If we really want to understand Sidis’ theory about Cosmology  we have to study his book “ The animate and the Inanimate”. In this book Sidis is studying many ideas which are very important in the evolution of science but also very crucial. So one of them is the reversibility. To do that, in fact he creates a reverse universe. He wants with this kind of test to introduce the reversible laws and to see how this is compatible or not with thermodynamics.