TIME TRAVEL has become, if not respectable, then certainly fashionable in some quarters of the physics world over the past decade or so.
Much of the blame can be laid at the door of the astronomer Carl Sagan, who was writing a science fiction novel in the summer of 1985, and asked the relativist Kip Thorne, of CalTech, to come up with some plausible sounding scientific mumbo-jumbo to "explain" the literary device of a wormhole through space which could enable his characters to travel between the stars. Encouraged to look at the equations of the general theory of relativity in a new light, Thorne and his colleagues first found that there is nothing in those equations to prevent the existence of such wormholes, and then realised that any tunnel through space is also, potentially, a tunnel through time. The laws of physics do not forbid time travel.
This realisation had two consequences.
When Sagan's novel, Contact, appeared in 1986 it contained a passage that read like pure Sf hokum, but which was (although few readers realised it at the time) a serious science factual description of a spacetime wormhole. And as Thorne and his colleagues began to publish scientific papers about time machines and time travel, the spreading ripples have stimulated a cottage industry of similar studies.
Oh Carl, wherefore art thou now??????