Fatal Flaw Discovered In Invisibility Cloaks 255
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."
bummer (Score:2, Insightful)
Wrong Cloak (Score:5, Insightful)
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? (Score:4, Insightful)
Yeah - you aren't invisible, but wouldn't that still make the tracking missile miss you?
Well... (Score:1, Insightful)
The fatal flaw is: (Score:2, Insightful)
They DON'T WORK!
Soo.... (Score:4, Insightful)
Props to Soulskill (Score:3, Insightful)
Re:Soo.... (Score:5, Insightful)
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 (Score:4, Insightful)
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:Doctor Who knew all this stuff already... (Score:1, Insightful)
Unfortunately everyone has a mobile phone nowadays, so they -do- stand out (letterboxes too). But if you don't mind the risk of getting blown up for your valuable insides, you could still dress up as an ATM.
Re:That's not a flaw... (Score:1, Insightful)
offsetting my apparent position could be as useful as making me disappear entirely!
Not when you are trying to use it to sneak around in the women's locker room.
So you're saying... (Score:2, Insightful)
It took a team from MIT to walk to the side of the object, look at the object and report that the object could be seen? I think this cloak managed to hide something other than the object....
Re:Finally!!! (Score:0, Insightful)
Am I right?
Re:The fatal flaw is: (Score:3, Insightful)
I thought the problem was the expulsion of highly-charged particles? Plasma, or whatever it's called. After all, the thing's gotta have a tailpipe.
Re:bummer (Score:3, Insightful)
They did. Then they switched it on, and ever since they are seeking the device.
0.2 units high by 0.15 units? (Score:4, Insightful)
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:Have they considered... (Score:2, Insightful)
Re:Shoot to miss (Score:2, Insightful)
That might work. A 6 ft soldier would appear to be displaced by about 4.5', if that ratio holds.
Re:Military Applications (Score:3, Insightful)
Re:I guess? (Score:2, Insightful)
Not if it realizes you're likely behind a cloak and just adjusts itself with some nifty math.
But ... that was my first thought as well.
Okay, so I'm not invisible, but you still don't actually know where I'm at so its close enough for a lot of neat things.
I suspect however, that much like in the fantasy of StarTrek (sorry to burst some of your bubbles :) and root kit detection, theres always a way to detect the target, but knowing the right way to look for it is half the battle.
In general, Stealth aircraft just hide from radar. Sure they are difficult to see in general due to paint scheme and normal hours of operation and all that, but its biggest threat is from radar, and its very stealthy against that. But if you put any of the known stealth aircraft out in the middle of the clear sky, you can pick it up visually from a good distance during the day.
You don't have to be invisible from every method of detection, just the one being used to detect you.
Re:Soo.... (Score:2, Insightful)
Well, they probably did and really knew about it for a long time, but geeks being geeks, these minor details probably didn't come out because they were so proud of what they had accomplished, and rightfully so. Even a cloak that works head on is freaking impressive to the point of becoming magic. I know they are just wave guides, but its still freaking impressive.
With that in mind, someone comes a long and notices it a long time later and points it out and the scientists are like 'yea well, we haven't got to that part yet' and we get to here.
Either way, they didn't say 'it only works from head on', they said something entirely different. Technically it doesn't appear to work 'head on' by certain definitions.
They'll probably be lots of gotcha's for a while. Its new tech.
Either way, if I can get one of these things so my son can have it when he's in high school it would be awesome. Muahahahahahaha
Re:The fatal flaw is: (Score:5, Insightful)
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.
Re:I guess? (Score:3, Insightful)
No, it's really not. Anti-tank weapons usually require a direct hit for a kill, or a very near hit to do significant disabling damage.
For example,
- smaller anti-tank missiles like the US Javelin or Soviet RPG use shaped charges (HEAT) that need to have virtually direct hits for the superheated metal core to penetrate armor.
- air to surface missiles like the AGM-65 Maverick use kinetic energy to penetrate the target before exploding.
- the Hellfire and various other popular TOW systems are only effective with hits perpendicular to the top of the vehicle.
In these cases, a near miss is at most likely to cause a roll, secondary damage to the rad or tracks/tires, or the need to repaint the vehicle upon return to base.