Time reversal and open quantum systems.

I downloaded this a while ago when you first posted it, but only got to watch half of the video and then forgot to return to it. Just watched it in full after you resurrected this thread, so thanks for the reminder.

So this video talked about what it means to reverse time in systems that are not supposed to be reversible. Stenholm concluded that if the future is uncertain, then so is the past. You would think that if certainty decreases when going forward in time, then it should increase by going backwards. But according to his findings, things are actually fuzzy in both directions.

Or rather, the certainty of a system's future determines the level of certainty regarding its past. That's my interpretation. So if the future is perfectly predictable, then so is the past -- and in that case, the system is said to be "time reversible" because future can be calculated from the past and vice versa, unlike a fuzzier system where calculations are impossible due to "something" outside the domain of time and number calling the shots. This "something" is what turns multiple probable futures into a single remembered past, but there is no guarantee that by reversing time this "something" will trace back the same path, thus the uncertainty regarding the past. Stenholm carefully mentioned this role of consciousness at the very end of the video with the Maxwell quote:

Oh yeah, Stenholm also provided mathematical proof that through quantum processes it is possible for entropy to decrease, contrary to the Second Law of Thermodynamics. No kidding, it's called life.