UA Associate Professor Jason Jones doesn't think light sabers are very practical:

Jones, an associate professor in the University of Arizona's College of Optical Sciences and head of the Jones Research Group, knows a thing or two about lasers. And although he is a "Star Wars" fan who received a toy lightsaber for his birthday, he says laser swords are easier said than done for a couple of reasons — battery power and light physics chief among them.

Curiously, although they emit light, the lightsabers in "Star Wars" aren't made of it. They are said to be made of plasma — a hot, gassy blend of ions — wrapped in a "force containment field," which is probably some kind of electromagnetic field, Jones says. He adds that the lightsaber might be better off if it were made of, well, light.

Light is made of photons, which "don't like to interact with each other," so sword fighting with light would be futile. The physics just aren't there. But, say, cutting off a hand with it? Tricky, but not impossible.

Jones says that battery power would also be a problem:

"That's really the killer, I think," Jones says. "Whether you're using plasma or light, the energy requirements for any of these lightsabers are going to be huge. Like in a lot of cool, important technological areas, batteries are the bottleneck. Even if you could get batteries with the necessary energy density, you'd need to recharge them very quickly, and that's not going to work in the middle of a battle."

But the science doesn't stop him from enjoying the movies:

"My wife pointed out to me that everything I'm saying is ridiculous because I don't know the laws of physics on Tatooine," Jones says. "So, I have to qualify: This only applies on Earth. And maybe it'll be different when my daughter's old enough to ask me questions about 'Star Wars' and I have to decide whether or not to rain on her parade, but for now I like it because it's nostalgic."

Read the whole thing here.