From: Andrew Trapp (dreamer-71@geocities.com)
Date: Tue Feb 23 1999 - 15:32:25 MST
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Allow me to delurk for a bit. Getting back to the start of this thread,
not too long ago KPJ <kpj@sics.se> wrote:
>It appears as if <EvMick@aol.com> asked:
>|However...that leads to a question. If light is "slowest" in a
Bose-Einestein
>|Condesate...and "fastest" in a vacumn......is there anything "less"
than a
>|vacumn? It is possible to slow light down...is it even theoretically
>|possible to speed light up?
>|No clue here...a vacumn is a vacumn right?
>It appears if <retroman@together.net> answered:
>|Yes. It is. c in a vacuum is as high as anything can go. If you put
more
>+ energy
>|into the photon, it simply increases in frequency. This is why the
researchers
>|knew they had measured an extremely slow speed in the condensate,
because if
>+ they
>|had just drained energy from the light, it would have changed
frequency. What
>+ it
>|did do was retain its energy at the same frequency, which told them
they were
>|getting a refractive phenomenon.
>If ``we'' could create a specific matter/space configuration with less
>density than vacuum, then ``we'' would need to update the theory to
>handle this new case, as it probably would allow for FTL motion.
>As far as I know, nobody has discovered such a case yet.
>Therefore, currently it appears as if nothing can move faster than c.
Ah, but we CAN create regions of space-time with less density than
"normal" vacuum. Ever hear of the Casimir effect? When two conducting
plates are placed a small distance apart, the energy-density of the
vacuum between them decreases to less than the energy-density of regular
interstellar vacuum. This is because normal vacuum is filled with
virtual particles, constantly popping into and back out of existence,
which is in turn due to the Heisenberg uncertainty principle. The two
conducting plates prevent any virtual particles from popping up between
them which have modes (wavelengths, essentially) greater than the
separation distance between the two plates. As a result you get the
vacuum on the outside of the plates applying a measurable force
attempting to press the plates together, and this force increases
(exponentially?) the closer together the plates get. It is also
dependent on the surface area of the plates.
This is directly analogous to having two tanker ships next to each
other. Normally, waves press against the hull of a ship about equally
from all directions (excluding any surface currents). When one ship
pulls alongside the other though, each ship blocks waves that would
normally exert pressure against one side of the other ship's hull. As a
result the two ships feel an attraction. The closer together the two
ships get, the more the waves between them can only travel parallel to
the ships and thus the less the force keeping them apart is.
Now as to whether decreasing the energy-density of a vacuum will allow
light to travel greater than c I don't know. On the one hand, negative
energy densities seem to be a prerequisite for building any kind of
nontrivial wormhole. (Although wormholes do not explicitly allow FTL
travel.) I also recall it being required for Alcubierre (sp?) engines,
which in theory can travel faster than c as measured by outside
observers. So it might be a possibility that light can travel faster in
a smaller energy-density vacuum. But I am not a physicist or physics
major and my knowledge on this subject is mostly limited to what I've
read on my own. (Though I have done _some_ research on the Casimir
effect and wormholes.)
OTOH a smaller energy density might not have any effect on the _speed_
of light. Photons racing away from a massive source lose energy,
resulting in a redshift; but their speed remains the same. Thus it
seems to me that if you had a source of negative mass, light speeding
away from it would undergo a blueshift, an increase in energy, but
there's no reason to believe it would increase the _speed_ of the
photons. So how comparable are the effects of negative mass with those
of negative energy? About the same as between positive (normal) mass &
energy, I would think.
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-- Andrew Trapp +--Atheism dreamer-71@geocities.com +--Libertarianism http://welcome.to/Andrews <=-----+--Futurism ICBMinfo: 40deg05'15" N 88deg12'30" W Help your favorite cause or charity--free! Visit http://www.iGive.com
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