What Can You Really Hear in Space?

sound in space
The beauty of the stars and galaxies is largely a visual experience. If objects make sound waves, they're too low or too high for us to hear. Listening to sound in space is nearly impossible. Space Frontiers / Stringer / Getty Images

Is it possible to hear sounds in space? The short answer is "No."  Yet, the misconceptions about sound in space continues to exist, mostly due to the sound effects used in sci-fi movies and TV shows. How many times have you "heard" the starship Enterprise or the Millennium Falcon whoosh through space? It's so ingrained our idea about space that people are often surprised to find out that it doesn't work that way. The laws of physics explain that it can't happen, but often enough producers don't really think about them. 

The Physics of Sound

It is helpful to understand the physics of sound. Sound travels through the air as waves. When we speak, for example, the vibration of our vocal cords compresses the air around them. The compressed air moves the air around it, which carries the sound waves. Eventually, these compressions reach the ears of a listener, whose brain interprets that activity as sound. If the compressions are high frequency and moving fast, the signal received by the ears is interpreted by the brain as a whistle or a shriek. If they're lower frequency and moving more slowly, the brain interprets it as a drum or a boom or a low voice.

Here's the important thing to remember: without anything to compress, sound waves can't be transmitted. And, guess what? There's no "medium" in the vacuum of space itself that transmits sound waves. There is a chance that sound waves can move through and compress clouds of gas and dust, but we wouldn't be able to hear that sound. It would be too low or too high for our ears to perceive. Of course, if you were in space without any protection against the vacuum, hearing any sound waves would be the least of your problems. 

What About Light?

Light waves are different. They do not require the existence of a medium in order to propagate. (Though the presence of a medium does affect the light waves. In particular, their path changes when they intersect the medium, and they also slow down.)

So light can travel through the vacuum of space unimpeded. This is why we can see distant objects like planets, stars, and galaxies. But, we can't hear any sounds they might make. Our ears are what pick up sound waves, and for a variety of reasons, our unprotected ears aren't going to be in space.

Haven't Probes Picked Up Sounds From the Planets?

This is a bit of a tricky one. NASA, back in the early 90s, released a five-volume set of space sounds. Unfortunately, they were none too specific about how the sounds were made exactly. It turns out the recordings weren't actually of sound coming from those planets. What was picked up were interactions of charged particles in the magnetospheres of the planets — trapped radio waves and other electromagnetic disturbances. Astronomers then took these measurements and converted them into sounds. It is similar to the way that your radio captures the radio waves (which are long-wavelength light waves) from radio stations and converts those signals into sound.

About Those Apollo Astronauts Reports of Sounds on and Around the Moon

This one is truly strange. According to NASA transcripts of the Apollo moon missions, several of the astronauts reported hearing "music" when orbiting the Moon. It turns out that what they heard was entirely predictable radio frequency interference between the lunar module and the command modules.

The most prominent example of this sound was when the Apollo 15 astronauts were on the far side of the Moon. However, once the orbiting craft was over the near side of the Moon, the warbling stopped. Anyone who has ever played with a radio or done HAM radio or other experiments with radio frequencies would recognize the sounds at once. They were nothing abnormal and they certainly didn't propagate through the vacuum of space. 

Why Do the Movies Have Spacecraft Making Sounds?

Since we know that you can't physically hear sounds in the vacuum of space, the best explanation for sound effects in TV and movies is this: If producers didn't make the rockets roar and the spacecraft go "whoosh", the soundtrack would be boring. And, that's true. But, it doesn't mean there's sound in space. All it means is that sounds are added to give the scenes a little drama. That's perfectly fine as long as you understand that it doesn't happen in reality. 

Updated and edited by Carolyn Collins Petersen.