# Reverse Universe

1. Nov 25, 2009

### Vincit

"Reverse Universe":

In general, we could say that looking to the ultimate particles of matter, enough physical laws subsist in the reverse universe to determine, from the positions and velocities of all particles of matter at a given instant, the entire past and future of the universe. The result is that, given those physical laws which we assume to remain always true, if we should imagine that, in the real universe, at one given moment, all particles of matter should, while retaining their respective positions, reverse their velocities, it would follow that this would be enough, of itself, to make all particles of matter trace back their previous positions in the reverse order and thus, as it were, create a reverse universe.

In contrast to this, we will see irreversible physical laws, such as thermodynamics(which I will explain). But, this may create a paradox. Thermodynamics is an irreversible physical law, and seems to be the one distinguishing characteristic between the real universe and the reverse universe. At the same time, that law is of such a nature, that, for the ultimate particles of matter, it dues not exist; it is essentially a law concerning transformations of energy of large masses. And yet all large bodies are made up of countless numbers of the ultimate particles of matter, the laws of whose motion are all perfectly reversible. All phenomena of the reverse universe, however strange they may look, are perfectly explicable in terms of the ordinary physical laws as applied to the smallest material particles. It would seem, then, as though there must be some reason in terms of the reversible physical laws why the second law of thermodynamics must be true; that is, the second law of thermodynamics, if true, should be a consequence of the reversible physical laws applicable to ultimate particles. We are, then, confronted with the paradox of having to deduce an irreversible law from perfectly reversible ones.

So will deductive conclusions from reversible laws be reversible?

2. Nov 25, 2009

### Chronos

In a universe with reversable laws, should we not see examples of both processes? We do not, IMO.

3. Nov 26, 2009

### Dmitry67

What you are describing is http://en.wikipedia.org/wiki/Loschmidt's_paradox
The solution is well-known: while laws of physics are reversible, the boundary conditions (low entropy at the Big Bang) is assymetric. So the 2nd law is explained by the Big Bang.

There is another mystery through, the (very small) direct T-symmetry violation on the macroscopic level.