Photo: hubblesite.org
It is scientifically accepted that the universe started with a rapid inflation called the Big Bang. But the question how our universe will die still needs to be answered. There are few theories about the ultimate fate of our universe. These theories lead us to the following three possible situations:
- The big rip
- The big freeze
- The big crunch and the big bounce
We know that the space in the universe is expanding at a faster rate than expected. Scientists theorized that the acceleration of space in the universe is because of the dark energy. It is called “dark” energy because we do not know what it actually is. About 25% of the known universe is estimated to be the dark energy. If the acceleration continues, one day space will expand so fast that gravity will not be able to hold the particles together and the big rip will happen.
In the big freeze, all the stars will be far far away from each other because of the expansion of the universe. After many many generations, all the stars and the gas clouds that create stars will run out of energies. So, there will be no stars and the universe will be a very dark and cold place.
The third situation will happen if the dark energy decreases over time. Then it is possible that one day gravity will start dominating over the dark energy and the galaxies will start getting closer to each other. If this happens, one day the whole universe will collapse into a dimensionless singularity. This is the big crunch. The big bounce theory says that there will be a big bang after the big crunch and the universe will start expanding again. The universe will go under contraction after the expansion and eventually the big crunch will happen again and they cycle will continue.
Here is a great video that explains the ultimate fate of our universe: