General Relativity and Casmology | for M.Sc | Bianchi Identity (Short Question) | by KRISHNA SINGH

General relativity, also known as the general theory of relativity and Einstein's theory of gravity, is the geometric theory of gravitation published by Albert Einstein in 1915 and is the current description of gravitation in modern physics. General relativity generalizes special relativity and refines Newton's law of universal gravitation, providing a unified description of gravity as a geometric property of space and time or four-dimensional spacetime. In particular, the curvature of spacetime is directly related to the energy and momentum of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of second order partial differential equations.Cosmology (from Ancient Greek κόσμος (kósmos) 'world', and -λογία (-logía) 'study of') is a branch of physics and metaphysics dealing cwith the nature of the universe. The term cosmology was first used in English in 1656 in Thomas Blount's Glossographia,[2] and in 1731 taken up in Latin by German philosopher Christian Wolff, in Cosmologia Generalis.[3] Religious or mythological cosmology is a body of beliefs based on mythological, religious, and esoteric literature and traditions of creation myths and eschatology. In the science of astronomy, cosmology is concerned with the study of the chronology of the universe.cosmology, field of study that brings together the natural sciences, particularly astronomy and physics, in a joint effort to understand the physical universe as a unified whole. The “observable universe” is the region of space that humans can actually or theoretically observe with the aid of technology. It can be thought of as a bubble with Earth at its centre. It is differentiated from the entirety of the universe, which is the whole cosmic system of matter and energy, including the human race. Unlike the observable universe, the  universe is possibly infinite and