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Science/Tech See other Science/Tech Articles Title: Physicists have created a "hole in time" using the temporal equivalent of an invisibility cloak. 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. Time cloaking is possible because of a kind of duality between space and time in electromagnetic theory. In particular, the diffraction of a beam of light in space is mathematically equivalent to the temporal propagation of light through a dispersive medium. In other words, diffraction and dispersion are symmetric in spacetime. That immediately leads to an interesting idea. Just as its easy to make a lens that focuses light in space using diffraction, so it is possible to use dispersion to make a lens that focuses in time. Such a time-lens can be made using an electro-optic modulator, for example, and has a variety of familiar properties. "This time-lens can, for example, magnify or compress in time," say Fridman and co. This magnifying and compressing in time is important. 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. In effect, the space between the two lenses is a kind of spatio-temporal cloak that deletes changes that occur in short periods of time. 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. But it's early days yet. Given the rapid development of spatial cloaks, it'd be a brave man who'd bet on this being the last word. Fridman and pals have clearly made themselves an interesting toy but they modestly refrain from speculating about the applications for their time cloak. However, that's a task well suited to readers of the Physics arXiv Blog. If you have any suggestions, leave them here. From among 35 comments: doanwon I think this works in masking the visual sense when the observer is suddenly seeing something that is occurring because the light--which is the event--has not been released by the cloak. The light has been trapped for a brief period of time. It's like a delay but in the visual sense. So you can't really be out of the time dimension. You can only fool the visual observer. Stock transactions are rigged already. The high levels get near immediate electronic event reporting while those day traders and lower in the food chain get delayed transactions. JohnStClair Use Slow Light to Cloak Between the lenses you can insert a magnetic vortex wormhole generator to bring in low-speed-of-light hyperspace energy that has a light speed of 1 meter/second. The generator creates negative energy to open up a wormhole between space and hyperspace. Because negative energy has a lower potential than low-density positive hyperspace energy, the hyperspace energy will flow into this dimension between the lenses. It is like putting a vacuum pump on the end of a garden hose. This will increase the available cloaking time. Furthermore, the hyperspace energy can be curved using electromagnetic fields since they are subject to the Lorentz transformation. Thus the light can be curved around the object to be cloaked. This concept is what Einstein, the discoverer of hyperspace, was trying to do in the Philadelphia Experiment that was covered up by the US Navy. The Navy wanted a way to bend light around the Liberty ships so that the German U-boats would see a false image. It resulted in the discovery of teleportation which has now been accomplished. If I were going to cloak something, I would create a wormhole opening in front and back of the object and light will travel around the object through the throat of the wormhole. This is the same as the wormhole elevator that we have between earth and Mars. As the elevator ascends, it becomes wavy space-time because the spring constant of space has been decreased substantially due to the spring's dependence on the speed of light squared and the linear mass of the universe. spookysr Time Lens? WTF is a time lens? More smoke & mirrors from private sector? Give me a break. Classified projects already out of the R&D lab of UC Berkeley using optical (or photonic) metamaterials are already being field tested in SW Asia with US Army tank officers. It causes light to refract around an object in ALL directions rendering the object partially "cloaked" (you still can see scintillation-effect). It uses nano-technology mirrors embedded into a jump suit and can be turned off and on at will. The Brits are toying with one that can cloak an entire army tank, and it works. What this thing is in this article is just something specious at best. What they seem to be talking about is slowing down a laser or some sort of coherent light which is already being done successfully at UCONN in Connecticut (USA). But its the only source of light. What about ambient light from other sources? That ambient light would UN-cloak you I'd think. There are MANY US Patents on file for cloaking devices. The Japanese have a really nifty one. We have been doing a sort of cloaking since WW2 with Yehudi Lights. Now we are using active camouflage on jet fighter planes since Clinton administration (i.e. Boeing Bird of Prey). They disappear right before your eyes (blend in with sky). pkk some references Original proposal for spacetime cloaking is at at Journal of Optics: iopscience.iop.org/2040-8986/13/2/024003 Recent popular article on spacetime cloaking: physicsworld.com/cws/article/indepth/46376 My comments: www.citeulike.org/blog/pak/16541 Post Comment Private Reply Ignore Thread Top • Page Up • Full Thread • Page Down • Bottom/Latest Begin Trace Mode for Comment # 1.
#1. To: Tatarewicz (#0)
Interesting! ;)
There are no replies to Comment # 1. End Trace Mode for Comment # 1.
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