Eppur if you move – these are the words, according to some sources, uttered by the famous Galileo Galilei after he abandoned the heliocentric vision of the Universe before the court of the Holy Inquisition in 1663.
Nearly four centuries have passed since that forced recognition, and today we not only know—and have demonstrated—that the Earth moves: we have also demonstrated that it does so in a variety of ways. Some of them we still cannot fully explain. Among them is the oscillating rhythm of the inner core, the iron heart of the planet.
The Earth’s inner core, a sphere of iron and nickel with a radius of 1,221 kilometers, separated from a mantle of liquid iron, has been moving and changing for decades. A recent paper published by Professors Vidale and Wang from the University of Southern California (USA) explains that the planet’s rotation rate fluctuates with a period of 6 years, according to seismological data.
The meaning of the moon, days and nights
Since the time of Galileo, it has been known that the Earth describes an elliptical orbit with the Sun at one of the foci of the ellipse, in addition to rotating around an axis passing through the poles. The first of these movements is the cause of the seasons (along with the tilt of the Earth’s axis of rotation relative to the ecliptic), and the second we owe to days and nights.
The center of the Earth does not exactly describe an elliptical orbit around the Sun, but rather moves in a kind of loop. This is due to the influence of the Moon, which causes the Earth to rotate around the center of mass or barycenter of the Earth-Moon system simultaneously with its rotation around the Sun.
The barycenter is located approximately a quarter of the Earth’s radius. And this is because the Moon has an important mass.
Of course, if you compare the distance from the barycenter of the Earth-Moon system to the center of the Earth with the Earth-Sun distance, then it is so insignificant that it can be neglected. For this reason, it has virtually no effect on the development of the annual seasons and the cycle of day and night.
Rotation is not as simple as it is made out to be because the Earth’s rotation axis is not fixed but undergoes some “minor” movements such as precession, nutation, etc.
Change of seasons and ice ages
The precession of the earth’s axis is the most important of the minor movements. It is also a periodic movement, that is, repeated from time to time. In this case, it repeats every 25,776 years, so it shouldn’t worry us too much.
The precession of the Earth’s axis causes the seasons to change between the Earth’s two hemispheres. Let’s think about the top. When thrown, it remains in an upright position, rotating around its vertical axis, but after a moment the axis tilts and begins to rotate, forming a kind of inverted cone. This movement is precession.
Nutation is the periodic movement of the earth’s axis from greater to lesser inclination relative to the ecliptic, as a result of which, from a climatological point of view, we have more or less contrasting seasons. With a greater degree of inclination of the earth’s axis relative to the ecliptic, the climatological difference between summer and winter is more contrasting than with a smaller angle. This fact gave rise, for example, to ice ages on Earth. It is known that this movement is due to the gravitational attraction of the Moon and that its period is much shorter than the precession period. Nutation has a period of 18.6 years.
All these periodic movements of the Earth have an important influence on climate. These are known as Milankovitch cycles.
Internal movements
The above movements occur due to the gravitational interaction of the Earth with other stars in the solar system such as the Sun and Moon. But inside the Earth also moves.
We cannot forget the tectonic movements of plates due to magmatic activity beneath the Earth’s surface, the movement of glaciers due to climate change, and even more so the movements that the Earth’s core undergoes.
Tectonic movements can cause earthquakes, mountain building, volcanic activity, and the creation of geographic features such as mountain ranges, ocean trenches, island arcs, etc.
Center
The Earth’s core is more than 5,000 km deep, but humans have only drilled down to about 12 km. Direct study of what is happening in the Earth’s core is impossible with current technology. We can observe the effects that these movements produce and draw conclusions about what might happen.
It is known, for example, that the Earth’s core is made of molten iron and nickel and that it rotates, which creates a magnetic field near the Earth.
This magnetic field protects us from solar radiation, which is full of high-energy particles that would make life on Earth impossible, by directing them towards the Earth’s poles and creating wonderful auroras.
Additionally, by analyzing the seismic waves produced by earthquakes, scientists have a better idea of what is happening in the core. This is exactly what Professors Wang and Vidale from the University of Southern California studied. According to their study published in Science Progressin which they analyzed seismic waves generated by controlled explosions, there appears to be a six-year cycle in which the Earth’s core changes its speed of rotation, which could explain the change in day length, which fluctuated almost constantly. in recent decades.
After these and other studies that are likely to be carried out, there is no doubt that Galileo was unable to prove that the Earth moves.