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>"Lack of Gravity Waves Puts Limits on Exotic Cosmology Theories
By Clara Moskowitz
Staff Writer
posted: 19 August 2009
02:36 pm ET

This time, scientists are excited to find nothing.

In results announced today, a huge physics experiment built to detect gravitational waves has yet to find any.

Rather than be disappointed by the null findings, physicists say the results were expected, and in fact help them narrow down possibilities for what the universe was like just after it was born.

The Laser Interferometer Gravitational-Wave Observatory Scientific Collaboration (LIGO) is a set of instruments in Louisiana and Washington built to search for evidence of gravitational waves, which are theoretical ripples in space-time thought to be caused by the acceleration of mass. No one has yet directly detected these waves, though they are predicted by Einstein's theory of General Relativity, and are widely thought to permeate our universe.

In theory, every time mass accelerates - even when you rise up out of your chair - the curvature of space-time changes, and ripples are produced. However, the gravitational waves produced by one person are so small as to be negligible. The waves produced by large masses, though, such as the collision of two black holes or a large supernova explosion, could be large enough to be detected."<