Scientists record Earth's mystery hum but can't explain what it is

Scientists have finally recorded the sound of the Earth.

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Experts have been trying to record the hum for over half a century but have only tried using seismometers on land.

Researchers have now captured the hum using seismic instruments at the bottom of the sea.

If you're sitting at home trying to listen to the Earth's hum, although it's constant, you won't be able to hear it.

That's because the Earth hums at a frequency of 2.9 millihertz. Think about being at a nightclub. When you hear that base pounding, the lowest possible frequency you can hear is 20 hertz. Therefore, 2.9 millihertz is approximately 10,000 times smaller than the lowest frequency humans can hear.

Even though scientists have a recording of the hum, they still don't know what causes it.

The hum is defined as the Earth contracting every few minutes but there are multiple theories as to why the sound is created. Although we can imagine at any point Earth will be coming into labour whatever the cause of the hum is, scientists believe understanding it will allow them to really understand what is happening below the surface.