The Universe was born approximately 13.8 billion years ago. This moment, which marks the beginning of our knowledge, has been called the “Big Bang”. While all the energy and all the mass of our Universe were grouped into a single point, a singularity, the latter “exploded”.
Since then, we have studied this universe and our world, although still full of secrets, is understood in broad terms. In particular, we discovered that the Universe was still expanding, as during the Big Bang. There are now two major theories, both of which lead to the same conclusion, that of the “thermal death of the Universe” or “Big Freeze” in English.
The “Big Freeze”: an inevitable future?
The first is that the Universe is a closed world, with limits (although still unknown). Then, as the second law of thermodynamics dictates, the Universe would gradually end up losing all its energy. Since energy is not conserved, it will disperse throughout the Universe, forming a sort of uniform energy soup, similar to the world that ours was before the Big Bang.
The second hypothesis, on the contrary, is that the Universe is open and limitless. In this scenario, the expansion will continue, to the point of emptying it of all its substance. The energy will then be lost forever. It is possible to imagine these two theories by visualizing an enclosure.
If the enclosure is closed, and nothing can escape, the animals inside will breed to a critical point where they will step on each other, then they will be distributed evenly in their given space, stopping, de factotheir growth. If, on the other hand, a door to the enclosure remains open, it will gradually empty to the point where no animal will be in the enclosure. He will then have lost all his energy and will no longer be able to gain any more.
A 150-year-old theory
The idea of a reduction in the amount of energy in the Universe is not new. In the very long term, it is even likely that the energy will dissipate. It is today very poorly distributed. It was Baron Kelvin who first theorized this idea in the 1850s. Since then, it has been debated hundreds of times, without anyone being able to provide proof to confront or affirm it.
Other possible destinies for the Universe?
If you don’t like this idea of a cold, lifeless end of the world, fortunately there are other theories about the end of the Universe. One of them also wants that the Universe never actually ends. According to this idea, known as the “Big Crunch”the Universe will continue its expansion until it reaches a critical point. At that point, the Universe will work in reverse and will begin to contract.
It will shrink little by little, faster and faster, to the point of reaching ridiculous dimensions and taking the form of a singularity, like during the Big Bang. For some, this sequence between phases of expansion and contraction could allow the Universe to exist outside of any notion of time. There would then have been other Universes before us, just as there will be others after us, whose tiny differences during their creations made them unique.
