Light from Distant Galaxies Confirms General Theory of Relativity

The general theory of relativity, of Albert Einstein once again confirmed. The new data were obtained from a study of light from hundreds of thousands of distant galaxies. General relativity predicts that the wavelength of this light will be shifted by a small amount due to the galaxies’ mass, in an effect called gravitational redshift. The effect is very difficult to measure, because it is the smallest of the three types of redshift, with redshift also being caused by the movement of the galaxies and the expansion of the universe as a whole. To disentangle the three sources of redshift, the researchers relied on the vast number of galaxies in the Sloan Digital Sky Survey sample, which allowed them to perform a statistical analysis.

The amount of redshift they found that appeared to be caused by gravity agreed exactly with the predictions of general relativity. According to Radoslaw Wojtak, an astrophysicist at the University of Copenhagen they have independent measurements of the cluster masses, so they can calculate what the expectation for gravitational redshift based on general relativity is. It agrees exactly with the measurements of this effect. However, the findings still don’t disprove an alternative theory of gravity invented to undo the need for dark energy, which is thought to be causing the accelerated expansion of the universe.