The Earth’s axis of our planet in the northern vector is directed to the point where the second-magnitude star, called the Polar, is located in the tail of the Ursa Minor constellation.
This star during the day outlines in the celestial sphere a small circle with a radius of about 50 minutes of the arc.
In ancient times, they knew about the inclination of the earth's axis
A very long time ago, in the II century BC. e., astronomer Hipparchus discovered that this point is mobile in the starry sky and slowly moves towards the movement of the Sun.
He calculated the speed of this movement at 1 ° per century. This discovery is called the
"precession of the earth's axis." This is a move ahead, or a prelude to the equinox. The exact value of this movement, constant precession, is 50 seconds per year. Based on this, the complete ecliptic cycle will be approximately 26,000 years.
Precision is important to science.
Back to the question of the pole. Determining its exact position among stars is one of the most important tasks of astrometry, which deals with measuring arcs and angles in the celestial sphere in order to determine the coordinates of stars and planets, their own motions and distances to stars, as well as solving practical astronomy problems important for geography and geodesy and navigation.
You can find the position of the pole of the world using photography. Imagine a long-focus photographic camera, implemented in the form of an astrograph, aimed motionlessly at an area of the sky near the pole. In such a photograph, each star will describe a more or less long arc of a circle with a single common center, which will be the pole of the world - the point where the rotation of the earth's axis is directed.
A little bit about the angle of inclination of the Earth axis
The plane of the celestial equator, being perpendicular to the earth's axis, also changes its position, which causes the movement of the points of intersection of the equator with the ecliptic. In turn, the attraction by the Moon of the equatorial displacement of the Earth’s masses tends to turn the Earth so that its equatorial plane crosses the Moon. But in this case, these forces act not on the water shell of the Earth, but on the masses forming the equatorial swelling of its ellipsoidal figure.
Imagine a ball inscribed in an earth ellipsoid, which it touches at the poles. Such a ball is attracted by the Moon and the Sun by forces directed to its center. For this reason, the earth's axis remains unchanged. This attraction, acting on the equatorial swelling, tends to turn the Earth in such a way that the planes of the earth's equator and the object attracting it coincide, creating a tilting moment.
The sun during the year twice moves away from the equator to ± 23.5 °, and the distance of the moon from the equator during the month reaches almost ± 28.5 °.
Children's toy spinning top reveals a little secret
If the Earth did not rotate, then it would tend to bend, as if nodding, so that the equator kept track of the Sun and the Moon all the time.
True, due to the enormous mass and inertia of the Earth, such oscillations would be very insignificant, since the Earth would not have time to respond to such a quick change of direction. We are well acquainted with this phenomenon on the example of a children's top.
Gravity tends to overturn the top, but the centripetal force protects it from falling. As a result, the axis moves, describing the conical shape. And the faster the movement, the narrower the figure. The earth axis behaves in exactly the same way. This is a certain guarantee of its stable position in space.
Earth's tilt affects climate
The Earth moves around the Sun in an orbit that is almost similar to a circle. Observing the speed of stars located near the ecliptic, it means that at any moment we approach one star and move away from the opposite stars in the sky at a speed of 29.5 kilometers per hour. The change of seasons is the result of that. There is an inclination of the earth's axis to the plane of the orbit and is about 66.5 degrees.
Due to the small elliptical orbit, the planet in January is slightly closer to the Sun than in July, but the difference in distance is not significant. Therefore, the effect on the receipt of heat from our star is hardly noticeable.
Scientists believe that the earth's axis is an unstable parameter of our planet. Studies show that the angle of inclination of the earth's axis with respect to the plane of its orbit in the past was different and periodically changed. According to the legends that reached us about the death of Phaethon in the descriptions of Plato, there is a mention of the axis displacement at this terrible time by 28 °. This disaster took place to be more than ten thousand years ago.
We fantasize a little and change the angle of the Earth
The angle of the Earth’s axis with respect to the orbital plane today is 66.5 ° and provides a not so sharp winter-summer temperature fluctuation. For example, if this angle would be about 45 °, what would happen at the latitude of Moscow (55.5 °)? In May, the sun under these conditions reaches its zenith (90 °) and moves to 100 ° (55.5 ° + 45 ° = 100.5 °).
With such an intense movement of the Sun, the spring period would have passed much faster, and in May would have reached a peak in temperature, as at the equator at the maximum solstice. Then it would weaken slightly, since the sun, passing the zenith, would go a little further. Then it came back, passing the zenith again. For two months, in July and May, an unbearable heat would be observed, about 45-50 degrees Celsius.
Now consider what would happen in the winter, for example, in Moscow? After passing the second zenith, our luminary would have sunk in the month of December to 10 degrees (55.5 ° -45 ° = 10.5 °) above the horizon. That is, with the approach of December, the sun would come out for a shorter period than now, rising low above the horizon. During this period, the sun would shine for 1-2 hours a day. Under these conditions, the night temperature drops below -50 degrees Celsius.
Every version of evolution has a right to life.
As we see, for the climate on the planet, it is important at what angle the earth's axis. This is a fundamental phenomenon in the mild climate and living conditions. Although, perhaps, under different conditions on the planet, evolution would go a little different way, creating new species of animals. And life would continue to exist in its other variety, and perhaps there would be a place for a “different” person in it.