How to Build a Real Lightsaber

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Hey, Welcome to Sign Stuff production of iHeartRadio. I'm Hoorge Champ and today we're answering the question could we build a real lightsaber? A long long time ago in a galaxy that's here. Star Wars became one of the most popular movie and television franchises ever created, and arguably one of the coolest things about it are the glowing sorts of light that the characters used to fight with. I mean, what self respecting geek hasn't dreamed of holding one in

Who are big Star Wars.

Nerdsally one of them prefers Star Trek, but I won't tell you who it is. You'll have to use the force to figure it out. So get ready to go to warp speed, because this is the podcast you are looking for. As we answer the question possible a real lightsaber is hm? I promise it's not a trap. Hey everyone, Okay, that was a lot of Star Wars puns, but don't worry. There's a lot of real cool signs in this episode. We're gonna be talking about plasmas, laser needles, and the

I'm ANDREWS.

Ricker.

I am a PhD plasma physicist who spent my entire career at the Princeton Plasma Physics Laboratory, and I just love my job.

Archro Domingas. I am a PFC plasma physicist as well.

Amazing, And are you fans of Star Wars? Yes? Worse of course you're physicist. Of course.

Wait was ar truly even born when Star Wars came out?

Not the first one, see see, I was a teenager.

I have to say I am a fan, but none of us are as much fans as my eight year old son. He is obsessed with it.

Wow, you're lucky. I can't get my kids to watch any of it.

Oh, I can't get him not to watch.

That original trilogy or the second.

So I am very proud to say that he's watched all of them, but always gravitates back to four or five.

And oh, yeah, I can see why you're proud, Yes, third proud. All right, Well, I guess the question is what do you think about Lightsabers when you first saw that movie?

So I saw it in the theaters, and I'm vague memories of just being blown away by these what looked like sword fights with I didn't know what they were at this time, lasers, plasmas. This was just way beyond my teenage self.

So I don't think I ever remember a time I didn't know about lights So they're just kind of a thing that existed and that when I was, you know, ten or something, I found out that wasn't real. So for me, it's just been like a part of life.

Okay. So there are a few concepts in physics that could potentially be used to make a real lightsaber, and one of them is plasma. Plasma is basically the fourth state of matter. There's solid, liquid, gas, and then there is plasma. If you heat up a solid, it melts and becomes a liquid. If you heat up a liquid,

So, first of.

All, what they did is beautiful. I mean, what a beautiful feat of engineering and electronics. It looks beautiful, it acts beutifully.

Yeah. So it's really very much like a blowtorch in which they have a directed jet of propane that has been.

Lit up, and the length is related to how fast it's coming out, and as it comes out, it's cooling down, and at some point it cools down to the point where it goes out at the tip right it stops combining. That's what I think is happening. And I would argue that the hottest part is the plasma, but the edges are propably just spot gas.

So the lightsaber they built on YouTube is basically just the blowtorch or not that different from a lighter or a flame. And I should mention that this video with

That's probably a mixture of some plasma hot gas.

It's a mix of it.

It has some plasma in it, which leads to the light emitted because plasma has light emissions. But I also think part of it is that the black body radiation from the little pieces of stuff that burnout. So it's a mix of several sources of light.

Yes, okay, this is interesting because it gets into the physics of flames or fire. A flame like from a candle or a blowtorch can't have plasma in it, but not necessarily. Here's what happens. Fire happens because of combustion, which is a chemical reaction. That reaction creates energy, which heats up what's left after the reaction, and that glows just from being hot, kind of like a traditional light bulb or a piece of metal that glows when it's hot.

But I think it goes back to the question like, is a lightsaber by definition? Does it have to be a plasma? I don't know what the answer to that is, right, Can a lightsaber be a very hot blowtorch?

Maybe? I think it would.

Still count as a lightsaber. If somebody comes up to me and does a flip and pulls that out and confronts.

Me, I will run away because that, to me is a weapon made out of plasma.

You'd be like, I got a bad feeling about this.

