Invisibility Cloaks: How it works?

Whether you're a Harry Potter fan or a mere fourth-level mage in a game of "Dungeons and Dragons," you're probably familiar with the concept of an invisibility cloak. Slip this magical garment over your head and, in the eyes of 

all onlookers, vanish.

This sort of thing tends to fly unquestioned on the grounds of Hogwarts or in the umber-hulk-infested depths of the Underdark. But what about in the real world, where even the "Predator" aliens' clunky sci-fi camouflage looks far-fetched? Well Muggles, science has some good news for you: Invisibility cloaks are a reality. The technology is far from perfect, but we've already reached the point where you even get to choose from two different invisibility technologies.

On one hand, there's the optical camouflage technology developed by scientists at the University of Tokyo. This approach works on the same principles of the blue screen used by TV weather forecasters and Hollywood filmmakers. If you want people to see through you, then why not just film what's behind you and project it onto your body? Granted, it hardly matches up to the personal cloaking devices found in the likes of "Metal Gear Solid" video game series, but it produces similar (though more limited) results.

For a far more advanced approach, consider investing in a cloak made from metamaterials, tiny structures smaller than the wavelength of light. If properly constructed, such a cloak would actually guide rays of visible light around an object -- much like a rock diverting water in a stream. For now, however, the technology only works in two dimensions and only comes in the ultra-petite size of 10 micrometers across.

In this article, we'll explore both invisibility technologies, the science behind them and their possible applications outside of magical quests and sci-fi infiltration missions.