![]() They observed how this elemental force drives galaxies to clump into larger collections of themselves and how it shapes the expansion of the universe. The Princeton scientists studied the effects of gravity on these objects over long periods of time. The team used data from the Sloan Digital Sky Survey, a long-term, multi-institution telescope project mapping the sky to determine the position and brightness of several hundred million celestial objects.īy calculating the clustering of these galaxies, which stretch nearly one-third of the way to the edge of the universe, and analyzing their velocities and distortion from intervening material, the researchers have shown that Einstein's theory explains the nearby universe better than alternative theories of gravity. "We knew we needed to look at the large-scale structure of the universe and the growth of smaller structures composing it over time to find out," Reyes said. But because these theories were designed to match the predictions of general relativity about the expansion history of the universe, a factor that is central to current cosmological work, it has become crucial to know which theory is correct, or at least represents reality as best as can be approximated. These modified theories of gravity depart from general relativity on large scales to circumvent the need for dark energy, an elusive force that must exist if the calculations of general relativity balance out. In recent years, several alternatives to general relativity have been proposed. For scientists, the theory provides a basis for their understanding of the universe and the foundation for modern research in cosmology. Clocks located a distance from a large gravitational source will run faster than clocks positioned more closely to that source, Einstein said. Shockingly, the flow of time, Einstein said, could be affected by the force of gravity. The groundbreaking theory showed that gravity can affect space and time, a key to understanding basic forces of physics and natural phenomena, including the origin of the universe. It redefined humanity's understanding of the fabric of existence - gravity, space and time - and ultimately explained everything from black holes to the Big Bang. "It adds another brick to the foundation that underlies what we do."įirst published in 1915, Einstein's general theory of relativity remains a pivotal breakthrough in modern physics. "All of our ideas in astronomy are based on this really enormous extrapolation, so anything we can do to see whether this is right or not on these scales is just enormously important," Gunn said. ![]() The results are important, they said, because they shore up current theories explaining the shape and direction of the universe, including ideas about "dark energy," and dispel some hints from other recent experiments that general relativity may be wrong. Other scientists collaborating on the paper include Tobias Baldauf, Lucas Lombriser and Robert Smith of the University of Zurich and Uros Seljak of the University of California-Berkeley. Reinabelle Reyes, a Princeton graduate student in the Department of Astrophysical Sciences, along with co-authors Rachel Mandelbaum, an associate research scholar, and James Gunn, the Eugene Higgins Professor of Astronomy, outlined their assessment in the March 11 edition of Nature.
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