Henry Cavendish
Abstract
Henry Cavendish (1731–1810) was an English natural philosopher and chemist renowned for his precise experimental work. Conducted in 1797–1798, the Cavendish experiment stands as a monumental achievement in measuring the force of gravity between masses in a controlled laboratory setting, enabling the calculation of Earth's density and mass.
Introduction
Cavendish's torsion balance experiment marked a watershed moment in gravitational physics. By translating Newtonian universal gravitation into measurable laboratory forces, he provided the empirical bridge needed to connect celestial mechanics with terrestrial measurement.
Experiment Details
The apparatus utilized a torsion balance where two small lead spheres were suspended from a delicate wire, while two larger lead spheres were positioned nearby to exert gravitational attraction. By measuring the minuscule twisting angle of the wire, Cavendish determined the gravitational force between the masses:
\[ F = G \frac{m_1 m_2}{r^2} \]Results and Significance
Though Cavendish framed his results in terms of determining the mean density of the Earth (finding it to be roughly \(5.48\) times that of water), his data implicitly yielded the gravitational constant \(G\). This precise measurement validated Newton's law of universal gravitation on a laboratory scale and allowed scientists to "weigh the Earth" for the first time.
Legacy
Beyond his work on gravity, Cavendish discovered hydrogen (which he termed "inflammable air") and demonstrated that water is a compound of hydrogen and oxygen. His rigorous approach to precision instrumentation set a new benchmark for quantitative physical science.