Friday, July 22, 2011 1:09:33 AM
How To Make Time Invisible
By Hank Campbell | July 16th 2011 12:14 PM
Researchers from Cornell say that by using a bit of electromagnetics wizardry they can create a 'hole' in space and keep it hidden - spatial cloaking. Invisible time.
We see things using light, of course, namely as light scatters on an object. Using materials with a negative index of refraction, experiments have been able to create an 'invisibility cloak' for objects, which is certainly exciting. The downside is they are not in the visible range so Romulans are not going to be invading Earth any time soon.
We've also written about an invisibility cloak for time before but that was a mathematical extension of a physical process - because light normally slows down as it enters a material it is theoretical to locally manipulate the speed of light so that some parts speed up and others slow down so rather than being curved in space, the leading half of the light speeds up and arrives before an event, while the trailing half is made to lag behind and arrives too late. The result is that for a brief period the event is not illuminated and escapes detection.
The researchers pre-publishing this week have manipulated light in a fiber-optic cable using that theoretical process. Some of the light passing through a split-time lens speeds up and some slows down and when the waves come back together it arrives at its destination with no record of that 'gap' in time. The event is invisible in time.
Their invisibility cloak for time lasted for 15 trillionths of a second, which was enough time for them to register that their pulse of light were cloaked in the time domain.
Schematics of the temporal cloak using a pair of split time-lenses (STL). The STL's are used to create a temporal 'hole' in a probe beam such that any temporal or spectral changes caused by an event within this hole do not occur. The figure is oriented such that the probe light is described by horizontal lines, and lines at different orientations represent different wavelengths. D denotes the magnitude of the total negative or positive group-velocity dispersion.
It isn't perfect, thanks to third-order dispersion, so longer periods of time (by simply using a longer cable) will not work until the kinks are worked out. The single-mode fiber has a length of, at most, 50 Km before scattering is too much - which means a temporal gap of just over a microsecond.
Citation: Moti Fridman, Alessandro Farsi, Yoshitomo Okawachi, Alexander L. Gaeta, 'Demonstration of temporal cloaking', arXiv:1107.2062v1
*
More on invisibility:
Meta-Flex: Your Future Invisibility Cloak?
Like Your New Invisibility Cloak? The Chinese Have Already Cracked It
Plasmonics Advance Yields 2-D 'Invisibility' Cloak
Invisibility Cloak Gets A Nanomaterial Boost
Mathematics Of Cloaking: New Analysis Improves Methods To Render Objects Invisible
Invisibility Advance - 3D Cloaking Metamaterial In Optical Range Created
Research into Metamaterials May Pave the Road to Invisibility
First Tunable Electromagnetic 'Gateway' Acts Like A 'Hidden Portal'
*
Related Articles on Science 2.0
Meta-Flex: Your Future Invisibility Cloak?
Giant Invisible Space Ribbon
A cloak in time
An Invisibility Cloak For Time Also?
Like Your New Invisibility Cloak? The Chinese Have Already Cracked It
*
© 2011 ION Publications LLC (emphasis in original)
http://www.science20.com/science_20/blog/how_make_time_invisible-80903 [with embedded links, and comments]
===
Physicists Create a Hole In Time to Hide Events
Alex Knapp
Jul. 18 2011 - 1:05 am
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.
Copyright 2011 Forbes.com LLC™
http://blogs.forbes.com/alexknapp/2011/07/18/physicists-create-a-hole-in-time-to-hide-events/ [with embedded links, and comments]
===
Invisibility cloak hides objects in a gap in time
Researchers come up with invisibility cloak that's more Dr. Who than Harry Potter
By Kevin Fogarty
July 18, 2011, 9:12 AM —
Just in time for the film finale of Harry Potter, whose best deus ex machina was a cloak that made him invisible, researchers at Cornell invented one that combines invisibility and time travel.
Well, not time travel – as in travelling through time into the past. The device actually creates a spot between two time lenses in which anything that happens is undetectable because the light that should be hitting it has taken a detour, through time, around it.
That's not the kind of time travel that will get you to the court at Camelot in time to become revered for predicting an eclipse, but it's not too shabby.
It's a much more elegant approach than the earliest "cloaks" that provided camouflage, not invisibility, by projecting on one side of the cloak the image of what was on the other side. To make a truck invisible, tiny cameras on one side take in the image of a truckless landscape and send the image to the other side, which displays it as a high-def movie of a truck not being in that spot.
A 2008 paper theorized the ability to do something similar without the cameras and movie screen by using materials that erase the effect on light of passing through a space or bouncing off an object.
Metaphorically that would mean catching the light, erasing the image and then sending it on its way without delaying it. Like live-action Photoshop at relativistic speeds.
More recently physicists specializing in the behavior of light have designed "metamaterials" that bend light around an object so it appears not to be there (no light bouncing off it means you can't see it, but you'd think there would be a dark spot where the invisible you was supposed to be).
