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Scientists Make Item Invisible to Microwaves
Vicissidude writes "A team of American and British researchers has made a cloak of invisibility. In their experiment the scientists used microwaves to try and detect a copper cylinder. Like light and radar waves, microwaves bounce off objects making them visible and creating a shadow, though it has to be detected with instruments. If you can hide something from microwaves, you can hide it from radar and visible light. In effect the device, made of metamaterials — engineered mixtures of metal and circuit board materials, which could include ceramic, Teflon or fiber composite materials — channels the microwaves around the object being hidden. When water flows around a rock, co-author David R. Smith explained, the water recombines after it passes the rock and people looking at the water downstream would never know it had passed a rock. The first working cloak was in only two dimensions and did cast a small shadow, Smith acknowledged. The next step is to go for three dimensions and to eliminate any shadow."
...that would love to be invisible to microwaves.
They could've posted a pict...
Oh, wait. Never mind!
If we can hit that bull's-eye, the rest of the dominoes will fall like a house of cards... Checkmate.
someone using the term "kewl" is complaining about buzzwords?
*Ring* Hello?
Hi, this is the Pot calling. Is the Kettle in?
I don't think this follows, at least when we're talking about metamaterials. So far no one has invented metamaterials for optical wavelengths, as metamaterials rely on complex structure that's somewhat wavelength specific. It's easier to play "fool the photon" with microwaves (because of the longer wavelength) or X-rays (because of the higher energy) than it is with visible light. (Xiang Zhang's experiments in extending near-field effects of visible light are a very different mechanism, and are lumpedin with metamaterials simply for lack of a better term.)
Socialism: a lie told by totalitarians and believed by fools.
Negative Index of refraction Materials (NIMs), metamaterials, or whatever you want to call them, are relatively easy to make in the microwave region, since the wavelengths are on the order of centimeters. Thus, using a special arrangement of rings, loops, and wires, you can craft a lattice-like material that exhibits negative refraction. Technically, it has a negative magnetic permeability (mu) and negative permittivity (epsilon).
This has all kinds of weird implications. The group velocity is still in the forward direction, but the phase velocity goes in reverse. Evanescent waves propogate, not die off. Perfect lenses can be made. Measurements LESS than the wavelength of light can be taken. There was a list of implications in the August issue of Scientific American, I believe.
Anyhow, this works great at the ~cm scale. Visible light is hard as hell: the scale there is on the order of nanometers. And the copper or silver or tungsten wires used to make the metamaterials have MISERABLE magnetic losses at these small scales, so mu is no longer negative. The energy no longer propagates in the medium. As of three years ago, there were no promising candidates for solving this problem. There was an outside hack at using carbon nanotubes -- which may or may not maintain their permeability down to small scales -- but it was a long shot at best. Arranging the little guys would have been devilishly difficult.
Glad to see that Pendry, who's been in this field almost as long as Veselago, is still making good strides. Even if they can't get to the visible wavelength, NIM's have spectacular applications for microwave antennae.
"Diplomacy is something you do until you find a rock." --Richard Pound
If it's diverting all the light around you, there's no light to get in and hit your eye so you can see.
The solution would be much more complex than the basic cloak. You'd have to let some light in, but make sure it didn't get back out again. I can see that being problimatic.
If forums teach us anything, it is that logic and critical thinking should be required courses in the public schools.
You obviously didn't either. Somebody bring me the learnin' stick. You're both technically right. The Romulan Bird-of-Prey (from TOS, small white-ish ship with the bird painted on the bottom) did have a cloaking device, as did the Klingon (and Romulan) D-7 Battlecruiser. In the TNG era the Romulan Warbird (big and green) and the contemporary Klingon ships (Bird-of-Prey and Vor'Cha). Now, go play. I have a phaser to polish.
A casual stroll through the lunatic asylum shows that faith does not prove anything. - Neitzsche
The real issue, and the major downside to a cloak of this nature, is how do you see where you're going while you are wearing it?
Use your feelings, you must