The Big Bang Theory is the most accepted explanation for the beginning of the universe.
This theory is not just about the beginning of the universe, it also explains how the universe grew, expanded, and what it looked like, along with the concept of time formed after the beginning of the universe.
Laid out in the 1920s by Russian physicist, mathematician Alexander Friedmann, and Belgian mathematician, astronomer Georges Lemaître, this theory was largely accepted because it was supported by various proofs.
The theory says that the universe, which is still expanding, was in a very hot and dense state before it began expanding 13.7 billion years ago.
This assumption, which Georges Lemaître had previously called the “first Atom hypothesis”, is now referred to as the “Big Bang Theory”.
The expanding universe is likened to a balloon being inflated. Imagine that there are different colored dots on the surface of the balloon, and each of these dots is a different galaxy, and as you inflate the balloon, these galaxies move away from each other. Because we live in one of these galaxies, it looks like all the other stars are moving away from us.