Caspar Henderson writes:

Old stories about the Northern Lights, or aurora borealis, show the full play of human imagination at work across the sky. In Greenland some said the lights were the spirits of children who had died at birth but were now dancing in the heavens. Others said they were made by spirits playing ball with the skull of a walrus—or by walrus spirits kicking around human skulls. To the Algonquin people of eastern Canada, the lights were the reflection of fires lit by their creator, Nanabozho, to remind them that they are in his thoughts. In Finland they are still known as “fox fires” after a mythical fox whose tail sparks colorful flames in the sky as he runs across a snowy landscape.

A scientific account of auroras links our imaginations to the vastness of space and the irreducible strangeness of matter. They occur when charged particles of the solar wind streaming across tens of millions of miles of empty space from the sun are drawn down along the lines of the Earth’s magnetic field where it is nearly vertical at the poles. Here, 100 kilometers (62 miles) or so above our heads, the particles excite air molecules which then shed their excess energy in the form of light: green or red for oxygen, blue or purple for nitrogen.

More puzzling are reports of the aurora making sounds. The explorer Knud Rasmussen wrote in the early 20th century that the Inuit sometimes heard whistling, rustling, and other sounds as it played across the sky. According to their legends, he added, if you returned the whistle the light might come nearer and even dance for you. Some Europeans reported hearing the noises, too. In an account of travels in Lapland published in 1827, the naturalist Sir Arthur de Capell Brooke described one such occasion. “The lights were … very bright and exceptionally fast in motion … The night was perfectly calm and quiet and I thought I heard a crackling sound … coming from [their] direction.” Other accounts over the years compare the noise to the swish or rustle of a silken skirt, the sizzle of bacon in a hot pan, a flock of birds, and even to the crack of a rifle being fired.

For a long time many researchers dismissed these reports. Auroras occur far too high up for any sounds they might make to be audible on the ground, so there could be no sound. But in 1990 a young acoustic scientist had an experience that helped change that. [Continue reading…]