Earth's daily rotation- rotation of the Earth around its axis with a period of one sidereal day, the observed manifestation of which is diurnal rotation celestial sphere. The rotation of the Earth is from west to east. When viewed from the Pole Star or the North Pole of the Ecliptic, the rotation of the Earth occurs counterclockwise.
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V = (R e R p R p 2 + R e 2 tg 2 φ + R p 2 h R p 4 + R e 4 tg 2 φ) ω (\displaystyle v=\left((\frac (R_(e) \,R_(p))(\sqrt ((R_(p))^(2)+(R_(e))^(2)\,(\mathrm (tg) ^(2)\varphi )))) +(\frac ((R_(p))^(2)h)(\sqrt ((R_(p))^(4)+(R_(e))^(4)\,\mathrm (tg) ^ (2)\varphi )))\right)\omega ), where R e (\displaystyle R_(e))= 6378.1 km - equatorial radius, R p (\displaystyle R_(p))= 6356.8 km - polar radius.
- An aircraft flying at this speed from east to west (at an altitude of 12 km: 936 km / h at the latitude of Moscow, 837 km / h at the latitude of St. Petersburg) will be at rest in the inertial frame of reference.
- The superposition of the Earth's rotation around its axis with a period of one sidereal day and around the Sun with a period of one year leads to the inequality of solar and sidereal days: the length of the average solar day is exactly 24 hours, which is 3 minutes 56 seconds longer than the sidereal day.
Physical meaning and experimental confirmation
The physical meaning of the rotation of the Earth around its axis
Since any movement is relative, it is necessary to indicate a specific frame of reference, relative to which the movement of a body is being studied. When they say that the earth rotates around an imaginary axis, it means that it makes rotary motion relative to any inertial frame reference, and the period of this rotation is equal to sidereal days - the period of a complete revolution of the Earth (celestial sphere) relative to the celestial sphere (Earth).
All experimental proofs of the Earth's rotation around its axis are reduced to the proof that the frame of reference associated with the Earth is a non-inertial frame of reference of a special type - a frame of reference that performs rotational motion relative to inertial frames of reference.
Unlike inertial motion (that is, uniform rectilinear motion relative to inertial frames of reference), in order to detect non-inertial motion of a closed laboratory, it is not necessary to make observations over external bodies, - such movement is detected with the help of local experiments (that is, experiments performed inside this laboratory). In this sense of the word, non-inertial motion, including the rotation of the Earth around its axis, can be called absolute.
Forces of inertia
Effects of centrifugal force
Acceleration dependency free fall from geographic latitude. Experiments show that the acceleration free fall depends on geographic latitude: the closer to the pole, the greater it is. This is explained by the action centrifugal force. First, points on the earth's surface located at higher latitudes are closer to axes of rotation and, consequently, when approaching the pole, the distance r (\displaystyle r) decreases from the axis of rotation, reaching zero at the pole. Secondly, with increasing latitude, the angle between the centrifugal force vector and the horizon plane decreases, which leads to a decrease in the vertical component of the centrifugal force.
This phenomenon was discovered in 1672, when the French astronomer Jean Richet, while on an expedition to Africa, discovered that near the equator pendulum clock go slower than in Paris. Newton soon explained this by saying that the period of a pendulum is inversely proportional to square root from the acceleration due to gravity, which decreases at the equator due to the action of centrifugal force.
Flattening of the Earth. The influence of centrifugal force leads to the oblateness of the Earth at the poles. This phenomenon was predicted by Huygens and Newton in late XVII century, was first discovered by Pierre de Maupertuis in the late 1730s as a result of processing data from two French expeditions specially equipped to solve this problem in Peru (led by Pierre Bouguer and Charles de la Condamine) and Lapland (led by Alexis Clairaut and himself Maupertuis).
Coriolis Force Effects: Laboratory Experiments
This effect should be most clearly expressed at the poles, where the period of complete rotation of the pendulum plane is equal to the period of the Earth's rotation around its axis (sidereal days). IN general case, the period is inversely proportional to the sine of geographic latitude , at the equator the plane of oscillation of the pendulum is unchanged.
Gyroscope- a rotating body with a significant moment of inertia retains an angular momentum if there are no strong perturbations. Foucault, who was tired of explaining what happened to a Foucault pendulum not at the pole, developed another demonstration: a suspended gyroscope maintained its orientation, which means it slowly rotated relative to the observer.
