Einstein has been proven right in spectacular style.
Scientists have conducted a precise test of the way gravity works outside our solar system.
It marks the first time that Einstein's general theory of relativity has been tested at such a large scale.
The general theory of relativity, also known as GR, was first proposed in 1915. But its implications are huge, and therefore have never been tested fully.
Despite that, scientists rely on it to explain the strange behaviour of our universe. The new study shows that they haven't been wrong to do so.
For instance, scientists have known since 1929 that the universe is expanding, but in 1998 found that the expansion had sped up and was going more quickly than it did in the past. That can only make sense if the universe is filled with a mysterious substance called dark energy – but that in turn relies on GR being correct at the scale of galaxies.
As such, our very understanding of the universe relies on GR being correct.
To check that, a team of astronomers looked deep into space, using a nearby galaxy as a gravitational lens. That allowed them to test gravity at the astronomical scale.
"General Relativity predicts that massive objects deform space-time, this means that when light passes near another galaxy the light's path is deflected," said Thomas Collett of the Institute of Cosmology and Gravitation at the University of Portsmouth, who led the study. "If two galaxies are aligned along our line of sight this can give rise to a phenomenon, called strong gravitational lensing, where we see multiple images of the background galaxy.
"If we know the mass of the foreground galaxy, then the amount of separation between the multiple images tells us if General Relativity is the correct theory of gravity on galactic scales."
