Findings from the Dark Energy Spectroscopic Instrument (DESI) suggest that dark energy could be evolving over time. If they're right, cosmology will need a new model.
Astronomers studying the largest-ever map of the cosmos have found hints that our best understanding of the universe is due a major rewrite. The analysis, which looked at nearly 15 million galaxies and quasars spanning 11 billion years of cosmic time, found that dark energy — the presumed-to-be constant force driving the accelerating expansion of our universe — could be weakening. Or at least this is what the data, collected by the Dark Energy Spectroscopic Instrument (DESI), suggest when combined with information taken from star explosions, the cosmic microwave background and weak gravitational lensing. If the findings hold up, it means that one of the most mysterious forces controlling the fate of our universe is even weirder than first thought — and that something is very wrong with our current model of the cosmos. The researchers' findings were published in multiple papers on the preprint server arXiv and presented March 19 at the American Physical Society's Global Physics Summit in Anaheim, California, so they have not yet been peer-reviewed. "It's true that the DESI results alone are consistent with the simplest explanation for dark energy, which would be an unchanging cosmological constant," co-author David Schlegel , a DESI project scientist at the Lawrence Berkeley National Laboratory in California, told Live Science. "But we can't ignore other data that extend to both the earlier and later universe. Combining [DESI's results] with those other data is when it gets truly weird, and it appears that this dark energy must be 'dynamic,' meaning that it changes with time." The evolving cosmos Dark energy and dark matter are two of the universe's most puzzling components. Together they make up roughly 95% of the cosmos, but because they do not interact with light, they can't be detected directly. Yet these components are key ingredients in the reigning Lambda cold dark matter (Lambda-CDM) model of cosmology, which maps the growth of the cosmos and…