More than a century after Albert Einstein introduced his groundbreaking theories, scientists continue to challenge and scrutinize his work, seeking cracks that could advance their understanding of physics.
But that’s easier said than done.
Raising the bar. A recent large-scale experiment has once again affirmed the validity of Einstein’s theories—this time across billions of galaxies.
DESI. The Dark Energy Spectroscopic Instrument (DESI) project conducted this latest experiment. DESI, a collaboration involving over 900 researchers from 70 institutions, has been mapping the motion of galaxies across the observable universe.
To date, DESI has studied 6 million galaxies, spanning motions from 11 billion years ago to those of nearby galaxies. By the project’s completion, it aims to map 40 million galaxies, offering an unprecedented view of the universe’s structure.
Revalidating Einstein. However, the analysis of these first observations has already yielded results.
The experiment compared the motion of these galaxies with predictions derived from various models of gravity, including Einstein’s theory of general relativity and alternative models like modified gravity. The result: Einstein’s predictions aligned most closely with the observed data.
“General relativity has been very well tested at the scale of solar systems, but we also needed to test that our assumption works at much larger scales,” Pauline Zarrouk, a cosmologist at the French National Center for Scientific Research, said. “Studying the rate at which galaxies formed lets us directly test our theories and, so far, we’re lining up with what general relativity predicts at cosmological scales.”
Universality of Einstein’s laws. Einstein’s theory of relativity has been validated repeatedly using numerous methods, from laboratory experiments to stellar observations. However, testing its universality requires extending the theory to extreme scales, such as the vastness of the universe. DESI’s results bolster the theory’s robustness on a cosmological scale, further cementing its place as a cornerstone of modern physics.
The neutrino problem. Beyond testing gravity, DESI’s work also sheds light on fundamental particle physics. Researchers used DESI data to refine estimates of neutrino masses, subatomic particles whose properties remain elusive.
Previous limits suggested the total mass of all three types of neutrinos must exceed 0.059 electron volts (eV/c²). DESI’s findings now cap the maximum sum at 0.071 eV/c², narrowing the range and providing vital insights for future studies.
The project has a catalog of publications describing the methods and results of its experiments.
Looking ahead. Although DESI’s results are groundbreaking, the project is far from finished. DESI plans to release even more comprehensive results in March 2025, promising deeper insights into both the cosmos and the fundamental particles that compose it.
Image | KPNO/NOIRLab/NSF/AURA/R. Sparks
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