A new study has bolstered the discovery that dark energy, a mysterious force driving galaxy acceleration, has weakened over time. The findings, based on three years of data from the Dark Energy Spectroscopic Instrument (DESI) collaboration, suggest that dark energy’s energy density has decreased by 10% in the past 4.5 billion years.
The study challenges the long-held assumption that dark energy is an inherent property of empty space, unchanging over time. Cosmologists must now explain this shift, potentially revising their “standard model” for the universe’s history.
Researchers used DESI to map the universe’s expansion history, tracking variations in galaxy density and baryon acoustic oscillations (BAOs) left over from the early universe. These findings imply that the cosmic expansion is accelerating less now than it was in the past, contradicting the assumption of a constant dark energy.
The discovery has significant implications for our understanding of the universe’s evolution and the nature of dark energy.
Source: https://www.nature.com/articles/d41586-025-00837-2