How Max Planck Orchestrated the Quantum Revolution of the 1920s

In the 1920s, Max Planck was at the center of the wild revolution in Physics, often supporting and financing the theories but sometimes restraining the work of Albert Einstein, Werner Heisenberg, Max Born, Otto Hahn, Lise Meitner, Max von Laue, Erwin Schrödinger and more (way more).  I contend that this happened because of his political actions and a series of personal tragedies around WW1 which damaged his international reputation and enhanced his German reputation which left Planck with the power and the will to build German science into a powerhouse.  Ready? Let’s go… 

When World War 1 began in 1914, Max Planck was 56 years old and was the father of four children from his first wife, Marie, who had died of tuberculosis 5 years previously, 26-year-old Karl, 25-year-old twins Emma and Grete, and 21-year-old Erwin, and his second wife Marga was pregnant with his fifth child.  Max Planck was respected and admired by almost everyone who knew him.  For example, the physicist Lise Mietner, who had traveled to Berlin in 1907 specifically to study under Planck and became his assistant in 1913 said that Planck, “was such a wonderful person, that when he entered a room, the air of the room got better.[1]”  Also, just before the start of the war, in 1913, Planck was instrumental in getting 35-year-old Albert Einstein a position in Berlin, working to create a new section of the Kaiser Wilhelm Institute for theoretical Physics just for Einstein.  Einstein was happy about the move as it meant working near Planck, being near his girlfriend/cousin Elsa, and living near his good friend the Chemist Fritz Haber.  Once in Berlin, Einstein, Planck, and Haber all became very close, and Einstein was particularly devoted to Planck.  Five years later Einstein wrote to Max Born’s wife Hedwig and told her that the best thing about Berlin was “chiefly” working with Planck, reminding her that, “to be near Planck is a joy.[2]

Max Planck
Max Planck

Surprisingly, this closeness between Einstein, Haber, and Planck did not diminish with the outbreak of World War 1.  I say it was surprising because, Planck, like almost all of his German compatriots, welcomed the outbreak of World War 1 and was pleased that his two sons volunteered for the military and his daughters joined the Red cross. Planck wrote his sister, “what a glorious time we are living in.  It is a great feeling to be able to call oneself a German[3]”.  Fritz Haber was even more invested in patriotic fever and immediately turned to use his chemical expertise from the development of nitrogen fertilizer which saved millions of lives to the production of munitions and then became the father of chemical weapons!  Einstein, on the other hand, was actively against the war and was distressed by the madness taking over his new workplace and his friends.

For example, it wasn’t long into the war when reports that Germans had violated a treaty by attacking Belgium, killing, raping, and enslaving thousands, reached Germany.  However, Planck and other German intellectuals thought it was propaganda and in September of 1914, Planck and Haber added their names to a long list of prominent scientists that denied that Germany started the war or even, caused the harm to “life and property of a single Belgian citizen” except out of self-defense.  Einstein was disgusted, and not only was they one of the few prominent scientists to not sign the manifesto but also co-wrote a rebuttal! 

The pro-war letter that Planck signed was published to great patriotic acclaim in Germany and a feeling of betrayal and revulsion among the Allies.  Soon Planck’s Dutch friend Hendrik Lorentz who he met at the first Solvay conference started sending him accounts of the terrors of the German occupation.  Planck started to see that things occurred that “do not conduce to the honor of Germans[4].”  By 1916, Planck wrote an open letter to Lorentz slightly denouncing the earlier signing of his proclamation as he “noticed with distress [that it gave] rise to incorrect ideas about the feelings of its signers[5].” Then, that same year, Planck’s views on the war became more personal: his younger adult son Erwin was captured by the French and his older son Karl was killed in action and Planck focused on his teaching which wasn’t easy.  For example, the winter of 1916/1917 was particularly cold and a student named Gabriele Rabel recalled, “We were without coal. Indeed, some universities had completely closed their doors. But in Berlin, teachers, and students kept on their overcoats and plodded ahead.  Each day Planck made a little speech, encouraging us to endure[6].”  When he once asked if he should cancel a class for the weather, he was overjoyed to learn that his students were devoted to learning, “[Planck’s] happiness and pride at our devotion, and the childlike candor with which he expressed his joy was overwhelming, and whatever hearts had not yet flown to him before were conquered now[7].”  Then tragedy struck again, in May of 1917, Planck’s daughter Grete died in childbirth to a daughter they called Grete in her honor.  Planck was devastated, writing Einstein, “I must tell you that I still feel physically incapable of work these days… My grief over my …daughter, who passed away in my arms last week… still gnaws too persistently at my thoughts for them to be able to exert their normal freedom of action.[8]” In February of 1918, to improve Planck’s mood, Einstein arranged a celebratory meeting for Planck’s 60th birthday in April, “because I am very fond of Planck and he will certainly be pleased when he sees how much we all like him and how highly everyone regards his lifework.[9]” 

