[I]via:[/I] NatureNews
[release][B]Proposed device could edit actions out of history.[/B]
By: Zeeya Merali
It would be the perfect hiding place: a hole carved out of space–time. Optical physicists have created blueprints for a cloak that generates a pocket in reality in which actions can be concealed. In practice, the proposed design can be built only inside the special environment of an optical fibre. But even this constrained space–time cloak could have useful effects, such as assisting quantum computing.
The ideal space–time cloak — the theory behind which is published in the Journal of Optics today[URL="http://www.nature.com/news/2010/101116/full/news.2010.611.html?s=news_rss&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+news%2Frss%2Fmost_recent+%28NatureNews+-+Most+recent+articles%29#B1"]1[/URL] — would be an upgraded version of the 'invisibility cloak' that was first proposed in 2006[URL="http://www.nature.com/news/2010/101116/full/news.2010.611.html?s=news_rss&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+news%2Frss%2Fmost_recent+%28NatureNews+-+Most+recent+articles%29#B2"]2[/URL],[URL="http://www.nature.com/news/2010/101116/full/news.2010.611.html?s=news_rss&utm_source=feedburner&utm_medium=feed&utm_campaign=Feed%3A+news%2Frss%2Fmost_recent+%28NatureNews+-+Most+recent+articles%29#B3"]3[/URL] and has since been built for some wavelengths of light. Such standard invisibility cloaks are made from metamaterials — substances with a complex internal structure that allows them to channel light around objects like water flowing around a rock in a river. A distant observer perceives the light as if it has travelled in a straight line without ever hitting an intervening object.
"I realized that it may be possible to use metamaterials to bend light rays in both space and time, not just in space," says Martin McCall, an optical physicist at Imperial College London who led the team behind the new proposal. "This would add a new dimension to the invisibility cloak — literally."
[B]
Bypassing time[/B]
The key feature of the proposed space–time cloak is that its refractive index — the optical property that governs the speed of light within a material — is continually changed, pulling light rays apart in time. When the leading edge of a light wave hits the cloak, the material is manipulated to speed up the light, but when the trailing edge hits, the light is slowed down and delayed. "Between these two parts of the light, there will be a temporal void — a space in which there will be no illuminating light for a brief period of time," explains McCall.
Events and actions inside this void in space–time, after the leading edge of the light has passed through but before the trailing edge has arrived, would be shielded from the view of anyone outside. After the hidden action has been completed, the cloak would be turned off. The delayed trailing portion of light would then recombine with the leading edge, reconstructing a full light wave that would travel on; any observers would be unaware that it had been postponed.
"You could imagine a burglar using a space–time cloak to create an invisible corridor leading to a safe," says McCall. With the cloak turned on, the burglar could run through this corridor, open the safe, steal the contents, shut the safe and escape, while any security camera trained on the safe would just show a continuous image of a locked door at every point in time, explains McCall. "The dastardly event would have been edited from history," he says. By contrast, putting a conventional invisibility cloak over the safe would hide the object from observers — but a security camera would spot that the once-visible safe had been hidden.
Security guards do not need to worry, however. McCall and his colleagues have calculated the precise properties of the metamaterial needed to build a space–time cloak that would be perfectly invisible, and there are fundamental problems that prevent it from being constructed. The theoretical calculations work only in a vacuum, and to create a space–time void of even a few minutes would require a cloak bigger than Earth because of the space required to recombine the accelerated leading edge and slowed trailing edge of the light wave. Worst of all, the theory requires the metamaterial to boost light rays beyond the fundamental speed of light.
[B]
Fibre-optic void[/B]
Undeterred, the team has designed a less efficient version to be built from optical fibres — inside which light can be accelerated and slowed without breaking the fundamental speed limit. Lasers would be used to control the fibres' refractive indices, opening and closing the temporal void. The fibre-optic cloak could hide events only from observers standing directly ahead of the oncoming light waves, and it could not fully block all reflections from light travelling through the cloak while it is turned on, so some light might bleed out. A distant observer looking down the optical fibre would not spot the hidden event, but they would notice the background light getting brighter and dimmer.
McCall hopes that a fibre-optic cloak creating a space–time void around 30 centimetres long, to hide actions taking place over a few nanoseconds, could be built within the next year. It could be tested by firing a separate illuminating laser signal into the region of the void — the light should disappear when the cloak is turned on and reappear when it is switched off, he says.
However, Ulf Leonhardt, a physicist at the University of St Andrews, UK, who made one of the original proposals for an invisibility cloak, is sceptical that the design could be implemented with current technology, because of the difficulty involved in dramatically manipulating the refractive index of optical fibres to create a void for even a few nanoseconds. "It is, however, a very inspiring theoretical idea, so it could motivate others to come up with a more practical design," he says.
