http://news.yahoo.com/s/ap/20061019/ap_on_sc/cloak_of_invisibility

By RANDOLPH E. SCHMID, AP Science Writer
Thu Oct 19, 7:36 PM ET

WASHINGTON - Scientists are boldly going where only fiction has gone before — to develop a Cloak of Invisibility. It isn’t quite ready to hide a Romulan space ship from Capt. James T. Kirk or to disguise     Harry Potter, but it is a significant start and could show the way to more sophisticated designs.

In this first successful experiment, researchers from the United States and England were able to cloak a copper cylinder.

It’s like a mirage, where heat causes the bending of light rays and cloaks the road ahead behind an image of the sky.

“We have built an artificial mirage that can hide something from would-be observers in any direction,” said cloak designer David Schurig, a research associate in Duke University’s electrical and computer engineering department.

For their first attempt, the researchers designed a cloak that prevents microwaves from detecting objects. Like light and radar waves, microwaves usually bounce off objects, making them visible to instruments and creating a shadow that can be detected.

Cloaking used special materials to deflect radar or light or other waves around an object, like water flowing around a smooth rock in a stream. It differs from stealth technology, which does not make an aircraft invisible but reduces the cross-section available to radar, making it hard to track.

The new work points the way for an improved version that could hide people and objects from visible light.

Conceptually, the chance of adapting the concept to visible light is good, Schurig said in a telephone interview. But, he added, “From an engineering point of view it is very challenging.”

The cloaking of a cylinder from microwaves comes just five months after Schurig and colleagues published their theory that it should be possible. Their work is reported in a paper in Friday’s issue of the journal Science.

“We did this work very quickly ... and that led to a cloak that is not optimal,” said co-author David R. Smith, also of Duke. “We know how to make a much better one.”

The first working cloak was in only two dimensions and did cast a small shadow, Smith said. The next step is to go for three dimensions and to eliminate any shadow.

Viewers can see things because objects scatter the light that strikes them, reflecting some of it back to the eye.

“The cloak reduces both an object’s reflection and its shadow, either of which would enable its detection,” Smith said.

The cloak is made of metamaterials, which are mixtures of metal and circuit board materials such as ceramic, Teflon or fiber composite.

In an ideal situation, the cloak and the item it is hiding would be invisible. An observer would see whatever is beyond them, with no evidence the cloaked item exists.

“Since we do not have a perfect cloak at this point, there is some reflection and some shadow, meaning that the background would still be visible just darkened somewhat. ... We now just need to improve the performance of cloaking structures.”

In a very speculative application, he added, “one could imagine ‘cloaking’ acoustic waves, so as to shield a region from vibration or seismic activity.”

Natalia M. Litchinitser, a researcher at the University of Michigan department of electrical engineering and computer science who was not part of the research team, said the ideas raised by the work “represent a first step toward the development of functional materials for a wide spectrum of civil and military applications.”

Joining Schurig and Smith in the project were researchers at Imperial College in London and SensorMetrix, a materials and technology company in San Diego.

The research was supported by the Intelligence Community Postdoctoral Research Fellowship Program and the United Kingdom Engineering and Physical Sciences Research Council.

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Oh jeez…if Jason sees this, he’s gonna make us practice speaking Vulcan - he’ll be waiting for first contact.

dang. i can think of a lot of ...fun things to do when im invisible…

Sadly, very few of us see via microwaves, so I don’t see this being too useful just yet.  But as soon as they get it to work with visible light I’m sure burglary incidents will skyrocket.

From what I read, the thing is only a theoretical “blueprint” anyway.

If this were a hoax, though, I’m sure you could see right through it.

JoeDaJuggler - 20 October 2006 08:05 PM

From what I read, the thing is only a theoretical “blueprint” anyway.

D’oh!  Nevermind—I was looking at an old article on Duke’s site.

Can I apply to be the first one to try out the perfected model?

*imagines Thunder with a perfected invisibility cloak*

*goes to check the locks on his doors and the curtains on his windows*

I wonder how much power this sort of thing will need to operate, though?  I doubt that you’ll be able to just stick in a couple of AA batteries and go on your way with it.  If it needs to be plugged in to some high-power electical source, then it’s not going to be much use for wandering around with.

True, Acci, but remember, the first Univac computer filled a large room and had something like 2 KB of ram and took 12 people to run it.

But then again, what the hell does the size of computers have to do with the size of this light-bending device?