Deflection of projectiles during gun firing. Another observable manifestation of the Coriolis force is the deflection of the trajectories of projectiles (to the right in the northern hemisphere, to the left in the southern hemisphere) fired in a horizontal direction. From point of view inertial system reference, for projectiles fired along the meridian , this is due to the dependence of the linear velocity of the Earth's rotation on geographic latitude: when moving from the equator to the pole, the projectile retains the horizontal component of the velocity unchanged, while line speed The rotation of points on the earth's surface decreases, which leads to a displacement of the projectile from the meridian in the direction of the Earth's rotation. If the shot was fired parallel to the equator, then the displacement of the projectile from the parallel is due to the fact that the trajectory of the projectile lies in the same plane with the center of the Earth, while points on the earth's surface move in a plane perpendicular to the axis of rotation of the Earth. This effect (for the case of firing along the meridian) was predicted by Grimaldi in the 40s of the 17th century. and first published by Riccioli in 1651.
Deviation of freely falling bodies from the vertical. ( ) If the speed of the body has a large vertical component, the Coriolis force is directed to the east, which leads to a corresponding deviation of the trajectory of a body freely falling (without initial velocity) from a high tower. When considered in an inertial frame of reference, the effect is explained by the fact that the top of the tower relative to the center of the Earth moves faster than the base, due to which the trajectory of the body turns out to be a narrow parabola and the body is slightly ahead of the base of the tower.
Eötvös effect. At low latitudes, the Coriolis force, when moving along the earth's surface, is directed in the vertical direction and its action leads to an increase or decrease in the acceleration of free fall, depending on whether the body moves to the west or east. This effect is called the Eötvös effect in honor of the Hungarian physicist Lorand Åtvös, who experimentally discovered it at the beginning of the 20th century.
Experiments using the law of conservation of angular momentum. Some experiments are based on the law conservation momentum momentum: in an inertial frame of reference, the value of the momentum (equal to the product of the moment inertia and the angular velocity of rotation) under the action internal forces does not change. If at some initial time the installation is motionless relative to the Earth, then the speed of its rotation relative to the inertial reference frame is equal to the angular velocity of the Earth's rotation. If you change the moment of inertia of the system, then the angular velocity of its rotation should change, that is, rotation relative to the Earth will begin. In a non-inertial frame of reference associated with the Earth, rotation occurs as a result of the action of the Coriolis force. This idea was proposed by the French scientist Louis Poinsot in 1851.
The first such experiment was carried out by Hagen in 1910: two weights on a smooth crossbar were installed motionless relative to the Earth's surface. Then the distance between the loads was reduced. As a result, the installation came into rotation. An even more illustrative experiment was made by the German scientist Hans Bucka in 1949. A rod about 1.5 meters long was installed perpendicular to a rectangular frame. Initially, the rod was horizontal, the installation was stationary relative to the Earth. The rod was then brought into vertical position, which led to a change in the moment of inertia of the installation by about 10 4 times and its rapid rotation with an angular velocity 10 4 times higher than the Earth's rotation speed .
Funnel in the bath.
Since the Coriolis force is very weak, it has negligible effect on the direction of the swirl of water when draining in a sink or bathtub, so in general the direction of rotation in a funnel is not related to the rotation of the Earth. Only in carefully controlled experiments is it possible to separate the effect of the Coriolis force from other factors: in the northern hemisphere, the funnel will be twisted counterclockwise, in the southern hemisphere - vice versa.
Effects of the Coriolis Force: Phenomena in the Environment
Optical experiments
A number of experiments demonstrating the rotation of the Earth are based on the Sagnac effect: if the ring interferometer rotates, then due to relativistic effects, a phase difference appears in the oncoming beams
Δ φ = 8 π A λ c ω , (\displaystyle \Delta \varphi =(\frac (8\pi A)(\lambda c))\omega ,)where A (\displaystyle A)- the area of the projection of the ring on the equatorial plane (the plane perpendicular to the axis of rotation), c (\displaystyle c)- speed of light, ω (\displaystyle \omega )- angular speed of rotation. To demonstrate the rotation of the Earth, this effect was used by the American physicist Michelson in a series of experiments carried out in 1923-1925. In modern experiments using the Sagnac effect, the rotation of the Earth must be taken into account to calibrate ring interferometers.
There are a number of other experimental demonstrations of the Earth's diurnal rotation.
Uneven rotation
Precession and nutation
History of the idea of the daily rotation of the Earth
Antiquity
The explanation of the daily rotation of the sky by the rotation of the Earth around its axis was first proposed by the representatives of the Pythagorean school, the Syracusans Hicket and Ekfant. According to some reconstructions, the Pythagorean Philolaus of Croton (5th century BC) also claimed the rotation of the Earth. A statement that can be interpreted as an indication of the rotation of the Earth is contained in the Platonic dialogue Timaeus .
