Wednesday, December 30, 2015

How does a lightsaber work? Here is my best guess.

A lightsaber works by emitting a stream of magnetic monopoles. Magnetic monopoles are heavy particles that source magnetic fields. They are so-far undiscovered but many physicists believe they are real due to theoretical arguments. For string theorist Joe Polchinski, for example, “the existence of magnetic monopoles seems like one of the safest bets that one can make about physics not yet seen.” Magnetic monopoles are so heavy however that they cannot be produced by any known processes in the universe – a minor technological complication that I will come back to below.

Depending on the speed at which the monopoles are emitted, they will either escape or return back to the saber’s hilt which has the opposite magnetic charge. You could of course just blast your opponent with the monopoles, but that would be rather boring. The point of a lightsaber isn’t to merely kill your enemies, but to kill them with style.

So you are emitting this stream of monopoles. Since the hilt has the opposing magnetic charge they pull after them magnetic force lines. Next you eject some electrically charged particles – electrons or ions – into this field with an initial angular velocity. These will circle in spirals around the magnetic field and, due to the circular motion, they will emit synchroton radiation, which is why you can see the blade.

Due to the emission of light and the occasional collision with air molecules, the electrically charged particles slow down and eventually escape the magnetic field. That doesn’t sound really healthy, so you might want to make sure that their kinetic energy isn’t too high. To then still get an emission spectrum with a significant contribution in the visible range, you need a huge magnetic field. Which can’t really be healthy either, but at least it decays inversely proportional to the distance from the blade.

Letting the monopoles escape has the advantage that you don’t have to devise a complicated mechanism to make sure they actually return back to the hilt. It has the disadvantage though that one fighter’s monopoles can be sucked up by the other’s saber if that has opposite charge. Can the blades pass through each other? Well, if they both have the same charges, they repel. You couldn’t easily pass them through each other, but they would probably distort each other to some extent. How much depends on the strength of the magnetic field that keeps the electrons caught.

Finally, there is the question how to produce the magnetic monopoles to begin with. For this, you need a pocket-sized accelerator that generates collision energies at the Planck scale. The most commonly used method for this is to use a Kyber crystal. This also means that you need to know string theory to accurately calculate how a lightsaber operates. May the Force be with you.

[For more speculation, see also Is a Real Lightsaber Possible? by Don Lincoln.]


Brian Clegg said...

I think you miss the point, Sabine. Star Wars isn't real science fiction, it's a fairy story, using SF tropes. Jedi are magicians, and a lightsaber is a twinkly magic sword. No more science required.

The Universe said...

Polite cough. An electron has an electromagnetic field, not an electric field, so the phrase "electric charge" is something of a misnomer. So "magnetic charge" is a misguided concept. Along with magnetic monopoles.

Sabine Hossenfelder said...

An electron has a mass and thus a restframe in which its electric field is purely electric. Hence the electric charge is perfectly well defined.

Sabine Hossenfelder said...


As Arthur Clarke put it so aptly, "Any sufficiently advanced technology is indistinguishable from magic."

Bryan Dixon said...

"But it says LIGHT saber not magnetosaber"

"Yes, and?"

Hum Bug said...

It seems to me you're describing an antenna made out of magnetic monopoles. I.e. the oscillating magnetic field caused by the acceleration of the monopoles cause an oscillating electric field. So, just like an antenna, it will emit an electromagnetic wave and you wouldn't even really need the charged particles if the parameters are tweaked to produce visible light, right?

akidbelle said...

Why not a string?

(And by the way the electron also has a magnetic moment; inseparable from the electric field.)


kneemo said...


JimV said...

"Star Wars" is not science fiction by my definition because it makes no attempt to have any scientific plausibility. For example, the graphics for its spaceship chases were based on race cars skidding through turns around a race track. The script-writers thought "parsec" was a unit of time. There are many good science-fiction books upon which good movies could have been based using the same resources.

That doesn't mean any points are missed by experts who explain how implausible Star Wars imaginary devices are, even giving them every benefit of the doubt involving the remotest possibilities.

