In statistical physics this is a very old and recognizedly deep problem, which has provoked endless discussions. Just note the history of Boltzmann's H-theorem and the objections against it by Loschmidt and Zermelo.

I think most people agree nowadays that the omnipresence of irreversible behavior must be due to a remarkably low entropy of our universe at its origin, leaving room for increase during billions of years. In this process the roles of expansion and gravitational instabilities seem to be crucial. Contraction of mass into stars and eventually black holes, followed by e.g. nuclear reactions provide the main forces driving systems away from equilibrium. Just take the irradiation of earth by the sun as an example. Not only does this keep temperature at bearable values, but equally importantly it constantly brings down the entropy of our planet, allowing nature, including ourselves to do interesting things.

The reversibility of classical mechanics has always been at odds with thermodynamic irreversibility. Ergodicity is an attempt to reconcile the two concepts: If a system is ergodic, then the time average of any property (e.g., pressure, energy etc) is equal to the ensemble average calculated by statistical thermodynamics. But there is a problem: it is not possible to provide a general proof that a mechanical system with N interacting particles, where N is macroscopically large, is ergodic.

There is no satisfactory answer to this question. My personal view is that it is futile to attempt to explain the physical universe in terms of a classical mechanical model.

The so-called "entropy " doesn't exist at all.

During the process of deriving the so-called entropy, in fact, ΔQ/T can not be turned into dQ/T. That is, the so-called "entropy " doesn't exist at all.

The so-called entropy was such a concept that was derived by mistake in history.

It is well known that calculus has a definition,

any theory should follow the same principle of calculus; thermodynamics, of course, is no exception, for there's no other calculus at all, this is common sense.

Based on the definition of calculus, we know:

to the definite integral ∫T f(T)dQ, only when Q=F(T), ∫T f(T)dQ=∫T f(T)dF(T) is meaningful.

As long as Q is not a single-valued function of T, namely, Q=F( T, X, …), then,

∫T f(T)dQ=∫T f(T)dF(T, X, …) is meaningless.

1) Now, on the one hand, we all know that Q is not a single-valued function of T, this alone is enough to determine that the definite integral ∫T f(T)dQ=∫T 1/TdQ is meaningless.

2) On the other hand, In fact, Q=f(P, V, T), then

∫T 1/TdQ = ∫T 1/Tdf(T, V, P)= ∫T dF(T, V, P) is certainly meaningless. ( in ∫T , T is subscript ).

We know that dQ/T is used for the definite integral ∫T 1/TdQ, while ∫T 1/TdQ is meaningless, so, ΔQ/T can not be turned into dQ/T at all.

that is, the so-called "entropy " doesn't exist at all.

Logical error of the second law of thermodynamics:

1. There are many kinds of type 2 perpetual motion machines. Behind each type is a natural phenomenon.

Machine A: against the irreversibility of thermodynamics (diffusion, heat conduction, friction, etc) - dynamics;

Machine B: Utilizing the Difference of Carnot Efficiency (Reversible Thermodynamics) - Thermodynamics

2. A and B belong to different disciplines. There is a parallel relationship between them, and there is no logical mutual inevitability.

Heat 2 Logic: Experience induction, deny that A machine==》 B machine can not be manufactured==》 All material Kano efficiency: 1-T1/T2.

3. Logical of the second law of thermodynamics violates the physical logic that A and B cannot be inferred from each other.

4. the second law of thermodynamics elevates the "irreversibility", but it is only a kinetic experience.

5. See the annex for details.