Cavendish experiment

The Cavendish experiment was a laboratory measurement of the gravitational attraction between lead spheres, carried out by the English scientist Henry Cavendish with a torsion balance originally built by John Michell. Two small lead balls hung from the ends of a horizontal rod suspended on a thin wire, and two large lead balls were placed nearby; the tiny twist of the wire caused by their attraction was observed through a telescope from outside the room, so that the apparatus was not disturbed. Cavendish used the result to calculate the density of the Earth, obtaining a value close to the modern one, about five and a half times the density of water. The experiment is often described as weighing the Earth, since the gravitational constant and the planet's mass could later be derived from such data.

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