New Data Support Einstein on Accelerating Universe - Science News
Einstein is still the boss, say researchers with the BOSS project for measuring key properties of the universe.
BOSS, for Baryon Oscillation Spectroscopic Survey, has measured the distance to faraway galaxies more precisely than ever before, mapping the universe as it existed roughly 6 billion years ago, when it was only 63 percent of its current size. The findings suggest that the mysterious “dark energy” causing the universe to expand at an accelerating rate was foreseen by Einstein, the researchers reported April 1 at the American Physical Society meeting.
To keep the universe in a static state, Einstein added a term called the “cosmological constant” to the equations for his theory of general relativity; when the universe was later found to be expanding, he called the constant his “biggest blunder.” But in recent years, the cosmological constant, which describes a repulsive force occupying all of space, has been invoked to explain the discovery, first reported in 1998, that the universe is expanding faster and faster.
Evidence for accelerated expansion could be explained either by the negative pressure exerted by the cosmological constant (or some other form of dark energy) or by some flaw in general relativity. The BOSS results support the dark energy picture. “We find no deviations from general relativity on these very large scales,” said Nikhil Padmanabhan, a physicist at Yale University who presented the results and is a coauthor on a series of papers posted online at arxiv.org.
BOSS, a part of the third Sloan Digital Sky Survey, will operate through 2014. Its current results are for about a quarter million galaxies. The key to the measurements are an imprint of sound waves — called baryon acoustic oscillations — frozen into the radiation from 300,000 years after the Big Bang, which occurred 13.7 billion years ago. These sound waves caused regularly spaced bumps in the distribution of galaxies throughout the cosmos, and so can serve as a sort of space ruler.