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Curtains are falling on the final chapter of the Harry Potter movie franchise, so it's time to hang up your invisibility cloak in the hall closet. But don't look so glum, there's a new cloak for your spatio-temporal wardrobe -- one that's sure to turn a few heads in the physics department.
Moti Fridman and Alexander Gaeta, professors of applied and engineering physics at Cornell University, have developed a time cloak -- yes, a time cloak -- that, besides sounding like a Kurt Vonnegut trope, can also hide events in time.
Physicists have already found ways to make invisibility cloaks by distorting electromagnetic fields and steering light around a volume of space so that, essentially, anything inside this space is invisible.
Fridman and company were able to take that idea a step further and cloak time. In electromagnetic theory, the diffraction and dispersion of light are symmetric in spacetime.
They built a device that has two lenses called an electo-optic modulator. Next, they sent a beam of light through the lenses. The first lens compressed the light, while the second lens decompressed it, leaving a short gap or hole, in time where any event went unrecorded. To the naked eye, light coming out of the second time-lens appeared uninterrupted, as if no distortion had occurred.
In essence, between the two lenses exists a space-time void that cloaks any changes occurring in the short amount of time it takes the light to pass through both lenses.
The time cloak only lasts for 110 nanoseconds and Fridman says the best it can achieve in 120 microseconds. That may not sound like a long time, but I can't imagine the future appears anything but infinite to a couple of guys who just a built a time cloak.
Dhruv
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