Cloaking Technology May Protect From Natural Disasters
LiveScience Staff .. Date: 18 August 2009 Time: 05:20 AM ET .. [bit old but ..]
Like sound or light waves, tsunamis have a wavelength, crests and troughs that could be cancelled out to effectively cloak, say, an oil rig and protect it from the waves, based on new technology. But practically pulling such complex cloaking off will require a lot more research. .. CREDIT: Stockxpert
Cloaking, that perennial technology of comic books and sci-fi series, may be one step closer to reality.
Researchers have developed a new cloaking method that may someday prevent submarines and fighter jets from being detected by sonar and radar. It might also be used to shield buildings and oil rigs from the devastating effects of earthquakes and tsunamis.
As it is often depicted in sci-fi movies and books, cloaking involves making an object partly or completely invisible to incoming radiation such as light or radio waves.
And while there are already various cloaking methods available, this latest technology is the first to use antennas to generate waves instead of relying on exotic metals or “metamaterials” to protect objects from electromagnetic waves coming from sonar or radar. Metamaterial is created by combining two or more materials to extend the range of electromagnetic effects.
“It's a brand new method of cloaking," said Graeme Milton, lead author of the study and a professor at the University of Utah. "It is two-dimensional, but we believe it can be extended easily to three dimensions, meaning real objects could be cloaked.” .. http://www.livescience.com/4966-cloaking-device-concept-moves-theory.html
Compared to previous forms of cloaking that were only capable of hiding objects from very specific wavelengths of radiation, scientists say the new method can hide objects from a broader band of wavelengths, including sound waves, sea waves, and seismic waves.
"The problem with metamaterials is that their behavior depends strongly on the frequency you are trying to cloak from," Milton said. "So it is difficult to obtain broadband cloaking. Maybe you'd be invisible to red light, but people would see you in blue light."
Building bigger shields
Experiments conducted by the researchers showed it is possible to cloak something 10 times wider than the 4-inch microwaves that are emitted by radar, raising hopes for cloaking larger objects. So far, the largest object cloaked from microwaves was an inch-wide copper cylinder.
"We proved mathematically that this method works when the wavelength of incoming electromagnetic radiation is large compared with the objects being cloaked, meaning it can cloak very small objects," Milton says. "It also can cloak larger objects."
Milton says the cloaking devices cause "destructive interference," similar to when two pebbles are thrown in a pond and generate ripples of waves. In places where wave crests meet, the waves add up and the crests are taller. Where troughs meet, the troughs are deeper. But where crests cross troughs, the water is still because they cancel each other out.
The principle, applied to sound waves, is "sort of like noise cancelation devices you get with headphones in airplanes if you travel first class," Milton said.
The mathematical feasibility of the new cloaking technique is detailed in the journals Optics Express and Physical Review Letters. The research team designed a computer model to simulate how such a cloaking device would work.
"The research simulates on a computer what you should see in an experiment," Milton says. "We just do the math and hope other people do the experiments."
Blocking natural disasters
Results from the study demonstrate that it is conceivable to build cloaking devices that generate waves to create a quiet zone to protect oil rigs against incoming tsunami waves, or to create vibrations to neutralize incoming seismic waves from an earthquake.
"Our method may have application to water waves, sound and radar," Milton said. "It would be wonderful if you could cloak buildings against earthquakes. That's on the borderline of what's possible."
One disadvantage of the new method "is that it appears you must know in advance everything about the incoming wave," Milton said. That might require placement of numerous sensors to detect incoming seismic waves or tsunamis.
"The cloaking device would have to generate fields that have very small wavelengths," Milton said. "It is very difficult to build antennas the size of light waves. We're so far from cloaking real-sized objects to visible light that it's incredible."
Though cloaking from light "is probably impossible, it's a fascinating subject, and there is beautiful mathematics behind it," Milton said. "The whole area has exploded. So even if it's not going to result in a 'Harry Potter' cloak, it will have spinoffs in other directions," not only in protecting objects from waves of various sorts, but "for building new types of antennas, being able to see things on a molecular scale. It's sort of a renaissance in classical science, with new ideas popping up all the time."
Photo: Light-bending technology could be used to help make planes, tanks and soldiers effectively 'invisible' (Staff Sgt Andy M Kin, file photo: US Air Force) [ INSERT IMAGE ]
The United States Air Force is working with Victorian researchers to develop light-bending technology which could be used to camouflage military hardware in war zones.
The US military hopes the technology could allow armies to make troops, tanks, planes and ships effectively invisible on the battlefield.
The Victorian scientists are using modelling based on mother-of-pearl to work out how to control the direction of light.
The theory is that light could be bent around objects, making them disappear.
"By learning from nature, we're able to actually arrange very small particles - we call them nanoparticles - in a very precise way, in a 3D arrangement," Deakin University Associate Professor Tiffany Walsh said.
"This 3D arrangement can be very good at scattering light in particular wavelengths, in a very unusual way, in a very unexpected way."
The breakthrough uses computer modelling at the Victorian Life Sciences Computation Initiative.
Associate Professor Marc R Knecht, from the University of Miami, says the work is being used by the United States Air Force.
"They're going to be using a lot of these waveguides for camouflage so that they aren't visible to the enemy on the battlefield," he said.
OOPS forgot EDITING "The US Air Force is quite ecstatic and really excited about this project."
But Associate Professor Walsh cannot say when the US will start using the ideas in warzones.
"These ideas, if they're promising, someone else in the Air Force will take them and develop them," she said.
"I don't know what that timescale is, or who's in charge of that," she said.
She says the technology could have a wide range of practical applications, such as replacing wires in circuitry with lights, which would be a more efficient way to power computers.
Invisibility Breakthrough for Japanese Researchers
NTDTV - Uploaded on Jul 25, 2009
Researchers in Japan have invented an incredible invisibility cloak.
The technology comes from 2003, but it's developers say the Harry Potter-like invisibility cloak is just the beginning. The team, led by Dr. Susumu Tachi, from Keio University, is now adapting their findings to help pilots, drivers, doctors and others.
Retro-reflective projection technology uses a computer, a video camera and projector to shine background images onto the front of a subject wearing specialised clothing, creating the illusion of invisibility.
What makes the technology unique is a fabric made of glass beads only 50 microns wide, which can reflect light directly back at the source, much like the screen in a cinema.
Viewed from near the light source, the projection is bright even in broad daylight, and researchers say the material can be applied to almost anything. In the short term, the team sees usage in car interiors, airplanes and helicopters.
They say blind spots could be eliminated and accidents and hard landings avoided by making walls seemingly transparent.
The eventual goal though is to create an "augmented reality" that allows anyone to easily see information on real world objects.
[Dr. Susumu Tachi, Keio University]: "Looking to the future, instead of glasses, people could wear this and it would act as a navigation system. It could also tell you who someone is, if you meet them around town." In the few years since the technology's invention, the price of the material, as well as that of computing, has come down, opening the door for smaller yet more powerful applications.
Whether used to increase safety or to create a whole new form of computer-human interaction, the world is likely to see, or possibly not see, more of this technology in the future.
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