Universe Expansion May Be Slowing, Not Accelerating, Study Suggests (theguardian.com) 17
A new study challenges the Nobel-winning theory that the universe's expansion is accelerating, suggesting instead that it may be slowing down as dark energy weakens -- potentially leading to a future "big crunch" where the cosmos collapses back in on itself. "Our study shows that the universe has already entered a phase of decelerated expansion at the present epoch and that dark energy evolves with time much more rapidly than previously thought," said Prof Young-Wook Lee, of Yonsei University in South Korea, who led the work. "If these results are confirmed, it would mark a major paradigm shift in cosmology since the discovery of dark energy 27 years ago." The Guardian reports: The latest work focuses on the reliability of observations of distant supernovae (exploding stars) that led to the discovery of dark energy, work that was awarded the 2011 Nobel prize in physics. [...] By estimating the ages of 300 host galaxies using a different method, the team concluded that there are simply variations in the properties of stars in the early universe that mean they produce, on average, fainter supernovae. Correcting for this systematic bias still results in an expanding universe, but suggests that the expansion has slowed down and that dark energy is waning, the analysis concluded. If dark energy keeps decreasing to the point where it becomes negative, the universe is theoretically predicted to end in a big crunch. The findings are published in Monthly Notices of the Royal Astronomical Society.
