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Max Planck

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   CAPTION: Max Planck

   Max Karl Ernst Ludwig Planck
   Max Karl Ernst Ludwig Planck
         Born       April 23, 1858
                    Kiel, Germany
         Died       October 4, 1947
                    Göttingen, Germany
      Residence     Germany
     Nationality    German
        Field       Physicist
     Institution    University of Kiel
                    Humboldt-Universität zu Berlin
                    Georg-August-Universität Göttingen
      Alma Mater    Ludwig-Maximilians-Universität München
   Academic Advisor Philipp von Jolly
   Notable Students Gustav Hertz

                    Erich Kretschmann
                    Walther Meißner
                    Walter Schottky
                    Max von Laue
                    Max Abraham
                    Moritz Schlick
                    Walther Bothe
      Known for     Planck's constant, quantum theory
    Notable Prizes  Nobel Prize in Physics (1918)
   He is the father of Erwin Planck.

   Max Karl Ernst Ludwig Planck ( April 23 in Kiel, Germany, 1858 –
   October 4, 1947 in Göttingen, Germany) was a German physicist. He is
   considered to be the founder of quantum theory, and therefore regarded
   as one of the most important physicists of the twentieth century.

Life and work

Childhood and youth

   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 in Kiel and Munich, and his
   paternal uncle was a judge.

   Max Planck was born in Kiel to Johann Julius Wilhelm Planck and his
   second wife, Emma Patzig. He was the sixth child in the family, though
   two of his siblings were from his father's first marriage. Among his
   earliest memories was the marching-in of Prussian and Austrian troops
   into Kiel during the Danish-Prussian war 1864. In 1867 the family moved
   to Munich, and Planck was enrolled in Munich's Königliches Maximilians
   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 conservation of energy. Planck
   graduated early, at age of sixteen.

Education

   Planck was extremely gifted when it came to music: he took singing
   lessons in addition to playing the piano, organ and cello, and
   composing songs and operas. However, instead of music he chose to study
   physics.

   The Munich physics professor Philipp von Jolly advised him against
   going into physics, saying, "in this field, almost everything is
   already discovered, and all that remains is to fill a few holes."
   Planck replied that he did not wish to discover new things, only to
   understand the known fundamentals of the field, and began his studies
   in 1874 at the University of Munich. Under Jolly's supervision, Planck
   performed the only actual experiments of his scientific career
   (studying the diffusion of hydrogen through heated platinum), but soon
   transferred to theoretical physics.

   In 1877 he went to Berlin for a year of study with the famous
   physicists Hermann von Helmholtz and Gustav Kirchhoff and also the
   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, however, dry and monotonous. Despite this he soon became close
   friends with Helmholtz. While there he mostly undertook a program of
   self-study of Clausius's writings, which led him to choose heat theory
   as his field.

   In October 1878 Planck passed his qualifying exams and in February of
   1879 defended his dissertation, Über den zweiten Hauptsatz der
   mechanischen Wärmetheorie (On the second fundamental theorem of the
   mechanical heat theory). He briefly taught mathematics and physics at
   his former school in Munich.

   In June 1880 he presented his habilitation thesis,
   Gleichgewichtszustände isotroper Körper in verschiedenen Temperaturen
   (Equilibrium states of isotropic bodies at different temperatures).

Academic career

   With the completion of his habilitation thesis, Planck became an unpaid
   private lecturer in Munich, waiting until he would be 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 the other the same thermodynamical formalism as
   Gibbs without realizing it. Clausius's ideas on entropy occupied a
   central role in his work.

   In April 1885 the University of Kiel appointed Planck an associate
   professor of theoretical physics. Further work on entropy and its
   treatment, especially as applied in physical chemistry, followed. He
   proposed a thermodynamic basis for Arrhenius's theory of electrolytic
   dissociation.

   Within four years he was named the successor to Kirchhoff's position at
   the University of Berlin — presumably thanks to Helmholtz's
   intercession — and by 1892 became a full professor. In 1907 Planck was
   appointed to Boltzmann's position in Vienna, but turned it down to stay
   in Berlin. During 1909 he was the Ernest Kempton Adams Lecturer in
   Theoretical Physics at Columbia University in New York City. He retired
   from Berlin on 10 January 1926, and was succeeded by Erwin Schrödinger.

