How a Light Saber Works | Hacker News Reader

How a Light Saber Works

dickgrune.com

182 pointsSiecje118 comments

I think basing it on light is a mistake. I much prefer the solid core construction idea, with either a thin layer of plasma and/or a highly excited core material.

I re-watched Star Wars Episode 1 recently, and, as soon as the first lightsaber showed up on screen, I felt like a kid again. The movie is still terrible, and should be excluded from the series[1]. But, there is just something about watching space samurai, with light-up swords, that made me spend the next three hours imagining how to build something like it.

[1] http://static.nomachetejuggling.com/machete_order.html

> I re-watched Star Wars Episode 1 recently

Were you watching it out of phase in hope the interference with your first watching would cancel it from your memory?

Common mistake - if it leaves your memory, the next time you see the cover you'll go back to the "Awesome, a new Star Wars movie!" mentality.

Or you stand there in disgust, wondering how the hell Oskar Schindler and Mark Renton found each other and why they haven't cut their hair in a long time ... and put it back on the shelf.

If only it had gone that way. Star Wars fans seem to be willing to give the benefit of the doubt.

False, that's constructive interference. GP wants destructive interference. My suggestion is to load up the audio in Audacity, apply the "Invert" effect, and listen to that on loop for a few nights' sleep.

Early in Episode 1, one of the Jedi stabs his light saber point-first into a big metal door. It sinks in effortlessly and in short order begins melting the door. It doesn't compress or blow up. So that's one thing this description gets wrong.

Also, why do lightsabers that touch not pass through one another?

Oh, and this theory is an amazing thought experiment!

This description says that there are physical glass filaments that they light travels through. So they hit against each other and can't pass through one another.

But the description says "beams from energy weapons hardly affect them and just pass through." But in the movies we see blaster shots being reflected by lightsabers.

IIRC in universe a lightsaber is essentially an infinte blaster shot trapped in a magnetic loop. The crystal tunes the magnetic loop, so blocking blaster shots is simple because the blaster on the "outside" bounces off the same field keeping the plasma "inside" and for the same reason you can have proper sword fights.

I forget if you can shoot a Jedi with a regular bullet but I'd imagine s/he could just dodge it regularly since blaster bolts travel significantly faster.

No, they're much slower. At 24 frames per second, you can watch a bolt from a blaster pistol fly across a room; even a tracer round from a low-velocity handgun would just be a streak. It's more in the range of a good fastball than a bullet.

Considering it has been shown that a lightsaber easily and nearly instantly cuts through most metals, apparently due to extreme heat, that regular bullets would likely not cause an issue.

The speed of the projectile is not an issue either, Jedi use a precognition-like ability to dodge or block blaster fire. That's why a group is required, to eliminate the possibility of them dodging and blocking.

Well, it depends on how thoroughly it dissipates the projectile. Turning a high-velocity slug into a high-velocity blob of superhot molten metal would certainly reduce its penetration, but you still wouldn't want it to hit you in the face.

Still, when lightsabers clash you never see them bending as the article claims they would.

You do see that in Spaceballs, though. Would be hilarious if Mel Brooks turned out to be more technically accurate than the original.

Because that would make for a terrible sword fight scene.

It is interesting to think how you would do battle though, it would basically be the first person / fastest to swing, likely killing both parties anyway.

If there's something lightsabers don't cut through - I think cortosis was mentioned in the KOTOR games - then it would make sense to have a small lightsabre on the tip of a staff of cortosis. (Or perhaps, more practically, a staff coated with cortosis, I don't know how heavy that stuff's meant to be.)

In any case! ^^; A light-spear. You'd be able to parry with the shaft and stab/slice the other person from beyond their reach.

It's not canon, but I remember reading one the expanded universe books that describes a Sith that had somehow created a lightsaber with an extended blade for some perceived advantages. I believe it added 12 to 24 inches to the overall length.

I can just imagine the spam the jedi got in their email inbox after that revelation.

I've just been wondering if a light saber is similar to an electrolaser [1], where you use a laser to ionize air and then send out an electric current through the plasma channel.

