We all live inside an invisible field that permeates every cell of our bodies and affects global processes on Earth. Magic has nothing to do with it. It is only about our planet’s magnetic field and the dangers, mythical and real, that it can cause.
Compass hand
“The Earth’s magnetic field is weakening! The magnetic poles are shifting! The pole inversion is coming! Humanity is in danger!” Have you ever heard this? Almost certainly, even this year, you have listened to it.
We cannot see the magnetic field of our planet, but it permeates everything around us and plays an extremely important role in the existence of life on Earth. Therefore, any hint that there may be any danger from it will easily lead to panic.
And the best remedy for panic is to understand how a potentially dangerous thing works. With the magnetic field of our planet, this is not easy, but there is a great starting point. The compass hand. People have been using this device for hundreds of years and know that it always points north.
At the same time, a compass is by no means a magical artifact. To create one, you can take an ordinary metal needle, magnetize it, for example, by rubbing different ends on different sides of the magnet, and hang it on a string. It will always point to the pole, unless, of course, there is another magnet or a large piece of iron nearby.
However, if you imagine the Earth’s magnetic field as a huge number of magnetized needles suspended in different places, you will not be so wrong. But how does it arise?
Dynamo inside the Earth
The main principle to understand the magnetic field is this: the movement of electric charges generates a magnetic field, and the magnetic field causes charged particles to move. Together, this phenomenon is called electromagnetism. It has an incredibly large number of manifestations, but first of all, it is worth remembering that for a magnetic field as powerful as the Earth’s to arise, charged particles must move relative to conductors.
In the case of our planet, this movement occurs in the inner core, which is located in the very center of our planet, the outer core that surrounds it, and partially in the mantle that surrounds the first two.
The inner core contains a large amount of iron and nickel and is solid despite its temperature of about 5400°C. Its diameter is almost 2440 km. It is surrounded by an outer core that begins at a depth of 2890 km below the surface of our planet.
The outer core also contains a lot of iron and nickel, although there is also enough oxygen and sulfur. And this layer is no longer in a solid state, but is a viscous liquid. It can be compared to sour cream. You just have to remember that it exists at a temperature of about 4400°C and a tremendous pressure.
The material of the outer core is conductive. At the same time, the rotation speed of the inner core is slightly different from the rest of the planet. As a result, convective flows arise in the outer core, which are essentially the movement of charges. This process is quite complex, as it also involves such forces as friction at the boundary between the inner and outer cores, electric currents, heat and mass transfer to the outer layers, and many other factors. This model is called a geodynamo because its mechanism of action is similar to one of the simplest generators of electric current, a dynamo.
Manifestations of the Earth’s magnetic field
In the end, the result of this whole process is unambiguous – a giant magnetic dipole is formed. It can be visualized with the help of the already mentioned needles suspended on a thread. If you imagine a huge number of them, they will form closed arcs coming out of one magnetic pole and entering the other. These are called magnetic field lines of force and are quite imaginary. It is simply a visualization of the direction in which the forces caused by electromagnetism act. They are the ones that turn the compass needle in a certain direction.
Many centuries ago, people noticed that the compass arrow does not point exactly to the geographic pole of the Earth, which is well calculated by the movement of the celestial bodies, but somewhere slightly to the side of it. This means that the orientation of the dipole inside the Earth does not exactly coincide with the axis of our planet, and this is not surprising if we remember that it arises in a layer of dynamically moving fluid.
It is worth noting that the strength lines of the Earth’s magnetic field do not end above its surface. They stretch for many thousands of kilometers around the surface, and it is this part of them that is the most important for life on our planet. After all, it is there that they stop charged particles flying towards us from the Sun and other stars.
They can be partially absorbed by the planet’s atmosphere or, in the case of life hiding in the depths of the oceans, by the water column. But without magnetic fields, it would be difficult for them to cope with this task.
The aurora borealis is a vivid example of the power of the Earth’s magnetic field. They are powered by charged particles that have been caught by magnetic field lines and directed by them to the polar zones, where they enter the atmosphere. There, they interact with gas molecules that slow them down and convert the dangerous energy into visible light. The intensity of the aurora borealis demonstrates how much potentially life-threatening energy is intercepted and neutralized by the interaction of the magnetic field and the atmosphere.
Magnetic anomalies and pole motion
All of the above is just a simplified scheme of how the Earth’s magnetic field works. It is even more complicated due to the presence of magnetic anomalies. These are areas on Earth that generate their magnetic fields. For example, they are formed in areas of mid-ocean ridges where new crust is born. There, they look like bands parallel to the faults themselves.
