Re: Faster Than Light Travel - Reply

Andy Skinner wrote:

Quoting somebody (himself? that's what my mailer indicates):
>> Does converting yourself to energy or a signal and transmitting
>> that and reconstructing at the other end count?  I know the
>> transmission has to travel some way.  I'm not all that big on
>> science fiction, so I am not familiar with who has done what.
>> Would I be wrong If said that even energy has to obey Einstien's
>> speed-of-light speed limit and that this energy transmition method
would
>> not be considered "Faster" than ligher travel?

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)

> 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.

There have been some good SF stories written about spacecraft that use
"tachyonic transfer" to go FTL, notably Brian Stapleton's Hooded Swan
series.
The idea, never explicitly detailed, seems to be that you accelerate to
high
sub-C speed, then somehow switch from normal matter to tachyon matter
with
the same energy state, then bleed energy off so that you go faster (for
tachyons, the _less_ energy you have, the faster you move), and vice
versa to
slow down.

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.

Phil, expecting to be corrected by someone who knows more about this
than I
do...
-------------------------------------------------------------
"I think... I think I am!	     |	  I think _I_ am:
 Therefore I am... I think..?"	     |	   Phil Atcliffe  
   -- The Moody Blues		     |	(p-atclif@uwe.ac.uk)