LIGO
LIGO
One-line summary: The Laser Interferometric Gravitational-Wave Observatory — twin 4-km laser interferometers that detected ripples in spacetime itself from colliding black holes.
What it is
LIGO (Laser Interferometric Gravitational-Wave Observatory) is a pair of facilities, each with two ~4-km laser arms set at a right angle, under vacuum. A passing gravitational wave compresses space along one arm more than the other, changing the arms' relative length and producing a signal. As described by michelle-thaller, the detectors started in Oregon and Louisiana.
Why it matters to science
LIGO is Thaller's example of detecting "a wave that's actually made of space and time" — confirming gravitational waves, a prediction she "never thought they'd be able to actually detect." It also opens a potential observational window past the cosmic-microwave-background: gravitational waves can travel through the era when the early universe was opaque to light, possibly carrying information from the Big Bang itself.
Key facts
- Arms are ~4 km; the measured length changes are "thousands of times smaller than the nucleus of an atom."
- So sensitive that passing trucks or a sneeze register as noise; detectors sit in vacuum chambers.
- ~10 years ago, a black-hole merger millions of light-years away produced a chirp ("womp, womp, womp") seen first at one site, then at the other at the speed-of-light delay — confirming the signal.
- The result earned a Nobel Prize; "hundreds of people" were on the first paper. Now a routine detection (also neutron-star mergers).
Open questions
- Can detectors be improved enough to sense the gravitational waves of the Big Bang itself?