A team of researchers at the California Institute of Technology in Pasadena used a laser interferometer to look for the gravity waves that Einstein predicted in his general theory of relativity. The instrument is a precursor to the national Laser Interferometer Gravitational-Wave Observatory, a titanic device under construction in Hanford, Wash., and Livingston, La. The scientists employed a laser beam in a pair of 40-m vacuum tubes to measure the gravitational displacements caused by neutron star pairs within our galaxy. They determined that the upper limit for the frequency of the phenomena is once every two hours. The National Science Foundation-funded observatory's two 4-km-long tubes will be able to detect displacements smaller than the diameter of a proton. It is expected to be in service by the end of 2001.