For years scientists have investigated ways of observing a phenomenon known as gravitational waves. As part of his theory of relativity, Albert Einstein speculated about the existence of the waves in 1916. He reasoned that the waves resulted from large masses moving suddenly, causing ripples throughout the universe. Scientists at the California Institute of Technology in Pasadena, Calif., and the Massachusetts Institute of Technology in Cambridge, Mass., are set to begin installing Nd:YAG lasers this month in a five-mile-long scientific apparatus being erected to detect the waves. The project, dubbed the Laser Interferometer Gravitation-Wave Observatory, will be established at the Hanford Nuclear Observatory in Richland, Wash., at a cost of $365 million. The interferometer will comprise two arms -- forming an L shape when viewed from above. When a gravitational wave hits Earth, the laser interferometers will detect interference in the laser beam. Photodetectors will record any interference and convert the wave into an electrical signal. Researchers hope the huge observatory will record such events as the collision of neutron stars and other phenomena that occur more than 70 million light-years away.