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Building an 'Invisibility Cloak' With Electromagnetic Fields

Soulskill posted about 8 months ago | from the easier-than-building-them-with-corn-fields dept.

Science 71

Nerval's Lobster writes "University of Toronto researchers have demonstrated an invisibility cloak that hides objects within an electromagnetic field, rather than swaddling it in meta-materials as other approaches require. Instead of covering an object completely in an opaque cloak that then mimics the appearance of empty air, the technique developed by university engineering Prof. George Eleftheriades and Ph.D. candidate Michael Selvanayagam makes objects invisible using the ability of electromagnetic fields to redirect or scatter waves of energy. The approach is similar to that of 'stealth' aircraft whose skin is made of material that absorbs the energy from radar systems and deflects the rest away from the radar detectors that sent them. Rather than scattering radio waves passively due to the shape of its exterior, however, the Toronto pair's 'cloak' deflects energy using an electromagnetic field projected by antennas that surround the object being hidden. Most of the proposals in a long list of 'invisibility cloaks' announced during the past few years actually conceal objects by covering them with an opaque blanket, which becomes 'invisible' by displaying an image of what the space it occupies would look like if neither the cloak nor the object it concealed were present. An invisibility cloak concealing an adolescent wizard hiding in a corner, for example, would display an image of the walls behind it in an effort to fool observers into thinking there was no young wizard present to block their view of the empty corner. 'We've taken an electrical engineering approach, but that's what we are excited about,' Eleftheriades said in a public announcement of the paper's publication. (The full text is available as a free PDF here.)"

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71 comments

Error, Error. (4, Interesting)

girlintraining (1395911) | about 8 months ago | (#45417169)

Invisibility cloaks like this only work within a certain range of EM frequencies. Outside of that range, it won't work; in fact it may even amplify the signal and make it more obvious whatever is being cloaked. And there are some thing no amount of cloak can deal with. You can alter the optical properties of a thing, but if it's out-gassing several thousand degree plumes... you cannot mask the infra red signature of that. These new meta materials may help in communications, but I highly doubt they will ever be able to make large human-sized physical objects disappear to any current multi-sensor technology.

Re:Error, Error. (3, Insightful)

i kan reed (749298) | about 8 months ago | (#45417261)

Sure, pragmatic constraints affect every design. But if you're worried about being spotted by cosmic rays, that's a lot better than being worried about being spotted by guards or radar.

Re:Error, Error. (3, Interesting)

girlintraining (1395911) | about 8 months ago | (#45417523)

Sure, pragmatic constraints affect every design. But if you're worried about being spotted by cosmic rays, that's a lot better than being worried about being spotted by guards or radar.

I'd be more worried about dying of cancer, honestly. And metamaterials do offer the promise of light-weight shielding against radioactivity in space -- as has been pointed out, they do operate over certain ranges of frequencies. I'm just tired of people calling them 'invisibility cloaks', when all they're doing is reflecting emissions at certain frequencies in a novel fashion. There are a great many useful applications for this... but "invisibility cloak" doesn't make the list. Sorry. That's bad science.

Re:Error, Error. (0)

Anonymous Coward | about 8 months ago | (#45418331)

That's not say this could not be useful though. I would like to know what the environment is like inside the cylinder. Perhaps it's not as dangerous within it.

The stealth fighters and bombers we have today are not invisible, but if they are invisible to radar, that's just as good. You're left with visible confirmation only and that's not very useful in those kinds of circumstances.

I would love a car that is immune to radar detectors.

Cloaking! (1)

fyngyrz (762201) | about 8 months ago | (#45420111)

The Klingons are going to be pissed we've got this technology too. Nothing quite as entertaining as a pissed-off Klingon, either.

Re:Error, Error. (0)

Anonymous Coward | about 8 months ago | (#45418387)

And metamaterials do offer the promise of light-weight shielding against radioactivity in space

What? That makes little to no sense considering a lot of the radiation in space involves wavelengths smaller than atoms, so a metamaterial for those wavelengths would not be constructable. Metamaterials for slightly longer wavelength stuff even would have limited uses because the coupling would still suck.