Yes, exactly.

I think the argument is what is a lightsaber? And since this was inspired by Star Wars, I think we have to take what was in the movie as a definition of what a lightsaber is, which means you have to be able to fight with it. As they hit. It's as if two solid pieces of metal or something are up against each other and you have to have that battle. Where now is who's that the more arm strength?

I think that is Andrew's strongest argument is when and they have the fight scenes, you can stop a lightsaber with another lightsaber. I very much doubt that you can stop one of these that they made in twenty twenty with another one of these. I think they would just go through one another, And that I think is the strongest argument against it being a lightsaber.

Okay, sorry, Hacksmith Industries. The physicists here from the Princeton Plasma Physics Laboratory don't think what you've made is quite a real lightsaber. If you cross to flames or to blow torches, the flames are just gonna go through each other, or the flow of the hot gases are gonna mix in the form. They're not gonna collide and feel solid like in the movies. So now the question is is

Way we do it is with magnets. All right.

Here, doctor Zuicker has an idea for maybe how to make a real plasma lightsaber work, and it has to do with how scientists are trying to.

Make a fusion reactor.

A future reactor is basically the idea that you could create a miniature sun here on Earth. Inside of our Sun, there's incredible pressure at the very core of it, and there's plasma there, and the combination of those two things makes atoms fuse together. Well, here on Earth, scientists are working on making a plasma like that, and the way they hold that plasma together is using essentially a magnetic bottle that holds a blob of plasma together.

We're trying to eventually make a miniature star like the Sun, but we use powerful magnets to keep the plasma where we want it to be and get it hotter and hotter and hotter. So if a lightsaber were to have a confining magnetic field in a tube that would keep the plasma inside that tube. Number one, you get the shape, Okay, okay, But what's interesting is that if two lightsabers, both with

What doctor Zicker is proposing here is that maybe a lightsaber could be essentially a magnetic bottle. The hilt of the lightsaber could somehow form a magnetic field that contains a blob of plasma in the shape of a long tube, and it would be hot enough to glow and cut through things. And also when you hit another lightsaber, the magnetic fields would repel each other, giving you that feeling

Exactly.

We have so many problems with the.

Why is that nonsense?

What Andrew is describing is literally what we call a magnetic mirror, which is a cylinder of concentric rings that are electromagnets with a very strong one at both ends. So you've got to have some floating solid electromagnets all around the platform.

To create those kinds of magnetic fields, you need to surround that whole area with magnets, which would defeat the purpose of it being like a freestanding lightsaber.

I mean, my entire thing was based upon magical magnetic fields.

Okay, we tried, but here's the thing about plot. A plasma is basically like a gas. It's not solid, and it wants to expand and spread out like a gas. And the only way to contain a plasma is but either something solid or you have to surround it with magnets, which would ruin the idea of a lightsaber. So it doesn't seem possible to make a real lightsaber using plasma.

Us like here is online.

It's a pleasure to be here.

Both Fasy and myself are really really huge Star Wars fans born in the seventies. I mean Star Wars shape my childhood. Really, I've watched the movie so many times, like you then by heart, and I don't know. There's something about like the Jedi Knight and the lightsaber that is just I don't know, there's something to it, right, Just the sound of it makes my hair rise on the.

Amazing I guess as a physicist, when you see the movies, what do you think a lightsaber is?

Actually it's funny because I think if you ask any Star Wars fan, many of them will say that it's like a plasma saber. They would say it's made of plasma. I don't know what is the origin of the idea, the exact origin, but I don't know. I'm a purist. I like the original Star Wars trilogy, and you have no mention of plasma anywhere there. We're called them lightsabers.

Right, that's true. They're not called plasma sabs.

They're not called planas there. They're gonna light sabers, right. Stick to that exactly for me. A concentration of light energy that's concentrated in some shape that looks like a saber.

So they need to be made out of light somehow.

Exactly, and that stopped at some point, it stops like the blade is finite.

