There are some other theories apart from big-bang to explain the formation of the universe. They are as follows:
1. Steady State Theory: It suggests the continuous creation of matter throughout the universe to explain its continuous expansion. Such a universe will be infinite with no beginning or end.
2. The Oscillating model of Universe: It involves an endless series of big bangs, followed by Big Crunches that restarted the cycle, endlessly.
3. Eternal Inflation theory: It is slightly different from Big bang theory. it states that the inflation of universe never stopped after the big bang, and has been going on for an infinite length of time. New universes are coming into existence even now and those universes could have different physical laws from ours.