What is the ‘big bang’ theory of origin of universe? What is the main difference between Indian cosmology and this theory?

● Big bang theory is most successful theory in explaining origin of universe and different stages of its development. It gained importance because it does not violate any known laws of physics.

● According to this theory, about 13.8 billion years ago, all the matter of universe were concentrated at single tiny point. This began to enlarge rapidly in hot explosion, and it is expanding still today. Subatomic particles were produced when universe was cooled after explosion. And then simple atoms were produced by these subatomic particles.

● These simple atoms formed big clouds of primary elements like hydrogen, helium, lithium. Stars and galaxies were formed by condensation of these clouds due to gravitation. Later,primary elements in stars or supernovas produced heavy elements.

● It has been found that speed of expansion of universe is increasing. Universe will go on expanding continuously and will freeze after cooling. Recently, large amount of dark matter and dark energy has been noticed in the universe. But what is its role? This question is not answered yet.

● The main difference between Big-bang theory and Indian cosmology is that in bigbang theory there was nothing before 13 billion years ago, it came out from zero. But in Indian cosmology there is repetitive cycle of developing and destroying after a limit and again developing from zero like a cycle of egg and bird.