Vale Noel Hush, 1924–2019

Noel Hush, who died on March 20 at the age of ninety-four, was an Australian theoretical and computational chemist who became one of the great scientists of his times. He was also dedicated to the preservation of liberal and conservative values in Australian society, a political position he pursued through his membership of the board of directors of Quadrant since 1998. At a memorial service in the Great Hall at the University of Sydney on May 27, his friends and colleagues recalled his numerous achievements. We publish here tributes from Max Bennett and Jeff Reimers.

Max Bennett

Forty-eight years ago, I received a telephone call at my office and laboratory in the basement of the old medical school at Sydney University (Anderson Stuart Building) inviting me to supper in order to meet Walter Moore. This was a surprise, as I did not know the caller, the recently appointed professor of theoretical chemistry, Noel Hush. However, I knew who Walter Moore was, as he had published a superb textbook on physical chemistry and later an even more wonderful and highly praised biography of Erwin Schrödinger, the genius with a somewhat scandalous reputation who was the co-discoverer of quantum mechanics with Heisenberg. When I joined these colleagues in a private room in St Paul’s College on the campus of the University of Sydney, I soon discovered that I had much more in common with Noel Hush than with Walter Moore, as both of us loved the history and philosophy of science and indeed philosophy in general. From then on, until his death at ninety-four last March, we regularly met and had lunch. He became my mentor, guiding me through the vicissitudes of university politics and reminiscing about his momentous life as a theoretical chemist, peppered with colourful anecdotes of great scientists.

Noel loved Sydney University, in which he had been for forty-eight years a professor, first in chemistry and later as emeritus, for it had given him a great head start both as an undergraduate and graduate during the Second World War. He felt extremely lucky that his early graduate years were spent in the company of those few members of staff still active at the university during the war, some of whom had recently worked in America in the school of Linus Pauling, that double Nobel Prize winner of magisterial status, who had brought the Schrödinger theory of the wave equation into quantum mechanics to illuminate at the fundamental level various molecular processes. Noel found this very exciting, absorbing the complex methodology with skill and application, and going so far as to audaciously challenge some of Pauling’s ideas, in which Noel proved to be correct.

Such publications, while he was still in his twenties, brought international recognition, leading to an invitation to take a junior lectureship at Manchester University, applying quantum mechanics to molecular reactions. The department was dominated by the young Meredith Evans and the great chemist and polymath Michael Polanyi. So Noel joined them with much pride and pleasure, expanding his interest and understanding of how electrons in the outer array of electrons to be found in atoms could be transferred from one atom to another in the process of oxidation-reduction, at the heart of so many phenomena in nature such as photosynthesis.

Why, one might ask, did Noel go to Manchester rather than the great universities of Oxford or Cambridge? Noel explained to me that Manchester was in fact a great university, with many jewels in its crown besides Polanyi. The philosopher Ludwig Wittgenstein, who we both admired greatly, at first studied and carried out research at Manchester around the early part of the twentieth century on first arriving in the United Kingdom from Vienna, where he had graduated in engineering. Indeed, we discussed the extremely novel designs Wittgenstein had produced for a propeller in his graduate research in aeronautical engineering. Following Wittgenstein, the New Zealander Ernest Rutherford, probably the greatest experimental physicist of the twentieth century, had been professor of physics there, shortly after showing that the atom consisted of a core or nucleus surrounded by a comparatively enormous amount of space in which a few electrons rotated around the core.

But the cream on the cake at Manchester for Noel was his lunches with that genius Alan Turing, about ten years older than Noel, the inventor of the theory of the computer, and the leader of the group that famously broke the German Enigma code during the Second World War, with all that meant for the survival of the United Kingdom. More particularly, Turing was engaged at the time of meeting Noel with the development of sets of differential equations that could provide a theoretical framework for morphogenesis, the diffusion and reaction of molecules with cells that could generate a three-dimensional structure such as a hand or, for that matter, the patterns of stripes on a zebra. Noel had qualms about these equations and went into collaborative argument with Turing on their applicability. It hit Noel very hard when Turing committed suicide, a tragedy now read as due to the way he was treated by the British authorities on their discovering his homosexuality.

By this time, Noel, still in his early thirties, was establishing a wonderful reputation, at first in collaboration with Meredith Evans in the Manchester Centre, a collaboration that was tragically cut short by Evans’s early death. Noel then went in 1955 to Bristol where he became reader in organic chemistry. His marvellous contributions in developing adiabatic electron transfer theory and in photosynthesis led to his appointment at Sydney to the first chair in Australia devoted to theoretical chemistry. Here he opened up the new field of molecular electronics, enabling the manipulation of molecules to act as components in devices, which in turn led to the much-celebrated field of nanotechnology.

Hush’s command of quantum mechanics enabled him to elucidate what brought certain types of chemical reactions about and to design experiments to check the validity of his theories, some of which he performed. His theoretical work and the design of such experiments led to others carrying out experiments and interpreting them in ways dependent on Noel’s insights. This was acknowledged, for instance, in the Nobel Oration in chemistry by Henry Taube in 1983.

It came as a great surprise to me and many others when the Nobel Prize for Chemistry was awarded to Rudolph Marcus in 1992. Marcus was working in the very field in which Noel had made such momentous contributions, that is in “The Theory of Electron Transfer Reactions in Chemical Reactions”, involving the transfer of outer sphere electrons around the nucleus. This had justifiably been named “The Marcus-Hush Theory of Outer Sphere Electron Transfer”, given Noel’s contributions, and there is no doubt that Noel should have shared the Prize. Noel, in all the years I have known him, never showed any bitterness over this sad reflection on the Nobel Committee. For Noel it was the search for knowledge and understanding that brought the highest pleasure, though it was wonderful to see him receive, in 2007, the Welch Award in Chemistry for basic chemical research for the benefit of mankind, the pre-eminent prize in the subject. Noel asked me to appear on his behalf in a documentary made for the Welch Foundation by a crew that flew out to Sydney. I was able to bring to bear my perspective on the originality and analytical skills of this extraordinary man.

