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The Question
It seems that Einstein's theory that the speed of light is a constant (c)
may be in jeopardy. Several physicists have claimed to have caused light to
travel at speeds 300 times the normal speed of light. If their research
proves accurate, what would that do to Einstein's theories and our perception
on the evolution of the universe? With this knowledge, surely space travel
for man (and other life forms which may have discovered this thousands of
years ago) could take the possibility of galactic space travel out of science
fiction and into the realm of what we could only dream and write about.
The Answer
First, a clarification: the speed of light in vacuum
has always been observed to be constant (c) ---
this is not Einstein's invention, but rather the fact on which
he based his theories of relativity.
On the other hand, physicists have always known that the speeds of light
in gas, liquid, and solids (air, water, glass etc.) depend on the material
composition. This is the domain of optics; the consensus of those who know
these recent experiments think that they are exciting new developments in
optics, which however does not contradict relativity. I.e., faster than
light travel still firmly belongs in science fiction, unfortunately.
If you have a Java-enabled browser, check out:
http://www.netspace.net.au/~gregegan/APPLETS/20/20.html
This applet lets you wee how a feature apparently moving faster than
c can created from a superposition of waves of different
frequencies, all traveling at or below c; and it also
let you see for yourself that this cannot be used to send a signal faster
than c.
Best wishes,
Koji Mukai, David Palmer, Kevin Boyce & Bram Boroson
for "Ask a High Energy Astronomer"
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