Earth's magnetic field It is an invisible force, but essential to life as we know it. It protects us from solar radiation, influences navigation systems, and holds within its variations a fascinating history full of mysteries, theories, and myths that have intrigued scientists for centuries. To learn more about its protective function, you can read about the cosmic shield of the magnetic field.
Even if we don't see it, it's always present. From the first Chinese compasses to modern satellites, the study of the geomagnetic field has been fundamental to understanding our planet and its climatic, geological, and biological history. But where does this field really come from? Can its changes influence the climate or cause catastrophes? In this article, we'll unpack all these topics with a scientific basis and without falling into conspiracy theories.
What is the Earth's magnetic field and how does it originate?
El terrestrial magnetic field (also known as the geomagnetic field) is a region of space dominated by magnetic forces generated within the Earth's core. Although for centuries it was thought that there was a large magnet at the center of the planet, today it is known that This field is a product of the movement of liquid metals in the outer core, mainly iron and nickel. For a more detailed explanation of how they work, see What is the Earth's magnetic field and how does it work?.
This phenomenon is known as dynamo effectBroadly speaking, the heat of the core causes convective motions in the molten iron, which, along with the Earth's rotation, generates electric currents. These currents, in turn, produce the magnetic field. It's a complex process, comparable to the operation of a bicycle dynamo, but on a planetary scale.
This field has a structure of dipole (two poles: north and south) that resembles a traditional magnet. However, it is not perfectly aligned with the Earth's rotational axis, and the magnetic poles shift over time. Currently, the magnetic north pole is moving from Canada toward Siberia at an accelerated rate.
Components and structure of the field
The Earth's magnetic field is not uniform. It can be divided into three major components:
- Internal field: generated in the outer core, represents more than 90% of the total field.
- External field: influenced by interactions with the solar wind, gives rise to the magnetosphere.
- Local anomalies: caused by magnetic rocks in the Earth's crust, useful in archaeology or geology.
Its shape is affected by the solar wind, so instead of being spherical, the magnetosphere is teardrop-shaped. It is compressed on the side facing the Sun and extends like a tail in the opposite direction. To better understand these interactions, you can read about How the Sun affects the Earth's magnetic field.
Geomagnetic reversals: when and why do they occur?
Throughout geological history, The Earth's magnetic field has changed direction multiple timesThis phenomenon, called polarity reversal, occurs when the north and south magnetic poles swap. It doesn't happen immediately, but can last for thousands of years.
The last known complete reversal occurred approximately 780.000 years ago (the Brunhes-Matuyama event). The so-called geomagnetic excursions, such as the Laschamps earthquake 42.000 years ago, when the field suddenly dropped in intensity and the poles temporarily reversed for a few centuries, before returning to their original position. To learn more about these reversals, see What happens when the Earth's magnetic poles are reversed?.
Do these investments affect the climate or life?
Although many theorists have tried to link these investments with events such as mass extinctions, ice ages, or drastic climate changes, current scientific evidence does not strongly support it.
The most recent study of the Laschamps excursion suggests that it may have coincided with a collapse of the magnetic field, which would have allowed for increased solar and cosmic radiation, affecting the ozone layer and altering weather patterns. However, other scientists, such as NASA's Gavin Schmidt, point out that No direct and conclusive connection has been found between magnetic reversals and global climate change..
Even over the past 2,8 million years, there is no clear evidence linking geomagnetic excursions to significant climate changes. For a deeper look into the potential consequences of climate change, see What are the consequences of the Sun's magnetic field being about to reverse?.
The magnetosphere: shield of life
One of the most important functions of the magnetic field is that It works as a shield against cosmic radiationIt deflects charged particles from the sun and deep space, protecting our atmosphere, especially the ozone layer.
When these particles collide with the atmosphere, they generate visually spectacular phenomena: the northern and southern lightsAlthough beautiful, they are the result of an energetic interaction that, without the magnetic field, could be detrimental to life. For more information on how these auroras form, visit how the northern lights are produced.
The role of the magnetic field in navigation and human history
For over 2.000 years, civilizations have used the Earth's magnetism for navigation. The magnetic properties of minerals such as magnetite were already known in China. Later, figures such as William Gilbert in the XNUMXth century helped consolidate the idea of the Earth as a large spherical magnet.
The compass, which points to magnetic north, has been essential for exploration, trade, and geography. However, since magnetic north does not coincide with geographic north, the concept of magnetic declination to adjust measurements, which is crucial even today, especially in the event of a digital system failure. You can learn more about the importance of this phenomenon in navigation in the article on the Earth's magnetic field.
Myths and conspiracy theories about the magnetic field
Multiple theories without scientific basis have circulated on social media claiming that changes in the magnetic field cause catastrophes, extinctions, or are even behind current climate change. One of these theories is known as "The Story of Adam and Eve," proposed by Chan Thomas in 1965 and recently revived on platforms like TikTok.
This theory suggests that Geomagnetic reversals caused the extinction of entire civilizations and that we are facing an imminent event. However, the scientific community rejects these ideas for lacking rigorous foundation.
According to experts, the Earth has natural mechanisms that continue to protect life even during a pole reversal. The atmosphere, for example, continues to block much of the radiation, even if the magnetic field is weakened. To learn more about how the magnetic field works and its effects, see the article on Space hurricanes and the magnetic field.
Scientific importance and practical applications
The study of the magnetic field not only serves to understand the past, but also has modern applications in archaeology, mining and even climatologyMagnetometry is used to detect mineral deposits or buried structures by means of the small disturbances they cause in the Earth's magnetic field.
Furthermore, the magnetic recording in rocks or sediments It allows us to establish geological chronologies and study tectonic shifts, providing key data on the evolution of the Earth and its continents. Through advances in the study of the atmosphere, many of our planet's secrets have been deciphered.
Thanks to missions like the Swarm satellites launched by the European Space Agency, we have detailed information on field variations, allowing us to accurately update the global magnetic model.
The Earth's magnetic field is, without a doubt, a key element in understanding both the current functioning of the planet and its history. Its origin, based on complex internal movements of the core, generates a dynamic structure, capable of inverting and varying over time, yet with an essential protective function for life. Although its study still presents unknowns, scientific advances have allowed many myths to be debunked. Today we can affirm that, far from being a sign of catastrophe, the changing behavior of the magnetic field is another reflection of the active life of our planet.
