On that day We will fold the heaven, like the folding of a book. Just as We initiated the first creation, We will revert it. This is our promise. We will certainly fulfill it. (21:104)
"Experts versed in astrophysics will take cognizance of the magnificence of this verse. We know today that the universe is expanding. We also know that this expansion is the consequence of the acceleration generated by the Big Bang. We are faced with two alternatives here. According to one of them, the expanding universe will spread out to a vast expanse, all the stars will have exhausted their energies, the temperature will fall and thus the end will be reached. Following the exhaustion of the energy of the stars and the coming to a standstill of all actions, all celestial bodies will break apart and escape from gravitational force. This is called the "Open Universe Model". According to a second alternative, the expanding universe will stop because of the mutual attraction of all bodies and the universe will contract to return to its primordial state.
The collapse of the universe is referred to as the "Closed Universe Model". The power to realize this folding up is gravity. As we know, all matter is in mutual attraction. When something is thrown into the air, the object thrown cannot help falling back after some time because of gravity; matter that has scattered in every possible direction in space following the Big Bang will retrace its steps in a given time to be folded up. We must remember that at the time of the descent of the Quran the notion of gravity did not exist and that it was to be known some one thousand years later thanks to Newton's discovery.
Once the expansion of the universe was established, scientists began to study whether the universe would continue to expand or come to a close by folding up. To this end they tried to find out the critical density of matter in the universe and arrived at certain ratios they called "Omega". if the density in the universe is at a certain level, the process of folding up will begin before the scattering of matter into infinity.
Humans are born, live and die and eventually return to the dust of which they were made. The same thing holds true for beast and plants. It appears that the law that governs all living creatures is also applicable in the case of the universe."
- Unknown Author