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Is there a reason ever given that explains why a lightsaber (which I assume/was made to assume is a sort of laser) doesn't go on infinitely like a normal laser (excluding atmospheric conditions)?

Or is the blade of a lightsaber something different than a laser?

Lightsaber Reference in XKCD

  • I think it's possible scientifically through a concept called fourier transformations, though the saber could not be made of a laser in that case. – apoorv020 Aug 3 '11 at 21:19
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    @apoorv020: This does not make too much sense. The Fourier transformation is not a real transformation that transforms a physical object (or electromagnetic force, or anything). It is a mathematical operation. – vsz Feb 5 '12 at 9:36
  • @vsz Using a fourier transform, it's theoretically possible to form a pulse of light, using wavelengths from 0 to infinity. Though not everybody would have done college level courses, I left the technical details out. – apoorv020 Feb 5 '12 at 17:49
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    @apoorv020: Maybe you use the Fourier transformation to calculate what your controller should do, but not to physically accomplish something. Having an infinite number of lasers to cancel each other completely is still impossible to do. – vsz Feb 6 '12 at 5:36
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    Added an amusing (and, I think, relevant) XKCD cartoon. Please revert if you don't approve :) – K-H-W Oct 13 '14 at 13:40
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According to a lot of the Star Wars Extended Universe info, they actually arc back after a certain distance; it's just not terribly visible in the movies; think of them arcing back in a beam right next to the one emanating for the emitter. (It may help to think of a magnetic field (like the traditional 'Magnetic Bottle') being generated to point the out-flowing energy to somewhere a few feet away, then being 'Capped' there, forcing it to arc back to where it grounds.)

I'm trying to hunt up the article with all of the history on them (they have changed a lot over time), but for the moment, this is probably what you are looking for:

...they developed a method to generate a focused beam of energy that arced circumferentially back to its source, creating a controlled energy circuit and leading to the first portable high-energy blades.

Then,

Once focused by the crystals, the plasma was sent through a series of field energizers and modulation circuitry within the emitter matrix that further focused it, making it into a coherent beam of energy that was projected from the emitter.[25] The blade typically extended about a meter before being arced by the blade containment field back to a negatively charged fissure ringing the emitter, where it was channeled back to the power cell by a superconductor, completing the circuit. Below is a list of the primary parts almost all lightsabers needed to use to function properly:

From: Lightsaber on Wookieepedia

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From what I've read, it's best to think of the blade mathematically as an ellipse or ellipsoid with an exceptionally small conjugate diameter, rather than as a straight line. Instead of creating a line of energy that stops at an arbitrary point, it's creating a ball of energy that is exceptionally distended in a specific way.

In simpler terms, think of somehow focusing a laser to travel in a very tight circle rather than a straight line, so the light loops around in the shape of a sword blade. Of course, the problem is the "somehow". That's what makes this science fiction. We don't know how to do that right now, but perhaps you can just imagine someone discovering a principle that makes it possible.

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    That would justify double-ended lightsaber being easier to make than single-ended ones: the generator is at the center, so single-ended ones need an extra piece of technology for asymmetric containment. Double-ended lightsabers had thus phased out by the time of episode IV, everyone having moved to the newer, more maniable technology. – user56 Aug 4 '11 at 7:26
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    Tempting, but this doesn't explain how one side turns on before the other in episode 1, nor how it still functions as a single side light saber when cut in half. – Aphaea Aug 4 '11 at 13:15
  • Perhaps it had a specific mechanism to turn of the asymmetric containment if assembled but by episode IV it was lost tech? – jclozano Dec 27 '11 at 20:29
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    @Aphaea It was two lightsabers welded together... - starwars.wikia.com/wiki/Darth_Maul's_lightsaber – Tobias Wärre Oct 13 '14 at 13:54
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Lightsabers have changed little in the thousands of years of their employ by the Jedi Knights. Those who believe the Jedi order began on the ancient world of Ossus point to the abundance of Adegan crystals in the system as proof. These crystals are ideal for the creation of lightsabers, as they focus the energy released from a saber's power cell into the tight, blade-like beam. Early lightsabers did not have self-contained power cells, and were instead connected by a conducting cable to a belt-worn power pack. Once unleashed, the power channels through a positively charged continuous energy lens at the center of the handle. The beam then arcs circumferentially back to a negatively charged high energy flux aperture. A superconductor transfers the power from the flux aperture to the power cell. As a result, a lightsaber only expends power when its blade cuts through something. So efficient is the blade, that it does not radiate heat unless it comes into contact with something.

