It’s a question 12-year-olds often ask, and to answer it we need to start with what sound itself is. It’s vibrations in the air. It’s merely the transmission of an action. In the case of a scream, the particles of air are reverberating from the rapid exhalation of a human in distress or excitement. Every sound starts with an action. That’s why you hear sounds when you kick a soccer ball, tap on a window, or sip a coffee. They’re all just actions that get reflected in the surrounding particles of air, spreading out like ripples in a disturbed pond.
Our ear is the receptor of these air disturbances. The extremely sensitive eardrum within the ear picks up on these tiny ripples, and they get translated into noises that we hear in our brains. So, the essential ingredients for a sound are causation, a means of transmission, and a receptor. In our case here on earth, many – actually most – of the actions we perform cause a disturbance in the air that’s surrounding everything. The air then transmits that disturbance to all nearby locations. And if you’re standing near enough to the activity causing the noise, our ears easily pick up the noises which alerts us that something is happening nearby.
The vacuum of space
Now we get to space. By “space”, we usually mean the enveloping darkness that shrouds all parts of the solar system and beyond that aren’t lit by sunlight or filled by air. It’s literally the “space” or the emptiness between the celestial bodies that inhabit this vast, three-dimensional area.
However, this “space” or emptiness isn’t actually that empty. It’s full of giant stars, galaxies, planets, black holes, dust clouds, comets, and other objects. So to refer to “space” as a “vacuum”, that is a space that doesn’t have anything in it, is technically wrong. However, calling space a vacuum does denote one very useful truth, at least to our topic. Space is often referred to as being a vacuum because once you leave the surface or thin atmosphere of the objects that float around in it at great distance from each another, there’s basically nothing there at all. In almost all parts of space, one you venture out into it, there’s nothing there. Nothing at all.
For example, here on earth we’re constantly swathed in air particles, and surrounded by objects that do such things as exert gravitational pull on us and reflect light back into our eyes. But if you ventured up off the surface of the earth, and kept going beyond the clouds, beyond the atmosphere, into “space”, there would be nothing. You would be suspended in nothing. Nothing to stand on, nothing to breathe, and if you’re far enough away from planet earth, not much to see either.
That’s why you can’t hear anything in space. The critical element of transmission is lost. The air particles that exist in great numbers within every square inch of space here on the surface of the earth don’t exist in space. It’s just nothingness. So anything you do, whether it’s clapping your hands together or screaming for all you’re worth, doesn’t make any sound at all.
Not all space is a vacuum, though
Having said all this, there are still some places where you can hear things in space. This of course only happens in places where “space” isn’t actually nothingness. For example, inside black holes. In 2003, from the Perseus galaxy over 25 million light years away, scientists detected the sound of a black hole emanating a very, very, very faint B-flat. However, black holes can only do this because they have such immense energy radiation, they can cause ripples within the vast gaseous emanations of galaxy clusters.
So, now you have the answer. The next time you’re needing to call for help from somewhere out in the empty void of space, you might want to try texting. Unless you’re a black hole.
