Planck, Max

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PLANCK, MAX

PLANCK, MAX (1858–1947), German theoretical physicist.

Max Karl Ernst Ludwig Planck, the initiator of a fundamental transformation in physics deeper even than the theory of relativity, was a revolutionary neither by background nor by temperament. He came from a line of pastors, theologians, and jurists and married the daughter of a banker. His father was a professor of law, first at Kiel, where Planck was born, and then in Munich, where he attended university.

As a student, Planck distinguished himself by breadth rather than brilliance. He toyed with making a career as a historian, musician (he played the piano at concert level), or mathematician. He decided on physics as a way of combining mathematics with earthier interests. But he stayed close to the abstract, developing his physical ideas without special assumptions about the structure of matter and without reference to the concerns of human beings. Whereas Albert Einstein's test for the goodness of a theory was whether God would like it, Planck's was whether a Martian could understand it.

The branch of physics that lent itself best to Planck's approach was thermodynamics. He took its principles as the subject of his doctoral thesis (1879) and pursued their applications as extraordinary professor of physics in Kiel and during his first decade in Berlin, where he became professor of theoretical physics in 1888. In the late 1890s, however, he found that he could not solve the problem he had set himself without recourse to an atomic model.

This problem, from which quantum theory emerged, was the derivation of the relative intensities I(n) of the various frequencies n in the radiant heat within an oven maintained at a constant temperature T. This problem intrigued Planck because, on thermodynamic grounds, I should depend only on the quotient n/T and not at all on the material or shape of the oven. Thus he could picture the radiators in its walls as he pleased without compromising generality. He chose identical charged particles attached to perfectly elastic massless springs. To derive a formula that fit the measurements, he supposed, against his previous absolutism and in agreement with the statistical mechanics of Ludwig Boltzmann (1844–1906), that the entropy principle permitted exceptions. This supposition when applied to the oscillators underwrote late in 1900 a derivation that limited the energy possessed by an oscillator of frequency n to a multiple of hn, where h, "Planck's constant," came from fitting the formula to experimental results.

Planck delighted in his formula because of a second universal constant (besides h) that it contained; he called it k and named it after Boltzmann. Unlike h, k had a clear physical meaning. Through it Planck could calculate the electronic charge and other atomic constants. For the formula and the calculations, he almost received the Nobel prize in 1908. Before the Royal Swedish Academy of Sciences accepted him, however, it learned that energy quanta might not be compatible with sound physics. Planck did receive the physics prize, but not until 1919 (the reserved prize for 1918).

Planck came to regard the violation of ordinary ideas required by the acceptance of the quantum discontinuity as a good thing, a step toward the removal of human traces from physical science. For a similar reason—its rejection of ordinary ideas of space and time—Planck promoted relativity theory immediately after its publication in 1905. Later, his extraterrestrial epistemology enabled him to accept, while Einstein (1879–1955) rejected, wave mechanics and its probabilistic interpretation.

In 1912 Planck began the administrative career that would make him the most respected spokesman for German science. In that year he took office as a permanent secretary of the Prussian Academy of Sciences. He added service to and ultimately (in 1930) assumed the presidency of the Kaiser-Wil-helm-Gesellschaft (KWG), the most important organization for scientific research in Germany. His frequent lectures on the nature of science, science and values, science and religion, and the state of physics earned him a wide following between the wars. His standing during the postwar Weimar period was enhanced by his behavior during World War I. He was the only signatory to the infamous manifesto supporting the German army's actions in Belgium, An die Kulturwelt!, to repudiate it during the war. He had a deserved reputation for courage and probity. Even Einstein, whose religion, pacifism, and bohemian behavior separated him from most Germans, esteemed Planck for his human qualities. They were fast friends until the Nazis took power in 1933.

Planck visited Adolf Hitler in 1933 soon after the promulgation of the law cleansing the civil service—which, with some loopholes, discharged Jews from government jobs including university professorships. Planck protested that the measure would cripple German science. Hitler replied that he had nothing against Jews, only against communists, and that all Jews were communists. He then flew into such a rage that Planck could only creep away. Nevertheless, Planck retained his positions in the Academy and the KWG in hope of protecting their employees and for fear of being replaced by a party hack. This decision required him to give the Hitler salute, pay court to small-minded government and party officials, discharge some Jews to keep others, and make other demeaning concessions.

Planck decided to retain his offices well beyond retirement age (he was seventy-five in 1933) on the mistaken belief that he still possessed the sort of influence he had enjoyed in imperial and Weimar times. He found out just how little influence his compliance had earned him when, in 1944, he sought clemency for his son, an army officer implicated in the plot to kill Hitler. Planck could not even obtain a hearing; Erwin Planck was executed; and Planck lost the last of the four children who, along with his first wife, friends, work, and music, had made his life and home a joy before World War I. (His elder son was killed in the war; his wife died before it began, and his twin daughters at its end.)

At the end of World War II, Allied bombing drove Planck and his second wife out of Berlin and into the woods near Göttingen. Rescued by American troops, the old man (then eighty-seven) revived enough to attend, as the only German invited, the postponed celebration in London of the 300th anniversary of Isaac Newton's birth, and to serve as the figurehead president of the revived KWG. The American occupiers agreed to the revival on condition that the institution change its name. It prospers into the early twenty-first century as the Max Planck Society for the Advancement of Science.

See alsoPhysics; Science and Technology.

bibliography

Primary Sources

Hentschel, Klaus, ed. Physics and National Socialism: An Anthology of Primary Sources. Translated by Ann M. Hentschel. Basel, 1996.

Planck, Max. The Origin and Development of the Quantum Theory. Translated by H. T. Clarke and L. Silberstein. Oxford, U.K., 1920. Planck's Nobel lecture.

——. Scientific Autobiography, and Other Papers. New York, 1949. Includes some of Planck's public lectures.

——. Physikalische Abhandlungen und Vorträge. 3 vols. Braunschweig, 1958.

——. The New Science. Translated by James Murphy and W. H. Johnston. New York, 1959.