Darwin College Lecture Series 2010. "Risk and Natural Catastrophes" by Professor Mark Bailey( Armagh Observatory)Natural catastrophes rare, high-consequence events present us with a unique conjunction of problems so far as risk is concerned. First, they can have an extremely long recurrence interval, so long that the greatest may not have occurred within living human memory. Secondly, the effects of events with which we are all too familiar, for example earthquakes, floods, volcanoes and storms, are easily trumped by the impacts of objects comets and asteroids that reach Earth from outer space; and thirdly, the largest of these events have a global reach, in principle threatening not just our civilisation but perhaps life on Earth itself. However, recognising that such events occur very rarely, should we make hay while the sun shines and ignore, ostrich-like, the significant actuarial risk; or should we seek to understand the phenomena and develop strategies to mitigate the threat and perhaps technologies to avert it? Our response often depends less on a purely rational assessment than on personal circumstances and how we have been brought up, but in any case, the nature of the risks, which are poorly understood, means that we must be prepared to handle the law of unintended consequences (i.e. could our actions make things worse?). We must also be prepared to explore what happens if, perhaps inevitably, our current scientific understanding turns out to be less certain than many experts believe.BiographyProfessor Mark E. Bailey MBEAstrophysicist and Director of Armagh Observatory. He obtained his PhD at the University of Edinburgh in 1978 with a thesis on the evolution of active galactic nuclei. In recent years his research has focused on areas closer to home: the dynamical evolution of comets, asteroids and meteoroid streams; solar system terrestrial interrelationships; and aspects of the comet and asteroid impact hazard. The asteroid (4050), discovered in 1976 by C.-I. Lagerkvist, was named Mebailey in March 1990 for his work on the dynamics and origin of comets. He is the co-author of `The Origin of Comets (Pergamon, 1990).