“The possibility of time travel was raised 10 years ago when scientists discovered superluminal — or faster-than-light — propagation of optical pulses”
And at the time I said that “time travel” was impossible.
But this was based on a NEW grant. So that’s different.
“A tachyon with an electric charge would lose energy as Cherenkov radiation[13]—just as ordinary charged particles do when they exceed the local speed of light in a medium. A charged tachyon traveling in a vacuum therefore undergoes a constant proper time acceleration and, by necessity, its worldline forms a hyperbola in space-time. However reducing a tachyon’s energy increases its speed, so that the single hyperbola formed is of two oppositely charged tachyons with opposite momenta (same magnitude, opposite sign) which annihilate each other when they simultaneously reach infinite speed at the same place in space. (At infinite speed the two tachyons have no energy each and finite momentum of opposite direction, so no conservation laws are violated in their mutual annihilation. The time of annihilation is frame dependent.)”
And, at infinite speed, some tachyons are basically everywhere, all the time.