The universe will "end in a big crunch," warns physicist

A physicist suggests that the universe has only been around for half of its 33 billion-year lifespan, and will one day change direction.

Evidence from dark energy suggests that the universe will end in a "big crunch" approximately 20 billion years from now.

The universe is approaching the midpoint of a possible lifespan of 33 billion years, according to new calculations by a Cornell physicist using the latest dark energy data. The findings suggest that the universe will continue to expand for about 11 billion more years before changing direction, contracting back to a single point in a dramatic “big crunch.”

Physics professor Henry Tay reached this conclusion after updating a theoretical model that includes the "cosmological constant," an idea first proposed by Albert Einstein more than a century ago and widely used by modern cosmologists to describe the expansion of the universe.

"For the past 20 years, people believed that the cosmological constant was positive, and the universe would expand forever," Tye said. "The new data seems to indicate that the cosmological constant is negative, and the universe will end in a big crunch."

Tye is the corresponding author of a study on the findings published in the Journal of Cosmology and Astroparticle Physics.

Predicting the fate of the universe

The universe, now about 13.8 billion years old, continues to expand outward. According to Tye, the future depends on the value of the cosmological constant: If it is positive, the expansion will continue forever. If it is negative, the universe will eventually reach a maximum size before changing direction and collapsing completely. His calculations support the latter scenario – a future in which the universe shrinks to zero, which would be the ultimate end of space and time.

The last thing is the conclusion that Tye reached through his calculation.

"This big crush defines the end of the universe," Tye wrote in the study. He determined from the model that the big crush will occur about 20 billion years from now.

New data from observations of dark energy

The big news this year is the reports from the Dark Energy Survey (DES) in Chile and the Dark Energy Spectroscopic Instrument (DESI) in Arizona this spring. Tye said there is a good agreement between these two observations, one in the Southern Hemisphere and one in the Northern Hemisphere. The whole idea of ​​these two groups’ dark energy surveys is to see if dark energy—68 percent of the mass and energy in the universe—really comes from a pure cosmological constant. They found that the universe is not just governed by a cosmological constant, dark energy. Something else is going on with dark energy.

In the paper, Tye and his colleagues proposed a hypothetical particle with a very low mass that behaved like a cosmological constant early in the universe's life, but no longer does. This simple model fits the data well but shifts the underlying cosmological constant into the negative realm.

"People have said in the past that if the cosmological constant is negative, then the universe will eventually collapse. That's not new," Tye said. "But here the model tells us when the world will collapse and how it will collapse."

Observations and the future of cosmology

There will be more observations, Tye said. Hundreds of scientists are measuring dark energy by looking at millions of galaxies and the distances between them, collecting more precise data to feed into the model. DESI will continue observations for another year, and observations are underway or will begin soon at several other locations, including the Zwicky Transient Facility in San Diego, the European Space Agency’s Euclid Space Telescope, NASA’s recently launched SPHEREx mission and the Vera C. Rubin Observatory (named after Vera Rubin, who received her master’s degree from Cornell in 1951).

According to Tye, it is encouraging that the lifespan of the universe can be determined quantitatively. When you know both the beginning and the end of the universe, you understand the universe better, which is the goal of cosmology.

"For all life, you want to know how life begins and how life ends – the endpoints," he said. "For our universe, it's also interesting to know, does it have a beginning? In the 1960s we learned that it has a beginning. So the next question is, 'Does it have an end?' For many years, many people thought that it would just go on forever. It's good to know that if the data holds up, the universe will have an end."

for the scientific article

More of the topic in Hayadan:

• Is the universe a bubble? – Scientists have proposed a way to test this
• The universe in a nutshell
• Hubble reveals: dark energy has existed for at least 9 billion years
• Stages in the formation of the stars of the universe