The force of gravity has shaped the universe. The character of the pull has transformed the tiny differences in the amount of matter in the early universe into the vast filaments of galaxies that can be observed today. A new study using data from the Dark Energy Spectroscopic Instrument (DESI) has mapped the growth of these structures over the past eleven billion years, and has produced the most accurate large-scale test of the force of gravity in history.
DESI is an international collaboration of more than 900 scientists from over 70 institutions around the world, managed by the US Department of Energy's Lawrence Berkeley National Laboratory (Berkeley Lab). In this new study, scientists have found that gravity behaves as predicted by Einstein's theory of general relativity. These results confirm the current model of the universe and narrow down possible theories of modified gravity, which had been proposed as alternative explanations for unexpected observations, such as the accelerating expansion of the universe, which is usually attributed to dark energy.
Limits to Einstein's theory of gravitation
The researcher Héctor Gil Marín, from the Faculty of Physics and the Institute of Cosmos Sciences of the University of Barcelona (ICCUB), has co-led this new analysis and comments that "these data allow us to study how quickly the largest structures in the cosmos have formed, to put limits to Einstein's theory of gravitation on cosmological scales much larger than those of the solar system". The researcher, who is also a member of the Institute for Space Studies of Catalonia (IEEC), adds that "the results, for now, fit perfectly with the predictions of Einstein's theory of general relativity".
The study also provides a new upper limit on the mass of neutrinos, whose only elementary particles have not yet had their masses measured. Previous experiments revealed that the sum of the masses of the three types of neutrinos should be at least 0.059 eV/c2 (for comparison, that of the electron is 511 000 eV/c2). The DESI results indicate that this sum should be less than 0.071 eV/c2, which leaves a very narrow window for the possible values of the neutrino masses.
