New data from prominent dark energy observatories indicates that the universe may not expand indefinitely as previously thought. A study led by physicist Henry Tye from Cornell University suggests that the cosmos could reach its maximum size in approximately 11 billion years and subsequently begin contracting, ultimately culminating in a “big crunch” around 20 billion years from now.
Tye, the Horace White Professor of Physics Emeritus, arrived at this conclusion by revising a longstanding model based on the “cosmological constant.” This concept, first introduced by Albert Einstein over a century ago, has been central to contemporary theories regarding the universe’s expansion and eventual fate. He notes that recent findings indicate a shift in understanding: rather than a positive cosmological constant leading to perpetual expansion, the data points toward a negative value that would trigger a dramatic reversal.
“For the last 20 years, people believed that the cosmological constant is positive, and the universe will expand forever,” Tye stated. “The new data seem to indicate that the cosmological constant is negative, and that the universe will end in a big crunch.” Tye’s research is detailed in the article titled “The Lifespan of our Universe,” published in the Journal of Cosmology and Astroparticle Physics.
Understanding the Shift from Expansion to Contraction
Currently, the universe is approximately 13.8 billion years old and continues to expand. Standard cosmology presents two scenarios for its future: if the cosmological constant remains positive, expansion will continue indefinitely. Conversely, if it is negative, the universe will eventually stop expanding, reach a maximum size, and then reverse direction, collapsing back to a singular point. Tye’s updated model strongly supports the latter scenario.
“This big crunch defines the end of the universe,” Tye emphasized. His calculations suggest that the collapse would occur in about 20 billion years, marking a significant moment in cosmic history.
Key evidence for this theory comes from recent findings by the Dark Energy Survey (DES) in Chile and the Dark Energy Spectroscopic Instrument (DESI) in Arizona. Tye highlighted that results from these two observatories, which operate in opposite hemispheres, have shown consistent results. Both projects aim to deepen understanding of dark energy, which constitutes roughly 68% of the universe’s mass and energy.
Their research seeks to determine whether dark energy is a constant property of space itself or influenced by other factors. The latest data suggest a more intricate picture, indicating that the universe is not solely dictated by a pure cosmological constant. Tye and his colleagues have proposed the existence of a hypothetical particle with an extremely low mass, which would have acted like a cosmological constant in the early universe but has evolved over time, leading to the current negative value.
“People have said before that if the cosmological constant is negative, then the universe will collapse eventually. That’s not new,” Tye remarked. “However, here the model tells you when the universe collapses and how it collapses.”
Future Research and Implications
As research continues, more data is expected to refine our understanding of dark energy. Hundreds of scientists are currently studying millions of galaxies to measure distances and improve estimates. The DESI project will keep gathering observations for another year, while other initiatives, such as the Zwicky Transient Facility in San Diego and the European Euclid space telescope, are also contributing to this critical field of study.
Tye expressed optimism about the ability of scientists to calculate the universe’s total lifespan in measurable terms. Understanding both its origins and its eventual demise provides valuable context for cosmologists exploring the full arc of cosmic history. “For any 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. 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.”
Tye’s co-authors on the study include his former doctoral students, Hoang Nhan Luu and Yu-Cheng Qiu, both from the Hong Kong University of Science and Technology. As ongoing research continues to unfold, the future of the universe remains a captivating topic at the intersection of science and existential inquiry.
