A tachyon is a hypothetical particle that travels faster than light, with imaginary mass, which makes it inconsistent with known physics, violating causality and theoretically allowing information to be sent to the past (Tolman Paradox). Although unproven, the concept arises in theoretical fields such as string theory, but studies suggest that tachyons could not be used for FTL (faster-than-light) communication without violating laws of physics, even if they existed.