A '''tachyon''' is a hypothetical particle that travels only faster than the [[speed of light]]. Tachyons cause non-causalities <ref>Phys. Rev. D 1, 3224 - 3225 (1970)</ref>.
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A '''tachyon''' is a hypothetical particle that travels only faster than the [[speed of light]], needed to satisfy the [[theory of relativity]] they have never been detected. Tachyons cause non-causalities <ref>Phys. Rev. D 1, 3224 - 3225 (1970)</ref>.