However, almost nothing is known about Giketa and Ekfant, and even their very existence is sometimes questioned. According to the opinion of most scientists, the Earth in the system of the world of Philolaus did not rotate, but forward movement around the Central Fire. In his other writings, Plato follows the traditional view of the immobility of the Earth. However, we have received numerous evidence that the idea of the rotation of the Earth was defended by the philosopher Heraclides Pontic (4th century BC). Probably, another assumption of Heraclid is connected with the hypothesis of the rotation of the Earth around its axis: each star is a world that includes earth, air, ether, and all this is located in infinite space. Indeed, if the daily rotation of the sky is a reflection of the rotation of the Earth, then the premise of considering the stars as being on the same sphere disappears.
About a century later, the assumption of the rotation of the Earth became integral part the first, proposed by the great astronomer Aristarchus of Samos (3rd century BC). Aristarchus was supported by the Babylonian Seleucus (II century BC), as well as Heraclid Pontic, who considered the Universe to be infinite. The fact that the idea of the daily rotation of the Earth had its supporters as early as the 1st century A.D. e., some statements of the philosophers Seneca, Derkillid, astronomer Claudius Ptolemy testify. The overwhelming majority of astronomers and philosophers, however, did not doubt the immobility of the Earth.
Arguments against the idea of the Earth's motion are found in the works of Aristotle and Ptolemy. So, in his treatise About Heaven Aristotle justifies the immobility of the Earth by the fact that on a rotating Earth, bodies thrown vertically upwards could not fall to the point from which their movement began: the surface of the Earth would move under the thrown body. Another argument in favor of the immobility of the Earth, given by Aristotle, is based on his physical theory: the Earth is a heavy body, and heavy bodies tend to move towards the center of the world, and not rotate around it.
It follows from the work of Ptolemy that the supporters of the hypothesis of the rotation of the Earth answered these arguments that both the air and all terrestrial objects move along with the Earth. Apparently, the role of air in this reasoning is fundamentally important, since it is understood that it is precisely its movement along with the Earth that hides the rotation of our planet. Ptolemy counters this by saying that
bodies in the air will always seem lagging behind ... And if the bodies rotated together with the air as a whole, then none of them would seem to be ahead of the other or lagging behind it, but would remain in place, in flight and throwing it would not make deviations or movements to another place, such as we see with our own eyes taking place, and they would not slow down or accelerate at all, because the Earth is not stationary.
Middle Ages
India
The first of the medieval authors, who suggested that the Earth rotates around its axis, was the great Indian astronomer and mathematician Aryabhata (late V - early VI centuries). He formulates it in several places in his treatise. Ariabhatia, for example:
Just as a person on a ship moving forward sees fixed objects moving backward, so an observer ... sees fixed stars moving in a straight line to the west.
It is not known whether this idea belongs to Aryabhata himself or whether he borrowed it from ancient Greek astronomers.
Aryabhata was supported by only one astronomer, Prthudaka (9th century). Most Indian scientists have defended the immobility of the Earth. Thus, the astronomer Varahamihira (6th century) argued that on a rotating Earth, birds flying in the air could not return to their nests, and stones and trees would fly off the Earth's surface. The eminent astronomer Brahmagupta (6th century) also repeated the old argument that a body that fell from high mountain, but could sink to its base. At the same time, however, he rejected one of Varahamihira's arguments: in his opinion, even if the Earth rotated, objects could not break away from it due to their gravity.
Islamic East
The possibility of the Earth's rotation was considered by many scientists of the Muslim East. Thus, the famous geometer al-Sijizi invented the astrolabe, the principle of operation of which is based on this assumption. Some Islamic scholars (whose names have not come down to us) even found The right way refutation of the main argument against the rotation of the Earth: the verticality of the trajectories of falling bodies. In essence, at the same time, the principle of superposition of movements was stated, according to which any movement can be decomposed into two or more components: with respect to the surface of the rotating Earth, the falling body moves along a plumb line, but the point that is the projection of this line onto the Earth’s surface would be transferred to it. rotation. This is evidenced by the famous scientist-encyclopedist al-Biruni, who himself, however, was inclined to the immobility of the Earth. In his opinion, if some additional force acts on the falling body, then the result of its action on the rotating Earth will lead to some effects that are not actually observed.
File:Al-Tusi Nasir.jpeg
Nasir ad-Din at-Tusi
Among the scientists of the XIII-XVI centuries, associated with the Maraga and Samarkand observatories, a discussion unfolded about the possibility of an empirical justification for the immobility of the Earth. Thus, the famous astronomer Kutb ad-Din ash-Shirazi (XIII-XIV centuries) believed that the immobility of the Earth could be verified by experiment. On the other hand, the founder of the Maraga observatory, Nasir ad-Din at-Tusi, believed that if the Earth rotated, then this rotation would be separated by a layer of air adjacent to its surface, and all movements near the Earth’s surface would occur in exactly the same way as if the Earth was motionless. He justified this with the help of observations of comets: according to Aristotle, comets are a meteorological phenomenon in the upper atmosphere; nevertheless, astronomical observations show that comets take part in the daily rotation of the celestial sphere. Consequently, the upper layers of the air are entrained by the rotation of the sky, and therefore the lower layers can also be entrained by the rotation of the Earth. Thus, the experiment cannot answer the question of whether the Earth rotates. However, he remained a supporter of the immobility of the Earth, as it was in line with the philosophy of Aristotle.
