Humanity has almost four million years behind us, and during this time we have achieved an understanding of the movement of tectonic plates, learned how to predict the weather and mastered outer space. But our planet is still fraught with many secrets and mysteries. One of them, which is associated with global warming and the theory of catastrophes, is the precession of the planet's axis.
Historical background
The movement of the equinoxes against the background of the stars was noticed in the 3rd century BC by Aristarchus of Samos. But the first to describe the increase in the longitude of the stars and the differences between the sidereal and actual year was the ancient Greek astronomer Hipparchus in the 2nd century BC. And this despite the fact that at that time it was believed that all the stars are fixed on a fixed sphere, and the movement of the sky is the movement of this sphere around its own axis. After were the works of Ptolemy, Theon of Alexandria, Sabit ibn Kurr, Nicolaus Copernicus, Tycho Brahe and many others. The reason for the precession of the Earth's axis was explained and described by Isaac Newton in his "Principles" (1686). And the precession formulashowed the American astronomer Simon Newcomb (1896). It is his formula, refined in 1976 by the International Astronomical Union, that describes the speed of precession depending on the time reference.
Physics of the phenomenon
In elementary physics, precession is a change in the angular momentum of a body when its direction of motion in space changes. This process is observed on the example of a top and its slowdown. Initially, the vertical axis of the top, when it slows down, begins to describe a cone - this is the precession of the top axis. The main physical property of precession is inertia-free. This means that when the force causing the precession ceases, the body will take a stationary position. In relation to celestial bodies, such a force is gravity. And since it acts constantly, both the movement and the precession of the planets will never stop.
The movement of our stationary planet
Everyone knows that the planet Earth revolves around the Sun, rotates along its axis and changes the direction of this axis. But that's not all. Astronomy distinguishes thirteen types of movement of our house. Let's list them briefly:
- Rotation around its own axis (change of day and night).
- Rotation around the Sun (change of seasons).
- "Walking forward" or leading up to the equinoxes is precession.
- Wobbling of the earth's axis - nutation.
- Change of the Earth's axis to the plane of its orbit (tilt of the ecliptic).
- Changing the ellipse of the earth's orbit (eccentricity).
- Changes in perihelion (distance fromthe farthest point of the orbit from the sun).
- Parallactic inequalities of the Sun (monthly changes in the distance between our planet and the star).
- At the time of the parade of the planets (the planets are located on one side of the Sun), the center of mass of our system goes beyond the boundaries of the solar ball.
- Earth deviations (disturbances and perturbations) under the influence of the attraction of other planets.
- Progressive movement of the entire solar system towards Vega.
- Movement of the system around the core of the Milky Way.
- The movement of the Milky Way galaxy around the center of a cluster of similar galaxies.
It's all complicated, but mathematically proven. We will focus on the third movement of our planet - precession.
Is this a top?
We used to think that the axis of rotation of the planet around its axis is unchanged and its northern end is directed to the point of the polar star. But it's not quite like that. The axis of the planet describes a cone, as well as a children's toy top or spinning top, which is caused by the attraction of our satellite and our luminary. As a result, the planet's poles are slowly moving relative to stars with an arc radius of 23 degrees and 26 minutes.
How to see it?
The inclination of the earth's axis is due to interactions in the gravitational system Sun-Earth and Moon-other planets. The forces of gravity are so great that they cause the planet's axis to precess - a slow wiggle clockwise in the opposite direction of the planet's rotation. Seeing the phenomenon of lunisolar precession in action is easy enoughlook at the spinning top. If you deviate its handle from the vertical, then it begins to describe a circle in the opposite direction of rotation. If we imagine that the axis of the planet is a pen, and the planet itself is a top, then this will be, albeit a rough, example of the precession of the Earth's axis. Our planet goes through half of the precession cycle in 25776 years.
Effects of precessions of the Sun and the Earth-Moon complex
The slow movement of the vernal equinox (the intersection of the celestial equator and the ecliptic), provoked by precession, leads to two consequences:
- Adjusting celestial coordinates.
- Changes in the stay of the Sun in the zodiac constellations.
Changes in the vernal equinox led to the emergence of an international agreement on the coordinates of celestial bodies with mandatory fixation on a specific date. Indeed, due to the precession of the Earth's axis in ancient times, this point was in the constellation Aries, and today it is located in the constellation Pisces. By analogy, there is no correspondence between the astrological signs of the zodiac constellations. For example, the sign of Pisces indicates that in the period from February 21 to March 21, the luminary is located in the constellation Pisces. So it was in ancient times. But today, due to the precession of the Earth's orbit during this period of time, the Sun is in the constellation of Aquarius.
There will be no eternal spring
Precession is the precession of the equinoxes, which means the shift of the points of the autumn and spring equinoxes. In other words, spring on the planet with eacha year comes earlier (by 20 minutes and 24 seconds), and autumn later. This has nothing to do with the calendar - our Gregorian calendar takes into account the length of the tropical year (from equinox to equinox). Therefore, in fact, the effect of precession is already included in our calendar. This shift is periodic, and its period, as mentioned earlier, is 25776 years.
When will the next Ice Age begin?
Change in the direction of the Earth's axis every about 26 thousand years (precession) is a change in its northern direction. Today, the point of the North Pole points to the North Star, in 13 thousand years it will point to Vega. And in 50 thousand years the planet will go through two cycles of precession and return to its current state. When the planet is located "directly" - the amount of solar energy received is minimal and the ice age begins - most of the land is covered with ice and snow. The history of the planet shows that the ice age lasts about 100 thousand years, and the interglacial - 10 thousand. Today we are experiencing such an interglacial time, but in 50 thousand years the ice crust will cover the planet to the borders below New York.
Not only precession is to blame
According to the National Aerospace Agency NASA, the geographic North Pole of the planet since 2000 began to actively shift to the east. For 115 years of studying the climate on the planet, he deviated by 12 meters. Until 2000, the pole moved towards Canada at a rate of several centimeters per year. But after that date, he changed both direction and speed. Today he is at a speedup to 17 centimeters per year moves towards Britain. The reasons for this phenomenon are the melting of the Greenland glaciers, an increase in the mass of ice in the east of Antarctica, droughts in the Caspian and Hindustan basins. And behind these phenomena is the anthropogenic factor of impact on the Earth.
Why are winters not the same?
Besides the fact that our planet precesses, it also oscillates during this process. This is nutation - fast relative to the precession period "wiggle of the poles". It is she who changes the weather - sometimes the winter is colder, then the summer is drier and hotter. In years of particularly strong nutation, more severe weather conditions are expected.