Re:Error, Error. (3, Insightful)

nospam007 (722110) | about 8 months ago | (#45417379)

"Invisibility cloaks like this only work within a certain range of EM frequencies. "

Just like a concrete or brick wall. It works only within a certain range of EM frequencies.
With the right viewing system, you can see right through.

Re:Error, Error. (0)

Anonymous Coward | about 8 months ago | (#45417495)

You just need to make the antennas big enough to cover the object...

Not even invisible (1)

Geoffrey.landis (926948) | about 8 months ago | (#45417595)

And this isn't even an "invisiblity" shield-- what it is, is a radar-scattering device.

From the article, apparently it scatters an incident radar beam so that the backscattered part (the part that returns to the transmitter) is zero. Specifically, they "then carefully modulated the current on each element to modify the field such that it deflected microwaves aimed at an aluminum cylinder in every direction except back toward the source of the microwaves, where the object could be detected."

So the object isn't invisible at all, except to observers who are looking at it from exactly the direction of the illumination-- in all other directions, it reflects brightly.

Furthermore, who the heck wrote this sentence: "using the ability of electromagnetic fields to redirect or scatter waves of energy." It is a feature of electromagnetic fields that they pass through each other (except in materials of strongly nonlinear index, of which air is not one.) You can't scatter one beam of light with another one!

Re:Not even invisible (1)

mcgrew (92797) | about 8 months ago | (#45425808)

You can't scatter one beam of light with another one!

No, but you can cancel light out [wikipedia.org] with more light [angryflower.com] . And this does make an object invisible, if tuned to the wavelength you want it to be invisible in.

The trouble is, you could tune it to work in visible light but only if that light were coherent (as in, comes out of a laser). You can't get incoherent light out of phase with itself because it's a wide range of frequencies and all completely incoherent, like snow on an analog TV.

Re:Not even invisible (1)

Geoffrey.landis (926948) | about 8 months ago | (#45437573)

You can't scatter one beam of light with another one!

No, but you can cancel light out with more light.

You can cancel light out in specific directions, but the price of nulling the interference in some directions is increasing the intensity in others. It's that conservation of energy thing. On the average, you make the object brighter

And that really isn't "invisibility"-- you can't see through the object. It's just a complicated way of achieving the same effect as painting the object black. Except it's only "black" for a selected wavelength in a selected direction.

...The trouble is, you could tune it to work in visible light but only if that light were coherent (as in, comes out of a laser). You can't get incoherent light out of phase with itself because it's a wide range of frequencies and all completely incoherent, like snow on an analog TV.

Right.

Re:Error, Error. (1)

fahrbot-bot (874524) | about 8 months ago | (#45418069)

You can alter the optical properties of a thing, but if it's out-gassing several thousand degree plumes... you cannot mask the infra red signature of that.

Meaning, "The thing's got to have a tailpipe." So, you've seen Star Trek VI: The Undiscovered Country [wikipedia.org] ...

Re:Error, Error. (1)

Boronx (228853) | about 8 months ago | (#45420127)

But they never established that Enterprise was studying gaseous anomalies, only Excelsior

Re:Error, Error. (2)

slick7 (1703596) | about 8 months ago | (#45419453)

but I highly doubt they will ever be able to make large human-sized physical objects disappear to any current multi-sensor technology.

Two words, Philadelphia Experiment.

Re:Error, Error. (0)

Anonymous Coward | about 8 months ago | (#45420799)

but I highly doubt they will ever be able to make large human-sized physical objects disappear to any current multi-sensor technology.

Two words, Philadelphia Experiment.

I'll take your two and raise you two

Magnetic mines and morons

Re:Error, Error. (1)

slick7 (1703596) | about 8 months ago | (#45447777)

I'll take your two and raise you two

Magnetic mines and morons

They both exist, ergo your argument is invalid.

Re:Error, Error. (0)

Anonymous Coward | about 8 months ago | (#45420257)

Heavier than air flying machines are impossible. -- Lord Kelvin, President, Royal Society, c. 1895

I also have a picture of the Wright brothers flying about 8 years later. But thanks for your input.

Re:Error, Error. (1)

aaronb1138 (2035478) | about 8 months ago | (#45420715)

Works in the microwave band eh? Can I get one of these in the K/Ka band for my automobile?

