Dark Energy Spectroscopic Instrument (DESI) is an advanced instrument that simultaneously captures light from 5,000 galaxies. In a new study, the data from DESI found that gravity behaves as predicted by Einstein’s theory of general relativity.
The result supports our current universe model and constrains alternative modified gravity theories. These theories were proposed to explain phenomena like the universe’s accelerating expansion, which is usually attributed to dark energy.
Gravity—which shapes our universe—significantly impacts the amount of matter present in it. This new study, which uses data from the DESI, traced how this cosmic structure grew over the past 11 billion years, providing the most precise test to date of gravity at very large scales.
General relativity has been thoroughly tested within solar systems, but testing its validity on much larger scales was also important. By studying the rate of galaxy formation, we can directly test our theories. So far, the results align with the predictions made by general relativity at cosmological scales.
The study also set new upper limits on the mass of neutrinos, the only fundamental particles with uncertain masses. Previous experiments suggested that the combined mass of all three types of neutrinos is at least 0.059 eV/c² (compared to the electron’s mass of about 511,000 eV/c²). DESI’s findings indicate that the total mass is less than 0.071 eV/c², providing a narrow range for the neutrino masses.
The DESI collaboration released several papers detailing their results from nearly 6 million galaxies and quasars, allowing researchers to look up to 11 billion years into the past. With just one year of data, DESI has made the most precise measurement of cosmic structure growth, surpassing previous efforts that took decades.
This new analysis expands on earlier findings from April, which revealed the most extensive 3D map of the universe and suggested that dark energy might be evolving. The latest “full-shape analysis” dives deeper, measuring the distribution of galaxies and matter on various scales.
This study involved months of work and cross-checking, using a technique to prevent bias by concealing results from scientists until the analysis was complete.
Dragan Huterer, professor at the University of Michigan and co-lead of DESI’s group interpreting the cosmological data, said, “Both our BAO results and the full-shape analysis are spectacular. This is the first time that DESI has looked at the growth of cosmic structure. We’re showing a tremendous new ability to probe modified gravity and improve constraints on dark energy models. And it’s only the tip of the iceberg.”
Mark Maus, a PhD student at Berkeley Lab and UC Berkeley who worked on theory and validation modeling pipelines for the new analysis, said, “Dark matter makes up about a quarter of the universe, and dark energy makes up another 70 percent, and we don’t know what either one is. The idea of taking pictures of the universe and tackling these big, fundamental questions is mind-blowing.”
