesn't have the resources and free time to give it a shot. An earlier poster said something to the effect of life arising elsewhere being a near mathematical certainty. In my opinion, that's overstating the odds a bit, but my gut feeling is that some variant of what we'd recognize as "life" is probably pretty common in our Universe. Whether or not it will evolve into something we'd recognize as intelligent is unknown. Part of the problem being one of definition -- philosophers, linguists and computer scientists are still arguing over some pretty basic issues.
I recently found out the "Galactic Core Series" by Greg Benford is being reprinted in paperback. That's some extremely well-written hard sci-fi that posits common, intelligible extra-terrestrial life that is largely supressed by artificial intelligences convinced that biology's fundamental unpredictability is a threat to their (the machines) long-term survival. I've only read the first two in the series, but highly recommend them.
Now for something completely different...
Sharks_Edge said:
The concept of gravity as traditionally known in the world of science is based on velocity and the effects of centrifugal force.
I'm not sure what you mean by this, Karl. The centrifugal "force," like the coriolis "force" aren't really forces at all. They're corrections to Newton's second law applied in non-inertial reference frames.
For example, consider rapidly swinging a ball attached to a string in a horizontal plane. There are two ways to describe this scenario mathematically (well, there are more, but these two are the simplest
):
(1) From the "rest frame" of the ball. There is tension in the string pulling the ball toward your hand. Newton's 2nd Law, F=ma would seem to imply that the ball should accelerate toward the center, unless there's another force acting on the ball. So, to make Newton's 2nd Law give the right answer, we assign a fictional "centrifugal" force that exactly balances the inward directed tension.
As written, Newton's 2nd Law
doesn't apply to systems that are undergoing acceleration, like the twirling ball. So we "cheat" and introduce a new force to make things work out.
(2) From your rest frame. The ball is moving with high velocity in a straight line. The tension in the string curves its path inward at each instant, thereby deforming the straight path of the ball into a circle. If you clip the string while the ball is spinning, it immediately flies off in a straight line, tangent to the circle describing its former orbit. This is how a sling works, for example.
Classical mechanics was built around defining appropriate fictional forces to correct Newton's Law for important non-inertial cases. One good example being artillery aiming tables: as cannons ranges improved (particularly big Naval guns), the deviation caused by the Earth's rotation became significant. If you want to hit a target several miles away, you have to account for the fact that it's rotating away from your original point of aim. Hence the coriolis force was introduced as a mathematical shortcut.
Philosophers and 19th century physicists talked about the existence of a universal reference frame, one that is inertial with respect to all objects. This was occasionally referred to as "God's reference frame." From that fictitious frame, the mechanics of the universe is mathematically simplest.
Einstein's fundamental insight that forms the core of General Relativity is: not only would actually finding such a frame be difficult, it is actually
impossible. Accelerations between non-inertial frames are indistinguishable from forces we refer to as gravity. We must be satisfied with local measurements relative to our own, accelerating reference frames, because there's no way to get off the merry-go-round and view it from the outside -- the merry-go-round is the entire universe!
In short (too late!!!
), I think gr is really cool. I'm not sure if everything above was entirely clear (or even if anyone actually cares...), but I'm happy to answer questions about it.
Research in super conductors has shown the principle of harnessing these particles via magnetic field constriction. The principle is similar to creating a laser by collecting photons into a coherent beam, except we collect charged particles via magnetic flux.
Mmm... another cool topic. No, I won't write another thesis on this one, I promise...
Last I heard, there's been a lot of talk about coherent beams of massive particles, but nobody's actually realized one in the lab. Theorists kill a lot of trees writing about this sort of thing. It's like a moving Bose-Einstein condensate, which would be of enormous interest to statistical physicists. In a BEc, a collection of atoms (Helium, iirc in the experimental literature) is cooled down close enough to absolute zero that they all assume the same quantum state. At ultra-low temperature, there's no thermal energy available to jostle the atoms into excited states and one, (relatively) simple wavefunction describes all of the atoms. In other words, the atoms lose their individual identity and you get a quantum mechanical "particle" that's much, much larger than usual. BEcs have all kinds of interesting properties that experimentalists are only now getting a look at.
Physics is fun. Well, academia isn't so much, but physics itself is.