Metamaterials are fabrics, metals or other materials designed (usually with something clever operating on a nano scale) to have properties normal materials don't. Like being able to bend light around themselves.
The problem with that approach, other than the tendency to be stolen by English boarding-school children with a penchant for trouble, is that they're difficult and expensive to build.
The metamaterials used have a lattice structure – like woven cloth – with gaps between the strands of material that are smaller than the wavelength of the light you're trying to bend.
That's ridiculously small, but not enough to give the material the ability to bend light in a controlled way.
That, in one experiment, required 10,000 gold resonators that were attached to a piece of silk one centimeter square.
Try doing that on the kitchen table with a pair of tweezers and some Elmer's.
At Cornell the approach relied relied only on beams of light and the odd common behavior of light being refracted – bent as it passes through a medium like water, which is why a fish you see from the surface is never quite where it looks like it is if you try to poke it with a stick.
Light refracts not only in space, but in time as well, because the two are part of the same uber-thing according to Dr. Einstein.
Send a focused beam of light through a lens that modulates it optically (using the material in the lens) and with electromagnets and you can take a beam of light moving in a straight line, cause it to bend around an object, and return to its straight line as if nothing ever happened.
Except it doesn't bend just in space, as is would if it hit an angled mirror; it bends in time, then returns to its original course without having to bounce off anything first.
Bend light around all sides of an object and you create a spherical space that still exists in normal space and time, but you can't see it because all the light that should be hitting it is taking a detour though a part of the physical dimensions we normally can control only to the point that we can alter whether we're late to a meeting or not.
Researchers at Imperial College in London published a paper in February describing a similar experiment in invisibility using "A Spacetime Cloak, or a History Editor," the result is not only repeatable, it also has a brand name.
You'll probably be able to pick one up at your local Big Box store in a year or two, along with technology able to accomplish all the other magical things in Harry Potter, Lord of the Rings and all the other fantasy novels that apparently created a yen for magical powers in the kid brains of what are now top physicists.
I'm sure they'll keep on in that path until, in a decade air traffic will be complicated by dragon flights but you'll never miss an appointment because the airline will have a time portal for you to jog through on your way down to baggage claim (you'll have had to check the battle axes and armor; sorry, no one has invented a way to make the TSA invisible or unnecessary).
© 2011 ITworld
http://www.itworld.com/science/184133/invisibility-cloak-hides-objects-gap-time [with embedded lihks; no comments yet]
===
(linked in) http://investorshub.advfn.com/boards/read_msg.aspx?message_id=50277081 and preceding (and any future following)
By Hank Campbell | July 16th 2011 12:14 PM
Researchers from Cornell say that by using a bit of electromagnetics wizardry they can create a 'hole' in space and keep it hidden - spatial cloaking. Invisible time.
We see things using light, of course, namely as light scatters on an object. Using materials with a negative index of refraction, experiments have been able to create an 'invisibility cloak' for objects, which is certainly exciting. The downside is they are not in the visible range so Romulans are not going to be invading Earth any time soon.
We've also written about an invisibility cloak for time before but that was a mathematical extension of a physical process - because light normally slows down as it enters a material it is theoretical to locally manipulate the speed of light so that some parts speed up and others slow down so rather than being curved in space, the leading half of the light speeds up and arrives before an event, while the trailing half is made to lag behind and arrives too late. The result is that for a brief period the event is not illuminated and escapes detection.
The researchers pre-publishing this week have manipulated light in a fiber-optic cable using that theoretical process. Some of the light passing through a split-time lens speeds up and some slows down and when the waves come back together it arrives at its destination with no record of that 'gap' in time. The event is invisible in time.
Their invisibility cloak for time lasted for 15 trillionths of a second, which was enough time for them to register that their pulse of light were cloaked in the time domain.
Schematics of the temporal cloak using a pair of split time-lenses (STL). The STL's are used to create a temporal 'hole' in a probe beam such that any temporal or spectral changes caused by an event within this hole do not occur. The figure is oriented such that the probe light is described by horizontal lines, and lines at different orientations represent different wavelengths. D denotes the magnitude of the total negative or positive group-velocity dispersion.
It isn't perfect, thanks to third-order dispersion, so longer periods of time (by simply using a longer cable) will not work until the kinks are worked out. The single-mode fiber has a length of, at most, 50 Km before scattering is too much - which means a temporal gap of just over a microsecond.
Citation: Moti Fridman, Alessandro Farsi, Yoshitomo Okawachi, Alexander L. Gaeta, 'Demonstration of temporal cloaking', arXiv:1107.2062v1
*
More on invisibility:
Meta-Flex: Your Future Invisibility Cloak?
Like Your New Invisibility Cloak? The Chinese Have Already Cracked It
Plasmonics Advance Yields 2-D 'Invisibility' Cloak
Invisibility Cloak Gets A Nanomaterial Boost
Mathematics Of Cloaking: New Analysis Improves Methods To Render Objects Invisible
Invisibility Advance - 3D Cloaking Metamaterial In Optical Range Created
Research into Metamaterials May Pave the Road to Invisibility
First Tunable Electromagnetic 'Gateway' Acts Like A 'Hidden Portal'
*
Related Articles on Science 2.0
Meta-Flex: Your Future Invisibility Cloak?
