Article abstract: Planck’s discovery in 1900 that light consists of infinitesimal “quanta” and his articulation of the quantum theory replaced classical physics with modern quantum physics. This work not only resulted in Planck’s receiving the Nobel Prize in Physics for 1918 but also became a major enabling factor in the work of many other Nobel laureates.
Born into an intellectual family in Kiel, Schleswig, Max Karl Ernst Ludwig Planck spent most of his early life in Munich, where the family moved in the spring of 1867, when he was nine. Planck’s father, Johann Julius Wilhelm von Planck, was a professor of civil law at the university in Kiel, whose second wife, Emma Patzig, was Max’s mother. Max’s forebears included many lawyers and clergymen, a fact which helps explain Planck’s lifelong respect for the law and interest in religion.
In May, 1867, Planck was enrolled in Munich’s Konigliche Maximilian-Gymnasium, a classical Gymnasium, where he came under the tutelage of Hermann Müller, a mathematician who took an interest in the youth and taught him astronomy and mechanics as well as mathematics. It was from Müller that Planck first learned the principle of the conservation of energy that underlay much of his future work in thermodynamics and quantum theory.
Upon completion of the Gymnasium in 1874, Planck was at a personal crossroads. He was gifted in music and humanities as well as in mathematics and the sciences. He concluded ultimately that his music talents were insufficient to justify his continuing in that field. When he entered the University of Munich in October, 1874, he concentrated on mathematics. At Munich, however, his interest in physics grew, although his mathematics professors tried to dissuade him, arguing that nothing new remained to be discovered in the field.
Planck became ill as he was completing his first year at Munich and missed two years of school. In the winter term of 1877-1878, when he was well enough to resume his studies, he entered the University of Berlin, where he decided to study theoretical physics because of the order and logic that discipline demanded. Planck yearned to study the nature of the universe. Theoretical physics offered him his most sensible foothold for achieving that goal.
In Berlin, Planck studied with Hermann von Helmholtz, Gustav Kirchhoff, and Rudolf Clausius. Only Clausius was a gifted teacher, although the other two were able physicists. Planck learned much on his own through reading. Although his doctoral dissertation, on the second law of thermodynamics, was undistinguished, he was graduated summa cum laude in 1879. He taught mathematics and physics briefly at his former secondary school in Munich and in 1880 was appointed a privatdocent at the University of Munich. At that time, theoretical physics was viewed as an unpromising field, so his future seemed less than bright.
In 1885, Planck became an associate professor of physics at the University of Kiel, where he remained until 1888, when he was appointed assistant professor and director of the Institute for Theoretical Physics, to replace Kirchhoff, who had died. He rose to professor in 1892 and remained at Berlin until his retirement in 1926.
Planck’s early work in the laws of thermodynamics and his early interest in the principle of the conservation of energy figured largely in his research from his early teaching days at Kiel through his first decades at the University of Berlin. Although he had been reared on classical physics and was a conservative at heart, Planck began to realize that the laws of classical physics deviated greatly from results obtained in experimental physics. He found the greatest disparities not in the field of optics but in that of thermodynamics. The problems stemmed from the measurement of radiant energy in the frequency spectrum of black bodies.
Kirchhoff deduced that radiant energy is independent of the nature of its radiating substance, reasoning that black bodies that absorb all frequencies of light should therefore radiate all frequencies of light. Energy at that time was considered infinitely divisible, a theory that led to many anomalies and seeming contradictions in physics. The problem arose because the lower-frequency range has a smaller number of frequencies than the higher-frequency range.
Important physicists working on this problem reached conflicting conclusions. Wilhelm Wien devised an equation that explained the emissions at high frequencies but not at low frequencies. John William Strutt, Third Baron of Rayleigh devised an equation that worked for low frequencies but not for high frequencies. Work in the field was at an impasse when Planck devised a classically simple equation that explained the distribution of radiation over the full range of frequencies, basing his equation on...
(The entire section is 2023 words.)