Most of the Islamic scholars of a later time (al-Urdi, al-Qazvini, an-Naysaburi, al-Jurdjani, al-Birjandi and others) agreed with at-Tusi that all physical phenomena on a rotating and motionless Earth would result in the same way. However, the role of air in this case was no longer considered fundamental: not only air, but also all objects are transported by the rotating Earth. Therefore, to justify the immobility of the Earth, it is necessary to involve the teachings of Aristotle.
A special position in these disputes was taken by the third director of the Samarkand Observatory, Alauddin Ali al-Kushchi (XV century), who rejected the philosophy of Aristotle and considered the rotation of the Earth physically possible. In the 17th century, the Iranian theologian and scholar-encyclopedist Baha al-Din al-Amili came to a similar conclusion. In his opinion, astronomers and philosophers have not provided sufficient evidence to disprove the rotation of the Earth.
latin west
A detailed discussion of the possibility of the Earth's motion is widely contained in the writings of the Parisian scholastics Jean Buridan, Albert of Saxony, and Nicholas Orem (second half of the 14th century). The most important argument in favor of the rotation of the Earth, and not the sky, given in their works, is the smallness of the Earth in comparison with the Universe, which makes attributing the daily rotation of the sky of the Universe to the highest degree unnatural.
However, all of these scientists ultimately rejected the rotation of the Earth, albeit on different grounds. Thus, Albert of Saxony believed that this hypothesis is not capable of explaining the observed astronomical phenomena. Buridan and Orem rightly disagreed with this, according to which celestial phenomena should occur in the same way regardless of what makes the rotation, the Earth or the Cosmos. Buridan could find only one significant argument against the rotation of the Earth: arrows fired vertically upwards fall down a sheer line, although with the rotation of the Earth, in his opinion, they would have to lag behind the movement of the Earth and fall to the west of the point of the shot.
But even this argument was rejected by Oresme. If the Earth rotates, then the arrow flies vertically upwards and at the same time moves to the east, being captured by the air rotating with the Earth. Thus, the arrow must fall in the same place from which it was fired. Although here again the entraining role of air is mentioned, in reality it does not play a special role. This is illustrated by the following analogy:
Similarly, if the air were closed in a moving ship, then it would appear to a person surrounded by this air that the air is not moving ... If a person were in a ship moving at high speed to the east, not knowing about this movement, and if he stretched out his hand in a straight line along the mast of the ship, it would have seemed to him that his hand was making rectilinear motion; in the same way, according to this theory, it seems to us that the same thing happens to an arrow when we shoot it vertically up or vertically down. Inside a ship moving eastward at high speed, all kinds of motion can take place: longitudinal, transverse, down, up, in all directions - and they seem exactly the same as when the ship is stationary.
Further, Orem gives a formulation that anticipates the principle of relativity:
I conclude, therefore, that it is impossible to demonstrate by any experience whatsoever that the heavens have a diurnal movement and that the earth does not.
However, Oresme's final verdict on the possibility of the Earth's rotation was negative. The basis for this conclusion was the text of the Bible:
However, so far everyone supports and I believe that it is [Heaven] and not the Earth that moves, for "God created the circle of the Earth that will not shake", despite all the opposite arguments.
The possibility of a daily rotation of the Earth was also mentioned by medieval European scientists and philosophers of a later time, but no new arguments that were not contained in Buridan and Orem were added.
Thus, practically none of the medieval scientists accepted the hypothesis of the rotation of the Earth. However, in the course of its discussion by scientists of the East and West, many profound thoughts were expressed, which will then be repeated by scientists of the New Age.
Renaissance and Modern times
In the first half of the 16th century, several works were published that claimed that the reason for the daily rotation of the sky is the rotation of the Earth around its axis. One of them was the treatise of the Italian Celio Calcagnini "On the fact that the sky is motionless, and the Earth rotates, or on the perpetual motion of the Earth" (written around 1525, published in 1544). He did not produce great impression on contemporaries, since by that time the fundamental work of the Polish astronomer Nicholas Copernicus “On the rotations of the celestial spheres” (1543) had already been published, where the hypothesis of the daily rotation of the Earth became part of the heliocentric system of the world, like Aristarchus Samossky. Copernicus previously expressed his thoughts in a small handwritten essay. Small Comment(not earlier than 1515). Two years earlier than the main work of Copernicus, the work of the German astronomer Georg Joachim Rhetik was published. First Narrative(1541), where the theory of Copernicus is popularly expounded.
