Recent findings from prominent dark-energy observatories indicate that the universe may not expand indefinitely as previously thought. A physicist from Cornell University, Henry Tye, has calculated that the cosmos could reach its maximum size in approximately 11 billion years before undergoing a dramatic reversal, ultimately collapsing in a scenario referred to as a “big crunch” around 20 billion years from now.
This research, published in the Journal of Cosmology and Astroparticle Physics, suggests that the universe, currently estimated to be 13.8 billion years old, is moving toward the halfway point of a total lifespan of about 33 billion years. Tye’s updated model relies on the “cosmological constant,” a concept introduced by Albert Einstein more than a century ago, which has been pivotal in modern cosmology.
Tye explains, “For the last 20 years, people believed that the cosmological constant is positive, and the universe will expand forever. The new data seem to indicate that the cosmological constant is negative, and that the universe will end in a big crunch.” This perspective challenges long-held assumptions about the fate of the universe.
Understanding the Big Crunch Versus Endless Expansion
Current cosmological theories outline two primary outcomes for the universe’s future. If the cosmological constant remains positive, the universe will continue expanding indefinitely. Conversely, if it is negative, as Tye’s findings suggest, the universe will eventually cease expanding, reach its largest size, and then contract until everything collapses into a singular point.
Tye emphasizes that this “big crunch” would represent the universe’s definitive end, with projections indicating that such a collapse would occur in about 20 billion years.
Insights from Dark Energy Observations
Key evidence supporting these conclusions stems from recent observations by the Dark Energy Survey (DES) in Chile and the Dark Energy Spectroscopic Instrument (DESI) in Arizona. According to Tye, data from these observatories, which operate in separate hemispheres, closely align, lending credibility to the findings. Both initiatives aim to deepen the understanding of dark energy, which constitutes approximately 68% of the universe’s mass and energy.
These studies challenge the notion that dark energy is merely a constant feature of space. Instead, the data suggest a more intricate scenario, potentially involving additional factors influencing dark energy’s behavior. To explain this, Tye and his team propose a theoretical particle with extremely low mass, which would have acted like a cosmological constant in the early universe but whose effects have evolved over time. This adjustment aligns with the latest observations and indicates a shift towards a negative cosmological constant.
Tye clarifies, “People have said before that if the cosmological constant is negative, then the universe will collapse eventually. That’s not new. However, here the model tells you when the universe collapses and how it collapses.”
The Ongoing Search for Cosmic Understanding
The pursuit of knowledge about dark energy is far from over. Hundreds of researchers are currently analyzing millions of galaxies and measuring intergalactic distances to refine existing estimates of dark energy. The DESI project will continue its observations for another year, while other initiatives, 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, are either contributing or preparing to begin their own investigations.
Tye expresses optimism regarding the ability to calculate the universe’s total lifespan. He notes that understanding both its origin and eventual conclusion is crucial for cosmologists. “For any life, you want to know how life begins and how life ends — the endpoints,” he states. “For our universe, it’s also interesting to know, does it have a beginning? In the 1960s, we learned that it has a beginning. Then the next question is, ‘Does it have an end?’ For many years, many people thought it would just go on forever. It’s good to know that, if the data holds up, the universe will have an end.”
The implications of Tye’s research not only reshape our understanding of the cosmos but also invite further exploration into the fundamental nature of dark energy and the ultimate fate of the universe.
