Recent research suggests that the universe’s expansion may be slowing down, which goes against the common belief that dark energy is making it speed up. Since the discovery of dark energy almost 30 years ago, this research could lead to a major change in the way we think about cosmology.
Overview of New Findings
South Korea’s Yonsei University, led by Professor Young-Wook Lee, has discovered evidence against the speeded-up expansion of universe and a colder cosmos. The new result comes from a re-analysis of distances to faraway galaxies, and it raises the possibility that earlier estimates may have been influenced by something not currently identified. What their work suggests is that dark energy — the mysterious force which scientists suspect is causing the universe to expand at an ever-faster rate — might diminish and change over time much more quickly than had been thought.
Background and Implications
For the past couple of decades cosmologists have thought that the expansion of the universe has been thrust from slowing to accelerating 4.8 billion years ago or so. It was this acceleration that the dark energy, proposed to form about 68% of the cosmos, was postulated to resemble a kind of anti-gravity pushing galaxies apart at an increasing rate with time. The 2011 Nobel Prize awarded for this discovery was based on the observational evidence of type Ia supernovae supporting that accelerated expansion. But the new results imply that this may no longer be so, or at least not since 1.5bn years ago, and if that were the case, it could mean that we need to rethink not just dark energy but our own theories of gravity more generally.
Scientific Impact
If true, these results could transform current models of cosmology. The standard model of cosmology, ΛCDM which is based on constant acceleration provided by a dark energy-like term with negative pressure, does no longer account for everything that happens in the universe. Instead, researchers could have to consider changing dark energy or other forces influencing cosmic expansion. In addition, this work could provide a solution to the “Hubble tension,” a discrepancy between different measurements related to the rate at which the universe is expanding.
Future Directions
Now that they are here, astronomers and physicists will be concentrating on further observations and experiments to verify these results. Better measurements of supernovae, the cosmic microwave background and galaxy distributions are key. The possible slowdown of the universe raises new questions about its ultimate fate, including whether it might eventually re-collapse into what cosmologists call a “big crunch.”
This growing understanding shows that cosmological research is always changing and moving forward. It also reminds us that basic questions about the universe’s expansion and the strange dark energy are still hotly debated and very complicated.