作者：Seth Borenstein, AP Science Writer

编译：顾灵

来源：联合通讯（The Associated Press）版权2012/Artdaily

科学家称，一项新的隐形技术业已诞生，它不仅可以像《哈利·波特》中的隐形衣那样遮蔽一件实物，还能遮蔽一整个事件。这张时间遮罩其实是将整个时间周围的光速扭曲了。科内尔大学（Cornell University）的科学家们向联合通讯（The Associated Press）解释了这一2011年的研发项目可以如何使得艺术盗贼自由进出美术馆，躲过所有镭射警报系统、监控摄像头甚至你的双眼，满载而归。图片：AP Photo/Heather Deal, Cornell University.

华盛顿报道(AP).- 像哈利·波特的斗篷那样把一个实物隐形是一回事，把一整件事儿搞没了是另一回事。听着不可思议，但如今科学家们已经办到了，他们发明了一个时间遮罩。

试想，一个贼在你眼前和整个监控系统之下把一件名画轻轻松松搬走。你压根就没看见有这么个人走进博物馆，把画拿下然后离开，但他确实这么做了。不仅这个人是隐形的，整件事都是隐形的。

科内尔大学（Cornell University）的科学家们成功实现了一个小型试验，将时间和事件隐形。所以一切都发生于眨眼间：他们的时间斗篷在四十亿万分之一秒中生效，这一成果登载于上周四的《自然》（Nature）杂志。

我们看见事物的过程其实是事物折射的光抵达我们视网膜的过程。通常这束光是连续的。而在这项新发明中，科学家们成功将这一连续光束打断。

这一隐形斗篷的时间性则体现在将这束光从传统三维空间中抽离。科内尔团队这一次改变的并非光束的流动性，而是其运动速度；并非在空间中改变，而是在时间维度上。

他们对光束的速度做了手脚，改变原来让这束光得以被监控摄像头与镭射安保系统捕捉到的速度，从而让一起艺术盗窃案凭空消失。
科内尔大学物理分析师、该项目的合作者Moti Fridman解释说：可以这么理解，科学家们修改或擦除了历史中的一微妙，就像在一部影片中插入你都无法察觉到的一段碎片情节，但它确实存在于影片中，只不过你看不见。*

与此同时，科学家们不仅生造了一个镜头，还生造了一段时间…他们将光线分流，将光的一部分加速，另一部分减速，由此产生了一段时间缝隙，而被隐藏的事件恰藏于这段缝隙中。

科内尔大学物理设备与工程系主任、该项目合作者Alexander Gaeta 解释说：“就好像在时间中事件发生的那一刻挖了个洞，然后你就无法知道发生过的事。”

所以换句话说，光束被改装得过快以致人眼无法捕捉。利用比人类头发丝还细的光学纤维，这个时间空洞在光线穿过纤维时生成。艺术家们在这一刻透过洞把这束光抽走，然后抽走其他光束，并利用一个时间透镜将光分成不同速度运行的两束，从而让其因过快或过慢而隐形。Fridman 说，整个项目看起来就是堆在桌上的一大团面条（其实是光学纤维）。

这是科学史上头一回真在时间里玩把戏，把一个事件藏起来。整个项目的理论概念来自Martin McCall，他是伦敦帝国学院光学理论系的教授（theoretical optics at Imperial College in London），Gaeta、Fridman及科内尔大学的其他研究者共同研究时间透镜，尝试实现McCall的理论假想。

整个项目只耗费了几个月，对科学研究而言只不过是眨眼的功夫。
McCall 说：“这个项目非常重要，因为它解开了视觉感知的新疆界。”

杜克大学与德国Karlsruhe科学研究所的同仁们曾在空间实物隐形的研究上获得突破，早前成功研发出一件隐形斗篷，可以弯曲三维空间中实物周围的光线。

McCall预言：在光与时间之间，隐形的概念将会成为实用科技，但他并未参与任何一个研究小组的工作。

纽约城市大学（City College of New York）专攻虚拟科技物理学的物理学家Michio Kaku称这类研究确在正途，但毕竟还只是亿万分之一秒。

Kaku在一封邮件中写道：“若要用这点时间在霍格沃茨学院转悠一圈，肯定不够花。下一步是延长这一时间间隙，比如到百万分之一秒。所以在达到像科幻小说中描写的那种眼见为实的隐形还有很长的路要走。

Gaeta说接下来的实验就可以实现百万分之一秒甚至千万分之一秒。但McCall说，从数学计算上来看，所需耗费的纤维会太长——大约18,600 英里——来达到1整秒。

Gaeta回应道：“总得有个起点，这次的实验就是个明证。”
“当然，同类例子还有许多”，Gaeta和Fridman补充道，“比如在信息高速公路上加载一个隐形数据包，但这可以不干扰整个数据流的运行。不过当这个技术落入黑客手里，那就会变成病毒。”

