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Reversing time promises invisibility

  September 15/22, 2008
Bounce light off the right material surrounding an object and the beams reverse course and return toward their source as though you were running time backwards. Reflect the reversed light off an ordinary mirror and you can make the object disappear.

The mirror sends the beams in their original direction but angled inward toward each other. By making the beams converge at the right point you can make them bend around the object rather than bounce off of it. This makes the object invisible by creating the illusion that the light has passed through it.

This time-reversal-and-mirror process mimics bending the lightwaves backwards as they hit the surrounding material. Bending lightwaves backwards -- negative refraction -- is a method researchers have been studying to develop invisibility shields, but making negative refraction materials that work for more than a narrow range of wavelengths is extremely challenging.

The time reversal technique offers a new route to practical invisibility shields. Time reversal could also be used to make more powerful magnifying lenses. The technique can also be used with sound waves.

Research paper:
Time Reversal and Negative Refraction
Science, published online August 28, 2008

Researcher's homepage:
John Pendry

Related stories and briefs:
Negative refraction gets visible -- recent developments in negative fraction
Scheme reverses light pulses -- previous work on time reversal of light

Further info:
View from the High Ground: ICL's John Pendry -- an interview with the inventor of negative index of refraction materials

Back to TRN September 15/22, 2008

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