I could be wrong but wouldn't the power of the laser determine the length of the plasma channel?

[1] http://en.wikipedia.org/wiki/Electrolaser

Have you watched The Phantom Edit? It's a fairly decent Star Wars movie, set in the Old Republic.

I like Machete order, but if you're allowed to drop films from the series to improve it can't we go the whole hog and drop all of Episodes 1, 2 and 3?

Frankly I'm only leaving Jedi in there because it needs an ending...

I don't know where I first came across the concept of "fiction apologism"

heres a pretty good explanation:

http://99percentinvisible.org/episode/future-screens-are-mos...

but I feel like it is a wonderful under-appreciated art.

Three problems I see:

1) This lightsaber appears to allow blaster fire to pass through undeflected.

2) There is no discussion of how sabers parry each other instead of breaking.

3) It appears to have a "blunt" tip.

1 and 2 could possibly be explained as a Force-related effect. Vader has been seen to deflect blaster bolts with his bare palms, so we know that the Force is capable of doing this; perhaps something in the design of the lightsaber makes it much easier to perform this feat with the surface of the blade, or perhaps it even produces a field or resonance in the Force that deflects energies without conscious effort beyond that needed to power the saber. Vader's deflection power may be inspired by study of the saber itself.

This implies that a sufficiently powerful Force user could parry a lightsaber with their bare hands! However, given that the blaster-deflection trick appears to be quite difficult, saber-deflection may be possible in theory but beyond any Jedi's abilities in practice.

2 could also be explained by advanced materials technology. The filaments, perhaps created by Force-guided elemental deposition, may simply be too strong for human muscles to break by whacking them together.

3 could perhaps be solved by making the filaments loop back around at the tip instead of terminating in a ceramic cap. A single filament, then, would spiral clockwise out from the base of the blade, make a 180-degree turn, and spiral back inwards counterclockwise. The only problem is that this would produce much greater light pressure in the tip than along the rest of the filament; saber designers would have to take this into account to avoid catastrophic failure.

>This implies that a sufficiently powerful Force user could parry a lightsaber with their bare hands!

Relevant YouTube clip: [1]

Star Wars games are considered C-Canon[2], so I think it's a safe bet a work as huge as SW:ToR can be considered authorative. I also remember Knights of the Old Republic 2 having a feat called "Unarmed Parry" or so which allowed parrying any melee weapon.

[1]https://www.youtube.com/watch?v=1ToztqqDcaY#t=203

[2]http://en.wikipedia.org/wiki/Star_Wars_Expanded_Universe#Off...

"The prevailing theory is that a thin layer of steam builds up around it immediately, preventing the rest of the water to come into contact"

A miss in front of an open goal :-). This should have mentioned the beautiful word "Leidenfrost" (http://en.wikipedia.org/wiki/Leidenfrost_effect)

Leidenfrost effect is how you test if your stainless steel skillet is at the right temperature for cooking.

If you are into cooking, I must insist you check this out - http://www.youtube.com/watch?v=CB-SCA1reqE

On Earth Unplugged they show how to direct a droplet of water using this effect. [1]

[1]: http://www.youtube.com/watch?v=hIXFxP_6m7I

I was aware of this effect but unaware that it had a name. Thanks for that!

Not sure where the original source is but this is definitely worth a read: http://geektyrant.com/news/architect-of-death-star-speaks-ou...

"Also, the filaments are so thin and so far apart (relatively speaking), that beams from energy weapons hardly affect them and just pass through."

A lightsaber is supposed to reflect the beams of energy weapons. Not let them through.

I always thought light saber was basically plasma contained by magnetic field.

electromagnetic containment sounds like the most viable solution. Now how are we going to solve the inevitable heat dissipation problem. Basically we're trying to mimic the conditions of the sun, and wield such immense power in a very tiny handle no? Don't think this will ever be possible :)

Not with that attitude it won't.

I think eventually something like a lightsaber would be feasible. I like to envision my Southern descendants having fun by hovering along in their speeders in the middle of the night slicing off the tops of mailboxes.

