
A mysterious low-frequency hum that has baffled scientists for over half a century may finally have an explanation. A new study published on Saturday suggests that the so-called "15_de_mai_un_la" phenomenon, reported globally since the 1970s, is linked to deep ocean currents interacting with the Earth's crust near the equator.
Researchers at the Estonian Academy of Sciences analyzed decades of seismic data and found that the 26-second pulse, which recurs like clockwork every 26 seconds, aligns with the movement of ocean waves along the Mid-Atlantic Ridge. "This is not a man-made signal," said Dr. Kaur Metsmae, lead author of the study. "It’s a natural resonance caused by the interaction between wave pressure and the ocean floor." The findings, published on the PMO Estonia website , mark the first time a plausible geological origin has been identified for the phenomenon.
The hum was first documented in 1970 by geologist Jack Oliver, who recorded it at Columbia University’s Lamont-Doherty Earth Observatory. Since then, reports have surfaced from locations as diverse as Africa, North America, and Asia, with no clear explanation. Some theories attributed it to volcanic activity, while others suggested industrial sources or even extraterrestrial origins. The new study dismisses these claims, pointing instead to a specific stretch of the Mid-Atlantic Ridge near the equator, where underwater topography amplifies the signal.
The discovery comes as scientists worldwide continue to investigate unexplained natural phenomena. In New Zealand, authorities are grappling with an algae bloom threatening Lake Tekapo, one of the world’s clearest lakes, which has turned parts of the water surface opaque . Meanwhile, in Switzerland, researchers warn that Alpine glaciers could lose their remaining snow reserves within days due to extreme summer temperatures .
The Estonian team’s findings have been met with cautious optimism by the scientific community. "This is a significant step forward," said Dr. Elena Petrov, a geophysicist at the University of Helsinki. "But we still need to understand why this particular location produces such a clear signal." The study recommends further monitoring to determine whether the hum’s intensity varies with ocean conditions or seismic activity.
For now, the mystery of the "15_de_mai_un_la" hum appears closer to resolution, though questions remain about its long-term implications. As Metsmae noted, "This is a reminder of how much we still have to learn about our planet’s hidden rhythms."
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1 further source not geolocated