Schrödinger in 1943 — Luke O’Neill

#whatislife75
Sep 4, 2018 · 7 min read

In 1939, Eamon de Valera, who at that time was Taoiseach (Prime Minister) of Ireland, had the idea of establishing in Dublin an Institute for Advanced Studies.

He was inspired partly by the Princeton Institute for Advanced Studies, where Einstein had been recruited. The Dublin Institute for Advanced Studies (DIAS) would be the Irish State’s first attempt since independence to directly support scientific research, and during a debate in Dáil Éireann (the principal chamber of the Irish parliament) De Valera said, ‘The name of Hamilton is known wherever there is a mathematical physicist. This is the country of Hamilton. We have the opportunity of establishing now a school, which I think will enable us to achieve a reputation in that direction comparable to the reputation which Dublin and Ireland had in the middle of the last century’ De Valera had to be brave (a trait we long for in our politicians). The opposition party was scornful and accused him of trying to ‘satisfy his vanity with a pretence of scholarship’. De Valera was adamant however, and became Minister for Education — whilst also holding the post of Taoiseach — in order to push the bill through. Ireland at that time was a relatively poor country, with few students making it to second level education, much less third level, and yet here was a bold plan. De Valera chose two subjects for DIAS which wouldn’t require expensive equipment: theoretical physics and Celtic studies. The question arose regarding who would be the first director, and, through various contacts De Valera managed to recruit Erwin Schrödinger to the post. De Valera was overjoyed. Here was a Nobel Prize-winning physicist whose work on the wave equation had used the Hamiltonian function. Schrödinger himself, who at that time was a political refugee, escaping the Nazi rule in Austria, is on record as saying that he was delighted to come to the city of the illustrious Hamilton.

As part of his role as director Schrödinger had to give an annual public lecture, and in 1943 he chose the topic ‘What is Life?’. This was a gamble, as Schrödinger was a physicist straying into biology. The question, however, intrigued him. He was inspired by a famous paper published in 1935 by Delbruck, Timofeef-Ressovsky, and Simmer — in which the authors described an experiment in which they irradiated fruit flies with X-rays to create mutations. They calculated the minimum amount of radiation needed to cause a mutation, and from that calculated that a gene had a physical size which Schrödinger interpreted as being ‘a thousand atoms’. At that time it wasn’t known what genes were made of, and the Delbruck paper inspired Schrödinger to consider the physical nature of the gene. Physicists were sceptical of Schrödinger’s interest in biology; Ernest Walton was a physicist in Trinity at that time (he shared the Nobel Prize for Physics in 1951 with John Cockcroft for their work at Cambridge on splitting the atom), and he attended the What is Life? lectures. In a letter written in 1966 reminiscing about Schrödinger he wrote: ‘I attended the course which became the basis for What is Life?’ It was very well attended throughout and created much interest, but I was just a little doubtful about his wisdom in wandering into biological fields. I remember sitting close to him at lunch one day when the conversation turned to biological topics. Possibly it was at a time he was contemplating What is Life?. He pointed out how he had inherited the somewhat unusual shape of his nose from his grandfather and that the gene responsible for it must have been maintained at a constant temperature to within a few degrees for about a century’.

Schrödinger approached the question from the perspective of a physicist and first of all considered the mechanism of heredity, prophetically proposing that the gene was an ‘aperiodic crystal’. The term came from the fact that a gene had to be stable for it to be passed to the next generation, but also had to contain information. A periodic crystal (which, as Schrödinger says in his book What is Life?, physicists ‘Have hitherto dealt with’) would be too simple to instruct the complexity inherent in living systems and so we get the key line in What is Life?: The most essential part of a living cell — the chromosome fibre — may suitably be called an aperiodic crystal’. In 1953, Francis Crick sent a reprint of his and James Watson’s famous Nature paper to Schrödinger in Dublin, writing: ‘We thought you might be interested in the enclosed reprints — you will see that it looks as though your term ‘aperiodic crystal’ is going to be a very apt one’

