The Earth makes a mysterious humming sound, and for the first time, it has been recorded in the ocean floor.

The Earth's hum, however, remains one of the world's most intriguing mysteries. While there have been several theories, scientists have still not identified the source of the phenomenon.

Scientists Baffled By The Humming Earth

The Earth's hum has interested scientists since 1959, but the phenomenon was only proved in 1998.

The planet continues to create a steady sound that is inaudible to the human ear, despite various claims by people that they have actually heard it.

The mysterious sound may be the key to unlocking some of the secrets of the Earth, but while the humming sound has been recorded on numerous occasions, scientists still have no definite answer on where it is coming from and what is causing it.

The Earth's Hum On The Ocean Floor

A team of European geophysicists, in a study that was published in November in the Geophysical Research Letters journal, claimed that they were able to record the Earth's hum from the bottom of the ocean for the first time. They installed seismometers at the Indian Ocean's floor to make the observations.

By recording the first instance of the Earth's hum from the ocean floor, the researchers were able to significantly expand the avenues through which the phenomenon can be studied, considering that water makes up 70 percent of the planet.

In addition, the researchers were able to figure out how to get a clear recording of the Earth's hum in the ocean floor, which is no easy feat due to the constant motion of the ocean and its inhabitants. The team needed to gather signals from several seismometers and filter out all the other noise that were picked up.

Where Does The Earth's Hum Come From?

The planet's vibrations, or free oscillations, hovers at a frequency of between 2.9 and 4.5 millihertz, which is 10,000 times lower than what the human ear can pick up.

Theories on the oscillations have proposed that they are caused by the pounding of ocean waves that make the Earth vibrate like a bell, atmospheric turbulence, or for conspiracy theorists, secret military operations in the form of submarine activity. There have even been claims that the Earth's hum is caused by a project that is tunneling under the Earth, or the presence of aliens.

However, after years of studying and recording the Earth's hum, scientists may finally be inching closer to an explanation to put the outrageous theories to rest.