As someone with more than a passing interest in science I often find myself screaming “that’s just plain wrong!” at films or TV programmes with a laughably poor grasp of basic scientific principles. One notion that just will not go away is the prorogation of sound in space. Whether it’s the destruction of the Death Star in Star Wars, or Dalek spaceships being vaporised in Doctor Who, everything in space seems to go ‘boom’.
Sound waves reach your ear as vibrations passing through matter – normally air. If you’ve ever been at a gig with large subwoofers you might have felt these vibrations passing through the floor and up your legs, providing you with that ‘thumping bass’ feeling.
Air is actually not a very good medium for transmitting sound. Try tapping a hard surface and listening to the sound it makes. The vibrations caused by your finger have been transferred through the molecules in the air and into your ear. Now place your ear on to the surface, and tap again. The sound should be louder. This is because the molecules of the solid surface are more tightly packed, and thus transfer the vibrations faster than air can.
What does this have to do with the Death Star? Well, in the vacuum of space there are no molecules – that is essentially what the word ‘vacuum’ means. Since there are no molecules there is nothing to transmit the vibrations caused by the Death Star blowing up, and so Luke Skywalker (and the audience) should not be able to hear the explosion.
At this point I have to mention Firefly, a TV programme created by Joss Whedon (best know for Buffy the Vampire Slayer). In Firefly, spaceships float serenely by in complete silence, often accompanied by some twangy (a very scientific technical term) guitar music. The effect is very strange, but only because the myth of sound in space has been perpetuated on our screens for so long.
Thankfully, someone is fighting back against this and other on screen gafs. The Insultingly Stupid Movie Physics website is one that I discovered many years ago now, but if you have never seen it before, it’s well worth a look. Sound in space is part of the ‘Generic Bad Movie Physics’ list, along with flaming cars and visible laserbeams.
The site also reviews movies, but not in the traditional sense. Ratings are dished out on a scale based on the American system ranging from GP for good physics to XP – physics so bad they can only come from a universe other than our own. The Terminator is deemed ‘pretty good’ despite the titular time-travelling cyborg, whereas Star Wars Episode III takes place, as you might expect, in a galaxy of physics far, far away.
Unfortunately it looks like the site hasn’t been updated in a while, but what is up there is still pretty entertaining. Of course, no one is expecting Hollywood to have a team of expert scientists on every film set, but it doesn’t hurt to get a few facts right.