Engage the Cloaking Device

And one of my favorite gadgets in science fiction is the cloaking device. Now, the earliest example I can remember from my own personal experience is from Star Trek, because the Klingons and the Romulans in Star Trek had access to technology that could render their ships not just undetectable by sensors, but completely invisible. So this goes beyond stealth technology, which uses materials and architecture to confound devices like radar.

I'll talk more about that later, but this would be a technology that could turn an entire spacecraft completely invisible, allowing light and other electromagnetic energy to bend around it in such a way as to seemingly pass through it entirely, so you can think kind of like light in this sense, being like flowing water. Imagine a stream of water flowing downhill, and you place a rock in the middle of that stream, and the water will part around that rock and come

back together on the other side. And so if you're just a little further downstream, you would never know there was a rock there in the first place, because the way the water is flowing, it looks like it's been moving in a straight line the whole time. That's simply the same kind of concept for cloaking devices, except instead

of water, we're talking about electromagnetic radiation. That's the basic premise, right, It somehow is able to bend energy so that it flows around the object and continues on its original trajectory as if nothing were there to begin with. To an outside observer relying upon this type of energy to quote unquote see the cloaked object, it would seem as if nothing were there at all. When it comes to science fiction, writers tend to rely upon terms that sound vaguely futuristic

and scientific, but typically they don't actually mean anything. Most of them rely on fictional energies or materials, but there are real world examples of cloaking devices that I would like to talk about. Before I jump into that, I need to make one thing very clear. The cloaking devices and technologies I'll be covering will not turn objects invisible to the naked eye. They don't work at that end of the electromagnetic spectrum, at least not the ones that

are on the higher tech end of it. Some of them use optical illusions to make it seem that way. This little fact, however, sometimes gets lost in reporting of cloaking technology. The headlines are too good to say new cloaking device makes it a reality, or sometimes the information is included in the reporting and then everyone gets a little bummed out about it because it's not a quote

unquote real cloaking device. I'll also cover a few technologies that create this illusion of a cloaking device under specific criteria, because the solution is actually a kind of clever and a good place to start is with stealth technology. Now I've covered stealth tech in a previous episode of Tech Stuff, but I'm gonna go and cover some of it again right here. I'm just gonna go really light on history, because you can listen to the other episode and get

the full story. I just want to talk about how stealth fighters and stealth bombers work from that stealth perspective. First, I'm sure you've seen pictures of these sorts of vehicles and you might notice right away that they don't appear to be invisible. You can kind of sort of totally see them. One makes them stealth isn't there ability to disappear in front of your very eyes, because they don't have that, but rather their ability to evade detection via radar. Now,

radar works like echolocation. Electromagnetic symbol signals rather beam out from a transmitter, and then those signals collide with an object like a jet. Some of those signals bounce off the jet and bounce back towards the transmitter. You also, besides the transmitter, have a receiver, and the receiver picks up these returning signals and registers that there's an aircraft

present in the airspace. If there's a change in wavelength the radio In the radio signals, you can also deduce if the aircraft is moving toward you or away from you. If the radio waves are longer than they were when you blasted them out, that means the objects moving away. If they're elongated. In other words, if the wavelengths are shorter the object is coming toward you. This is the Doppler of act. It's the same sort of thing you might experience if a car with a siren blasting drives

past you. It sounds higher pitched as the car is coming towards you, and lower pitched as the car is moving away from you. And that's because the sound waves themselves are being compressed in front of the vehicle as it moves towards you, and they're elongated as the vehicle moves away from you. Same sort of thing can happen with electromagnetic waves, and like I said, it's called the

Doppler effect. Also, by looking at the delay between when the radio waves blasted out from the transmitter and when the returning waves were picked up by the receiver, you know how far away the aircraft is because the radio waves travel at a constant speed. So by knowing how much time has passed, you know how how far away the aircraft is. Right, you just measure the amount of time that has passed and then you do a quick calculation to say, well, it traveled x distance in this

amount of time. Let's take half of that at because the signals traveled out and then they traveled back, so half of the full length of travel time is how far away the aircraft is, roughly speaking, So stealth technology is all about foiling that process. The two major methods involved creating a radar absorbent surface, something that is very efficient at absorbing electromagnetic radiation, and then making sure that the aircraft has a particular shape to reflect any other

radio waves in different directions than the origin source. The absorbent surface is a composite material that's made of lots of different lightweight stuff that's really efficient at absorbing radio energy. If the aircraft absorbs the radio waves from a radio antenna, nothing would bounce back and nothing would get picked up by the receiver. So if you had a perfect absorbent material, it would just soak in all those radio waves. Nothing would ever return, so it would never show up on radar.

