http://www.forbes.com/sites/alexknapp/2011/07/18/physicists-create-a-hole-in-time-to-hide-events/
Researchers at Cornell University have made an astounding leap forward in cloaking technology. While other teams have been working on what have been traditionally seen as “invisibility cloaks” – using meta-materials to hide an object from visible light — this team has been working on something a bit more ambitious: hiding an actual event in time.
Current work in developing invisibility cloaks tries to hide an object spatially. Like a magician using a complex set of mirrors to hide his tricks, a invisibility cloak uses materials that change the shape of light so that it moves around an object, hiding it from view. What the researchers at Cornell are doing is similar: they’re taking advantage of the fact that, according to current theories in physics, time and space are equivalent – and instead of focusing on changing the shape of light, they’re focused on changing its time.
The researchers began their experiment by creating two time lenses. Unlike a normal lens, which compresses or changes the actual shape of a light wave through diffraction, a time lens magnifies or compresses the time of a light wave through dispersion.
The time lenses that were created for this experiment were split time lenses. Essentially, two halves of a lens were placed so that the points met in the middle. There was one split time lens on one side of the cloaked event and another split time lens on the other side. A laser was then passed through the first time lens. This dispersed the light around the events happening between the lenses. The light then passed through the second split time lens and returned to its original phase. So to an observer, it’s as though the events between the lenses never happened. (See the figure above for a visual about how this works.)Now, this “hole in time” was only created for the briefest of instants – about 110 nanoseconds. And the research indicates that the maximum amount of time an event could be hidden is also small – perhaps no longer than 120 microseconds. Still, this is a pretty fascinating breakthrough, and it’d be interesting to see if this could be combined with a spatial cloak in a practical way.
