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Astronomers Measure the Deceleration of the Universe before Dark Energy

Young Universe Expanded Slowly During Last 14 Billion Years, Expansion Slowed and then Sped Up


Astrophysicist Kyle Dawson stands in front of the 2.5-meter Sloan Telescope at Apache Point Observatory in New Mexico. Photo Credit: Dan Long, Apache Point Observatory

Nov. 12, 2012 – Like a roller coaster that crawls slowly uphill and then zooms downhill, the universe expanded at a much slower rate 11 billion years ago than it has during the past 5 billion years, says a new study co-authored by Kyle Dawson, a University of Utah astrophysicist.

Light from 60,000 super-bright objects known as quasars served as flashlights to illuminate hydrogen gas between Earth and objects in the distant, early universe.

“We reconstructed a 3-D map of the hydrogen gas, and from the map, we learned about the processes by which the universe expanded and grew in the first 3 billion years,” says Dawson, an assistant professor of physics and astronomy at the University of Utah and a member of the third Sloan Digital Sky Survey, or SDSS-III, which conducted the study.

Scientists believe the universe formed some 13.8 billion years ago in a sudden expansion of matter and energy known as the Big Bang. Previous research showed its expansion has been speeding up for the past 5 billion years. The new study – performed using the 2.5-meter Sloan Telescope at Apache Point Observatory in New Mexico – is the first to make measurements showing expansion of the universe was slowing for the first 3 billion years after the Big Bang. The expansion later crested the top of the “roller coaster” and began to expand more rapidly some 5 billion years ago.

 Full press release.

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