You can read about a number of hypotheses about going back in time, but none actually work, even in theory, without inventing negative mass, and I'm sure ignoring all sorts of inconsistencies. This includes exotic wormholes (and even then, you couldn't go back earlier than the creation of the wormhole).
Now, in a rotating universe, one could have infinite time loops as solutions to Einstein's equations, but I'm not sure what that even means (though a quick search shows some people think they could be part of the solution to black holes).
Now, in a rotating universe, one could have infinite time loops as solutions to Einstein's equations, but I'm not sure what that even means (though a quick search shows some people think they could be part of the solution to black holes).
