According to my research: the whole universe works like a big star.
At first, the environment of the big star expands. Then the terminal bodies collapse and the star's environment shrinks. And these events are repeated several times. Expansion, contraction, re-expansion, contraction.
Each time the kernel size gets smaller. Finally, three things happen.
1- The big collision with the star and destruction. 2- Ejecting all objects around the star and exploding the core of the star. 3- The star shrinks to the size of an atom.
I prepared an article about the birth to death of a star with all the details and mathematical formulas.
Everything is based on classical physics.