DESI's 3D map of the universe can show how dark energy may have evolved over time. Earth is at the center in this animation, and every dot is a galaxy.

At a beachfront convention center in Cancún, Mexico, last December, Seshadri Nadathur presented a confidential growth chart of the universe. Seated in the audience, hundreds of his fellow scientists silently processed that the cosmic chronicle as they had come to know it may need revising. "It's the most exciting thing that's happened in cosmology in 25 years," says Nadathur, a cosmologist at the University of Portsmouth in England.

For almost three decades, astronomers have believed that the universe is expanding faster and faster and that the acceleration of this growth is constant over time—driven by a mysterious force they call "dark energy." Last April a survey by the Dark Energy Spectroscopic Instrument (DESI) published hints that dark energy may not be as constant as they'd assumed, adding to a pile of concerns that are already threatening the standard model of cosmology. Today Nadathur and his DESI collaborators unveiled their follow-up results publicly at the American Physical Society's Global Physics Summit and in multiple preprint papers, further validating the omen.

After nearly tripling the researchers' collection of galaxy coordinates, the new DESI analysis provides the strongest evidence yet that the rate of cosmic expansion fluctuates—finally shedding some light on dark energy, which scientists think constitutes about 70 percent of everything in the universe.

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