In many ways, fragmentary thoughts about the relationship of knowledge in the field of astronomy, modern history Earth from ancient history, turn into a harmonious hypothesis (harmonious, put it in quotation marks) under the influence of the notes that the portal’s readers bring. IN in this case they helped to reveal one of the secrets of the Zodiac with the material presented Star-foxy - “Global cataclysms await the planet.
Of course, there's a lot I don't know. I could not find other words of synonyms describing the mechanism of precession than those that are most often found in textbooks - the displacement of the points of the spring and autumn equinoxes and those new ones that I paid attention to: " braking during the movement of the Earth around the signs of the Zodiac", about which I.V. speaks Meshcheryakov:

[When scientific group, which I was a part of, was developing the GLONASS space navigation system, it was necessary to solve many fundamental tasks. It was necessary to take into account the drift of the poles and the uneven rotation of the Earth - the so-called geodynamics. As of 1990, the deceleration of the Earth's movement around the signs of the Zodiac was 5 arc seconds per year. The time of the spring equinox is taken, and the Earth arrives at the next equinox with a delay of 5 arc seconds. After 72 years, 1 degree is gained. And the epoch of the Zodiac signs is 30 degrees. We multiply, and it turns out 2160 years. 12 - full circle Zodiac - multiply by 2160, and get the inverse precession of the Earth. This number - 25920 - is one of the life cycles of the planet. So global warming associated with the cycles of existence and development of the Earth and solar system.k

It’s not very clear to me whether we can say that this is a slowdown, as Meshcheryakov said (or the journalist misrepresented this). I can’t say anything about this due to lack of knowledge. However, I clearly remember myths that mention that during periods of catastrophes (floods or something else), the Earth would stop rotating for three days.

But, in order to make a smooth transition to the hypothesis, to develop it, which Doctor of Technical Sciences Ivan Vasilievich Meshcheryakov did not dare, I will make an intermediate hypothesis, supported by references to the mechanism of precession, with schematic drawings made during the era of space flights, although the first one to explain the mechanism of precession Newton was a genius.

Now, let's go back to ancient times. Excerpt from Alan Alford's book [Gods of the New Millennium]

[Thousands of years ago, ancient astronomers divided the starry sky into twelve sectors and came up with names and symbols for them, by which they are known to this day. The Greeks gave each such group of stars the name "zodiac". Nowadays, in order to determine the character of a person and draw up his complete horoscope, they look under what star he was born and what was the relative position of the Sun and the Earth on the day of his birth. This kind of entertainment is now very widespread and very entertaining, but in essence it has not the slightest relation to science. Astrology has had a long way to go.

Going back to time ancient Sumer and Egypt, we see that the concept of the zodiac was then used in completely different areas. For there is no doubt that in these ancient civilizations the signs of the zodiac were used on a scientific level. It is now widely accepted, incredible as it may seem, that the ancients knew a precessional cycle of 25,920 years, and they divided this cycle into 12 periods of 2160 years.

It was already mentioned in Chapter 6 that the Sumerian mathematical system was built around the number 3600, so that the highest number in this system, 12,960,000, was equal to 500 precessional cycles of 25,920 years. If 25,920 years corresponds to 360 degrees of the “circumference of the sky,” then 2160 years is 30 degrees, and 72 years is 1 degree. Thus, the number "72" also played a very important role. The significance of this number in one legend led Egyptologist Jane Sellers to suggest that the Egyptians were also aware of the phenomenon of precession. This legend is the myth of Osiris, it tells how 72 conspirators, led by Set, were going to kill Osiris. Jane Sellers is an exceptional person - she is an expert in many fields, including astronomy and archaeology. She is convinced that the 4,000-year-old Pyramid Texts clearly reveal knowledge of astronomy, even if the Egyptians themselves did not realize the full implications of it. Sellers writes: "I am convinced that for ancient man numbers 72... 2160, 25 920 contain the concept of Eternal Return."

