Jim Falk recalls Alan’s work as a physicist and ecologist
In other comments on Alan’s political life much has been said about his integrity and courage, but the same qualities also characterised his intellectual work – notably as a professional physicist where he made some interesting and important contributions.
His early work was for his PHD in the early 1960s where he founda method within quantum mechanics to calculate the way in which electrons would behave in disordered materials. Working with his supervisor REB Makinson he was able to show that the electrons would become trapped by the disorder.This was very early to be wrestling with the implications of disorder – and the work was at the very roots of what would later become the huge field of chaos theory – which deals with that majority of nature which has randomness at the core of its dynamics.
In 1972 he published an article with two colleagues on“Non-velocity Redshifts and Photon-Photon Interactions” in the prestigious journal Nature. It proposed an explanation for why the light coming from distant galaxies which were visibly linked by matter could show completely different shifts towards the red-end of the spectrum. Of course the usual explanation of these red shifts was that they were caused by the speed at which stars were receding from us due to the expansion of the universe. But that could hardly be the case for the seemingly linked galaxies. So they suggested that light could be being slowed as it bashed its way through the light from other stars on the way to us. It was an extremely bold hypothesis (although ultimately as provocative as it was probably wrong) – so bold that Nature editorialised about its potential significance.
Later Alan would turn his considerable mathematical insight to the study of life, and in particular evolutionary theory. Here he tackled the thorny question that evolutionary systems theorists were puzzling about. In reality it appears that bio systems with lots of interacting species are more stable than ones with very few. And this makes sense. At first sight, a system with few species should be much more vulnerable to a single species loss than ones with many and that appears to be the case. But when these were modelled mathematically instability seemed to increase with the number of interacting species. Alan was able to show that the previous models allowed a process of evolution that tacitly produced negative populations. By restricting his calculation to species populations that were what he called “feasible” he produced a theory that conformed much more closely to reality.
Alan was incurably curious, bold, generous, warm and sharply and quickly intelligent. As a friend, activist and as an intellectual – including as a cutting edge scientist – Alan will be long remembered.
Jim Falk has taught physics at a number of Australian universities, is emeritus professor at the university of Wollongong and an honorary professorial fellow in the Melbourne Sustainable Society Institute, at The University of Melbourne.