The planets are divided according to their apparent movements at the bottom of the group: lower (Mercury, Venus) and upper (all the rest except the Earth).

The movements in the constellations of the lower and upper planets are different. Mercury and Venus are always in the sky, either in the same constellation as the Sun, or in a neighboring one. At the same time, they can be located both east and west of the Sun, but no further than 18-28 ° (Mercury) and 45-48 ° (Venus). The greatest angular distance of a planet from the Sun to the east is called its greatest eastern elongation, to the west - its greatest western elongation. At eastern elongation, the planet is visible in the west, in the rays of the evening dawn, shortly after sunset, and sets some time after it.

Then, moving backwards (i.e. from east to west, at first slowly, and then faster, the planet begins to approach the Sun, hides in its rays and ceases to be sawed. At this time, the lower connection of the planet with the Sun occurs; the planet passes between the Earth and the Sun. The ecliptic longitudes of the Sun and the planet are equal. Some time after the inferior conjunction, the planet becomes visible again, but now in the east, in the rays of the dawn, shortly before sunrise. At this time, it continues to move backward, gradually moving away from the Sun "Having slowed down the rate of retrogression and reached the greatest western elongation, the planet stops and changes its direction of motion to a direct one. Now it moves from west to east, at first slowly, then faster. Its distance from the Sun decreases, and finally it hides in the morning rays Sun At this time, the planet passes behind the Sun, the ecliptic longitudes of both luminaries are again equal - it comes from the top This is the conjunction of the planet with the Sun, after which, after some time, it is again visible in the west in the rays of the evening dawn. Continuing to move in a straight line, it gradually slows down its speed.

Having reached the maximum eastern distance, the planet stops, changes the direction of its movement to the reverse, and everything repeats from the beginning. Thus, the lower planets make, as it were, “oscillations” around the Sun, like a pendulum around its middle position.

The positions of the planets relative to the Sun described above are called planetary configurations.

7.2. Explanation of the configurations and apparent movements of the planets

During their movement in orbits, the planets can occupy various positions relative to the Sun and the Earth. Suppose that at some moment (Fig. 24) the Earth T occupies a certain position in its orbit relative to the Sun C. The lower or upper planet can be at this moment at any point in its orbit.

If the lower planet V is located in one of the four points V 1, V 2, V 3 or V 4 indicated on the drawing, then it is visible from the Earth in the lower (V 1) or upper (V 3) conjunction with the Sun, in the greatest western (V 2) or at greatest eastern (V 4) elongation. If the upper planet M is located at points M 1, M 2, M 3 or M 4 of its orbit, then it is visible from the Earth in opposition (M 1), in conjunction (M 3), in the western (M 2) or eastern ( M 4) quadrature.

The essence of explaining the forward and backward movements of the planets is to compare the orbital linear velocities of the planet and the Earth.

When the upper planet (Fig. 25) is near the conjunction (M 3), then its speed is directed in the direction opposite to the Earth's speed (T 3). From the Earth, the planet will appear to move in direct motion, i.e. in the direction of its actual movement, from right to left. In this case, its speed will seem increased. When the upper planet is near opposition (M 1), then its speed and the speed of the Earth are directed in the same direction. But the linear velocity of the Earth is greater than the linear velocity of the upper planet, and therefore, from the Earth, the planet will appear to be moving in the opposite direction, i.e. backwards, from left to right.

Similar reasoning explains why the lower planets (Mercury and Venus) near the lower conjunction (V 1) move backwards among the stars, and near the upper conjunction (V 3) - in direct motion (Fig. 26).

Send your good work in the knowledge base is simple. Use the form below

Students, graduate students, young scientists who use the knowledge base in their studies and work will be very grateful to you.

Hosted at http://www.allbest.ru/

Introduction

The starry sky has occupied the imagination of people at all times. Why do stars light up? How many of them shine at night? Are they far from us? Does the stellar universe have boundaries? Since ancient times, man has thought about these and many other questions, sought to understand and comprehend the structure of that big world in which we live.

The earliest ideas of people about him are preserved in fairy tales and legends. Centuries and millennia passed before the science of the Universe arose and received a deep substantiation and development, revealing to us a wonderful prostate, an amazing order of the universe. It was not for nothing that even in ancient Greece it was called Cosmos, and this word originally meant “order” and “beauty”.

