DESI confirms Einstein's relativity on cosmic scales with unprecedented precision.

An international team of astronomers confirmed that Albert Einstein's theory of general relativity holds true on cosmic scales, following an extensive survey conducted by the Dark Energy Spectroscopic Instrument (DESI). The study analyzed nearly six million galaxies and quasars, spanning 11 billion years of cosmic history, offering new perspectives on the growth of cosmic structures, the mass of neutrinos, and the distribution of dark matter and energy.

Scientists used DESI, a state-of-the-art spectroscopic instrument installed on the Nicholas U. Mayall Telescope at Kitt Peak National Observatory in Arizona, to map how these galaxies cluster across time, aligning with Einstein's predictions and confirming general relativity on cosmic scales. This study represents the most accurate large-scale test of gravity in history, spanning most of the 13.8-billion-year history of the universe and strengthening the foundations of general relativity.

"General relativity has been very well tested at the scale of solar systems, but we also needed to test that our assumption works on much larger scales," said cosmologist Pauline Zarrouk from the French National Centre for Scientific Research, according to Science Alert. Zarrouk co-directed the new analysis alongside Héctor Gil Marín from the University of Barcelona.

The findings reveal that the way galaxies cluster and evolve over billions of years is consistent with Einstein's predictions, aligning with general relativity at cosmological scales. "Studying the speed at which galaxies formed allows us to directly test our theories, and so far, we are aligning with what general relativity predicts on cosmological scales," Zarrouk stated, as reported by Scienze Notizie.

The DESI collaboration involves more than 900 researchers from over 70 institutions worldwide and is managed by the U.S. Department of Energy's Lawrence Berkeley National Laboratory. DESI can capture light from 5,000 galaxies simultaneously and will eventually observe roughly 40 million galaxies and quasars, providing important contributions to the understanding of the universe over the last 11 billion years.

Space.com, New Scientits, and India Today were among the websites that reported on the study.

"Both our BAO results and the full-shape analysis are spectacular," said Professor Dragan Huterer of the University of Michigan, co-lead of DESI's group interpreting the cosmological data, according to Phys.org. "We're showing a tremendous new ability to probe modified gravity and improve constraints on models of dark energy. And it's only the tip of the iceberg."

The new analysis, called a "full-shape analysis," has expanded the possibilities of extracting information from the data, allowing the study of the distribution of galaxies and matter on different scales in space. This analysis has allowed researchers to explore up to 11 billion years into the past. Conducting this study required months of additional work and rigorous cross-checks.

Gravity plays a fundamental role in the functioning of the Universe, acting as the glue that holds cosmic structures together. The cosmic web, an intricate network of filaments and voids, represents the large-scale structure of matter formed by the gravitational pull of galaxies and dark matter. The way gravity clumps galaxies together along strands of the cosmic web against the outward pull of the expansion of the Universe is consistent with predictions made by Einstein's theory of general relativity.

"Einstein's theory of general relativity describes the motion of massive objects in a gravitational field that they create. It is one of the most successful physical theories that we have," said Huterer, as reported by Space.com.

The findings also place tighter constraints on alternative theories of modified gravity, which have been proposed to explain unexpected observations, including the accelerating expansion of the universe. These alternatives are generally referred to as "modified theories of gravity" and aim to explain observations of the universe without the need to introduce an unknown like dark energy.

"Our DESI data shows that it is in agreement with Einstein's theory of gravity but still favors a dynamical dark energy—and finding these simultaneously is new," noted Mustapha Ishak-Boushaki, an astrophysicist from the University of Texas at Dallas, according to New Scientist.

The study also provided new upper limits on the mass of neutrinos, the only fundamental particles whose masses have not yet been precisely measured in the laboratory. DESI's results indicate that the sum of the neutrino masses should be less than 0.071 eV/c², leaving a narrow window for neutrino masses.

"Remarkably, the galaxy clustering also sets upper limits on the yet unknown mass of tiny particles called neutrinos, as their presence affects the growth of structure," said Professor Ofer Lahav from UCL Physics & Astronomy, a DESI collaborator and a member of its Executive Committee, as reported by Mirage News.

Despite ongoing data collection, DESI has already achieved the most precise measurement of cosmic structure growth, focusing on how galaxies cluster and offering new insights into dark matter and dark energy. Further results from the second and third years of DESI operations are expected to be released in Spring 2025, with takeaways from the first three years of observations to be shared in March 2025.

"The idea that we can take pictures of the universe and tackle these big, fundamental questions is mind-blowing," said Mark Maus, a PhD student at Berkeley Lab and UC Berkeley, as reported by Space.com.

This article was written in collaboration with generative AI company Alchemiq