Family

   In March 1887 Planck married Marie Merck (1861-1909), sister of a
   school fellow, and moved with her into a sublet apartment in Kiel. Four
   children were born to the couple: Karl (1888-1916), the twins Emma
   (1889-1919) and Grete (1889-1917), and Erwin Planck (1893-1945).

   After the appointment to Berlin the Planck family lived in a villa in
   Berlin-Grunewald, Wangenheimstraße 21. In the vicinity of this address
   several other professors of Berlin University were living, among them
   the famous theologian Adolf von Harnack, who became a close friend of
   Planck. Soon the Planck home became a social and cultural centre;
   numerous well-known scientists were frequent visitors, such as Albert
   Einstein, Otto Hahn and Lise Meitner. The tradition of jointly playing
   music had already been established in the home of Helmholtz.

   After several happy years the Planck family was struck by a series of
   disasters: in October 1909 Marie Planck died, possibly from
   tuberculosis. In March 1911 Max Planck married his second wife, Marga
   von Hoesslin (1882-1948); in December his third son, Herrmann, was
   born.

   During the First World War Planck's oldest son, Karl, was killed in
   action in Verdun, and Erwin had already in 1914 been taken prisoner by
   the French. Grete died in 1917 while giving birth to her first child;
   her sister lost her life two years later under the same circumstances,
   after marrying Grete's widower. Both granddaughters survived and were
   named after their mothers. Planck endured all these losses with stoic
   submission to fate.

   Finally in January 1945 his youngest son Erwin, to whom Max Planck had
   been particularly close, was executed by the Nazis because of his
   participation in the failed attempt to assassinate Hitler in July 1944.
     * Wives: Marie Merck (m. 1887), Marga von Hoesslin (m. 1910)
     * Children: Karl (1888-1916), twins Emma (1889-1919) and Grete
       (1889-1917), Erwin (1893-1945), Herrmann (b. 1911)

Professor at Berlin University

   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 of the DPG.

   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 twenty all together, among them
   the following:

          Max Abraham 1897 (1875 - 1922)
          Moritz Schlick 1904 (1882 - 1936)
          Walther Meißner 1906 (1882 - 1974)
          Max von Laue 1906 (1879 - 1960)
          Fritz Reiche 1907 (1883 - 1960)
          Walter Schottky 1912 (1886 - 1976)
          Walther Bothe 1914 (1891 - 1957)

Black-body radiation

   In 1894 Planck turned his attention to the problem of black-body
   radiation. He had been commissioned by electric companies to discover
   how to create the most light from lightbulbs with the minimum energy.
   The problem had already 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 of the radiation (e.g., the colour of the light) and the
   temperature of the body? The question had been explored experimentally,
   but the Rayleigh-Jeans law, derived from classical physics, failed to
   explain the observed behaviour at high frequencies, where it predicted
   an unphysical divergence of the energy density towards infinity (the
   ultraviolet catastrophe). Wilhelm Wien proposed Wien's law, which
   correctly predicted the behaviour at high frequencies, but failed at
   low frequencies.

   By interpolating between the laws of Wien and Rayleigh-Jeans Planck
   found the famous Planck black-body radiation law which described the
   experimentally observed black-body spectrum very well; it was first
   proposed in a meeting of the DPG on October 19, 1900 and published in
   1901.

   By 14 December 1900, he was already able to present a theoretical
   derivation of the law, but this required him to use ideas from
   statistical mechanics, as introduced by Boltzmann. So far he had been
   holding a strong aversion against any statistical interpretation of the
   second law of thermodynamics which he regarded as of an axiomatic
   nature: "... an act of despair ... I was ready to sacrifice any of my
   previous convictions about physics ..."

   The central assumption behind his derivation was the supposition that
   the electromagnetic energy could be emitted only in quantized form, in
   other words, the energy could only be a multiple of an elementary unit
   E = hν, where h is Planck's constant, also known as Planck's action
   quantum (introduced already in 1899), and ν is the frequency of the
   radiation.

