Max Karl Ernst Ludwig Planck (; ; 23 April 1858 – 4 October 1947) was a German
theoretical physicist whose discovery of energy
quanta won him the
Nobel Prize in Physics in 1918.
Planck made many substantial contributions to theoretical physics, but his fame as a physicist rests primarily on his role as the originator of
quantum theory and one of the founders of
modern physics, which revolutionized understanding of
atom
Atoms are the basic particles of the chemical elements. An atom consists of a atomic nucleus, nucleus of protons and generally neutrons, surrounded by an electromagnetically bound swarm of electrons. The chemical elements are distinguished fr ...
ic and
subatomic processes. He is known for the
Planck constant
The Planck constant, or Planck's constant, denoted by h, is a fundamental physical constant of foundational importance in quantum mechanics: a photon's energy is equal to its frequency multiplied by the Planck constant, and the wavelength of a ...
, which is of foundational importance for quantum physics, and which he used to derive a set of
units, today called
Planck units, expressed only in terms of fundamental
physical constants.
Planck was twice president of the German scientific institution
Kaiser Wilhelm Society. In 1948, it was renamed the
Max Planck Society (Max-Planck-Gesellschaft) and nowadays includes 83 institutions representing a wide range of scientific directions.
Early life and education
Planck came from a traditional, intellectual family. His paternal great-grandfather and grandfather were both theology professors in
Göttingen
Göttingen (, ; ; ) is a college town, university city in Lower Saxony, central Germany, the Capital (political), capital of Göttingen (district), the eponymous district. The River Leine runs through it. According to the 2022 German census, t ...
; his father was a law professor at the
University of Kiel and
Munich
Munich is the capital and most populous city of Bavaria, Germany. As of 30 November 2024, its population was 1,604,384, making it the third-largest city in Germany after Berlin and Hamburg. Munich is the largest city in Germany that is no ...
. One of his uncles was also a judge.
Planck was born in 1858 in
Kiel
Kiel ( ; ) is the capital and most populous city in the northern Germany, German state of Schleswig-Holstein. With a population of around 250,000, it is Germany's largest city on the Baltic Sea. It is located on the Kieler Förde inlet of the Ba ...
,
Holstein (now
Schleswig-Holstein
Schleswig-Holstein (; ; ; ; ; occasionally in English ''Sleswick-Holsatia'') is the Northern Germany, northernmost of the 16 states of Germany, comprising most of the historical Duchy of Holstein and the southern part of the former Duchy of S ...
), to 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
Karl Marx (; 5 May 1818 – 14 March 1883) was a German philosopher, political theorist, economist, journalist, and revolutionary socialist. He is best-known for the 1848 pamphlet '' The Communist Manifesto'' (written with Friedrich Engels) ...
'' 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.
He 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
The Second Schleswig War (; or German Danish War), also sometimes known as the Dano-Prussian War or Prusso-Danish War, was the second military conflict over the Schleswig–Holstein question of the nineteenth century. The war began on 1 Februar ...
in 1864.
In 1867 the family moved to
Munich
Munich is the capital and most populous city of Bavaria, Germany. As of 30 November 2024, its population was 1,604,384, making it the third-largest city in Germany after Berlin and Hamburg. Munich is the largest city in Germany that is no ...
, and Planck enrolled in the Maximilians
gymnasium school. 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
Astronomy is a natural science that studies celestial objects and the phenomena that occur in the cosmos. It uses mathematics, physics, and chemistry in order to explain their origin and their overall evolution. Objects of interest includ ...
and
mechanics
Mechanics () is the area of physics concerned with the relationships between force, matter, and motion among Physical object, physical objects. Forces applied to objects may result in Displacement (vector), displacements, which are changes of ...
as well as
mathematics
Mathematics is a field of study that discovers and organizes methods, Mathematical theory, theories and theorems that are developed and Mathematical proof, proved for the needs of empirical sciences and mathematics itself. There are many ar ...
. It was from Müller that Planck first learned the principle of conservation of energy. Planck graduated early, at age 17. This is how Planck first came in contact with the field of physics.
Planck was gifted when it came to
music
Music is the arrangement of sound to create some combination of Musical form, form, harmony, melody, rhythm, or otherwise Musical expression, expressive content. Music is generally agreed to be a cultural universal that is present in all hum ...
. He took singing lessons and played piano, organ and cello, and composed songs and operas. However, instead of music he chose to study
physics
Physics is the scientific study of matter, its Elementary particle, fundamental constituents, its motion and behavior through space and time, and the related entities of energy and force. "Physical science is that department of knowledge whi ...