Ortwin Hess, a researcher into metamaterials at the University of Surrey in Guildford, UK, believes that the design might have practical applications for the developing field of quantum computing. Physicists are struggling to build quantum computers, because any accidental observation of fragile quantum properties can disrupt calculations before they have been completed. "This cloak could be used to shield quantum systems from being observed, long enough for calculations to be done," he says. [/release]
[URL="http://www.nature.com/news/2010/101116/full/news.2010.611.html"]Source[/URL]
Wikileaks will go out of business.
badass
Holy.
Fucking.
Shit.
someone explain quantum mechanics to me, I really want to know how something can go differently just because of observation
Oh man sounds interesting.
Holy shit these would be awesome for urban exploration.
"Oh shit its security! Quick, activate the Space-Time Cloaking Device!"
[quote]The ideal space–time cloak — the theory behind which is published in the Journal of Optics today1 — would be an upgraded version of the 'invisibility cloak' that was first proposed in [b]20062[/b][/quote]
Damn these things must work really well
suddenly the vietnam war never happened
-snip-
[QUOTE=Bletotum;26091332]someone explain quantum mechanics to me, I really want to know how something can go differently just because of observation[/QUOTE]
Okay sure I- wait- no- I'm afraid no one can do that son. All the theories are barely scratching the surface, your best bet would be google and wikipedia (checking sources.) Though, maybe, someone in here could put it in better words then those websites. The prospects of it are very mysterious and revolve around the behavior of electrons, and the sub-atomic particles that make up electrons. All very confusing if you don't have a really high level knowledge of physics and atomic chemistry.
Pfft no way we have the tech for that kind of stuff yet.
We haven't even got hover cars what chance do we have to make this shit.
[quote]"You could imagine a burglar using a space–time cloak to create an invisible corridor leading to a safe," says McCall. With the cloak turned on, the burglar could run through this corridor, open the safe, steal the contents, shut the safe and escape, while any security camera trained on the safe would just show a continuous image of a locked door at every point in time, explains McCall. "The dastardly event would have been edited from history," he says. [/quote]
:gonk:
[QUOTE=alienmartian23;26091502]suddenly the vietnam war never happened[/QUOTE] No it did happen and it will happen since we are in an alternate time line in which it did happen.
[QUOTE=Lust;26091134]Wikileaks will go out of business.[/QUOTE]
They have a profit motive?
what
[QUOTE=madmanmad;26091755]Pfft no way we have the tech for that kind of stuff yet.
We haven't even got hover cars what chance do we have to make this shit.[/QUOTE]
We have hover-cars, they're just not mass producted
Is anyone else reminded of the Room of Requirement?
[QUOTE=Bletotum;26091332]someone explain quantum mechanics to me, I really want to know how something can go differently just because of observation[/QUOTE]
Quantum mechanics in s nut shell:
We can't determine the exact position or velocity of very small objects that are moving really fast.
can someone tell me whats so special about the years 1939-1945? everybody keeps banging on about shit that happened back then but it makes no sense to me.....
We're pretty much punching holes in space-time?
Badass.
[quote=source;26093016]can someone tell me whats so special about the years 1939-1945? Everybody keeps banging on about shit that happened back then but it makes no sense to me.....[/quote]
World Wars Episode 2: Attack of the nazis.
This reminds me of so much Doctor Who related things.
[QUOTE=SPESSMEHREN;26091447]Holy shit these would be awesome for urban exploration.
"Oh shit its security! Quick, activate the Space-Time Cloaking Device!"[/QUOTE]
Ooops, it malfunctioned!
The warehouse and a large chunk of the ground it was attached to is now in Siberia
[QUOTE=ZekeTwo;26093300]Ooops, it malfunctioned!
The warehouse and a large chunk of the ground it was attached to is now in Siberia[/QUOTE]
During the Mesozoic Era.
When compared to Siberian raptor packs, a few rent-a-cops don't seem so bad, eh?
[QUOTE=Luxo;26092678]Quantum mechanics in s nut shell:
We can't determine the exact position or velocity of very small objects that are moving really fast.[/QUOTE]
Not quite. An increase in the certainty of a measurement of the position of a particle introduces uncertainty into any measurement of its momentum, and vice versa.
What Holocaust?
I figure honesty is the best policy here: I have no idea what the hell quantum mechanics actually is. This stuff is so far over my head that I couldn't reach it with three ladders and a step stool. However, I do think the phrase "Space-Time Cloak" is incredibly cool sounding, and will pretend that I'm knowledgeable on exactly what it is and does in social situations with people who I believe know even less on the subject than I do.
[quote]The theoretical calculations work only in a vacuum, and to create a space–time void of even a few minutes would require a cloak bigger than Earth because of the space required to recombine the accelerated leading edge and slowed trailing edge of the light wave. Worst of all, the theory requires the metamaterial to boost light rays beyond the fundamental speed of light. [/quote]
[i]So you can erase any part of history...[/i]
So long as you are capable of violating the laws of physics, the event is in space, and the event is not very long.
And its only useful if there would normally be people there to see it.
And they can still hear it.
And it doesn't affect time in any way.
why are we getting excited about this
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