What is Big Bang?

The Big Bang is the beginning of the universe, it is the beginning of space-time, the beginning of time itself. It is one of the most interesting concept of theoretical physics and astrophysics.

According to this theory, the universe expanded from a point of infinite density(singularity). We don't know the reason for this expansion neither our present telescope and physics can predict or see what was there before the Big Bang but we know what is there after the Big Bang and can predict that what happened during it.

Just imagine that all the matter of the universe compressed into a sphere as small as an electron expanded but due to the intense pressure the matter became energy through Einstein's E=MC*C equation where E= energy, M = mass and C= speed. 

The amount of energy in some places was more compared to other places which mean that the energy was unevenly distributed.

When this energy cooled down the first subatomic particles were formed. This subatomic grouped and formed the first atoms were formed. But the problem was that half of the energy became antimatter, as a result, there was kind of a war between antimatter and matter in which most of the matter, when combined with antimatter, formed energy. Fortunately, the amount of matter was more than that of antimatter and that is the matter from which whole of the known universe is made of. Now, the question arises that what happened to the energy that was released from the contact of these antimatter and matter particles?

As an answer to this, some scientists suggest that it is what we call dark energy while the other says that with time it red-shifted so much that now we can receive it as a very faint microwave or radio waves.