Source of Earth's Hum Revealed, Space Symphony Possible By Robert Roy Britt Senior Science Writer posted: 10:18 am ET 26 March 2000 출처-http://www.space.com/scienceastronomy/planetearth/space_symphony_000323.html Competing with the natural emissions from stars and other celestial objects, our Earth sings like a canary -- it drones on in a constant hum of a gazillion notes. 별과 다른 천..