In the 16th century, Copernicus was fully supported by the astronomers Thomas Digges, Retik, Christoph Rothman, Michael Möstlin, the physicists Giambatista Benedetti, Simon Stevin, the philosopher Giordano Bruno, the theologian Diego de Zuniga. Some scientists accepted the rotation of the Earth around its axis, rejecting its forward movement. This was the position of the German astronomer Nicholas Reimers, also known as Ursus, as well as the Italian philosophers Andrea Cesalpino and Francesco Patrici. The point of view of the outstanding physicist William Gilbert, who supported axial rotation Earth, but did not speak about its forward movement. At the beginning of the 17th century heliocentric system world (including the rotation of the Earth around its axis) received impressive support from Galileo Galilei and Johann Kepler. The most influential opponents of the idea of the Earth's motion in the 16th - early 17th centuries were the astronomers Tycho Brage and Christopher Clavius.
The hypothesis of the rotation of the Earth and the formation of classical mechanics
In fact, in the XVI-XVII centuries. the only argument in favor of the axial rotation of the Earth was that in this case there is no need to attribute huge rotational speeds to the stellar sphere, because even in antiquity it was already reliably established that the size of the Universe significantly exceeds the size of the Earth (this argument was also contained by Buridan and Orem) .
Against this hypothesis, arguments based on the dynamic ideas of that time were expressed. First of all, this is the verticality of the trajectories of falling bodies. Other arguments also appeared, for example, equal firing range in the east and western directions. Answering the question about the unobservability of the effects of diurnal rotation in terrestrial experiments, Copernicus wrote:
Not only the Earth with the water element connected with it rotates, but also a considerable part of the air, and everything that is in any way akin to the Earth, or the air already closest to the Earth, saturated with terrestrial and water matter, follows the same laws of nature as The earth, or has acquired motion, which is communicated to it by the adjoining earth in constant rotation and without any resistance
In this way, leading role in the unobservability of the rotation of the Earth plays the entrainment of air by its rotation. This opinion was shared by the majority of Copernicans in the 16th century.
Supporters of the infinity of the Universe in the 16th century were also Thomas Digges, Giordano Bruno, Francesco Patrici - all of them supported the hypothesis of the rotation of the Earth around its axis (and the first two also around the Sun). Christoph Rothmann and Galileo Galilei believed the stars to be located on different distances from the Earth, although they did not explicitly speak out about the infinity of the Universe. On the other hand, Johannes Kepler denied the infinity of the Universe, although he was a supporter of the rotation of the Earth.
The Religious Context of the Earth Rotation Debate
A number of objections to the rotation of the Earth were associated with its contradictions to the text. Holy Scripture. These objections were of two kinds. Firstly, some places in the Bible were cited to confirm that it is the Sun that makes the daily movement, for example:
The sun rises and the sun sets, and hurries to its place where it rises.
In this case, the axial rotation of the Earth was under attack, since the movement of the Sun from east to west is part of the daily rotation of the sky. A passage from the book of Joshua has often been quoted in this connection:
Jesus called to the Lord on the day that the Lord delivered the Amorites into the hands of Israel, when he beat them in Gibeon, and they were beaten before the face of the sons of Israel, and said before the Israelites: Stop, the sun is over Gibeon, and the moon is over the valley of Avalon. !
Since the command to stop was given to the Sun, and not to the Earth, it was concluded from this that it was the Sun that made the daily movement. Other passages have been cited in support of the Earth's immobility, such as:
You set the ground on solid foundations: it shall not be shaken forever and ever.
These passages were considered contrary to both the notion of the rotation of the Earth around its axis and the revolution around the Sun.
Supporters of the rotation of the Earth (in particular, Giordano Bruno, Johann Kepler and especially Galileo Galilei) defended in several directions. First, they pointed out that the Bible was written in a language understandable ordinary people, and if its authors gave clear scientific point from the point of view of the wording, it would not be able to fulfill its main, religious mission. Thus, Bruno wrote:
In many cases, it is foolish and inexpedient to give much reasoning in accordance with the truth rather than accordingly. this occasion and convenience. For example, if instead of the words: “The sun is born and rises, passes through noon and leans towards Aquilon,” the sage said: “The earth goes in a circle to the east and, leaving the sun that sets, leans towards two tropics, from Cancer to the South, from Capricorn to Aquilo,” then the listeners would begin to think: “How? Does he say the earth is moving? What is this news? In the end, they would have considered him a fool, and he really would have been a fool.
