Treasures from the archive

Monthly contributions from Helen Piel, MSc PhD (Österreichische Zentralbibliothek für Physik & Fachbibliothek Chemie und Astronomie).

On 27 January 1926, the journal Annalen der Physik received Erwin Schrödinger’s manuscript for the first of his four papers on “Quantisation as an Eigenvalue problem” (Quantisierung als Eigenwertproblem). At the time, the 38-year-old Austrian physicist was chair for theoretical physics at the University of Zurich, a position previously held by Albert Einstein and Max von Laue. He had arrived in Zurich in 1921, after a year and a half of constant job and location changes: from Vienna to Jena to Stuttgart to Breslau (Wrocław) to Zurich.

Schrödinger had first come into contact with quantum theory as a student at the University of Vienna, where he read physics and mathematics between 1906 and 1910, when he handed in his dissertation. Before fully turning to theoretical physics, however, he was an assistant at Franz Serafin Exner’s institute, which focused on experimental physics. Schrödinger worked on a variety of topics, including electricity and colour theory, before his focus switched to the problems of nuclear and quantum physics. 

Taking ideas and inspiration from the work of Einstein and Louis de Broglie, among others, Schrödinger developed a complete theory of wave mechanics, set out in this 1926 papers. All four were published in quick succession until the end of the summer. With the Annalen der Physik, Schrödinger had chosen one of the most prestigious physics journals of the time – until 1920 probably the most prestigious. Many of the central papers on thermodynamics, the theory of relativity, and quantum theory were published in the Annalen: Schrödinger’s papers are in the company of those by Albert Einstein, Max Planck, Ludwig Boltzmann and others. 

Available at the University Library:

Schrödinger’s dissertation (1910): „Über die Leitung der Elektrizität auf der Oberfläche von Isolatoren an feuchter Luft“ (https://ubdata.univie.ac.at/AC13261492).

Schrödinger’s offprint collection, incl. the first editions of his four papers on „Quantisation as an Eigenvalue problem”. S33-50, S33-51, S33-54 and S33-55, Erwin Schrödinger Archive. 

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Arnold Sommerfeld once referred to Schrödinger’s theory of 1926 as “the most remarkable of all remarkable discoveries of the 20th century.” Some have emphasised how remarkable it is by saying it came out of nowhere, as it were, by coming “out of the mind of Schrödinger”. 

But Schrödinger had first encountered quantum physics in his student days – his professor in theoretical physics, Friedrich “Fritz” Hasenöhrl, was known for his excellent lectures –, even though he then focused on experimental physics first. Schrödinger turned his full attention to theory sometime in the mid- to late 1910s. While still serving in the First World War, he began studying the work of Albert Einstein. Later, having taken up the chair of theoretical physics at the University of Zürich in 1921, Schrödinger had an inspiring work environment to fully immerse himself in. There were not only his colleagues at the University, but also those at the Swiss Federal Institute of Technology, that is, the ETH Zürich: physicists Peter Debye and Paul Scherrer and mathematician Hermann Weyl among them. 

In the autumn of 1925, Debye invited Schrödinger to give a seminar on an aspect of Louis de Broglie’s work. In his dissertation, de Broglie had speculated that mass can be associated with a wave phenomenon. In a paper that Schrödinger knew, Einstein had already briefly picked up on the idea in the context of gases. Schrödinger’s theory of wave mechanics combines these inspirations with an existing, longstanding interest in extending classical mechanics. 

Schrödinger’s thought processes can be traced in the notebooks he kept. They are mostly written in Kurrent, the old German cursive, with the occasional note in Gabelsberger shorthand or headlines in Latin cursive. Some pages are neat, with underlining for emphasis, others full of crossed out sections. Read together, the notebooks show how the optical-mechanical analogy – going back to William Rowan Hamilton in the 1830s – functioned as a heuristic for Schrödinger in developing his theory.

Scientific notebooks are an invaluable source to anyone trying to understand the behind-the-scenes processes of science. Publications are often retroactively streamlined narratives. Notebooks, on the other hand, can reveal the twists and turns of the research process. They can also highlight the creativity and personality of a researcher. Schrödinger, with his classical education and earlier aspirations of becoming a writer, took notes in elegant prose that still make them very readable – so long as you know Kurrent, of course.

