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## Fatal Flaw Discovered In Invisibility Cloaks255

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."
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## Fatal Flaw Discovered In Invisibility Cloaks

• #### bummer (Score:2, Insightful)

by Anonymous Coward
bummer.
• #### The fatal flaw is: (Score:2, Insightful)

by Anonymous Coward

They DON'T WORK!

• #### Re:The fatal flaw is: (Score:5, Funny)

on Monday April 19, 2010 @05:09PM (#31902216)
I can't see how they could work.
• #### Re: (Score:3, Informative)

I am amused at the correlation between your comment and your sig. Well done, sir.
• #### Re: (Score:2)

"Invisibility cloak?!? Ha! I'll believe it when I see it!"
so, do you believe it now that you can kinda see it from an angle? :-)
• #### Re: (Score:3)

WSpock, "the solution is transparent to the user."
Kirk, "now everyone knows why Kligons looked a scant shifty."
• #### Re:The fatal flaw is: (Score:5, Insightful)

on Tuesday April 20, 2010 @01:04AM (#31906582) Homepage

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:The fatal flaw is: (Score:5, Funny)

on Monday April 19, 2010 @05:21PM (#31902368) Homepage

No, the fatal flaw is that a cloaked object moving at warp speed emits a slight subspace variance. Adversaries performing an antiproton scan may also be a problem.

• #### Re:The fatal flaw is: (Score:5, Funny)

on Monday April 19, 2010 @05:25PM (#31902400) Homepage Journal

What if we modify the phase variance?

• #### Re:The fatal flaw is: (Score:5, Funny)

by Anonymous Coward on Monday April 19, 2010 @05:39PM (#31902564)

What if we modify the phase variance?

yeah, as long as we randomly modulate the shield frequencies, reverse the polarity of the heisenberg compensators, and amplify the transporter buffers... we should be good to go. Earl Grey tea never tasted so good.

• #### Re: (Score:2)

Don't forget to note, and share with others, the differences between self-sealing stem bolts and warp matrix flux capacitors.

• #### Re:The fatal flaw is: (Score:5, Funny)

on Monday April 19, 2010 @07:05PM (#31903784)

This solution will never work.

No one has even suggested routing extra power to the main deflector array yet.

• #### Reverse the polarity? (Score:5, Funny)

on Monday April 19, 2010 @06:26PM (#31903304) Homepage Journal

What if we modify the phase variance?

yeah, as long as we randomly modulate the shield frequencies, reverse the polarity of the heisenberg compensators, and amplify the transporter buffers... we should be good to go. Earl Grey tea never tasted so good.

Now see here... If the polarity of anything is to be reversed, then clearly we should start with the neutron flow...

• #### Re:The fatal flaw is: (Score:4, Funny)

on Monday April 19, 2010 @09:19PM (#31905056) Homepage Journal

amplify the transporter buffers

No, no, no. You need to narrow the angular confinement beam.

• #### Re:The fatal flaw is: (Score:5, Informative)

on Monday April 19, 2010 @06:00PM (#31902926) Homepage
Nah, that can easily be defeated by a tachyon burst, particularly if you invert the polarity of the shield harmonics.
• #### Re: (Score:3)

As far as anyone's sensors were concerned, that'd light you up like a Christmas tree.

• #### Re: (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:5, Funny)

on Monday April 19, 2010 @05:18PM (#31902328) Homepage Journal
They should be working on a "Somebody Else's Problem" field. I hear that this is much easier than trying to much around with physics.
• #### Re: (Score:3, Insightful)

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

• #### Re:bummer (Score:5, Funny)

<bfelger AT gmail DOT com> on Monday April 19, 2010 @05:54PM (#31902828)

Unfortunately, every member of the search team is slacking off, assuming someone else is looking for it.

• #### Re: (Score:2)

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

You gave me a great idea: use the invisibility cloak to take a nap at work! As long as you're nowhere someone's likely to trip over you and don't snore too loudly you'd have it made!

• #### Re: (Score:2)

Still, it's better than a fatal flaw that causes users to spontaneously combust.

• #### Re: (Score:2)

At least that would have been funny!

• #### Cheer up (Score:5, Informative)

on Monday April 19, 2010 @05:42PM (#31902620) Journal

Well, cheer up. It might still mean that the Romulan's weapons hit some nearby console when they think they're targeting the warp core. Of course, it would be better if they didn't hit anything at all, but I'm affraid that the law that for each hit a console must explode in a shower of sparks and send some ensign flying across the room is more immutable than the laws of refraction ;)

• #### Re: (Score:3, Interesting)

They don't have to be perfect; they just have to be good enough. Nor do that have to work all the time; they just need to work when needed, and for just long enough to allow the first shot. ("Spock, what's tha...doh!")
• #### Wrong Cloak (Score:5, Insightful)

<sabotage&praecantator,com> on Monday April 19, 2010 @05:03PM (#31902122) Homepage

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.

