Fatal Flaw Discovered In Invisibility Cloaks

KentuckyFC writes "Carpet cloaks took the world by storm last year because they were the first devices to hide objects at optical frequencies. The idea is that a thin layer of dielectric material placed on a surface can make light look as if it is reflecting off the original surface. In other words, the layer is invisible and anything embedded within it is invisible too. This trick is like hiding something under a carpet, hence the name. Carpet cloaks are relatively easy to make because the dielectric material does not need to be specially constructed to steer light in special ways; physicists call this an isotropic material. Now a group at MIT has shown that isotropic carpet cloaks have a fatal flaw. When viewed at an angle, the carpets don't hide objects at all. Instead, they simply shift their position by about the same distance as they are high. So when viewed from an angle of 45 degrees, an object 0.2 units high is shifted to one side by a distance of 0.15 units, says the team. That's a serious limitation for carpet cloaks."

Comments

Wrong Cloak

[LaminatorX]

So what they're saying is it's more of a Cloak of Displacement? While less stealthy, I think that's actually better odds of avoiding the hit than the penalty for attacking an invisible opponent.

I guess?

[Monkeedude1212]

Yeah - you aren't invisible, but wouldn't that still make the tracking missile miss you?

Soo....

[Some.Net(Guy)]

When they were creating these cloaks, they didn't think to look at it from other angles than just straight on? Seriously? That's the equivalent of "it works on my machine."

Re:Soo....

[e2d2]

They're making things invisible. It's kind of hard. So cut them a break? It's not like it's been done before and they just half-assed it after all.

Re:All over the world

[TheMeuge]

From TFA:

Zhang and co go on to prove their assertion by tracing a ray that passes through the kind of isotropic carpet cloak that Pendry suggested. What they've discovered will shock carpet cloakers all over the world.

Yeah, all over the world.... uhm, all three of them. (Emphasis mine)

The three that YOU CAN SEE...

Re:bummer

[maxwell demon]

They did. Then they switched it on, and ever since they are seeking the device.

0.2 units high by 0.15 units?

[Posting=!Working]

I mean, I know we all understand it, but if you're giving an example, why use unitless decimals when you can use integers and tangible concepts? Why not just say it would displace a 4 meter tall truck by 3 meters instead of 0.2 units tall object by 0.15 units?

Re:The fatal flaw is:

[fractoid]

I can't see how they could work.

This is only about 'carpet cloaks', not invisibility cloaks in general. The problem is that a carpet cloak is the optical analogue of simply putting a display screen in front of the object and a video camera behind the object. In other words, of course it doesn't bloody work from the side, you morons. A general invisibility cloak is still possible, but may require phased array optics or other exotic active techniques.