Q&A: Rainer Weiss on LIGO’s origins
Scientists from MIT and Caltech, along with others around the world, have made the first direct detection of gravitational waves reaching the Earth, using an instrument known as LIGO (Laser Interferometer Gravitational-Wave Observatory). LIGO is a system of two identical detectors located 1,865 miles apart. Each detector consists of two 4-kilometer-long vacuum tubes, arranged in an L-shape, through which scientists send laser beams. As each beam reaches the end of a tube, it bounces off a mirror and heads back in the opposite direction. All things being equal, both laser beams should arrive back at their source at precisely the same time and, due to interference, cancel the light that would go to a photodetector. If, however, a gravitational wave passes through the detector, according to Albert Einstein’s predictions of 100 years ago the wave should stretch space in one tube while contracting the space in the other tube by...