Engineer explains why lightsabers WOULDN’T work

lightsaber diagram thumb

Hey everybody, it is Matt Gluesenkamp again. With such a big to-do at the research center about the 50th anniversary of the laser’s invention, I started thinking about how many movies out there show lasers being used in fantastical ways. From a bright red beam slowly moving to cut a bound-and-gagged spy in half (mostly possible) to a plane-mounted foot-thick laser popping a houseful of popcorn (not really going to work), there are a lot of myths and legends about lasers that Hollywood has generated or perpetuated over the years.

But perhaps the most well-known instance of “lasers” in cinema are the lightsabers from the Star Wars saga. I put quotes around “lasers” because the way lightsabers behave in these movies is quite a bit different from the way lasers behave in real life. So I wanted to take a look at these fictional devices, how they supposedly work in the Star Wars universe, and compare that to how they might work in our own, real, universe.

Pinning down the canonical inner workings of a lightsaber is tricky, but from browsing through the sometimes contradictory information on StarWars.com, Wookieepedia, and HowStuffWorks.com, I managed to glean what I thought was a pretty good breakdown. In the Star Wars universe, lightsabers are typically custom-built by Jedi and Sith warriors, but all have several common elements. Each has a power source, a lightsaber crystal, one or more focusing crystals, and a stabilizing emitter system. The power source is typically a diatium power cell, often with a capacity of several megawatt-hours. The lightsaber crystal converts the power cell’s energy into a plasma that is then passed through and directed by the focusing crystals. Finally, the emitter system stabilizes the plasma into a blade shape using a mix of power modulation and magnetic field containment.

Did that make sense to anyone? No? Good, then I’m not alone. Science fiction is typically a blend of materials and physical laws that do exist, and those that don’t. Although real-life battery technology is coming along great, we are a long way off from creating handheld batteries with capacities like that the ones found in the lightsaber’s diatium power cell. Perhaps the key lies in discovering this fictional diatium material?

Also, crystals do have many useful optical and piezoelectric properties but I don’t know of one that could magically create plasma from electricity. However, I read that the crystals must be “attuned to the Force” by a Jedi or Sith in a meditation ritual that can take days. So maybe we should start there.

Where the explanations of lightsaber technology get really convoluted is when they start talking about how the blade is shaped and contained. Magnetic fields are currently used to contain plasmas, but they are generated by machinery that must also surround it – Generating such a magnetic envelope from a single, unidirectional source would likely require some new laws of physics. There are also no crystals that can “direct” a plasma.

In fact, a plasma “being directed” by a crystal lens doesn’t make any physical sense anyway. A plasma is really just an ionized gas – a gas in which the electrons have been stripped from their atomic nuclei. We see plasmas all the time. They make up and are emitted from every star, like our solar wind and solar flares. The interaction of the solar wind with Earth’s magnetic field produces the aurora, or northern lights, another form of plasma. Plasmas are also the stuff of every spark and lightning bolt.

Although my specialty isn’t in plasma physics, I can very generally say that plasmas can be created by bringing gases up to a high energy level. The higher the energy, the more atoms will be stripped of their electrons, and the better quality plasma we will have. It’s completely possible that one could create a plasma by producing a large enough voltage difference, a la lightning, or a powerful enough laser focus. However, enormous amounts of energy are required with either of these approaches, and it would be extremely difficult to control the plasma’s shape. An electrical arc can have wild shifts in direction, and it can hardly be controlled without being surrounded by magnets. A laser will go in a straight line, but of course it doesn’t stop. A laser-based lightsaber would require a block or a couple of mirrors floating in midair, moving in sync with the hilt – which is of course largely impossible. On top of that, they would certainly melt in the presence of such a plasma anyway. Further, all of this is saying nothing about what the actual quality of the plasma would be and how reliably or quickly it would cut through objects.

So it seems quite impossible to create a lightsaber, as seen in the Star Wars films, using existing technologies, materials, and physical laws. But given the enthusiasm of Star Wars superfans out there, I wouldn’t be surprised if people are trying. Anyway, since I’m more of a nerd than a plasma physicist, I’ll pose this question to my colleagues: How do you think a real-life lightsaber could work?