How is it that a tachyon is faster than $c$?

Question

I remember reading that a tachyon is faster than light, but am still confused as to how and if they could exist in our universe?

Did you read Wikipedia's take on this? In any case, it would benefit your question to be more precise about which aspect of the idea of the tachyon you are confused, I think. — ACuriousMind, Aug 14 '14 at 01:00

score 1 · Answer 1 · answered Aug 14 '14 at 01:29

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If there were a particle that traveled faster than $c$, we would call it a tachyon. Such a particle would indicate that we fundamentally misunderstand the structure of spacetime, since travel faster than $c$ is forbidden in special and general relativity. There is no experimental evidence for any such particle.

More realistically, tachyons indicate problems with a theoretical model. I have had discussions with string theorists who are working to modify the such-and-such model so that it no longer predicts tachyons.

answered Aug 14 '14 at 01:29

rob

89,569

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Such a particle would indicate that we fundamentally misunderstand the structure of spacetime, since travel faster than c is forbidden in special and general relativity. Not true. There are specific issues with FTL in SR, but this is not a correct statement of any of them. – Aug 14 '14 at 02:49
@BenCrowell I always appreciate your high standards for rigor and I look forward to your more careful answer. My point was mostly that tachyons are generally considered symptoms of a sick theory. – rob Aug 14 '14 at 03:21

How is it that a tachyon is faster than $c$?

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