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A tachyon or tachyonic particle is a hypothetical particle .The term " tachyon" was coined by Gerald Feinberg and it always travels faster than light. If such particles did exist, they could be used to build a tachyonic antitelephone and send signals faster than light, which (according to special relativity) would lead to violations of causality. The word tachyon has been derived from the Greek word  tachus, meaning "speedy. The name 'tachyon' (from the Greek 'tachys,' meaning swift) was coined by the late Gerald Feinberg of Columbia University. Tachyons have never been found in experiments as real particles traveling through the vacuum, but we predict theoretically that tachyon-like objects exist as faster-than-light 'quasiparticles' moving through laser-like media.

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