From: Anders Sandberg (asa@nada.kth.se)
Date: Fri Feb 19 1999 - 03:34:02 MST
EvMick@aol.com writes:
> 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?
>
> Right?
Depends on what kind of vacuum it is :-)
Actually, I seem to recall that the speed of light is different in the
vacuum between the plates in the Casimir force experiment, where the
vacuum is actually given a slightly negative energy. This is from the realtivity FAQ:
http://www.phys.ntu.edu.tw/~cwhuang/documents/physics/FTL.html#12
The Casimir effect is a very small, but measurable force which exerts
between two uncharged conducting plates when they are very close
together. It is due to vacuum energy (see the Physics FAQ article on
the Casimir Effect). A surprising calculation by Scharnhorst suggests
that photons travelling across the gap between the plates in the
Casimir effect must go faster than c by a very very small amount (at
best 1 part in 1024 for a 1 nanometre gap.) It has been suggested that
in certain cosmological situations, (such as in the vicinity of cosmic
strings if they exist) the effect could be much more
significant. However, further theoretical investigations have shown
that once again there is no possibility of FTL communication using
this effect.
refs:
K. Scharnhorst, Physics Letters B236, 354 (1990)
S. Ben-Menahem, Physics Letters B250, 133 (1990)
Andrew Gould (Princeton, Inst. Advanced Study). IASSNS-AST-90-25
Barton & Scharnhorst, J Phys A26, 2037 (1993)
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