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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:

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 an Astrophysicist"

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