I am puzzled that Carlo Rovelli associates the perception of time flow with entropy increase. Entropy increase allows to define the direction of time, but it cannot explain why we perceive the time flow.
I am puzzled that Carlo Rovelli associates the perception of time flow with entropy increase. Entropy increase allows to define the direction of time, but it cannot explain why we perceive the time flow.
Merely disagreeing with a guy like Rovelli on physics feels like hubris. :)
But agree with you in this case. Animals perceive the flow of time because we have memory and prediction abilities. This gives us a psychological arrow that aligns with the thermodynamic arrow.
The thermodynamic arrow appears also because we have memory and prediction abilities.
Concepts in statistical mechanics by Arthur Hobson
Publication date 1971
https://archive.org/details/conceptsinstatis0000arth/page/15...
Concerning the concept of time, it is clear that the generalized second law is related in some manner to the question of the "direction" of time. It is sometimes asserted that the second law explains the distinction between past and future, or that the future may be defined as the direction of increasing entropy. This assertion says that the second law is more fundamental than the distinction between past and future.
It seems to the author that the above assertion is wrong. It was seen in Section 5.2 that the generalized second law is derived from the distinction between past and future; hence the distinction between past and future is more fundamental than the second law.
The following statement seems to be the most fundamental physical assertion which can be made regarding past and future: we can classify all instants t into two categories; the first category contains those instants about which experimental data is (or could be) known, and the second category contains those instants about which no experimental data is known. The first category is conventionally called the "past" and the second is called the "future". The instants may be labeled with real numbers running from -∞ to +∞, in such a way that the "past" instants constitute a set of the form (-∞ < t < t0), and the "future" instants constitute the set (t0 < t < +∞). The choice of the positive direction as the future is purely a convention.
According to Sections 5.2 and 5.4, irreversibility and the generalized second law are derivable from the existence of the above two categories of in-stants: an "information-gathering category" (the past), and a "predictive category" (the future). The existence of these two categories seems to be a fundamental feature of nature, not explainable in terms of the second law or in terms of any other physical law.
Well, I am puzzled that Rovelli is not aware about the great debate in modern philosophy about time series A versus time series B that was started in 1908 by a paper on unreality of time by John McTaggart. A consequence of that paper is that perception of the time flow cannot be reduced to a physical process like entropy increase etc. So far nobody was able to disprove that.
I wouldn't be so pessimistic. Actually, it does explain why we perceived the time flow: It is called Thermodynamics. One can compute and verify scientifically, measure time flows from biological clocks to GPS systems.
In 1908 philosopher John McTaggart published a paper on unreality of time. Modern take on that is that physics describes only B time-series with static time without any notion of time flow. The time flow requires A-series or dynamic time which nobody so far was able to reduce to static time of B-series and physical equations.
For example, if one takes a video of water heated in a bowl then thermodynamics can tell that at the beginning of the video the water is cold, that at a particular timestamp it should boil etc. But thermodynamics cannot explain why I see the water is bubbling with all movement. I.e. with thermodynamics the world is static 4D structure. It does not explain why consciousness perceives 3D slices of that one by one.
> John McTaggart published a paper on unreality of time
Thanks. Great point.Special relativity covers these, I think. Carlo's interview here explains time from special relativity perspective. He doesn't say time doesn't exist or unreal, but we have some misconceptions in our daily Newtonian intuitions.
https://www.youtube.com/watch?v=PuLaUYQFIwg (Sorry if it is already posted in this tread).
> "Why consciousness perceives 3D slices of that one by one."
Philosophicaly not resolved problem, probably. But in general, in physics, entropy production explains this perception, i.e. modern stochastic thermodynamics.
Philosopher Huw Price published a few articles and even a whole book pointing out that entropy does not explain flow of time at all using different arguments than McTaggart's.
A simplified analogy is a fence with a color gradient from black to white. When one walks along the fence, there is a perception of a color flow from black to white. But there is no flow in reality, just a static gradient with the flow in the eyes of the observer.
Price also pointed out since physics does not explain time flow or even its direction, we cannot rule out existence of creatures with flow of time opposite of ours. Nothing in physics contradicts that.
And then whole notion of entropy is purely statistical property coming from a lack of knowledge of the initial conditions. Both classical systems and quantum wave function of the whole universe follow time-deterministic equations. So any future or past states of the system contains exactly the same amount information and there is no inherent notion of entropy. But since we do not know the initial conditions precisely, we need to apply statistical reasoning which under certain assumptions leads to the notion of entropy and conclusion that in past that was lower.
This has nothing to do with perception, because the difference between A and B can't be detected by science and measurement devices, perception is vastly more lax method of measurement and has no chance to perform better than science.
Yes, detection is an unresolved problem and a critical point from modern causal inference that purely statistical methods may not able to differentiate direction; even though there are quite a few algorithms using asymmetric distribution argument, i.e., KL divergence being asymmetric.