• #### Re:Wrong Cloak (Score:5, Funny)

on Monday April 19, 2010 @05:07PM (#31902188)
Better a D&D reference than another of the endless Harry Potter ones...
• #### Re: (Score:2)

Better a D&D reference than another of the endless Harry Potter ones...

I haven't seen a single Harry Potter reference so far. It's been all Star Trek.

I guess people just figure everyone already knows about the various workarounds like the Marauder's Map and so on...

• #### I guess? (Score:4, Insightful)

on Monday April 19, 2010 @05:03PM (#31902124) Journal

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

• #### Re: (Score:2)

If it's optically tracked, sure. You might be out of luck if the operator is using IR.

• #### Re: (Score:2)

That's what I'm saying. Shifting the apparent location of a target is almost as good.
• #### Re:I guess? (Score:5, Interesting)

<arancaytar.ilyaran@gmail.com> on Monday April 19, 2010 @05:30PM (#31902462) Homepage

Depends on the size of the missile...

• #### Re: (Score:2)

I think you'll find it's less about the size of the missile and more about the yield of the warhead.

One of the advantages to 10+ Mton nuclear warheads, is that you don't need to be very precise

• #### Re: (Score:3, Informative)

No, it's about the size of the missile. The warhead is always listed in pounds but the potential is always listed in kinetic energy.

For example, the BrahMos has 32 times the kinetic energy of the Tomahawk, despite having a warhead 3/5 the size. It is by far much more destructive than our Tomahawk because of its higher mass and higher velocity capability.

• #### Re: (Score:2)

Maybe so but a broad spray of shrapnel and bullets won't. Even rain could defeat a cloak unless the rain goes right through it without resistence.

• #### Re: (Score:2)

Two words. Splash. Damage.
• #### Re: (Score:2)

Two words. Splash. Damage.

That's four words.

Or were you saying that "Two words" is two words? Seems like a bit of a tautology, though maybe not for the reason you'd think...

• #### Re: (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 j

• #### Military Applications (Score:5, Interesting)

on Monday April 19, 2010 @05:04PM (#31902136)

I'm sure a carpet cloak like this would have military applications, and in a desert environment like the Middle East, people aren't going to notice you unless they're close to you.

A sniper on a ridge covered with one of these babies is still going to do the job.

• #### Re: (Score:2)

So if I understand this right TFA says that these cloaks just render something as appearing where it isn't rather than completely invisible when viewed from various angles?

If so that's still got the possibility of being pretty bloody useful.

• #### Re: (Score:2)

At least it could hide things from satelites, since they don't look down at any significant angle.

• #### Re: (Score:2)

They do look down at significant angles. This is why you have to hide stuff you don't want seen whenever the spy satellite is over the horizon, not just when its over head. The operators get to decide when to use fuel (or bleep off a flywheel) to reorient a satellite.
• #### Re: (Score:2)

I'm sure a carpet cloak like this would have military applications

Sure, if you have soldiers the size of a pinhead.

But then, remember that all the jihadists have to do is move sideways a bit and "ha ha, we can see your pinhead, you silly infidel !"

• #### Soo.... (Score:4, Insightful)

on Monday April 19, 2010 @05:05PM (#31902150) Homepage
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.... (Score:5, Insightful)

on Monday April 19, 2010 @05:12PM (#31902262)

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: (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

• #### Finally!!! (Score:4, Funny)

on Monday April 19, 2010 @05:06PM (#31902164)
At last, my sig is actually appropriate for a slashdot story!
• #### I see no sig... (Score:2, Funny)

I'm sorry, my "Disable sigs" preference has completely cloaked your sig.

• #### Re: (Score:2)

Try looking at your monitor sideways!

• #### Fatal Flaw Discovered In Invisibility Cloaks (Score:3, Funny)

by Anonymous Coward on Monday April 19, 2010 @05:06PM (#31902178)

You could bump into the invisible object.

• #### Props to Soulskill (Score:3, Insightful)

on Monday April 19, 2010 @05:11PM (#31902240) Journal
...for making a Wing Commander reference (from the books, not the horrific movie that by coincidence has the same name) in the "department" byline for this story.
• #### Re: (Score:2)

...for making a Wing Commander reference (from the books, not the horrific movie that by coincidence has the same name) in the "department" byline for this story.

Wow, given the implied Scottish accent in "you-cannae-fire-while-cloaked", I actually would have thought that was a reference to Scotty from Star Trek.

Apparently, I'd have been wrong. Of course, one can argue that any Scottish accent in Sci Fi after Scotty is, by definition, an homage to the great engineer -- and, for purposes of discussion, I bel

• #### Re: (Score:2)

There were Wing Commander books? I'm only familiar with the Wing Commander video games that were the basis for the movie.

