The universe is approaching the midpoint of its 33-billion-year lifespan, a Cornell physicist calculates with new data from dark-energy observatories. After expanding to its peak size about 11 billion years from now, it will begin to contract – snapping back like a rubber band to a single point at the end.

Henry Tye, the Horace White Professor of Physics Emeritus in the College of Arts and Sciences, reached this conclusion after adding new data to a model involving the “cosmological constant” – a factor introduced more than a century ago by Albert Einstein and used by cosmologists in recent years to predict the future of our universe.

“For the last 20 years, people believed that the cosmological constant is positive, and the universe will expand forever,” Tye said. “The new data seem to indicate that the cosmological constant is negative, and that the universe will end in a big crunch.”