Question

when did the big baang happen

Answer 1

13.7 billion year ago

Answer 2

Here's your answer looking for

The Big bang was happened 13.8 billions years ago.

But now I want to explain this topic so here we go.

The big bang theory is one of the most mind blowing theory.
This theory and solve the most amazing and mysterious question that is
"What is the origin of universe?"

According to this theory, 13.8 billions years ago, our whole universe was compressed in a point mass. And because of this compression there was a tremendous amount of heat about billions of Kelvin.
And has very high gravitational force.

Because of that heat, there was a huge explosion in that point mass.
After that explosion, all the things start spreading all around and going far from each other.

After the explosion also there was a tremendous amount of heat, in which life is obviously not possible.

But, in a microsecond after that explosion, there was instant decrease in temperature. The temperature falls from the bilion of Kelvin to the million of Kelvin.
But this temperature is also not support for a life.
So, because of this tremendous temperature, there was the formation of quark gluon plasma.

This quark gluon plasma is sixth state of matter, that is formed in a huge amount of temperature in which, the quark and the gluon starts melting.
And this melting results as the formation of quark gluon plasma.

So, as the time passes, after thousands of years, there was huge fall in temperature.

And this results as the formation of fundamental subatomic particles, that is neutron proton and electron.

Now, the first element was formed, that was hydrogen along with Helium with the trace of lithium.
And as the time passes, the new elements are also formed.
But, the hydrogen become the fundamental element of the universe.
And because of this only the stars or sun are also formed because they are also made up of hydrogen and helium.

And after this all happenings, our universe was formed.
And today, don't know on how many planets the life is possible.
And one of them is our Earth.

So this was the Big Bang Theory.

Hope you are satisfied with my answer