When I was in high school, I wasn't among the most talented students in physics. I liked some aspects of the subject but was usually bored by the linear approach of all the mathematical formulas involved. I remember one specific day, though, when we were talking about planets, space and its emptiness and my physics teacher asked a question:

Imagine you are an astronaut, out on a mission on the moon. You just landed on it, went outside with one of your partners and try to talk to him through the communication system in your helmet. But for some reason, the transmitter doesn't work anymore and you have to find another way to verbally communicate with him. What do you do to talk to him?

Nobody had an answer. Then I raised my hand. "You could go over to him and press your helmet against his, so that there is a bridge between the helmets. This way, if you talk sound will be able to travel through, over to his helmet." I was happy. Not only did I know how to bypass communication if I ever became an astronaut and my transmitter died on me out in space. But more importantly, I gave a correct answer in a physics class. From this moment on I had a thing for sound in space.

For a sound designer, science-fiction is an exciting and challenging genre. Depending on the material you are working on, you will have to create sounds for spaceships, weapons, machinery, technologies or even whole different species, planets or galaxies. But there are not only huge amounts of unique and characteristic sounds to be crafted from scratch. As soon as you deal with space, you'll have to choose your style: Do you go silent and physically accurate - or do you prefer the more traditional approach to sound in space: big sound. Let's find out what realism can do for sound design in space. And why sometimes it's better to use less realistic sound to make a film feel more real.

Reality, Realism and Realistic

Like with many terms that describe big concepts or ideas, it is hard to define 'reality' in a few, simple words. To avoid getting too philosophical, let's use 'reality' in the sense that it defines the actual world around us, the real world with all its things, entities and events. 'Realistic' then describes things or situations that try to imitate reality as close as they can. If something or someone is good at doing that, we perceive their work as realistic. In art, 'realism' pursues a high level of being realistic - getting a piece of work that is not real itself as close to a depiction or representation of reality as possible.
There are plenty other definitions of these terms (with cinematic realism alone having a plethora of discourses), but we'll keep them for the purpose of this blog entry.

Now, what exactly is it that makes a film's sound realistic? Is it a soundtrack (and by that I don't mean music) that adds little or nothing during the postproduction of a film and stays true to the material that was recorded on location or set? Is it a detailed acoustic recreation of the physical space of a scene, with every little sound that you would hear if you were there - developed and carefully placed by sound designers, sound editors and re-recording mixers? Or is it a multi-layered or sometimes quite simple array of sounds selected to match what's happening on-screen that makes a film sound realistic?

The unsatisfying answer is: it can be any of them. Realistic sound is not an exclusive concept. When some might be used to and expect a spaceship to make a sound while it flies by on screen, others wouldn't call it realistic. Realism is a reflection of reality, and films are a representation of reality. Everyone decides for their own if they deem a film realistic or not - and sound plays an important part in it.

Realistic sound in space

In order to judge realistic sound in space, first, we need to get the physics of sound straight. As you might remember from school, sound works through waves. Waves need a medium to travel through to get to our ears. On earth this works out just fine: we can perceive sound through waves in the air, water, even metal. In space, there is nothing. At least nothing we know of yet - and certainly nothing for sound waves to travel through. Space is silent.

At 372 miles above the Earth
There is nothing to carry sound
No air pressure
No oxygen

Life in space is impossible

Opening statement, Gravity (2013)

So, realistic sound in space should be silent, right? Anything else would be unrealistic, wouldn't it? Well, it's not that easy.

In the last years, two big blockbuster productions have represented sound in space quite physically accurate: Alfonso Cuarón's Gravity (2013) put audiences right in the helmets of its protagonists. We hear everything we would if we were out there in space with our colleagues Dr. Stone and Kowalski. And when the 'Explorer' bursts into pieces through debris, we see it, but we don't hear it:

A similar stylistic direction was taken by director Christopher Nolan and the sound team behind Interstellar (2014). Although a big Hollywood production (just like Gravity), its soundtrack goes completely silent when it cuts to exterior shots in space - with the only exception of Hans Zimmer's beautiful score sometimes bridging acoustic gaps. What it does, is create an engaging contrast on many different levels. The following excerpt from Interstellar exemplarily shows those contrasts. Watch.

Warning: contains major plot spoilers.