Remember the first ‘Predator’ movie?  With Governor Arnold?  I like the way they showed him, (the Predator) as some sort of almost-invisible creature, the image was clear, but kind of ‘jellied’ or something, a bit wavy looking.  I wonder if the ‘invisible’ objects would look like that?  It would sure be difficult to bend all those light waves then re-blend them perfectly in-sync. 

And if the object being rendered invisible cast any sort of shadow, that shadow would, of course, be visible, because it would not be in the direct line of sight, and also it would darken whatever it landed on, so while you may not see the intruder, you would certainly be able to see the intruder’s shadow.

Well, dang, dang!  There goes my idea to visit girl’s high-school locker rooms!

Dan, deeply disappointed

Dan Jr. - 21 October 2006 05:26 PM

Remember the first ‘Predator’ movie?  With Governor Arnold?  I like the way they showed him, (the Predator) as some sort of almost-invisible creature, the image was clear, but kind of ‘jellied’ or something, a bit wavy looking.  I wonder if the ‘invisible’ objects would look like that?  It would sure be difficult to bend all those light waves then re-blend them perfectly in-sync. 

And if the object being rendered invisible cast any sort of shadow, that shadow would, of course, be visible, because it would not be in the direct line of sight, and also it would darken whatever it landed on, so while you may not see the intruder, you would certainly be able to see the intruder’s shadow.

Well, dang, dang!  There goes my idea to visit girl’s high-school locker rooms!

Dan, deeply disappointed

There shouldn’t be any shadow, assuming the thing works right.  Shadows are caused by an object blocking light rays.

But this technology bends the light around the object, so it’s not blocking them.  If they can get the light to angle around properly, the light waves should simply “slide” around the object and continue on their previous path.

Of course, that depends on being able to get the light to go partway around the object and then continue on its original course.  Then you’d only be able to see what was behind the object, not the object itself, and you’d end up with it looking like this.  If it bounced off at some weird angle instead, you’d have the object cloaked but it wouldn’t fit in against its background; you might instead see what’s off to the side somewhere like this.  I’m not sure just how they’re getting it to head off at the proper angle to get the cloaking right.

Well, some magazine I just read had an article about this, so of course I am now an Absolute Authority and Expert on the subject. 

Regarding the shadow:

Okay, the ‘invisiblity’ comes from taking the light waves that emanate from the background behind the cloaked object, pulling them forward and around the object, then ‘bending’ them back to their original path, as if unblocked by the cloaked object.

But that object is still there, and is still blocking the sunlight (or whatver) that strikes it, thus creating a shadow on the opposite side of the light source.

Picture a human being (let’s make it be Hillary Duff) standing on the sidewalk in front of a Baskin-Robbins, trying to call me on her cell phone to find out what flavor ice cream cone to bring me.  The sun is off to her right, our left, as we face here.  There will be a shadow on the sidewalk next to her, on her left side, starting at her feet, and extending away.

Now, the cloaking device will bend the light rays of the Baskin-Robbins around her and reassemble them and let them now travel to our eyes, so we will see the store-front as though she wasn’t there.

But the sidewalk she is standing on is still darkened by her shadow, and will show to us.  Nothing can be done to prevent this, as the sunlight cannot pass through her, even if she is ‘cloaked’.  She is still a solid object.  A very beautiful solid object, I might add, but we already knew that.  So a shadow will still be present, it is unaffected by the light rays of the store-front being bent around her by the cloaking device.  They are two totally independent items.

I am glad we are getting to the bottom of this very important issue.

Dan, thinking very seriously about getting a real life

No, ideally the cloak would bend ALL light rays, not just the ones in a particular direction - the rays coming from the sun as well as rays reflecting off of objects around the person so cloaked.  There would be no shadow.

However, if the cloak was unidirectional then you are correct in assuming that a shadow would exist.  A unidirectional cloak would probably be far easier to develop and operate, but would still have applications (such as cloaking an air vehicle from ground fire).  The object would still be visible from the sides.  I expect this is the sort of thing that would turn up first. 

Also note that such a cloaking system could not be absolute or any person inside the cloak would be completely blind unless using other wavelengths to see by (ie - infrared or ultraviolet).  One would assume that a certain amount of light will be allowed through to provide for vision.  It needn’t be much, but would show up as a blank spot on the cloak that might be detectable, particularly if the wearer were moving against a varied background.