The planet that hums by Robert Coontz from “New Scientist” September 11, 1999
THEY LIVE UNDERGROUND
They are everywhere but seem to come from nowhere. They barely exist, but never leave. If sounds have shadows, they are the shadows of a sound.
Researchers call them the background free oscillations of the Earth. But last year, when a pair of Japanese geophysicists named Naoki Suda and Kazunari Nawa dredged them out of a mass of seismic data, some people called them a hum. That’s a comforting thought: a mystic Om, perhaps, or just the warm, cozy sound of a planet going about its business.
What’s peculiar about the notes in the Hum is that they have no obvious source. Not earthquakes, not nuclear explosions, nothing. The vibrations triggered by cataclysmic events fade away to nothing, but the Hum continues, regardless.