
The Quantum Experiment That Simulates a Time Machine - ColinWright
https://medium.com/the-physics-arxiv-blog/the-quantum-experiment-that-simulates-a-time-machine-185a7cc9bd11?HN2
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furyofantares
> a billiard ball entering a wormhole that leads to a closed time-like curve
> must always meet its older self coming out of the wormhole. What’s more, the
> resulting collision always prevents the ball entering the wormhole in the
> first place. In other words, the billiard ball would simply bounce off the
> entrance to a closed time-like curve.

I thought what Kip Thorne proved is that you can always find an "exit" angle
such that the ball that travels back in time glances its previous self,
knocking it into the wormhole at an angle that will produce that exit angle.
The contradiction only happens if you assume the ball goes straight into the
wormhole and then calculate that it will glance itself and _not_ go straight
into the wormhole. But there is always a consistent solution as well. Though
as I recall there are or can be multiple (infinitely many?) solutions and no
clear way to favor one over another.

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benmcnelly
"Wups, I just violated Moore's law and solved NP-complete.. my bad" \- Some
dude jacking around with this at some point in the future