Available at the University Library:

Erwin Schrödinger, Notebook „Eigenwertproblem des Atoms II“. W33-725/2, Erwin Schrödinger Archive. Digitised version available at https://phaidra.univie.ac.at/detail/o:164878 

Holmes, Frederic L. (1990). Laboratory notebooks: can the daily record illuminate the broader picture? Proceedings of the American Philosophical Society 134(4), 349–366.

Joas, Christian & Christoph Lehner (2009). The classical roots of wave mechanics: Schrödinger’s transformations of the optical-mechanical analogy. Studies in History and Philosophy of Modern Physics 40, 338–351. 

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In the early spring of 1926, Schrödinger had submitted the first two of his four papers on quantisation as an Eigenvalue problem. Now he was about to send off the next manuscript to the Annalen der Physik. “Unfortunately,” he wrote to his friend, fellow physicist Hans Thirring, more would have to follow: “I say unfortunately, even though I’m having the whale of a time with this, but I’m a bit tired.” At that point in March, Schrödinger had been working on his papers for at least three months, if not longer. It hadn’t always been straightforward and at one point he complained, “If only I were better at mathematics!” Hermann Weyl, from the ETH Zürich, helped by pointing him to relevant literature. By the time he wrote to Thirring, Schrödinger was confident that his mathematical solutions were “a lot easier or at least more familiar” than Max Born’s matrices (he’d been thinking about how his theory related to Born’s and Werner Heisenberg’s work).

At the same time, Schrödinger needed to fulfil his duties as Professor for Theoretical Physics. Erwin Fues, a German theoretical physicist, was visiting and “working magnificently” on band spectra, which helped with some of the workload. (In 1943, Fues would become professor at the University of Vienna; he was a signatory of the 1933 vow of allegiance of German professors to Hitler. In August 1945 he was suspended and expelled from Austria.) But Schrödinger still hoped to find someone to support him during the upcoming winter term. A possibility he was looking at was funding from the Rockefeller Foundation. (The Rockefeller Foundation, founded in 1913, had recently begun shifting its attention to the advancement of science. Its earlier focus had been on education, social service, and public health.) That meant thinking about funding applications. 

Still, the letter to Thirring also shows Schrödinger’s optimism that “someday [this will] be worth all this effort”. He was well aware that his work could mean “the resolution of the quantum question”. 

The following autumn, Thirring visited Schrödinger and his wife Anny in Zurich. Physics was likely discussed, and perhaps even the Annalen papers, but “Above all,” Thirring wrote after his return to Vienna, “I would like to express my sincere gratitude to you and your dear wife for your gracious hospitality. The few hours I spent with you are among the most pleasant memories of my autumn trip.”

Hans Thirring died 50 years ago this month. The Physics Library is currently exhibiting a retrospective (in German) in the staircase leading to the reading rooms on the fifth floor.

Available at the University Library:

Erwin Schrödinger to Hans Thirring, 17/03/1926. B35-3855, Hans Thirring Papers. Digitised version available at https://phaidra.univie.ac.at/detail/o:143241 

Hans Thirring Papers, Special Collection, Physics Library. Partly digitised; digitisations available at https://phaidra.univie.ac.at/detail/o:128617 

Thirring, Hans (1948). Erwin Schrödinger zum 60. Geburtstag. Acta Physica Austriaca 1(2), 105–109. 

Zimmel, Brigitte & Gabriele Kerber (eds.) (1992). Hans Thirring: ein Leben für Physik und Frieden. Wien: Böhlau.

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Albert Einstein read Schrödinger’s papers soon after publication. He was then living in Berlin, where he had moved from Zurich (and the chair Schrödinger now held) in 1914. Einstein was in the unique position to be a salaried Fellow of the Prussian Academy of Sciences with no duties other than to participate in the weekly academy meetings. He had Max Planck to thank for that. Planck also pointed Einstein towards Schrödinger’s new papers: “Mr Planck showed me your theory with justified enthusiasm. I then studied it with the greatest of interests too,” Einstein wrote to Schrödinger on 16 April 1926.

