LIGO analogy lab—A set of undergraduate lab experiments to demonstrate some principles of gravitational wave detection

Abstract

The first direct detection of gravitational waves by the Laser Interferometer Gravitational-Wave Observatory (LIGO) in September 2015 proved their existence, as predicted by Einstein's General Theory of Relativity, and ushered in the era of gravitational-wave interferometry. In this article, we present a set of lab course experiments at different levels of advancement, which give students insight into the basic LIGO operating principle and advanced detection techniques. Starting with methods for folding an optical cavity, we advance to analogy experiments with sound waves that can be detected with a Michelson interferometer with an optical cavity arm. In that experiment, students also learn how the sensitivity of the device can be tuned. In a last step, we show how optical heterodyne detection (the mixing of a signal with a reference oscillator) was used in Initial LIGO. We hope these experiments not only give students an understanding of some LIGO techniques but also awaken a fascination for how unimaginably tiny signals, created by powerful cosmic events a billion years ago or earlier, can be detected today here on Earth.

An interactive gravitational-wave detector model for museums and fairs

“…The exhibit highlights both the behaviour of gravitational waves-changing relative distances on a small scale-and the technologies necessary to measure this behaviour. Such an interferometer is a common item in the tool-kit of gravitational-wave education and outreach and is often used in undergraduate laboratory experiments [30][31][32][33] . The University of Birmingham has expertise in designing and building instruments such as interferometers.…”