.
Planck enrolled at the
University of Munich in 1874. Under professor
Philipp von Jolly's supervision, Planck performed the only experiments of his scientific career, studying the
diffusion
Diffusion is the net movement of anything (for example, atoms, ions, molecules, energy) generally from a region of higher concentration to a region of lower concentration. Diffusion is driven by a gradient in Gibbs free energy or chemical p ...
of
hydrogen
Hydrogen is a chemical element; it has chemical symbol, symbol H and atomic number 1. It is the lightest and abundance of the chemical elements, most abundant chemical element in the universe, constituting about 75% of all baryon, normal matter ...
through heated
platinum
Platinum is a chemical element; it has Symbol (chemistry), symbol Pt and atomic number 78. It is a density, dense, malleable, ductility, ductile, highly unreactive, precious metal, precious, silverish-white transition metal. Its name origina ...
, but transferred to
theoretical physics
Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain, and predict List of natural phenomena, natural phenomena. This is in contrast to experimental p ...
. 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, he went to the
Friedrich Wilhelms University in Berlin for a year of study with physicists
Hermann von Helmholtz
Hermann Ludwig Ferdinand von Helmholtz (; ; 31 August 1821 – 8 September 1894; "von" since 1883) was a German physicist and physician who made significant contributions in several scientific fields, particularly hydrodynamic stability. The ...
and
Gustav Kirchhoff and mathematician
Karl Weierstrass
Karl Theodor Wilhelm Weierstrass (; ; 31 October 1815 – 19 February 1897) was a German mathematician often cited as the " father of modern analysis". Despite leaving university without a degree, he studied mathematics and trained as a school t ...
. 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's writings, which led him to choose
thermodynamics
Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed b ...
as his field.
In October 1878, Planck passed his qualifying exams and in February 1879 defended his dissertation ''Über den zweiten Hauptsatz der mechanischen Wärmetheorie'' (''On the Second Law of Mechanical Heat Theory''). 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 thesis called ''Gleichgewichtszustände isotroper Körper in verschiedenen Temperaturen'' (''Equilibrium states of isotropic bodies at different temperatures''), which earned him a
habilitation.
Career

With the completion of his habilitation thesis, Planck became an unpaid
Privatdozent (German academic rank comparable to lecturer/assistant professor) in 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's ideas on
entropy
Entropy is a scientific concept, most commonly associated with states of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynamics, where it was first recognized, to the micros ...
occupied a central role in his work.
In April 1885, the
University of Kiel appointed Planck as associate professor of
theoretical physics
Theoretical physics is a branch of physics that employs mathematical models and abstractions of physical objects and systems to rationalize, explain, and predict List of natural phenomena, natural phenomena. This is in contrast to experimental p ...
. Further work on entropy and its treatment, especially as applied in
physical chemistry
Physical chemistry is the study of macroscopic and microscopic phenomena in chemical systems in terms of the principles, practices, and concepts of physics such as motion, energy, force, time, thermodynamics, quantum chemistry, statistical mech ...
, followed. He published his ''Treatise on Thermodynamics'' in 1897. He proposed a thermodynamic basis for
Svante Arrhenius
Svante August Arrhenius ( , ; 19 February 1859 – 2 October 1927) was a Swedish scientist. Originally a physicist, but often referred to as a chemist, Arrhenius was one of the founders of the science of physical chemistry. In 1903, he received ...
's theory of
electrolytic dissociation.
In 1889, he was named the successor to Kirchhoff's position at the
Friedrich-Wilhelms-Universität in Berlin – presumably thanks to Helmholtz's intercession – and by 1892 became a full professor. In 1907 Planck was offered
Ludwig Boltzmann
Ludwig Eduard Boltzmann ( ; ; 20 February 1844 – 5 September 1906) was an Austrian mathematician and Theoretical physics, theoretical physicist. His greatest achievements were the development of statistical mechanics and the statistical ex ...
's position in
Vienna
Vienna ( ; ; ) is the capital city, capital, List of largest cities in Austria, most populous city, and one of Federal states of Austria, nine federal states of Austria. It is Austria's primate city, with just over two million inhabitants. ...
, 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
Columbia University in the City of New York, commonly referred to as Columbia University, is a Private university, private Ivy League research university in New York City. Established in 1754 as King's College on the grounds of Trinity Churc ...
