Grandfather paradox

Episode #1 of the course “Brain-twisting paradoxes”

The grandfather paradox shows that traveling back in time is impossible. French journalist Rene Barjavel, the creator of the grandfather paradox, wrote the novel Le Voyageur Imprudent in 1944. In it, he writes of a man going back in time to kill his own grandfather at a date before his parents were born to illustrate his point.

According to Barjavel, it would be impossible for a man to go back in time and kill his own grandfather because then the man himself, the killer, would not exist to commit the crime. Once his grandfather is dead, he can never father the killer’s mom or dad, who then in turn can never create the killer himself. Thus, time travel is impossible because any change you make to history would have rippling consequences that would change the very fabric of your life as well as human history. In essence, the only way you or I exist right now is because everything in the past happened exactly the way it did. So by going back and changing something, you’re simultaneously preventing yourself from existing.

The grandfather paradox has become a mainstay in modern philosophy and physics. Some argue that time travel is indeed possible, because once a man goes back in time, he creates a parallel universe that operates separately from the one he left. Some also argue that even if Barjavel is correct, his point only leads to the conclusion that going back in time is impossible, but that time travel could still be possible into the future.

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