solvay conference 1911
Solvay conference 1911

Planck enjoyed his celebration but his good mood didn’t last long because, on November 11 of that same year, Germany lost the war, and Germany was thrust into chaos and economic freefall, although Planck’s younger son Erwin was released from captivity.  The next year, 1919, Planck’s other daughter, Emma, who had married her former brother-in-law after she moved in to take care of her orphaned niece, also died in childbirth to a daughter they named after her mother.  Einstein said that “I could not hold back my tears when I visited him… his aching pain shows through.[10]”  Planck wrote Lorentz, “Now I mourn both my dearly beloved children in bitter sorry and feel robbed and impoverished.  There have been times when I doubted the value of life itself.[11]”  Despite the personal and national disasters around him, Planck’s professional life was at its pinnacle, as the same time as he heard of his second daughter’s death, Planck received notice that he was awarded the 1918 Nobel Prize (they gave the award a year late) for his “discovery of energy quanta.”  Planck’s birthday celebration is considered a big reason he finally got the recognition he deserved, and some, like the Physicist Arnold Sommerfeld, re-used their words at his celebration for the Nobel committee.  Fritz Haber went with Planck to Sweden that same year as he won the Nobel Prize for Chemistry for his production of nitrogen fertilizer, causing mass protests and melding Planck’s accomplishments with Haber’s chemical weapons in many people’s minds.

The immediate post-war years were hard.  There were terrible food shortages, riots, and transit strikes, which made just surviving difficult let alone doing research.  In addition, all German scientists (aside from Einstein) were hated by the majority of the international scientific community for signing the manifesto and for facilitating chemical warfare.  For example, Einstein was the only German scientist invited to the Solvay Conferences of 1921 and 1924 specifically because of the manifesto (Einstein didn’t go in solidarity).  Planck knew that their science departments were struggling and they had very little opportunity for foreign investments so, in 1920, Max Planck got together with Fritz Haber and created an Emergency Association of German Science to collect money from industry and government to keep German science afloat.  Planck made sure that a significant portion of the cash went to theoretical research, despite the fact that industry and the government did not see any purpose to it at the time.  Because two well-known Nobel prize winners were collecting money, and one arguably of history’s most influential Chemists, they were pretty successful.  One of their early acts was inviting the Dane Niels Bohr to a talk in Berlin in April of 1920.  Bohr was too excited by the opportunity to meet Einstein and Planck to refuse and he ended up forming many close friendships, calling his conversations with Einstein the “greatest experience” he ever had!  The Germans were overjoyed by his visit, a scientist named George de Hevesy said that he had “never experienced an ovation similar to that given to Bohr in Berlin.  Young and old celebrated him with complete conviction and enthusiasm.”  Lise Mietner felt a little jealous of the professors dominating Bohr’s time and told Planck she wanted an afternoon “without bigwigs” and he agreed.  It was at this luncheon that Bohr became very close to many up-and-coming scientists including James Franck.  I mention Frank in particular because in November of 1920 Franck became a professor at the University of Gottingen (at the request of his friend Max Born was just made the chair) and soon there was a revolving door of students, visitors, and ideas between the scientists at Gottingen and Bohr’s newly formed Institute of Theoretic Physics in Copenhagen (now called the Niels Bohr Institute).    

Planck's Quantum Theory
Planck’s Quantum Theory

Simultaneously, Einstein’s life was changing drastically, with long-term implications for the world.  A few months before Planck’s second daughter’s death, in May of 1919, an English scientist named Arthur Eddington photographed an eclipse and proved that the stars near the sun were deviated from their path by the mass of the sun just as Einstein predicted by general relativity.  The papers went crazy and soon Einstein was the most famous scientist in the world!  The burgeoning Nazi party decided that Einstein who was both Jewish and a pacifist was the origin of Germany’s misfortunes, and Relativity was “Jewish” science that was denigrating pure German science.  In August of 1920, a Nazi named Paul Weyland announced a series of 20 lectures against relativity “for the Preservation of Pure Science.”  Einstein went for entertainment but he was not amused and when Planck heard about it, he called it, “scarcely believable filth”.  Planck realized, however, that there was a rising opposition to relativity from real scientists including the Nobel prize winners Philipp Lenard and Johannes Stark.  Planck decided to host a debate about the validity of relativity in September between Einstein and Philip Lenard which Planck ensured happened without drama but also did not seem to change anyone’s minds.  Einstein flirted heavily with leaving Germany but only stayed on in order “not to disappoint Planck[12].”  In 1922, Einstein was awarded the Nobel prize (for the previous year) and Planck limited Einstein’s duties to the bare minimum (1 lecture a year) to keep him in Berlin which did nothing to quash the anti-Einstein anti-Semitic faction.  By 1924, Lenard and Stark were publishing a public manifesto proclaiming their devotion to Hitler, as a “gift of God from a long darkened earlier time when races were still purer[13]”!  

