By tearing, freezing, crushing, or a false vacuum How will the universe end?

Cosmologists today agree that the universe is expanding at an accelerating pace due to what they call dark energy, a strange phenomenon that permeates the entire universe and has a physical impact on its fate.

In the 1920s, the American astrophysicist Edwin Hubble discovered that galaxies are moving away from each other as a result of the continuous expansion of the universe since its inception about 13.8 billion years ago. Scientists wondered: Will the universe continue to expand indefinitely, and what is its fate?

Cosmologists today agree that the universe is expanding at an accelerating pace due to what they call dark energy, a strange phenomenon that permeates the entire universe and has a physical impact on its fate.

But there is a big problem for scientists, which is that there is currently no possible way to prove the existence of dark matter and measure its quantities that would determine the fate of the universe in the future and how it will end? Will it continue to expand, or will it contract itself again? Therefore, scientists put forward various hypotheses that predict how the universe will end.

Many theories suggest that the universe will end one day, but what will this end be? This question generated many physical hypotheses that predict the fate of the universe, here are the most important ones.

The Great Freeze or Heat Death

The first scenario of the end of the universe is the scenario of it freezing as a result of its thermal death. Since its inception about 13.8 billion years ago, the universe has evolved - according to some scientists - from a state of order to a state of chaos and will eventually reach a state of extreme chaos, just like a sugar cube that gradually dissolves in a cup of tea, but it will take a very long time to return properly. Random to structured cube structure.

In the event of extreme chaos, the heat in the entire universe will be distributed evenly, according to a report published on the website " Phys.org " (Phys.org), and this means that there will be no more usable energy, and the mechanical movement inside the universe will stop and it will freeze in the so-called "freezing" The Big Freeze, which is a reflection of the heat death of the universe.

In this scenario, the stars would eventually run out, and as their fuel ran out, the universe would get darker and then black holes would appear all over it, which would in turn disappear over time.

According to the best physical models of the evolution of the universe, this scenario is most likely if dark energy continues to accelerate the expansion of the universe forever. But his slow death will last for a very long time, estimated at about one googol of years, i.e. one followed by 100 zeros!

The Big Rip

According to the hypothesis called the "Big Rip", the acceleration of the expansion of the universe will increase with time so that all the stars and galaxies will gradually disappear from our sky. Then the large cosmic structures begin to gradually collapse due to the diminishing effect of gravity.

This force will not be able to hold galaxies together, and their clusters will begin to disintegrate, and eventually the  same will happen inside galaxies, the stars will be freed from the influence of each other and the planets leave their orbits around the stars. 

Once space begins to expand faster than the speed of light, until the atoms disintegrate, no particle in the universe can interact with any other particle after that moment. The accelerating expansion will reduce the field of influence of fundamental forces, such as gravity or electromagnetism.

In the last few hours of existence, this field will shrink to smaller than the size of particles, disrupting the forces that hold matter together, and the atoms themselves disintegrating into smaller particles before the very fabric of spacetime itself is torn apart.

According to the New Atlas website , the scientists who propose this hypothesis estimate that the universe has about 22 billion years before it ends in this way. Fortunately, other scientists believe that this scenario contains unrealistic parameters, so it is less likely than other scenarios.

The Great Crush

But what if dark energy decreased over time and the density of matter in the universe was high enough? In this case, not only would the universe's expansion rate slow down, but it would also reverse, with gravity becoming the dominant force.

This will eventually lead to the shrinkage of the universe, merging galaxy clusters, galaxies colliding with each other and then the stars little by little. As the universe continues to shrink, the temperature will rise everywhere at once until the stars evaporate. This scenario is called the Big Crunch.

In the last moments of the universe's life, its temperature will be so high that the atoms themselves will disintegrate before being swallowed by the black holes that will occupy an increasing proportion of the shrinking universe. Eventually, the entire contents of the universe will be crushed into an extremely small space, in a reversal Big Bang.

Scientists differ in estimating when this phase of contraction may begin, but a recent scientific study - published on the website of the National Academy of Sciences " PNAS " - showed that this scenario may be very close in cosmological terms, as the universe will reverse its course after about 100 million years from now. In contrast, it will take about a billion years before we return to this singularity.

The 'pseudo' void

The previous three scenarios assume that our universe is the only universe in existence. But what if he's just part of a multiverse? Can these other universes affect our ultimate destiny?

The answer is yes, according to Discover magazine. If this is the case, then our universe will exist in a state known as a false vacuum, where we mistakenly assume that we are in the most stable state, but the picture can still change suddenly and subject to laws other different.

In this case, the universe would be like a bubble in a pot of boiling water, governed by its own laws. But bubbles (universes) can collide with each other, which means an immediate end to our universe as everything changes to a new state, which can result in a mixture of the two universes, or the formation of something completely new.