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Testing Gravity

5. Measuring the Gravitational Constant

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In this final mini-lecture, we discuss experiments that measure the gravitational constant (G) found in Newton’s Universal Law of Gravitation. In particular, we focus on: (i) Lord Henry Cavendish’s work in the late 18th century that was the first to experimentally confirm Newton’s Universal Law of Gravitation; (ii) modern measurements of G done by other lab groups outside the University of Washington, in particular the measurement done by Luther and Tower in 1982; (iii) the torsion balance setup used at the University of Washington to precisely measure G, including images and a video of the experiment; and (iv) the results of this experiment, which provided the most accurate measurement of G to date, and which can be used to accurately calculate the weight of the Earth.


In this course, Professor Jens Gundlach (University of Washington) explores gravity, in particular, gravity experiments. In the first mini-lecture, we give an overview of how our understanding of gravity and the Universe has evolved from ancient to modern times, emphasising various experiments, observations and theories that developed along the way. In the second mini-lecture, we introduce the modern theory of gravity, General Relativity. The third mini-lecture explores the big picture of physics, discussing the incompatibility between General Relativity and the Standard Model, and how physicists are searching for a unifying ‘Theory of Everything.’ In the fourth and fifth mini-lectures we turn towards gravity experiments, including those done at the University of Washington. In particular, we discuss experiments that test for Equivalence Principle violation and precisely measure the gravitational constant G.


Jens Gundlach is a Professor in the Department of Physics at the University of Washington in Seattle, Washington. He was a recipient of the 2021 Breakthrough Prize in Fundamental Physics for precision fundamental measurements that test our understanding of gravity, probe the nature of dark energy, and establish limits on couplings to dark matter. Naturally, his research interests include experimental fundamental physics, however Professor Gundlach also conducts research in biophysics. In particular, he is interested in nanopore sequencing of DNA.

Cite this Lecture

APA style

Gundlach, J. (2022, January 12). Testing Gravity - Measuring the Gravitational Constant [Video]. MASSOLIT.

MLA style

Gundlach, Jens. "Testing Gravity – Measuring the Gravitational Constant." MASSOLIT, uploaded by MASSOLIT, 12 Jan 2022,

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