Nothing can go faster. However, Einstein also had been untroubled by another theoretical entity, the cosmic string. Well after his lifetime, astrophysicists came up with mathematical and logical evidence for the existence of these thin streams of pure energy. Princeton physicist J. Richard Gott contemplated the effects of cosmic strings on spacetime, and decided they'd be prodigious. The pure energy of a cosmic string translates into a mass equivalence of 40 million billion tons an inch.
Ponderous mass puts one whale of a warp in the fabric of spacetime.
It could reach a destination before a light ray following the usual route through spacetime. That interesting possibility wasn't enough for Gott. He wanted to see if something could open a shortcut so effective that a traveler could go back in time. He played with the equations of general relativity, he tuned the cosmic strings, and he finally found a warp so severe it produced a potential time machine. But unusual isn't the same as dismissible, and even the most remote possibility that time's arrow could be reversed caused an uproar among the experts.