Equally importantly however, Schrödinger was also the first to discuss in lectures the possibility of a genetic code, and was the first to state such a concept in clear physical terms. The second major topic which actually took up two thirds of the content of the lectures concerned the thermodynamics of living systems; an area where much has still to be learned, and which was overshadowed by the huge advances that happened in genetics and molecular biology since Schrödinger’s lectures. Schrödinger discussed ‘Negative entropy’ as a critical feature of life, and later wrote: ‘If I had been catering for physicists alone I should have let the discussion turn on to free energy instead. But this highly technical term seemed linguistically too close to energy’. What is clear however is the fact that a famous physicist, writing about biology, inspired many physicists and chemists to consider biological questions — particularly at a time when the Manhattan project had disenfranchised so many physicists. As a direct result of What is Life?, therefore, the field of molecular biology was born. In some ways, though, we have been seduced by DNA. Perhaps the next 75 years will see more progress in our understanding of the questions raised in the rest of Schrödinger’s lectures.

Some of the ideas in the book have been criticised as derivative or wrong. Even at the time of publishing, Schrödinger himself knew of his limitations: ‘That some of us should venture to embark on a synthesis of facts and theories, albeit with secondhand and incomplete knowledge of some of them — and at the risk of making fools of ourselves’. He deserves huge credit for embarking on such a venture however, as his ‘little book’ (as Francis Crick referred to it) acted as a catalyst for further development, encouraging new approaches to biological questions. Much of the astonishing success of molecular biology over the past 75 years can be traced to the What is Life? lectures given at Trinity College Dublin in 1943, during the darkest days of World War II. Similar to the times of the Irish monks and the Book of Kells; an isolated country on the margins of western Europe played its part in the future development of the world as we know it.

And so we come to Schrödinger at 75. Ireland can no longer be considered isolated, but across the world we are perhaps yet again living in dark days. What might we expect from our ‘Little conference’? I highlight five of our illustrious speakers: Svante Pääbo has used a piece of technology (the automated DNA sequencer) championed and developed by another of our speakers, Leroy Hood, to do some time travel and look deep into our past by sequencing Neanderthal DNA; proving beyond doubt that we Homo sapiens interbred with Neanderthals. This may have helped build our immune systems; and these studies provide us with insights into who we are and where we come from. Beth Shapiro will offer another perspective on paleogenomics, and will provide insights into what we can learn from extinct species. Her book, How to Clone a Mammoth: The Science of De-Extinction, provides a picture on what will be required scientifically to resurrect extinct animal species.

Hood himself is, in many ways, trying to follow Schrödinger’s lead; not with the DNA question alone but beyond into systems biology, which brings with it a whole new way of looking at the complexity of life. That complexity also involves our bodies having a roughly 24 hour, ‘circadian’, rhythm controlled by a built-in clock; the molecular nature of which was uncovered by Michael Rosbash — who revealed that we really are just machines running to a clock’s relentless ticking. We are very elaborate machines however with at least five senses; the molecular nature of one — the sense of smell — being worked out by Linda Buck. Her research explained how our sense of smell works, providing us with a fundamental understanding of the machinery that controls the relay of sensory signals from the world around us to the central nervous system. And who might bring us an integration of all this complexity? Phillip Campbell, former editor of Nature, may do just that, having overseen the publication of the greatest discoveries in science over a number of years. Might he help us handle the cacophony of all that discovery?

I’m left asking: what would Schrödinger make of all of this if he were around today? He would no doubt be overjoyed to think that his lectures inspired all this great science. Perhaps we are getting closer to achieving what he hoped for in the preface to What is Life?: ’We feel clearly that we are only now beginning to acquire reliable material for welding together the sum total of all that is known into a whole’. My hope is that the presentations at this 75th anniversary conference go some way to this seemingly impossible goal.

Luke O’Neill (Trinity College Dublin) is an organiser of Schrödinger at 75 — The Future of Biology. The conference takes place on Sept 5th and 6th in the National Concert Hall, Dublin, and you can watch it live here.

#whatislife75

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Marking 75 years since Schrödinger's iconic 'What is Life?' lectures at Trinity College Dublin.