Oh okay, all right, Like I said, doctors Gagnon and Filian Grudeaux think they found a way to make a lightsaber actually out of light. But to do that, the design has to overcome two big challenges that people say makes it impossible to do that. Okay, Now, Star Wars is fiction, we think.

All of the future. Actually it happened a long time ago in the galaxy far far away. It already happened.

That's right, that's true. Good point, that's right. Well, we can only hope. But people say that lightsabers are impossible. What do you think people say lightsabers are impossible to be made out of light?

Yeah.

One of the reasons for one thing is out do you stop light after like a meter of propagation? You know, when you have a leaser. Think about the leaser pointer for example. The laser pointer will go on forever until it hits something or it's reflected on something, so light naturally does not stop by itself. One thing that it's just for a lightsaber that would be hard to do or hard to implement physically.

Okay, So the first challenge in making a lightsaber out of light is that light, when it's admitted, tends to want to keep going on forever. So how do you make a sword out of light that has a finite length? And the second problem, it's the same problem we had with the plasma lightsaber, which is how do you make the lightsaber feel solid?

You've seen the movies when the two blades clash together, they actually feel solid. But of course that's not what you would expect from light, right.

Right, Like if I cross the flashlights.

You can just do it and you see that they're just like whoa go through each other.

And that's because light doesn't necessarily interact with itself exactly, That's exactly it.

So if you think that light is made of photons, let's say, so little particles of light, they are electrically neutral, so it means that they don't have any electromagnetic interaction between them. They don't interact in any other way in terms of like other forces, like nuclear forces for instance.

So to a photon, another photon is just invisible.

Yes, in some sense classically clastically, of.

Course, they have no way that we traditionally understand that they can interact with each other exactly. So those are the two reasons people say making a lightsaber out of light is impossible. One how do you make it finite so the light beam doesn't go on forever? And two how do you make light feel solid? Well, it turns out there is a way to get around both of those problems, and no, it does not involve using the force. We'll start with making a finite beam of light.

According to doctors.

Canon and Fillian Cordeaux, you can do it with something called a needle of light. I've definitely done that as a kid, Like when you have a flashlight and you turn off the lights and you pretend that you're swinging a lightsaber around, but you're right that it keeps going on forever. Is that something that you think you have a solution.

For, Well, not the direct solution, but if you look at the scientific literature and the research done by any physicists, it's called a needle of lights and so it's a very particular electro magnetic fail configuration.

They are very hard.

To do in a laboratory, so you need very special mirrors to do them, but they have the property that when this light is focused, the energy will be in the form of a long cylinder.

WHOA, I don't think I was expecting this. Is there a process in physics that might allow that to concentrate light in a short beam like that?

Yes?

Yes, yeah, yes, yes, okay. Can you describe this phenomenon? What is it?

How does it work? I imagine like you're sending a light beam that would be cylindrical, so it would be more like an annular type of beam. It means that instead of having like a cylinder that is filled with light, you would only have like the outskirt of it, like a ring.

Oh I see, Instead of a solid beam of light, you're shooting out a ring of light.

Yes, exactly.

Then you send it on. Imagine in the hilt of the lightsaber there will be a mirror at the back, and then you send towards that mirror, and then when it's reflected like at the focus of the mirror, it would look like a needle. And it's what I said. It's related to the fact that you have like many beams of light. When it reflects to the focus, some of those beams will kind of interfere with each other. It will cancel in many places, but it would add up at the focus.

And so that gives you a little light needle.

Yep, exactly.

Okay, the details of this are a little hard to explain, but it is something that physicists that specialize in optics

Yes, yes, so the energy of the beam would be concentrated in that tiny needle.

And not anywhere else.

So there would be much more energy conceptor along the needle than the rest.

But the light would keep going after the needle, it just wouldn't be focused.

Yeah, exactly, so it would be diffuse. After the needles you want, it will still propagate, but the energy will go down drastically, so it would look like a small light saber.

Uh huh. We would see like an actual seat of glowing beam like a lightsaber.

