After 13.8 billion years of continuous expansion, the universe may stop and then begin to slowly contract.. This is evidenced by the data of a study published in the journal Proceedings of the National Academy of Sciences, and Live science briefly talks about them..

In the study, the three scientists attempted to model the nature of dark energy — a mysterious force thought to be causing the universe to expand ever faster — based on past observations of cosmic expansion.. In the team's model, dark energy is not a constant force of nature, but an entity called quintessence that can change over time..

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The researchers found that even given that the expansion of the universe has been accelerating for billions of years, the repulsive force of dark energy may be weakening.. Simulations have shown that the acceleration of the universe can stop within 65 million years. In the next 100 million years, it may stop expanding altogether and enter an era of slow contraction, which will end after billions of years, with the death or rebirth of space and time..

Scientists think it could happen 'impressively' quickly.

“If you go back 65 million years, this is the time when the asteroid Chicxulub crashed into the Earth and destroyed the dinosaurs.. On a cosmic scale, 65 million years is surprisingly short,” said study co-author Paul Steinhardt..

Gary Hinshaw, who did not take part in the study, said that there is nothing controversial or implausible in the new theory.. However, since it was based on past observations of the expansion of the universe. In addition, the nature of dark matter is still a mystery to scientists, so it will not be possible to verify the findings of the study in the near future..

Scientists realized that the universe is expanding in the 1990s. Now the distance between galaxies is increasing faster than billions of years ago.. The force behind this acceleration is what scientists have called dark energy, an invisible substance that works against gravity and pushes massive objects away rather than pulling them closer together..

Despite the fact that dark energy accounts for about 70% of the mass-energy of the universe, its nature remains a mystery to scientists.. A popular theory proposed by Albert Einstein is that dark energy is a cosmological constant - an unchanging form of energy woven into the fabric of spacetime.. If this is the case, and the force created by dark energy can never change, then the universe must continue to expand (and accelerate) forever..

But another theory suggests that dark energy doesn't have to be a constant to be consistent with past observations of cosmic expansion.. Rather, dark energy is something called quintessence, a dynamic field that changes over time..

Unlike the cosmological constant, quintessence can be both repulsive and attractive.. For the past 14 billion years, it has been repulsive, but this changed about five billion years ago when it became the dominant component and its gravitational repulsion caused the expansion of the universe to accelerate..

The scientists' model shows that at the moment, the repulsive force of dark energy may be in the process of rapidly decreasing, which began several billion years ago.. In this scenario, the acceleration of the expansion of the Universe is already slowing down today. After 65 million years, the acceleration may stop completely, and after just 100 million years, dark energy may begin to attract, causing the universe to contract.. That is, after 14 billion years of expansion, space may begin to shrink..