Nullary Sources

KentuckyFC of The Physics arXiv Blog posted this summary of some optics work out of Cornell University:

Invisibility cloaks are the result of physicists’ newfound ability to distort electromagnetic fields in extreme ways. The idea is steer light around a volume of space so that anything inside this region is essentially invisible.

The effect has generated huge interest. The first invisibility cloaks worked only at microwave frequencies but in only a few years, physicists have found ways to create cloaks that work for visible light, for sound and for ocean waves. They’ve even designed illusion cloaks that can make one object look like another.

Today, Moti Fridman and buddies, at Cornell University in Ithaca, go a step further. These guys have designed and built a cloak that hides events in time.

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The trick to building a temporal cloak is to place two time-lenses in series and then send a beam of light through them. The first compresses the light in time while the second decompresses it again.

But this leaves a gap. For short period, there is a kind of hole in time in which any event is unrecorded.

So to an observer, the light coming out of the second time-lens appears undistorted, as if no event has occurred.

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The device has some limitations. The Cornell time cloak lasts only for 110 nanoseconds—that’s not long. And Fridman and co say the best it can achieve will be 120 microseconds.

During the period the cloaking effect is active, the cloaked area will appear to outside observers as it did before the cloaking began. Any events that happen during that time will simply not be able to be observed. So, if you walk around while being cloaked, someone will not be able to see you moving; they’ll only see you as you were at the moment the cloaking began. When the cloaking is finished, you’ll appear to instantaneously teleport to your current position.

Fucking science.