Well, yeap.

Actually, it depends a little bit on the medium. So let's say you would open the slight sliaber in air. She could create a plasma and the plasma could start to emit light.

I see. The light will then cause the air molecules to glow.

Basically, yes, yeah, exactly.

Okay, yeah, we did end up with plasma. But here the plasma is only the reason we see the lightsaber. The actual sword is technically made of light. So does that solve the lightsaber problem?

Kind of? There is one little problem.

And I think you can have a slender that's about fifty thousand times the wavelength of your user. And so that's say in the optical regime, and for example, blue fits around five hundred danometers, so time sixty thousand, that will be the length of this needle of light.

So we're talking about probably a millimeter. Yeah, it has limitations, right, So it seems that they are able to do it for about the size of one millimeter.

What the physicists are saying is that this needle of light phenomenon depends on the wavelength of the light you're using, and so far, the longest needle scientists have been able to make is about one millimeter long. In other words, we can make a life lightsaber out of light, but at least so far, it would only be one millimeter long. Now, is it possible to make it longer?

The answer is maybe.

Star Wars would be a lot less exciting if it was called the light needle. Could I make it longer by using a longer wavelength of light?

I think so?

Oh oh, now we're getting somewhere like.

An infrared faber.

Oh yeah, I think it could work infrared. If so, it would be red.

I don't know.

The first lightsaber would be a sift lightsaber. It's harder to make a good guy lightsaber, as I think that's kind of one of the lessons of Star Wars is that fear and anger are easier. Exactly, that's the bath of the dark. The Bath of the Dark set is easier yep, more plausible, more physically practical. Yeah, okay, so that's where we stand on the problem of making a finite beam of pure light. It's possible to make a needle of light, but so far they are really short.

Hey, welcome back.

We're talking about whether we can build a real lightsaber when that has a beam of light that stops at a certain length, that can cut through things, and crucially that you can spar with. In the movies when the Jedi and the Cyth cross swords, they hit each other and they feel solid. But as we learn, making a lightsaber out of a plasma blowtorch meets all the requirements except the last one, and so it turned to lasers.

So that was more the main focus of our paper. So the idea is this. So we just said that if you have two photons, they cannot interact directly with each other, but it doesn't mean that they cannot interact indirectly. Okay, this is a huge feel of research. It's called nonlinear optics. Oh, so imagine that. Now you would have let's say a

Okay, here's the scenario that the physicists are imagining. Normally, photons of light just ignore each other. Light is electrically neutral and it has no mass, So photons can't push or pull or bump into each other. If you take two flashlights and you across the beams. The beams of light just keep going straight. I mean, who hasn't done that as a kid. But there is a way for photons to interact indirectly with each other. Photon can interact

Yeah, okay, it happens mostly when the intensity is very large.

Yeah.

Oh, it has to be powerful enough to feel that effect exactly. So it has to be.

Powerful enough to deform the medium. So we send the language to polarize it so it pulls the electron in one direction, let's say, more than the other, so that it changes and if another sluton comes in, it's propaggation will be modified.

So you could imagine this working in air as the medium the lightsabers are in. But doctor Gannon and doctor Phillian Grdeaux are envisioning something more universal. A lightsaber that could work anywhere, even space.

The next step is, but we don't want to rely on the medium for that thing to work. We wanted to work in vacuum, like in the movie in space. Look like in the movie, if you want to turn on your lightsaber on your spaceship and use it, you can't.

Well, technically, I think every time you see a lightsaber in Star Wars, they're in air.

That's true.

True.

We don't want it to depend on which atmosphere of the planet in your room.

Yeah, okay, okay, got it, got it, all right, So let's try to make a lightsaber that works in a vacuum. Go ahead.

So the question is if it is vacuum, then you might say, like, it's completely empty, right, so there are no media, right, so there cannot be any indirect interact between the photons. What but it can, that's the thing. So if you're talking about the quantum vacuum, quantum vacuum is full of stuff.

