ISSN 1019-3316, Herald of the Russian Academy of Sciences, 2008, Vol. 78, No. 3, pp. 309–312. © Pleiades Publishing, Ltd., 2008. Original Russian Text © R.N. Shcherbakov, 2008, published in Vestnik Rossiiskoi Akademii Nauk, 2008, Vol. 78, No. 5, pp. 461–465.
Profiles DOI: 10.1134/S1019331608030209
A Reluctant Revolutionary On the 150th Anniversary of the Birth of Max Planck Planck was born on April 23, 1858, in Kiel into the family of a professor of law. He spent his childhood and youth in Munich, where he studied at a classical gymnasium at first but later, upon becoming interested in music, mathematics, and physics, preferred exact sciences. At the age of 16, he entered the University of Munich and studied there for three yeas; then he studied for a year at the famous University of Berlin. According to Planck, at this university, he was more interested in studying R. Clausius’s writings than listening to lectures by outstanding scientists, such as G. Kirchhoff and H. von Helmholtz. Planck said that Clausius’s works, “written in lucid, understandable language,” had impressed him greatly, and he went deeper into them with growing enthusiasm. He particularly appreciated the exact formulation of the two laws of the theory of heat [2, p. 650].
Each time we look attentively into the serious and sometimes estranged faces of the luminaries of science, we always see in their eyes the strain of impetuous human thought that strove to comprehend the laws of the universe and determined the meaning of their lives. Max Planck, a German theoretical physicist, who was involved in studying heat radiation and one of the founders of quantum theory, occupies a worthy place among these great achievers. He was educated according to the ideals of classical physics and thought within the framework of its dominant paradigm. “He was conservative by nature and averse to revolutionary novelties …” [1]. There are always plenty of people in society who think that scientists are conservatives. To an extent, this is right because only scientists know the true value of accumulated scientific knowledge, appreciate it, and know better than anyone else how difficult it is to change anything in this knowledge. In his scientific activity, Planck was faithful to the classical ideals as long as it was possible.
Upon returning to Munich in 1878, Planck passed his qualifying examinations for the right to teach physics and mathematics at universities; a year later, he defended his doctoral dissertation “On the Second Fundamental Theorem of the Mechanical Theory of Heat,” in which he formulated in general terms the law of entropy. However, the then scientific community was not very impressed by this work of his and did not understand its true value. At first, the scientist worked at the University of Munich; then he was elected a professor of the University of Kiel and then, for a long time, was a professor at the University of Berlin. At the University of Berlin, he was appointed head of the Department of Theoretical Physics of the Faculty of Philosophy at the time when philosophy was unpopular among physicists. In 1894, after the death of A. Kundt and Helmholtz, the 36-yearold Planck continued his studies in theoretical physics. Planck’s life at the beginning of his academic career was full of difficulties and nonrecognition; in the years of fascism and World War II, he went through mistakes and disappointments; and his family life was full of disasters and tragedies. Planck remembered that his new statements were hardly ever recognized because he could prove them only theoretically, although perfectly strictly [2, p. 655]. This was natural because, for a long time,
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experimental physics had been the main and most respected physical discipline. However, as Planck continued to obtain substantial and, later, even outstanding scientific results, he became the most famous physicist in Berlin and then, from the beginning of the 20th century, the leading German theoretical physicist. External attributes of scientific fame, which are equally important for a scientist, also testified to this fact: in 1894, he became a member of the Prussian Academy of Sciences; from 1912 through 1938, he was its permanent secretary; in 1930, he became president of the Kaiser Wilhelm Society. In 1918, Planck was awarded the Nobel Prize “in recognition of the services he rendered to the advancement of physics by his discovery of energy quanta.” However, all this happened much later. At the beginning, Planck, combating the indifference of his colleagues to his studies, consistently solved the problems he was interested in. In the first place, these were the second law of thermodynamics and entropy. Trying to understand their nature, the scientist adverted to the theory of heat radiation in W. Wien’s interpretation, improved it, and finally came to energy quanta, which later raised him to the peak of his scientific fame. In