Egyptian zodiac or Dendera zodiac.

Precession earth's axis

Precession also called the anticipation of the equinoxes, because it causes a slow displacement of the points of the spring and autumn equinoxes, caused by the movement of the planes of the ecliptic and equator ( rice. 2 ) (the equinox points are determined by the line of intersection of these planes). Simplified Precession can be represented as the slow movement of the axis of the world (straight line parallel to the average axis of rotation of the Earth RR") along a circular cone, the axis of which is perpendicular to the ecliptic ( see fig. 2 ), with a period of complete revolution k 26000 years.

Dear astronomy lovers! “Every person in our time is faced with the signs of the Zodiac. Thus, he finds out under which star (constellation) he was born. But often, having compared the astrological and astronomical dates of the Sun in a particular constellation, people are surprised at the discrepancy between these dates. All the fact is that over the 2 thousand years since the creation of horoscopes, all the stars have shifted in the sky relative to the points of the equinoxes. This phenomenon is called precession (precession of the equinoxes) and this phenomenon is described in the wonderful article by Academician A.A. “Precession”. was published in the magazine "Earth and Universe" No. 2 for 1978."

Academician A. A. Mikhailov.

PRECESSION.

On April 26, Alexander Alexandrovich Mikhailov will turn 90 years old. The works of Academician A. A. Mikhailov received worldwide recognition. Its versatility is amazing scientific interests. These are practical and theoretical gravimetry, eclipse theory, stellar astronomy and astrometry. Academician A. A. Mikhailov contributed greatly to the formation and development of Soviet astronomy. The editorial board and readers of Earth and the Universe cordially congratulate Alexander Alexandrovich on his anniversary and wish him health and new creative success.

"Precession" in Latin means "walking forward." What is precession and how is its magnitude determined!

WHERE IS THE COORDINATE ORIGIN?

The position of a point on the Earth's surface is determined by two coordinates - latitude and longitude. The equator as the origin of latitude is given by nature itself. This is a line at all points of which the plumb line is perpendicular to the axis of rotation of the Earth. The beginning of the longitude count has to be chosen arbitrarily. This may be a meridian passing through some point, which is taken as the starting point. Since the calculation of longitude is associated with the measurement of time, such a point is taken astronomical observatory, where the time is determined most accurately. Thus, in France in the old days, longitudes were calculated from the Paris Observatory; in Russia after the founding of the Pulkovo Observatory in 1839 - from the meridian passing through the center of its main building. There were attempts to take as a starting point such that in a given territory all longitudes were measured in one direction. For example, in the 17th century, the most western point Old World - Ferro, one of the Canary Islands, to the east of which lay all of Europe, Asia and Africa. In 1883, by international agreement, the initial meridian passing through the optical axis of the passage instrument of the Greenich Observatory was adopted as the initial one (Earth and Universe, No. 5, 1975, pp. 74-80. - Ed.).

Choice prime meridian for calculating longitudes is not of fundamental importance and is dictated by expediency and convenience. It is only important that the starting point is stable and not located in a seismically turbulent area. It is also necessary that it is not located too close to the pole, where the position of the meridian is not determined very confidently. If these conditions are met, the constancy of the prime meridian will be ensured for thousands of years, since the displacement of blocks earth's crust does not exceed a few millimeters per year, which can cause a change in longitude by 0.1" in just a millennium.

On the celestial sphere, the position of the luminaries is also determined by two spherical coordinates, similar geographical coordinates. Latitude here is replaced by declination equal to the angular distance of the point from the celestial equator - great circle, the plane of which is perpendicular to the axis of rotation of the Earth. Geographical longitude corresponds to right ascension, which is measured from west to east - in the direction of the movement of the planets of the solar system. However, the choice starting point on the celestial sphere it is more difficult. It is clear that such a point must be motionless, but relative to what? You cannot take any star as a starting point, because each star has its own movement, and for some it exceeds \" per year. This is tens of thousands of times more than the movement of the zero point of geographic longitude.

