May 16, 2022

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The universe may begin to expand and contract for billions of years

The universe may begin to expand and contract for billions of years

After about 13.8 billion years of continuous expansion, it could reach The universe According to new research published in the Journal of the National Academy of Sciences, it will soon become a plateau and then slowly begin to shrink.

In a new study published by ScienceAlert, three scientists have attempted to simulate the nature of dark energy – a mysterious force that appears to be rapidly expanding the universe – based on previous observations of cosmic expansion.

In the team model, dark energy is not a constant natural force, but a substance called essence, which decays over time.

Although the expansion of the universe has accelerated for billions of years, researchers have found that the repulsive power of dark energy can be weakened.

According to their model, the acceleration of the universe will end “quickly” within the next 65 years, and then within a hundred million years, the universe could completely stop expanding, but instead enter an era of slow contraction leading to billions of years. From now until the death or rebirth of space time.

Paul Steinhardt, director of the Princeton Center for Theoretical Science at Princeton University in New Jersey, said all of this could happen “remarkably quickly.”

He added: “If we want to go back sixty-five million years, we will reach the time when he struck. Asteroid The Cichloups landed and destroyed the dinosaurs … Sixty-five million years is a remarkably short time for us to speak of a universe. “

However, this model is based solely on previous observations of expansion – and the current state of dark energy in the universe remains a mystery – and it is currently impossible to test the study’s prediction, and its findings are mere theories.

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Vacuum energy

Since the 1990s, scientists have realized that the universe is expanding at a rapid rate, and that the distance between galaxies is now growing faster than it was billions of years ago.

Scientists have called the mysterious source of this acceleration dark energy – an invisible substance that works against the force of gravity, pushing large objects in the universe instead of bringing them closer.

Although dark energy makes up almost 70 percent of the total energy of the universe, its properties remain an absolute mystery.

A popular theory put forward by Albert Einstein states that dark energy is a cosmological constant – a constant form of energy embedded in the fabric of space-time. If, then, the force exerted by the dark energy never changes, the universe must continue to expand (accelerate) forever.

However, a different theory suggests that dark energy does not have to be constant to accommodate previously observed cosmic expansion.

Alternatively, dark energy can be a center – a dynamic field that changes over time.

In contrast to the cosmological constant, an object can be repulsive or attractive, depending on the ratio between its kinetic energy and its potential energy at a given time. For the past fourteen billion years, Essence has been a chaser.

For most of that period, his contribution to the expansion of the universe was minimal compared to radiation and matter. About five billion years ago, the center became the dominant component and the effect of gravitational pull accelerated the expansion of the universe.

“The question we ask in this study is, should this acceleration continue forever? If not, what are the alternatives, and how quickly can things change?” Steinhardt said.

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Dark energy death

In their study, Steinhardt and his colleagues, Anna Igas of New York University and Cosmin Andre of Princeton University, predicted how the properties of matter would change over the next few billion years.

To do this, the team developed a physical model of the center showing its repulsive and attractive forces over time, in line with previous observations of the expansion of the universe. Once the team’s model was able to reliably reconstruct the history of the expansion of the universe, the researchers withdrew their predictions for the future.

Gary Henshaw, a professor of physics and astronomy at the University of British Columbia, who was not involved in the study, said: “The researchers were surprised that the dark energy in their model could decay over time … weakening its strength.

According to the group’s model, the repulsion of dark energy may have begun to decline rapidly billions of years ago.

Under these circumstances, the rapid expansion of the universe is already slow today. Soon, perhaps in sixty-five million years, this acceleration will be completely stopped, and then in a hundred million years the dark energy will become attractive, and thus the whole universe will begin to shrink.

In other words, after about fourteen billion years of development, the universe may begin to shrink.

But this contraction will be very slow at first, no man still alive on earth will notice any change, and the universe will contract slowly for a few billion years to reach half its size.

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Is this the end of the universe?

Steinhardt said there are two possibilities after the universe begins to shrink: either the universe collapses completely until it shrinks, or shrinks to the point where it returns to its original state, or another big bang. Occurs – or a new remnant of the old universe that is a great “re-” that leads to the creation of the universe.

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In this second scenario, the universe follows a continuous cycle of expansion, contraction, disappearance, and regression as it continually collapses and reshapes itself.

If this is true, our present universe may not be the first or only universe, but rather the latest in an endless chain of universes expanding and contracting before us. And it all depends on the dynamics of the dark energy.

Henshaw described the new study for the center as “a perfectly reasonable assumption of what dark energy is.”

Since all of our observations on cosmic expansion come from objects millions to billions of light-years from Earth, current data can only give scientists an idea of ​​the past of the universe, not its present or future.

Therefore, the universe may be on the verge of extinction, and there is no way for us to know long after the contraction phase has begun.

“I think it boils down to how committed you are to that theory and, most importantly, how testable you are?” Henshaw said.

Unfortunately, Steinhardt admits, there is no better way to test whether the essence is real, or whether cosmic expansion has begun slowly.

Only in time will we know whether the future of endless growth or rapid decay awaits our universe.