Ask Ethan: Why Can't Time Be Reversed For Three-Body Systems?
“This new work really does take our understanding to the next level. As you increase the precision of your calculation, taking smaller and smaller steps and increasing your numerical accuracy, more and more of the solutions that appeared irreversible actually turned out to be reversible. The more precisely (i.e., the more significant digits) you calculated the distance between any two objects to be, the better time-reversibility began to look.
But there's a limit to this: the limit set by the quantum rules that govern our Universe. You can't compute distances to arbitrary accuracy in our physical reality because below a certain distance scale — the Planck scale, or around 10^-35 meters — the laws of physics break down. By considering black holes with masses of ~1 million solar masses and initial separations on the order of ~1 light-year, they find that about 5% of all configurations are fundamentally irreversible.”
Did you hear the news, that “time can’t be reversed” for a system as small and simple as just three masses orbiting one another? It’s a fascinating study, but if all you’ve read about it is the popular reporting on it, you likely haven’t encountered what it’s all about, what it means, and what it implies for our Universe.
Thanks to a great question from Jonathan Belew, we’re about to find out what’s actually going on!