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
The American Academy of Arts and Sciences (The Academy) is one of the oldest learned societies in the United States. It was founded in 1780 during the American Revolution by John Adams, John Hancock, James Bowdoin, Andrew Oliver, and other ...
in 1914. He retired from Berlin on 10 January 1926, and was succeeded by
Erwin Schrödinger
Erwin Rudolf Josef Alexander Schrödinger ( ; ; 12 August 1887 – 4 January 1961), sometimes written as or , was an Austrian-Irish theoretical physicist who developed fundamental results in quantum field theory, quantum theory. In particul ...
. He was elected to the United States
National Academy of Sciences
The National Academy of Sciences (NAS) is a United States nonprofit, NGO, non-governmental organization. NAS is part of the National Academies of Sciences, Engineering, and Medicine, along with the National Academy of Engineering (NAE) and the ...
in 1926 and the
American Philosophical Society
The American Philosophical Society (APS) is an American scholarly organization and learned society founded in 1743 in Philadelphia that promotes knowledge in the humanities and natural sciences through research, professional meetings, publicat ...
in 1933.
Professor at Berlin University
As a professor at the
Friedrich-Wilhelms-Universität in 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 (
Deutsche Physikalische Gesellschaft, DPG); 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
Elise Lise Meitner ( ; ; 7 November 1878 – 27 October 1968) was an Austrian-Swedish nuclear physicist who was instrumental in the discovery of nuclear fission.
After completing her doctoral research in 1906, Meitner became the second woman ...
, "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:
* 1897
Max Abraham (1875–1922)
* 1903
Max von Laue (1879–1960)
* 1904
Moritz Schlick (1882–1936)
* 1906
Walther Meissner (1882–1974)
* 1907
Fritz Reiche (1883–1960)
* 1912
Walter Schottky (1886–1976)
* 1914
Walther Bothe (1891–1957)
Entropy
Thermodynamics
Thermodynamics is a branch of physics that deals with heat, Work (thermodynamics), work, and temperature, and their relation to energy, entropy, and the physical properties of matter and radiation. The behavior of these quantities is governed b ...
, 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
The first law of thermodynamics is a formulation of the law of conservation of energy in the context of thermodynamic processes. For a thermodynamic process affecting a thermodynamic system without transfer of matter, the law distinguishes two ...
. In 1850,
Rudolf Clausius formulated the so-called
second law of thermodynamics
The second law of thermodynamics is a physical law based on Universal (metaphysics), universal empirical observation concerning heat and Energy transformation, energy interconversions. A simple statement of the law is that heat always flows spont ...
, which states that a voluntary (or spontaneous) 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
Entropy is a scientific concept, most commonly associated with states of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynamics, where it was first recognized, to the micros ...
, 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 dissertation 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.
[Hoffmann: ''Max Planck.'' Munich 2008, p. 29.][Hartmann: ''Max Planck als Mensch und Denker.'' 3. revised edition, Basel 1953, p. 156.]
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.
Black-body radiation

In 1894, Planck turned his attention to the problem of
black-body radiation. The problem had been stated by Kirchhoff in 1859: "how does the intensity of the electromagnetic radiation emitted by a
black body (a perfect absorber, also known as a cavity radiator) depend on the
frequency
Frequency is the number of occurrences of a repeating event per unit of time. Frequency is an important parameter used in science and engineering to specify the rate of oscillatory and vibratory phenomena, such as mechanical vibrations, audio ...
of the radiation (i.e., the color of the light) and the temperature of the body?". The question had been explored experimentally, but no theoretical treatment had agreed with the experimentally observed evidence.
Wilhelm Wien proposed
Wien's law, which correctly predicted the behaviour at high frequencies, but failed at low frequencies. The
Rayleigh–Jeans law, another approach to the problem, agreed with experimental results at low frequencies, but created what was later known as the "
ultraviolet catastrophe" at high frequencies, as predicted by
classical physics
Classical physics refers to physics theories that are non-quantum or both non-quantum and non-relativistic, depending on the context. In historical discussions, ''classical physics'' refers to pre-1900 physics, while '' modern physics'' refers to ...
. However, contrary to many textbooks, this was not a motivation for Planck.
[For a solid approach to the complexity of Planck's intellectual motivations for the quantum, for his reluctant acceptance of its implications, see Helge Kragh,]
Max Planck: the reluctant revolutionary
, ''Physics World''. December 2000.