WHY DOES THE DECLINATION OF STARS CHANGE?

Astronomy as a science arose in ancient times partly as a result of the need to measure time associated with the apparent daily and annual movements of the Sun, which cause the change of day and night and seasons. From here, a system of astronomical coordinates closely connected with the Sun appeared by itself. The point of intersection of the celestial equator with the ecliptic, through which the Sun passes at the moment of the vernal equinox, was taken as the zero point of right ascensions. In the days of ancient astronomers, this point was located in the zodiac constellation Aries, the sign of which T is similar to greek letter gamma. This designation of the vernal equinox point has been preserved to this day. It is not marked by anything in the sky and its position can only be determined by measuring the declination of the Sun near the equinox: at the moment when, during the transition from the southern hemisphere to the northern, its declination is zero, the center of the Sun will be at the point of the vernal equinox. Astronomers were able to tie it to the stars more than 2000 years ago. At that time there were no means for observing the stars during the day along with the Sun, so one has to be surprised at the wit and skill of the ancient observers.

The Greek astronomer Clarius Ptolemy, in his famous work, known to us under the distorted Arabic name “Almagest” (mid-2nd century), wrote that the greatest Greek astronomer Hipparchus, who lived three centuries before him, determined the latitudes of stars (angular distances from the ecliptic), as well as their declinations (distances from the equator) and compared them with similar observations by Timocharis made 100 years earlier. Hipparchus found that the latitudes of the stars remained unchanged, but the declinations changed noticeably. This indicated a displacement of the equator relative to the ecliptic. Ptolemy checked the conclusions of Hipparchus and received the following declinations of the stars: a Taurus a Virgo Aldebaran Spica + 8°45" +1°24" (Tymoharps) + 9°45" +0°36" (Hipparchus) +11°0" - 0°30" (Ptolemy) It turned out that the declination of Alde the Ram increased over time, and Spica decreased. Hipparchus interpreted this as the point of the vernal equinox moving among the stars. It moves towards the Sun, so the Sun returns to it before it makes a full revolution along the ecliptic. This is where the term “anticipation” of the equinox comes from (in Latin, praecezeere). The movement of the vernal equinox (D) for the period from the 3rd century BC to the 2nd century. K. Ptolemy associated the change in the declinations of the stars Aldebaran (A) and Spica (8) with the displacement of the equator relative to the ecliptic, and therefore with the movement of their intersection point G towards the Sun (the direction of its movement is indicated by the arrow).

The situation has also changed North Pole world from R to R"

The speed of movement of the vernal equinox point along the ecliptic is very small; Hipparchus estimated it at 1° per 100 years, or 36" per year. Ptolemy received a higher value - almost 60" per year. Since then, this fundamental quantity for astrometry has been refined as observations accumulate, technology improves, and the passage of time. Arab scientists in X-XI centuries found that the point of the vernal equinox shifts by 48-54 per year", the great Uzbek astronomer Ulugbek in 1437 received 51.4". The last person to make observations with the naked eye was Tycho Brahe. In 1588 he estimated this value at 51".

The year of nature, that is, the period of repetition of the seasons, called the tropical year, is determined by the movement of the Sun relative to the point of the vernal equinox and is equal to 365.24220 average sunny days. The complete revolution of the Sun relative to a fixed point on the ecliptic, such as a star with vanishingly small proper motion, is known as a sidereal year. It is equal to 365.25636 days, that is, 0.01416 days, or 20 minutes 24 seconds, longer than the tropical year. This is precisely the period of time required for the Sun to pass through the segment of the ecliptic to which the point of the vernal equinox has retreated over the course of a year.