The basic sound design principles that Nolan and his team follow throughout the film are evident even just in the first 30 seconds. If you listen closely, you will notice the following pattern:

Interstellar - Docking Scene (first 30 seconds)

Green cells represent an active track, red cells represent an inactive track. You can clearly see that exterior shots lose all dialogue-, sound effect- and atmos-tracks. The only thing that Nolan allowed to continue is music. There are two very nice touches in those first 30 seconds: Notice the exterior shot of Dr. Mann trying to dock at the Endurance. You see the docking apparatus, but hear nothing but music. After the cut to the interior shot, our attention follows what Dr. Mann is trying to explain to Dr. Brand. But in the background there clearly is a muffled version of the hook mechanism unsuccessfully trying to complete the docking procedure. Another really nice touch is the moment of the explosion. Quite unexpectedly Dr. Mann gets interrupted mid-sentence because he causes his ship and parts of the Endurance to blow up. What happens acoustically is a shift from an environment filled with air to the vacuum in space. Consequently, the previously given physical foundation for soundwaves to travel - in other words: our ability to hear what's going on - literally gets sucked out of the door. With a nice, wooshy-slushy sound effect we loose all air and get surrounded by a moment of complete silence. It is only after 6 seconds that we're back with Cooper and Dr. Brand, as her word of warning gets interrupted by the explosion and Zimmer cues the next section of his score.

Add a little contrast to spice things up

Following this model of realistic sound in space offers a variety of contrasting moments, such as loud vs. silent, dramatic vs. comforting, passively being immersed in the film vs. actively engage with the film. These contrasts, when carefully placed, bear the opportunity to surprise the audience with the unexpected and unusual. We are so used to big explosions being accompanied by corresponding blasts of sound that the absence of those sounds is more surprising than what we would hear in reality. Physically correct sound in space has an interesting effect, though. It seems to change the viewers' disposition from passively watching, immersed by what's presented to them, to actively engage with what unfolds in front of them. Breaking through the familiar pattern of 'big explosion = big sound' invites audiences to enter into a dialogue with the film, attentively following and questioning what is going on on screen. Generally speaking, it is not important where you break this pattern in your film, be it on earth or in outer space. But when you do it in space, it's not 'just' a creative way of breaking expectations - it's physically accurate and realistic.

When Style beats Physics

Although personally I love the concept of physically accurate sound in science-fiction, it sometimes just doesn't fit the style and concept of a film. One of the most famous film franchises that decided to fill space with sound is Star Wars. Here, although you have plenty exterior shots out in space, you hear sounds just like you would on earth: the deep rumble of space stations, the high-pitch plane turbine engine sounds, laser blasts and big explosions. Pay attention to what the exterior space shots in Star Wars - A New Hope (1977) sound like:

For a big scale, top budget franchise like Star Wars it absolutely makes sense to take a more traditional route for sound design in space. Big explosions cause big impacts, both physically in what happens on screen and emotionally in the audience. Loud sound supports that effect. Whether you call it a cheap method of sensationalism to maximize the impact a film might have on viewers or an effective way to fully immerse audiences in the moment and to create the spectacle of cinema - in any way it is effective.

Star Wars' sound design is nothing short of outstanding and people, me included, love it for its characteristic and unique sound effects. Many of which we would never have heard, had George Lucas not decided to defy physical accuracy in sound. He knew that his style of storytelling would benefit from sound in space. Just imagine an extensively silent Death Star assault...

And Star Wars is in the best of company: lots of blockbuster space films (some of which are not even sci-fi) used this approach: Alien (1979), Total Recall (1990), Apollo 13 (1995), The Fifth Element (1997), Star Trek (2009) and Prometheus (2012).

Does the use of sound where it normally couldn't be make it less realistic? Is it less realistic because it is not what you would hear if you were right out there in space, next to the camera? Of course not. Film sound is hardly at any point an accurate representation of reality. It is a selection and a mix of sounds that artists have agreed upon to fit, support or sometimes contrast the visuals of a motion picture. There are times when this mix of sounds may feel realistic, where its intention is to let things sound as you would experience them out there in the real world. And there are instances, where artists deliberately choose to depart from realism in sound. They might alter the real soundscape of a setting and take out atmospheres, add sound effects, alter voices or insert additional foley.

Film sound, as film itself, can only ever be an approximation to reality. Given its fragmented mode of production, it is inherently an artistic construct trying to create a or represent reality. Sound Designers help make that construct feel as realistic as it can be - regardless of the stylistic path they choose to achieve their goal. Whether they want to silently burst the Endurance into pieces, or annihilate the Death Star with a big boom. They create their own acoustic reality that hopefully feels genuine to their viewers. And isn't that what ultimately makes a film feel realistic - or even real?

Take a closer look at silent space sound design with an example from the most famous science-fiction franchise Star Wars in my hands-on blog entry.