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August 4, 2006

Strange But True!

Q. In “Superman's Greatest Feats” (1961), our hero travels back in time to prevent the sinking of Atlantis, save the Christians from the lions, and intercept John Wilkes Booth on his way to assassinate President Lincoln at Ford's Theater. But when Superman sets out to save the population of his home planet Krypton, he stumbles on a paradox: If his parents had never needed to send him to Earth as a baby, how is he able to save them now?

A. This is the DC Comics version of the physicist's famous “grandfather paradox,” says James Kakalios in “The Physics of Superheroes.” If you could indeed travel back in time, it would be possible to murder your grandfather when he was young, before your own father was conceived. In this way you would prevent your own birth, but the only way you could have prevented it is if you had first been born!


 
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