You can hear explosions in space
Sound is a mechanical wave that requires a medium, such as air or water, to compress and expand as it travels. The vacuum of space contains far too few molecules for sound to propagate through it, making outer space effectively silent to human ears even during extremely violent events such as supernova explosions.
What we know
Popular depictions of space combat and cosmic events in film and television routinely feature dramatic explosion sounds, roaring engines, and other audible effects occurring in the vacuum of space, and this consistent cinematic convention, chosen for dramatic effect rather than scientific accuracy, has contributed to a persistent popular belief that sound genuinely can and does travel through space in the way it does through Earth's atmosphere.
Sound is fundamentally a mechanical pressure wave, produced when a vibrating source causes surrounding particles, whether in a gas, liquid, or solid medium, to alternately compress together and then spread apart in a repeating pattern, and this alternating compression and rarefaction propagates outward from the source as those particles collide with and displace their neighbors in turn, ultimately reaching a listener's ear, where it causes the eardrum to vibrate correspondingly, producing the sensation of hearing. This entire mechanism is fundamentally dependent on the presence of a sufficient density of matter, molecules or atoms close enough together to transmit that compression wave from one to the next.
Outer space, particularly the near-total vacuum found in the depths of interstellar and much of interplanetary space, contains an extremely sparse density of matter, often only a handful of atoms or molecules per cubic centimeter in interstellar space, compared to roughly ten thousand trillion trillion (10^19) molecules per cubic centimeter in Earth's atmosphere at sea level. This near-total absence of a transmitting medium means there simply are not enough particles present, or they are spaced far too widely apart, to sustain a mechanical pressure wave of the kind that constitutes sound, regardless of how energetically violent or explosive the source event might be. Even an event as extraordinarily energetic as a supernova, one of the most powerful explosions known to occur in the universe, releasing more energy in a brief period than an entire galaxy of ordinary stars, produces no sound in the everyday, hearable sense as it propagates outward through the vacuum, since there is no surrounding medium available to carry a pressure wave from the explosion to any distant observer.
This does not mean space is entirely without any wave phenomena at all; electromagnetic radiation, including visible light, radio waves, X-rays, and gamma rays, propagates perfectly well through a vacuum, since electromagnetic waves do not require a physical medium to travel, unlike mechanical sound waves, which is precisely why astronomers can observe and study distant cosmic explosions and other violent astrophysical events using telescopes sensitive to various parts of the electromagnetic spectrum, even though those same events would be entirely silent to a hypothetical unprotected human ear positioned nearby.
There is a genuine, scientifically legitimate nuance that is sometimes invoked, somewhat loosely, in connection with the "sound in space" question: astronomers have detected genuine, extraordinarily low-frequency pressure waves propagating through the hot, thin, but not perfectly empty gas that fills the space between galaxies within large galaxy clusters, most famously a specific, well-studied pressure wave detected emanating from the supermassive black hole at the center of the Perseus galaxy cluster. NASA has, for public engagement purposes, converted the pattern of this detected pressure wave into an audible frequency range and released it as a form of scientific sonification, but this is fundamentally an artistic and educational translation of scientifically real data into a hearable format for human audiences, not an indication that space is broadly filled with naturally audible sound in anything resembling the everyday sense, and NASA's own material describing this sonification project is careful to clarify this important distinction for public audiences.
Common claims
- Explosions in space produce audible sound like in movies.Not supported
- Sound needs a medium such as air or water to travel.Accurate
- Electromagnetic waves like light can travel through a vacuum.Accurate
- NASA has converted real pressure wave data from space into audible sound.Accurate, with clarified context