# Describe the collapse phase of Penrose cyclic universe, Conformal cyclic cosmology

I read about Penrose's idea of Conformal cyclic cosmology, he suggested that mostly everything at the end of the universe is black holes and empty space and that eventually the black holes evaporate at which time there is only light going through the universe.

Then why does the universe collapse? What does collapse mean in this circumstance? I wish to understand in a realistic physical sense of what is happening in his model at this time.

There is no collapse. The black holes evaporate, the particles get indefinitely diluted, space expands indefinitely, and time continues to $t=\infty$. Then the state is equivalent to the big bang state, if one rescales the whole thing conformally.