Planck's first proposed solution to the problem in 1899 followed from what he called the "principle of elementary disorder", which allowed him to derive Wien's law from a number of assumptions about the
entropy
Entropy is a scientific concept, most commonly associated with states of disorder, randomness, or uncertainty. The term and the concept are used in diverse fields, from classical thermodynamics, where it was first recognized, to the micros ...
of an ideal oscillator, creating what was referred to as the Wien–Planck law. Soon, however, it was found that experimental evidence did not confirm the new law at all, to Planck's frustration. He revised his approach and now derived the first version of the famous
Planck black-body radiation law, which described clearly the experimentally observed black-body spectrum. It was first proposed in a meeting of the DPG on 19 October 1900 and published in 1901. (This first derivation did not include energy quantisation, and did not use
statistical mechanics
In physics, statistical mechanics is a mathematical framework that applies statistical methods and probability theory to large assemblies of microscopic entities. Sometimes called statistical physics or statistical thermodynamics, its applicati ...
, to which he held an aversion.) In November 1900 Planck revised this first version, now relying on
Boltzmann's statistical interpretation of the
second law of thermodynamics
The second law of thermodynamics is a physical law based on Universal (metaphysics), universal empirical observation concerning heat and Energy transformation, energy interconversions. A simple statement of the law is that heat always flows spont ...
as a way of gaining a more fundamental understanding of the principles behind his radiation law. Planck was deeply suspicious of the philosophical and physical implications of such an interpretation of Boltzmann's approach; thus his recourse to them was, as he later put it, "an act of despair ... I was ready to sacrifice any of my previous convictions about physics".
The central assumption behind his new derivation, presented to the DPG on 14 December 1900, was the supposition, now known as the
Planck postulate, that electromagnetic energy could be emitted only in
quantized form, in other words, the energy could only be a multiple of an elementary unit:
:
where is the
Planck constant
The Planck constant, or Planck's constant, denoted by h, is a fundamental physical constant of foundational importance in quantum mechanics: a photon's energy is equal to its frequency multiplied by the Planck constant, and the wavelength of a ...
, also known as Planck's action quantum (introduced already in 1899), and is the frequency of the radiation. Note that the elementary units of energy discussed here are represented by and not simply by . Physicists now call these quanta photons, and a photon of frequency will have its own specific and unique energy. The total energy at that frequency is then equal to multiplied by the number of photons at that frequency.

At first Planck considered that quantisation was only "a purely formal assumption ... actually I did not think much about it ..."; nowadays this assumption, incompatible with
classical physics
Classical physics refers to physics theories that are non-quantum or both non-quantum and non-relativistic, depending on the context. In historical discussions, ''classical physics'' refers to pre-1900 physics, while '' modern physics'' refers to ...
, is regarded as the birth of
quantum physics
Quantum mechanics is the fundamental physical Scientific theory, theory that describes the behavior of matter and of light; its unusual characteristics typically occur at and below the scale of atoms. Reprinted, Addison-Wesley, 1989, It is ...
and the greatest intellectual accomplishment of Planck's career. (
Boltzmann had been discussing in a theoretical paper in 1877 the possibility that the energy states of a physical system could be discrete). The discovery of the Planck constant enabled him to define a new universal set of
physical units
A unit of measurement, or unit of measure, is a definite magnitude of a quantity, defined and adopted by convention or by law, that is used as a standard for measurement of the same kind of quantity. Any other quantity of that kind can ...
(such as the Planck length and the Planck mass), all based on fundamental physical constants, upon which much of quantum theory is based. In a discussion with his son in December 1918 Planck described his discovery as 'a discovery of the first rank, comparable perhaps only to the discoveries of Newton'. In recognition of Planck's fundamental contribution to a new branch of physics, he was awarded the Nobel Prize in Physics for 1918; (he received the award in 1919).
Subsequently, Planck tried to grasp the meaning of energy quanta, but to no avail. "My unavailing attempts to somehow reintegrate the action quantum into classical theory extended over several years and caused me much trouble." Even several years later, other physicists such as
Rayleigh,
Jeans, and
Lorentz set the Planck constant to zero in order to align with classical physics, but Planck knew well that this constant had a precise nonzero value. "I am unable to understand Jeans' stubbornness – he is an example of a theoretician as should never be existing, the same as
Hegel was for philosophy. So much the worse for the facts if they don't fit."
Max Born
Max Born (; 11 December 1882 – 5 January 1970) was a German-British theoretical physicist who was instrumental in the development of quantum mechanics. He also made contributions to solid-state physics and optics, and supervised the work of a ...
wrote about Planck: "He was, by nature, a conservative mind; he had nothing of the revolutionary and was thoroughly skeptical about speculations. Yet his belief in the compelling force of logical reasoning from facts was so strong that he did not flinch from announcing the most revolutionary idea which ever has shaken physics."
