Evrim Yazgin
Cosmos science journalist
Researchers have compiled a map of 6 million galaxies in the most precise test of how gravity works on large scales in the universe.
The survey, detailed in several pre-print papers on the arXiv server, uses data from the Dark Energy Spectroscopic Instrument (DESI). It tracks how gravitational forces have shaped the universe over the past 11 billion years.
Surprise, surprise they found that gravity behaves as Einstein predicted in his general theory of relativity.
The survey also limits possible theories of “modified gravity” which have been put forward as alternative ways of explaining observations such as the accelerating expansion of the universe attributed to the elusive dark energy.
“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,” says co-lead researcher Pauline Zarrouk, a cosmologist at the French National Center for Scientific Research (CNRS) working at the Laboratory of Nuclear and High-Energy Physics (LPNHE). “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.”
The results don’t fully close the door on potential outlier theories explaining the nature of the universe, though.
“The results from DESI, combined with datasets from other experiments, are consistent with general relativity theory operating at cosmic scales, although they do not completely exclude other theories of modified gravity,” says Mustapha Ishak-Boushaki, an astrophysicist at the University of Texas at Dallas.
The study also placed an upper limit on the mass of neutrinos. Neutrinos are the only fundamental particles whose masses have yet to be measured.
DESI is in its 4th of 5 years of surveying the sky. Its researchers plan to collect data from about 40 million galaxies and quasars by the time the project ends.