Giant Invisible Space Ribbon
A cloak in time
An Invisibility Cloak For Time Also?
Like Your New Invisibility Cloak? The Chinese Have Already Cracked It
*
© 2011 ION Publications LLC (emphasis in original)
http://www.science20.com/science_20/blog/how_make_time_invisible-80903 [with embedded links, and comments]
===
Physicists Create a Hole In Time to Hide Events
Alex Knapp
Jul. 18 2011 - 1:05 am
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.
Copyright 2011 Forbes.com LLC™
http://blogs.forbes.com/alexknapp/2011/07/18/physicists-create-a-hole-in-time-to-hide-events/ [with embedded links, and comments]
===
Invisibility cloak hides objects in a gap in time
Researchers come up with invisibility cloak that's more Dr. Who than Harry Potter
By Kevin Fogarty
July 18, 2011, 9:12 AM —
Just in time for the film finale of Harry Potter, whose best deus ex machina was a cloak that made him invisible, researchers at Cornell invented one that combines invisibility and time travel.
Well, not time travel – as in travelling through time into the past. The device actually creates a spot between two time lenses in which anything that happens is undetectable because the light that should be hitting it has taken a detour, through time, around it.
That's not the kind of time travel that will get you to the court at Camelot in time to become revered for predicting an eclipse, but it's not too shabby.
It's a much more elegant approach than the earliest "cloaks" that provided camouflage, not invisibility, by projecting on one side of the cloak the image of what was on the other side. To make a truck invisible, tiny cameras on one side take in the image of a truckless landscape and send the image to the other side, which displays it as a high-def movie of a truck not being in that spot.
A 2008 paper theorized the ability to do something similar without the cameras and movie screen by using materials that erase the effect on light of passing through a space or bouncing off an object.
Metaphorically that would mean catching the light, erasing the image and then sending it on its way without delaying it. Like live-action Photoshop at relativistic speeds.
More recently physicists specializing in the behavior of light have designed "metamaterials" that bend light around an object so it appears not to be there (no light bouncing off it means you can't see it, but you'd think there would be a dark spot where the invisible you was supposed to be).
Metamaterials are fabrics, metals or other materials designed (usually with something clever operating on a nano scale) to have properties normal materials don't. Like being able to bend light around themselves.
The problem with that approach, other than the tendency to be stolen by English boarding-school children with a penchant for trouble, is that they're difficult and expensive to build.
The metamaterials used have a lattice structure – like woven cloth – with gaps between the strands of material that are smaller than the wavelength of the light you're trying to bend.
That's ridiculously small, but not enough to give the material the ability to bend light in a controlled way.
That, in one experiment, required 10,000 gold resonators that were attached to a piece of silk one centimeter square.
Try doing that on the kitchen table with a pair of tweezers and some Elmer's.
At Cornell the approach relied relied only on beams of light and the odd common behavior of light being refracted – bent as it passes through a medium like water, which is why a fish you see from the surface is never quite where it looks like it is if you try to poke it with a stick.
Light refracts not only in space, but in time as well, because the two are part of the same uber-thing according to Dr. Einstein.
Send a focused beam of light through a lens that modulates it optically (using the material in the lens) and with electromagnets and you can take a beam of light moving in a straight line, cause it to bend around an object, and return to its straight line as if nothing ever happened.
Except it doesn't bend just in space, as is would if it hit an angled mirror; it bends in time, then returns to its original course without having to bounce off anything first.
Bend light around all sides of an object and you create a spherical space that still exists in normal space and time, but you can't see it because all the light that should be hitting it is taking a detour though a part of the physical dimensions we normally can control only to the point that we can alter whether we're late to a meeting or not.
Researchers at Imperial College in London published a paper in February describing a similar experiment in invisibility using "A Spacetime Cloak, or a History Editor," the result is not only repeatable, it also has a brand name.
You'll probably be able to pick one up at your local Big Box store in a year or two, along with technology able to accomplish all the other magical things in Harry Potter, Lord of the Rings and all the other fantasy novels that apparently created a yen for magical powers in the kid brains of what are now top physicists.
I'm sure they'll keep on in that path until, in a decade air traffic will be complicated by dragon flights but you'll never miss an appointment because the airline will have a time portal for you to jog through on your way down to baggage claim (you'll have had to check the battle axes and armor; sorry, no one has invented a way to make the TSA invisible or unnecessary).
© 2011 ITworld
http://www.itworld.com/science/184133/invisibility-cloak-hides-objects-gap-time [with embedded lihks; no comments yet]
===
(linked in) http://investorshub.advfn.com/boards/read_msg.aspx?message_id=50277081 and preceding (and any future following)
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"Eternal vigilance is the price of Liberty."
from John Philpot Curran, Speech
upon the Right of Election, 1790
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