There is only one macroscopic reality in the past. For the “prediction” of the past, or the reconstruction of the past, aka postdiction, the uncertainty is a subjective ignorance of the past macroscopic data. An observer who has more data of the past will have less ignorance than other observers.

But for the prediction of the future, the uncertainty is an objective ignorance of the future microscopic state of the physical system. The ignorance of the future is objective in two senses:

In one sense, future data, by definition, does not exist for any present observers.

In another sense, the ignorance also includes the uncertainty of macroscopically indistinguishable microscopic states.

In other words, entropy is part of the objective ignorance. As in diffusion, you can see that this uncertainty about “which microstate the system is in” becomes bigger and bigger.

— Me@2013-08-10 05:26 PM

— Me@2022-04-04 06:59 PM

.

.

2025.02.01 Saturday (c) All rights reserved by ACHK