August 20, 2009

Energy density of gravity waves estimated

An international group of scientists says it has defined the energy density of gravitational waves created immediately after the birth of the universe.

Gravitational waves that still ripple across the universe are believed to result from the Big Bang that created the universe more than 13 billion years ago. Albert Einstein predicted the existence of the waves in 1916, and the first evidence of their existence was reported in 1979.

Scientists from the Laser Interferometer Gravitational-Wave Observatory, a Caltech-Massachusetts Institute of Technology Scientific Collaboration, and the Virgo Collaboration of Italian and French scientists analyzed two years of data from LIGO instruments in Hanford, Wash., and Livingston, La.

The instruments use laser beams to measure how much the interferometer arms stretch and compress with the passage of gravitational waves and can detect a change of less than one-thousandth the diameter of the nucleus of an atom.

The scientists reported a quantitative estimate of the energy density of the background of gravitational waves left over from the Big Bang.

Our results are a major step toward the detection of primordial gravitational waves "¦ that were created as the universe expanded in its earliest moments, said Professor Lee Finn of Penn State, one of the study's authors.

The research appears in the journal Nature.