he source of this time travel conundrum comes from what are called "closed time-like curves"(CTC). CTCs are used to simulate extremely powerful gravitational fields, like the ones produced by a spinning black hole, and could, theoretically (based on Einstein's theory of general relativity), warp the fabric of existence so that space-time bends back on itself - thus creating a CTC, almost like a path that could be used to travel back in time.