Max Planck

Max Karl Ernst Ludwig Planck was a German theoretical physicist. He won the 1918 Nobel Prize in Physics "for the services he rendered to the advancement of physics by his discovery of energy quanta".
Planck made many substantial contributions to theoretical physics, but his fame primarily on his role as the originator of quantum theory and one of the founders of modern physics, which revolutionized understanding of atomic and subatomic processes. He is known for the Planck constant,, which is of foundational importance for quantum physics, and which he used to derive a set of units, now called Planck units, expressed only in terms of physical constants. The Planck relation, =, states that the energy of a photon is proportional to its frequency.
Planck was twice President of the Kaiser Wilhelm Society. In 1948 it was renamed the Max Planck Society, and today includes 83 institutions representing a wide range of scientific disciplines.

Early life and education

Max Karl Ernst Ludwig Planck was born on 23 April 1858 in Kiel, Holstein, the son of Johann Julius Wilhelm Planck and his second wife, Emma Patzig. He was baptized with the name of Karl Ernst Ludwig Marx Planck; of his given names, Marx was indicated as the "appellation name". However, by the age of ten he signed with the name Max and used this for the rest of his life.
Planck came from a traditional, intellectual family. His paternal great-grandfather and grandfather were both theology professors in Göttingen; his father was a law professor at the University of Kiel and Munich. One of his uncles was also a judge.
Planck was the sixth child in the family, though two of his siblings were from his father's first marriage. War was common during Planck's early years and among his earliest memories was the marching of Prussian and Austrian troops into Kiel during the Second Schleswig War in 1864.
In 1867, the family moved to Munich, where Planck enrolled at Maximiliansgymnasium. There, his mathematical talents emerged early and he later 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 law of conservation of energy. This is how Planck first came in contact with the field of physics. Planck graduated early, at age 17.
Planck was gifted in music; he took singing lessons and played piano, organ and cello, and composed songs and operas. Per Britannica, "He possessed the gift of absolute pitch and was an excellent pianist who daily found serenity and delight at the keyboard, enjoying especially the works of Schubert and Brahms."
In 1874, Planck enrolled at the University of Munich. Under professor Philipp von Jolly's supervision, Planck performed the only experiments of his scientific career, studying the diffusion of hydrogen through heated platinum, but transferred to theoretical physics. Jolly advised Planck against going into theoretical physics; Planck recalls that in 1878, Jolly argued that physics was almost complete, being a "highly developed, nearly fully matured science, that through the crowning achievement of the discovery of the principle of conservation of energy will arguably soon take its final stable form".
In 1877, Planck went to the University of Berlin for a year of study with physicists Hermann von Helmholtz and Gustav Kirchhoff and mathematician Karl Weierstrass. He wrote that Helmholtz was never quite prepared, spoke slowly, miscalculated endlessly, and bored his listeners, while Kirchhoff spoke in carefully prepared lectures which were dry and monotonous. He soon became a close friend with Helmholtz. While there he undertook a program of mostly self-study of Rudolf Clausius' writings, which led him to choose thermodynamics as his field.
In October 1878, Planck passed his qualifying exams and in February 1879 defended his thesis Über den zweiten Hauptsatz der mechanischen Wärmetheorie. He briefly taught mathematics and physics at his former school in Munich.
By the year 1880, Planck had obtained the two highest academic degrees offered in Europe. The first was a doctorate degree after he completed his paper detailing his research and theory of thermodynamics. He then presented his venia legendi thesis titled Gleichgewichtszustände isotroper Körper in verschiedenen Temperaturen.

Career and research

In 1880, Planck became a Privatdozent at Munich, waiting until he was offered an academic position. Although he was initially ignored by the academic community, he furthered his work on the field of heat theory and discovered one after another the same thermodynamical formalism as Gibbs without realizing it. Clausius' ideas on entropy occupied a central role in his work.
In April 1885, Planck was appointed Associate Professor of Theoretical Physics at the University of Kiel. Further work on entropy and its treatment, especially as applied in physical chemistry, followed. He published his Treatise on Thermodynamics in 1897. He proposed a thermodynamic basis for Svante Arrhenius's theory of electrolytic dissociation.
In 1889, Planck was named the successor to Kirchhoff's position at the University of Berlin – presumably thanks to Helmholtz's intercession – and by 1892 became Full Professor. In 1907, he was offered Ludwig Boltzmann's position in Vienna, but turned it down to stay in Berlin. During 1909, as a University of Berlin professor, he was invited to become the Ernest Kempton Adams Lecturer in Theoretical Physics at Columbia University in New York City. A series of his lectures were translated and co-published by Columbia University professor A. P. Wills. He was elected to the American Academy of Arts and Sciences in 1914. He retired from Berlin on 10 January 1926, and was succeeded by Erwin Schrödinger. He was elected to the National Academy of Sciences in 1926 and to the American Philosophical Society in 1933.

