Sound Cannot Travel In Space

The classic, silent explosions in space depicted in some science fiction films are actually more accurate than their noisy counterparts. Sound as we know it is a mechanical wave, a vibration that travels by bumping molecules into their neighbors (Review). In the near-perfect vacuum of space, there are vast distances between particles, leaving no medium through which these vibrations can propagate. Without air, water, or another substance to carry them, sound waves simply cannot exist, rendering the cosmos an utterly silent place to the human ear.

However, this doesn't mean the universe is without its own form of music. Scientists use a process called 'sonification' to translate invisible data into audible sound, allowing us to listen to the cosmos. For instance, the supermassive black hole at the center of the Perseus galaxy cluster creates immense pressure waves as it expels energy into the surrounding hot gas. These ripples are a true sound wave, but one with a frequency far too low for us to hear. By analyzing X-ray data, NASA astronomers identified its fundamental note: a B-flat, an astonishing 57 octaves below middle C. To make it audible, they had to raise its pitch quadrillions of times, revealing the deep, persistent hum of a galactic giant.