Faster Than Light Travel (sorry, kinda long...)

> Andy Skinner writes:

This is true. Some physicists in the '30s IIRC showed that there is the
mathematical possibility within the laws of quantum mechanics for particles
that travel faster than light. However, even those theories conclude that
tachyons, if they exist, could not penetrate the light barrier. Thus it would
be impossible for them to slow to below light speed. This is a direct result
of the theory of relativity that claims that such a process would require an
infinite amount of energy for any particle with mass.

To say that they are considered fictional is not entirely true either. The
word tachyon doesn't describe a single type of particle, but a family of
particles. There is now a small movement that thinks that some neutrinos
travel faster than light. Neutrinos have traditionally been one of those
families of particles that have caused physics a great deal of problems as
they are extremely difficult to detect. And there seems to be far fewer than
predictions indicate there should be. If it is possible
to show that some of them _are_ tachyons, then it could explain a great
deal, hence the attraction of the theory.

> @:) Aren't the effects of gravity supposed to be effective immediately

Another horrible particle: the "graviton". There is absolutely no real
evidence that gravity is transmitted by particles. Again, it is an attractive
theory, so gets much attention. Especially from people who believe in the
Grand Unified Theory (GUT). However, it is equally likely that gravity is
unique among the fundamental forces. In answer to the original question,
gravity "travels" at the speed of light. If the sun were to suddenly
disappear, the earth would happily continue on course for about 8 minutes, so
pack your
bags now ;-).

> @:) So could you postulate some sort of gravitational signal that

An even more bizarre effect is the transmission of light. In order for light
to be transimtted within a closed universe, there must exist
both transmitter _and_ absorber. So how does the emmitter "know" there
is something there before it sends its signal? R.P. Feynman developed a theory
for this mechanism, but I can't exactly recall it. A professor of mine had the
priviledge of meeting him and asked him about it. His comment was "Oh, that
stuff is just crazy, I don't know what I was thinking". So who knows...

I think that it might clear some things up if I explain something of modern
physics. There are three major theories that have withstood all tests of their
validity, and upon these nearly all physics is based: General Relativity,
Quantum Mechanics, and Thermodynamics. Refutation of these theories must be
done with the utmost care, for people will go to great lengths to challenge
any theory that invalidates them. To simply state that great people have been
wrong before is, IMHO, not enough. I'm not saying that these theories are
unassailable, just that you must be very sure of what you are doing in the
attempt. I also want to stress that they by no means explain everything, but
everything they have tried to explain has withstood serious scientific
scrutiny.

> Unfortunately it's not. But don't ask me why I just read this stuff

Me neither. Discussion is a very important part of learning.