Re:Error, Error. (0)

Anonymous Coward | about 8 months ago | (#45422433)

You seem to believe that it's a 100% given that the bourgeois (us) will always have our tricorders handy. Some/many people may be watched in the future with this and they won't know it. Big Brother tool.

I'm sure it's technology that will continue to mature.

Just as I thought! (4, Insightful)

DontBlameCanada (1325547) | about 8 months ago | (#45417181)

Canada is harbouring dissident Romulan scientists brought here by James T. Kirk (Canadian William Shatner).

Re:Just as I thought! (1)

Anonymous Coward | about 8 months ago | (#45417519)

It's all fun and games until INVISIBLE ZAMBONIS

Re:Just as I thought! (2)

sconeu (64226) | about 8 months ago | (#45418291)

And then... the dreaded Zamboni Apocalypse....

Re:Just as I thought! (1)

cold fjord (826450) | about 8 months ago | (#45418751)

And then... the dreaded Zamboni Apocalypse....

World War Freeze-Z

Re:Just as I thought! (1)

cold fjord (826450) | about 8 months ago | (#45418813)

Canada is harbouring dissident Romulan scientists brought here by James T. Kirk (Canadian William Shatner).

Which is why the Borg tried to invade the Earth in the past, before the Federation obtained cloaking shield technology with hundreds of years of refinement.

Re:Just as I thought! (0)

Anonymous Coward | about 8 months ago | (#45421433)

Once upon a time. There were three pigs. A big pig. A little pig. A medium sized pig. They all participated in massive orgies with all the other animals in the district. Until a newcomer with a massive cock, and also every STD ever, appeared and fucked all the locals. They all died. Including the three pigs. The newcomer then died. The end.

Re:Just as I thought! (1)

mcgrew (92797) | about 8 months ago | (#45425846)

William Shatner is Canadian, but James T. Kirk is from Iowa. Sheesh, you never watched any Star Trek movies? Besides, Captain James Kirk is now captain of the USS Zumwalt [cnn.com] , a navy destroyer that has a cloaking device! TFA: "When its begins missions, the Zumwalt will be the largest stealth ship in the Navy."

I wish they'd stop calling it that. (4, Insightful)

Lumpio- (986581) | about 8 months ago | (#45417191)

I think it's only justified to call something an "invisibility cloak" when it does what people actually expect an invisibility cloak to do, that is, make things actually not visible. How about calling it a "stealth cloak" because that's what I imagine most people would associate with being invisible to a radar, as opposed to the naked eye.

Re:I wish they'd stop calling it that. (1)

Anonymous Coward | about 8 months ago | (#45417291)

I think it's only justified to call something an "invisibility cloak" when it does what people actually expect an invisibility cloak to do, that is, make things actually not visible. How about calling it a "stealth cloak" because that's what I imagine most people would associate with being invisible to a radar, as opposed to the naked eye.

Won't you please think of the clickbait?

Re:I wish they'd stop calling it that. (1)

JeanCroix (99825) | about 8 months ago | (#45417299)

They're quick to point out that it's not actually a cloak, either. Shades of the Holy Roman Empire...

Re:I wish they'd stop calling it that. (1)

Mr D from 63 (3395377) | about 8 months ago | (#45417557)

Can you be wrapped in invisibility? I think not.

Doesn't matter, someone will just come along with a uninvisiblity uncloaker and sell it to the enemy. Isn't that how it always goes?

Re:I wish they'd stop calling it that. (1)

EdIII (1114411) | about 8 months ago | (#45418351)

Can you be wrapped in invisibility? I think not.

You obviously never suffered through high school...

Or my life. (0)

Anonymous Coward | about 8 months ago | (#45418723)

:^S

Re:Or my life. (1)

Anarchduke (1551707) | about 8 months ago | (#45420469)

Huh, a completely blank post. Must be an error on the slashdot server.

Re:I wish they'd stop calling it that. (1)

radtea (464814) | about 8 months ago | (#45417843)

After that, maybe they could try writing a remotely accurate summary, too! The summary is borderline gibberish, as it is impossible (in linear materials) for EM fields to "deflect" each other.

