13 Billion Light-Years Away, Einstein’s Theory of General Relativity Still Holds True

May 11, 2016 | Joanne Kennell

Exploding asteroids

His “biggest blunder” may have been right afterall.

It was discovered in the late 1990s that the universe is expanding at an accelerated rate. However, scientists are not still not sure what’s causing it. Is it the mysterious and elusive dark energy? Or it is due to Einstein’s theory of relativity, which states that gravity warps space and time, breaking down?

General relativity predicted that the universe must either expand or contract, but Einstein thought the universe was static, so he proposed a term to stop the expansion — the cosmological constant — which acts to counteract the gravitational pull of matter. However, when Hubble uncovered that the universe was actually expanding, Einstein regretted modifying his theory and viewed the cosmological constant as the “biggest blunder” of his life.

But some astronomers want to revive the cosmological constant because it ties together theory and observation. For example, by attempting to measure how much the expansion of the universe has changed over billions of years, scientists have suggested that the universe contains a bizarre form of energy, known as dark energy — a theoretical repulsive force that functions as an anti-gravity.

Sounds familiar, right? The cosmological constant is an example of this type of energy.

A recent study published online in the Publications of the Astronomical Society of Japan, and led by Japanese researchers, tested Einstein’s theory by using FastSound Survey data on more than 3,000 distant galaxies to analyze their velocities and clustering. By generating a map of these galaxies (as seen in the image below), which are located around 13 billion light-years from Earth, the international team found that Einstein’s general theory of relativity doesn’t break down. In fact, it is still valid far into the universe.

3D map of the universe

A 3D map of the universe spanning 12 to 14.5 billion light-years. Photo credit: NAOJ; Partial data supplied by: CFHT, SDSS

This supports that the expansion of the universe could be explained by a cosmological constant, just like Einstein proposed.

"We tested the theory of general relativity further than anyone else ever has. It's a privilege to be able to publish our results 100 years after Einstein proposed his theory," said Okumura in a press release.

Previously, no one had been able to analyze galaxies more than 10 billion light-years away, but thanks to the Fiber Multi-Object Spectrograph (FMOS) on the Subaru Telescope, which can study galaxies between 12.4 and 14.7 billion light-years away, the team finally could.

"Having started this project 12 years ago it gives me great pleasure to finally see this result come out," Karl Glazebrook, Professor at Swinburne University of Technology, who proposed the survey, said in the release.

The researchers plan to use the Prime Focus Spectrograph, which is currently under construction and expected to be able to study galaxies even further away, to determine if Einstein’s theory still holds.

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