Welcome address, by Malcolm MacCallum 

Andrew Robinson (biographer) 


Title: Not So Sudden Genius Abstract: Einstein had his first inkling of how to generalise special relativity in 1907 while sitting on his chair in the patent office in Bern. Suddenly he realised that a man in free fall would not feel his weight: what he would later call ‘the happiest thought of my life’. But it took a long time to develop this thought experiment into general relativity. Looking back from the 1930s, he recalled 'years of anxious searching in the dark, with their intense longing, their alternations of confidence and exhaustion and the final emergence into the light'. They included his escape from the patent office, his inaugural professorship in physics, the first Solvay Congress, his move to the Prussian Academy, the outbreak of the First World War and his painful separation from his wife and children. I shall attempt to describe this eightyear intermingling of intellect and emotion that led to his breakthrough announcement in November 1915. 
Richard Staley (history of science) 


Title: On thought experiments, principles and their limits on the path to general relativity Abstract: Einstein’s early expositions of relativity placed considerable emphasis on a small number of principles that played an important role guiding his work to develop a general theory of relativity. This paper will focus in particular on the role of the equivalence principle of 1907 and “Mach’s principle,” which Einstein first articulated explicitly in 1918. In each case I will trace their prehistory to the research of Ernst Mach, showing that in addition to his wellknown critiques of Newtonian ideas and the bucket experiment, Mach’s approach had been shaped by physiological research on the perception of motion (importantly inspired by railways and mine lifts). Yet if Mach’s work helped Einstein focus on a small number of difficult thought experiments, what Einstein made of them was distinctive, and his understanding of each – and the principles he associated with them – changed considerably as he developed his approach to gravitation and the metric field. Following the work of previous historians, then, I will investigate the limits to the heuristic principles that guided Einstein by examining his repeated reconsideration of thought experiments on fall and rotating objects, as well as the mathematical tools he was able to bring to bear on these problems. 
Bangalore Sathyaprakash (gravitational waves) 


Title: Gravitational Waves: A New Tool for Observing the Cosmos Abstract: Gravitational waves were first predicted by Albert Einstein in 1916 on the basis of his theory of general relativity. In the next five years groundbased interferometers, such as advanced LIGO, advanced Virgo and KAGRA, are likely to provide the first direct detection of gravitational waves. This will constitute a major scientific discovery, as it will permit a new kind of observation of the cosmos, quite different from today's electromagnetic and particle observations. In this talk, we review the remarkable progress made over the last few decades at developing accurate signal models for the searches, so that we can take full advantage of the discovery potential of the detectors. We also discuss the unique astrophysical and fundamental physics information that we will be able to extract upon detection. [Split image in recording] 
James Hough (experimental gravity) 


Title: The Challenges and Controversies of Experimental Gravity Abstract: Experiments in the areas of gravity and General Relativity are among the most challenging and controversial in physics. In this talk I will touch on a number of areas, from the arguments over the measured value of G, through experiments to test the equivalence principle with increasing precision, the tests of GR including the results from GPB and Lageos, and the current searches for gravitational radiation. In particular I will discuss progress with the upgraded laser interferometer gravitational wave detectors, Advanced LIGO and Advanced Virgo, and with KAGRA, the cryogenic interferometric detector being built underground in Japan. [Split image in recording] 
Pedro Ferreira (cosmology) 


Title: Cosmology for the 21st Century Abstract: Physical Cosmology is the success story of modern physics. Observations of the largescale structure of the Universe have allowed us to characterize the cosmological model with unprecedented precision. I will review the recent developments with a particular focus on how much we have learnt about the largescale properties of spacetime and its origins. I will discuss the future prospects of cosmology, the open cosmological problems and ideas that may lead to a completely new understanding of general relativity and spacetime. [Patchy audio and split image in recording] 
Katy Price (English literature) 


