”The equality (proportionality) of the gravitational and inertial mass has been proved with great accuracy in an investigation of great importance to us by Eötvös...” -Einstein, 1913
”The Michelson-Morley and the Eötvös experiments were critical to Einstein’s work and form the pillars of his most famous theories, the special and general theory of relativity...” -József Illy, The Practical Einstein
SCARCE FIRST EDITION of the account of Eötvös’s experiment establishing the equality of inertial and gravitational mass, AN ESSENTIAL COMPONENT OF EINSTEIN’S GENERAL RELATIVITY.
“In 1888 [Eötvös] developed the Eötvös torsion balance, consisting of a bar with two attached weights, the bar being suspended by a torsion fiber. He argued that if the two weights were made from different materials, and if the inertial and gravitational forces were not equivalent, there would be a discernible twisting force, which would cause a slight rotation of the bar about a vertical axis. Observations were made with copper, aluminum, asbestos, platinum, and other materials. No torque was found and Eötvös concluded that the masses of different materials were equivalent to a few parts per billion. His experiments were repeated in the 1960s by Dicke and in 1970 by Braginsky, with results affirming the equivalence to 1 part per 100 billion and 1 part per trillion respectively. The experiment became one of the foundation stones of general relativity since, by failing to distinguish between inertial and gravitational mass experimentally, it supported Einstein’s principle of equivalence” (Biographical Encyclopedia of Scientists).
IN: Mathematische und naturwissenschaftliche Berichte aus Ungarn, 8 Band, pp. 65-68. October 1889-October 1890. Berlin: Friedlander, 1891. Octavo, recent half calf over marbled boards. A fine copy, very handsomely bound. EXTREMELY RARE.