Answers of this kind were given mainly to objections concerning the daily motion of the Sun. Secondly, it was noted that some passages of the Bible should be interpreted allegorically (see the article Biblical Allegorism). So, Galileo noted that if Holy Scripture is taken entirely literally, then it turns out that God has hands, he is subject to emotions such as anger, etc. In general, main idea The defenders of the doctrine of the movement of the Earth were that science and religion have different goals: science considers the phenomena of the material world, guided by the arguments of reason, the goal of religion is the moral improvement of man, his salvation. Galileo quoted Cardinal Baronio in this connection that the Bible teaches how to ascend to heaven, not how the heavens are made.
These arguments were considered catholic church unconvincing, and in 1616 the doctrine of the rotation of the Earth was banned, and in 1631 Galileo was convicted by the court of the Inquisition for his defense. However, outside of Italy, this ban did not significant influence on the development of science and contributed mainly to the fall of the authority of the Catholic Church itself.
It must be added that religious arguments against the movement of the Earth were brought not only by church leaders, but also by scientists (for example, Tycho Brage). On the other hand, the Catholic monk Paolo Foscarini wrote a short essay “Letter on the views of the Pythagoreans and Copernicus on the mobility of the Earth and the immobility of the Sun and on the new Pythagorean system of the universe” (1615), where he expressed considerations close to Galilean, and the Spanish theologian Diego de Zuniga even used the theory of Copernicus to interpret some passages of Scripture (although he later changed his mind). Thus, the conflict between theology and the doctrine of the movement of the Earth was not so much a conflict between science and religion as such, but a conflict between the old (to early XVII centuries already obsolete) and new methodological principles underlying science.
Significance of the hypothesis of the rotation of the Earth for the development of science
Making sense scientific problems raised by the theory of the rotating Earth, contributed to the discovery of the laws of classical mechanics and the creation of a new cosmology, which is based on the idea of the infinity of the Universe. Discussed during this process, the contradictions between this theory and the literalist reading of the Bible contributed to the demarcation of natural science and religion.
see also
Notes
- Poincare, About science, from. 362-364.
- This effect was first observed
Hello dear readers! Today I would like to touch on the topic of the Earth and, and I thought that a post on how the Earth rotates will be useful to you 🙂 After all, day and night, and also the seasons, depend on it. Let's get to know everyone better.
Our planet rotates on its axis and around the sun. When it makes one revolution around its axis, one day passes, and when it circles the Sun, one year. More on this below:
Earth axis.
Earth's axis (axis of rotation of the Earth) - this is a straight line around which the daily rotation of the Earth occurs; this line passes through the center and intersects the surface of the Earth.
The tilt of the Earth's axis of rotation.
The axis of rotation of the Earth is inclined to the plane at an angle of 66°33´; thanks to this happens . When the Sun is over the Tropic of the North (23°27´ N), summer begins in the Northern Hemisphere, and the Earth is at its furthest distance from the Sun.
When the Sun rises over the Tropic of the South (23°27´ S), summer begins in the Southern Hemisphere.
In the Northern Hemisphere, winter begins at this time. The attraction of the Moon, the Sun and other planets does not change the angle of the earth's axis, but leads to the fact that it moves along a circular cone. This movement is called precession.
The North Pole is pointing towards the North Star. The earth's axis over the next 12,000 years, as a result of precession, will pass approximately halfway, and will be directed to the star Vega.
About 25,800 years constitutes a complete cycle of precession and significantly influences the climate cycle.
Twice a year, when the Sun is directly over the equator, and twice a month, when the Moon is in a similar position, the attraction due to precession decreases to zero and there is a periodic increase and decrease in the rate of precession.
Such oscillatory movements of the earth's axis are known as nutation, which peaks every 18.6 years. In terms of its impact on climate, this periodicity ranks second after change of seasons.
Rotation of the Earth around its axis.
Earth's daily rotation the movement of the Earth counterclockwise, or from west to east, as viewed from the North Pole of the world. The rotation of the Earth determines the length of the day and causes day and night to change.
The Earth makes one revolution around its axis in 23 hours 56 minutes and 4.09 seconds. During the period of one revolution around the Sun, the Earth makes approximately 365 ¼ revolutions, which is one year or 365 ¼ days.
Every four years, another day is added to the calendar, because for each such turn, except for a whole day, another quarter of a day is spent. The rotation of the Earth gradually slows down the gravitational pull of the Moon, and prolongs the day by about 1/1000 of every century.
Judging by the geological data, the rate of rotation of the Earth could change, but not more than 5%.
Around the Sun, the Earth rotates in an elliptical orbit, close to circular, at a speed of about 107,000 km / h in the direction from west to east. The average distance to the Sun is 149,598 thousand km, and the difference between the smallest and the largest distance is 4.8 million km.