WILL POLAR ALWAYS REMAIN POLAR

So, more than 2000 years ago, the phenomenon of precession was discovered, but it was explained only in 1687 by Isaac Newton in his immortal work “Mathematical Principles of Natural Philosophy.” He correctly concluded that, due to the daily rotation around its axis, the Earth has the shape of an ellipsoid slightly flattened at the poles. It can be considered as a ball with additional mass located along the equatorial belt. The attraction of the Earth by the Moon and the Sun in this case can be divided into two parts: attraction globe force applied to its center, and the attraction of the equatorial belt. When the Moon 2 times a month and the Sun 2 times a year move away from the plane of the Earth's equator, their attraction creates a moment of force that tends to rotate the Earth so that its equator passes through these luminaries.

The gravitational forces of the Moon acting on the center of our planet and its equatorial belt equator, their attraction creates a moment of force that tends to rotate the Earth so that its equator passes through these luminaries. If the Earth did not rotate, then such a rotation would actually occur, but fast rotation The Earth (after all, the point of its equator moves at a speed of 465 m/s) creates gyroscopic effect like a spinning top. The force of gravity tends to bring down the top, but rotation keeps it from falling, and its axis begins to move along a cone with the top at the fulcrum. Similarly, the earth's axis describes a cone around the ecliptic axis, moving away by 50.2" annually and making a full revolution in almost 26,000 years. This change in the direction of the earth's axis in space leads to the fact that the North Pole of the world describes a small circle around the North Pole of the ecliptic with a radius of about 23.5°, the same happens with South Pole. Since the proper motions of the stars are small compared to the precessional motion, the stars can be considered practically motionless, and the poles can be considered moving among them.

Currently, the North celestial pole is very close to a bright 2nd magnitude star Ursa Minor, which is therefore called Polar. In 1978 angular distance poles from this star is 50", and in 2103 it will become minimal - only 27". We would call this proximity of the celestial pole to a bright star fortunate. Indeed, in practical astronomy and its applications to geography, surveying, navigation and aviation, the North Star is used to determine latitude and azimuth. By 3000, the North Pole will move almost 5° away from the current Polaris. Then for a long time there will be no bright star close to the pole. Around 4200, the pole will come within 2° of the 2nd magnitude star a Cephei. In 7600, the pole will be close to the 3rd magnitude star b Cygnus, and in 13800, the polar star, although far from the pole (by 5°), will be the brightest star northern hemisphere Vega in the constellation Lyra.

IN southern hemisphere, on the contrary, the pole is now in an area of ​​the sky that is extremely poor bright stars. The star closest to the pole, O Octanta, is only 5th magnitude and barely visible to the naked eye. But in the future, albeit distant, in the southern hemisphere there will be a “harvest” for near-polar stars. However, the movement of the poles is not strictly uniform; it changes slowly due to the secular decrease in the inclination of the equator to the ecliptic, as well as a decrease in eccentricity earth's orbit. In addition, there are more significant periodic oscillations in the position of the poles, caused by changes in the declinations of the Moon and the Sun. When their declinations increase - the luminaries move away from the equator - their desire to turn the Earth in their direction increases. Although the Moon has a mass 27 million times less than the mass of the Sun, it is so much closer to the Earth that its action is 2.2 times stronger than the action of the Sun. Thus, almost 70% of the precessional movement is caused by the Moon. The Moon and the Sun periodically change their position relative to the equator. The declination of the Sun regularly changes within ±23.5° with a yearly period, the declination of the Moon changes more complexly, depending on the position of the nodes lunar orbit, which make one revolution along the ecliptic in 18.6 years. The inclination of the lunar orbit to the ecliptic is 5° and, when the ascending node is close to the vernal equinox, the inclination of the orbit is added to the inclination of the ecliptic, so that the declination of the Moon fluctuates between ±28.5° during the month. After 9.3 years, when the descending node approaches the vernal equinox, the inclinations are subtracted and the declination of the Moon changes within ±18.5°. Monthly changes in the declination of the Moon and annual changes in the declination of the Sun do not have time to produce a significant effect on the precessional movement. The fluctuation of the declination of the Moon with a period of 18.6 years causes vibrations of the earth's axis with an amplitude of 9.2", called nutation. This phenomenon was discovered by the English astronomer James Bradley in 1745.