   At first Planck considered that the quantisation was only as "a purely
   formal assumption ... actually I did not think much about it...";
   nowadays this assumption, incompatible with classical physics, is
   regarded as the birth of quantum physics and the greatest intellectual
   accomplishment of Planck's career (however, Ludwig Boltzmann had
   already in 1877, in a theoretical paper, been discussing the
   possibility that the energy states of a physical system could be
   discrete). It was in recognition of this accomplishment that Planck was
   awarded the Nobel prize for physics in 1918.

   The discovery of Planck's constant enabled him to define a new
   universal set of physical units (such as the Planck length and the
   Planck mass), all based on fundamental physical constants.

   Subsequently, Planck tried to grasp the meaning of the 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
   like Rayleigh, Jeans, and Lorentz set Planck's 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 are wrong."

   Max Born wrote about Planck: "He was by nature and by the tradition of
   his family conservative, averse to revolutionary novelties and
   sceptical towards speculations. But his belief in the imperative power
   of logical thinking based on facts was so strong that he did not
   hesitate to express a claim contradicting to all tradition, because he
   had convinced himself that no other resort was possible."

Einstein and the Theory of Relativity

   In 1905 the three epochal papers of the hitherto completely unknown
   Albert Einstein 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.

   However, Einstein's hypothesis of light quanta ( photons), based on
   Philipp Lenard's 1902 discovery of the photoelectric effect, was
   initially rejected by Planck; he was unwilling to discard completely
   Maxwell's theory of electrodynamics. "The theory of light would be
   thrown back not by decades, but by centuries, into the age when
   Christian Huygens dared to fight against the mighty emission theory of
   Isaac Newton ..."

   In 1910 Einstein pointed out the anomalous behaviour of specific heat
   at low temperatures as another example of a phenomenon which defies
   explanation by classical physics. Planck and Nernst, in order to
   clarify the increasing number of contradictions, organised the First
   Solvay Conference (Brussels 1911); at this meeting Einstein was finally
   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 for jointly playing music.

World War and Weimar Republic

   At the onset of the First World War Planck was not immune to the
   general excitement of the public: "... besides of much horrible also
   much unexpectedly great and beautiful: the swift solution of the most
   difficult issues of domestic policy through arrangement of all
   parties... the higher esteem for all that is brave and truthful..."
   Admittedly, he refrained from the extremes of nationalism, e.g., he
   voted successfully for a scientific paper from Italy receiving a prize
   from the Prussian Academy of Sciences in 1915 (Planck was one of its
   four permanent presidents), although at that time Italy was about to
   join the Allies; nevertheless the infamous " Manifesto of the 93
   intellectuals", a polemic pamphlet of war propaganda, was also signed
   by Planck, while Einstein retained a strictly pacifistic attitude which
   almost led to his imprisonment (from which he was only saved by his
   Swiss citizenship). But already in 1915 Planck revoked (after several
   meetings with Dutch physicist Lorentz) parts of the Manifesto, and in
   1916 he signed a declaration against German annexationism.

   In the turbulent post-war years, Planck, by 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 Organisation of
   German Science), which aimed at providing support for the destitute
   scientific research; the funds they could distribute were raised to a
   considerable part abroad. In this time Planck held leading positions
   also at Berlin University, the Prussian Academy of Sciences, the German
   Physical Society and the Kaiser-Wilhelm-Gesellschaft (which in 1948
   became the Max-Planck-Gesellschaft); under such conditions he was
   hardly able to conduct any more research himself.

   He became a member of the Deutsche Volks-Partei ( German People's
   Party), the party of peace Nobel prize laureate Gustav Stresemann,
   which aspired to liberal aims for domestic policy and rather
   revisionistic aims for international politics. He disagreed with the
   introduction of universal suffrage and expressed later the view that
   the Nazi dictatorship was the result of "the ascent of the rule of the
   crowds".