Gaeta不无无奈地说：“我们当然希望科技造福人类，但出于某种原因，总有人想拿它来做坏事。”

*笔者碎碎念：还记得曾经一部新加坡连续剧《力克千年虫》，反派在影像中不断插入一些微秒画面，观众并未察觉，但这一微秒传达的信息却已深深植入观者潜意识，有如催眠。当然，这是心理学上的应用，题外话了。

Time cloak created: How an art thief can walk into a museum and steal a painting

scientists demonstrate how they have have created, a new invisibility technique that doesn’t just cloak an object _ like in Harry Potter books and movies _ but masks an entire event. It is a time masker that works by briefly bending the speed of light around an event. Cornell scientists explain what they are talking about in this 2011 illustration that shows that if this technique is ever scaled up an art thief can walk into a museum and steal a painting without setting of laser beam alarms or even showing up on surveillance cameras or your eyes. AP Photo/Heather Deal, Cornell University.

By: Seth Borenstein, AP Science Writer

WASHINGTON (AP).- It’s one thing to make an object invisible, like Harry Potter’s mythical cloak. But scientists have made an entire event impossible to see. They have invented a time masker.

Think of it as an art heist that takes place before your eyes and surveillance cameras. You don’t see the thief strolling into the museum, taking the painting down or walking away, but he did. It’s not just that the thief is invisible — his whole activity is.

What scientists at Cornell University did was on a much smaller scale, both in terms of events and time. It happened so quickly that it’s not even a blink of an eye. Their time cloak lasts an incredibly tiny fraction of a fraction of a second. They hid an event for 40 trillionths of a second, according to a study appearing in Thursday’s edition of the journal Nature.

We see events happening as light from them reaches our eyes. Usually it’s a continuous flow of light. In the new research, however, scientists were able to interrupt that flow for just an instant.

Other newly created invisibility cloaks fashioned by scientists move the light beams away in the traditional three dimensions. The Cornell team alters not where the light flows but how fast it moves, changing in the dimension of time, not space.

They tinkered with the speed of beams of light in a way that would make it appear to surveillance cameras or laser security beams that an event, such as an art heist, isn’t happening.

Another way to think of it is as if scientists edited or erased a split second of history. It’s as if you are watching a movie with a scene inserted that you don’t see or notice. It’s there in the movie, but it’s not something you saw, said study co-author Moti Fridman, a physics researcher at Cornell.

The scientists created a lens of not just light, but time. Their method splits light, speeding up one part of light and slowing down another. It creates a gap and that gap is where an event is masked.

“You kind of create a hole in time where an event takes place,” said study co-author Alexander Gaeta, director of Cornell’s School of Applied and Engineering Physics. “You just don’t know that anything ever happened.”

This is all happening in beams of light that move too fast for the human eye to see. Using fiber optics, the hole in time is created as light moves along inside a fiber much thinner than a human hair. The scientists shoot the beam of light out, and then with other beams, they create a time lens that splits the light into two different speed beams that create the effect of invisibility by being too fast or too slow. The whole work is a mess of fibers on a long table and almost looks like a pile of spaghetti, Fridman said.

It is the first time that scientists have been able to mask an event in time, a concept only first theorized by Martin McCall, a professor of theoretical optics at Imperial College in London. Gaeta, Fridman and others at Cornell, who had already been working on time lenses, decided to see if they could do what McCall envisioned.

It only took a few months, a blink of an eye in scientific research time.

“It is significant because it opens up a whole new realm to ideas involving invisibility,” McCall said.

Researchers at Duke University and in Germany’s Karlsruhe Institute of Technology have made progress on making an object appear invisible spatially. The earlier invisibility cloak work bent light around an object in three dimensions.

Between those two approaches, the idea of invisibility will work its way into useful technology, predicts McCall, who wasn’t part of either team.

The science is legitimate, but it’s still only a fraction of a second, added City College of New York physicist Michio Kaku, who specializes in the physics of science fiction.

“That’s not enough time to wander around Hogwarts,” Kaku wrote in an email. “The next step therefore will be to increase this time interval, perhaps to a millionth of a second. So we see that there’s a long way to go before we have true invisibility as seen in science fiction.”

Gaeta said he thinks he can get make the cloak last a millionth of a second or maybe even a thousandth of a second. But McCall said the mathematics dictate that it would take too big a machine — about 18,600 miles long — to make the cloak last a full second.

“You have to start somewhere and this is a proof of concept,” Gaeta said.

Still, there are practical applications, Gaeta and Fridman said. This is a way of adding a packet of information to high-speed data unseen without interrupting the flow of information. But that may not be a good thing if used for computer viruses, Fridman conceded.

There may be good uses of this technology, Gaeta said, but “for some reason people are more interested in the more illicit applications.”

Copyright 2012 The Associated Press.