• #### Pictures (Score:4, Informative)

on Monday April 19, 2010 @05:12PM (#31902260)
I demand more pictures of invisibility cloaks in articles about invisibility cloaks. Theory be damned.
• #### invisiball (Score:2)

but will the cloaks still work when shaped like small* spheres?

*small where you are almost looking radial from any direction

• #### What happens... (Score:2, Interesting)

What happens when you layer them? I mean, if you overlap a bunch of these invisibility carpets, what would you end up looking at?
• #### Shoot to miss (Score:4, Interesting)

<brian.dunbar@NoSPAm.gmail.com> on Monday April 19, 2010 @05:17PM (#31902318) Homepage

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.

Maybe. But it would be a great way for soldiers to conceal themselves from aimed rifle fire.

• #### Re: (Score:2, Insightful)

That might work. A 6 ft soldier would appear to be displaced by about 4.5', if that ratio holds.

• #### Re: (Score:2)

So what if you took two of them and overlapped them at 45 degree angles? I realize that's not quite descriptive enough to clarify my line of thought, so let me elaborate:

Say I have a cube covered by this thing. When looking at it from a 45 degree angle, I see the cube displaced.

So what if I then take another slightly-larger carpet cloak and prop it up 45 degrees off-axis such that when I look at this outer cloak straight-on, I see "through" the outer cloak, and when I look at it at 45 degrees, I see
• #### Re: (Score:2)

Couldn't they just use two cloaks placed at the appropriate angles in relation to each other?

• #### Oh, well.... (Score:2)

guess I'll have to postpone that trip to Mordor.
• #### Disappointing (Score:4, Interesting)

on Monday April 19, 2010 @05:23PM (#31902380)
I don't know about you, but when I hear the phrase "fatal flaw," I really expect something a little more, I don't know... hilarious.
• #### Re: (Score:2)

If you look at the invisibility cloak the wrong way, it kills you!

• #### Re: (Score:2)

> If you look at the invisibility cloak the wrong way, it kills you!

Those are Soviet invisibility cloaks.

• #### Re: (Score:2)

As in "In Soviet Russia, invisibility cloaks look through you... after blasting a hole in you?"

• #### They're right! (Score:2)

When I take two steps to the right, all of a sudden all I see are AC posts modded down to -1. It appears the Slashdot moderation system is angle-dependent! I'm sure to win the Nobel for this.
• #### 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....

• #### 0.2 units high by 0.15 units? (Score:4, Insightful)

on Monday April 19, 2010 @05:36PM (#31902534)

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: (Score:3, Interesting)

What is that in Libraries of Congress?
• #### ever since they discoverd this theoretical flaw (Score:3, Funny)

<circletimessquareNO@SPAMgmail.com> on Monday April 19, 2010 @05:39PM (#31902562) Homepage Journal

in a theoretical device, i have been theoretically impressed

• #### The Fatal Flaw (Score:2)

You will still get pushed off the subway platform by the crowd, or hit by a bus that doesn't see you!
• #### two obvious solutions (Score:2)

1. Roll up the carpet.
2. Put the object in a carpet, then put the carpeted object in another, slightly angled carpet, then put THAT into yet another slightly more angled carpet, and that entire batch into still yet another, even more slightly angled carpet, etc, until all angles are covered.

Remember the "Wonder Woman - Invisible Man - Superman Encounter"?

I'll pass on the cloak in any event, thanks.

• #### I'm suspicious... (Score:2)

For all the talk of cloaking technologies I hear around here, this is the first I've heard of this one. Sure, I'm not an expert in the field, but if this "took the world by storm" last year, I'm surprised no news stories ever reached me.

Most suspicious, though, are the references to this as a technology for which practical devices have been built. The effect described in TFA is something you could see empirically if you had a working model; you don't need someone to draw a diagram showing the course of a

• #### There must be lots (Score:2)

of circumstances where any viewpoint other than roughly straight on is impractical - for example looking at someone through a tunnel, or someone a long way off through a telescope where to get any viewpoint from a significantly different angle would take a lot of walking. Presumably it works just fine then.
• #### simple solution (Score:2)

rotating mirror mount?

• #### FIRST POST!!!1 (Score:2)

... Although, if TFA is to be believed, it won't appear to be.
• #### Re: (Score:2)

When viewed from an angle, your first post has a fatal flaw.

• #### Thermals... (Score:2)

... wouldn't these "invisibility cloaks" be easily defeated with thermal detection equipment?

• #### Displacement is still fatal. (Score:2)

The displacement isn't as useful as everyone thinks. Anything that is wider than it is tall will still get hit by any shot that's near center or to the correct side of the displacement, and some shots that would have missed will be hits. Actually anything whose height to width ratio is 4:3 or lower will still get hit. That covers a lot of the military equipment you'd want to hide - tanks, planes, ships, most buildings, most vehicles, anyone not standing up, etc.