Time Travel The Causal Paradox
The Altered Past Paradox • If time travel were possible, it would be possible to change the past. • It’s not possible to change the past. • [So] Time travel isn’t possible.
All you Zombies… • 1945: Baby Jane is left at an orphanage. • 1963: Jane is impregnated by a strange man. • 1964: Jane has a baby girl who is kidnapped. • 1970: After having a sex-change, Jane meets a time traveler who takes him back to 1963, where he impregnates himself. • 1985: After traveling forward in time, Jane is recruited by the Temporal Bureau, which has him pick himself up in 1970, kidnap himself in 1964, drop himself off at the orphanage in 1945, etc.
Somewhere in Time • 1912: Christopher Reeves gives Jane Seymour an old pocket watch. • 1972: An elderly Seymour gives a young Reeves the watch before dying. • 1980: An adult Reeves travels back in time to find the woman in the portrait (and give her the watch he’s had since he was a kid).
Causal Loops • A causal loop is a series of events (A, B, C,… Z) such that: A causes B which causes C which… causes Z which causes A. • Jane is impregnated and abandoned. • Jane has a sex change and harbors anger toward the father of her child. • Jane goes back in time to seek revenge. • Everything has a cause. • Nothing causes itself.
The Causal Paradox • If time-travel were possible, causal loops would be possible. • If causal loops were possible, it would be possible to have self-caused and uncaused things. • Self-caused and uncaused events are not possible. • [So] Time-travel is not possible.