Quantum mechanics

   At the end of the 1920s Bohr, Heisenberg and Pauli had worked out the
   Copenhagen interpretation of quantum mechanics, but it was rejected by
   Planck, as also by Schrödinger and Laue; even Einstein had rejected
   Bohr's interpretation. Heisenberg's matrix mechanics he called
   "disgusting", the Schrödinger equation he gave a warmer reception. He
   expected that wave mechanics would soon render quantum theory - his own
   child - unnecessary. Scientific progress ignored his concerns. He
   experienced the truth of his own earlier observation from his struggle
   with the older views in his younger years: "A new scientific truth does
   not establish itself by its enemies being convinced and expressing
   their change of opinion, but rather by its enemies gradually dying out
   and the younger generation being taught the truth from the beginning."

Nazi dictatorship and Second World War

   When the Nazis seized power in 1933, Planck was seventy-four; he
   witnessed many Jewish friends and colleagues expelled from their
   positions and humiliated, and hundreds of scientists emigrated from
   Germany. Again he tried the "persevere and continue working" slogan and
   asked scientists who were considering emigration to stay in Germany. He
   hoped the crisis would abate soon and the political situation would
   improve again. There was also a deeper argument against immigration;
   emigrating German non-Jewish scientists would need to look for academic
   positions abroad, but these positions better served Jewish scientists,
   who had no chance of continuing to work in Germany.

   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-Gesellschaft (KWG) avoided open conflict
   with the Nazi regime; except for Fritz Haber. Planck tried to discuss
   the issue with Adolf Hitler but was unsuccessful. In the following year
   of 1934, Haber died in exile.

   One year later, Planck, being the president of the KWG since 1930,
   organised 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 put pressure on him to refrain from running for another
   term.

   As the political climate in Germany gradually became more hostile,
   Johannes Stark, prominent exponent of Deutsche Physik ("German
   Physics", also called "Aryan Physics") attacked Planck, 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, but all
   they could find out was that he was "1/16 Jewish."

   In 1938, Planck celebrated his eightieth birthday; the DPG held an
   official 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 - one year before the outbreak of a new war between France
   and Germany. At the end of the same year the Prussian Academy lost its
   remaining independence and was taken over by loyal Nazis (
   Gleichschaltung); Planck protested by resigning his presidency. He
   continued to travel frequently, giving numerous public talks, such as
   his famous talk on Religion and Science, and five years later he was
   still sufficiently fit to climb 3,000-meter peaks in the Alps.

   During the Second World War, the increasing number of Allied bombing
   campaigns against Berlin forced Planck and his wife to leave the city
   temporarily 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 his entire scientific records and correspondence.
   Finally, he got into a dangerous situation in his rural retreat due to
   the rapid advance of the Allied armies from both sides. After the end
   of the war he was brought to a relative in Göttingen.

Final years

   After the war, a number of German physicists assembled in Göttingen in
   order to reestablish the Kaiser-Wilhelm-Gesellschaft. In July of 1945,
   Planck agreed to act formally as its president, again. The British
   occupation authorities insisted on changing the name, and therefore in
   February 1948 the Max-Planck-Gesellschaft was established. Despite his
   deteriorating health, Planck resumed travelling in order to give public
   talks.

   In 1946, he travelled to London on the occasion of the 300^th birthday
   of Isaac Newton. He was the only German invited. On 1 April 1946,
   Planck was succeeded as president of the KWG by Otto Hahn. On 4 October
   1947, he died, aged 89, from the consequences of a fall and several
   strokes. He is buried in Göttingen, Germany.

Honours and medals

     * "Pour le Mérite" for Science and Arts 1915 (in 1930 Planck became
       chancellor of this order)
     * Nobel Prize in Physics 1918 (awarded 1919)
     * Lorentz Medal 1927
     * Adlerschild des Deutschen Reiches (1928)
     * Max Planck medal (1928, together with Einstein)
     * Planck received honorary doctorates from the universities of
       Frankfurt, Munich ( TH), Rostock, Berlin(TH), Graz, Athens,
       Cambridge, London and Glasgow
     * The asteroid 1069 was given the name "Stella Planckia" (1938)

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