NSF funds Cadonati's search for gravitational waves

Physicist Laura Cadonati has received a three-year, $300,000 grant from the National Science Foundation to search for gravitational waves, ripples in the fabric of space-time produced by catastrophic events such as the collision of black holes and supernova explosions.

“Einstein’s theory of general relativity predicted the existence of gravitational waves in 1916, but so far we have only indirect evidence that they exist,” says Cadonati. “If we can detect them, it will be the beginning of a new era in astronomy. Since gravitational waves are not absorbed or altered by matter, they can provide us with information about mysterious objects like black holes and neutron stars.”

Cadonati will analyze data collected by the Laser Interferometer Gravitational Wave Observatory (LIGO), located in Washington and Louisiana. Funded by the National Science Foundation and constructed by researchers at the California Institute of Technology and the Massachusetts Institute of Technology, the observatory is capable of measuring minute changes in space caused by the passing of gravitational waves.

“Gravitational waves are produced in the distant universe by the acceleration of massive objects and grow weaker as they move away from the source,” says Cadonati. “By the time they reach the Earth, they distort space by less than the width of one proton. The technology to detect these waves has only been powerful enough since the 1990s.”

The two LIGO observatories operate as a single unit and consist of four-foot-diameter vacuum pipes arranged in the shape of an L with four-kilometer arms. Test masses fitted with mirrors hang from wires in the vertex and at the end of each arm, and the laser beams extend the entire length of the tube. When a gravitational wave passes, it will lengthen the laser beam in one arm and shorten it in the other. The colossal size of the detectors increases their sensitivity, and the use of two widely-spaced detectors is necessary to screen out the effects of local events like micro-earthquakes and acoustic noise, since these disturbances are unlikely to happen simultaneously at both locations.

The LIGO observatory has just finished a two-year data collection run, and data is being analyzed by Cadonati and other members of the LIGO Scientific Collaboration, a group of 580 scientists at universities throughout the United States and in 11 countries. The LIGO Scientific Collaboration Group on campus will focus on the discovery of the coalescence of two black holes and unmodeled bursts of gravitational waves.

Gravitational waves may be difficult to measure, but scientists have been confident that they exist since 1974, when campus researchers Joseph Taylor and Russell Hulse measured their effect on a binary pulsar system. Their research was awarded the 1993 Nobel Prize in Physics.

Detection of gravitational waves will provide the ultimate test of Einstein’s theory of general relativity and will also give astronomers a new way to visualize the universe. “All the information gathered by astronomers comes from visible light, gamma rays, x-rays and other electromagnetic waves,” says Cadonati. “Detecting and studying gravitational waves will add a new dimension to our ability to understand the universe.”

February 19, 2008.

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