I hope someone makes a video splicing Harrison Ford as Indiana Jones facing a Star Wars Storm Trooper who has a "light saber". Ford draws his gun, shoots the Storm Trooper, then sneers, "The fool brought a light saber to a gun fight." (My point being, in case it is missed, that investing magical technology in a short-range weapon is another idiocy on the part of the Star Wars creators.)

And yet people flock to give their money to see such dross. I must be missing something.

Uncle Al said...

Consider a terminated bundle of coaxial paired emitters, one space-like and one time-like. Spacetime is rent asunder as the sheaf of coaxial coherent beams mixes. Like trimeric ketone peroxide explosives, entropy does the heavy lifting. Propagation length is limited by growing decoherence.

The bundled coaxial emitter element is an ambient temperature exciton superconductor Kyber crystal, polished face normal to propagation re ulexite. It is ordered-excreted by midi-chlorian larvae re coral. Dreamland gel spun the first synthetic ordered bundle milligram of
[-C(Ar)=(Ar)C-]n is also [=(Ar)C-C(Ar)=]n

at 46.200278 -122.186667, 18 May 1980, 0032 UTC. "Qualified success"

Lucy M said...

"Brian Clegg said... I think you miss the point, Sabine. Star Wars isn't real science fiction, it's a fairy story, using SF tropes. Jedi are magicians, and a lightsaber is a twinkly magic sword. No more science required."

hey what episode is that ?

Lucy M said...

Sabine says 'As Arthur Clarke put it so aptly, "Any sufficiently advanced technology is indistinguishable from magic.

a brilliant man in a time of multiverse ignorance.

The Universe said...

Sabine, electric charge isn't "perfectly well defined". If you're motionless with respect to an electron you might claim it has an electric field. But if you move past it, you might then claim it has a magnetic field too. But you didn't create a magnetic field for that electron just because you moved. Instead it has an electromagnetic field.

Sabine Hossenfelder said...


Right. What I said was, to repeat it, the electron has a restframe which is a preferred frame. It is uniquely defined and in this frame it doesn't have a magnetic field component (leaving aside the magnetic moment which is due to the electron not being a point). Besides this, even if you move past the electron, the magnetic field doesn't have a source. Why don't you do some reading about magnetic monopoles first and then come back before claiming that I am the one who is wrong. Best,


Nick M. said...

Uncle Al said,

"Consider a terminated bundle of coaxial paired emitters, one space-like and one time-like. Spacetime is rent asunder as the sheaf of coaxial coherent beams mixes."

Hi Uncle Al,

Is this related to the reason why, in the movie Ghost Busters, it was considered very dangerous for the 'busters' to "mix the streams"?


Shawn Halayka said...

Star Wars spoiler:

In Star Wars VII: The Force Awakens, the bad guy seems to have a sword made from electricity. Sounds like it, looks like it. Not your run of the mill light sabre.

Uncle Al said...

@Nick M,
As you know, Ghostbusters had a jolly romp with Standards & Practices (the censors). Urban Dictionary: crossing swords (NSFW). One wonders why Han Solo did not whip out a Smith & Wesson Mk II Hand Ejector .455 Eley caliber to demonstrate a fundamental boundary condition of lightsabers. First, business:
Magnetic monopoles symmetrize Maxwell's equations.
When you care to send the very best.
Glock - it's only the messenger.
0.48 "Knock, knock."


Andrew Foland said...

Light sabers are gram-scale strangelet rods.

Suppose you could create a meter-long rod of strangelet matter hundreds of of femtometers across. Typically they are themselves charged (allowing electronic manipulation to extend or retract the rope into a coil, sort of like protein folding), surrounded by a plasma. (Hence the glow.)

Such a coil would be effectively indestructible in contact with normal matter (shearing through a solid state lattice, eating up its nuclei).

Fernando said...

Wouldn't it be easier to make a gluons saber?

Paul Walker said...