those times, scientists were searching for the law of energy distribution in the spectrum of equilibrium blackbody radiation with regard to absolute temperature. Proceeding from the studies by Kirchhoff, L. Boltzmann, and Wien and taking into account that the distribution law in a Wien spectrum “is not generally valid” [2, p. 249], Planck, after much effort, inferred a formula for this law, which corresponded to experimental data received at the same time. Then, it was necessary to substantiate this law [2, p. 439]; in two months, the statistical substantiation was received. As a purely formal assumption, the scientist used the idea of discrete energy elements of oscillators. He obtained the value of an “energy element” (Planck’s term) that depended on the frequency of radiation. Information about the factor of proportionality h, part of the energy quantum formula, appeared in the 42-year-old scientist’s paper “On the Law of Distribution of Energy in the Normal Spectrum,” which was presented to the German Physical Society on December 14, 1900. At the same time, he received a constant, which was later called the Boltzmann constant; the Avogadro constant; and the electron charge, the values of which agreed with the previously calculated ones. Later, Planck recalled that he had been both very surprised and happy when J. Franck and G. Hertz, who experimented with excitation of the spectral line by electron bombardment, found a method of measuring this constant. However, the scientist went on; it was necessary to assign a physical meaning to this constant because its introduction meant separation from classical physics [2, p. 442]. Three decades later, Planck wrote [2, p. 512]:
Striving to understand experimental facts on the basis of the two laws of thermodynamics, I came to the radical hypothesis that the multitude of states in which an oscillating radiating system may be was discrete, countable, while the difference between two such states was characterized by one universal constant—the elementary action quantum. Planck’s colleagues were slow to accept his discovery. L. de Broglie called the energy quantum hypothesis a clever method that could improve the theory of an interesting but particular phenomenon. W. Heisenberg explained it by the scientist’s desire to clear up the previously unsolved problem of blackbody radiation. A. Sommerfeld saw in this hypothesis only a form of explanation rather than a physical reality. Planck’s action quantum became a “troublemaker” (de Broglie) in science; a “splinter in scientists' minds” (Heisenberg); and a “mysterious herald from the real world,” which introduced “illogicality” in physics (L.D. Landau). Modern physicists are of the opinion that today, “no phenomenon of quantum physics could be described consistently without Planck’s constant” [3]. However, even from the position of a modern scientist, who is a century away from that great event, Planck’s discovery appears somewhat mediocre: “From the mathematical point of view, this was merely a replacement of a continuous multitude of values of energy by a discrete multitude …. As for the value h, he selected it in view of obtaining agreement with experimental data …. Obviously, what Planck did was a mere manipulation” [4]. It was A. Einstein who played the main role in drawing attention to Planck’s hypothesis and in its recognition. In 1905, he came to the conclusion that the energy of light might be radiated and absorbed by an oscillating particle only in the form of so-called “light quanta” (which were later called photons), the value of which equals the product of Planck’s constant and the oscillation frequency. In 1907, the scientist used the energy quanta hypothesis in his studies of the heat capacity of solids under low temperatures. Planck, according to his own statements, tried more than once to introduce the action quantum in the system of definitions of classical physics [2, p. 442]. In 1911, at the First Solvay Conference, he presented a paper on the blackbody radiation law and the elementary action quantum hypothesis, which was actively discussed by the participants in the conference: H. Lorentz, H. Poincaré, Einstein, Sommerfeld, Wien, and others. Later, it became obvious that Planck’s discovery was a breakthrough in the understanding of the microworld. Einstein’s explanation of the photoelectric effect, N. Bohr’s quantum model of the atomic structure, de Broglie’s wave–particle duality, and Heisenberg’s quantum mechanics and uncertainty principle helped understand the fundamental role of Planck’s
