How Far Away Are Active Invisibility Cloaks?

Despite the Harry Potter headlines they've inspired, efforts over the last few years to create a real-life invisibility cloak have been simple proofs of concept. They're lab experiments, and not the kind of thing that could mask a troublesome young wizard lurking in a library, much less a soldier on the battlefield. But in those early successes, some scientists see the potential for active cloaking technology that could hide objects in plain sight.

According to University of Texas researcher Andrea Alù, a battery-powered (or active) cloak composed of metamaterials might prevent a broadband radio signal from scattering off a target, an important step towards making objects undetectable to the human eye.