But we don't have anything that's quite that perfect. The plane's shape plays a really big part in this as well, because a radio wave will bounce off of surfaces and return at an angle, just as if you were to bounce, say a cue ball inside a pool table. You know, if you choose different angles. When you're bouncing the cue ball, it's going to react in a different way. It's going

to bounce off in a different direction. Um And once you know that relationship, then you can start to design surfaces to bounce those radio waves off in directions that are not going to go back toward the receiver. The shape of stealth vehicles tends to include a lot of curved surfaces that seemingly wonky angles. Sometimes you'll get some very flat surfaces as well, but they'll be in odd

positions relative to one another. And this is all to try and foil those radio waves, to make them bounce in a way that's not going to go back to where the receiver is. So the electromagnetic radiation does not pass through the air craft, it doesn't bend around it the way you would say a cloaking device would do, but it does allow you to have a way of eluding radar detection. So it's not really the same sort

of technology that you would find in science fiction. Now, there are other ways you can simulate a cloaking device, such as a method that has been used in several marketing campaigns, and that as to use a series of cameras and screens to simulate a cloaking device. The concept is pretty simple. You start with an object. Let's say it's a Mercedes Benz F Cell concept vehicle, because Mercedes actually did do this as a marketing stunt back in

two thousand twelve. The F Cell, by the way, was a fuel cell prototype vehicle, and I've talked all about fuel cells in other episodes. Pretty fascinating technology anyway. Imagine that you cover one full side of this vehicle, let's say the driver's side of the vehicle, with a mesh that has a bunch of l e d s in it to act as a screen, so the side of the car turns into a low resolution l e ED

television screen. On the other side of the vehicle, you mount a camera and the camera captures everything that's on that side of the vehicle. So it's facing out from the passenger side, so it would be the same kind of point of view as a passenger would have if he or she was looking directly out of their window.

The video feed you pick up from this camera gets fed directly to the other side, to the l e ED screen side of the vehicle, and it displays whatever the cameras have picked up, so you end up getting this illusion. If you stand on the screen side of the vehicle, it's almost like you're looking through it, though at a lower resolution than reality, so it looks a little jankie. Although you could argue that's kind of like a cloaking effect you see in some science fiction shows

and movies where you've got that little shimmery effect. It's kind of like that, but less cool than that. Not so predator. It's a little more uh noticeable. I've seen similar setups to make an effect in costumes that make it look like a person has a hole straight through their torso. It's a pretty cool thing to do. It's

actually really easy if you've got two iPads. For example, Uh they typically will wear a screen on their chest, and then you can put a camera on your back and the camera captures live video from whatever is going on behind you, feeds it to the screen that's hanging on front of your torso, and you cut a hole in a shirt so that it it goes right around the screen and the screen is showing everything that's happening

behind you. So the illusion is that you've got a hole in your torso and people can look right through it and see what's happening on the other side. Uh. Like I said, you could actually do this in a pretty easy way. I saw a clever video that used a pair of iPad two tablet to make this effect on both sides. The guy who published the video's name is Mark Rober. He published the video on YouTube in October two thousand eleven, so you can actually find this video if you want to see how he did it.

But he said he used two iPad two's, one to face out in front and one to face out in back. So the but the screens were facing outward on both sides. One facing one had you know, the back of the iPad two was against his chest. The other one had the back of the second iPad two against his back. And what he did was he just set up a FaceTime call between the two iPads, so each iPad was showing the screen of the other iPads camera and by doing that, you just have this live feed on either side.

So it worked on either side of the person. You could stand in front of them and you're actually looking at the hole that's showing on showing what's going on behind the person, or you could be behind them, and you'd be looking through the hole and you see what's going on in front of that person, so you get this illusion that you have a hole going through a solid Torso it's great if you want to do a

creepy zombie style character at Halloween. I've always wanted to do this, but I've never actually gone out to buy a couple of iPads just to do a costume. It seems like it might be a little much for me, but still pretty neat. However, again, that's not a true cloaking device. I don't think anyone would ever argue that. And for one thing, any set up where you've got a screen and a camera means that you really only

have one side prepared to be quote unquote cloaked. So if you're on the other side of the device or the structure or whatever it is, you would totally see the object or the person standing there because you would be on the camera side, not the screen side. It's kind of like being backstage in a show. You see how everything works, so it's not truly cloaking. But next, we're gonna talk about bending light and something you can

actually do. We can bend light optical lenses do that, so if you wear glasses or contacts, you rely on something that bends light already, and I talked about the physics of optical lenses in an episode not too far back. But if you're clever and you use the right sequence of lenses at the proper distance from one another, you can create an optical illusion equal to a type of cloaking.

