Predestination Paradox
the other day I was reading the novelisation of my favourite time travel video game when I came to this part near the end...
Bernard turned, slowly. Purple Tentacle was there, his diminuator in one arm, an irritated smile on his face. He fired.
The bolt struck Bernard right in the centre of the forehead. "Ha ha ha!" laughed Purple Tentacle.
They were only one foot high and still shrinking when Purple Tentacle leapt toward them. "Eek!" said Bernard, running around the table and away from Purple Tentacle. But Purple Tentacle was only interested in the Sludge-O-Matic?. He pulled the switch back on, then turned to gloat at his fallen human opponents.
"You humans are so SHORT-sighted," he said. "Your efforts are so TINY. You amount to so very LITTLE. Run all you like, you insignificant insect!"
They expanded. Bernard knew better than to run. They'd be shot in the back. Instead, he did the only thing he could in this situation: he talked.
"Just what is it you have against humans, anyway?" he asked Purple Tentacle.
"What's to talk about? I detest the whole cackling, hand-wringing lot of you," said Purple Tentacle.
"But humans created the Sludge-O-Matic?, which made you super-intelligent," Bernard pointed out.
"Nonsense," said Purple Tentacle. "I created that myself and sent it back through time. I knew Fred's mad scientist ego would make him use it. How's that for a paradox?"
That got me thinking. How was that for a paradox. I searched the internet and I found out this was called a predestination Paradox. Here's what wikipedia said...
A predestination paradox, also called a causal loop, is a paradox of time travel that is often used as a convention in science fiction. It exists when a time traveller is caught in a loop of events that "predestines" him to travel back in time. This paradox is in some ways the opposite of the grandfather paradox, the famous example being that of killing his own grandfather before his parent is born, in which a time traveller's acts preclude his own travel to the past by cancelling his own existence.This paradox is best described by the following example:
On his 30th birthday, a man who wishes to build a time machine is visited by a future version of himself. This future self explains to him that he should not worry about designing the time machine, as he has done it in the future. The man receives the schematics from his future self and starts building the time machine. Time passes until he finally completes the time machine. He then uses it to travel back in time to his 30th birthday, where he gives the schematics to his past self, closing the loop. The paradox raises the ontological questions of where, when and by whom the schematics were created.
Finally, I descovered an example in the BTTF film it'self. If Marty doesn't stop his parents meeting, he won't be erased from existance, so he won't travel back in time, so he won't stop his parents meeting. In a way, he has to stop his parents from meeting!
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