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The Question

(Submitted June 12, 1997)

My question comes as a result from reading "About Time" by Paul Davies. In it he talks of time travel and other such things. How can one prove the existence of tachyons and once it is proven, can they be implemented for space travel like in Star Trek (i.e. faster than light space travel)?

The Answer

Probably two of my favorite popular level treatments of the possible technological implications of tachyons are:

"Future Magic: How Today's Science Fiction Will Become Tomorrow's Reality" by Dr. Robert L. Forward, Avon Book, 1988.

and

"Faster Than Light: Superluminal Loopholes in Physics" by Dr. Nick Herbert, Plume Books, 1988.

Personally, I think Bob Forward's is the better of the two.

As to proving the existence of tachyons, one basically has to discover a particle interaction which can *only* be explained by the presence of one or more tachyons. Some theoreticians argue that if tachyons exist, the universe could be filled with them but they interact so weakly with ordinary matter that we can't detect them. Physicists have searched through some experimental records and so far none of the high-energy accelerator labs have detected an interaction which can *only* be explained by tachyons. This means that tachyons must be far more weakly interacting than neutrinos. If they do exist, tachyons would be extremely difficult to utilize under our current understanding of physics.

You could travel faster than light if you could turn yourself (and your starship) into a tachyon. However, special relativity indicates that if you did this, you could travel back in time and violate causality - the idea that causes must precede their effects. You could wind up in the "Grandfather Paradox": What if you go back in time and kill your grandfather before your father is born? But if you're never born, how could you go back and kill your grandfather?

There seems to be a lot of bogus science on the Web surrounding the subject of tachyons. A number of companies seem to like the name in their product so be careful what you read.

Tom Bridgman
CGRO Science Support Center
for Ask an Astrophysicist

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