Physicists predict when the universe will end in a reverse Big Bang: ScienceAlert

If recent findings that dark energy evolves hold up, our Universe will collapse under its own gravity over a limited timeline, new calculations suggest.

Based on several recent results on dark energy, a new model reveals that the Universe has a lifespan of only 33.3 billion years. Since we are now 13.8 billion years after the Big Bang, this suggests that we have just under 20 billion years left.

For another 11 billion years, the Universe will continue to expand, before stopping and reversing direction, collapsing in the hypothetical Big Crunch, say physicists Hoang Nhan Luu of the Donostia International Physics Center in Spain, Yu-Cheng Qiu of Shanghai Jiao Tong University in China, and corresponding author Henry Tye of Cornell University in the United States.

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“For the last 20 years, people believed that the cosmological constant was positive and that the universe would expand forever,” says Tye. “The new data seems to indicate that the cosmological constant is negative and that the Universe will end in a Big Crunch.”

The cosmological constant Tye is referring to is λ, introduced by Albert Einstein in his theory of general relativity to describe the expansion of the Universe. If the value of λ is positive, then it acts as a force that constantly pushes outwards, thus contributing to the expansion of the Universe. If λ is negative, it behaves like a constant attraction that never fades and can eventually stop and reverse the expansion.

Recent observations suggest that dark energy could evolve over time. In the new model, the authors’ best fit goes with a small negative λ, although the current data does not rule out λ being 0. Since a negative λ pulls inward, it would hinder rather than help the expansion of the Universe.

Nevertheless, the Universe is indeed expanding, according to an overwhelming majority of evidence. But we can access the observed behavior of the Universe if we combine a small negative λ with an ultralight axion field that behaves like dark energy today.

We believe that axions are ultralight particles that can also be seen as a smooth, ghostly field in space, first proposed decades ago as a potential solution to other particle physics problems.

In their new analysis, Tye and his colleagues describe the axion as a force that gives the Universe a slight outward push at first, but slowly fades over time.

At present, axion influence still reigns, pushing the Universe outwards at an accelerating rate as gravity weakens between bodies moving further and further away from each other – so the Universe continues to accelerate today in this scenario.

However, in about 11 billion years, the axion’s thrust will weaken enough for the pull of negative λ to take over, stopping the outward expansion of the Universe at a maximum size of about 1.7 times its current size. Then the Universe will begin to contract again – reaching a Big Crunch in just 8 billion years.

It’s a bit like riding a bike up a hill, with a tailwind pushing you: on the way up, as the tailwind weakens, your ascent slows, then stalls gently at the top before descending the steeper side, gaining speed as you go.

According to the paper, the “downward” contraction is faster because the kinetic energy of the axion takes over and increasing densities strengthen the gravitational pull, making the contraction phase shorter than the expansion phase.

The Big Crunch is the opposite of the Big Bang, where all the matter in the Universe comes together into a single, infinitely dense singularity.

It is important to note that this is far from a certainty – not a prediction, but a possible future if recent indications can be validated. Much more data analysis will be needed to determine whether dark energy is indeed evolving.

Additionally, we still don’t know what dark energy is; they may not be axions or axion-like particles at all, but something completely different.

Nevertheless, this article provides a potential answer to one of the biggest questions in cosmology.

“For any life, you want to know how life begins and how it ends – the end points,” says Tye.

“For our Universe, it is also interesting to know if it has a beginning? In the 1960s we learned that it had a beginning. The next question then is: ‘Does it have an end?’ For many years, many people thought it would last forever. It’s good to know that if the data holds up, the Universe will end. »

The research was published in the Journal of Cosmology and Astroparticle Physics.