Principles of cosmology.
Cosmology. The beginning of cosmology. Edwin Hubble showed at the beginning of the XX century that the universe was in constant expansion, since he, with his rustic telescope, observed that the Andromeda galaxy had a slight red shift in its light spectrum, which was only explicable by the expansion of the universe. Breaking completely with the belief of the time inspired by Newton, that the universe was eternal and motionless, ushered the in a new era of cosmology. Friedman, during the years 1922-1924 with Robertson and Walker, proposed a model that was the exactly solution to Einstein's field ecuations , in which an in expansion, homogeneous and isotropic universe was described and three standard models of universe were created. Three years later Lemaitre would join to the group, proposing an universe in expansion without center, with beginning in...