Recent findings from dark energy research indicate that the universe may face a dramatic conclusion known as a “big crunch” approximately 20 billion years from now. According to calculations by Cornell physicist Henry Tye, the universe is currently nearing the halfway point of a predicted 33-billion-year lifespan. This groundbreaking research suggests that the cosmos will continue to expand for about another 11 billion years before reversing its trajectory and collapsing back into a singular point.
Tye, who holds the title of Horace White Professor of Physics Emeritus in the College of Arts and Sciences, arrived at these conclusions by updating a theoretical model that integrates the cosmological constant. This concept, originally proposed by Albert Einstein more than a century ago, is crucial for modern cosmologists in describing the universe’s expansion. “For the last 20 years, people believed that the cosmological constant is positive, and the universe will expand forever,” Tye explains. “However, the new data seem to indicate that the cosmological constant is negative, suggesting that the universe will ultimately end in a big crunch.”
The universe, which is roughly 13.8 billion years old, is currently in a state of expansion. Tye emphasizes that the future of the universe hinges on the value of the cosmological constant. If it remains positive, the expansion will continue indefinitely. Conversely, if it is found to be negative, the universe will eventually reach a maximum size before reversing direction and collapsing entirely. Tye’s calculations support the latter scenario, indicating a future marked by the universe contracting to zero, marking the ultimate conclusion of space and time.
This year has brought significant developments in dark energy research, particularly through the reports from the Dark Energy Survey (DES) in Chile and the Dark Energy Spectroscopic Instrument (DESI) in Arizona. Tye noted that these two observatories, located in the northern and southern hemispheres, align in their findings. The primary objective of these dark energy surveys is to determine if dark energy, which comprises approximately 68% of the universe's mass and energy, originates purely from a cosmological constant.
However, the data suggests that dark energy may involve additional complexities. Tye and his collaborators propose a hypothetical particle of very low mass that initially acted like a cosmological constant early in the universe's life but no longer does. This model aligns well with the data while indicating that the cosmological constant has shifted into negative territory.
Looking ahead, Tye remains optimistic about the ongoing observations in dark energy research. Hundreds of scientists are engaged in measuring dark energy by studying millions of galaxies and the distances between them, which will contribute to refining the model. DESI will continue its observations for another year, while other projects are either underway or will commence soon, including the Zwicky Transient Facility in San Diego, the European Euclid space telescope, NASA’s recently launched SPHEREx mission, and the Vera C. Rubin Observatory.
Tye finds it encouraging to quantify the lifespan of the universe. Understanding both the beginning and the end of the universe enhances our grasp of cosmic dynamics, which is the primary goal of cosmology. “For any life, you want to know how life begins and how life ends – the endpoints,” he asserts. “For our universe, it’s fascinating to learn about its beginning and, now, its potential end.”
This research highlights a significant shift in our understanding of the universe's fate, transitioning from the belief in endless expansion to the possibility of a definitive conclusion. As more data emerges, the scientific community awaits to see if this theory holds true.
Reference: “The lifespan of our universe” by Hoang Nhan Luu, Yu-Cheng Qiu and S.-H. Henry Tye, 18 September 2025, Journal of Cosmology and Astroparticle Physics. DOI: 10.1088/1475-7516/2025/09/055