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Image: LIGO/CIT

Scientists from the California Institute of Technology and the Massachusetts Institute of Technology achieved a remarkable feat last Friday, successfully "locking" the first of three giant interferometers that will be used to detect gravitational waves throughout the universe. Accelerating masses, such as exploding stars and vibrating black holes, cause these waves, which are distortions in space-time. And the idea behind each of the instruments is that these distortions will ever so slightly perturb laser light running through their miles of optical cavities, thereby changing the interference pattern where the beams intersect in a measurable way. Building three such detectors--two in Hanford, Wash., and one in Livingston, La.--will ensure that the scientists can rule out "local" distortions.

Friday's milestone marked the first time that laser light has traveled simultaneously down one of the instrument's two arms, which stretch out for two kilometers at roughly right angles. Video cameras recorded the buildup of light (above). As part of this exercise, the researchers also "locked" the mirrors directing the light into place with atomic-scale precision. The other two detectors completing this Laser Interferometer Gravitational-wave Observatory (LIGO) are scheduled for similar commissioning during the remainder of this year and next, and the first science run should commence sometime in 2002. Although this goal seems a long way off, the researchers stress the significance of "first lock." The director of this commissioning effort, Stan Whitcomb, compared it to the Wright brothers' first flight: "It doesn't stay up that long. It isn't very far off the ground. But it does fly!"