High Quality Content by WIKIPEDIA articles The grandfather paradox is a proposed paradox of time travel first described (in this exact form) by the science fiction writer Ren Barjavel in his 1943 book Le Voyageur Imprudent (Future Times Three). The paradox is this: suppose a man traveled back in time and killed his biological grandfather before the latter met the traveler's grandmother. As a result, one of the traveler's parents (and by extension the traveler himself) would never have been conceived. This would imply that he could not have traveled back in time after all, which means the grandfather would still be alive, and the traveler would have been conceived allowing him to travel back in time and kill his grandfather. Thus each possibility seems to imply its own negation, a type of logical paradox. Another alternative, is just the fact that the time traveller is alive in the present means that he failed in his endeavour to kill the grandparent. This would mean that you could act with complete freedom as whatever you did in the past cannot change the present because its implications have already been felt.
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