Data tests Einstein’s famous theory of General Relativity

Galaxy mapping data also test how gravity behaves at cosmic scales.

Mapping galaxies

Scientists, including astrophysicists from the University of Edinburgh, used the Dark Energy Spectroscopic Instrument (DESI) to map how nearly six million galaxies cluster across up to 11 billion years of time.

Their complex analysis of DESI’s first year of data provides one of the most stringent tests yet of Einstein’s famous theory of General Relativity and how gravity behaves at cosmic scales.

Looking at galaxies and how they cluster throughout time reveals how the universe’s structure has grown. This allowed DESI’s scientists to test theories of modified gravity – an alternative explanation for our universe’s accelerating expansion typically attributed to dark energy.

They found that the way galaxies cluster is consistent with our standard model of gravity and the predictions made by Einstein.

The result validates the leading model of the universe and limits possible theories of modified gravity, which have been proposed as alternative ways to explain unexpected observations such as the expansion of the universe.

Dr Samuel Brieden, Postdoctoral Research Associate in Observational Cosmology, Institute for Astronomy, University of Edinburgh, said:

The tests used a technique to hide the results from the scientists until the analysis pipeline was frozen, mitigating any unconscious bias. Seeing the final, ‘unblinded’ results was exhilarating. It felt like years of research culminating into that single moment.

Neutrino influence

A further insight DESI has revealed is on the mystery of neutrino mass. Neutrinos are elementary particles with very small masses, but the force of gravity they collectively produce affects how galaxies move and cluster in space. The DESI dataset has made it possible to detect the effect of neutrinos, which is exciting for both cosmologists and particle physicists.

About DESI

DESI can capture light from 5,000 galaxies simultaneously. It sits atop the US National Science Foundation’s Nicholas U Mayall 4-metre Telescope at Kitt Peak National Observatory, in Arizona, USA.

DESI is managed by the US Department of Energy’s Lawrence Berkeley National Laboratory (Berkeley Lab). UK involvement in DESI includes Durham University, University College London and the University of Portsmouth as full member institutions, together with individual researchers at the universities of Cambridge, Edinburgh, St Andrews, Sussex and Warwick. 

The experiment is now in its fourth of five years surveying the sky and plans to collect data on roughly 40 million galaxies and quasars by the time the project ends.

Edinburgh involvement

While mostly members of the research group led by Professor Florian Beutler (including Dr Samuel Brieden, Dr Richard Neveux, and Dr Mike Shengbo Wang) actively contributed to the study released today, also the groups led by Dr Yan-Chuan Cai, Professor Sergei Koposov, Professor John Peacock, and Professor Alkistis Pourtsidou are deeply involved in the DESI collaboration in various aspects, from investigating the structure of the Milky Way up to testing cosmological models on the largest scales.