4 Things Every Sci-Fi Movie Gets Dead Wrong About Science

Published January 11, 2015
Updated February 27, 2018

Lasers: Part Two—Visible Lasers

Sci Fi Movie Blunders Laser Gun

Source: Blogspot

This is one most people don’t really think about. After all, laser is light, and light glows, right? You’d think a bolt of laser fire would radiate in all directions and be visible for miles around if it’s really powerful. Except it doesn’t. Here’s a real laser being tested:

This goes right down to how lasers work. Light is made up of waves (shut up, Copenhagen interpretation of quantum mechanics). Each color of light is just a different wavelength, and in practice there are several wavelengths present within each color. Every wave has a crest and a trough, and sometimes the different wavelengths will overlap.

In places where the crest (or trough) of one wave matches up exactly with the crest (or trough) of another wave, the two beams are said to be “in phase,” and they strengthen each other. In places where the crest of one wave meets the trough of another, the beams are out of phase and cancel each other out. Averaged over multiple wavelengths, this creates a diffuse field of light that doesn’t have any particular direction.

Sci Fi Movie Blunders One Direction

Unlike the world of pop music, in which there is but One Direction. Source: Santa Banta

Lasers get their punch from the fact that all of the wavelengths of light in them are synchronized and in phase. Never mind how they do that, I’m not actually a scientist, or light-wizard, or whatever those people are called. The beams are just all in phase.

That means they reinforce each other and pump out a stronger beam than an equivalent-powered flashlight could, but it also makes them terrible flashlights. See, a coherent beam of light is, by definition, one that doesn’t scatter all over. A beam that doesn’t scatter is one that isn’t leaking stray photons out to the left and the right. That means that an observer who isn’t directly in the path of the beam shouldn’t be able to see it at all unless it’s firing through mist or something else that scatters light.

Sci Fi Movie Blunders Lab

Science just happened here.
Source: FALW

What all this means is that a truly accurate laser fight would hardly register on screen at all. Take the classic boarding scene from the beginning of Star Wars: The little ship would be depicted gliding away from the star destroyer at such a distance that the two couldn’t be rendered together in the same shot. The Tantive IV would occasionally pop open here and there with little holes as the destroyer’s laser cannons bored into its hull. All of this would be completely silent.

On boarding, the stormtrooper force would blow the hatch open and come pouring through the gaping hole. We, the audience, would only see little holes open up in their armor as they fall, without any idea where the shots were coming from. The stormtroopers’ guns would, likewise, just flicker a bit at their tips and set things on fire all over the place without any beams or bolts emerging.

It would be a terrible sequence, and George Lucas would be hooking on the interstate if he’d been dumb enough to write it that way. It would still be right, though, so let’s get on the re-re-make, Disney. And would it kill you to give Princess Leia a show-stopping musical number this time?

author
Richard Stockton
author
Richard Stockton is a freelance science and technology writer from Sacramento, California.
editor
Chris Altman
editor
Chris Altman is a freelancing writer and artist based out of Brooklyn, NY.