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constant for the development of quantum mechanics and elementary particle physics. If we trace the “points of influence” of Planck’s quantum theory on the subsequent development of the physics of the microworld, we will see that the result is the emergence of matrix and wave mechanics, quantum field theory, quantum statistics, quantum optics, quantum chemistry, and other disciplines. When Planck saw how actively quantum mechanics and atomic physics were applying his constant to their constructions, he agreed at last that the emergence of the elementary action quantum had led to a new epoch in physics [2, p. 431]. With regard to Planck’s contribution to the development of physics, Einstein emphasized: “He showed convincingly that in addition to the atomistic structure of matter there is a kind of atomistic structure to energy, governed by the universal constant …” [5, p. 257]. At present, Planck’s constant is viewed as a fundamental physical constant. In 1899, in connection with the discovery of the new fundamental constant, Planck considered the necessity to search for natural units of measurement. He came to the conclusion that, on the basis of a combination of the gravitational constant, the speed of light, and the new constant (Planck’s constant), it was desirable to introduce “natural units” for measuring length, time, mass, and temperature [2, pp. 232, 233]. According to Planck, these units preserve their numerical values if the laws of gravitation, thermodynamics, and the speed of light do not change. With time, scientists began to regard his ideas as very fruitful. Today, answering the scientifically topical question “Is the Planck scale not a mirage?” Academician L.B. Okun’ presents his pros and cons and stresses that “even within the framework of simple astrophysics, Planck’s units are perceived now as natural” [6, p. 191]. The Planck mass, which is regarded “as a fundamental physical value, characterizing the energy scale of the theories of the superunification of all interactions” [6, p. 181], is especially popular. According to D. Gross, a Nobel laureate, physics based on the Planck scale requires a transition from the standard model of elementary particle physics to string theory. Perhaps, this will lead to a deeper understanding of microworld laws [7, p. 36]. Planck was one of the first to understand and accept the theory of relativity. In 1914, Planck and W. Nernst did their best to invite Einstein to the University of Berlin where he could continue his studies. By that time, Planck had already conducted a number of his own studies on the basis of Einstein’s theory. Proceeding from the relativity principle, the scientist determined the form of the main equations of the mechanics of point mass in relativistic physics and showed, according to Einstein, that the principle of least action in the theory of relativity was as fundamentally important as in classical mechanics [5, p. 13]. In addition, he was the first to consider the dynamics of HERALD OF THE RUSSIAN ACADEMY OF SCIENCES
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the radiation of a moving blackbody and he developed the relativistic theory of thermodynamic processes. Thus, like many of his great contemporaries, Planck actively participated in creating and developing quantum mechanics and the theory of relativity, compared to which, according to H. Weyl, everything else faded. His fame as the discoverer of energy quanta and his scientific position and connections drew the attention of not only European but also of Russian and then Soviet scientists. In various years of his life, Planck corresponded or met with V.A. Mikhel’son, B.B. Golitsyn, P.N. Lebedev, Ya.I. Frenkel’, S.I. Vavilov, and L.I. Mandel’shtam; he was on friendly terms with A.F. Ioffe, N.V. Timofeev-Resovskii, and other Russian scientists. In 1925, Planck visited the Soviet Union in connection with the 200th anniversary of the USSR Academy of Sciences. In 1926, he became a foreign member of the USSR Academy of Sciences. Planck’s professional interests were wide. He examined the role of physics and physicists in understanding the world and presented his opinions with regard to nuances of scientific cognition in physics in discussions of W. Ostwald’s energy concepts and E. Mach’s theory of economical thinking. In midlife, Planck adverted to systemic studies of general, philosophical, and methodological problems of physics and physical cognition. His works were devoted to the unity of the physical picture of the world, new ways to physical cognition, the origin and influence of scientific ideas, the meaning and limits of exact science, etc. Teaching at institutions of higher education was a significant aspect of Planck’s activity. He spent much effort to educate young scientists and to form their scientific and worldview ideas; he communicated his vision and interpretation of physical science to his students and explained the importance of scientific knowledge for their worldview and practice. Planck’s monographs and textbooks The Principle of the Conservation of Energy, Treatise on Thermodynamics, The Theory of Heat Radiation, and Eight Lectures of Theoretical Physics were very popular and saw many editions. Einstein wrote that the pleasure one felt when taking Planck’s books in one’s hands was to a significant extent determined by his simple, truly belletristic style, which was inherent in all Planck’s works [5, p. 13]. Planck associated the future of science with good education [8, p. 189]: The right planning of school education is one of the most important conditions of scientific progress …. What is taught is less important than how it is taught …. The function of a school is to develop consistent methodological thinking …. The main point in this respect is to give the right interpretation of facts rather than to give a great number of them. Vol. 78
