goombah99 writes "Cloaking of broadband light, ala the Romulans, has been shown to be impossible for passive, locally responsive media (i.e. No Acme invisible paint). Recently, Sir Pendry et al showed that a hollow thick shell of negative refractive index material will act as cloaking device for objects placed in the interior. A difficulty with that system is that at present broad waverlength negative index matrials are not possible. Now, David Miller describes in Optics Express a active system can be built using some simple math that would give the appearance of a cloaking for broad wavelengths. It would not be useful against temporal probes like Radar, but would give the illusion of looking through the volume of space when viewed from any angle. He discusses how simplified systems which approximate cloaking are also possible using local response properties (i.e. Acme quasi-invisible paint)."