Another large group of anomalies is those associated with underground magma flows. As already mentioned, the Earth’s outer core undergoes a complex redistribution of mass and energy, and some of it is transferred to the mantle, the layer that lies between the core and the crust of our planet. It is also hot, liquid, viscous, and electrically conductive to a certain extent.
Powerful currents thousands of kilometers long can occur in the Earth’s mantle. And if there is a movement of charges there, they generate their own magnetic fields, which are smaller than the planetary one, but can still stretch almost over an entire continent.
Finally, there may be local magnetic anomalies that are no larger than a few tens of kilometers. They are associated with the presence of some minerals underground at a much shallower depth (most often iron ores), which can also conduct current and be magnetized.
All these anomalies are superimposed on the global magnetic field and can lead to its distortion. For example, it is well known that if there is ore underground, the compass can start spinning like crazy in that place.
The magnetic field of our planet is most affected by anomalies associated with mantle flows. Because of them, the Earth’s magnetic poles can differ from the geographical ones even more than is due to the orientation of the dipole associated with the Earth’s core. The north and south poles of our planet are generally located in such a way that the axis drawn through them does not pass through the geometric center of the Earth.
In addition, the magnetic poles of our planet are moving. This is all due to the same mantle flows, which, albeit slowly, are constantly changing their direction of movement. This can be seen most clearly in the north magnetic pole: in the nineteenth and twentieth centuries, it moved across the Canadian Arctic archipelago, and in recent decades it has been moving quite rapidly across the Arctic Ocean towards Eurasia.
Is there anything dangerous or even unusual about this process? The answer to the first question is almost certainly no. After all, the total power of a large magnetic field dipole does not change, which means that its protective properties do not change either.
The answer to the second question is much more difficult to give. Scientists have been observing the North Magnetic Pole for only a few centuries. Almost all this time, it has been moving, and quite chaotically and with varying speeds, so nothing is surprising about the current movement.
However, no one can 100% rule out that it had been moving for a couple of thousand years before that. From the rather limited information we have about mantle flows, almost every development can be considered natural. No one can say that they are a sign of an impending catastrophe.
Inversions of the Earth’s magnetic field
Finally, it is worth mentioning what causes fear among people the most. Magnetic field inversions. These are situations where it changes its polarity, and the north magnetic pole becomes the south pole, and vice versa.
It sounds scary, but this phenomenon does not have any major consequences in itself. The geographical poles remain in place. The Earth does not turn over, and no one falls off it. The direction of the power lines simply changes, and the compass arrow begins to point south. Unusually, there is no direct threat to humanity.
However, during this event, especially at the initial and final stages, the field strength can drop to zero. And if only on Earth. The same thing happens with those magnetic fields that stretch out into space. This means that their ability to trap high-energy particles is sharply reduced, and they begin to hit the cells of living organisms more often.
Source: www.ontariobeneathourfeet.com
This can last for hundreds, thousands, and tens of thousands of years, which is why living organisms can theoretically die from radiation damage. And this is what scientists are really afraid of when it comes to the possibility that the Earth’s magnetic field could disappear.
It is difficult to say what exactly causes the inversion of the Earth’s magnetic field. Most likely, the answer lies somewhere in the unpredictable flows of matter in the outer core of our planet.
However, there is no need to panic. The fact is that changes in the polarity of the magnetic field are well monitored by the same transverse magnetic anomalies near oceanic ridges. And they suggest to scientists that such events have occurred dozens of times in the last few hundred million years alone.
If they had led to mass extinctions, paleontologists would have noticed it for sure. For example, the last time the Earth’s magnetic field changed polarity was about 42 thousand years ago. This is the so-called Laschamp event. It is considered to be very short, but during it, for several centuries, the field strength was only 25% of the current one, and at the beginning and end, it dropped to 5%, i.e., 20 times.
Humanity already existed at that time and should have experienced some problems, but paleontologists see nothing of the sort. There are hypotheses that the Laschamp event could have caused the extinction of the Australian megafauna or Neanderthals, but they seem unlikely and insufficiently substantiated at this point.
And before that, there was the Brunhes-Matuyama event, which began 781 thousand years ago and lasted for 22 thousand years. No particular extinctions, especially among human ancestors, were observed. However, traces of radioactive carbon and other elements indicating an increase in the radiation background in samples, including biological ones, are present.
There is no final solution to all this. Most likely, we are simply overestimating the possible impact of increased solar radiation on living beings when the magnetic field disappears. In today’s civilized world, with its continuous medical control, we would most likely record a surge in cancer. But during the Stone Age, radiation-related deaths remained relatively unnoticeable compared to other causes.
There is a lot of talk now about the slow decline in the strength of the Earth’s magnetic field. Most likely, this is a natural process that is not unique. However, given everything that is known about this process in the past and how it has affected living beings, we should not expect any catastrophic consequences.