Me too.

That was a fun read.

So this version of the lightsaber differs in that it has a visible cap on the tip and that it doesn't reflect blaster fire?

And it doesn't glow in space.

And that it's almost useless as compared to canon.

> Force-operated

If it's force-operated, how did Han use Lukes's to slice open the tauntaun on Hoth?

Making light saber technology somehow tied to the Force answers an obvious question from Star Wars: why do only Jedi have light sabers?

There's a more mundane answer: they're just not very useful weapons for normal people. It's like the difference between a sword and a gun. Which would you rather have to defend yourself? The gun beats the sword every time.

Unless--you're so super-humanly fast and accurate that you can use your sword to block every bullet fired at you. Or even better, bounce them back at the person who fired them.

Light sabers are great weapons for Jedi because Jedi have the reflexes and skills to make them useful. This is not limited to light sabers--we've also seen Jedi be superior as pilots, pod race drivers, and blaster shots.

You don't need to be force sensitive to use a lightsaber but it helps because it's weightless so someone without force enhanced reflexes is likely to slice off an arm or foot trying to actually fight with it. I'm pretty sure though there are a couple of expanded universe characters who use lightsabers but aren't force sensitive and of course there's General Grevious who is a robot.

This is starting to sound like a Big Bang Theory episode :)

I remember playing Jedi Outcast where you start as a regular guy with guns and then you slowly get new force powers. At the beginning I never used the light saber. However, the more skills and power the character got the more I was using the saber until at one point it was the only weapon I would ever use. The blasters just felt clumsy and limited.

It's useless until you get the ability to deflect blaster fire with it. Then it become free armor and eventually you can reflect most of the weapons back at the person who shot them.

Why would Jedi not be master gun fighters then?

I think in one of the movies one of the Jedis calls the blasters clumsy or ugly or something. They're looked down upon as too easy or low class.

Also if you just have a blaster, then you can get shot. With a lightsaber you can block shots at you, and also block force lightning.

Obi-Wan Kenobi calls a blaster "so uncivilized" as he throws one away, after using it to kill General Grievous in Episode III: Revenge of the Sith[1] (see time mark 6:17).

[1]: http://www.youtube.com/watch?v=7oGf-a1Dqlc&t=6m17s

After watching the whole thing, the winner can say that. None of that was "civilized"

They probably would be, but presumably you'd run out of "bullets" pretty quickly if you were trying to block other bullets. Plus, a "blade" is probably more useful than a gun in most cases (e.g., breaking down a door.)

I think that they are. (Can you think of any in-universe proof they are not?) Blasters are less versatile than light sabers, though, so they carry light sabers.

Kyle Katarn would like a word with you ;)

I believe it started as a fan theory, but Han's incredible luck has been explained as latent Force-sensitivity. Appears to have made it into some expanded universe material.

http://starwars.wikia.com/wiki/Han_Solo#Personality_and_trai...

Seems like a fan 'solution' to a fan 'problem'. There isn't anything in the movies to suggest that Han using the lightsaber was problematic. There was nothing to explain until other fan theories were made despite being in conflict with that scene in the movie.

I was under the impression when I first saw that scene that lightsabers were just meant to be technology - the more "civilized" version of a blaster in the way swords were once seen as more civilized than guns, but still basically just a device. Han knew where the button was to turn it on, which was all he needed to know. In the same way you wouldn't have to be a samurai master to use a katana to cut a watermelon.

Which is why this universe is so damn awesome!

I always thought one had to be a trained Force sensitive to construct one, which is among the final tests of becoming a Jedi. Apparently if you didn't build the device properly, it would blow up in your hand upon first activation.

Which is also why they are not mass produced.

Luke Skywalker's first lightsaber was his father's, it was blue. Luke built his second one, which was green. Vader later noted this as a sign his skills were "complete".

EDIT: I'm now reading that at some point lightsabers were indeed mass produced. I think that ruins the fun of the mythology around the weapon.

EDIT2: Now I'm reading that the crystal must be infused with the Force by the builder before construction. Fun mythology back on?