Meanwhile, Planck was still supporting theoretical physics throughout Germany irrespective of whether the recipients were Jewish or not, including Max Born and James Frank at the University of Göttingen (Fun fact: Max Born coined the term “Quantum Mechanics” in 1924).  Anyway, in 1922, Born and Frank invited Niels Bohr to give a series of lectures in Gottingen and a 21-year-old wonderkid named Werner Heisenberg went and was inspired.  Three years later, in 1925, Heisenberg was Max Born’s student and thought of using matrix mathematics to create equations for describing how electrons behave.  Heisenberg went to Born and told him that he had written “a crazy paper[14]” and he didn’t dare send it in for publication on his own.  Luckily, Born was bowled over, and Max Born, Werner Heisenberg, and a fellow scientist named Pascual Jordan published a series of papers that arguably marked the beginning of the “modern” equations and theories of Quantum Mechanics.  Planck gloated, “Quantum mechanics is at the center of interest of the physicists of all countries. And just there, in the work of Heisenberg and Born, which the Committee has supported … it is clear how useful the Committee has already been for the development of physics in Germany.[15]” 

At almost the same time, an Australian scientist named Erwin Schrödinger created a wave equation for quantum mechanics.  Planck wrote Schrödinger, “I am reading your paper as an excited child listens to the answer to a riddle that has long perplexed it.[16]”  Heisenberg, however, thought that Schrodinger’s paper was “disgusting[17]” and worried that his matrix theory would be discarded for Schrodinger’s far easier wave theory.  In 1926, Heisenberg went to Copenhagen to study with Niels Bohr. There, while trying to create a quantum theory without waves or particles, Heisenberg ended up realizing that position and momentum are linked in that the more precisely you measure one property, the less accurately you can measure the other property: this is called the uncertainty principle.  Planck (Schrödinger, and Einstein) hated the uncertainty principle, which Planck called the “ominous relation,” of Heisenberg’s.  Planck worried that if you cannot have exact values for momentum and position then that creates, “an unacceptable limitation of the freedom of thought, and… mutilation of the main instrument with which the theorist must work.[18]” 

Around this time the Solvay committee decided that there were too many exciting ideas out of Germany and removed their anti-German embargo, and most other conferences followed suit.  Also, in 1927, Planck invited Schrodinger to Berlin, and for a short while the Berlin view of quantum mechanics (led by Schrodinger and supported by Einstein and Planck and more) was in direct debate with the Copenhagen-Gottingen view (led by Heisenberg and supported by Bohr and Born and more).  Despite his dislike of the uncertainty principle, Planck continued to support and mentor Heisenberg and Born, and other supporters of the Copenhagen view.  However, soon outside politics would take over, and destroy everything that Planck held dear including his relationship with Einstein and Haber, and that story is next time on the Lightning Tamers.

Whew!  So, that is the second half of my biography of Planck.  If you haven’t watched part 1, please check it out, Planck had a more direct influence on science.  I also have videos with more details on how Planck wrote his 1900 paper and why Planck wrote Boltzmann’s equation and how it ended up on Boltzmann’s grave. 


[1] Lise Mietner found in Sime, R Lise Meitner: A Life in Physics (1996) p. 37

[2] Einstein to Hedwig Born (Feb 8, 1918) The Correspondence of Albert Einstein: Volume 8 p.467

[3] Planck to Emma Lenz (Sept 17, 1914) found in Heibron, J The Dilemmas of an Upright Man (2000) p. 87

[4] Max Planck to Lorentz (Nov. 15, 1914) found in Heibron, J The Dilemmas of an Upright Man (2000) p. 88

[5] Open letter from Max Planck to Lorentz (February 27, 1915) found in Heibron, J The Dilemmas of an Upright Man (2000) p. 88

[6] Found in Brown, B Planck: Driven by Vision, Broken by War (2015)

[7] Found in Brown, B Planck: Driven by Vision, Broken by War (2015)

[8] Max Planck to Albert Einstein (May 26, 1917) Einstein, A The Correspondence of Albert Einstein: Vol 8 p. 334

[9] Einstein to Arnold Sommerfeld (Feb 1, 1918) The Correspondence of Albert Einstein: Volume 8 p. 460

[10] Albert Einstein to Max Born (December 8, 1919) A The Correspondence of Albert Einstein: Volume 9 p. 169

[11] Max Planck to Lorentz (Dec 21, 1919) found in Heibron, J The Dilemmas of an Upright Man (2000) p. 114

[12] Paul Ehrenfest to Albert Einstein (August 28, 1920) The Papers of Albert Einstein: Vol 10 p. 244

[13] Lenard, P Stark, J “The Hitler Spirit and Science”, (May 8, 1924) Translation from Hentscheel, K Physics, and National Socialism: An Anthology of Primary Sources (2011) p. 9

[14] Found in Pais, A Niels Bohr’s Times (1991) p. 278

[15] Found in Heibron, J The Dilemmas of an Upright Man (2000) p. 123

[16] Max Planck to Schrödinger (May 27 1926) Found in Heibron, J The Dilemmas of an Upright Man (2000) p. 162

[17] Heisenberg to Pauli found in Cropper, W The Quantum Physicists and an Introduction to Their Physics (1970) p. 90

[18] Max Planck to Lorentz (June 6, 1927) Found in Heibron, J The Dilemmas of an Upright Man (2000) p. 165

Leave a Reply

This site uses Akismet to reduce spam. Learn how your comment data is processed.