How does LIGO detect gravitational waves?

By Hamish Johnston

This year’s physics Nobel prize has gone to three physicists who pioneered the LIGO observatory, which in 2015 made the first-ever detection of gravitational waves.

The LIGO detectors are famously capable of detecting changes in length smaller than one thousandth the diameter of a proton.

So how is this done?

One of the laureates – Rainer Weiss – is credited with coming up with the idea of using a giant interferometer to detect gravitational waves. In the above video Nergis Mavalvala – who was a PhD student of Weiss and is now a leader in gravitational-wave astronomy and quantum metrology – gives an introduction to how the detectors work.

For a much more detailed account, check out this feature article by David Appell “Catching gravity, rolling by”. In the article LIGO’s Sheila Dwyer – a former PhD student of Mavalvala, no less – explains how quantum mechanics lends a hand in making such exquisitely precise measurements.