Mathematical cosmology is defined, informally speaking, as the study of whole universes. It started in 1917, when Albert Einstein showed how to build the first universe as a solution of his equations of general relativity.

Since then, it has developed into a vast theoretical science that uses dynamical systems and differential geometry methods and aims to study `universes’, solutions of Einstein’s and other gravity theories, and confront with the latest observations.

It has freed us from prejudices about our Universe, by separating the always unknown and unknowable Universe, from the many different universes-the possible constructions of mathematical and physical models of the Universe that we can build, study, and compare!