Geek Trivia: Low and behold

“According to scientists, Julie Andrews was right: The hills are alive with the sound of music. Okay, so maybe music is a generous term for the phenomenon, but the hills really are making noise, as is the entire planet Earth. You just can’t hear it because the Earth’s natural hum is subsonic, occurring at a frequency far below the range of the human ear.

Scientists first discovered the Earth’s hum–technically referred to as background-free oscillation–while sorting through seismic data. They couldn’t attribute a significant percentage of this “ground sound” to recognized seismic activity, meaning that the Earth itself wasn’t moving–something was moving the Earth.

Seismologists eventually realized that the atmosphere was actually pushing and pulling against the planet, creating subsonic noise beyond the normal rumble of seismic activity. Put simply, the air is “playing” the planet like an instrument, creating a distinct hum.

The hum changes throughout the course of the year, suggesting a seasonal and therefore thermal origin of the atmospheric pressures fueling the Earth’s hum. As the changing seasons heat and cool the air, the atmosphere expands and contracts accordingly, changing the placement and intensity of pressure exerted against the earth, resulting in a change in volume of the Earth’s hum.

Given the parameters of this phenomenon, it’s very likely that the other planets in the solar system possessing an atmosphere also have unique, cyclical hums. As such, Mars and Venus are probable candidates for planetary hums.

If it’s true, that means a cosmic symphony of planetary tones is playing in our solar system even as we speak. We just can’t hear it because the oscillations are simply too low in frequency.

Still, don’t think that the planets have the market cornered on low-frequency sound. In 2003, scientists discovered that a nonplanetary celestial object was emitting the lowest-frequency note ever detected.