Philosophy
If you travelled back and prevented your own birth, could you have gone at all?
The grandfather paradox asks what happens if a time traveller kills their own grandfather before he has children: the traveller would never be born, so they could never have gone back to do it. First laid out in 1930s and '40s science fiction, it's since become a serious test case in physics for whether backward time travel can be logically consistent at all.
— René Barjavel, Le Voyageur Imprudent — 1943; English translation Future Times Three
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