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ERWIN SCHRÖDINGER—SCIENTIST, DUBLINER … AND MORE

By Brian Hopkins and Peter McClintock

Above: Erwin Schrödinger (1887– 1961) in 1933, the year in which he received the Nobel Physics Prize and fled Nazi Germany. His theory of quantum mechanics, devised in 1926, is exploited by the semiconductor ‘chips’ on which modern electronics universally relies and has particular contemporary relevance for the development of quantum computers. (Alamy)

On the cusp of 1940, Ireland was suffering from economic hardship, especially evident in the tenements of the urban poor in Dublin and Cork. Moreover, living in overcrowded conditions, the poor were confronted by a return of such spectres of the 1840s as typhus and malnutrition. Having engaged in an economic war with Britain since 1932, de Valera’s government aggravated the malaise still further by adopting a policy of protectionism and self-sufficiency. Apart from an enervated economy, the Free State government had also to respond to a surge in IRA activity and did so through the draconian Emergency Powers Act (1939), which culminated in internment, hunger strikes and executions.

There was, however, another side to ‘Dear Dirty Dublin’, eloquently captured by Clair Wills in That neutral island (2007). As a consequence of wartime neutrality, Dublin, away from the tenements, witnessed a literary and cultural revival, as well as amply stocked shops and restaurants. For the English moneyed class, the city beckoned as an escape from a country engulfed by the bleakness of war. It was this incongruous scenario that welcomed a paradigm-shifting scientist into its midst: Erwin Rudolf Josef Alexander Schrödinger.

SCHRÖDINGER THE SCIENTIST

Above: Schrödinger and Monsignor Pádraig de Brún outside the School of Theoretical Physics, 65 Merrion Square, in 1952. Reputedly almost 7ft tall, de Brún makes Schrödinger appear misleadingly diminutive. The priest was an accomplished mathematician, with a DSc. from the Sorbonne and a chair in Mathematics at St Patrick’s College, Maynooth. (DIAS)

Schrödinger had been playing a central role in the revolutions in physics that occurred in the early decades of the twentieth century. There was a ferment of new ideas and discoveries, resulting in a transformation in how we perceive the physical world. Gone was the comfortable expectation that matter on very small scales behaves as normally as in everyday life except for everything being smaller. It came to be appreciated that its behaviour was dramatically different, and in many respects counter-intuitive. The existence of atoms had been confirmed beyond doubt, but Rutherford and collaborators had shown that atoms were mostly empty space, with a tiny positive nucleus, consisting of protons and neutrons, that was very much smaller than the atom as a whole. Bohr and others showed that the outer part of the atom could be perceived as negative electrons orbiting the nucleus, rather like the planets of the solar system orbiting the sun, but with the important differences that only certain quantised orbits were allowed and that the electrons were just points, seemingly with no size at all. Equally counter-intuitive, there was Einstein’s theory of relativity, in which the mass of a moving object depends on how fast it is going, space contracts along the direction of motion, time is a fourth dimension, and gravitational forces are derived from a distortion of the space–time continuum caused by the presence of massive objects.

One result of particular importance for Schrödinger was Louis de Broglie’s inference that every moving object has an associated wave whose wavelength is inversely proportional to its momentum (i.e. to the product of its mass and its velocity). Thus, as we walk around, we are all characterised by our own de Broglie waves, but because we are so massive compared to an atom our wavelengths are incredibly small, so that we do not have much ‘fuzz’ at our edges, which remain crisply defined. For much lighter objects around atomic scale or less, however, the wavelengths are far larger and may substantially exceed the classical size of the object. It was obvious that, if small entities like this were as wave-like as they were particle-like, traditional Newtonian mechanics could not possibly describe their properties. Some completely new, revolutionary, approach was needed. Schrödinger’s most brilliant achievement was to provide precisely that, in the form of the wave equation that bears his name.