Einstein and the theory of relativity
In 1905, three papers by
Albert Einstein
Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence f ...
were published in the journal ''
Annalen der Physik''. Planck was among the few who immediately recognized the significance of the
special theory of relativity. Thanks to his influence, this theory was soon widely accepted in Germany. Planck also contributed considerably to extend the special theory of relativity. For example, he recast the theory in terms of classical
action.
Einstein's hypothesis of light ''quanta'' (
photons), based on
Heinrich Hertz's 1887 discovery (and further investigation by
Philipp Lenard) of the
photoelectric effect, was initially rejected by Planck. He was unwilling to discard completely
Maxwell
Maxwell may refer to:
People
* Maxwell (surname), including a list of people and fictional characters with the name
** James Clerk Maxwell, mathematician and physicist
* Justice Maxwell (disambiguation)
* Maxwell baronets, in the Baronetage of N ...
's theory of
electrodynamics. "The theory of light would be thrown back not by decades, but by centuries, into the age when
Christiaan Huygens
Christiaan Huygens, Halen, Lord of Zeelhem, ( , ; ; also spelled Huyghens; ; 14 April 1629 – 8 July 1695) was a Dutch mathematician, physicist, engineer, astronomer, and inventor who is regarded as a key figure in the Scientific Revolution ...
dared to fight against the mighty emission theory of
Isaac Newton
Sir Isaac Newton () was an English polymath active as a mathematician, physicist, astronomer, alchemist, theologian, and author. Newton was a key figure in the Scientific Revolution and the Age of Enlightenment, Enlightenment that followed ...
..."
In 1910, Einstein pointed out the anomalous behavior of
specific heat at low temperatures as another example of a phenomenon which defies explanation by classical physics. Planck and
Walther Nernst, seeking to clarify the increasing number of contradictions, organized the First
Solvay Conference (Brussels 1911). At this meeting Einstein was able to convince Planck.
Meanwhile, Planck had been appointed dean of Berlin University, whereby it was possible for him to call Einstein to Berlin and establish a new professorship for him (1914). Soon the two scientists became close friends and met frequently to play music together.
First World War
At the onset of the
First World War
World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
Planck endorsed the general excitement of the public, writing that, "Besides much that is horrible, there is also much that is unexpectedly great and beautiful: the smooth solution of the most difficult domestic political problems by the unification of all parties (and) ... the extolling of everything good and noble." Planck also signed the infamous "
Manifesto of the 93 intellectuals", a pamphlet of polemic war propaganda (while Einstein retained a strictly pacifistic attitude which almost led to his imprisonment, only being spared thanks to his
Swiss
Swiss most commonly refers to:
* the adjectival form of Switzerland
* Swiss people
Swiss may also refer to: Places
* Swiss, Missouri
* Swiss, North Carolina
* Swiss, West Virginia
* Swiss, Wisconsin
Other uses
* Swiss Café, an old café located ...
citizenship).
In 1915, when Italy was still a neutral power, Planck voted successfully for a scientific paper from Italy, which received a prize from the
Prussian Academy of Sciences, where Planck was one of four permanent presidents.
Post-war and the Weimar Republic
In the turbulent post-war years, Planck, now the highest authority of German physics, issued the slogan "persevere and continue working" to his colleagues.
In October 1920, he and
Fritz Haber established the ''
Notgemeinschaft der Deutschen Wissenschaft'' (Emergency Organization of German Science), aimed at providing financial support for scientific research. A considerable portion of the money the organization would distribute was raised abroad.
Planck held leading positions at Berlin University, the Prussian Academy of Sciences, the German Physical Society, and the
Kaiser Wilhelm Society (which became the
Max Planck Society in 1948). During this time economic conditions in Germany were such that he was hardly able to conduct research. In 1926, Planck became a foreign member of the
Royal Netherlands Academy of Arts and Sciences.
During the interwar period, Planck became a member of the Deutsche Volks-Partei (
German People's Party), the party of Nobel Peace Prize laureate
Gustav Stresemann
Gustav Ernst Stresemann (; 10 May 1878 – 3 October 1929) was a German statesman during the Weimar Republic who served as Chancellor of Germany#First German Republic (Weimar Republic, 1919–1933), chancellor of Germany from August to November 1 ...
, which aspired to liberal aims for domestic policy and rather revisionistic aims for politics around the world.