And that's the secret behind the original Rochester Cloak, so called because it was developed at the University of Rochester. Now I'll talk more about their approach to cloaking in just a second, but first let's take a quick break to thank our sponsor. The version of the Rochester Cloak I studied had four lenses arranged in a straight line

with several inches separating each lens. So think of it as lens one, two, three, four, And let's say that for the purposes of this description, that the lens closest to someone who's going to look through the Rochester Cloak is lens number one. The furthest lens from the viewer

is lens number four. Now, in the demonstration I viewed the uh the the backdrop for this was a grid pattern, So there was actually a grid pattern in the very back, and the purpose of that was to provide a reference so that when you passed things between the lenses in order to create this cloaking effect, you would still see the grid pattern in the background, and it gives this illusion that you have an unbroken uh line of sight

even when an object is passing between the lenses. So a casual glance through the lenses, it makes it seem like light has just passed through the series of lenses without bending. Like from from lens for two lens one, the effect you get is that the light has just traveled straight through those lenses, because the grids in the

back remains straight, and that becomes your reference point. Right You're looking at the grids and you're thinking, well, the lines look straight, so the light's not really being bent by these lenses. At least that's the optical illusion I have. But what is really happening is some light gymnastics. And I don't mean low impact gymnastics. I mean gymnastics involving light.

Each lens bends the light in a slightly different way, concentrating or spreading out the light, so that if you were to place a small object between Lens one and lens too, So the first two lenses it would look as if you could see right through the object with some limitations. The big limitation is that the cloaking effect only works on the edges of the viewing area of

the lens. So if you think of the lens as a circle, the closer you get to the center of that circle, the closer you're getting to the point where you're going to be able to actually see that object. But if it's on the the edge of the center, then it seems like you can look right through the object. So uh, it's because the light is being bent in such a way that that light is concentrated on the center of lens number one before that lens actually spreads

the light out again towards your eye. And each of these lenses was carefully selected so that it would manipulate the light where it seems like you're looking at an unaltered image. Right, it looks like you're looking at that grid and the lines are straight. In fact, the way that the light is being bent by the lens, if you were to look through lens number two instead of lens number one, the backdrop would look very different. It

wouldn't look like a grid of straight lines. It's because each lens is bending light in a specific way that you're able to create this effect. So it doesn't matter if the object you put between lens one and lens two is a pencil or a finger, it seems like there is nothing there in front of you, or that the middle of the object has disappeared, like if you can see the object on either side of the lens, like if it extends out to either edge, it would

look like the middle is just suddenly gone. But again, this is all just through optics, so it's somewhat limited as it's entirely dependent upon your frame of reference. It depends upon the viewer looking through the lens. If you were to step to the side and look at this apparatus from ninety degrees on, you would observe that there's no cloaking effect at all. The light your eyes would detect has not passed through that array of lenses, so all you would see is someone placing an object between

two lenses, and it would not disappear. It would just be right there, so there'd be nothing special from your perspective. There are similar projects that use cameras, mirrors, and displays to create this type of illusion, but again they're dependent upon your frame of reference and perspective. If you step outside that frame of reference and truth settles in, then you notice that the thing is not really invisible or transparent.

This is kind of like having a magician hide something behind a little curtain, and because you're looking at the curtain, you cannot see what's going on behind it. But if you were watching from the side of the magician, you can see how the trick was done, which is not much fun, but it does show that the optical illusion depends upon certain criteria to work, specifically where you are

looking from. In two thousand seventeen, Toyota applied for a patent titled Apparatuses and Methods for making an Object Appear Transparent. So was this a way to turn an entire car invisible allah James Bond's Aston Martin v. Twelve Vanquished and Die Another Day. Not quite. This is a system meant to help the driver of the car. It's not meant

for people outside the vehicle. Toyota's approach is a method to make certain features inside the car appear transparent to the driver, so that the driver can have an unimpeded view of the environment around the car. Specifically, the objects that were meant to be turned transparent were the A pillars inside the vehicle. Now, the pillars in a car are the supports of a car's window area, sometimes also called the greenhouse. Pillars are divided up as A, B, C,

and if the vehicle's big enough, sometimes D pillars. The B pillars are sometimes called posts. Those are the ones that are on the side of the vehicle. Uh. The A pillars are the sections on either side of the windshield that support the windshield and connect to the top of the car in order to meet crash safety standards. Those pillars can be pretty wide to provide the necessary structural support, but that means they block some of your

