Clumped Galaxies Test General Relativity: Einstein's Theory Passes

It turns out that the theory of General Relativity may have encountered its toughest test yet--and passed. The most precise measurements to date of the strength of gravitational interactions between distant galaxies have shown perfect consistency with General Relativity's predictions.

The theory of General Relativity was first published by Albert Einstein in 1916. Since then, researchers have continued to uncover evidence that supports this theory.

"Gravity is the main driving force behind the growth of structure in the universe," said Lado Samushia, one of the researchers, in a news release. "According to General Relativity, gravity is a manifestation of the space-time curvature-massive objects curve the space-time around them, which affects the movement of other objects around them. It's a very elegant theory that has been successful in explaining the outcomes of many experiments, however it is not the only theory of gravity."

In fact, theoretical physicists have proposed many other theories and modifications to General Relativity. This means that researchers have continually sought examples in order to find out what the truth of the matter might be.

In this case, the scientists analyzed more than 600,000 galaxies from the Sloan Digital Sky Survey III Baryon Oscillations Spectroscopic Survey catalogue in order to create a measurement of how much galaxies clump together within the space that they occupy. More specifically, they used observed distortions in galaxy positions. This allowed them to measure the strength of gravity with a precision of six percent, the strongest constraint of its kind as of today. These measurements actually turned out to be perfect consistent with General Relativity.

"Whilst the Cosmological Principle tells us that the universe should have the same properties in every direction, observations do not match this picture," said Samushia. "Because galaxies are themselves parts of larger structures that are growing, they tend to 'infall' towards each other. This infall gives an apparent effect that we only see in the direction towards us, because of the way in which we observe the galaxies."

The findings are published in the journal Monthly Notices of the Astronomical Society.