The end of the expansion of the Universe would be soon

Depuis le Big Bang, l'Univers est en expansion accélérée. © Andrea Danti, Adobe Stock

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In 1998, scientists discovered, through two parallel studies, that Supernova type SN Ia they were moving away from each other faster and faster. Those supernovahis issues binary systems containing a white dwarfare considered landmarks in cosmologyalso called typical candleswhy them shine remains constant over time. However, when the researchers evaluated the distance between them as a function of time, they noticed that it was growing faster and faster as a function of time! We already knew at that time that theUniverse was expanding, but its model big explosion supposedly slowing this expansion: the observations showed the opposite.

Dark energy of unknown origin occupies more than 70% of our Universe

The only explanation found for this phenomenon concerned the presence of a pressure negative caused by an unknown substance. Named ” dark energy Since then, calculations have shown that it covers more than 70% of the energy content of our Universe, without being able to recognize it. Undetectable despite numerous attempts, however, several theories have tried to model it. The most widely used model today is typical cosmological modelwhich requires constant acceleration and depends on cosmological constant L., which represents the energy of the vacuum. In this case, the acceleration is constant, so the expansion will continue indefinitely. But let us look at another model, less well known: it presupposes a dynamic dark energy, that is, variable in time.

More specifically, dark energy would be like a substance determined by a gradient field, called quintessence. Each point in space is associated with a value of this quintessence V (Φ), which depends on the energy density and material that surrounds it. It then varies over time, thus contradicting the theory that relates to dark energy cosmological constants. She wave length would be of the order of magnitude of the Universe, giving it almost zero kinetic energy. Since the pressure associated with quintessence depends on the ratio between kinetic energy and dynamic energythis is negative, therefore consistent with a repulsive energy.

Acceleration would slow down in a few million years

According to this model, quintessence can interact with ordinary matter when it is in large quantities, such as astral system, or even larger, a galaxy. Thus, in the beginning of the Universe, when it was still solid, quintessence and matter would have interacted strongly, creating a kind of acceleration explosion. Then to stars removed, the density of matter decreases to become almost constant, hence the interaction with quintessence.

In a study published in the journal Proceedings of the National Academy of Sciences, a team of cosmologists explored the idea of ​​quintessence. And their model predicts several changes for the expansion of the Universe: first, its acceleration will slow down and then it will stop soon, and then instead of expanding the Universe will contract slowly. Their calculations assume a gradual increase of kinetic energy and a parallel decrease of dynamic energy: hence the evolution towards a positive pressure, which tends to shrink the Universe instead of stretching it: As the density of positive dynamic energy decreases and the density of kinetic energy exceeds it, the current phase of accelerated expansion will end and go smoothly into a period of decelerating expansion. Then, as the gradient field continues to decrease the potential, the dynamic energy density will become negative enough that the total energy density and therefore its parameter Hubble H

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