Under extremely quiet conditions, you can actually hear the Southern Lights.

While observers have reported hearing the aurora for centuries, the phenomenon was long dismissed as an auditory illusion. In 2012, researchers from Aalto University in Finland, led by Professor Unto K. Laine, finally proved the existence of these sounds. Using three separate microphones at a research site in Sodankylä, they triangulated the source of the noise to a height of approximately 70 meters (230 feet) above the ground.The sounds are produced by a physical process involving the 'inversion layer' of the atmosphere. During calm, clear nights, a layer of warm air can become trapped above a layer of cold air near the surface. This inversion layer allows electrical charges from the aurora to accumulate. When a particularly strong solar storm occurs, these charges discharge rapidly, creating the pops, crackles, and hissing sounds reported by witnesses.This discovery was significant because the aurora itself occurs much higher up, typically between 90 and 150 kilometers (56 to 93 miles) above the Earth. At that altitude, the air is too thin to carry sound waves to the ground. The Aalto University study showed that the sound is a local atmospheric reaction to the geomagnetic activity rather than sound traveling from the aurora itself. This explains why the sound is heard simultaneously with the visual display despite the speed of sound being much slower than the speed of light.