The eccentricity (deviation from the circle) of the earth's orbit changes slightly over a cycle of 94 thousand years. It is believed that the formation of a complex climatic cycle is facilitated by changes in the distance to the Sun, and the advance and retreat of glaciers during ice ages are associated with its individual stages.
Everything in our vast universe is very complex and precise. And our Earth is just a point in it, but this is our home, which we learned a little more about from a post about how the Earth rotates. See you in new posts about the study of the Earth and the Universe🙂
Why does day and night change? Of course, you have seen sunrises and sunsets more than once. Why do you think they happen? Does the sun stop shining? A simple experiment will help you understand this. If a lighted flashlight is directed to the side of an ordinary school globe in a dark room, then one half will be illuminated, and the other half will be in the shade. In the same way, the rays of the Sun illuminate our planet in the eternal darkness of space.
The imaginary axis of the Earth runs in a straight line from the North Pole to the South. The Earth revolves around it from west to east and exposes the Sun to one side, then the other. On the illuminated side - day, on the opposite side at the same time - night. around its axis determines the change of day and night.
The Earth makes a complete rotation around its axis in 23 hours and 56 minutes, that is, in a day. A day is a unit of time, approximately equal to the period of rotation of the Earth around its axis. The day is usually divided into night, morning, afternoon and evening.
standard time
Due to the rotation of the Earth around its axis, the time of day at different points the globe cannot be the same. Therefore, for convenience, time zones were introduced: the earth's surface was divided by meridians into 24 zones every 15 degrees of longitude.
The time of day within the same time zone is called belt. The time difference between the zones is one hour. The origin of time zones is considered to be the Greenwich meridian passing through the city of Greenwich (this is in, not far from London, where the Greenwich Observatory is located). From it, the belts are counted to the east. In other words, when moving to eastbound standard time increases, and in the western - decreases.
If it is 12 o'clock at Greenwich, then it is 13 o'clock in the first zone to the east of it, and 11 o'clock in the first zone to the west. The beginning of a new day is considered the 12th time zone. Thus, when on Far East a new day begins, in the Western Hemisphere the previous one still lasts.
In 2011, the President of our country signed the federal law on the allocation of nine time zones in Russia. The boundaries of these zones are determined taking into account the boundaries of the republics, territories and regions Russian Federation. The time zone is set to the same time. In the same 2011, the transition to winter time was canceled on the territory of Russia.
Since ancient times, people have been interested in why the night is replaced by day, winter in spring, and summer in autumn. Later, when the answers to the first questions were found, scientists began to consider the Earth as an object in more detail, trying to find out how fast the Earth rotates around the Sun and around its axis.
Earth Movement
Everything celestial bodies are in motion, the Earth is no exception. Moreover, it simultaneously has an axial movement and movement around the Sun.
To visualize the motion of the earth, just look at the top, simultaneously rotating around the axis and quickly moving across the floor. Without this movement, the Earth would not be habitable. So, our planet, without rotation around its axis, would be constantly turned towards the Sun with one of its sides, on which the air temperature would reach +100 degrees, and all the water available in this area would turn into steam. On the other side, the temperature would be constantly below zero and the entire surface of this part would be covered with ice.
Orbit of rotation
Rotation around the Sun follows a certain trajectory - an orbit, which was established due to the attraction of the Sun and the speed of our planet. If the attraction were several times stronger or the speed was much lower, then the Earth would fall into the Sun. What if attraction was gone? or greatly decreased, then the planet, driven by its centrifugal force, flew off tangentially into space. It would be like if an object tied to a rope is rotated overhead, and then abruptly released.The trajectory of the Earth's motion has the shape of an ellipse, not a perfect circle, and the distance to the sun varies throughout the year. In January, the planet approaches the point closest to the luminary - it is called perihelion - and is 147 million km away from the luminary. And in July, the Earth moves away from the sun by 152 million km, approaching a point called aphelion. 150 million km is taken as the average distance.
The earth moves in its orbit from west to east, which corresponds to the "counterclockwise" direction.
1 turn around the center solar system The Earth needs 365 days 5 hours 48 minutes 46 seconds (1 astronomical year). But for convenience, it is customary to consider 365 days for a calendar year, and the remaining time “accumulates” and adds one day to each leap year.The orbital distance is 942 million km. Based on the calculations, the speed of the Earth is 30 km per second or 107,000 km/h. For people, it remains invisible, since all people and objects move in the same way in the coordinate system. And yet it is very large. For example, the highest speed of a racing car is 300 km/h, which is 365 times slower than the speed of the Earth in its orbit.
However, the value of 30 km/s is not constant due to the fact that the orbit is an ellipse. The speed of our planet fluctuates a bit throughout the journey. Biggest difference is reached when passing the points of perihelion and aphelion and is 1 km/s. That is, the accepted speed of 30 km/s is the average.
