Washington, April 17 : Seismologists have detected a subtle and mysterious global hum, known as "Love waves", by studying records from some of the Earth's most uninteresting seismic stations.
According to a report in Discovery News, the newfound vibration is made of two-minute to five-minute, side-to-side surface seismic waves.
They are named for the British mathematician Augustus Edward Hough Love, who created the mathematical model of such waves in 1911.
The Love wave is a mode that essentially torques the Earth's north and south hemispheres against each other.
"It's as if the planet is dancing the Twist," explained Rudolf Widmer-Schnidrig of the Black Forest Observatory in Wolfach, Germany, and the Institute of Geophysics at the University of Stuttgart. "This gentle, faint twisting is called the "toroidal" mode," he added.
All of the planet's natural oscillations have signatures, or "modes" of vibration, depending on where and how they are created by earthquakes, ocean waves or other forces. hat's why among the suspects for making the Love wave hum are winds, ocean waves or even the sun.
The new detection comes 10 years after seismologists first identified louder global oscillations that resemble the ringing of a gigantic bell.
This oscillation is known as Earth's roaring spheroidal ring, which is a far more powerful oscillation that actually warps the shape of the planet like waves on a water surface.
On the other end of the spectrum is the newfound toroidal Love wave hum, which moves the Earth's surface a mere millionth of a meter every five minutes and dissipates less than 500 watts of energy.
"In other words, with the power needed by 10 light bulbs you could keep up the hum worldwide," said Widmer-Schnidrig. "This is unbelievable, I know. But maybe it lets you appreciate the minuscule amplitude of this oscillation," he added.
As for what creates the 500-watt undulations, it's still a matter of speculation.
According to geophysicist Toshiro Tanimoto of the University of California at Santa Barbara, "Perhaps winds exert shearing forces on the solid Earth, when an air mass hits a mountain range, for instance - or perhaps long-period ocean waves hitting the undersea walls at continental shelves are generating horizontal forces." It could even be caused by the sun, as oscillations in the sun may be picked up by Earth's geomagnetic field and cause Earth to hum a solar tune.