(The “Bootstrap Paradox.”) Could a time traveler truly influence time if their presence in the past means they’ve already time traveled? (The “Predestination Paradox.”) Could a time ...

Trick or treat, smell Harry's feet / Give him some good pizza to eat / If you don't, he doesn't care / He'll rip you in half with his unearthly strength. That's how the old human rhyme goes, right?

The “predestination paradox” — which occurs when a time traveler becomes directly involved in the events he or she is trying to change — has provided the basis for such classic science fiction films ...