spacetoday.net: Research challenges dark energy, cosmological constant

Posted: Thu, Jan 12, 2006, 6:05 AM ET (1105 GMT)
A new study suggests that "dark energy", the mysterious energy that is causing the expansion of the universe to accelerate, may have been less powerful earlier in the history of the universe, a discovery that could challenge the existence of Einstein's cosmological constant. LSU astronomer Bradley Schaefer presented research at the American Astronomical Society conference this week using gamma-ray bursts to measure the expansion of the universe. He found that the effect of dark energy declined the further back into the universe's history he probed, and may have actually been attractive, rather than repulsive, at some point. The discovery challenges the cosmological constant, a factor originally introduced by Einstein to keep the universe static, but invoked more recently by astronomers to explain why the expansion of the universe is accelerating, based on observations of distant supernovae. Many astronomers said it was too early to gauge the accuracy of the new gamma-ray burst observations and their effect on dark energy.