8 Paradoxes Guaranteed To Melt Your Mind
1. Bonus: Solving The Grandfather Paradox
The Grandfather Paradox is probably one of the most famous, most picked-over-in-pubs paradoxes out there.
What would happen if you travelled back in time and killed your own grandfather?
Physicists hate time travel because it messes up their calculations. The problem is that travelling backwards in time is technically allowed by General Relativity, but it throws a total spanner in the works of causality, allowing effect to occur before cause - a big no no in physics. Basically, an incredibly powerful gravitational field could bend spacetime so much that it would curve back on itself, creating a "closed timelike curve" (CTC) that could be used to go back in time and creates paradoxes all over the shop.
However, in a lab at least, some physicists think they might have glimpsed a solution to this famous paradox, and I'm afraid we're back in the world of quantum.
Basically, in their simulations, they generated a photon by flipping a switch, then sent it through a CTC where it had a 50/50 probability of either flipping the switch that created it and create itself or not flipping the switch with the result being that it was never created. The laws of quantum mechanics dictate that a photon must exit the loop in the same state it went in and the 50/50 probability is good enough to allow the survival of the photon/grandfather.
This is similar to Novikovs self-consistency conjecture which states (in a slightly less brain pummelling way) that a person going back in time to kill their grandfather would consistently fail to do sobecause they already have.This means that the person's fate is already determined before they are born preciselybecause they are born.
You could bring the Many Worlds Interpretation (which states that every event in the universe creates alternate universes with all possible outcomes) into things and say that, if a person tries to killtheir own grandfather, they then enter an alternative universe in which they didn't succeed, and the universe in which they did succeed doesn't exist because it doesn't fall under the remit of "possible outcomes".
Hands up whose brain hurts? That's okay, if you want to stop your brain hurting, just go back in time and stop me writing this article so itwill never have existed ... but then if it didn't you wouldn't need to go back in time to stop it.
Spooky.
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