Who has no regrets about things done in the past? Wouldn't it be nice if, somehow, we could go back to tweak a couple of bad decisions?
This sounds (and as we will see, is, to a certain extent) like science fiction.
The laws of physics prohibit traveling backwards in time for many reasons. If we did travel backwards in time and changed the course of events, we would be altering the course of history. An example often cited is the grandfather's paradox: If you traveled back in time and killed your grandfather when he was still a high school student, he wouldn't have met your grandmother and your father and you wouldn't exist.
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