MODERN AND CONTEMPORARY ASTRONOMY. – Edwin Hubble (1889-1953). The great epoch of cosmology begins at the beginning of this century with the construction of large telescopes such as the one at Mount Wilson California (100 inches). In 1917 astronomers identified individual stars in galaxies close. The great discussion between Curtis and Shapley begins, the former holding the existence of island Universes and the second, a true expert on Cepheid stars, resisting our galaxy losing its privileged status; in the Smithsonian, on April 26, 1920, they confront their theses as if it were about Copernicus and Ptolemy. For 1924 Hubble had discovered 36 Cepheids in spiral “nebulae” (galaxies) extending thus and definitively, the size of the Universe beyond the Via Milky.

Hubble uses those beacons of the Universe, made up of pulsating variable stars of regular period. In 1929 he gave surprising news, for its simplicity and transcendence, in a work of his entitled “A relationship between distance and radial velocity of extragalactic nebulae “, in which he warns that the farther away a galaxy is, with greater speed is moving away from us; in this relation, at double distance double speed of recession, at triple distance triple speed of recession … The consequences: the Universe is expand. That homogeneous and isotropic Universe, which expands relativistically, which according to Lemaitre it must have been born from an explosion, it has a limit constituted by its fabric of expansion, whose bodies travel approaching the speed of light.

Albert Einstein (1879-1955) and Stephen Hawking (1942). A. Eintein removes the Newtonian concept of absolute space and shows that light is wave and particle. With its expression E = mC2 of 1905, when formulating the Special Theory of Relativity TER, the bodies can become light and vice versa: Matter and Energy are then two aspects of the same thing. In 1916 he published the General Theory of Relativity TGR, which considers the acceleration of bodies and with which gravity is explained, not as a distance force but, as the deformation of Space-Time caused by the mass of the stars: Mass tells Space how it curves and Space tells Mass how does it move.

Support for ERT and GRT is in Maxwell’s Electromagnetic Theory (1831- 1879), in the field concept of Hertz (1857-1894) and Lorentz (1853-1928), and in the Minkowsky’s (1864-1909) pseudo-Euclidean space and Riemann curved geometry (1826-1866). In 1926 Eintein proved the existence of atoms with his studies on the Brownian movement, the effect of which is seen in smoke. The contributions of A. Eintein, next to of Max Plank’s Quantum Theory (1858-1947), Niels Born’s Atomic Theory (1885-1962) and the New Quantum Theory of 1925, allow to redo the foundations of the conception of the Universe. The Englishman S. Hawking, the most famous of today’s cosmologists, articulates two major Theories: the General Theory of Relativity and Quantum Mechanics. With them he has entered to the Event Horizon of the Black Holes and to the moment of the Big-Bang. He can solve the singularity of the Big-Bang with the incorporation of complex time. Between his his contributions are that black holes radiate, have temperature and entropy, and the change from the concept of a deterministic Universe to that of a probable Universe. Stephen Hawking’s Universe involves three concepts: • 1. Inflation. • 2. Quantum fluctuations. • 3. Anthropic Principle.

Quantum fluctuations in Hawking’s Universe, starting point to explain the origin of galaxies, have been verified with the spectacular results in the absolute and differential measurements of background radiation, observed by the project COBE, from 1989 to 1992. Today Cosmological Models and Observational Astronomy are shown as powerful supports and the only way to continue the development that previously large particle accelerators. Now it is not feasible to resort to the procedures of before because of the enormous cost of the instrumental methods of the physics of particles, to advance in the knowledge of the Universe and the laws that govern the cosmos.