It turns out the Earth can speak — in the form of chirps and whistles caused by radio waves audible to the human ear, and emitted by the Earth's magnetosphere. It's called a "chorus," or "dawn chorus."
Scientists have known about the phenomenon for some time, as it can be picked up just by using radio receivers. It's most easily picked up in the mornings and that — combined with the signature chirping noise — is what earned it the nickname of the "dawn chorus."
What causes it? These audible radio waves are emitted by energetic particles within the magnetosphere, a phenomenon that surrounds any planet or moon with an intrinsic magnetic field, like Earth. These particles affect (and are affected by) the radiation belts that also surround the planet, creating the unique noises.
This recent recording comes courtesy of NASA's twin Radiation Belt Storm Probe (RBSP) satellites launched at the end of August. They captured five separate occurrences of the phenomenon on September 5, using the RBSP's Electric and Magnetic Field Instrument Suite and Integrated Science (EMFISIS) instrument, and are strung together as one continuous recording.
The RBSP mission was to place a pair of identical satellites into eccentric orbits, travelling as low as 375 miles to 20,000 miles above the Earth. The satellites will follow one another through these orbits and their trip will bring them through the stable, inner Van Allen radiation belt as well as the less predictable outer one.
The satellites' job will be to investigate the various particles that make up the radiation belts and chart activity in discreet locations along the way.
Fortunately for the world, the EMFISIS team at the University of Iowa and NASA's Goddard Space Flight Center were able to create this recording of the Earth's chorus for us all to hear.
Don't you wish there were a translator that could tell us what the chorus is saying?
Audio Credit: University of Iowa; Visualisation Credit: NASA/Goddard Space Flight Center.