http://starwars.com/databank/technology/lightsaber/index.html

Some have suggested magnetic fields and plasma:

Shin also recommended adding a degausser sound on top of the other sounds for the weapon since the sound would be reminiscent of a magnetic field.

Design and create a "magnetic bottle." Since the 1950s, the ability to contain plasma and other high-energy particles has been done with electromagnetic containment fields, otherwise known as "bottles." Electrons and other atomic structures have difficulty crossing a magnetic field. By shaping the field, you can direct or contain them. The shape of the field varies, but for the lightsaber effect, the interior of the magnetic bottle will have to be about 3 feet long and 2 inches wide. This requires several focused, high-energy induction coils to be mounted to a heavy iron core disk. The disk also serves as a mount for the hilt.

http://www.ehow.com/how_5056861_make-real-lightsabers.html#ixzz1U8DcZ8IM

One problem with the criticisms from a skeptics point of view (myself) is too many strawman the possibilities. For instance, yes, light would pass though, but the magnetic fields might react with each other. Light might only be present as a visual effect and the actual cutting taking place by some other means. In short, it may be possible to make a ‘light saber’ with some combination of technologies. Some which work together to repel light sabers from each other, other to cut materials, and yet others to create visual effects to guide the use.

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    Interesting: you're indicated that it's possible the "blade" was developed first and was perhaps not visible, and that the light effect was added afterwards, perhaps to aid the wielder in knowing where his blade was to prevent self-injury. – Joel Coehoorn Apr 3 '12 at 17:16
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There is no good physical hypothetical model of a lightsaber. While you could potentially use an electric field to contain plasma in the proper shape, this would (a) take huge amounts of energy to maintain and (b) still probably not exhibit all the sword-like characteristics. Think continuous lightening plus a strong, highly localized field to contain it. Even with magical crystals to resonate (insert appropriate techno-babble) enough energy, the grip would be incredibly hot.

Lightsabers are clearly not lasers, as they are visible, wide, and interact with each other with substantial forces. Sadly, this is one of the "magical" details of Star wars.

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    Why is 'magic' in SF sad? – Anthony Aug 3 '11 at 23:29
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    'Sadly', I believe, because it means we're unlikely to ever get to play with them for real. – Jeff Aug 4 '11 at 1:42
  • Yes, I meant sadly unrealizable. If sci-fi stuck to purely reasonable technologies, it would either be boring or all the authors would need PhDs. – Aphaea Aug 4 '11 at 13:18
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    @Aphaea, I long for the days when this was reality, back in the golden days of Hard SF. – DampeS8N Aug 4 '11 at 17:39
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    On the reinassance who would have thought of a little box that could make you talk with anyone even thousands of miles away and also work as a personal library? (smartphones) it would have been called sadly magic – jclozano Dec 27 '11 at 20:31
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Light Sabers are not lasers. They are an energy projection/magnification of the crystal inside of them. It's crystalline structure is barely noticeable due to the intense light that the projection gives off but you can see it at the tip of the sabers. Think of it like a hologram, only one that channels and focuses immense energy into its projection.

  • Not quite, there's a bit of plasma going on, and other things too if you look at sources like the visual dictionary. They are indeed lasers, but not quite a projection like you say it is. – CBredlow Jan 11 '16 at 19:55

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