New findings suggest dark energy could be weakening, potentially reshaping our understanding of the universe’s expansion and challenging long-held cosmological theories.
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| DESI’s new findings indicate that dark energy may not be constant, challenging the standard model of cosmology and raising questions about the universe’s future. Image: NASA |
Tucson, Arizona, USA — March 21, 2025:
Recent revelations from the Dark Energy Spectroscopic Instrument (DESI) have thrown a wrench into the long-standing cosmological model, suggesting that dark energy—long considered the steady force behind the accelerated expansion of the universe—might be weakening. If these findings hold, the implications could be far-reaching, forcing scientists to reconsider how they view the universe’s structure and ultimate fate.
For over a century, scientists have known that the universe is expanding. The observation of distant galaxies moving away from each other gave birth to the understanding that space itself was stretching. In the late 1990s, however, this theory was upended by the discovery that the expansion was not slowing down, as previously assumed, but was accelerating. This acceleration was attributed to dark energy, a mysterious force believed to counteract gravity and push the universe apart.
Until now, dark energy was assumed to be constant—a fundamental feature of the universe. This assumption is deeply ingrained in the standard cosmological model, which was first influenced by Albert Einstein’s theory of relativity. According to this model, dark energy makes up about 70% of the universe, with dark matter contributing 25% and ordinary matter, the matter we interact with daily, comprising just 5%.
But new observations from DESI, based at the Kitt Peak National Observatory in Arizona, suggest that dark energy may be evolving over time. The instrument, which uses advanced optical fibers to simultaneously observe thousands of galaxies and quasars, has provided fresh data that could shake the foundations of cosmology.
Alexie Leauthaud-Harnett, a spokesperson for the DESI collaboration, explained that the team's findings are “deeply intriguing,” hinting at a possible shift in our understanding of dark energy. “It is exciting to think that we may be on the cusp of a major discovery about dark energy and the fundamental nature of our universe,” she said in a statement.
Arnaud de Mattia, a French physicist involved with the data analysis, noted that the new observations show “signs that the impact of dark energy may be weakening over time.” This hypothesis points to the possibility that dark energy's influence on the universe’s expansion may have been stronger in the past, particularly around seven billion years ago, when the expansion was accelerating at an even faster rate.
This potential change in dark energy would represent a dramatic shift in our cosmological models, which have long held that dark energy is constant. If it is weakening, scientists would have to reconsider the assumptions that have shaped their understanding of the universe’s behavior. The question now is: how do these findings fit into the bigger picture?
The implications of a weakening dark energy force are profound. If dark energy is not constant, the future of the universe could be very different from what cosmologists have predicted. For instance, it could mean that the universe’s expansion may slow down, halt, or even reverse—leading to the possibility of a “Big Crunch,” where the universe collapses back in on itself. Conversely, some scientists argue that this weakening might allow for the possibility of a steady-state universe, where expansion slows but does not stop.
However, despite the tantalizing evidence from DESI, there is still considerable uncertainty. Many researchers, including Etienne Burtin, another physicist involved in the study, remain cautious. Burtin believes that “within five years, we should have a clearer picture,” as more data from DESI and other observatories—including NASA's upcoming Nancy Grace Roman space telescope and the European Space Agency's Euclid mission—becomes available.
Joshua Frieman, a dark energy expert at the University of Chicago, also remains optimistic. “This new generation of surveys will nail this,” he said, referring to upcoming missions that promise to refine our understanding of dark energy.
Yet, despite this optimism, some scientists have voiced concerns about the current direction. Diplomatic tensions are already emerging, as new theories clash with older models that have been accepted for decades. The debate over dark energy's role is heating up, with some experts calling for a fundamental reassessment of current theories, while others insist that further evidence is needed to confirm the weakening hypothesis.
As research continues, the DESI data has already spurred a major shift in the conversation surrounding dark energy. Whether or not the hypothesis that dark energy is weakening proves true, the ongoing studies will likely lead to breakthroughs that redefine cosmology and our understanding of the universe. What is clear is that we are at a crucial crossroads in the study of space and time, one that could reshape our fundamental understanding of the universe for generations to come.