I enjoyed your article , Sabine. Nice, made me smile.
I feel Nick M is on track, now Jim V, hire the movie "Bedknobs and Broomsticks", its Ms Price would advise you about the "Age of not believing", Uncle Al, don't you go rending usunder our Universes fabric, you leave holes in the air and fairies fall through!
Call it magic if you like, Magic is the name for a trick we don't know the secret to but as to "How does it work", well by the power of the force of course,
They are used by Jedi and Sith Lords only, as they of course can focus the mind to control matter, transcending our reality with a "force"as yet discovered.
How does the indian rope trick work? Hypnosis? What moves the glass at a seance? How does a bird fly? When you can snatch this pebble from my hand , Grasshopper, it is time to leave....but look for answers in the real world of the paranormal, investigate Dr John Dee, Sir Oliver Lodge, Madame Blatavsky.....
First , sadly, Spoiler alert, yes they are a movie special effect, sleight of hand of a sort and it works by "seeing is believing".Enjoy the movie as entertainment.Consider it a fresh new chapter to a completed trilogy, possible with an unanswered question to be answered in the next movie in a lucrative way.
But HOW could it work is lots more fun to ponder, in a CSI way, a quest! here is an engineering and physics question to solve, new magic to learn,
Mans limited understanding at present calls such things magic, but visibly it is an energy "beam" like a laser/maser or particle beam, (plasma is better, hotter) but it is contained into a short "sword" stream, so is bound to a fixed length not projected...
color of beam is obviously spectrally related to quantum energy level of electron transition from shell to shell, investigate spectroscopy....color indicates element....
Now looking at the physical evidence,they clash together in fights with sparks so it must have substance of a sort, lets speculate it has a Kundalini powered 3 1/2 turns spiralling helix crystalline invisible substrate for physically containing the beam, a closed ended linear accelerator like a Hadron Collider has at the crash dummy end, the Dark energy in the handle of the lightsabre generates this antenna type carrier when switched on, with no Large Hadron collider loops needed for building the beam, because it is the future and they can do the science better
And the best fun is in "How do we make one", well, Grasshopper, we make a Klein bottle filled with Higgs Bosons, and imagine a "Thought form" applicator nozzle, and we just trust in it, with faith in the Force, and we see it in our mind as our own reality, and we visualise ourselves winning,
watch some children play Starwars, they know how. Believe. Be a fool and come and live in my paradoxical paradise, with John Coffee, Peter Pan and me.
Cynicism is only cheating yourself. Imagine a better world, and you will live in a better world, and have a nice day, Paul

Bhavay Tyagi said...

Sounds fascinating.
String theory hence gives rise to an elegant Universe.
And allows a new and wide range of possibilities for a better and stylish environment.

Alive Systems said...

Hi there,

A nice idea however I place more faith in the newly discovered process of "solidifying" light by locking individual photons together so that they become like a solid object. This way we could obtain a solid light blade though it could be not a hot but a cold blade.

More here:

Alternatively, we may think of a device, which could be transforming pure light into matter by production of so called Breit–Wheeler pair (γγ′ right arrow e+e−). This process is predicted by quantum electrodynamics. If we could manage to produce such matter from light generated by e.g. a "Kyber crystal", we would not need a lot of energy to power the saber and we could tune the device to produce all kinds of blades, adequately to the conditions we would need to use them in.

More here:

May the Force be with you


eternalinquisitor said...

Dear Sabine,
How does your model support the absolute rigidness of the light-saber, especially against metal objects? Further, given it is a particle stream, with one source-end, it should not be a finite column of constant or decreasing radius [Ep. IV-VI sabers were kind of conic, but Ep. I-III and Ep. VII ones are cylindrical.]

Phillip Helbig said...

The sound made when two light sabers clash is a sample of a bridge suspension cable being hit by a hammer.

My wife and I saw the latest James Bond film last night. In the cinema, there was a sign which pointed out that, in order that all visitors might enjoy the film, Star Wars fans should keep their light sabers switched off during the screening.

I don't know what is more fantastic: the Star Wars universe, or Bond showing up at dinner in a crease-free white tuxedo while on a train in the middle of the desert.

Kaleberg said...

There is a place in this world for whimsy. There may even be a place for magnetic monopoles.

I think it was one of Dr. Who's writers who had him say: "Any magic sufficiently advanced is indistinguishable from technology." Star Wars definitely has its magic.