This "cloak" is interference-based, using active dipoles to generate a field that cancels the scattered field in the forward (0 degree) and backward (180 degree) directions. It's a clever piece of work, but there are fairly hard limits to the how wide an angle such techniques can cover, and moving from an essentially 2D scenario to full 3D increases the complexity enormously, although I'd love to see them try it.

Re:I wish they'd stop calling it that. (1)

Anonymous Coward | about 8 months ago | (#45417867)

but you won't get as many hits and advertising revenue if you do it that way, son

Go ahead and stick your dick right in those dollar bills you whores

Re:I wish they'd stop calling it that. (0)

Princeofcups (150855) | about 8 months ago | (#45418239)

I think it's only justified to call something an "invisibility cloak" when it does what people actually expect an invisibility cloak to do, that is, make things actually not visible. How about calling it a "stealth cloak" because that's what I imagine most people would associate with being invisible to a radar, as opposed to the naked eye.

How about flying cars? Or cure for cancer? Or pioneer probe in interstellar space? The list goes on.

Re:I wish they'd stop calling it that. (1)

AK Marc (707885) | about 8 months ago | (#45419393)

And all it'll do is change radar to be separate radiators from receivers. With that done, active radar will "penetrate" the cloak without issue, and passive detection would be mostly unaffected.

irrelevant (1)

Anonymous Coward | about 8 months ago | (#45417319)

Invisible : Invisible to Radar :: Edible : Edible by Sperm Whales

MMPPI (0)

Anonymous Coward | about 8 months ago | (#45417333)

Magnetic Multiplexed Photon Phase Inversion?

Geeze (0)

Anonymous Coward | about 8 months ago | (#45417375)

What a redundant and poorly written summary.

Just destructive interference? (1)

joe_frisch (1366229) | about 8 months ago | (#45417393)

I may be missing how this works, but it looks like they are driving a bunch of antennas to cancel the scattered radiation from an object in one direction. While this works, the trick is to know exactly what the input signal is and the react in time to cancel - something that can only work for very narrowband sources or sources where you know the input field (including its phase) in advance.

I don't see how this could work for radar or light.

Re:Just destructive interference? (5, Funny)

Mr D from 63 (3395377) | about 8 months ago | (#45417761)

I don't see how this could work for radar or light.

Of course you can't see it working. Thats the point.

Re:Just destructive interference? (1)

Vitriol+Angst (458300) | about 8 months ago | (#45421711)

Magnetic stealth is the perfect cloaking mechanism -- just as long as the enemy never launches anything metallic at it, they are home free!

Re:Just destructive interference? (1)

Zorpheus (857617) | about 8 months ago | (#45417813)

So "the ability of electromagnetic fields to redirect or scatter waves of energy" means that they just send out electromagnetic waves that interfere with the waves around the object? Was already wondering since when electromagnetic fields can redirect electromagnetic waves. That only works in Star Trek.

Re:Just destructive interference? (1)

joe_frisch (1366229) | about 8 months ago | (#45417875)

I think you are right. The cross-section for photon / photon scattering at low energies is really tiny - maybe never observed at optical wavelengths or longer. (there might be some result I don't know about).

The article makes it sound much cooler than it is - but its still kind of a nice demonstration and not easy.

Re:Just destructive interference? (1)

Zorpheus (857617) | about 8 months ago | (#45421109)

Yes, it is more obvious in classical electrodynamics. For all waves and electromagnetic fields the superposition principle can be applied because the Maxwell equations are linear. This means that if you add any fields or other waves to an incoming wave you can describe the result mathematically as the sum of the incoming wave and whatever you generate.
According to the Maxwell equations the incoming wave is influenced by susceptibility and permeability of the materials it is going through, and by charges and currents. But waves and fields are just added to the fields of it, they do not change the original wave. So to compensate changes in a wave you have to add a wave that compensates the changes, and this wave must be actively adapted to the incoming wave.

My Summary.... (1)

bobbied (2522392) | about 8 months ago | (#45417439)

I just don't see this working......

Invisibility Cloak? (1)

Anonymous Coward | about 8 months ago | (#45417459)

Instead of trying to make something invisible (isn't that hyper-impossible anyway?), why don't we just put an SEP field over it?