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In his inauguration speech as president of Berlin University, Planck defined the goal of higher education in the following way: “No doubt, imparting scientific independence is the most important goal of academic teaching; scientific views acquired in the course of fair work are also a strong basis for a moral outlook on life, which can withstand all ups and downs” [8, p. 84]. However, despite his authority, Planck, unlike Kundt, Sommerfeld, and M. Born, did not found his own scientific school, although he had a number of students and assistants (M. Laue, M. Abraham, Hertz, Franck, E. Zermelo, L. Meitner, and others). Evidently, this was because of his excessive emphasis on future scientists' independence and his numerous duties as the secretary of the academy, which left him no time to train students. Addressing students in March 1947, Planck concluded his presentation with the following heartfelt words: “He who has been fortunate enough to participate in developing exact science will find the highest satisfaction and inner calm in the knowledge that he studied the researchable and respected the unresearchable” [9, p. 161]. Perhaps, this was both the scientist’s assessment of his work and his parting words to the young. Planck was always a devoted citizen of his country. However, his naivety and political and social inexperience made him take steps about which he felt deeply sorry afterwards. To begin with, these were his militaristic attitudes of 1914–1918 and the celebration of German honor, dignity, and will to win. Two decades later, he put up with fascism, which prevented him as a “nationalistically oriented German” [9], despite his antifascist views, from speaking up in defense of unwanted scientists. The only thing the great Planck could do under those conditions was to compromise with the existing regime to save German science from full liquidation and to protect the young from degradation and mysticism. The fascist regime brought grievous material and spiritual losses to Planck and other German scientists, such as the isolation of German science after WWI and its deconstruction in the years of Hitlerism. The scientist felt deep disappointment in the authorities in which he had trusted so much and which had brought so much suffering and destruction to peoples. Despite his privileged position, disasters fell on Planck as well.
Planck’s human losses were devastating. In 1909, his first wife died after more than 20 years of happy marriage. His elder son Karl was killed in action at Verdun during WWI. Both daughters died while giving birth to their first children. His son Erwin was hanged because of his participation in the failed attempt to assassinate Hitler. At the end of the war, Planck himself was caught in a bombing raid and had a miraculous escape. Nevertheless, he preserved good health and the ability to work until the end of his difficult life, which was largely explained by the strict tenacity of his spirit and behavior and his regular and simple everyday life. The great scientist died on October 4, 1947, in Göttingen at the age of 89. In Göttingen, at the residence of his relatives, he spent the last two years of his life together with his second wife and was buried there. Einstein commented on this sad event in the following way: “A man who gave the world a great creative idea does not need praise of the next generations. His creative work has given him a more significant benefit.” R.N. Shcherbakov, Dr. Sci. (Ed.) REFERENCES 1. M. Born, Reflections and Reminiscences of a Physicist (Nauka, Moscow, 1977) [in Russian]. 2. M. Planck, Selected Works (Nauka, Moscow, 1975) [in Russian]. 3. L. I. Ponomarev, “On the Centenary of the Action Quantum Discovery,” in Studies on the History of Physics and Mechanics, 2002 (Nauka, Moscow, 2003), p. 10 [in Russian]. 4. M. B. Menskii, Humans and the Quantum World (Vek 2, Fryazino, 2005), pp. 33–35. 5. A. Einstein, Collection of Scientific Works (Nauka, Moscow, 1967), Vol. 4 [in Russian]. 6. L. B. Okun’, “Fundamental Constants of Physics,” Usp. Fiz. Nauk 161 (9) (1991). 7. D. Gross, “The Coming Revolutions in Fundamental Physics,” Znanie Sila, No. 10 (2007). 8. M. Plank, Unity of the Physical Picture of the World (Nauka, Moscow, 1966) [in Russian]. 9. F. Herneck, Pioneers of the Nuclear Age (Progress, Moscow, 1974) [in Russian].
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