# Johann Heinrich Lambert

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## Lambert, Johann Heinrich

(yō`hän hīn`rĭkh läm`bĕrt), 1728–77, German-French philosopher and scientist, b. Alsace. He developed many basic concepts in mathematics, including that of the hyperbolic functions in trigonometry. In physics he achieved valuable results in work on the measurement of the intensity of light (the metric unit of brightness in the cgs system is named for him), degrees of heat, and humidity. In his philosophical work*Neues Organon*(1764) he pointed out the importance of beginning with experience and using the analytical method to investigate any theory of knowledge. His correspondence with Kant is of great philosophical significance. His other important books are

*Photometria*(1760) and

*Pyrometrie*(1779).

## Lambert, Johann Heinrich

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.

### WORKS

*Opera mathematica,*vols. 1–2. Zürich, 1946–48.

*Photometria, sive de mensura et gradibus luminis, colorum et umbrae.*Augsburg, 1760.

*Cosmologische Briefe.*Zürich, 1761.

*Neues Organon,*vols. 1–2. Leipzig, 1764.

*Logische und philosophische Abhandlungen,*vols. 1–2. Edited by J. Bernoulli. Berlin, 1782–87.

### REFERENCE

Barthel, E. “Johann Heinrich Lambert.”*Archiv fü r Geschicte der Mathematik, der Naturwissenschaften und der Technik,*1929, vol. 11. fasc. 1.2.