Yeah.

Yes.

As it turns out, empty space is not really empty. It has something that physicists called the quantum vacuum energy. The theory is that empty space actually has something like a background buzz or a low level of energy that predisposes it to create particles out of nothing.

So it's full of what we call virtual particles.

I see, empty space is not really empty. It has kind of like a bubbling frost of quantum particles that come into existence and disappear.

Right according to the theory, Yeah, according to what like the best theories that we have right now to describe the microscopic world. They come into existence, but they go back to the vacuum in such a short time that we can't even measure them. That's why they are called virtual particles. I see.

But light as it goes through a vacuum, does interact with virtual quantum particles.

Yes, it does, exactly.

And actually one effect that it's supposed to happen when you reach a very very high intensity is that you can actually create matter directly from light. So light would interact with this particle and it would pull them, and then you can start generate electron pulls it from pairs directly from light.

I see. Okay, Okay, So let's say I have a laser super intense, I shoot it. It's interacting with the quantum vacuum, and is the idea then that it's that trail that it leaves. That interaction would then affect the other lightsaber. Is that where we're going, Yeah, exactly.

Yeah, So imagine you would have like two lightsabers at ninety degrees with each other, and then they clash like in a fight for instance, and then there is an interaction region between the two lightsabers. And then so imagine some of those photons come from one of the hilts, and then because of this indirect interaction between the photons through the vacuum, then some of them might reflect towards

Oh, you would feel a force.

You would feel a force in the hilt.

Yes, So that's kind of the idea. If you have two of these laser swords, when they hit each other, they would interact with the quantum vacuum energy, which would cause photons to be reflected from one sort to the other, and then those photons would make you feel a force through what's called radiation pressure. Basically, when photons hit something, they actually give whatever they're hitting some momentum, pushing it back.

Yep.

Actually in the film called that quantum reflection. So it's really a quantum effect that induces these direction between photons and that reflect them.

Back towards the hill.

Then that's what we think would make it feel. I don't know if it will feel solid, but you will feel something.

We kind of analyze how you would feel it, and it will feel very different than just like hitting something solid, that's for sure.

I see. It won't feel like you're clashing swords, but you'll definitely feel something that kicks you back.

Oh yeah, something like that.

Yeah, all right, well I think we did it that. It's possible to make a real lightsaber sort of. You can't have a standing beam of light and yes, it's small, but as Yoda said, size matters not you can also cut through things, and you could technically make it feel solid or at least like it hit something. Does that mean we should all grow a ponytail and become pata ones.

No, well, hey, let's say let's put it in fury. But one of the things that has been pointed out is that, well, you need an energy source, right, and the energy source, of course, has to fit into the hilt of the lifesaver.

Leather batteries all work for this.

Yeah, it could not work so to have a significant effect to feel let's say a kickback on the other hilt, for instance, and it's ten to the twenty three watts.

So that's just a shy less than the output of the thought.

You take the entire sun's output. That's how much you need to feel a little kickback at this light saber through this effect, meaning your lightsaber would be as powerful as the sun. Yeah.

Almost.

These effects are weak.

Yeah, the effects are weak, so you need a lot just to get it.

So you need to put in a lot of soot on to see something or to feel something because.

The problem is so small.

Okay, yeah, this kickback the fact that might make the lightsaber feel solid depends on a quantum physics interaction that is very unlikely, and so you need a lot of photons to make it happen, which means your lightsaber needs to output the same amount of energy as the sun. But hey, as jin Urso said, rebellions are built on hope. Maybe there is a way to get that kind of energy. Okay, all right, Well I'm not the terror because I know kyber crystals are who knows how they work?

Right?

Maybe they have the power of a sun.

Oh yeah, people say that that's what also power the Death Star. So that's another of my calculation that I do. If one of my electromagnetic courses, I mean, it takes a lot of energy for that later beam, trust me.

Well, let's take it a step further. Guys, is a Kyberg crystal possible?