Axial rotation
The earth's axis is a conditional line that can be drawn from north to south pole. It passes at an angle of 66 ° 33 relative to the plane of our planet. One revolution occurs in 23 hours 56 minutes and 4 seconds, this time is indicated by a sidereal day.
The main result of axial rotation is the change of day and night on the planet. In addition, due to this movement:
- The earth has a shape with oblate poles;
- bodies (river flow, wind) moving in a horizontal plane are somewhat displaced (to the left in the Southern Hemisphere, to the right in the Northern Hemisphere).
Axial movement speed per different areas is significantly different. The highest at the equator is 465 m / s or 1674 km / h, it is called linear. Such speed, for example, in the capital of Ecuador. In areas north or south of the equator, the rotation speed decreases. For example, in Moscow it is almost 2 times lower. These speeds are called angular., their exponent becomes smaller as they approach the poles. At the poles themselves, the speed is zero, that is, the poles are the only parts of the planet that are without movement relative to the axis.It is the location of the axis at a certain angle that determines the change of seasons. Being in this position, different areas planets receive different amounts of heat different time. If our planet were located strictly vertically relative to the Sun, then there would be no seasons at all, since those illuminated by the luminary in daytime northern latitudes received as much heat and light as the southern latitudes.
Axial rotation is influenced by the following factors:
- seasonal changes (precipitation, atmospheric movement);
- tidal waves against the direction of axial movement.
These factors slow down the planet, as a result of which its speed decreases. The indicator of this decrease is very small, only 1 second in 40,000 years, however, over 1 billion years, the day lengthened from 17 to 24 hours.
The motion of the Earth continues to be studied to this day.. This information helps to create more accurate star charts, as well as to determine the relationship of this movement with natural processes on our planet.
The earth is constantly in motion, revolving around the sun and around its own axis. This movement and the constant tilt of the Earth's axis (23.5°) determines many of the effects that we observe as normal phenomena: night and day (due to the rotation of the Earth on its axis), the change of seasons (due to the tilt of the Earth's axis), and different climate in various fields. Globes can be rotated and their axis has an inclination like the Earth's axis (23.5 °), so with the help of a globe you can trace the movement of the Earth around its axis quite accurately, and with the help of the "Earth - Sun" system you can trace the movement of the Earth around the Sun.
Rotation of the Earth around its axis
The earth rotates on its own axis from west to east (counterclockwise as viewed from the North Pole). It takes Earth 23 hours, 56 minutes, and 4.09 seconds to complete one full turn around its own axis. Day and night are due to the rotation of the earth. The angular velocity of the Earth's rotation around its axis, or the angle by which any point on the Earth's surface turns, is the same. It is 15 degrees in one hour. But the linear speed of rotation anywhere on the equator is approximately 1,669 kilometers per hour (464 m/s), decreasing to zero at the poles. For example, the rotation speed at a latitude of 30° is 1445 km/h (400 m/s).
We do not notice the rotation of the Earth for the simple reason that all the objects around us are moving in parallel and simultaneously with us at the same speed and there are no "relative" movements of objects around us. If, for example, a ship moves evenly, without acceleration and deceleration across the sea in calm weather, without waves on the surface of the water, we will not feel at all how such a ship moves if we are in a cabin without a porthole, since all objects inside the cabin will be move in parallel with us and the ship.Movement of the Earth around the Sun
While the Earth rotates on its own axis, it also rotates around the Sun from west to east counterclockwise, when viewed from north pole. It takes the Earth one sidereal year (about 365.2564 days) to complete one complete revolution around the Sun. The path of the Earth around the Sun is called the Earth's orbit. and this orbit is not perfectly round. The average distance from the Earth to the Sun is about 150 million kilometers, and this distance varies up to 5 million kilometers, forming a small oval orbit (ellipse). The point in the Earth's orbit closest to the Sun is called Perihelion. Earth passes this point in early January. The point in the Earth's orbit that is farthest from the Sun is called Aphelion. Earth passes this point in early July.
Since our Earth moves around the Sun in an elliptical trajectory, the orbital speed changes. In July, the speed is minimal (29.27 km/s) and after passing aphelion (upper red dot in the animation) it starts to accelerate, and in January the speed is maximum (30.27 km/s) and starts to slow down after passing perihelion (lower red dot). ).
While the Earth makes one revolution around the Sun, it covers a distance equal to 942 million kilometers in 365 days, 6 hours, 9 minutes and 9.5 seconds, that is, we rush along with the Earth around the Sun at an average speed of 30 km per second (or 107 460 km per hour), and at the same time the Earth rotates around its own axis in 24 hours once (365 times in a year).
In fact, if we consider the movement of the Earth more scrupulously, then it is much more complicated, since various factors influence the Earth: the rotation of the Moon around the Earth, the attraction of other planets and stars.
