What Makes The Earth Hum? Planet Earth emits a low, continuous hum, consisting of different frequencies, all below the range of human hearing. The hum can only be detected by seismometers, and exists even when no earthquakes are occurring. Scientists are not yet sure what causes this, but several theories have been offered.
A California scientist thinks variations in atmospheric pressure over the Earth’s surface produce the hum. As air pressure rises, it pushes down against the surface, and the surface rebounds as the pressure drops, similar to a gong being stuck softly by rubber mallets. The resulting vibrations produce the frequencies that make up the hum. Using data from 15 seismographic stations around the world, over a number of years, he also found that the hum is about 10% louder in winter, when air pressure is higher.
Another theory says the hum is background noise made by waves moving across the ocean floors. The action of waves at the surface results in a thumping wave on the bottom that creates the hum.
Others think the hum is caused by the energy of the pounding surf against the world’s coastlines, causing vibrations in the Earth’s crust. Researchers worldwide continue to gather data and make speculations.
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