The Phony Physics of Star Wars Are a Blast

I’m a huge fan of Star Wars. The first movie (no, not Episode 1) came out when I was young, so I grew up thinking about the Millennium Falcon and lightsabers. Perhaps it sparked my interest in science—even if it’s not exactly science fiction. Oh, there’s a nice way to start a nerd fight: Is Star Wars “science fiction” or is it “space fantasy”?

Either way, you have to admit there are things in there that look like science. I mean, anytime you deal with stuff in space, it’s an opportunity to talk about science. That’s exactly what I’m going to do, since today is Star Wars Day. May the 4th be with you!

What scientific things in Star Wars are just not scientific? I’m going to go over some of the more interesting ideas, but don’t get me wrong. I’m using these errors as a way to talk about science, but I don’t think they need to be fixed. A more realistic Star Wars would probably be boring. Read on, you’ll see what I mean.

Sound in Space

The opening scene in Star Wars shows a massive Star Destroyer pursuing a smaller rebel ship. You hear the rumble of the engines, and it gives you the impression of a powerful vessel. Unfortunately, it’s just not possible.

Let’s think about sound for a moment. Suppose you tap a coffee mug on the side with a spoon. You hear a nice little plink. That’s because the tap caused the ceramic material to oscillate back and forth, which pushes on the air around it, compressing it. This compressed air then pushes on other nearby air as it expands. The whole process produces a pressure wave, and this pressure wave is what we call sound.

Is it possible to have a sound wave without air? Sure. You don’t need air, but you need something for the pressure wave to travel through. This could be a solid or water or really anything that lets a higher pressure push on parts with lower pressure. Sound waves need some kind of medium to “wave” in. In space there’s … nothing.

Well, that isn’t totally true. There are charged particles like protons and electrons moving through space—remnants of solar wind or debris from exploding stars. In a solar system there’s also some dust. Still, the density of this “gas” would be so tiny, you could hardly measure it. Much too low to transmit sound.

So why do moviemakers put sound out there in the void? Well, most of us have never been in space, and when things collide silently it just seems wrong. The sound of that massive Star Destroyer reminds us of a big ocean vessel passing close by—something we can relate to.

How Do You Steer This Thing?

One of the big ideas in physics is that forces change the motion of an object. If you apply a constant, continuous force to an object—and there is no counterforce like wind drag—that object will speed up and continue to speed up forever.

We call this Newton’s second law, and it works for multiple forces on an object by replacing them with a single force called the net force, as shown below. Here m is the mass of the starship and a is its acceleration.