Planck disagreed with the introduction of
universal suffrage
Universal suffrage or universal franchise ensures the right to vote for as many people bound by a government's laws as possible, as supported by the " one person, one vote" principle. For many, the term universal suffrage assumes the exclusion ...
and later expressed the view that the Nazi dictatorship resulted from "the ascent of the rule of the crowds".
Quantum mechanics
At the end of the 1920s,
Niels Bohr
Niels Henrik David Bohr (, ; ; 7 October 1885 – 18 November 1962) was a Danish theoretical physicist who made foundational contributions to understanding atomic structure and old quantum theory, quantum theory, for which he received the No ...
,
Werner Heisenberg
Werner Karl Heisenberg (; ; 5 December 1901 – 1 February 1976) was a German theoretical physicist, one of the main pioneers of the theory of quantum mechanics and a principal scientist in the German nuclear program during World War II.
He pub ...
, and
Wolfgang Pauli had worked out the
Copenhagen interpretation of quantum mechanics, but it was rejected by Planck, and by Schrödinger, Laue, and Einstein as well. Planck expected that
wave mechanics would soon render quantum theory his own child unnecessary. This was not to be the case, however. Further work only served to underscore the enduring central importance of quantum theory, even against his and Einstein's philosophical revulsions. Here Planck experienced the truth of his own earlier observation from his struggle with the older views during his younger years: "A new scientific truth does not triumph by convincing its opponents and making them see the light, but rather because its opponents eventually die, and a new generation grows up that is familiar with it."
Nazi dictatorship and the Second World War
When the Nazis came to power in 1933, Planck was 74 years old. He witnessed many Jewish friends and colleagues expelled from their positions and humiliated, and hundreds of scientists emigrate from
Nazi Germany
Nazi Germany, officially known as the German Reich and later the Greater German Reich, was the German Reich, German state between 1933 and 1945, when Adolf Hitler and the Nazi Party controlled the country, transforming it into a Totalit ...
. Again he tried to "persevere and continue working" and asked scientists who were considering emigration to remain in Germany. Nevertheless, he did help his nephew, the economist
Hermann Kranold, to emigrate to
London
London is the Capital city, capital and List of urban areas in the United Kingdom, largest city of both England and the United Kingdom, with a population of in . London metropolitan area, Its wider metropolitan area is the largest in Wester ...
after his arrest.
He hoped the crisis would abate soon and the political situation would improve.
Otto Hahn asked Planck to gather well-known German professors in order to issue a public proclamation against the treatment of Jewish professors, but Planck replied, "If you are able to gather today 30 such gentlemen, then tomorrow 150 others will come and speak against it, because they are eager to take over the positions of the others." Under Planck's leadership, the
Kaiser Wilhelm Society (KWG) avoided open conflict with the Nazi regime, except concerning the Jewish Fritz Haber. In May 1933 Planck requested and received an interview with the recently appointed Chancellor of Germany
Adolf Hitler
Adolf Hitler (20 April 1889 – 30 April 1945) was an Austrian-born German politician who was the dictator of Nazi Germany from 1933 until Death of Adolf Hitler, his suicide in 1945. Adolf Hitler's rise to power, He rose to power as the lea ...
to discuss the issue, telling him that the "forced emigration of Jews would kill German science and Jews could be good Germans", to which the chancellor replied "but we don't have anything against the Jews, only against communists". Planck was therefore unsuccessful, since this reply "took from him every basis for further negotiation", as to Hitler "the Jews are all Communists, and these are my enemies." In the following year, 1934, Haber died in exile.
One year later, Planck, having been the president of the KWG since 1930, organized in a somewhat provocative style an official commemorative meeting for Haber. He also succeeded in secretly enabling a number of Jewish scientists to continue working in institutes of the KWG for several years. In 1936, his term as president of the KWG ended, and the Nazi government pressured him to refrain from seeking another term.
As the political climate in Germany gradually became more hostile,
Johannes Stark, prominent exponent of the ''
Deutsche Physik'' ("German Physics", also called "Aryan Physics") attacked Planck,
Arnold Sommerfeld, and Heisenberg for continuing to teach the theories of Einstein, calling them "white Jews". The "Hauptamt Wissenschaft" (Nazi government office for science) started an investigation of Planck's ancestry, claiming that he was "1/16 Jewish", but Planck denied it.
