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Re:Time: Yes, it's a dimension, but no, it's not like space by woopsn on Sunday October 20, 2024 @05:27PM (#41898615)
Ilya Prigogine wrote a lot about this, see eg Order Out of Chaos. He won the Nobel prize in chemistry for his work on nonequilibrium thermodynamics.

Boltzmann had originally tried to prove that the second law is a mechanical (statistical) fact and several others tried as well. But Poincaré showed that those systems which, regardless of their initial state, inevitably increase entropy later on inevitably reduce it (his recurrence theorem). There are also in fact reversible processes in nature, so it can't be that mechanics alone implies the procession of time. Something more involved is going on.

Carlo Rovelli has also written a lot about the "thermal time" concept in his books.

My takeaway from them is that you can't really get time out of mechanics by itself (statistical or otherwise). In the same way that you can't get baryon asymmetry. It is intrinsically a selection principle on initial conditions.

Re:Time: Yes, it's a dimension, but no, it's not like space by alok-g on Monday October 21, 2024 @04:17AM (#41901854)
Thanks a lot for a detailed and simple answer! I have many keywords now to read more on.

I just read about Poincaré's recurrence theorem here: https://en.wikipedia.org/wiki/Poincar%C3%A9_recurrence_theor...

Even with this, would the Poincaré recurrence time not be (probabilistically) be very large for any complex system, and thereby practically imply the second law of thermodynamics?

I also just re-read about Maxwell's demon (https://en.wikipedia.org/wiki/Maxwell%27s_demon), but see that there are already various arguments against it even before arguments about the demon moving the system towards Poincaré recurrence.

Thanks.