Born Aug. 26, 1728, in Mulhouse; died Sept. 25, 1777, in Berlin. German mathematician, astronomer, physicist, and philosopher. Member of the Academies of Sciences in Munich (1771) and Berlin (1765). A Frenchman by birth.
In mathematics Lambert is credited with the proof of the irrationality of the number π (1766). He is also the author of works devoted to algebra, the theory of parallel lines, the theory of perspective, and spherical trigonometry. Lambert was the first to apply systematically the method of hyperbolic functions. While working on logic calculus, he anticipated many ideas of J. Boole’s algebra of logic. His best known work in astronomy is a study of cometary orbits (1761) and the peculiarities in the motion of Jupiter and Saturn. He also introduced the concept of binary star. Lambert developed the idea of a hierarchical structure of the universe; he viewed the solar system as a first-order system, star clusters as second-order systems, and the Milky Way and similar distant nebulae as third-order systems. In physics his best-known work is a treatise on photometry (1760). Lambert, along with P. Bouguer, is considered to be the founder of this science. Lambert provided a theory explaining the reflection of light by dull surfaces and introduced the term “albedo” into science. By comparing the brightness of various stars, he attempted to determine the distance of the stars from the earth. He also studied the refraction of light in the atmosphere and hygrometry.
Lambert’s philosophical views were influenced by J. Locke, C. Wolff, and N. Malebranche. He was one of the predecessors of I. Kant as a critic of the theory of cognition. Lambert was also the first to propose the idea of a universal sign language.