LOG#107. Basic Cosmology (II).

Evolution of the Universe: the scale factor The Universe expands, and its expansion rate is given by the Hubble parameter (not constant in general!) Remark  (I): The Hubble “parameter” is “constant” at the present value (or a given time/cosmological age), … Continue reading

LOG#105. Einstein’s equations.

In 1905,  one of Einstein’s achievements was to establish the theory of Special Relativity from 2 single postulates and correctly deduce their physical consequences (some of them time later).  The essence of Special Relativity, as we have seen, is that  … Continue reading