Einstein Is Right Again – Gravity Has Not Changed Across The Universe

Researchers have conducted one of the most precise tests of Albert Einstein’s theory of General Relativity to date while looking at vast cosmic distances – and like all the tests before, the theory has passed it with flying colors. The current understanding of gravity, at the level of precision we have, seems to be the correct one. The test has important consequences for a major cosmological mystery: the nature of dark energy.

Over two decades ago, astronomers discovered that the universe is experiencing an accelerated expansion. The source of this acceleration remains unknown – the leading hypothesis is known as dark energy, an energy field across time and space that exerts a repulsive pressure like some sort of antigravity. We don’t have much solid evidence on what dark energy does, so alternative ideas put forward the view that maybe our theory of gravity is incomplete, and that gravity might be slightly different at larger scales.

The international Dark Energy Survey released a report examining distances of up to 5 billion light-years to study galaxies and determined the subtle distortions created by gravity as it warps space-time. This effect, called weak gravitational lensing, allowed the team to determine the strength of gravity in the past. As far as they can tell, they do not find any evidence of physics beyond our current model of the Universe.

While this is an important test, it is not the last word on the matter. It wouldn’t be science if it was. The European Space Agency will send a new observatory called Euclid to space in 2023 for a six-year mission. Euclid will push this analysis up to 8 billion light-years away. And by 2027, NASA will have the Nancy Grace Roman Space Telescope in space that will look at weak gravitational lensing even further, up to 11 billion light-years away.

“There is still room to challenge Einstein’s theory of gravity, as measurements get more and more precise,” co-author Agnès Ferté, who conducted the research as a postdoctoral researcher at JPL, said in a statement. “But we still have so much to do before we’re ready for Euclid and Roman. So it’s essential we continue to collaborate with scientists around the world on this problem as we’ve done with the Dark Energy Survey.”

There are a lot of uncertainties about the nature of dark energy and the equally mysterious dark matter. But for now, they continue to be the leading hypothesis.