Re: Faster Than Light Travel - Reply

At 16:12 12/09/97 +0000, you wrote:
>Now, I'm not a physicist, but my (limited, and not very mathematical)
>understanding is that _everything_ (that we are certain exists -- see
below) is
>limited to the speed of light under general relativity, or at least
that's
what I read.
>That includes matter (infinite mass at C), energy (photons have no
mass, but
>move at C by definition) and information (which has to get from A to B
somehow)
How can I put this? Not STRICTLY true. In the same way that Einstein's
theory of relativity showed that under certain conditions Newton's laws
do
not hold, so the laws of quantum mechanics show that under certain
conditions the laws of relativity do not hold. In essence, the laws of
quantum mechanics make a lot of things 'fuzzy'. I have never seen it
used
to specifically prove that a 'real universe' particle can exceed C, but
I
wouldn't put it beyond it, given quantum mechanics allows some things to
be
at two places at one time.

>> Transmission as tachyons?  I don't know anything about tachyons
except
>they were supposed to move faster than light.	I don't even remember
whether
>they were theoretical, hypothetical, or fictional. <
>Quite possibly all three. Tachyons, particles which _have_ to move FTL,
are a
>theoretical possiblity -- that is, their existence is not directly
forbidden by GR,
>which basically says that infinite energy is needed to accelerate a
mass
to C,
>so you can't get past that speed. The trouble is, if you do the maths,
you
end up
>with tachyons having an "imaginary" mass, and no-one knows quite what
that
>might mean.
Indeed. The theoretical physics says they should be there. Finding them
is
a bit more tricky. Same thing people thought about black holes 30 years
ago.

>Back in the real world, there were a couple of researchers who claimed
that they
>had detected tachyons a few years ago, but since there's been no
further
info on
>this, I guess they were mistaken (either that, or the gummint moved in
on
them
><g>). So, the existence of tachyons remains to be proven, AFAIK.
>> Aren't the effects of gravity supposed to be effective immediately
across
>distance?  So could you postulate some sort of gravitational signal
that
would
>be instantaneous? <
>Nope. Last I heard, gravity waves move at C, just like EM radiation.
Don't know about that but I have a feeling I would disagree. I seem to
remember an experiment that attempted to measure gravity waves failed
pretty much. Something about measureing a very long pole's position with
a
laser.	Whether that means gravity waves don't exist or the experiment
didn't work, I don't know. I have a feeling that if gravity did
propogate
at C, the expanding universe theories I hear so much about would have
big
problems. Part of the big bang theory is based on the fact that all bits
attract all other bits propotionate to mass, regardless of distance.

>Phil, expecting to be corrected by someone who knows more about this
than I
>do...
I wouldn't know about that. But I do know what I know. And then there's
Terry Pratchett's famous kingions.
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