BIG BANG AND BIG CRUNCH:

According to modern science the whole matter present in the universe gets condensed into minimum space at one point of time. As this state is highly unstable, the condensed matter again explodes to form universe. While the universe is in time, the stars get burn out and become Black holes with highly condensed matter with huge gravity which will even absorb light.

By and by, the universe get filled with black holes (stars which died out) and the black holes attract each other and merge into one enormous black hole.

This gigantic black hole will suck up all the remaining matter (and even light) from the universe like a hyper vacuum cleaner. Thus again the matter becomes condensed into a massive black hole which contains all the matter and energy of the universe. This state being unstable again explodes to form the universe. Countless universes have thus come and gone in the unending infinite time. This will keep happening too. That is how the universe is designed and launched into existence.