Current News from The Looking Glass:

Thursday, January 5, 2012

Time Bandits!

First Demonstration of Time Cloaking

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.

Ref: Demonstration Of Temporal Cloaking

Tuesday, January 3, 2012

"This Moment to ARise" Redux

Dozens of dead blackbirds have fallen from the sky over a small Arkansas town for the second year in a row.

That the town of Beebe has seen this before, however, doesn't make the deaths of dozens of birds any less odd -- maybe even more so.

ABC Arkansas affiliate KATV reported that a radar image showed a large mass over Beebe a few hours before midnight Saturday. Then the birds began falling from the sky, just like last year.

Emily Nichols, a police dispatcher in Beebe, told ABC Radio that she received multiple calls. "Just that blackbirds are falling again and that they found black birds on their streets where they live or at churches," Nichols said.

Animal Care and Control was called out at about 7 p.m., a few hours earlier than last year, Horace Taylor of Animal Care and Control in Beebe told ABC Radio.

"Well, there was just birds falling down on the street and people dodging and missing them," Taylor said. "And we were down the street picking them up. We got called out by the chief and we all [came] out trying to pick them off the street."

Taylor added that the Game and Fish Department took about 30 of the nearly 100 birds for testing to try to determine what happened.

Fireworks were blamed for the deaths of thousands of blackbirds last year, but it's unclear whether fireworks were the cause this time. Police imposed an impromptu ban on fireworks when the birds began falling this year.

Lt. Brian Duke of the Beebe Police Department told ABC this year wasn't nearly as bad as last year, when the birds covered the streets of Beebe. This year, they were concentrated in a smaller area and the birds were cleaned up quickly. There haven't been any reports of people being hit by a falling bird.

Biologists said last year's kill was caused by birds who were spooked off their roosts by the loud explosions and began flying into homes, cars, telephone poles and each other.

Around this same time last year, thousands of dead fish also turned up in the Arkansas River, prompting conspiracies about the end of the world, poison and environmental catastrophe.

Taylor and Duke both agree, though: it's probably just the fireworks in Beebe.

ABC News Radio and the Associated Press contributed to this report.


The Red Queen?

[the Mad Hatter is brought into The Red Queen's court]
The Red Queen: Where is Alice?
The Mad Hatter: I've been considering words that start with the letter M. Moron. Mutiny. Murder. Mmm-malice.
The Red Queen: Well, we're looking for an A word right now. Where is Alice?