How do lasers work?

Dec 5, 2023
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Laser Interferometer Gravitational-Wave Observatory uses two massive lasers placed thousands of miles apart to probe the very fabric of space-time.
This is a bit misleading.

There are multiple LIGO sites (three?) that are "thousands of miles apart," which allows them to identify the direction of gravitational waves via triangulation.

But each of those sites have two lasers at the site that are at right-angles to each other. When a gravitational wave passes through the site, one light path is shortened by a minuscule amount, relative to the other light path, allowing the gravitational wave to be detected.