There is one more circumstance that does not affect the declination of stars, but nevertheless causes a slight movement of the vernal equinox point. This is the attraction of the planets of the solar system. The positions of the North (above) and South (below) poles of the world among the stars. The positions of the poles are marked with numbers every thousand years, starting from 2000 BC (-2) and ending with 23,000 (23). The planets are too far from the Earth for their effect on the Earth’s equatorial belt to be noticeable. However, due to the inclinations of planetary orbits to the ecliptic, a certain, albeit very weak, moment of force arises, tending to rotate the plane of the earth's orbit until it coincides with the plane of the orbit of a given planet. The total effect of all major planets slightly changes the position of the ecliptic, which also affects the position of its intersection points with the equator, that is, the position of the vernal equinox point. This additional displacement, equal to approximately 0.1" per year, is called precession from the planets, while the main movement is lunisolar precession. The combined effect of lunisolar precession and precession from the planets is called total precession.

HOW TO MEASURE PRECESSION?

Knowing the masses of the planets and the elements of their orbits, it is possible to accurately calculate the value of the precession of the planets, but the lunar-solar precession has to be determined from observations in almost the same way as Hipparchus first did - by changes in the planets of the solar system.

Precession and nutation of the earth's axis (the scale of nutational oscillations is enlarged for clarity) and the declination of stars. This method is simpler and more reliable than finding the positions of the vernal equinox point among the stars. However, the matter is complicated by the fact that all stars have their own motions, which also affect their declinations, and it is necessary to carefully study and exclude these motions from the observed declinations of stars. It is especially difficult to exclude systematic movements of stars caused by the movement of the Sun in space and the rotation of the Galaxy.

Great work on precise definition The values ​​of general precession were carried out at the end of the last century by the American astronomer Simon Newcomb. The value he obtained was approved in 1896 international commission, although now we know that the definition of this important constant, made almost half a century earlier by the Pulkovo astronomer, and subsequently the director of the Pulkovo Observatory O. V. Struve, is more accurate. The value of the total precession calculated by Newcome for the year 1900 is: 50.2564" + 0.000222" T (the second term gives the annual change, T is the number of years that have passed since the beginning of 1900). Newcome's constant precession was used by all astronomers for 80 years. Only in 1976 the XVI Congress of the International astronomical union in Grenoble adopted a new value for 2000: 50.290966" + 0.0002222" T. The old value for 2000 (50.2786") is 0.0124" less than the new one. In conclusion, we describe the method for determining constant precession, developed in last decades. We have already wondered how to find on the celestial sphere fixed point to justify the zero point of right ascensions. Back in 1806, the French astronomer and mathematician Pierre Laplace expressed the idea that weak and distant nebulous spots visible through telescopes in many places in the sky have the smallest, vanishingly small proper motions. Laplace considered them to be large star systems, distant from us by huge distances. Subsequently, Laplace, trying to substantiate his cosmogonic hypothesis, changed his opinion about the nature of nebulae. He believed that this was planetary systems, which are in the stage of formation, that is, formations that are much smaller and closer to us. Now we know that Laplace’s first opinion is correct, but this assumption was not paid attention at the time, and there was no justification for it then. The practical implementation of Laplace's idea - to determine the zero point of right ascensions relative to extragalactic nebulae - became possible only after the improvement of astrophotography.

Extragalactic nebulae - galaxies - cannot be considered absolutely motionless. As follows from the theory of the expanding Universe, galaxies are moving away from us at speeds proportional to their distances. If we accept that the transverse linear speeds of the same order of magnitude as the receding velocities, they are approximately 75 km/s per 1 million parsecs, or 3.26 million light years. Then it turns out that the displacements of distant galaxies on the celestial sphere will become noticeable only after millions of years. Thus, galaxies can serve as a basis inertial system coordinates - a system that has no rotation, but only translational rectilinear movement(“Earth and the Universe”, No. 5, 1967, pp. 14-24.-Ed.). Strictly speaking, the movement should be uniform, but we do not have a way to detect unevenness and therefore are forced to ignore it.

