Laser Interferometer Gravitational-Wave Observatory. This is used to observe gravitational waves, and determine how they deform space-time. Each of the "legs" is a 2.5 mile long vacuum chamber. This is one of two LIGO detectors - the other is in Hanford, WA.
In The News, Scientific - Astronomy
Links: www.ligo.caltech.edu, www.nytimes.com
By: robsv