Pics or it didn't happen! (1)

QilessQi (2044624) | about 8 months ago | (#45417647)

Oh, wait... I guess the absence of pictures is proof that they succeeded. Bravo!

Project rainbow anybody? (0)

Anonymous Coward | about 8 months ago | (#45417769)

Wasn't this already done with project rainbow ? I don't remember it working out to well for the sailors ;)

Invisibility Cloak, yeah right (3, Insightful)

Rotag_FU (2039670) | about 8 months ago | (#45417889)

And I thought it was just the mayor smoking crack, apparently the whole town is now. :)

Re:Invisibility Cloak, yeah right (0)

Anonymous Coward | about 8 months ago | (#45419987)

And I thought it was just the mayor smoking crack, apparently the whole town is now. :)

The cloud makes them invisible

Re:Invisibility Cloak, yeah right (1)

fishicist (777318) | about 8 months ago | (#45421757)

The word "invisible" does not appear in the paper. The authors call this cloaking, not invisibility.

Nice try, but.. (1)

drewsup (990717) | about 8 months ago | (#45417895)

We have had this tech for over 40 years! Track Break Notch will do similar things by either walking a radar off you, or move your position according to what the radar can see.
The bigger problem is millimeter band radar, you need really funky waveguides to broadcast these as a normal antenna can't cope the small wave frequency.
The A6 from the Navy and the EF-111A from the USAF both could manage similar things to this, I can only hope they have managed to it smaller as the units for each section of bandwidth were the size of a small coffin, and you needed LOTS to cover the threat assessment for a given area.
Smells more like grant sniffing to me..

Projectile vulnerability (1)

dohzer (867770) | about 8 months ago | (#45417917)

Good luck scattering and redirecting the rocks I start throwing in every direction once this technology is widely available.

Already figured it out (1)

Gary (9413) | about 8 months ago | (#45418003)

I already have a more practical invisibility capability. I just talk to management about actual technical topics. I become invisible to them almost immediately.

How is this Datacenter? (0)

Anonymous Coward | about 8 months ago | (#45418263)

Another Verge-esque Slashdot self-post... They need better topics breakdown for the "topical" slashdot.

Philadelphia Experiment, anyone? (1)

lamer01 (1097759) | about 8 months ago | (#45418643)

I mean, didn't his cause havoc already?

hmmm (1)

slashmydots (2189826) | about 8 months ago | (#45418881)

For those of you asking "Why no picture" there actually is one.
1. go to google
3. type "empty field"
Tada, picture of an invisible car.

Re:hmmm (1)

slashmydots (2189826) | about 8 months ago | (#45418885)

What the hell?! It seriously ate step 2 for absolutely no reason! What kind of stupid filter does Slashdot have? Let's try again:
2. click on images

Ironic that a step about invisibility disappeared btw.

Re:hmmm (0)

Anonymous Coward | about 8 months ago | (#45420787)

Because you violated the basic law.

Everyone knows step 2 is ??? and step 3 is Profit!

Tesla Proven Right,Again (2)

Geek Hillbilly (2975053) | about 8 months ago | (#45419619)

Sounds an awful lot like the Philadelphia Experiment except on a smaller scale. Not surprising that the work of Nikola Tesla,which in a lot of ways was way ahead of its time,is being re-examined.How many more of his discoveries will finally see the light of day after being suppressed for 60 or 70 years? All I can say is this -> "You Ain't seen Nothing Yet"

Move along... nothing to see here (1)

bshell (848277) | about 8 months ago | (#45420333)

Seriously, the paper does not report on anything like visible light invisibility. That's not what this is. This is a case of misleading labelling.

Troy Hurtubise's next project (0)

Anonymous Coward | about 8 months ago | (#45420341)

will be a bizarre projector that came to him in a dream that will see right through that cloak.

very old technology (1)

peter303 (12292) | about 8 months ago | (#45422625)

It goes back to stealth technology in microwave region.

Finally (0)

Anonymous Coward | about 8 months ago | (#45422813)

Canada's military snowmobile brigade can attack undetected

here I come (1)

Pharoah_69 (2866937) | about 8 months ago | (#45425276)

Klingon War Bird of Prey (with 2 big-breasted Klingon women), here I come.

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