The Universe may not expand forever as once believed. A new study now suggests it could one day collapse under its own gravity, reversing everything we know about cosmic destiny.
What does the new research say?
Physicists from Cornell University in the United States, Shanghai Jiao Tong University in China, and the Donostia International Physics Center in Spain have proposed a fresh model based on recent findings about dark energy. Their calculations suggest the Universe could have a total lifespan of 33.3 billion years.
Since the Big Bang occurred 13.8 billion years ago, that leaves less than 20 billion years before everything ends in a cosmic collapse. The study, published in the Journal of Cosmology and Astroparticle Physics, suggests the expansion will continue for about 11 billion more years before halting and reversing direction.
Why would the Universe stop expanding?
For two decades, scientists believed the cosmological constant, known as λ (lambda), was positive. That meant the Universe would keep expanding indefinitely. But according to lead researcher Henry Tye, new data hints λ could be slightly negative.
“If λ is negative, it acts like a constant pull,” Tye explained. It retards expansion and can ultimately cause the Universe to contract."
This constant, which was first formulated by Albert Einstein in his general theory of relativity, explains the rate at which the Universe is expanding. A positive value propels outward motion, and a negative one acts like gravity's opposing force.
What role does dark energy play?
Recent studies suggest dark energy, the mysterious force driving expansion, may not be constant. The new model combines a small negative λ with an ultralight axion field, which currently behaves like dark energy.
Axions are hypothetical, light particles that serve as a ghostly field throughout space. Here, the axion provides the Universe with its present outward push but dissipates over time. As the axion dissipates, the negative λ might overwhelm the inward pull, ultimately halting expansion.
When will the Universe begin to collapse?
The team predicts that in about 11 billion years, expansion will stop when the Universe reaches around 1.7 times its current size. After that, contraction will begin, leading to a “Big Crunch” roughly 8 billion years later.
The process has been compared to riding a bike uphill with the wind. As the push weakens, the rider slows, reaches the top, and then speeds downhill. Similarly, the Universe would accelerate downward as gravity takes over, pulling all matter into a single dense point.
How certain is this scenario?
The researchers stress that this is not a confirmed prediction but one possible outcome. Much depends on whether new data confirms that dark energy is evolving over time.
“We still don’t know what dark energy really is,” Tye said. “It might not be axions at all, but something entirely different.”
Still, the study offers a new way to think about the Universe’s life cycle. “It’s natural to ask how everything begins and ends,” Tye added. “If the data hold up, we may finally know that the Universe, like life, has an end.”
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