First theorized by Albert Einstein in 1916, gravitational waves are defined as fluctuations in space-time that emanate from certain binary systems (such as two black holes colliding). It takes some sort of major event in the universe to produce gravitational waves. Although they can't be directly detected, scientists have tried to identify the waves by the ripples they send through space-time.
So far, scientists have been able to detect the influence of these waves on neutron stars orbiting one another; in 1993, Joseph Taylor and Russell Hulse received the Nobel Prize in physics for advancing studies in the field. Scientists have been working on designing computer programs that would model gravitational waves so that they could detect them. The real question is why it's important to detect and understand gravitational waves.
The answer lies in the contribution these waves can make to physicists' and astronomers' understanding and explanation of some of the most basic laws of physics. As far as we've come since Einstein's time, there still is a long way to go. There also are still questions -- or points to prove -- regarding how the universe began and how events such as formation of black holes or deaths of stars occur.
NASA had been involved in developing a satellite called the Laser Interferometer Space Antenna, or LISA, along with the European Space Agency (ESA). In April 2011, NASA announced that it would pull out of the LISA program because of budgetary constraints [source: Cowen]. The ESA planned to continue with the mission to measure gravitational waves with lasers from a spacecraft, albeit likely on a smaller scale than originally planned.
All is not lost as far as gravitational wave detection goes, however. The California Institute of Technology has partnered with the National Science Foundation and the Massachusetts Institute of Technology to construct the Laser Interferometer Gravitational-Wave Observatory (LIGO). The goals of LIGO include verifying -- directly -- that gravitational waves exist, testing properties and predictions regarding the waves' propagation, speed and direction and confirming the existence of black holes. According to the project's Web site, it will be "the most stringent test ever of Einstein's general relativity theory" [source: California Institute of Technology].
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