Does the Force require lucidity in order to operate?

no but Han does not use the force

Yes, but only out of choice. He is actually the most powerful Jedi in existence, which is how he managed to travel through time to fight the Nazis.

You mean in Raiders of the Lost Ark?

Yeah, the Ark is actually a Sith relic containing the ash from Vader's cremation on Endor.

http://i.imgur.com/mJMj0.gif and now I know what's in the briefcase in Pulp Fiction.

Han doesn't have to use the Force. Luke is present, though not lucid, and he uses the Force.

As with all things Star Wars Wookiepedia has an extensive article on how lightsabers work "in universe".

http://starwars.wikia.com/wiki/Lightsaber

Nice, but tail mirror doesn't reconcile with Jedis sticking sabers into metal doors to cut the openings.

Now I'm no physicist, but wouldn't the heat of the "blade" still be capable of melting the door, unless the jedi applied enough pressure to actually collapse the blade?

Indeed. If I recall the scene in question correctly, they did seem to be quite ginger in applying pressure, appearing to let the heat do all the work. (Mind you, I haven't seen that movie in at least a decade and my youtube/google-fu failed to produce a clip)

I recall that on several occasions Jedi just shove the things as hard as they want into and through whatever they want. Especially in fighting the droids in the Clone Wars episodes.

I assumed the slowness of sliding the blade into the door in the scene you mention was due to the thickness of the door. It couldn't be sliced open because it was too thick, therefore you melt a hole into it.

I'm not even sure why that part is necessary. The mirror can be anchored at the other end and the filaments constructed/woven such that they assume the proper shape when charged.

My theory - just made it up - a lightsaber is a hologram formed by phase conjugation of third-order non-linear vacuum polarization (chi-3). A fusion energy source emits gamma rays which form the hologram, and in turn the hologram shapes the beam, it's a feedback effect.

A lightsaber beam can block another light beam in the following way - the incoming beam acts as a wiggler for the lightsaber pump photons, which first get downshifted and then disintegrate into matter-antimatter pairs. The trick is to separate the matter from antimatter and channel them into the reactor. So firing at a lightsaber actually charges it.

The problem of course is conservation of momentum. To counteract the backwards jolt, a lightsaber creates a forward momentum impulse. This counteraction is not perfect, so Jedi are trained to maintain their balance in such situations.

When two lightsabers contact their beams are actually consumed by the other. That's why the Jedi/Sith can go on fighting forever, all the while throwing senate furniture at each other.

Obviously there is no power supply. The Jedi channels the energy of the Force.

I never noticed the Jedi avoiding looking at the naked beam of a lightsaber in the movies. I'd think it would be quite damaging to the eyes.

Han Solo cutting open the Tauntaun in ESB is the death-blow to any mystical theory about lightsabers.

Unless Han Solo is force sensitive.

It's never been conclusively ruled out. Curious fans have speculated about it every now and then. In the books, he ends up fathering three Jedi. (Granted, he fathers them with Leia, a known force-sensitive. But it's entirely possible he's force sensitive, too.)

I should note that a fantastic way to start a nerd fight with Star Wars fans is to take the position that Han is force sensitive. Most people seem vehemently opposed to the idea. They see it as breaking character and/or narrative theme for him.

Star Wars is just the realpolitik machinations of midichlorians trying to gain lebensraum.

Midichlorians are heretical. They are the propaganda of a false prophet. The force exists outside of such things.

Is there a special branch of Godwin's law that includes the addition of Episode 1-3 to references to the 3rd Reich?

Yes, they are a splinter group of Interpol. Jackie Chan is one of their detectives.

edit - there should be a scifi detective/cop show called "Godwin's Law" about police vs Nazis, in space. That would be awesome.

In fact I am slightly annoyed that it doesn't exist already.

I'll join you in that! In the meantime, there's Iron Sky.

How can you combine Ayn Rand, Ray Kurzweil and Star Wars for nerd baiting?

If it is, it isn't conscious, Han Solo cuts open a Tauntaun at the beginning of Ep 5 with Luke's lightsaber.

