The DESI instrument observing the sky from the Nicholas U. Mayall Telescope during a meteor shower
KPNO/NOIRLab/NSF/AURA/R. the sparks
Albert Einstein’s theory of general relativity has been proven correct on the largest scale yet. Analysis of millions of galaxies shows that the way they have evolved and clustered over billions of years matches his predictions.
Ever since Einstein presented the theory of gravity more than a century ago, researchers have been trying to find scenarios where it doesn’t hold. But at the level of the greatest distances in the universe there was no such test until now, he says Mustapha Ishak-Boushaki at the University of Texas at Dallas. He and his colleagues used data from the Arizona Dark Energy Spectroscopic Instrument (DESI) to come up with one.
The details of the cosmic structure and how it has changed over time are a powerful test of our understanding of gravity, the force that formed galaxies as it evolved from small variations in the distribution of matter in the early universe.
DESI has so far collected data on how nearly 6 million galaxies formed over the past 11 billion years. Ishak-Boushaki and his colleagues combined results from several other large surveys, such as those that make maps. Cosmic microwave background radiation and supernovae. They then compared Einstein’s ideas and the modified theory of gravity with the predictions of the more contemporary competing theory of gravity. They found no deviation from Einstein’s gravity. Ishak-Boushaki says that while there are some uncertainties in the measurements, there is still no strong evidence that any theory that deviates from Einstein’s would more accurately capture the state of the universe.
Itamar Allali Meanwhile at Brown University in Rhode Island general relativity proven to hold up in very detailed laboratory tests, it is important to be able to test it at all scales, including the entire cosmos. This helps rule out the possibility that Einstein made correct predictions for objects of the same size but of different sizes, he says.
The new analysis also offers insights into how dark energyA mysterious force believed to be responsible for the accelerated expansion of the universe fits into our theories of gravity, he says Nathalie Palanque-Delabrouille at the Lawrence Berkeley National Laboratory in California. Einstein’s early formulations of general relativity included a cosmological constant – a type of anti-gravitational force that played the same role as dark energy – but previous DESI results have suggested that dark energy is not a constant. The universe may have changed as it aged, says Palanque-Delabrouille.
“Seeing agreement with general relativity and still seeing this departure from the cosmological constant opens a Pandora’s box of what the data can really say,” says Ishak-Boushaki.
DESI will continue collecting data for several years and will eventually record the positions and properties of 40 million galaxies, which the three scientists say will bring clarity to the proper marriage of general relativity and dark energy theory. This new analysis used only one year of DESI data, but in March 2025 the team will share the results of the instrument’s first three years of observations.
Allali says he anticipates these results will have implications in a number of important ways, such as defining change. Hubble constantwhich is a measure of the universe’s expansion rate, reduces the mass of elusive particles called neutrinos and also searches for new cosmic components. “dark radiation”.
“This analysis will weigh much more than gravity, it will affect all of cosmology,” he says.
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