Origin of universe.

Origin of Universe There are several theories regarding the origin of universe but most accepted is Big-Bang theory.

Big-Bang Theory This theory was proposed by Abbe Lemaitre in $1931.$  According to the Big-Bang theory about $15$ billion years ago, cosmic matter was in a condensed form. Explosion took place which broke the condensed matter and scattered its fragments into space at an enormous velocity making a Big-Bang sound and thus the theory came to be known as the Big-Bang theory