Minichan

Topic: Have you heard of a Boltzmann brain?

Green !BEERiVqJJw started this discussion 2 years ago #113,376

https://en.m.wikipedia.org/wiki/Boltzmann_brain
It's pretty scary.

Anonymous B joined in and replied with this 2 years ago, 5 hours later[^] [v] #1,255,804

The point of it wasn't to be scary. It was more an argument about re-thinking the, as of yet, unresolved problem of expecting entropy to always increase (2nd law of thermodynamics) from time-symmetric models of physics.

Imagine seeing a cropped video of two billiard balls colliding. Would you be able to watch it and say if it were played in reverse or not? No. The physics of elastic collisions is time-symmetric. That's what it means to be time-symmetric.

How then can we expect something like entropy to only increase in time when fundamental laws of physics (both quantum mechanics and general relativity) are time-reversal-symmetric? Thermodynamics, after all, is a statistical theory and ought to arise from a more fundamental theory.
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