The early universe

The theories put forward in explaining the evolution of the universe, which is accepted as a totality of mass and radiation, are reviewed. The beginning of the universe with a big bang and the theory that it originated from a space-time singularity are discussed. The existence of elementary particles and the occurrences of weak and strong electromagnetic interactions, etc. which are predicted by these theories are also reviewed. The standard cosmological model, which assumes that (a) the cosmological principle is valid and (b) Einstein's theory of general relativity determines the dynamics of all motion, is developed in detail, to explain the evaluation of the Universe. This is done in stages as 'early universe' and 'very early universe'. Particle creation, annihilation and survival, all of which arise as a consequence of this model are explained theoretically. The relevance of Planck area for calculation of Planck mass has also been brought out. In the light of these discussions, it is concluded that the idea of space-time manifold, which is the underlying arena of all physical processes, may not be a valid concept anymore, so that one must be prepared to accept new and/or unfamiliar forms of matter as well as laws of nature. (K.B.)