January 2019 issue of American Journal of Physics

January 2019 Issue,
Volume 87, No. 1


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

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.



Comoving frames and the Lorentz–Fitzgerald contraction by Alon Drory.  DOI: /10.1119/1.5082535

Analytical solution of gravity tunnels through an inhomogeneous Earth byStefan Isermann.  DOI: 10.1119/1.5075717

Flying in formation: The orbital dynamics of LISA's three spacecraft by Joseph C. Amato.  DOI: 10.1119/1.5075722

Laboratory demonstration of acoustic source localization in two dimensions by Frank Lamelas, and Sudha Swaminathan.  DOI: 10.1119/1.5078510

Reliable determination of contact angle from the height and volume of sessile drops by F. Behroozi, and P. S. Behroozi.  DOI: /10.1119/1.5078512

The Fluidyne engine by Alejandro Romanelli.  DOI: 10.1119/1.5078518

Observation of the Talbot effect with water waves by Alexandra Bakman, Shmuel Fishman, Mathias Fink, Emmanuel Fort, and Sander Wildeman.  DOI: 10.1119/1.5081051

Apparatus and Demonstration Notes

LIGO analogy lab—A set of undergraduate lab experiments to demonstrate some principles of gravitational wave detection by Dennis Ugolini, Hanna Rafferty, Max Winter, Carsten Rockstuhl, and Antje Bergmann.  DOI: 10.1119/1.5066567


Taking teachers' ideas seriously: Exploring the role of physics faculty in preparing teachers in the era of the Next Generation Science Standards by Amy D. Robertson, Lane Seeley, Orlala T. Wentink, and Stamatis Vokos.  DOI:  10.1119/1.5082286


Stability of planetary systems: A numerical didactic approach by Renato Pakter, and Yan Levin.  DOI: 10.1119/1.5079541


Don't demean the geometric mean by Sanjoy Mahajan.  DOI: 10.1119/1.5082281

Book Reviews

The Age of Innocence: Nuclear Physics Between the First and Second World Warsby Cameron Reed.  DOI: 10.1119/1.5075721

Books Received

American Journal of Physics 87, 79 (2019); DOI: 10.1119/1.5082182


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