Only in the 30s of this century did Pulkovo and Moscow astronomers raise the question of linking the system of stellar positions to distant galaxies. The proposal of Soviet astronomers was discussed in detail in 1952 at the VIII Congress of the International Astronomical Union in Rome, and soon A. N. Deitch in Pulkovo and S. Vasilevsky at the Lick Observatory in the USA received numerous photographs of galaxies and faint stars. These images could be used as "first epochs", giving the positions of the stars for some initial moments. Repeating such images after 20 or more years served to determine absolute own movements stars relative to galaxies. This work was carried out in Pulkovo, Moscow, Tashkent and at several foreign observatories. Establishing an inertial system using distant galaxies is complicated by the fact that galaxies that have a sufficiently bright and clear core to be reliably measured on photographic negatives are no brighter than the 15th magnitude. The stars “attached” to them are approximately the same size. For practice, the provisions are interesting bright stars- from the 1st to the 6th or 7th magnitude, the brilliance of which is tens of thousands of times greater than that of stars of the 15th magnitude. Therefore, it is necessary to re-photograph areas of the sky and make the necessary alignment, often even in two steps, including intermediate stars of approximately 10th magnitude.

Not enough time has passed since the photographs of the “first epochs” were taken to fully take advantage of the new method of determining constant precession. In the future, this method will provide a confident and accurate justification for the inertial coordinate system. And then the position of the vernal equinox point - the zero point of right ascensions - will be “fixed” on the celestial sphere for many millennia.

On Saturday, when everything normal people either they walk around the city center and watch parades, or go out into nature, I sat at home and argued about the climate, the reasons for the change of seasons and all that. The dispute ended in nothing, so I immersed myself in Wikipedia and educational videos in two languages. No, well, I knew that the change of seasons occurs due to the tilt of the axis and the elliptical orbit, and in general I considered myself a fairly savvy person in this matter, but alas, this is not so. For example, I didn’t know that the earth’s axis is not only tilted by 23.5 degrees, it also rotates. This rotation is called precession. She is best seen in GIFs
What does precession of the earth's axis look like?

This is hard to see on the ground, but you can simply observe the precession yourself - simply by launching a top. It also has a rotation axis, and, as I checked yesterday, it also rotates. Or it can be clearly seen on the gyroscope.

True, given our longevity, the results of precession are almost invisible - our axis completes a full rotation in almost 26,000 years. In addition, in addition to the fact that the axis of the earth rotates, it also vibrates (You can also see it on the top, but only in slow motion). This wobble is called nutation, and in the picture it is marked in red). Please note that the earth's axis is not always tilted at 23.5 degrees - the tilt can fluctuate in both directions by 3-8 degrees

It is this nutation that causes changes in the weather, then winter is colder, then warmer, then summer is drier and hotter, then you don’t have to get out of your jackets. The weather changes because of her. By the way, in 2014 it was expected that nutation would be especially strong, but the expectations were not met.
By the way, due to precession, our northern polar star will change relatively soon. In the sense of the star by which we will search for the north (relatively, this is in a couple of thousand years)))
Well, now about eras. And this was also a shock for me. So, first, and, for me, most important. This is NOT the "age of Aquarius". Now is the "era of fishes". This turned out to be a blow for me :) I had never before thought about how exactly eras are counted, how they are counted. Well, remember precession? It is precisely because of this that the cardinal directions are constantly changing for us (I mean in a cosmic sense). Because of this, the sun, although for us it always rises in the east, actually describes a full circle in the sky. And approximately every 2150 years you can see (well, if you live that long))) that on the day of the spring equinox it begins to rise, being among the stars of a new zodiac sign.
We managed to find only a picture, but there is also a video


Video about eras

Video about precession, climate, our elliptical orbit (did you know that our elliptical orbit also rotates?))

