You may not have heard it, but the Earth is always humming and scientists have finally managed to capture its elusive sound hidden beneath the ocean. This hum has long intrigued the scientific community, and in 1959 researchers attempted to explain it, without much success. However, in 1998 scientists finally published work proving that Earth emits a humming sound and through the use of technology scientists have been working hard to try and find out just why this is occurring.
Every moment of the day the Earth both expands and contracts, although this is so subtle that no one can feel these free oscillations, as they are called. It is these oscillations that can be detected in hums or vibrations despite there being no seismic activity of any kind around, according to ScienceAlert.
While 1998 may have been a momentous year in proving that the Earth’s humming sound was indeed real, this was only shown by the use of seismometers which had to be used while on land. Now, scientists have detected the Earth’s hum under the ocean. This is a considerably important moment in understand this humming sound as 70 percent of the Earth is comprised of water.
There have been many theories about what could be creating this humming sound that the Earth emits, with one of them suggesting that these oscillations might come about it because of the heavy moments of the waves as they hit the ocean floor. Studies have shown that this hypothesis is certainly a feasible one.
Another theory is that the sound could be caused by atmospheric turbulence, especially as researchers noticed that the humming sound was much more powerful during storms in the wintertime in the northern part of the Pacific Ocean as well as in the southern oceans during their winter.
Because of these ideas of what may be causing the mysterious sounds, there have been seismometer stations built onto the floor of the ocean in numerous spots around the world to try and pick up acoustic humming sounds which might be triggered by the ocean.
To find out exactly where the hum was coming from, a team of researchers from the Paris Institute of Earth Physics extracted data that had been recorded over an 11-month period from 57 different seismometer stations located near Madagascar in the Indian Ocean.
Once scientists received the data, they then chose the top two stations which had the best quality of data to analyze and took care to disregard signals coming from things like currents on the seafloor and infragravity waves. After the extraneous data was removed, the remaining sound heard was that of the Earth’s hum.
Scientists then took this data and compared it with other data collected from stations measuring the sound on land, and found that the Earth has a natural hum which measures at frequencies of between 2.9 and 4.5 millihertz. If you’re wondering why we can’t hear it, the simplest explanation is that the hearing of humans begins at 20 hertz, which means that the hum of the Earth is 10,000 times below anything that we could ever hear naturally.
Interestingly, even though the sound did vary over time, it was not found to correspond with the changing of the seasons as had previously been thought might be the case. While there is still much work to be done in studying the sounds the Earth makes, having measuring stations both below the ocean as well as on land is helping scientists to have a much greater understanding of this phenomenon with so much data now available to work with.
The latest research detailing the humming of the Earth as captured beneath the ocean has been published in the Geophysical Research Letters.