ABSTRACT
Cosmology is based on the general theory of relativity (GTR). The GTR postulates that space-time is curved and dynamical. In Newtonian mechanics we think of space-time as a background stage on which particles reside, move and interact with one another. The space-time itself does not change with time. It is assumed that the three-dimensional space has zero curvature and, hence, can be described by Euclidean geometry. In contrast, Einstein's general theory of relativity postulates that space-time is curved. Furthermore, it is dynamical, that is, we cannot think of it as a background stage. The space-time itself evolves with time. The gravitational force is a manifestation of the space-time curvature. The evolution of space-time is determined by its matter content.