Earth movements for big gap time

© Vladimir Kalanov,
website"Knowledge is power."

Precession

In addition to rotation and revolution, the Earth undergoes many other movements that occur over longer periods of time. The most noticeable of them is precession. Precession was discovered by Hipparchus in the 2nd century BC. It represents a very slow movement of the earth's axis of rotation, which, in order to maintain a constant inclination relative to the ecliptic plane, changes its direction in space, describing a conical surface. The cause of precession is the gravity that the Sun and Moon jointly exert on the Earth's equator. Indeed, our planet does not have an ideal spherical shape; it is slightly flattened at the poles. Therefore, the Sun and Moon, which do not lie on the plane of the celestial equator, tend to align the earth's equatorial bulge on their orbital planes. And the Earth, rotating around its axis, is subject to this double gravitational influence. The sum of these forces is such that the axis earth's rotation, which is perpendicular to the equatorial plane, moves in space, like the axis of a children's top. The Earth's rotation axis, changing its position relative to the Earth, Moon and Sun over time, describes a double conical surface, the apex of which is the center of the Earth. About once every 26,000 years, the axis returns to its original position in space. The consequences of this movement are not immediately apparent, but they are very important for astronomy.

Due to precession, the celestial North Pole moves among the constellations, describing a closed circle in approximately 26,000 years

Indeed, due to precession, there is a slow shift in the celestial sphere of the main astronomical reference points: the poles, equinoxes and solstices. Therefore, the North Star, by which today we can determine the position of the celestial North Pole, will lose this function in the future. The North Pole indeed describes a circle in the sky and, for example, in 14000 AD. it will be near the star Vega in the constellation Lyra. In addition, since the axis of rotation is perpendicular to the celestial equator, a shift in the direction of the axis leads to a displacement of the equatorial plane in space, but it nevertheless makes the same declination angle with respect to the ecliptic.

Consequences of precession

The vernal equinox point, determined by the intersection of the celestial equator with the ecliptic, as already mentioned, slowly moves due to the precession of the equinox. Changing the position of the vernal equinox has two consequences, one of which is associated with celestial coordinates, the other with the zodiacal constellations. And indeed, the point of the vernal equinox is the starting point of the right ascension of the luminaries in the equatorial coordinate system. Its movement across the celestial sphere is due to the fact that the coordinates are constantly being adjusted (the right ascension of the luminary is constantly increasing), namely, with the international agreement on coordinates celestial bodies on a fixed date, such as 1950 or 2000. When in ancient times determined the position of objects on the celestial sphere, the point of the vernal equinox was in the constellation Aries. Today, due to precession, the point of the vernal equinox is not in Aries, but in the constellation Pisces. Likewise, there is no longer a correspondence between the 12 zodiac signs defined in ancient times and the corresponding constellations. If, for example, we are talking about the sign of Pisces, we should not think that between February 21 and March 21 the Sun is actually in the constellation Pisces. It's been like that for a long time. But today - no, because due to the precession of the Sun visible from the Earth, this period of time approximately falls on the stay of the Sun in the constellation Aquarius.

Nutations

Precession of the Earth's axis occurs due to the gravitational influence of the Sun and Moon on the Earth (the so-called lunisolar precession). It should be borne in mind that the force of attraction of these two celestial bodies is closely dependent on their distance from the Earth. This fact affects the conical movement, and small vibrations, the so-called nutation, should not be overlooked.

Nutation of the rotation axis

Superimposed on the conical precessional motion, which contributes to the movement of the ecliptic pole (P), oscillatory motion- nutation (N). As a result, the edges of the cone become “wavy”. During nutation, the celestial pole describes a wave-like curve among the stars. Nutations have a period of 18.6 years, their maximum amplitude (maximum angle) is about 9 arc seconds.

