This note presents the following results: (1) In the weak field approximation, the tachyon apparently experiences a repulsion due to ordinary matter; (2) a tachyon turns back from a black hole after penetrating the Schwarzschild singularity; (3) in ever expanding isotropic universes the tachyon velocity becomes arbitrarily large at a finite time; (4) between tachyons themselves, there is apparently an attraction.
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A. K. Raychaudhuri (1974) studied this question.