The magnetic field that cocoons Earth, shielding us from the sun’s most dangerous rays, has not always been so stable. About 41,000 years ago, that protective field weakened to a mere flicker of its usual strength. And then, the poles flipped. For a brief moment in geological time, north became south. Now, for the first time, you can hear the sound of that upheaval.

Scientists at the Technical University of Denmark and the German Research Centre for Geosciences have transformed this ancient disruption, known as the Laschamp event, into something you can experience with your ears — a soundscape built from the movements of Earth’s magnetic field lines. The result is unsettling, almost otherworldly. It’s a window into a distant past when the Earth’s magnetic shield faltered and exposed the planet to forces from space.

A Field in Flux

Most of us don’t think much about the magnetic field unless we’re lost in the woods and pulling out a compass. But deep beneath our feet, molten metal churns in the planet’s core, creating this invisible force field. It stretches thousands of kilometers into space, forming a barrier that protects our atmosphere from solar radiation.

Earth’s magnetic field is not fixed. In fact, it is always shifting. Over the past 200 years, the field has weakened by about 9% globally, according to NASA. But this is just a blip on a much longer time scale. “Paleomagnetic studies show the field is actually about the strongest it’s been in the past 100,000 years, and is twice as intense as its million-year average,” NASA notes.

However, there have been times in Earth’s history when this magnetic shield was significantly weaker. During those times, more cosmic radiation penetrated our atmosphere. The Laschamp event, which occurred around 41,000 years ago, is one of the most striking examples.

During this event, the magnetic poles reversed. As it reversed, the field lines — those invisible loops that guide everything from compass needles to migrating birds — pointed the wrong way.

“In terms of geological time scales, that is very fast,” explained Norbert Nowaczyk, a researcher at the German Research Centre for Geosciences.

According to the German Research Centre for Geosciences, this reversal lasted only 250 years. However, the weakened magnetic field persisted for about 440 years before returning to its usual strength. Earth’s surface was bombarded by harmful cosmic rays — the proof is in the traces left in ice cores and ocean sediments in the form of beryllium-10 isotopes.

The Laschamp event has also been linked to the extinction of megafauna in Australia and changes in human behavior, including using caves as shelters. However, this remains controversial.

The Sound of a Magnetic Reversal

While the Laschamp event has been known to scientists for decades, a new effort has brought this ancient phenomenon to life in an unexpected way — through sound. By using data collected from the European Space Agency’s (ESA) Swarm satellite mission, the team has created a “sounded visualization” of the Earth’s magnetic field during this event.

The scientists transformed the movement of magnetic field lines into sound by combining the data with natural noises like wood creaking and rocks crashing. The result is an eerie, otherworldly soundscape. “The process of transforming the sounds with data is similar to composing music from a score,” the researchers explained.

This unnerving soundscape is designed to evoke and capture the disruption of Earth’s magnetic field during the Laschamp event.

What About Today?

Today, scientists are keeping a close eye on Earth’s magnetic field. One area of particular interest is the South Atlantic Anomaly, a region where the field is unusually weak. Some researchers wonder if this could signal an impending magnetic reversal. But so far, there is no direct evidence linking this anomaly to a future flip.

Since 2013, ESA’s Swarm satellites have been measuring magnetic signals from various parts of Earth. Focus areas include the core, mantle, and crust, as well as the oceans, ionosphere, and magnetosphere. This data helps scientists better understand the complex dynamics of Earth’s magnetic field and should offer early warning of an impending pole reversal.

While any potential magnetic field flip is likely still thousands of years away, the consequences could be significant, especially for modern technology. A weaker magnetic field would provide less protection against the solar wind and cosmic rays, according to Monika Korte, a geomagnetic expert at GFZ Potsdam. Compasses would lose accuracy, and satellites that handle telecommunications or monitor weather could experience disruptions.

However, Korte reassures that Earth’s atmosphere would still shield humans and animals from harmful radiation. But, she notes, effects typically seen during strong geomagnetic storms, such as satellite damage, communication issues, and increased radiation on long-distance flights and the International Space Station, could become more frequent during even moderate solar activity.