Nothing in this universe is eternal everything has got its end. The one who has taken birth will die; each and every tits and bits that has been created will be destroyed. As stars take birth and destroy during the supernova. In the same way, the universe has been born in Big Bang has got its judgment day so called the doomsday. The day may come and it will come on which the pieces of stuff from massive stars to tiny atoms will perish. There are theories and hypothesis which tell us that how the universe will end.
The Big Crunch
One of the most staple theories for how the universe began is the Big Bang, where all matter first existed as a singularity, an infinitely dense point in the abyss of nothing. Then something caused it to explode. The matter expanded outward at an incredible rate and the universe formed which we see today.
A hypothetical opposite of the big bang is the contraction of the universe to a state of extremely high density and temperature. Big crunch states that gravity will eventually cause this expansion to slow down at a point where it halts and starts to contract in place of expansion. The contraction will bring all of that material (planets, stars, galaxies, black holes-everything) back to the centre until it becomes that infinitely dense singularity again, wiping out everything. And then there would be same conditions that the universe had been before the Big Bang all the matter of the universe condensed into an infinitesimal point.
This is, however, unlikely to happen based on current knowledge, and since recent discoveries had been done that the universe appears to be expanding at an accelerating rate.
Heat Death via Black Holes
The ‘heat-death’ of the universe is when the universe has reached a state of maximum entropy. In this case, gravity is not strong enough to overcome the expansion, so the universe just keeps on expanding. Galaxies drift apart like despondent lovers, and the all-encompassing night between them becomes wider and wider. The heat death of the universe will only occur if the universe will last for an infinite amount of time (i.e. there will be no big crunch). It will occur because according to the second law of thermodynamics, the amount of entropy in a system must always increase. The amount of entropy in a system is a measure of how disordered the system is – the higher the entropy, the more disordered it is.
Slowly the stars will all wink out, one by one, and enough energy won’t be left to ignite new ones. Finally, the entire universe will go dark. The matter will still be there, but in particle form, and its motion will be totally random. The universe will be in a state of equilibrium, and these particles will bounce off of one another without exchanging energy. We’ll be left with just particles in zero.
The End of Time
Another word for “time” is “change”. When transformation stops, time ceases. Calculating the death date of the last black hole, this marks the end of everything. If anything is eternal, it’s surely time. Whether there is a universe or not, time has to continuously go on. Otherwise, there would be no way to identify one moment from the next. But what if time lost momentum and just froze? What if there were no more moments? Just the same instant in time. Let us think that we are living in the universe that never ends. It has got an infinite amount of time, anything that could possibly happen has a 100 percent probability of happening. The same paradox happens if you have eternal life.
You live an infinite time, so anything that is possible is guaranteed to happen (and happens an infinite number of times). Thus, if you live forever, the odds of you becoming permanently incapacitated in some way reach 100 percent and you spend eternity cartwheeling through the darkness of space. Because this messed up a lot of calculations that try to predict outcomes in our universe (like the figures behind dark energy), scientists theorised something else: that time itself must eventually stop.
Assuming you were still alive to experience this (in billions of years, long after the Earth is gone), you’d never realise anything was wrong. Time would just grind to a halt and, according to scientists, “Then everything will be frozen, like a snapshot of one instant, forever.” But it wouldn’t really be forever since time wouldn’t be moving forward at all. It would just be that one instant in time. You’d never die. You’d never grow old. It would be a kind of false immortality. But you would never know.
The Big Bounce
It’s hard to decide what is more existentially challenging — the idea that the universe has lasted forever, or the alternative that it had a beginning. Is it more disturbing to contemplate the cosmos that stretches eternally behind us, or to imagine a time before which there was no time at all?
The concept Big Bounce is bit similar to the Big Crunch. Imagine g that gravity slows the expansion of the universe and condenses everything back into one single point. In this theory, the force of that rapid compression is enough to start off another big bang, and the universe starts again. In this model, things are not really get destroyed but they get reformed. Physics does not approve this explanation, so some scientists have claimed that perhaps the universe doesn’t go the whole way back to a singularity. Instead, it gets very close and is then repelled by a force like a ball is repelled when you bounce it off the floor. This “Big Bounce” would be very similar to a Big Bang, and would, in theory, produce a new universe.
The Big Rip
The Big Rip is a hypothetical cosmological model concerning the ultimate fate of the universe, in which the matter of the universe, from stars and galaxies to atoms and subatomic particles, and even space-time itself, is progressively torn apart by the expansion of the universe at a certain time in the future.
Eventually, the acceleration speeds up so much that, like the Enterprise at warp factor nine, it can’t take anymore and rips itself apart into nothingness.
The scariest part of this theory is that, while most of these scenarios take place long after the stars have burned out and nothing is left anyway, the Big Rip is scheduled to happen (at the earliest estimate) in another 16 billion years. At this phase in the universe’s existence, planets (and theoretically life) will still exist. And this universe-wide cataclysm could burn them alive, tear them apart, or feed them to the space lions that live between universes. It’s anyone’s guess. But it’s sure to be a far more violent death than the slow heat death most people were expecting.
Vacuum Metastability Event
The idea of a “Vacuum Metastability Event” is to apply this to the universal scale. What if the universe was in a local energy minimum? If it were to somehow tunnel to the global minimum, then the laws of physics would change and the universe as we know it would cease to exist.
When this happens, at some time in the universe, a bubble will appear. Think of it as an alternate universe (though it’s really the same universe with different properties). This bubble will expand in all directions at the speed of light and wipe out everything it touches. Eventually, this bubble will destroy everything in the universe.