After studying Schrödinger’s theory, however, Einstein had some doubts, “which you can hopefully chase away”. He asked his younger colleague how exactly his equation was meant to express the following: “If I have two systems that are not coupled to each other at all, and if E1 is an allowed energy value of the first system quantum-wise and E2 an allowed energy value of the second, then E1 + E2 = E must be an allowed energy value of the total system consisting of both of them.” About a week later, on 22 April, Einstein wrote again. He had gone back to Schrödinger’s first paper, from which he could work out Schrödinger’s train of thought and which equations he had used. “So my letter was superfluous,” he admitted. 

Einstein’s letter most likely crossed ways with Schrödinger’s reply to his earlier one from 16 April; Schrödinger’s reply is dated 23 April. In it, Schrödinger explained that and why Einstein’s doubts were unfounded, the conclusion to which his senior colleague had come to already. Schrödinger also expressed his gratitude for both Planck’s and Einstein’s approval of his ideas, which were “more valuable to me than that of half the world.” Aware of his influences, Schrödinger then thanked Einstein for his paper on gas theory, which had highlighted the importance of de Broglie’s ideas for him. Without this inspiration, he wrote, “this work would definitely not have been developed now and probably not ever (I mean, not by me)”. 

Einstein’s reply from 26 April will have gratified Schrödinger. “I am convinced,” the Nobel Prize laureate wrote, “that you have made a decisive breakthrough with your formulation of the quantum condition”.

Available at the University Library:

Einstein – Schrödinger correspondence, April 1926. B33-(56)-8 to B33-(56)-11, Erwin Schrödinger Archive. Digitised versions available at

 https://phaidra.univie.ac.at/detail/o:1542243,

 https://phaidra.univie.ac.at/detail/o:1542421,

  https://phaidra.univie.ac.at/detail/o:1542189,

 https://phaidra.univie.ac.at/detail/o:1542331.

Halpern, Paul (2015). Einstein's Dice and Schrödinger's Cat: How Two Great Minds Battled Quantum Randomness to Create a Unified Theory of Physics. New York: Basic Books.

Hanle, Paul A. (1977). The coming of age of Erwin Schrödinger: his quantum statistics of ideal gases. Archive for History of Exact Sciences 17(2), pp. 165-192.

Paty, Michel (2022). Einstein’s criticism of quantum mechanics. In Olival Freire (ed.), The Oxford Handbook of the History of Quantum Interpretations (pp. 303-338). Oxford: Oxford University Press. 

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In 1926, Max Planck was in his late 60s and still actively involved in the world of science. He was a leading figure in the German Physical Society and in the Prussian Academy of Sciences as well as editor of the Annalen der Physik. For many, he was the authority figure in physics and a spokesperson for science as a whole. 

At the time, Schrödinger and Planck were corresponding quite frequently about the statistics of ideal gases, since Schrödinger had sent a manuscript on the topic for inclusion in the Academy’s proceedings. Planck decided to publish it, adding – as agreed between the two of them – a commentary of his own. 

When it came to Schrödinger’s new work, Planck’s reaction was very encouraging – and very lyrical: “I read your paper like a curious child listens, full of excitement, to the solution of a riddle which has plagued them for a long time. And I delight in all the beauties that reveal themselves to the eye, but which I will have to study in greater detail in order to fully grasp them.” 

A few weeks later, towards the end of May, Planck had to admit that these “epoch-making papers” gave him trouble: “I am currently making very slow progress in penetrating these peculiar trains of thought.” Thus he and, as he emphasised, all of his physicist colleagues in Berlin, were delighted that Schrödinger considered presenting his theory at a meeting of the German Physical Society that summer. They were all hoping to be inspired and promised not to tire him out too much in the discussion. 

Schrödinger replied that under these conditions he would gladly come and asked for advice on his presentation: “I mean, should I think more about the fact that you and Einstein and von Laue will be in the auditorium – a thought that leaves me faint anyhow – or should I think more about the gentlemen who are less familiar with theoretical physics”? Planck suggested a general introduction to the theory as well as giving a second, more detailed presentation on another day. Schrödinger agreed.

