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.
So if a starship is running its engines, it won’t travel at a constant speed. The only way you could do that is by turning the engines off. Instead, you’re rushing faster and faster toward what appears to be a moon … Wait, that’s no moon! Too late.
There’s another problem with the motion of starships: How do you turn? There are two things to think about here. First, both the acceleration and the velocity of the ship are represented by vectors (the symbols with the arrow on top). That means direction matters. Moving to the left is different than moving to the right.
The second thing to consider is the definition of acceleration. It’s the rate of change for velocity, and we can write it as the following:
Since velocity is a vector, changing direction means it’s accelerating, even if the speed is constant. But wait, we just saw that Newton’s second law says you can’t accelerate without a force. So in order to turn your cool starfighter, you need a force that pushes perpendicular to the direction of travel—a sideways force.
Take a look at the X-wing fighter. Does it have any thrusters on its side to help it turn? Nope. Instead, it turns to the left by rolling a little to the left and performing a banked turn. This is exactly how an airplane on Earth flies.
But what does an airplane have that an X-wing doesn’t? Right, the answer once again is air. For an airplane, there is this external force due to the interaction between the air and the wing, which we call lift. If a plane tilts to the side a little bit, this lift force can be used as a sideways force to make it change direction. That’s how things fly down here.
So, there’s your problem. The X-wing and other spacecraft use this same banking move to turn in space, even though there’s no lift on the wings. If you watch the battle over the Death Star, those TIE fighters and X-wings are zipping around like it’s a WW II dogfight. Again, it’s wrong, but I’m fine with it.
You Can’t See a Laser Shot
Star Wars isn’t very explicit about what is shot out of a handheld blaster or from the cannons on an X-wing. They sure look like lasers beams, and I think that’s what most people imagine. But they can’t be lasers. Why not? Two reasons.
First, a laser beam is light, and we know the speed of light: 3 x 108 meters per second. If an X-wing shot a laser at a TIE fighter that was 1 kilometer away, it would take just 3 millionths of a second to hit the target. If you have a film (like the real movie) that plays at 30 frames per second, each frame lasts 0.03 seconds. That means the laser would be so fast you wouldn’t see it. It would be like it’s instantaneous. That’s not good for movies. You want to see the shot.
Second, even if it was slower, the beam would be invisible in space. Remember, we see things when light enters our eye. That means there are two kinds of things you can see: things that produce light, like your phone screen, and things that reflect light. Your hand doesn’t give off visible light, but the sunlight bounces off your hand and hits your retina.
Now, a laser produces “collimated” light that all goes in the same direction. So the only way you can see it is if there’s something in the path of the beam that reflects light into your eye. On Earth there is something: air. And not just air, but dust and stuff. I took this picture below, and I amped it up even more by spraying fake fog into the beam.
But you know what you don’t have in space? Yep, air. So the only way you could see a laser beam is if it hits you right in the eye. That would be bad. Bottom line: Laser beams are invisible in space.
Faster-Than-Light Communication
When you call a friend, your phone transmits electromagnetic waves to the nearest cell tower. That tower sends a signal (through a wire) to another tower, which then sends an EM wave to your friend’s phone. None of these signals can move faster than the speed of light, so if you’re calling from New York to London, your words would take 0.02 seconds to get there. No big deal, they can wait two-hundredths of a second.
Now imagine you want to communicate with another friend on the surface of Mars. Well, Mars is much farther away, so information traveling at the speed of light can take up to 20 minutes to arrive, depending on the positions of the planets. It’s still not a big issue, but it is annoying.
OK, one more example. You have just one more friend, and they recently took a new job near the star Alpha Centauri—one of the closest stars to Earth. How long would it take to send a phone call to that star? The answer is 4.4 YEARS. No one has time for that.
You see the problem. In Star Wars: Attack of the Clones, Obi-wan sends a transmission from the planet Geonosis to Coruscant. If these planets are in different star systems, the signal could easily take 10 years to arrive. That really makes for a complicated plot. It’s much simpler to just make communications instantaneous.
But really, maybe Star Wars isn’t even wrong here. I mean, it is in a whole different galaxy, and they have special powers like The Force. Perhaps they figured out a way to send information faster than the speed of light. One thing is certain: Ignoring the science makes for great entertainment. But understanding the science sure makes you appreciate our home on Earth. Go outside right now and listen to all the sounds!
