Invisibility Cloak

[Thornir Alekeg]

Talk of trying to develop an invisibility cloak.

 

[Umbran]

Of course, if that's the way it works, the person inside won't be able to see anything outside, either....

The news story is horribly vague, but if this is what I saw elsewhere as a reference to materials that have negative refractive index, the'd have another major drawback - they'd have be be very precisely shaped, and would only produce invisibility within a narrow frequency bandwidth.

 

[Hypersmurf]

Of course, if that's the way it works, the person inside won't be able to see anything outside, either....

Fibre-optic threads peeking out, and linked to the person's HUD sunglasses, maybe?

-Hyp.

 

[Thunderfoot]

I've seen a demo of this actually - don't pull out your checkbooks yet.

The "visual acuity problem" is not an issue for the wearer because there is a HUD system linked to fiber optic cameras (not sure if you were joking Hypersmurf, but you're spot on, at least that was the route they were going when I saw the test model).

The problem however, is as Umbran pointed out the limited bandwidth, the other problem is it is a PROJECTED IMAGE. Its great if you're standing still, try moving and there is an image flicker (more like a cloaking device from Star Trek than a cloak of invisibility) the civilian applications are also not an issue yet as this is being developed as a weapons program. (go figure). the other problem is one of heat exchange, the thing lights up like a Christmas tree under infra-red or night vision gear.

But they are least ten years away from any serious breakthroughs at this point. The technology just isn't there yet. (But, who knows)

 

[paradox42]

Actually I think this is different from what you're talking about Thunderfoot. There was a device demonstrated in Japan that consisted of a cloak of material that would take a projected image and display it, thus rendering the wearer apparently translucent (and in theory transparent/invisible if the technology improves further). That also drew comparisons to Harry Potter at the time, but it was done years ago.

This new thing talked about in the article (assuming negative refractive index is what they mean, like Umbran said) would require no projection- the materials themselves literally bend the light around the object, or more to the point through it. I don't really see a cloak in the clothing sense as being a likely possibility for the technology, but planes and ships that can disappear seem an obvious way to go. Precision shaping is very important to getting the "invisibility" effect right, and modern high-tech vehicles generally require precision shaping to properly build- seems like a definite possibility.

So less Harry Potter, more Wonder Woman, perhaps?

 

[Mycanid]

Here's another general link on the subject for everyone to peruse that just got sent to me from slashdot.org:

http://news.bbc.co.uk/1/hi/sci/tech/5016068.stm

 

[Umbran]

Precision shaping is very important to getting the "invisibility" effect right, and modern high-tech vehicles generally require precision shaping to properly build- seems like a definite possibility.

So less Harry Potter, more Wonder Woman, perhaps?

The problem is that the precision shape required to make a plane fly may have darned little to do with the precision shape needed to keep you invisible.

If it is the negative refractive index thing, there's another issue - It is basically a differnet sort of "lensing" effect, so the shape and relative positions of the object, lens, and observer will matter. Your eyeglasses or contact lenses assume a particular positionfor your eye. Try to look through the side, and they don't work as well. The same logic would apply here. Try to make a single lens that makes you invisible from all directions? Unless it just falls out that the proper shape is a sphere, it won't happen.

 

[paradox42]

The problem is that the precision shape required to make a plane fly may have darned little to do with the precision shape needed to keep you invisible.

If it is the negative refractive index thing, there's another issue - It is basically a differnet sort of "lensing" effect, so the shape and relative positions of the object, lens, and observer will matter. Your eyeglasses or contact lenses assume a particular positionfor your eye. Try to look through the side, and they don't work as well. The same logic would apply here. Try to make a single lens that makes you invisible from all directions? Unless it just falls out that the proper shape is a sphere, it won't happen.

Good point. But hen, if we can invent some kind of antigravity technology, then we could build invisible spherical UFOs and become like all those aliens in 1950s sci-fi shows!

 

[Thunderfoot]

Yep, looks like the precision shaping thing. Umbran is right, depending on where you stand you might see (for lack of a better phrase) a shadow(??) or blur that would give away your position, but in combat, the time it would take to actually pinpoint the source would be too long, you're toast as the "blur" fries you. So, in theory, its practicle, but I wouldn't invest yet.

Of course if someone is trying to figure out a way to build it, someone is already figuring out a way to defeat it. (Military axiom - Murphy's laws of combat material aquisitions #2)