Cloaking Device

Guardian Unlimited: Now you see it, now you don't: cloaking device is not just sci-fi:

The cloaking device relies on recently discovered materials used to make superlenses that make light behave in a highly unusual way. Instead of having a positive refractive index - the property which makes light bend as it passes through a prism or water - the materials have a negative refractive index, which effectively makes light travel backwards. It's light, but not as we know it.

Prof Milton's team calculated that when certain objects are placed next to superlenses, the light bouncing off them is essentially erased by light reflecting off the superlens, making the object invisible.

The calculations show that while the device could be used to obscure almost any shape of object, it only works over a short range of wavelengths, so if used to hide objects from human vision, they might only partially disappear.

Seems like a good opportunity for ghost sightings in the distant future.