Hunting Einstein’s waves

This spring I traveled to Baton Rouge to visit a gravitational-wave hunter named LIGO. It’s one of the biggest and most expensive facilities the National Science Foundation has ever invested in, and it still hasn’t produced what it was built to do.

LIGO stands for Laser Interferometer Gravitational-wave Observatory, and its job is to hunt for gravitational waves — ripples in spacetime predicted by Einstein but never seen directly. It’s a tricky job, involving an elaborate system of lasers and mirrors to measure the infinitesimal changes in the machine as a gravitational wave passes through it. In 1999 I went to the inauguration of the Louisiana-based LIGO detector (there are two — the other is in Hanford, Washington) and listened to physicists talk about what it might mean to finally detect gravitational waves. Astonishingly, scientists knew at the time that the first generation LIGO detector might not be sensitive enough to snare the waves, and that they would need to build a more advanced version in order to announce a discovery.

That’s where LIGO is now. Over the past few years engineers have been ripping the guts out of both the Louisiana and Washington detectors and replacing them with more sensitive equipment. My Nature feature reports on how they have finished the construction work and are gearing up to test the upgraded system, in hopes of capturing Einstein’s waves once and for all.