PREFACE

In 1931, on the centennial of Maxwell’s birthday, Albert Einstein described the work of the Scottish physicist and mathematician as the most profound and the most fruitful that physics has experienced since the time of Newton. Einstein kept a photograph of Maxwell on his study wall, alongside pictures of Michael Faraday and Newton. James Clerk Maxwell is best known for formulating classical electromagnetic theory: This united all previously unrelated observations, experiments and equations of electricity, magnetism and optics into a consistent theory summarized by four partial differential equations. Importantly, Maxwell’s equations retain their form under coordinate changes and gave rise to the Einstein field equations of general theory of relativity. Einstein’s equations, published in a compact form in 1915, are a set of 10 (coupled and non-linear) equations describing the fundamental interaction of gravitation as a result of spacetime being curved by matter and energy. These tensor equations are also preserved when they undergo geometric transformations. In generalized coordinate systems, e.g. non-Euclidean metrics, they express that light follows curved trajectories along geodesics. In this way, the flow of light in spacetime is detoured around massive cosmological objects such as heavy planets or black holes (in the latter case, light is ultimately absorbed if it enters the so-called event horizon, but that’s another story). The tour de force of British physicist Sir John Pendry was to recognize in 2006 that one can markedly enhance control of light trajectories on the scale of the human laboratory by designing metamaterials whose permittivity and permeability curve the electromagnetic space, whereby the time variable only plays the role of a parameter. This original proposal opened new vistas in photonics, e.g. with the fast growing field of cloaking. However, James Clerk Maxwell is also known for other seminal works, such as for presenting the first durable colour photograph (using the principle of threecolour analysis and synthesis, the basis of nearly all subsequent photochemical and electronic methods of colour photography) during an 1861 Royal Institution lecture on colour theory. Moreover, Maxwell is also recognized for his foundational work on the rigidity of rod-and-joint frameworks like those in many bridges. The latter scientific legacy is maybe less well known, but is of foremost importance as it underpins the parallel developments in electromagnetic and acoustic metamaterials. The