“Sound cannot travel through a vacuum”

The idea that sound cannot travel through a vacuum is a widely accepted scientific principle, largely because our everyday experience with sound relies on a medium like air. We perceive sound when vibrations create pressure waves that travel through particles, reaching our ears and being interpreted by our brains. Without these particles to transmit the vibrations, sound simply has no way to propagate. This fundamental understanding correctly leads to the conclusion that the vast emptiness of space, being a near-perfect vacuum, should be devoid of sound as we know it.

Scientifically, sound is defined as a mechanical wave, meaning it requires a medium—a collection of interconnected particles—to transfer energy through compressions and rarefactions. In Earth's atmosphere, air molecules are constantly colliding and passing these vibrations along. In the sparse environment of space, however, the particles are so far apart that such collisions are too infrequent to effectively transmit sound waves. This is why the iconic movie tagline, "In space, no one can hear you scream," resonates so strongly; it accurately reflects the physical reality of sound propagation.

However, the common belief can be slightly nuanced. While typical audible sound cannot travel in space, it's important to remember that space isn't an absolute vacuum. Regions like galaxy clusters contain extremely diffuse gas and plasma, which can technically carry sound waves. These "sounds" are at incredibly low frequencies, far below the range of human hearing, and are often amplified and translated from other forms of data (like X-ray emissions) to be perceived. Furthermore, recent scientific research has even demonstrated that sound can "tunnel" across microscopic vacuum gaps between specialized materials called piezoelectric crystals, though this occurs under very specific, engineered conditions and not through the vastness of interstellar (Review) space.