No, there is no sound in space. At least, not in the way we traditionally understand sound on Earth. The misconception exists largely due to popular culture. Movies and TV shows often depict space battles with roaring rockets and booming exploding stars, but in reality, space is eerily silent.
The reason for this silence lies in the nature of sound itself. Sound is a vibration that travels through a medium, like air or water. For sound waves to propagate, they need particles. Space is a near-perfect vacuum, meaning it has very few particles. Without a medium for these sound waves, there is no sound.
NASA’s “Space Sounds”: Understanding Sonification
Despite the silence of space, there are videos and recordings labeled as “sounds from space” released by NASA. These are not sounds in the traditional sense. Instead, they are products of a process called sonification.
Sonification is the conversion of data into sound. In the context of space, instruments on spacecraft record electromagnetic vibrations or particle interactions. These signals, which are not audible, get converted into sound waves that we can hear. When scientists represent data in an auditory format, it makes certain patterns and anomalies easier to detect.
For instance, the eerie “whistles” and “howls” from recordings of Jupiter or Saturn aren’t sounds that an astronaut could hear. Instead, they are sonifications of radio waves or other electromagnetic phenomena detected by spacecraft.
Gravitational Waves: A Type of Sound in Space
The groundbreaking discovery of gravitational waves adds a new layer to our understanding of “sounds” in space. Detected by the Laser Interferometer Gravitational-Wave Observatory (LIGO), these are ripples in spacetime caused by cataclysmic events, like the merging of two black holes.
Now, gravitational waves aren’t sounds in the traditional sense. They don’t propagate through air or water; they literally stretch and compress the fabric of the universe. However, much like the sonifications mentioned earlier, scientists often convert gravitational wave data into sound.
When scientists at LIGO do this, the results are astounding. The final moments of two black holes spiraling into one another can be “heard” as a chirp. In this context, these gravitational waves are akin to the universe’s symphony, a testament to the colossal events unfolding in the cosmos.
Sound in Space: Can You Hear Sound on the Moon?
Similar to the vastness of space, the Moon is also an environment where sound doesn’t propagate in the traditional manner. The Moon has an extremely thin atmosphere or exosphere, which consists of very few particles. Because of this near-vacuum condition, there’s no medium for sound waves to travel through on the Moon’s surface. So, if an astronaut shouts on the Moon without any equipment, the sound doesn’t travel. Another astronaut standing a distance can’t hear it.
How Astronauts Talk on the Moon
Given the lack of an effective medium for sound transmission on the Moon, you might wonder how astronauts communicate with each other. Astronauts wear helmets that are part of a sealed system, connected to their spacesuits. Inside these helmets, there’s an atmosphere – usually a mix of oxygen and other gases – which transmits sound. When an astronaut speaks, the sound waves travel through the air inside the helmet, reaching a microphone. This microphone then converts the sound into an electrical signal, which transmits the signal to the communication systems of other astronauts or to mission control on Earth.
Any vibrations caused by an astronaut’s activities on the Moon are felt through their spacesuit. If an astronaut taps on another’s helmet, the latter “hears” it through the vibrations conducted by their spacesuit and helmet.
The Mysterious Music of Apollo
During the Apollo 10 mission, astronauts reported hearing a strange “whistling” sound, which some described as “outer-space-type music,” while they were orbiting the dark side of the Moon. This event remained classified until 2008 and spurred numerous speculations and theories.
However, the source of this “music” wasn’t extraterrestrial. The sounds were likely radio interference between the lunar module and the command module of the spacecraft. When two radios are close to each other and set to similar frequencies, they produce a whistling sound due to interference. This phenomenon, while eerie in the context of space exploration, is quite common and has a straightforward scientific explanation.
Sound on Mars
Mars has a very thin atmosphere composed mainly of carbon dioxide, with traces of nitrogen and argon. This atmosphere is about 100 times less dense than Earth’s. The atmospheric pressure at the Martian surface averages 0.6% of Earth’s sea level pressure. Such a tenuous atmosphere significantly affects the way sound travels on Mars compared to Earth.
Sound travels through the movement of particles in a medium, be it solid, liquid, or gas. The speed and character of sound waves are influenced by the properties of this medium. Given Mars’ thin atmosphere, sound travels slower than it does on Earth. Additionally, the composition of the Martian atmosphere means that certain frequencies, especially higher ones, get absorbed more quickly and do not travel as far.
In practical terms, this means that sounds on Mars are quieter and muffled than we’re used to. High-pitched noises are particularly hard to hear. If you were to have a conversation on Mars without the aid of communication equipment, voices would sound different, and you’d need to be much closer to the source of a sound to hear it clearly.
Are Wind and Dust Storms Silent?
Mars has frequent wind events and massive dust storms. But would a human standing on the Martian surface hear these?
Wind on Mars, even during a strong gust, sounds very faint. Given the thin atmosphere, there simply aren’t enough particles colliding with one another to produce a sound as loud as on Earth.
The massive dust storms that engulf the entire planet are visually impressive, but are surprisingly quiet. The movement of the fine dust and the thin atmosphere does not generate the roaring sounds we associate with storms on Earth. Instead, you might hear a soft hiss or a very low rumble, but it would be much subtler than one might expect.
References
- Abbott, R.; et al. (29 June 2021). “Observation of Gravitational Waves from Two Neutron Star–Black Hole Coalescences”. The Astrophysical Journal Letters. 915 (1): L5. doi:10.3847/2041-8213/ac082e
- Everest, F. (2001). The Master Handbook of Acoustics. New York: McGraw-Hill. ISBN 978-0-07-136097-5.
- Kinsler, L.E.; Frey, A.R.; Coppens, A.B.; Sanders, J.V. (2000). Fundamentals of Acoustics (4th ed.). New York: John Wiley & Sons. ISBN 0-471-84789-5.
- Maurice, S.; et al. (2022). “In situ recording of Mars soundscape:. Nature. 605: 653-658. doi:10.1038/s41586-022-04679-0