Planck and Schrödinger continued discussing physics throughout the year. At the same time, Planck was about to retire. The Königliche Friedrich-Wilhelms-Universität zu Berlin – today’s Humboldt University – quickly added Schrödinger to the list of possible successors. Other names mentioned were Arnold Sommerfeld, Max Born, and Werner Heisenberg (the latter then deemed “too young”). Schrödinger had another offer from Johns Hopkins University in Baltimore and in general a hard time deciding; he was happy in Zurich. But, as a poem Schrödinger wrote in Planck’s guest book indicates, when Planck said: “I would like it,” Schrödinger finally accepted the offer from Berlin. In the summer of 1927, he and his wife Anny would move to the German capital.

Available at the University Library:

Planck – Schrödinger correspondence, 1926. B33-(61)-19 to B33-(61)-25, Erwin Schrödinger Archive. Digitised versions available at  https://phaidra.univie.ac.at/search?q=b33-(61)%2C%201926&page=1&pagesize=10 

Schrödinger, Erwin (1925). Bemerkungen über die statistische Entropiedefinition beim idealen Gas. Sitzungsberichte der Preußischen Akademie der Wissenschaften. Physikalisch-mathematische Klasse, 434-441.

Eckert, Michael (1997). Die „Autorität“ der theoretischen Physik in Deutschland. Zum 50. Todestag von Max Planck. Physik in unserer Zeit 28(6), 246-250.

Heilbron, Jon L. (2000). The Dilemmas of an Upright Man: Max Planck and the Fortunes of German Science (with a new afterword). Cambridge, MA: Harvard University Press.

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The spring semester was drawing to a close in Zurich when Schrödinger informed his dean that he would have to cancel two of his upcoming lectures as well as one tutorial. For, he explained, “there will be lectures by excellent scientists from my field during the so called ‘Magnetic Week’”. These scientists had been invited by the physicists at the ETH Zürich, where Peter Debye had begun to organise an annual international lecture series. For the days between 22 and 26 June 1926, the chosen topic to discuss was magnetism.

Debye, who won the Nobel Prize in Chemistry in 1936, was working towards the (re-)internationalisation of science in the interwar years. Born in Maastricht, close to the Dutch-German border, he had held positions in the Netherlands, Germany, and Switzerland and was fluent in several languages. In 1940, he emigrated to the US. His contact with Schrödinger during their time in Zurich wasn’t close but possibly influential. As Debye remembered it, he received Louis de Broglie’s dissertation and “then I said to Schrödinger, ‘Schrödinger, you know, I have not much time. […] and I don’t understand this De Broglie business. You read it. You see if you could get a nice talk about it.’”

However, Debye never claimed having had any influence on the development of Schrödinger’s wave mechanics. They were at different institutions and though friendly towards each other, not engaged in any significant scientific exchanges. In fact, according to Debye, Schrödinger hardly talked to anyone about what he was working on; “Except he went to the mathematician, [Hermann] Weyl, in order to help him out with some of the equations.” The first Debye heard about Schrödinger’s theory was from Edgar Meyer, professor of experimental physics at the University of Zurich. 

Meyer was one of Schrödinger’s closest colleagues in Zurich. He had, in fact, been the one to convince the faculty to offer the chair for theoretical physics to the Austrian physicist. Schrödinger described Meyer as a “perfectly charming, dear, and pleasant person, a jolly guy without any falsehood”. Although they fell out with each other at some point, they were eventually back on good terms.

The dean granted Schrödinger’s attendance at the Magnetic Week. Schrödinger used the opportunity to discuss his equation with international colleagues like Wolfgang Pauli, then professor in Hamburg. Pauli once joked that Schrödinger’s wave mechanics was a “local superstition”, though he assured him in a letter that this was not meant personally; nor was it meant to detract from Schrödinger’s work.

In the mid-2000s, Debye’s relationship to the Nazi regime was at the centre of the so-called the “Debye affair”. Prompted by this, chemist Jurrie Reiding has been working on a comprehensive biography of Debye which is set to be published later this year: Being His Own Man. Work and Life of Nobel Laureate Peter J. W. Debye (1884–1966).

