Dennis Sciama Memorial Lecture
This year's lecture
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Lorenz, Gödel and Penrose: New perspectives on determinism and unpredictability, from fundamental physics to the science of climate change. Tim Palmer (Oxford)1 March 2013 in Oxford, 22 May 2013 in Trieste Lorenz is one of the pioneers of chaos theory. However, over 50 years before Lorenz, Poincaré discovered the sensitive dependence on initial conditions that characterises chaos. So what makes Lorenz's contribution so important? I argue it is the discovery of the fractal invariant set in state space: the Lorenz attractor. Quite amazingly, properties of the Lorenz attractor can be shown to link the calculus of dynamical systems theory to deep and diverse areas of mathematics such as Wiles' proof of Fermat's Last Theorem and Gödel's incompleteness theorem. But more than this, I argue that the fractal invariant set has implications for physics - not only for practical problems such as climate prediction, but also for the deepest problems of fundamental physics. In particular, I will put some meat on the bones of Penrose's suggestion that "the correct theory of quantum gravity might be a deterministic but non-computable theory" by treating the Universe as a dynamical system with fractal invariant set. The result is a novel perspective, not only on the quantum gravity programme, but also on quantum physics in general. |
Dennis Sciama (1926-1999) played a pivotal role in the development of modern cosmology and relativistic astrophysics both through his own work and through being the mentor of a large number of research students and colleagues who then went on to become leading figures in their own right. He was head of the Astrophysics Sector of SISSA from 1982 - 1998, first jointly with Nicolò Dallaporta and then on his own. During those years the group grew to become a major world player in astrophysics research, particularly in the areas of relativistic astrophysics and cosmology which were his main interests. Before coming to Trieste, he had led similar groups in England, first at Cambridge and then at Oxford.
The memorial lectures are an occasional series with each lecture being given by a leading world expert, focusing on topics which were of particular interest to Dennis. Each lecture is normally given twice, once in Trieste and once in Oxford.
A Dennis Sciama's short biography
Dennis Sciama was a research student of Paul Dirac in Cambridge just after the second world war, working on Mach's principle - the idea that the nature of local physical laws is affected by the state of the whole Universe. He became passionately involved with developments in cosmology and relativity theory, interacting particularly with Hermann Bondi, Thomas Gold, Fred Hoyle and Felix Pirani and becoming for a while a committed advocate of the Steady-State theory of the Universe until eventually abandoning it in the face of mounting contrary observational evidence and switching allegiance to the Big-Bang picture which then became standard. He then became a pioneer of investigating astrophysical processes in the evolving and expanding universe, making full use of his extremely broad knowledge of basic physics to make fruitful links between different areas. His interests spanned studies of anisotropies of the microwave background, the structure of radio sources and quasars, X-ray astronomy, the physics of the interstellar and intergalactic medium, astroparticle physics and the nature of dark matter. Perhaps most significant of all was his advocacy of relativistic astrophysics, the study of black holes and the interaction between quantum theory and general relativity. The group which he led in Cambridge in the 1960s (including George Ellis, Stephen Hawking, Martin Rees and Brandon Carter) and his links with Roger Penrose, were immensely influential in this. After Cambridge, he subsequently led groups in Oxford (1970s and early 1980s) and at SISSA (1980s and 1990s), carrying on the earlier traditions and creating an ever-expanding "family" of students and collaborators. Well-known students from these later years include John Barrow, James Binney, Philip Candelas and David Deutsch.
He is remembered particularly for the excitement in doing physics which he communicated to those around him, for his charismatic lecturing and for his books ("The Unity of the Universe", "The Physical Foundations of General Relativity", "Modern Cosmology" and "Modern Cosmology and the Dark Matter Problem") which have been of great importance for introducing many people to these subjects.
Past lectures
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From Planets to Universes Martin Rees (Cambridge)11 November 2011 in Oxford, 16 April 2012 in Trieste |
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Black Hole Research: A New Golden Age Kip S. Thorne (Caltech)25 May 2011 in Trieste, 27 May 2011 in Oxford |
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Astrophysical Black Holes and E = Mc2 Marek Abramowicz (Göteborg/Warszaw)3 June 2010 in Trieste, 19 November 2010 in Oxford |
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Mach's Principle as the Universal Basis of Dynamics Julian Barbour (Oxford)12 November 2009 in Trieste, 27 November 2009 in Oxford |
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The Constants of Nature John Barrow (Cambridge)21 April 2008 in Trieste, 21 November 2008 in Oxford |
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The Origin of the Universe Stephen Hawking (Cambridge)in Oxford with an interactive audio-visual link to Trieste, 24 February 2006 |
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Cosmology and Local Physics George Ellis (Cape Town)14 November 2003 in Trieste, 21 November 2003 in Oxford |
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What do Black Holes and the Big Bang tell us about the nature of Quantum Mechanics? Roger Penrose (Oxford)25 January 2002 in Trieste, 13 May 2002 in Oxford |