In 1938, Planck celebrated his 80th birthday. The DPG held a celebration, during which the Max-Planck medal (founded as the highest medal by the DPG in 1928) was awarded to French physicist
Louis de Broglie. At the end of 1938, the Prussian Academy lost its remaining independence and was taken over by Nazis, as part of their process of ''
Gleichschaltung''. Planck protested by resigning his presidency. He continued to travel frequently, giving numerous public talks, such as his talk on Religion and Science and, five years later, he was sufficiently fit to climb 3,000-metre peaks in the
Alps
The Alps () are some of the highest and most extensive mountain ranges in Europe, stretching approximately across eight Alpine countries (from west to east): Monaco, France, Switzerland, Italy, Liechtenstein, Germany, Austria and Slovenia.
...
.
During the
Second World War
World War II or the Second World War (1 September 1939 – 2 September 1945) was a World war, global conflict between two coalitions: the Allies of World War II, Allies and the Axis powers. World War II by country, Nearly all of the wo ...
, the increasing number of Allied bombing missions against Berlin forced Planck and his wife to temporarily leave the city and live in the countryside. In 1942, he wrote: "In me an ardent desire has grown to persevere this crisis and live long enough to be able to witness the turning point, the beginning of a new rise." In February 1944, his home in Berlin was completely destroyed by an air raid, annihilating all his scientific records and correspondence. His rural retreat was threatened by the rapid advance of the Allied armies from both sides.
In 1944, Planck's son
Erwin was arrested by the
Gestapo
The (, ), Syllabic abbreviation, abbreviated Gestapo (), was the official secret police of Nazi Germany and in German-occupied Europe.
The force was created by Hermann Göring in 1933 by combining the various political police agencies of F ...
following the attempted assassination of Hitler in the . He was tried and sentenced to death by the
People's Court in October 1944. Erwin was hanged at Berlin's
Plötzensee Prison in January 1945. The death of his son destroyed much of Planck's will to live.
Personal life and death
In March 1887, Planck married Marie Merck (1861–1909), sister of a school fellow, and moved with her into a sublet apartment in Kiel. They had four children: Karl (1888–1916), the twins Emma (1889–1919) and Grete (1889–1917), and
Erwin (1893–1945).
After living in the apartment in Berlin, the Planck family lived in a villa in Berlin-Grunewald, Wangenheimstrasse 21. Several other professors from
University of Berlin lived nearby, among them theologian
Adolf von Harnack, who became a close friend of Planck. Soon the Planck home became a social and cultural center. Numerous well-known scientists, such as
Albert Einstein
Albert Einstein (14 March 187918 April 1955) was a German-born theoretical physicist who is best known for developing the theory of relativity. Einstein also made important contributions to quantum mechanics. His mass–energy equivalence f ...
,
Otto Hahn and
Lise Meitner
Elise Lise Meitner ( ; ; 7 November 1878 – 27 October 1968) was an Austrian-Swedish nuclear physicist who was instrumental in the discovery of nuclear fission.
After completing her doctoral research in 1906, Meitner became the second woman ...
were frequent visitors. The tradition of jointly performing music had already been established in the home of
Helmholtz.
After several happy years, in July 1909 Marie Planck died, possibly from
tuberculosis
Tuberculosis (TB), also known colloquially as the "white death", or historically as consumption, is a contagious disease usually caused by ''Mycobacterium tuberculosis'' (MTB) bacteria. Tuberculosis generally affects the lungs, but it can al ...
.
In March 1911 Planck married his second wife, Marga von Hoesslin (1882–1948); in December his fifth child Hermann was born.
During the
First World War
World War I or the First World War (28 July 1914 – 11 November 1918), also known as the Great War, was a World war, global conflict between two coalitions: the Allies of World War I, Allies (or Entente) and the Central Powers. Fighting to ...
Planck's second son Erwin was taken prisoner by the French in 1914, while his oldest son Karl was killed in action at
Verdun
Verdun ( , ; ; ; official name before 1970: Verdun-sur-Meuse) is a city in the Meuse (department), Meuse departments of France, department in Grand Est, northeastern France. It is an arrondissement of the department.
In 843, the Treaty of V ...
. Grete died in 1917 while giving birth to her first child. Her sister died the same way two years later, after having married Grete's widower. Both granddaughters survived and were named after their mothers. Planck endured these losses stoically.
In January 1945,
Erwin Planck, to whom he had been particularly close, was sentenced to death by the
Nazi
Nazism (), formally named National Socialism (NS; , ), is the far-right politics, far-right Totalitarianism, totalitarian socio-political ideology and practices associated with Adolf Hitler and the Nazi Party (NSDAP) in Germany. During H ...