The Schrödinger wave equation is applicable quite generally. It enables, for example, calculation of the quantum energy levels of electrons in atoms that are heavier and more complex than the hydrogen atom, for which Bohr’s model had been sufficient to reveal the main properties. By solving the Schrödinger wave equation, one finds the value of the so-called wave-function at any chosen position, which can be interpreted as giving the statistical probability of the electron being there, although its presence has no objective reality until a measurement is made to determine where it actually is. Until that happens, it remains in a ‘superposition of possible states’. Thus traditional mechanics, with hard-edged objects existing at well-defined positions in space, was replaced by Schrödinger’s new theory, wave mechanics, which tells us the probability that they might be there. The sharply defined, planet-like orbits of Bohr’s model had to be replaced by fuzzy, often doughnut-shaped regions of high probability.

Schrödinger instinctively disliked this statistical interpretation, to such an extent that he went to the trouble of proposing a paradox, now known as ‘Schrödinger’s cat’, to demonstrate that the so-called Copenhagen interpretation of the wave-function was absurd. He envisaged a cat inside a closed box which might (or might not) be killed by a random quantum event triggering the release of poison. The quantum event was a radioactive decay that would take place eventually, but at a completely indeterminate time. The thought experiment consisted of opening the box, until which time the cat had to be envisaged as being in a superposition of alive/dead states, which indeed seemed a ridiculous idea.

Nonetheless, despite Schrödinger’s dislike of the Copenhagen interpretation of the wave-function and the obvious absurdity of a cat that is neither alive nor dead, every experimental test—over almost a century now—has provided a triumphant validation of the theory of quantum mechanics.

DUBLIN BOULEVARDIER IN THE LAND OF SAINTS AND SINNERS

In December 1939 the academic vagrant Schrödinger arrived in Dublin to be greeted by his host, de Valera, mathematician and Gaeilgeoir enthusiast. Within a year or so he became director of the School of Theoretical Physics housed in the Dublin Institute for Advanced Studies (DIAS), cheek by jowl with an inevitable School of Celtic Studies. Dev was delighted to have enticed a Nobel Physics Prize-winner to head a project that he had drafted to promote Ireland’s scientific standing. Schrödinger had shared the award with Paul Dirac six years earlier ‘for the discovery of new productive forms of atomic theory’, thus recognising him as one of the fathers of quantum mechanics.

Schrödinger took up residence in Clontarf, together with his wife Anny, his mistress Hilde and the young daughter Ruth whom he had fathered with the latter. Despite Ireland’s Catholic conservatism, this ménage à trois seemingly met with little public disapprobation—in contrast to when he was a fellow of Magdalen College, Oxford. Nor did the fact that he had two more daughters by two different Irish women in 1944 and 1946. Schrödinger had an entangled open marriage in that he pursued many other women that Anny knew about while she had sustained love affairs with two of Schrödinger’s best friends, the physicists Hermann Weyl and Arthur March (Hilde’s husband).

Schrödinger reportedly had an engaging personality that exuded charisma, charm and kindness. These traits not only made him attractive to women but also enabled him to forge scientific collaborations. He mixed freely with the Dublin literati (e.g. Brian O’Nolan/Flann O’Brien/Myles na gCopaleen) and artists (e.g. Patrick O’Connor) and regularly attended the theatre. In particular, he formed an easy, enduring and advantageous friendship with the polymath Monsignor Pádraig de Brún, who just happened to be the first chairman of the DIAS. Schrödinger began to feel so at home in Dublin that he claimed that Austria and Ireland shared Celtic roots. By 1948 he and his wife had been granted Irish citizenship while retaining Austrian nationality, Schrödinger having been elected as a member of the Royal Irish Academy in 1931. As shown by his rampant philandering, however, Schrödinger displayed a reckless disregard for social mores and traditions. Such an indifference would eventually lead to his name being disgraced.

Schrödinger’s unconventional polyamorous conduct was an open secret, at least in Dublin’s freethinking circles, but there was a darker side, as exposed by Irish Times journalist Joe Humphreys in 2021. Schrödinger had a history of grooming and sexually abusing girls as young as twelve, even recording his conquests in a diary entitled Ephemeridae (mayflies). In short, his reputation changed from being that of a Lothario to that of a paedophile, the consequences of which were dramatically propelled by a student protest at Trinity College, Dublin: his statue was removed, as was his name from both the physics lecture theatre and a cycle map.