Noel’s mastery of quantum mechanics and his interest in philosophy naturally made him curious that the great mathematician Roger Penrose, the mentor of Stephen Hawking, should claim to have a theory that would bridge “the gap”, as it were, between the counterintuitive world of quantum mechanical phenomena and that of another “mysterious” phenomenon, namely consciousness. Penrose and his colleague Hameroff have proposed that this bridge can be found in the workings of microtubules, the threads twenty-five nanometres wide that make their way through the neuron and all its processes, acting as railway tracks for the delivery of materials from the neuron cell body to the axon s, which can be up to a metre or so away, and that have been the basis of much speculation since their discovery in the nineteenth century. Hush and Jeff Niemens showed that there were fundamental errors in the Penrose–Hameroff theory. The now newly established institute by Penrose, devoted to the theory of the tubular basis of consciousness within a quantum mechanical framework, places the Hush–Niemens criticisms to one side. This is something that no doubt Noel would have responded to with glee, relishing the opportunity to once more enter into argument with a first-class adversary, as Noel understood that it is only through such duelling that ignorance is dispelled and understanding advanced.

Noel was held in near reverence at Sydney, because of his renowned contributions to the fundamental subject at the heart of many natural phenomena that we see about us, and as embodying the heroic age of quantum chemistry. One searches for a phrase that might aptly catch the qualities of this unique scholar, and the one that comes to mind, which is seldom used, is that “Noel was a really lovely man”.

Max Bennett is Professor of Neuroscience, Sydney Medical School University Chair, University of Sydney.

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Jeff Reimers

The science of quantum mechanics provides basic understanding as to how atoms bind together to make molecules, proteins, DNA, plastics, materials, electronic devices, solar-energy converters, to name just a few. Within a decade of the birth of quantum mechanics in 1926, most of the basic understanding of chemistry as we now know it was laid down. By the mid-1940s when Noel Hush was a student at Sydney University, classic textbooks had been written, texts we would be happy to teach from today. In the post-war years, the prospects for a better world seemed endless.

His first paper, as a Sydney University MSc student in 1947, was on the hot topic of how polymers formed, published in the top journal Nature. In those days, top graduates did not apply for jobs. Heads of departments wrote to them, offering positions.

And so it came to pass that Meredith Evans, Professor of Physical Chemistry at Manchester University, invited Noel Hush there in 1949. This was the best place for this type of work in Europe at the time, and definitely a centre of real action.

“Batteries!” Evans told Hush, were the future, yet nobody really understood how they worked. From 1952 until 1975, Hush put together his famous theory of electron transfer—how electrons move from one object to another. It applies not just to 1950s batteries, but also to the lithium batteries powering today’s mobile phones, computers and cars.

But there was more. Quantum mechanics shows that light and matter are closely related, obeying the same basic laws. So incoming light can cause electrons to move inside molecules, and moving electrons in molecules can create light.

Hush’s theory for batteries explained the colour of Prussian blue, the first modern synthetic pigment, invented in 1709, used in clothing dyes, paintings and blueprints. It should have been colourless, not blue. Hush showed that the colour was caused by pumping electrical charges within the material. Harnessing this process has led to modern organic and dye-sensitised solar cells.

His 1968 quantum theory also predicted that an electron could be half on one molecule and half on another, even if a third molecule was in between. This was a revolutionary understanding. The next year, Henry Taube synthesised a structure displaying this property, getting him the 1982 Nobel Prize.

A critical feature of Noel Hush’s work was the belief that one day computers would allow large numerical simulations of chemical systems based only on the equations of quantum mechanics. In the 1950s, these notions were considered ridiculous. Upon starting in 1972 at Sydney University, Professor Hush engaged an expert, George Bacskay, as a collaborator. Together, they pioneered many software developments that are today standard practice. In 1989, I also started to collaborate with him, developing new applications.

Then he had a vision that one day molecules could replace silicon in electronic circuits, a field known as “molecular electronics”. His theories, zeal and support through funding initiatives and conference organisation encouraged many workers around the globe. Over the last five years, many Australian universities have attracted top young overseas talents in this area. Professor Hush’s vision lives on.

He and I worked together for twenty years on understanding photosynthesis. Nothing is more quantum than the way plants convert sunlight into chemical energy—Noel Hush’s equations at play, molecular electronics in action.

I had joined Sydney University in 1985 as a junior research fellow. This was the opportunity to live my dream and work on one of the most important problems of the nanotechnology era—improving the Second Law of Thermodynamics. However, I had neither the expertise nor the resources to take on such a task. One has to have a dream, but dreams don’t pay the mortgage. After three years and no papers and no future, I was asked by Professor Hush to do some (for me) simple calculations related to molecular electronics. This saved my career.

He taught his colleagues some key things:

• You have to work on something that is important.
• Only take on what you can finish.
• Just because it is easy to you does not mean that it is boring.
• Always take on new challenges.
• Always keep learning.

His second-last paper was submitted the day of his death, his first paper on the hot topic of attosecond spectroscopy—chemical processes occurring in one millionth of one millionth of one millionth of a second. His last paper, a review of his life’s work, will be completed shortly—I promise.

He may no longer be with us, but his papers will be around for a very long time, along with his inspiration of others.

Professor Jeff Reimers holds a joint appointment in the School of Mathematical and Physical Sciences, University of Technology Sydney, and the International Centre for Quantum and Molecular Structures, Shanghai University