Before the Big BangThere was nothing: space, time, matter, & energy didnt exist
Then everything changed, and we dont really know why.
It is the expansion of a singularity that formed the universe.
It created everything: Time, Space, and the Matter (atoms) that make up everythingThe Big Bang is the birth of the universe 13.7 billion years ago.
So what happened?
Everything was compressed into a tiny spec. It suddenly expanded very rapidly and was very hot. So what happened?
As it expanded it cooled and matter began to form by sticking together.
Eventually the matter clumped together into nebula clouds
Then gravity helped pull the matter in to make stars and galaxies.
Some of these stars died out & blew up. From the debris new stars and planets formed like our solar system.
The universe continues to expand, stretching space and time b/t the galaxies.
Edwin Hubble used a very powerful telescope to see:The Milky Way is NOT the only galaxyGalaxies are moving away from each other (if they are moving away now then at some point they must have been closer-George Lemaitre)What proof do we have for the Big Bang?
3. Leftover radiation fills all of space (space is now cold, 3K)4. The amount of Hydrogen & Helium found in the universe matches predictions.