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physicists have drawn up blueprints for a cloaking device that could, in theory, render objects invisible.
light normally bounces off an object's surface making it visible to the human eye. but john pendry and colleagues at imperial college london, uk, have calculated that materials engineered to have abnormal optical properties, known as metamaterials, could make light pass around an object as so it appears as if it were not there at all.
metamaterials are exotic composites made of electronic components such as wires and inductors that can be engineered to precisely control the way light travels through them.
pendry's team has drawn up plans for a spherical metamaterial structure that would render an enclosed object invisible. "the theory tells us the material properties we need at each point," says team member david smith, from duke university in north carolina, us. "the challenge is to match those theoretical requirements in the actual material, point-by-point."
bad visibility
other designs for invisibility cloaks have been drawn up in the past. one idea is to calculate exactly how an object scatters light and design a surrounding material to exactly cancel this out.
but such cloaking devices could not be used for more than one object. "using our method you can hide different objects under the same cloak, or move around within the cloak, and remain hidden," says pendry.
however, pendry's team’s design could currently only work at wavelengths larger than visible light. designing a cloaking device for visible wavelengths could be tricky as it would involve creating nanoscale metamaterials. "at these levels it is far more difficult to control the metal's properties," says smith. nonetheless, he believes that optical cloaking devices could be become a reality within the next decade.
fun idea
will stewart, an independent optics expert at the university of southampton, uk, is less convinced. he believes that it may prove too difficult to overcome these problems within such a timeframe. "it's great fun and a lovely idea, but i don't think it can literally be taken and applied to make an optical cloak," he says.
but stewart says the approach could work well with a narrow band of wavelengths and could, for example, shield an object from radar. pendry's team is, in fact, working on just such a device made from millimetre-sized metal units, which they hope to complete within a year.
"it looks like star trek was right," stewart says, referring to the invisibility shield famously used by klingon spaceships in the science fiction show.
journal reference: science (doi: 10.1126/science.1125907)
new scientist
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washington – troops conducting urban operations soon will have the capabilities of superheroes, being able to sense through 12 inches of concrete to determine if someone is inside a building.
the new "radar scope" will give warfighters searching a building the ability to tell within seconds if someone is in the next room, edward baranoski from the defense advanced research projects agency's special projects office, told the american forces press service.
by simply holding the portable, handheld device up to a wall, users will be able to detect movements as small as breathing, he said.
the radar scope, developed by darpa, is expected to be fielded to troops in iraq as soon as this spring, baranoski said. the device is likely to be fielded to the squad level, for use by troops going door to door in search of terrorists.
the radar scope will give warfighters the capability to sense through a foot of concrete and 50 feet beyond that into a room, baranoski explained.
it will bring to the fight what larger, commercially available motion detectors couldn't, he said. weighing just a pound and a half, the radar scope will be about the size of a telephone handset and cost just about $1,000, making it light enough for a soldier to carry and inexpensive enough to be fielded widely.
the radar scope will be waterproof and rugged, and will run on aa batteries, he said.
"it may not change how four-man stacks go into a room (during clearing operations)," baranoski said. "but as they go into a building, it can help them prioritize what rooms they go into. it will give them an extra degree of knowledge so they know if someone is inside."
even as the organization hurries to get the devices to combat forces, darpa already is laying groundwork for bigger plans that build on this technology.
proposals are expected this week for the new "visi building" technology that's more than a motion detector. it will actually "see" through multiple walls, penetrating entire buildings to show floor plans, locations of occupants and placement of materials such as weapons caches, baranoski said.
"it will give (troops) a lot of opportunity to stake out buildings and really see inside," he said. "it will go a long way in extending their surveillance capabilities."
the device is expected to take several years to develop. ultimately, servicemembers will be able to use it simply by driving or flying by the structure under surveillance, baranoski said.
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