Lightsabres

Lightsabres

Like most people, I thoroughly enjoyed the three original Star Wars films, and like most people, I found the prequel installments rather disappointing. The special effects and visual quality were dramatically improved, but the stories left much to be desired, the acting was mediocre, and the writing had none of the intensity or sparkle of the originals. After“ Episode I: The Phantom Menace” appeared, I was discussing it with my friend Johanna. We spent a lot of time complaining about Jar Jar Binks, the interminable pod race sequence, and the complete absence of memorable dialogue. But as we talked, I realized that despite my criticism, there was still something about the film that inspired me. So I said, “ Even considering all these problems, be honest. When you left the theater, didn’t you want to be a Jedi knight?” Johanna smiled sheepishly and said, “ Well, yeah, of course!” Me too.

That’s not to say I’d record my religion as“ Jedi” on a census form— Star Wars is, after all, just a story. Still, Jedi knights are very cool, in the way comic- book superheroes are. They have mysterious telepathic and telekinetic powers; they are expert fighters; they nearly always manage to save the day. But the best thing about Jedi knights is that they carry what they consider a simple, low- tech weapon: a lightsabre.

Is That a Lightsabre Under Your Cloak, or Are You Just Happy to See Me?

There are plenty of Star Wars fans, collectors, and Web sites, but there’s also a thriving fan subculture related specifically to the lightsabre. A number of companies do booming business supplying collectors with exacting replicas of lightsabre props. For example, a company called Master Replicas creates limited- edition runs of replicas for each of the lightsabres seen in the films under license from Lucasfilm. So far, they’ve sold more than10,000 of these replicas, at prices ranging from US$249 to$599— with some1,000- unit runs selling out in less than24 hours. I find it truly amazing that so many people are willing to spend so much money on completely nonfunctional replicas of film props.

One popular pastime of lightsabre fans is discussing whether or how an actual working lightsabre could theoretically be built— as if to prove to themselves that there really is some possible world in which lightsabres exist, that what the films depict could be true. Respectable scientists have weighed in with their theories and opinions, and amateur theoretical physicists have added their own speculations. Because of the passion with which some people want to believe lightsabres could exist, an enormous amount of effort has been expended to reverse- engineer this imaginary weapon. Surprisingly enough, it just might be possible to build such a thing… eventually.

The Science of Lightsabres

So how could you construct a working lightsabre? It’s tempting to say you could use a laser beam, but that wouldn’t work. For one thing, a laser beam doesn’t just stop at an arbitrary point in space; for another, it doesn’t radiate light to the sides unless it’s traveling through a refractive medium such as smoke or water vapor. And, of course, since it’s just a beam of light, it wouldn’t repel another blade. In short, a laser beam really behaves nothing at all like a lightsabre.

One popular idea for how a lightsabre might be created involves the use of plasma. Plasma is a type of superheated gas that glows just as a lightsabre blade does. The light from neon tubes comes from plasma, as does the light of the sun. One of the interesting properties of plasma is that it can be contained by a magnetic field. Some people speculate that if a lightsabre handle created a cylindrical magnetic field then filled it with plasma, that would look( and act) very much like the lightsabres of Star Wars— right down to the repulsive effect when two blades touch.

There are a few problems with the magnetic- field idea. First, nobody knows how to project a magnetic field out to a precise point in space at which the power sharply drops off. Magnetic fields lose strength in proportion to their distance from the source. That means the strength of the field a meter away from the handle would be much weaker precisely where it needs to be strongest— to prevent the plasma from shooting out the tip of the cylinder. Even if that problem could be solved, though, the amount of power required to create a field that could contain the plasma would be enormous— on the order of that produced by a building- sized generator. Packing that power into a lightsabre hilt would be quite a feat. Then, of course, you’d also be creating a magnetic field that would powerfully affect a lot of things other than the plasma. Having your belt buckle, say, sucked into the lightsabre blade when you activate it would probably not help you defeat your opponent.

May the Force Not Singe You

A variation on the magnetic field idea is that a stream of plasma could be sent down the center of the virtual blade, but then be pulled back around the outside— sort of like a fountain. This may solve the problem of blade length with its“ push- me- pull- you” effect, though it would still require an immensely powerful magnetic field. But there’s an even more serious problem with all plasma- based designs. Plasma hot enough to sever limbs and burn through metal doors also radiates enough heat to singe anything in its near vicinity, including the hand and clothing of the person holding the lightsabre. Heat, like magnetic fields, does not stop suddenly at an arbitrary point in space.

If plasma contained in a magnetic field is not a viable solution, are we simply out of luck? Not necessarily. A great many alternative models have been proposed, with varying degrees of scientific support. All of them are ultimately speculative, relying on hypothetical advances in science or engineering, or the discovery of substances that have not yet been shown to exist. Some models abandon the image of a cylinder for a very tight arc or loop that might have a similar appearance— the notion being that electromagnetic energy of one form or another could possibly be coaxed into such a shape. There’s also the suggestion that some novel material may be discovered that could stretch like a balloon when“ inflated” by an electron beam, but remain laterally rigid. Still others think the exotic notion of“ virtual particles” created by spinning a conductive disc at close to the speed of light could achieve the desired effect.

Speculation on how a lightsabre might be built does not always stick to the facts of science. Some fans judge proposed technological solutions not by their scientific plausibility, but by their adherence to the descriptions in the Star Wars films and books. In other words, if a proposed design were in all ways identical to the lightsabres of the films except that it didn’t make the trademark humming and swooshing sounds, some fans would reject it as being an unacceptable( or at least incomplete) solution. As much as I appreciate Star Wars and technology, in my professional opinion this attitude is just nutso. “ Real” lightsabres, after all, are just a plot device. It may or may not ever be possible to construct something that approximates the appearance and behavior of a lightsabre, but it’s certain that the only way to make something exactly like that is by rotoscoping the glowing shafts of light on film( or a computer) and adding sound effects artificially. That said, I still think the idea of a lightsabre is interesting enough that inventing a way to achieve that effect is on my life’s to- do list. But mine won’t hum, it will whistle. Deal with it. — Joe Kissell