An invisibility cloak is one step closer to reality, with a group of German and British scientists reporting that they've successfully created a prototype that works in three dimensions.
Previous attempts have worked only in two dimensions, so that observers only had to crane their head a little to see the supposedly invisible object.
Researchers from the German Karlsruhe Institute of Technology and Imperial College London used photonic crystals to conceal a small bump on a gold surface.
Admittedly, the bump was pretty hard to see anyway -just 0.00004 inches high by 0.00005 inches across.
The cloak is made of a polymer crystal containing tiny pockets of air, and can be given a variable refractive index by altering the ratio of air to polymer.
In its present form, the cloak works only for one particular set of wavelengths, in the infrared part of the spectrum, and is clearly pretty tiny. But the design is in theory completely scalable, so that the research represents a solid proof of principle, says the team.
Details appear in Science.