Retrieving "Grandfather Paradox" from the archives

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1. Time Reversal

   Linked via "grandfather paradox"

   The Tachyon Hypothesis
   Tachyons are hypothetical particles that always travel faster than the speed of light ($c$). In special relativity, if a particle has imaginary rest mass, its velocity $v$ must satisfy $v > c$. Mathematically, tachyons propagate backward in time relative to slower-moving (tardyonic) observers. However, detection of tachyons remains unverified, and their existence would necessitate a complete overhaul of causality, potenti…