The image of the physicist as someone who is able to perform miracles with an incomprehensible theory has stuck ever since Arthur Eddington observed in his famous 1919 expedition that the position of the stars changes during a solar eclipse, in accordance with Einstein's then new general relativity. Indeed, according to Arthur C Clarke any sufficiently advanced technology is indistinguishable from magic. Few examples illustrate this better than the recent prediction by two independent groups that materials with exotic electromagnetic properties can make an object disappear. Even more intriguingly, it seems that the best way to actually engineer such an invisibility device is to follow the mathematics of general relativity (arXiv.org/abs/cond-mat/0607418).
Invisibility has inspired countless myths, novels and films – most recently involving Harry Potter. It is important to realize, however, that invisibility is not the same as transparency. H G Wells’ Invisible Man, for instance, makes himself transparent by inventing a recipe to make his refractive index uniform so that light cannot be scattered or absorbed in his body. In contrast, the Invisible Woman character creates a field that distorts space a bit like the way in which Einstein’s gravitational field warps space–time. Her field is cunningly designed to smoothly guide light around her so that she remains hidden whatever she does. In the September issue of Physics World, Ulf Leonhardt and Thomas Philbin describe how this approach to invisibility has allowed a team led by John Pendry of Imperial College in the UK, and, independently, Leonhardt himself to develop the scientific concepts for a bona fide invisibility device.
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