In his theory of relativity, Albert Einstein explained how the laws of physics differ from our everyday expectations when you consider extreme speed or immense gravity. One prediction of this theory is time dilation: if an object is moving very quickly relative to us, its actions will appear to unfold in slow motion. Astronomers think that the universe is expanding, which means that distant galaxies are moving away from us at high speeds. We therefore expect these galaxies to experience time dilation. While very distant galaxies are generally too faint to be observed with a telescope, we can study them using quasars. Quasars are extremely bright objects at the heart of some galaxies, caused by material falling onto a supermassive black hole at the galaxy’s center.

While time dilation has been detected in other astronomical objects, the effect has not been found in previous studies of quasars. This discrepancy has caused scientists to speculate that something may be wrong with our understanding of either quasars or the structure of the universe. However, these complaints appear to have been premature. A recent study looked at 190 quasars that were monitored over 20 years and successfully detected time dilation. The authors of the study suggest that previous investigations failed to find the signal because their samples were much smaller, preventing a robust statistical analysis.

While time dilation and other predictions of relativity may seem bizarre, studies like this one reinforce that Einstein was right about this fundamental law of physics. However, testing these predictions is still important: just as Einstein realized that classical physics was not the complete picture, future studies may reveal that relativity is just one piece of a larger puzzle.

This study was performed by Geraint F. Lewis, a professor in the Sydney Institute for Astronomy at the University of Sydney and Brendon J. Brewer, a senior lecturer in the Department of Statistics at the University of Auckland.

Managing Correspondent: Emily Pass

Press Article: Astronomers observe time dilation in early universe (The Guardian)

Original Journal Article: Detection of the cosmological time dilation of high-redshift quasars (Nature Astronomy)

Image Credit: NASA, ESA and J. Olmsted (STScI)