Invisibility Achieved

At the beginning of August, About Physics reported on a physicist that predicted invisibility machines was a physical possibility. At that time, I said that I'd believe it when I saw it...

Well, I haven't seen it yet, but it's apparently happened. Physicists at Duke University have reported that they've created a process to bend microwaves around an object with virtually no distortion, thus making the object effectively invisible, or cloaked, when observed at that range of frequencies.

The object cloaked in this manner was a copper cylinder. By creating a series of concentric circles made out of metamaterials, which influence the electromagnetic waves in complex ways that don't occur in nature, the microwaves were broken apart and then reformed on the other side of the cylinder in such a way as to "resemble free space."

The invisibility is not yet perfect; there's still some distortion in the microwave range. Also, it only works at a specific frequency of microwave radiation, but this proof that the theory is sound will result in more work. Though such devices may have applications, true invisibility is still a long way off, as it would have to affect the entire range of visible light at once.

In 2001, David Smith, the Duke University researcher who created the cloak, worked with metamaterials to create a "lens" with a negative refractive index, impossible with ordinary optical lenses. According to Ulf Leonhardt of the University of St. Andrews in Scotland, the microwave cloak is actually easier to construct than the negative lens.

Related Articles

• Science - abstract of Metamaterial Electromagnetic Cloak at Microwave Frequencies (subscription required for the full paper)
• USA Today - Now You See It: 'Cloak of invisibility' tested
• New Scientist - Working invisibility cloak created at last
• Photonics Online - First Demonstration of a Working Invisibility Cloak
• About Physics Blog - The Invisibility Machine