Title: First Class Travel in Einstein’s Train Abstract: Trains were a staple of relativity exposition, offering an apparently straightforward analogy for a frame of reference in motion relative to observers at rest on the embankment. Einstein’s own example of dropping a stone from the carriage window led to more elaborate stories involving lightning flashes, gunshots, an Australian millionaire uncle and a runaway monorail travelling at the speed of light. As journalists, pulp authors, poets and novelists joined the conversation about new conceptions of space, time and gravitation, it became clear that there were different classes of travel on the “Einstein train”, with first class limited to those with highly specialised mathematical knowledge. This talk will visit the various carriages, to see what bourgeois and working class passengers made of relativity during the 1920s and 30s, with examples of relativity humour from Punch, Dorothy L. Sayers, P.G. Wodehouse and W.H. Auden. First class passengers may have disapproved of such illinformed chatter, but we will find that everyone was travelling to the same destination: a modern scientific culture in which theorists, journalists, storytellers and audiences all had a part to play in negotiating relativity’s meaning and significance. [Patchy audio in recording] 
Ramesh Narayan (astrophysics) 


Title: Black Hole Astrophysics Abstract: The black hole is an object which is so compact, and whose gravitational pull is so strong, that nothing, not even light, can escape from its interior. The black hole is one of the earliest and most celebrated predictions of general relativity, but it was for long considered nothing more than a theoretical oddity. This changed in the 1960s and 1970s with the discovery of quasars and Xray binaries, and the realization by astrophysicists that these amazingly powerful objects must have black holes at their centers. Today we know that the Universe is full of black holes, most weighing several times the mass of the Sun, but some weighing up to a billion times more. Even though light cannot escape from inside the event horizon  the putative "surface" of a black hole which demarcates the point of noreturn  gas flowing into a black hole does emit very intense radiation in radio waves, light, Xrays, and gamma rays, before falling through the horizon. Such radiation can be observed using telescopes on the ground and in space, and provides valuable information about astrophysical black holes. With improving technology, astronomers have been steadily probing closer and closer to the center. Within the next decade, we can look forward to direct observations of the region of strong gravity right next to a black hole's horizon. 
Mihalis Dafermos (mathematics) 


Title: The Contribution of Mathematics to General Relativity: Past, Present and Future Abstract: The contribution of mathematics to the original formulation of general relativity is of course quite well known, providing in particular the revolutionary new geometry on which the whole theory is based. The mathematical story of the theory does not however end with the definitive 1915 achievement of the Einstein equations. Throughout the subsequent development of the subject, progress in mathematics has been extremely influential in revealing several of the salient features of general relativity now taken for granted but not at all clear in 1915. Examples include the wavelike nature of the Einstein equations and its consequences, the notion of black hole and the ubiquity of singularities. This talk will survey the role mathematics has played in our basic understanding of general relativity and the big open questions in the subject that future developments in mathematics hope to resolve. 
Mike Duff (quantum gravity) 


Title: MTheory Abstract: The leading candidate for an allembracing theory of physics, one that would unify quantum mechanics and Einstein's general relativity and describe all physical phenomena from quarks to the Big Bang, is called 'Mtheory', where M stands for magic, mystery or membrane, according to taste. Mtheory brings together two strands in theoretical research: (1) 'Supergravity', an extension of Einstein’s theory involving 'supersymmetry’ that permits a maximum of eleven spacetime dimensions; (2) String theory, whose fundamental components are tiny vibrating strings. Is M really the final theory? Michael Duff will critically discuss the evidence. 
Harry Collins (sociology) 


Title: General Relativity's Sociological Spin Offs Abstract: General Relativity has had consequences beyond the natural sciences. It has formed the basis for extensive philosophical and sociological analysis of the nature of science and our understanding of science. I will start with a discussion of the controversy over the meaning of Eddington’s 1919 eclipse observations and move on to the spinoffs from gravitationalwave detection research. These include a better understanding of experimental replication, of statistics and of scientific expertise. Imitation Game experiments will be described in which nonexperts pretend to be experts in Turing Test like circumstances. 