John Barrow 


Title: Einstein's Universe of Universes Abstract: One hundred years ago Albert Einstein proposed a new theory of gravity that made it possible to study whole universes. Every solution of his famous equations describes a possible universe. We shall follow the trail of mathematical discovery that revealed a spectacular gallery of cosmic possibilities  expanding universes, bouncing universes, rotating universes, chaotic universes, inflationary universes, accelerating universes and multiverses  culminating in the current 'best buy' model for the astronomical universe we see today. Its structure poses new problems that remain to be solved by the astronomers, mathematicians and physicists of tomorrow. [Audioonly recording] 
Sir Roger Penrose 


Title: Light Cones, Black Holes, Infinity, and Beyond Abstract: A less appreciated revolutionary aspect of Einstein’s general relativity is the way in which gravity influences the very notion of causality in physical theory. Black holes are an extreme example, whose distorted causality prevents any kind of signal from propagating from the interior to the outside world. A similar situation arises with cosmological horizons, whereby communication becomes impossible from the most distant parts of the universe. This causality is provided by spacetime’s “light cones”, or conformal structure, the part of the metric not directly dependent on measures of time or distance but which governs electromagnetic and other massless signals. Conformal structure provides a new flexibility for an understanding of the infinite regions of the universe, its Big Bang and remote future, leading to a picture of the universe that is unorthodox, but well in accord with modern 