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Professor McCall is Professor of Theoretical Optics in the Physics Department at Imperial College London and Chair of Quantum Electronics and Photonics Group at the Institute of Physics. His research into negative index media led to the theoretical proof of space-time invisibility cloaks, hiding events rather than just objects.

Professor McCall was invited to speak to students from The Judd School’s Physics Society. His talk was entitled ‘Beetles, Black Holes and Editing History’.

Professor McCall’s talk described how we have recently discovered how to manipulate light in ways that were only dreamt of a few years ago. The talk began with some simple ideas about electric and magnetic fields. A student correctly identified a picture of a distinguished-looking bearded scientist as James Clerk Maxwell, whose famous equations predicted that light is electromagnetic radiation. Professor McCall showed how materials respond to electric and magnetic fields giving rise to the ‘refractive index’ that students study in ‘A’ level. Less familiar, however, is the concept that refractive index can take negative values leading to the remarkable possibility of making lenses that are in principle ‘perfect’. Professor McCall showed the students how these ideas are quite controversial, with scientists disagreeing over whether it was possible for gravity around black holes to refract in this special way. 

Professor McCall also demonstrated double refraction in Calcite, and how helical index structures found in beetles are revealed by their changing colour when viewed with 3-D spectacles. Everyone is always enthralled to hear about how we have recently developed ideas enabling us to make Harry Potter-style cloaks that really do make objects invisible so the talk concluded with a description of Professor McCall’s research on how to make a cloak in time, rather than space, a so-called ‘History Editor’. 

Following the talk, the event organiser said: “Professor McCall’s talk was very well delivered and entertaining. The display of the beetles using 3D Glasses was particularly enjoyed and the subject itself was fascinating.”