view while you're driving. So it's that section of a car that separates the front windshield from your side mirror or your side window. Rather so that that poe, that pillar is what Toyota was thinking about, like, how can we make it so that you can see through that pillar and thus have a better view out that side of your vehicle, so that you really don't have an impeded view from the front all the way over to your side window. How do you get rid of that

gap from your vision. Well, according to the patent, Toyota's system redirects light using mirrors so that the light projects on the pillar itself, creating the illusion that the pillar is transparent and removing that gap from your visibility. And because it's a patent, anyone is free to look it over and read about the technology Toyota developed. So if you want to do it, if you want to read about some pretty complicated concepts and optics, I have the

patent number for you. It is a long one, so get ready. The patent application number is US two thousand, seventeen zero two two seven seven eight one a one. So if you put that into a patent search, you're gonna pull this up and you can read all about how Toyota proposes this technology be implemented. But what about a cloak more in line with the invisibility cloak in Harry Potter. In J. K. Rowling's books, characters make use of the invisibility cloak to snoop in on important exposition.

And in that world it all works via magic, which is great because there's no need to explain anything. It just works. But is there anything like that in the real world. Well it's not nearly so dramatic as that, but the U see San Diego Jacob's School of Engineering played host to a cool project that reminds me of

the invisibility cloak in Harry Potter. A research team published a study in a journal called Progress in Electromagnetics Research that detailed a cool technology they nicknamed a carpet cloak. And with this tech, you could put an object on a flat surface, like a table. You could then lay the carpet cloak on top of this object. Now, a normal piece of cloth would betray that something was in

fact underneath it. You would be able to see the cloth bunched up and folded over the contours of the object. But this new tech wouldn't appear to do that, assuming you could see in the microwave range. According to the senior author of the study, bubbacar Conte, the carpet would create the illusion that it was laying flat on the table as if nothing were under it at all, and it used taflon and ceramics as dielectrics, a dielectric is a material that acts as a poor conductor or an insulator.

When you subject a dielectric to an electric field, very little current will flow in the material because there's no free electrons in the material to have current flowing. However, the material does become electrically polarized. The positive charges of the of the dielectric are attracted to the electric field and the negative charges in the dielectric are repulsed by it, and this separation of charge it's minute, but it reduces

the electric field within the dielectric anyway. The combination of teflon and ceramics scatter the microwaves to mimic a reflection pattern of a flat surface. So while there are actual deformations in this carpet cloak, the way the material scatters electromagnetic radiation makes it appear as if it is flat. So in reality it is folded around an object, but from a microwave perspective, it's as if it's a perfectly

flat piece of cloth. If you were to reach out and touch the material, you would actually feel the spots where it covered the object. But again, this was entirely on the microwave scale, not visible light, so to our eyes everything would seem exactly the same. Microwaves have a wavelength of about ten to the minus two meters, meaning they are on the centimeter scale, but visible light has wavelengths closer to point five times ten to the minus

six meters. I mean, they have a much smaller wavelength and therefore a higher frequency. Designing material that can scatter visible light requires more precision than something for microwaves. The cloak carpet falls into a general category of stuff we call meta materials, and those are super cool. So let's talk about what they are and how they work right after we take this break to thank our sponsor. So

what is a meta material? Well, they're different kinds, but two of the defining features are that one this is stuff that's made by humans, so you do not find meta materials in nature, and two, they tend to have properties that are either uncommon or un heard of in nature. So it's stuff we make what acts differently than stuff

we encounter in the natural world. Menty materials get their unique properties not just from the type of stuff they are made from, but also their actual physical structure, which makes them different from natural elements. So, for example, if you were to go panning for gold and you found a few gold nuggets, pure gold nuggets in a stream, Those pure gold nuggets would have the same general properties as say, a bar of pure gold or a piece

of pure gold jewelry. They would all be in different shapes and sizes, but their properties would remain exactly the same. It would still behave as gold, But a meta materials properties depend at least partly on the structure of the meta material itself. And by structure, i'm talking about repeated patterns that are all the way down to the nano scale,

or maybe even further down to the atomic scale. A nanometer is one billionth of a meter, and a human hair can average about one hundred thousand nanometers in diameter. So we are talking super small here, so small that a light microscope will be of no help to you if you want to look at this stuff, because the light wavelengths are actually bigger than the things you're trying

to look at. To bend electromagnetic radiation, you have to create these tiny, repeating patterns of structures inside this material. What's more, the structures need to be at a scale that's smaller than the length of the wavelength of electromagnetic radiation that you plan to manipulate. Now, there are a few ways that meta materials could manipulate electromagnetic radiation. One way is to create what is called left handed material