The poles move too

The curved lines shown in the figure represent the movement of the Earth's North Pole over several years. This is the "path of the pole."

Earth movements lasting millennia

In addition to those described, the Earth slowly, over thousands of years, makes other movements. For example, due to the attraction of other bodies of the solar system, with a periodicity of approximately 92 thousand years, the very shape of the earth’s orbit changes, becoming more or less elongated.

Over time, the angle of the earth's axis also changes. Just a little bit, and it fluctuates from 21°55" to 24°20" with a periodicity of approximately 41 thousand years. Today, as mentioned above, this angle is 23°27".

Precession, changes in the eccentricity of the orbit and the angle of inclination of the earth's axis affect the climate and the change of seasons because the illumination of the earth's hemispheres changes. By the way, it is very likely that these minor displacements are associated with the ice ages that once shook our planet. But in any case, the quantity solar energy reaching the earth's surface remains approximately the same; only its distribution changes.

Dear visitors!

You have probably observed the rotation of a top more than once and noticed that its axis is practically never stationary. Under the influence of gravity, in accordance with the laws of rotational motion, the axis of the top moves, describing a conical surface.

The earth is a big top. And its axis of rotation, under the influence of the gravitational forces of the Moon and the Sun on the equatorial excess (as is known, the Earth is flattened and, thus, there seems to be more matter located at the equator than at the poles) also rotates slowly.

The Earth's rotation axis describes a cone with an angle of 23.5° near the ecliptic axis, as a result of which the celestial pole moves around the ecliptic pole in a small circle, making one revolution in approximately 26,000 years. This movement is called precession.

The consequence of precession is a gradual shift of the point of the vernal equinox towards the apparent movement of the Sun by 50.3" per year. For this reason, the Sun annually enters the point of the vernal equinox 20 minutes earlier than it makes a full revolution in the sky.

As a result of precession, the pattern of daily rotation of the starry sky slowly changes: about 4600 years ago, the celestial pole was near the star a Draco, now it is located near the North Star, and after 2000 years the pole star will be near Cepheus. After 12,000 years, the right to be called polar will pass to the star Vega (α Lyrae), which is currently 51° from the pole.

Changing the position of the celestial equator and celestial pole, as well as moving the vernal equinox point causes a change in the equatorial and ecliptic celestial coordinates. Therefore, when giving the coordinates of celestial bodies in catalogs or depicting them on maps, they must indicate the epoch, i.e., the moment in time for which the positions of the equator and the vernal equinox points were taken when determining the coordinate system.

The phenomenon of precession was discovered in the 2nd century. BC e. by the Greek astronomer Hipparchus when comparing the longitudes of stars determined by him from observations with the longitudes of the same stars found 150 years before him by the Greek astronomers Timocharis and Aristillus. To a large extent, precession occurs under the influence of the gravitational force of the Moon.

The forces that cause precession, due to changes in the position of the Sun and Moon relative to the Earth, are constantly changing. Therefore, along with the movement of the Earth’s axis of rotation along the cone, its small vibrations, called nutation, are observed. The largest of these oscillations has an amplitude of 9.2" and a period of 18.6 years. Under the influence of precession and nutation, the celestial pole describes a complex wave-like curve among the stars.

The rate of change in the coordinates of stars due to precession depends on the position of the stars on the celestial sphere. The declinations of different stars change over the course of a year by values ​​from +20" to -20" depending on right ascension. Right ascensions change in a more complex way due to precession, and their corrections depend on both the right ascensions and the declinations of the stars. For near-polar stars, right ascensions can change quite noticeably even over short intervals

time. For example, the right ascension of the North Star changes by almost a whole degree over 10 years. Precession tables are published in astronomical yearbooks and calendars.

It should be borne in mind that precession and nutation only change the orientation of the Earth's rotation axis in space and do not affect the position of this axis in the Earth's body. Therefore, neither the latitude nor the longitude of places on the earth’s surface change due to precession and nutation and these phenomena do not affect the climate.