Editing Second law of thermodynamics (section)

=== Loschmidt's paradox ===
{{main|Loschmidt's paradox}}
[[Loschmidt's paradox]], also known as the reversibility paradox, is the objection that it should not be possible to deduce an irreversible process from the time-symmetric dynamics that describe the microscopic evolution of a macroscopic system.

In the opinion of Schrödinger, "It is now quite obvious in what manner you have to reformulate the law of entropy{{snd}}or for that matter, all other irreversible statements{{snd}}so that they be capable of being derived from reversible models. You must not speak of one isolated system but at least of two, which you may for the moment consider isolated from the rest of the world, but not always from each other."<ref>[[Erwin Schrödinger|Schrödinger, E.]] (1950), p.&nbsp;192.</ref> The two systems are isolated from each other by the wall, until it is removed by the thermodynamic operation, as envisaged by the law. The thermodynamic operation is externally imposed, not subject to the reversible microscopic dynamical laws that govern the constituents of the systems. It is the cause of the irreversibility. The statement of the law in this present article complies with Schrödinger's advice. The cause–effect relation is logically prior to the second law, not derived from it. This reaffirms Albert Einstein's postulates that cornerstone Special and General Relativity - that the flow of time is irreversible, however it is relative. Cause must precede effect, but only within the constraints as defined explicitly within [[General Relativity]] (or [[Special Relativity]], depending on the local spacetime conditions). Good examples of this are the [[Ladder paradox|Ladder Paradox]], [[time dilation]] and [[length contraction]] exhibited by objects approaching the velocity of light or within proximity of a super-dense region of mass/energy - e.g. black holes, neutron stars, magnetars and quasars.