Is There Such a Thing as a Planet Sound

Can a planet make a sound? Its an interesting question that gives us insight into the nature of sound waves. In a sense, planets do emit radiation which can be used to make sounds we can hear. How does that work? The Physics of Sound Waves Everything in the universe gives off radiation that — if our ears or eyes were sensitive to it — we could hear or see. The spectrum of light that we actually perceive is very small, compared to the very large spectrum of available light, ranging from gamma-rays to radio waves. Signals that can be converted to sound make up only one part of that spectrum. The way people and animals hear sound is that sound waves travel through the air and eventually reach the ear. Inside, they bounce against the eardrum, which begins to vibrate. Those vibrations pass through small bones in the ear and cause small hairs to vibrate. The hairs act like tiny antennae and convert the vibrations into electrical signals that race to the brain through the nerves. The brain then interprets that as sound and what the timbre and pitch of the sound are. What About Sound in Space? Everyone has heard the line used to advertise the 1979 movie Alien, In space, no one can hear you scream. Its actually quite true as it relates to sound in space. For any sounds to be heard while someone is in space, there have to be molecules to vibrate. On our planet, air molecules vibrate and transmit sound to our ears. In space, there are few if any molecules to deliver sound waves to the ears of people in space. (Plus, if someone is in space, theyre likely to be wearing a helmet and a spacesuit and still wouldnt hear anything outside because theres no air to transmit it.) That doesnt mean there arent vibrations moving through space, only that there are no molecules to pick them up. However, those emissions can be used to create false sounds (that is, not the real sound a planet or other object might make). How does that work? As one example, people have captured emissions given off when charged particles from the Sun encounter our planets magnetic field. The signals are at really high frequencies that our ears cant perceive. But, the signals can be slowed down enough to allow us to hear them. They sound eerie and weird, but those whistlers and cracks and pops and hums are just some of the many songs of Earth. Or, to be more specific, from Earths magnetic field.   In the 1990s, NASA explored the idea that emissions from other planets could be captured and processed so people could hear them. The resulting music is a collection of eerie, spooky sounds. There is a good sampling of them on NASAs Youtube site.  These are literally artificial depictions of real events. Its very similar to making a recording of a cat meowing, for example, and slowing it down to hear all the variations in the cats voice. Are We Really Hearing a Planet Sound? Not exactly. The planets dont sing pretty music when spaceships fly by. But, they do give off all those emissions that Voyager, New Horizons, Cassini, Galileo, and other probes can sample, gather, and transmit back to Earth. The music gets created as the scientists process the data to make it so that we can hear it.   However, each planet does have its own unique song. Thats because each one has different frequencies that are emitted (due to different amounts of charged particles flying around and because of the various magnetic field strengths in our solar system). Every planet sound will be different, and so will the space around it.   Astronomers have also converted data from spacecraft crossing the boundary of the solar system (called the heliopause) and turned that into sound as well. Its not associated with any planet  but does show that signals can come from many places in space. Turning them into songs we can hear is a way of experiencing the universe with more than one sense.   It All Began With Voyager The creation of planetary sound started when the Voyager 2 spacecraft swept past Jupiter, Saturn, and Uranus from 1979 to 1989.  The probe picked up electromagnetic disturbances and charged particle fluxes, not actual sound. Charged particles (either bouncing off the planets from the Sun  or produced by the planets themselves) travel in the space, usually kept in check by the planets magnetospheres. Also, radio waves (again either reflected waves  or produced by processes on the planets themselves) get trapped by the immense strength of a planets magnetic field. The electromagnetic waves and charged particles were measured by the probe and the data from those measurements were then sent back to Earth for analysis. One interesting example was the so-called Saturn kilometric radiation.  Its a low-frequency radio emission, so its actually lower than we can hear. It is produced as electrons move along magnetic field lines, and theyre somehow related to auroral activity at the poles. At the time of the Voyager 2 flyby of Saturn, the scientists working with the planetary radio astronomy instrument detected this radiation, speeded it up and made a song that people could hear.   How Do Data Collections Become Sound? In these days, when most people understand that data is simply a collection of ones and zeroes, the idea of turning data into music isnt such a wild idea. After all, the music we listen to on streaming services or our iPhones or personal players is all simply encoded data. Our music players reassemble the data back into sound waves that we can hear.   In the Voyager 2 data, none of the measurements themselves were of actual sound waves. However, many of the electromagnetic wave and particle oscillation frequencies could be translated into sound in the same way that our personal music players take data and turn it into sound.  All NASA had to do was to take the data accumulated by the  Ã¢â‚¬â€¹Voyager probe and convert it into sound waves. Thats where the songs of distant planets originate; as data from a spacecraft.