Available at the University Library:

Wolfgang Pauli to Erwin Schrödinger, 22/11/1926. B33-978/2, Erwin Schrödinger Archive. Digitised version available at https://phaidra.univie.ac.at/detail/o:1542361. 

Altschuler, Glenn C. (2006). The convictions of Peter Debye. Daedalus 135(4), 96–103.

Reiding, Jurrie (2010). Peter Debye: Nazi collaborator or secret opponent? Ambix 57(3), 275–300. 

Schirrmacher, Arne (2019). Establishing Quantum Physics in Göttingen. David Hilbert, Max Born, and Peter Debye in Context, 1900–1926. Cham: Springer.

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In 1927, Schrödinger moved from Zurich to Berlin as successor to Max Planck. He could look forward to an active scientific environment that included the Kaiser Wilhelm Institute for Physics and the German Physical Society on an institutional level. On 30 November 1927 he wrote to his friend Stefan Meyer:

“So far, I’m quite enjoying Berlin. At the faculty there is a whole Austrian colony […]. The overall atmosphere is very nice. The closest colleagues in my field, Laue, Planck, Einstein are all three very lovely people – and Nernst one can get along with, once one gets over his pathological vanity and cantankerousness.”

Not long after taking up his post, Schrödinger was elected to the Prussian Academy of Sciences. The vote was unanimous, which was unusual. At the time, the Academy was based in the Baroque Revival building of the national library. It had been founded in 1700 with Gottfried Wilhelm Leibniz as its first president. Like other academies, it was a network that offered communication channels through its meetings and proceedings and conferred prestige and peer recognition on its members. Unlike others, however, it included both the natural sciences and the humanities. Women weren’t forbidden membership in theory, but in practice none were elected, notwithstanding a few honorary members. It was in fact Lise Meitner who, in 1949, would become the first woman to be elected on scientific merit, and then only as a corresponding member. (The first woman to become a full member was historian Liselotte Welskopf in 1964.)

As a new member, Schrödinger had to introduce himself to the Academy in a meeting open to the public, which he did on 4 July 1929. His speech included biographical notes as well as some thoughts on his field. (Here, his main point was that, perhaps, theoretical physics needed to say goodbye to causality.) 

“I came to terms with modern atomic theory only slowly. Its internal contradictions sounded like screaming dissonances measured against Boltzmann’s pure, mercilessly clear trains of thoughts. For a while, I practically took flight and sought refuge in the field of colour theory, inspired by Franz Exner and K.W.F. Kohlrausch.”

He also honoured Fritz Hasenöhrl, whose lectures had impressed the student Schrödinger. Hasenöhrl, he said, laid the “foundation for my scientific personality”, while Boltzmann had been his “scientific first love”. Schrödinger thus gave his Viennese roots a prominent place in this brief autobiography. 

His time in Berlin would become one he remembered fondly for both his scientific and social contacts and activities. The latter ranged from musical evenings at Planck’s house and sailing with Einstein to “Viennese sausage evenings” at the Schrödingers’. He moved to Oxford in 1933, having made the decision to emigrate not long after the Nazi rise to power.

In 1946, the Prussian Academy of Sciences was reopened as the German Academy of Sciences at Berlin. After Reunification, it was reconstituted as the Berlin-Brandenburg Academy of Sciences and Humanities.

Available at the University Library:

Erwin Schrödinger to Stefan Meyer, 30/11/1927. B16-49, Stefan Meyer Papers.

Schrödinger, Erwin (1929). Antrittsrede des Hrn. Schrödinger. Sitzungsberichte der Preußischen Akademie der Wissenschaften, Physikalisch-mathematische Klasse. S33-69, Erwin Schrödinger Archive.

Fischer, Wolfram & Interdisziplinäre Arbeitsgruppe Berliner Akademiegeschichte (eds.) (2000). Die Preußische Akademie der Wissenschaften zu Berlin 1914–1945. Berlin: Akademie-Verlag.

Phillips, Denise (2016). Academies and Societies. In Bernard Lightman (ed.), A Companion to the History of Science (pp. 224-237). Oxford [etc.]: Wiley Blackwell.

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