A Big Crunch: How the Universe Could Collapse in 20 Billion Years

[Buster's Uncle]

A Big Crunch: How the Universe Could Collapse in 20 Billion Years
Cassidy Ward
SYFY
Mon, October 13, 2025 at 5:47 PM EDT
4 min read


Dark energy is one of the most mysterious concepts in all of the cosmos. We know very little about what it is but it just might play an overwhelming role in the death of the universe. Often referred to as a cosmological constant, dark energy is thought to be responsible for the increasing expansion of the universe.

Now, recent discoveries from the Dark Energy Spectroscopic Instrument (DESI) at the Kitt Peak National Observatory in Arizona suggest that dark energy’s influence is actually weakening, and that expansion could slow, stop, and reverse course in the future. If that’s true, we’ll need a new model of the cosmos and how it evolves over time.

A new study published in the Journal of Cosmology and Astroparticle Physics proposes an alternative model which gives the universe an expiration date. According to this new model, everything will come to an end about 20 billion years from now (relatively soon on cosmological timescales) in a rapid and violent crunch.


How the universe could come to an end: Big Freeze or Big Crunch


Dark Energy


On human timescales, the universe may as well be eternal. It’ll be here long after our species and our planet are gone, but it does have an end. The generally accepted long-term evolution of the universe involves eternal expansion and a long, slow death.

Dark energy drives expansion and that expansion gets faster over time. Meanwhile, the second law of thermodynamics tells us that no process is totally efficient and waste heat is always lost. As a result, the overall entropy of the universe increases. Over a long enough period, all that remains will be the waste heat of the things that once existed. The cosmos will be a cold, dark, empty place that’s continually expanding.

A hundred billion years from now, cosmologist Katie Mack explains, things will have spread apart so much that we won’t be able to see distant galaxies anymore. Today, when we point the Hubble telescope or JWST at pretty much any point in the sky, we see countless galaxies, sometimes dating back to near the beginning of time. When future astronomers point their telescopes at the sky, they’ll see nothing but the stars inside their own galaxy and darkness.

About a trillion years from now, there will be no stars at all. The longest-lived stars will be dying out and no new stars will be born. Black holes will still exist but with nothing new to gobble up, they’ll slowly evaporate. Even the smallest black holes will take an incredible amount of time to fizzle out, on the order of 10 to the power of 65 years, and supermassive black holes will take longer. After that, nothing will happen. The universe will still exist, and it will keep expanding, but as the cosmic equivalent of an empty sheet of paper upon which nothing is ever written.



Expanding Universe


We call that process Heat Death, otherwise known as the Big Freeze, and it all comes out of the cosmological constant, that constant expansive pressure which pushes the stars apart. The new study changes the cosmological constant and, therefore, changes the universe’s future.

“For the last 20 years, people believed that the cosmological constant is positive, and the universe will expand forever,” explains Henry Tye, the Horace White Professor of Physics Emeritus in the College of Arts and Sciences at Cornell University, in a statement. “The new data seem to indicate that the cosmological constant is negative, and that the universe will end in a big crunch.”

Using the new DESI data, researchers proposed a new model which suggests expansion will slow over time, coming to a halt about 11 billion years from now, before reversing course. Contraction will be comparatively rapid. The universe will be about 25 billion years old when expansion stops and only about 34 billion years old when it collapses into a singularity in an event known as the Big Crunch.

The new model relies on a field of axions, a low-mass hypothetical particle which behaves like the cosmological constant but changes over time. In this model, the cosmological constant becomes slightly negative.

“People have said before that if the cosmological constant is negative, then the universe will collapse eventually. That’s not new,” Tye said. “However, here the model tells you when the universe collapses and how it collapses.”

The authors note that their conclusions are far from confirmed and future observations could reinforce or refute their model. But the age of dark energy astronomy is alive and well and someday soon we may be able to say with relative certainty how and when the universe will end.

https://www.yahoo.com/news/articles/big-crunch-universe-could-collapse-214708667.html