SCHRÖDINGER’S ENDEAVOUR TO EXPLAIN BIOLOGY AT AN ATOMIC LEVEL

Above: Schrödinger was a keen cyclist and, in honour of his contribution to science, a bicycle path was opened in September 2021 tracing a route from Clontarf to the DIAS in Merrion Square. Two months later, he was revealed to have been a paedophile. The map was quickly rededicated to significant Irish scientists other than Schrödinger.

Following his work on quantum mechanics, Schrödinger spent several years in Dublin trying to develop a unified field theory (a ‘theory of everything’) that would bring together in a consistent way the forces due to gravity, electricity and magnetism and nuclear forces, working partly in collaboration with Einstein. Unfortunately for them both, the enterprise ultimately failed.

After that, Schrödinger turned his attention to very different kinds of problems in philosophy, eastern religion and the physics of life. In relation to the latter, he asked himself what it was about a particular arrangement of atoms in a piece of living matter that made it alive, whereas a different arrangement of exactly the same atoms would not be alive.

He addressed this question in a celebrated set of public lectures at the DIAS in 1943. These were published the following year as what became a classic text, What is life?, and this little book seems to have been in print in one form or another ever since. The 1992 edition, which also included his 1956 Terner Lectures Mind and matter and his essay Autobiographical sketches, as well as a foreword by Roger Penrose, has since been reprinted at least a dozen times. Penrose remarks that What is life? must rank among the most influential of scientific writings of the last century.

Schrödinger had been bold enough to tackle this fundamental question—central to humanity’s understanding both of itself and of its place within the universe—more than a decade before the discovery of the structure of DNA, and both Francis Crick and James Watson, who received the Nobel Prize for the discovery, acknowledged the book as an early source of inspiration.

Schrödinger pondered the question of why atoms are so small. This is, of course, equivalent to asking why we, as examples of life, are so big. His conclusion was that, given the constant thermal jiggling of our constituent atoms and molecules and the quantum indeterminacy mentioned above, life can only be stable, and governed by reliable physical laws, if the statistical averages are reliable, which in turn requires that the number of atoms be very large. It is a penetrating insight, albeit absolutely obvious in retrospect.

A lot was already known about heredity, especially from the nineteenth-century work of Gregor Mendel, and it was evident that the information to be inherited must be encoded in some way in the genes, but it was quite unclear how that happened. Schrödinger argued that the hereditary information must be carried by a molecule, whose required stability would derive from quantum mechanics. Mutations could be attributed to rare quantum transitions in its structure. He thus showed that the existence of such a molecule could account for the observations. Of course, it is now well known that his arguments were characteristically well aimed, and that the molecule in question is DNA. What is life? is arguably the most enduring outcome of Schrödinger’s time in Dublin, even though it is probably very different from what Dev had in mind when he originally invited him.

In conclusion, two comments. First, an unresolved question is how Schrödinger managed to circumvent censure by the gatekeepers of Holy Ireland: Eamon de Valera and Archbishop John Charles McQuaid. It is hard to imagine that Dev was unaware of Schrodinger’s iconoclastic modus vivendi given his, and particularly McQuaid’s, widespread network of informants. Perhaps in his eagerness to secure DIAS tenure for the heavyweight physicist he had embraced a state of cognitive dissonance, which is sometimes associated with obfuscation (not infrequent among politicians). Dev, the master sophist, had undoubted powers of obfuscation that could have made the archbishop unsure of how to challenge Schrödinger’s appointment. In this respect, one is reminded of Lloyd George’s remark that negotiating with de Valera was like ‘… trying to pick up mercury with a fork’.

The second issue concerns Schrödinger’s legacy. On the one hand, he was an outstanding thinker who helped to revolutionise twentieth-century physics with his theory of wave mechanics and who laid the foundations for molecular biology. On the other hand, his legacy is sullied by his attraction to young girls and his apparent disinclination to control his sexual behaviour.

Brian Hopkins is Emeritus Professor of Psychology and Peter McClintock is Emeritus Professor of Physics, both at Lancaster University.

Further reading
P.V.E. McClintock, ‘Essay review: What is life?’, Contemporary Physics 53 (5) (2012), 433–5.
W. Moore, Schrödinger: life and thought (Cambridge, 1989).