Well, I would like to know what is the Kyberg crystal?

Yeah.

In the article, we talk about electron positron bears recombination, which is probably one of the most efficient nichanism to generate energy.

So, as Fransos said, so the most efficient way would be to use antimatter when you annihilate let's say to an electron and a positron, all of it becomes energy.

I see, a positron is like an anti electron basically, right, Yeah, yes, exactly, So.

If you annihilate them, then you get like as much energy as you can coming from that mass. So that's probably the most efficient way. So I don't know if kyber crystals are similar, for there be rate on a different level than that, but as far as we know, the best would be antimatter and aliation.

This could be the subject of a whole other episode, but antimatter is regular matter that has its quantum number flipped. So if you take an electron and you flip its charge, you get a positron, which is an anti electron. And if you mix a matter particle with its antimatter version, they annihilate and give out a whole bunch of energy. Now, could you power a lightsaber with that, Yes, but you'd need a lot of it.

So even that, you would still need like one hundred million kilograms of that into your hilt.

One hundred kilograms of matter and antimatter one hundred million kilogram Yeah, being annihilated at a time.

The time to power it for about a minute.

That's a lot, lot. That's a lot, a lot.

It would squeeze all of that into the hilt. Would be so similiar to like a white dwarf and the neutron star.

Uh.

Even if you take that much matter and antimatter squeeze it down to a hilt, you'd be basically carrying a sun with you.

Yeah, you can carry it. Interesting, I mean I think you would need the pores to actually life.

Oh, there you go. That's how it works.

Why they need the far Yeah, the power their lightsabers.

Yeah, this is not looking so good. But the real kicker is that shooting light actually.

Creates a kickback. Like if you turn on a.

Flashlight, the flashlight actually gets pushed back, kind of like give you fire a gun.

The effect is super small.

Because light has very little momentum, so you don't actually feel it with a flashlight, but at the intensities of light we're talking about in our lightsaber, it would be a lot.

When you turn your lightsaber on, you'll have some kind of recoiled effects like a trust and the estimated that the trust.

There's like ten to the seven saturn five rockets, like put like strap them all on together and when you just power it on. That's what you would.

Feel ten to the seven Saturn five rockets. Wait, if I have a laser four, that's how much when I turn it on, that light would actually push me back?

Yes, exactly.

Wait Wait guys, I feel like you're saying that the thing that disqualifies Star Wars as fiction is not lightsabers. It's not Kyper crystals. It's Newton's second law of motion.

Yeah, you're probably right.

Everything else is possible, but Neaton's second law says no, that's all fiction.

Yes, that's a very nice way to summarize it.

You're right, all right, Well, to summarize our space opera to a galaxy for are far away. It's definitely possible to build a real lightsaber that glows in a beam and can cut through metal. I mean, the folks on YouTube did that, but it doesn't feel solid. To make a lightsaber that feels solid, you could make it out of lasers and have it interact with the quantum vacuum energy.

I don't know.

It's so like it looks like an efficient weapon, a noble weapon of a more civilized.

Age, the idea of combining a sword, which as a kid, swords are cool, but now it's a sword made out of like lasers. Yeah. Yeah, that did Star Wars influence either of you a little bit and your choice to become physicists.

Maybe at some deep level. I mean I always been interested with sci fi in general. So Star Wars, of course, as I said, shape my childhood.

It makes people wonder what's possible?

Yes, yeah, exactly, and personally for me, just the fact that you know they were in space, and so I think this movie brought interests to astrol physics, a rockets, things like that. So it's not direct Star Wars, but it's via space that brought me to physics.

Thanks for joining us, See you next time, and hey, may the Force be with you. Music and Time Effects Firm Fix the Bay credit to Louise whom anoyed. You've been listening to Science Stuff production of iHeartRadio, written and produced by Me or Hm candidate by Rose Seguda, executive producer Jerry Rowland, and audience enger and mixer Ksey Peckram. And you can follow me on social media. Just search for PhD Comics and the name of your favorite platform.