The news of the ‘stop’ of the Earth’s core discovered by Chinese researchers Yi Yang and Xiaodong Song, from Peking University, was, on Monday, one of the most widespread and commented on in the world. Hundreds of headlines announced the event, and almost immediately the social networks began to boil with thousands of reactions and questions of all kinds. One in particular was the most repeated: What consequences will the ‘slowdown’ of the inner core of the Earth have for us?
Some media even went so far as to announce that there would be profound changes in the climate and that the phenomenon will also affect sea level. But the truth is that none of this is mentioned in the study, published in Nature Geoscience. The authors, in effect, limit themselves to saying that the phenomenon could cause, at most, small changes in the intensity of the magnetic field and in the length of the days, which would vary by just one tenth of a thousandth of a second per year. That is there will be no consequence that we can perceive directly or that affects our daily life.
One of the most interesting points of the study, moreover, is that the speed of rotation of the solid core seems to ‘oscillate’ with respect to that of the rest of the Earth, speeding up or slowing down in cycles of about seventy years. In other words, what Yang and Song observed is something that has probably been repeated over and over again, every seven decadesfor countless millions of years without us even realizing it.
The core keeps spinning
But what do the researchers mean when they talk about a ‘stop’ of the inner core? Certainly not due to the fact that it has completely stopped rotating, but rather that it has stopped in relation to the rotational movement of the mantle and the surface. And what does this mean?
The first thing to understand is that the inner core of the Earth is a solid sphere, made mostly of iron and nickel, that is about 2,400 km in diameter and that ‘floats’ freely in a liquid ocean (also made of iron and nickel). , the outer core, which is where the Earth’s magnetic field is generated. That is, we could consider the inner core as ‘a planet within our planet’, suspended right in its center and free to move independently from the rest of the Earth.
But how exactly does it move? The issue is not simple, and around it there is a scientific debate that has lasted for several decades. As explained yesterday on ABC, Yang and Song realized that from the 1970s to 2009, the solid core of the planet seemed to be rotating a bit. faster than the mantle and crust, which means that if we could ‘look down’ from the surface and observe the nucleus, we would see it spinning slowly forward. However, around 2009 this rotation began to slow down. And if we were to look at the core now, we wouldn’t see it spinning at all, because it’s spinning at the same speed as the surface.
The important thing about the study, then, is the verification that the rotation of the nucleus is not constant, as was thought until just a few years ago, but that it follows much more complex patterns. By analyzing hundreds of seismic waves from earthquakes since the 1960s, the researchers discovered that something similar had already happened in the early 1970s, which suggests the existence of an oscillation, a cycle in the velocity of inner core rotation which is repeated more or less every seven decades.
This oscillation, according to the researchers, is probably due to the gravitational influence of the much heavier Earth’s mantle, the thick layer of semi-molten rock that, with its 3,000 km thickness, separates the core from the Earth’s crust.
Therefore, the ‘slowdown’ in the rotation of the solid nucleus has nothing to do, for example, with an imminent reversal of the magnetic field, nor with weather catastrophes or with a sudden rise in sea level. Something that could only happen if the nucleus stopped completely, which is not the case, or if the external liquid nucleus stopped rotating and, therefore, generating the magnetic field that protects the planet from the attacks of cosmic radiation.
Of course, the last word hasn’t been said and much remains to be learned about the inner workings of our planet and exactly how what happens in the center of the Earth influences what happens on its surface.