Volksgerichtshof because of his participation in the
failed attempt to assassinate Hitler in July 1944. Erwin was executed on 23 January 1945.
After World War II ended, Planck, his second wife, and their son were brought to a relative in
Göttingen
Göttingen (, ; ; ) is a college town, university city in Lower Saxony, central Germany, the Capital (political), capital of Göttingen (district), the eponymous district. The River Leine runs through it. According to the 2022 German census, t ...
, where Planck died on October 4, 1947. He was buried in the old Stadtfriedhof (City Cemetery) in Göttingen.
Religious views

Planck was a member of the
Lutheran Church in Germany. He was very tolerant toward alternative views and
religions.
[. adherents.com. Retrieved on 5 July 2011.] In a lecture in 1937 entitled "Religion und Naturwissenschaft" ("Religion and Natural Science") he suggested the importance of these symbols and rituals related directly with a believer's ability to worship God, but that one must be mindful that the symbols provide an imperfect illustration of divinity. He criticized atheism for being focused on the derision of such symbols, while at the same time warned of the over-estimation of the importance of such symbols by believers.
In "Religion und Naturwissenschaft", Planck expressed the view that God is present everywhere, and he held that "the holiness of the unintelligible Godhead is conveyed by the holiness of symbols." Atheists, he thought, attach too much importance to what are merely symbols. He was a churchwarden from 1920 until his death, and believed in an almighty, all-knowing, beneficent God (although not necessarily a personal one). Both science and religion wage a "tireless battle against skepticism and dogmatism, against unbelief and superstition" with the goal "toward God!"
Planck said in 1944, "As a man who has devoted his whole life to the most clear headed science, to the study of matter, I can tell you as a result of my research about atoms this much: There is no matter as such. All matter originates and exists only by virtue of a force which brings the particle of an atom to vibration and holds this most minute solar system of the atom together. We must assume behind this force the existence of a conscious and intelligent spirit
rig. ''geist'' This spirit is the matrix of all matter."
Planck argued that the concept of God is important to both religion and science, but in different ways: "Both religion and science require a belief in God. For believers, God is in the beginning, and for physicists He is at the end of all considerations … To the former He is the foundation, to the latter, the crown of the edifice of every generalized world view".
Furthermore, Planck wrote,
..."to believe" means "to recognize as a truth", and the knowledge of nature, continually advancing on incontestably safe tracks, has made it utterly impossible for a person possessing some training in natural science to recognize as founded on truth the many reports of extraordinary occurrences contradicting the laws of nature, of miracles which are still commonly regarded as essential supports and confirmations of religious doctrines, and which formerly used to be accepted as facts pure and simple, without doubt or criticism. The belief in miracles must retreat step by step before relentlessly and reliably progressing science and we cannot doubt that sooner or later it must vanish completely.
Noted historian of science
John L. Heilbron characterized Planck's views on God as
deistic. Heilbron further relates that when asked about his religious affiliation, Planck replied that although he had always been deeply religious, he did not believe "in a personal God, let alone a Christian God".
[Heilbron, 2000]
page 198
Publications
* Translated in
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See also
*
List of things named after Max Planck
*
German inventors and discoverers
*
Photon polarization
*
Statue of Max Planck
*
Zero-point energy
Zero-point energy (ZPE) is the lowest possible energy that a quantum mechanical system may have. Unlike in classical mechanics, quantum systems constantly Quantum fluctuation, fluctuate in their lowest energy state as described by the Heisen ...
Notes
References
Sources
*
Aczel, Amir D. ''Entanglement'', Chapter 4. (Penguin, 2003)
*
*
Pickover, Clifford A. ''Archimedes to Hawking: Laws of Science and the Great Minds Behind Them'', Oxford University Press, 2008,
*
* Rosenthal-Schneider, Ilse ''Reality and Scientific Truth: Discussions with Einstein, von Laue, and Planck'' (Wayne State University, 1980)
External links
*
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Annotated bibliography for Max Planckfrom the Alsos Digital Library for Nuclear Issues
Max Planck– Encyclopædia Britannica article
– www.nobel-prize-winners.com
Max Planck Institutes of Natural Science and AstrophysicsMax Planck – Selbstdarstellung im Filmportrait (1942) inematic self-portrait of Max Planck Berlin-Brandenburgische Akademie der Wissenschaften, 1942
* including the Nobel Lecture, 2 June 1920 ''The Genesis and Present State of Development of the Quantum Theory''
Life–Work–Personality– Exhibition on the 50th anniversary of Planck's death
*
{{DEFAULTSORT:Planck, Max
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