sciencesoup:

Symphony of the Universe

After my radio astronomy article yesterday, I thought I should expand on the idea of “sound” in space—how, after all, can stars and galaxies make noise? Sound waves only travel through a medium, such as solid, liquid or gas, by making their molecules vibrate and creating a compression wave. When there is no medium, there’s no sound—hence why the near-vacuum of space is almost completely silent. In the 90s, NASA released an album called “Symphonies of the Planets”, but the sounds weren’t exactly of the planets: they were converted from measurements of the interactions of electromagnetic disturbances, such as charged particles in the planets’ magnetospheres or trapped radio waves. Electromagnetic waves, such as radio waves or light, don’t need a medium to travel like sound waves do. They’re composed of both electric and magnetic waves and so they’re self-propagating, because the oscillating electric field creates an oscillating magnetic field which then creates an oscillating electric field and so on, and the continued disturbances keep the wave moving forward. It’s not until they’re captured here on Earth that they’re converted into sound, and we can hear the symphony of the universe.