There's also Gen. Grievous and his throphy lightsabers.

we don't mention him...

For all that's known, Grievous was a pretty good fighter before he got turned into that machine monster. So, like Vader, he is still alive in a Force sense.

I guess this is also why his MagnaGuards don't carry lightsabers, but electrostaffs instead.

Nobody cares about Grievous. He's part of the later, shittier movies from a different director (yeah Lucas in 2000s has nothing to do with the Lucas in the 70s).

Didn't Luke wield a lightsaber before he knew he was force sensitive?

Yep, he picked it up and just turned it on. I guess you could say it was natural instinct but I would have to think such a thing would require a great deal of concentration.

Plus there's the fact it's quite canon that there's a power source. Luke bought one when he built his second lightsaber.

EDIT: Thanks to Wookiepedia I now see that the earliest lightsabers were the result of the user channeling the force through the device. Later to be changed to various power sources which resulted in superior weapons.

That shit was stoles from Dune.

Maybe just having the lightsaber Luke's proximity was enough to power it? After all, some Jedi can hurl their lightsabers.

I read a long time ago in some kinda official source, that they have a cold fusion source in the handle.

3D ionizing laser can create and energy beam of a fixed length or point. And thus create your light saber. http://www.gizmag.com/burton-true-3d-laser-plasma-display/20...

I couldn't see an explanation of how the sabers can strike each other without causing damage to those around them, or themselves.

Also, wouldn't a ceramic plate in the handle make the saber incredibly fragile?

Some ideas from Michio Kaku: https://www.youtube.com/watch?v=aLcEYbAdyxk (goto 5:13)

http://starwars.wikia.com/wiki/Lightsaber is anyone cares enough to read it.

"Anything it touches is heated to 4000 to 5000 oC within milliseconds, depending on the properties of the material. And we all know what that can do!"

Just the face temperature of the sun, probably would melt your face off as soon as you turned on the thing.

5000 degrees, centimeters away from a naked hand, would be kinda damaging to skin.

Not necessarily. Temperature determines which way heat energy flows, it says nothing about how fast it flows. I can hold my hand in an oven at 500 degrees with no problem because the transfer is very slow. Briefly touching a much cooler 150 degree piece of metal would give me a nasty burn, because of how quickly the heat transfers.

Not necessarily, maybe the thermal properties of the lightsaber are modified to give them high thermal resistance that is lowered contextually (like when youre slashing up some guy)

example of extremely high thermal resistance material: http://www.youtube.com/watch?v=Pp9Yax8UNoM

That's where _the force_ comes in. Nerd Shamed by vvv

Han Solo isn't a force user. Hoth

TBF He had heavy duty insulated gloves on and the lightsaber was only powered for ~10 seconds.

That is true. He could do it. But there is the problem of the Tauntan. If the saber did produce that temperature, they wouldn't need to rest inside of the the warm carcass, therefore, by the movie's logic, the saber doesn't produce much temperature.

Too much wind. Tauntaun was also only temporary as he set up a shelter.

If you had 5000° you could make a hot tub in the snow.

Plus it wasn't exactly hot on Hoth

Whether or not Han Solo unknowingly uses the force is an unanswered question.

Don't think General Grievous is a force user either.

I don't count that as canon. Plus he had metal hands so...

To be fair, Hoth was pretty cold...

can evanescent waves couple with the environment to generate the plasma?

Is this an idea for a startup?

who needs an explanation behind "its some space wizard stuff".

Nobody needs an explanation, but explanations are fun. Don't go hatin' on a man's hobbies.

It is funny to see which attributes each person believes need explaining. The article here spends paragraphs on the blade, but hand-waves a handle-sized terawatt power source into existence.

> hand-waves a ... power source into existence

This seems true to the source document.

AFAICT this version of the lightsaber is not collapsible. Which takes away the coolest aspect of it.

If you read the full article it is explained later on how the filaments of glass are coiled and wrapped in such a way that they fit in the handle and expand when lit by the light pressure causing the filament cords to expand like an inflated wick.

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