and as a left hander, I really appreciate this. Left handedness. When it comes to meto materials refers to two attributes, permitivity and permeability. Permitivity refers to the resistance that is encountered when an electric field interacts with this material. Permeability refers to the degree of magnetization within a material that's interacting with a magnetic field. If both the permitivity and the permeability of a substance is negative, that substance is

said to be left handed. Now, you can also have single negative meta materials, in which either the permitivity or the permeability is negative, but not both. Most stuff in nature, however, falls into double positive category, meaning both permitivity and permeability is positive. So meta materials fly in the face of nature. Take that, nature, I think you're so big. The carpet cloak is an example of meta materials that have the capability of bending microwaves around them as if the material

wasn't there. Though, as I mentioned earlier, right now scientists are working on wavelengths that are in that centimeter range or maybe as small as near infrared, which is still a much larger wavelength than visible light. They have not managed anything that would work in the visible range. In order to do that, they would have to build these repeated structured patterns at a very tiny scale. We're talking

like ten to twenty nanometers max. Developing that technique will be a challenge, and making enough of it to say code a jet might be outside the realm of possibility, And that phrase visible range is also important. It might be really tricky or maybe even impossible to design a meta material that can work across the entire visible spectrum of light wavelengths. We might be able to create materials that allow certain types of light to bend around it

while it still reflects other wavelengths. Such a material might, let's say, let red light pass right through it, but reflect all of the wavelengths of light. Now, that would be a pretty cool way to create a gel for a theater light I imagine, But it doesn't turn something completely invisible. It just means that you would have no red reflected back from that particular object. All the stuff you would see would not have any red in it, and all the red light would go on to the

other side. In a similar vein, you wouldn't be able to manipulate all wavelengths of electromagnetic radiation with a basic meta material. So while you could conceivably create a material that could allow visible light to bend around it, other types of electromagnetic radiation might remain unaffected, meaning you would still be able to quote unquote see the object using a different wavelength, like radar. So you might have an invisible jet like Wonder Woman, but it will still show

up on people's sensors. Meta materials aren't necessarily restricted to electromagnetic wave manipulation. However, there are scientists and engineers making meta materials that will interact with other types of waves, including physical waves like sound, owned waves, or waves in the ocean. Imagine a material that can redirect sound waves with incredible efficiency. You could design a space that amplifies

or nullifies sound. Or imagine a building made out of meta materials that can redirect seismic waves so it's as if these seismic waves just passed through the building. So if an earthquake were shaking everything around the building, the waves would actually move through the physical structure as if nothing were there at all. And it could remain unaffected by the earthquake. Much of the work and meta materials

does not have the goal of creating magically invisible matter. Rather, it's to manipulate electromagnetic radiation to make technologies more effective. For example, imagine solar cells that are made from materials that capture light with greater efficiency, so we lose less of the Sun's energy due to reflections off the solar cell. Or imagine radio receivers that are more effective at picking up week signals due to their physical structure or going

to the physical wave examples. Imagine a perfectly soundproofed room that absorbs all sound from the outside, which I would love to have so that every time someone walks in or out of the door that's next to the studio, it doesn't interrupt me and I don't have to say things all over again. Maybe I have some personal stake in this now. I recently read a report about a team that made a meta material that's effective with sound waves,

and this research comes out of Pennsylvania State University. Researcher Amanda D. Hanford used meta materials to bend sound waves around an object as if the object were not there, and if you were to blast this object with sound waves, the sound waves would continue onward as if there was nothing in their way, so you wouldn't get any echoes back from that object. And Hanford's meta material works under water.

That means such a material could shield an object from sonar. SONAR, which was originally an acronym that stood for Sound Navigation and ranging, uses sound as an echo location strategy. It's essentially the sound equivalent to radar. Most radio waves do not work so well underwater, but sonar is a different story. Sound travels very well underwater, so for certain applications, such as the navigation equipment aboard a submarine, sonar is incredibly useful.

But if you can shield objects from sonar, then there's no way to know that there's an object there. A submarine's sonar equipment wouldn't detect this object, potentially resulting in a crash. Or you could conceivably use meta materials to hide a full submarine, creating a Red October sort of situation, which is pretty cool. Now, when we ever have a cloaking device like the ones in science fiction films, I'm

not gonna say it will never happen. Science and technology can do amazing things, and it may be that we solve this challenge using those tools, but it's going to take some time if it is possible. In the meantime, will probably see some really amazing applications of these various strategies for stuff that is just as cool as turning a cling on bird of prey invisible. And that wraps up this discussion about cloaking devices. I hope you enjoyed it.

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