Professor at Berlin University

As a professor at the University of Berlin, Planck joined the local Physical Society. He later wrote about this time: "In those days I was essentially the only theoretical physicist there, whence things were not so easy for me, because I started mentioning entropy, but this was not quite fashionable, since it was regarded as a mathematical spook". Thanks to his initiative, the various local Physical Societies of Germany merged in 1898 to form the German Physical Society ; from 1905 to 1909 Planck was the president.
Planck started a six-semester course of lectures on theoretical physics, "dry, somewhat impersonal" according to Lise Meitner, "using no notes, never making mistakes, never faltering; the best lecturer I ever heard" according to an English participant, James R. Partington, who continues: "There were always many standing around the room. As the lecture-room was well heated and rather close, some of the listeners would from time to time drop to the floor, but this did not disturb the lecture." Planck did not establish an actual "school"; the number of his graduate students was only about 20, among them:

, also known as the "mechanical theory of heat" at the end of the 19th century, had emerged at the beginning of this century from an attempt to understand the functioning of steam engines and to improve their efficiency. In the 1840s, several researchers independently discovered and formulated the law of conservation of energy, which is now also known as the first law of thermodynamics. In 1850, Rudolf Clausius formulated the so-called second law of thermodynamics, which states that a voluntary transfer of energy is only possible from a warmer to a colder body, but not vice versa. In England at this time William Thomson came to the same conclusion.
Clausius generalized his formulation further and further and came up with a new formulation in 1865. To this end, he introduced the concept of entropy, which he defined as a measure of the reversible supply of heat in relation to the absolute temperature.
The new formulation of the second law, which is still valid today, was: "Entropy can be created, but never destroyed". Clausius, whose work Planck read as a young student during his stay in Berlin, successfully applied this new law of nature to mechanical, thermoelectric and chemical processes.
In his thesis in 1879, Planck summarized Clausius' writings, pointing out contradictions and inaccuracies in their formulation and then clarifying them. In addition, he generalized the validity of the second law to all processes in nature; Clausius had limited its application to reversible processes and thermal processes. Furthermore, Planck dealt intensively with the new concept of entropy and emphasized that entropy is not only a property of a physical system, but at the same time a measure of the irreversibility of a process: If entropy is generated in a process, it is irreversible, since entropy cannot be destroyed according to the second law. In reversible processes, the entropy remains constant. He presented this fact in detail in 1887 in a series of treatises entitled "On the Principle of the Increase of Entropy".
In his study of the concept of entropy, Planck did not follow the molecular, probabilistic interpretation that prevailed at the time, as these do not provide absolute proof of universality. Instead, he pursued a phenomenological approach and was also skeptical of atomism. Even though he later abandoned this attitude in the course of his work on the law of radiation, his early work impressively shows the possibilities of thermodynamics in solving concrete physicochemical problems.
Planck's understanding of entropy included the realization that the maximum of entropy corresponds to the equilibrium state. The accompanying conclusion that knowledge of the Entropy allows all laws of thermodynamic equilibrium states to be derived corresponds to the modern understanding of such states. Planck therefore chose equilibrium processes as his research focus and, based on his habilitation thesis, researched the coexistence of aggregate states and the equilibrium of gas reactions, for example. This work on the frontier of chemical thermodynamics also received great attention due to the rapidly expanding chemical work at that time.
Independently of Planck, Josiah Willard Gibbs had also discovered almost all the knowledge Planck gained about the properties of physicochemical equilibria and published them from 1876 onwards. Planck was unaware of these essays, and they did not appear in German until 1892. However, both scientists approached the topic in different ways, while Planck dealt with irreversible processes, Gibbs looked at equilibria. This approach was finally able to prevail because of its simplicity, but Planck's approach is attributed the greater universality.