Systems of the world are ideas about the location in space and the movement of the Earth, the Sun, the Moon, planets, stars and others. celestial bodies.

1. Picture of the world

In the ancient Indian book called "Rig Veda", which means "Book of Hymns", one can find a description - one of the very first in the history of mankind - of the entire Universe as a whole. According to the Rigveda, it is not too complicated. It contains, first of all, the Earth. It appears as a boundless flat surface - "vast space". This surface is covered from above by the sky. And the sky is a blue dome dotted with stars. Between heaven and earth - "luminous air".

It was very far from science. But something else is important here. Remarkable and grandiose is the daring goal itself - to embrace the whole Universe with thought. From here comes the confidence that the human mind is able to comprehend, understand, unravel its structure, create in its imagination a complete picture of the world.

2. Movement of the planets

By observing the annual movement of the Sun among the stars, ancient people learned to determine in advance the onset of a particular season. They divided the sky along the ecliptic into 12 constellations, in each of which the Sun is located for about a month. As already noted, these constellations were called zodiacal. All of them, with the exception of one, are named after animals.

Ancient people associated their agricultural work with the morning sunrise of one or another constellation, and this is reflected in the very names of the constellations. Thus, the appearance of the constellation Aquarius in the sky indicated the expected flood, the appearance of Pisces - the upcoming move of the fish for spawning. With the morning appearance of the constellation Virgo, the harvesting of bread began, which was carried out mainly by women. A month later, the neighboring constellation Libra appeared in the sky, at which time the weighing and counting of the crop was taking place.

As early as 2000 BC. e. Ancient observers noticed five special luminaries among the zodiac constellations, which, constantly changing their position in the sky, move from one zodiac constellation to another. Subsequently, Greek astronomers called these luminaries planets, that is, "wandering." These are Mercury, Venus, Mars, Jupiter and Saturn, which have retained the names of the ancient Roman gods in their names to this day. The Moon and the Sun were also counted among the wandering luminaries.

Probably, many centuries passed before the ancient astronomers managed to establish certain patterns in the motion of the planets and, above all, to establish the time intervals after which the position of the planet in the sky in relation to the Sun is repeated. This period of time was later called the synodic period of the planet's revolution. After that, it was possible to take the next step - to build a general model of the world, in which a certain place would be assigned to each of the planets and using which it would be possible to predict the position of the planet in advance for several months or years in advance.

According to the nature of their movement celestial sphere in relation to the Sun, the planets (in our understanding) are divided into two groups. Mercury and Venus are called internal or inferior, the rest are external or superior.

The angular velocity of the Sun is greater than the velocity of the direct motion of the upper planet. Therefore, the Sun gradually overtakes the planet. As for the inner planets, at the moment when the direction to the planet and to the Sun coincide, the conjunction of the planet with the Sun occurs. After the Sun overtakes the planet, it becomes visible before sunrise, in the second half of the night. The moment when the angle between the direction to the Sun and the direction to the planet is 180 degrees is called the opposition of the planet. At this time, it is in the middle of the arc of its backward movement. The removal of the planet from the Sun by 90 degrees to the east is called the eastern quadrature, and 90 degrees to the west is called the western quadrature. All positions of planets mentioned here concerning the Sun (from the point of view of the terrestrial observer) are called configurations.

During excavations of ancient cities and temples of Babylonia, tens of thousands of clay tablets with astronomical texts were found. Their decoding showed that the ancient Babylonian astronomers closely followed the position of the planets in the sky; they were able to determine their synodic circulation periods and use these data in their calculations.

3. The first models of the world

In spite of high level astronomical information of the peoples of the ancient East, their views on the structure of the world were limited to direct visual sensations. Therefore, in Babylon, there were views according to which the Earth looks like a convex island surrounded by an ocean. It is as if there is inside the Earth " realm of the dead". The sky is a solid dome resting on earth's surface and separating the "lower waters" (the ocean flowing around the earth's island) from the "upper" (rain) waters. Celestial bodies are attached to this dome, as if the gods live above the sky. The sun rises in the morning through the east gate and sets through the west gate, and at night it moves under the earth.

According to the ideas of the ancient Egyptians, the Universe looks like a large valley, elongated from north to south, in the center of which is Egypt. The sky was likened to a large iron roof, which is supported on pillars, on which stars are suspended in the form of lamps.

AT Ancient China there was an idea according to which the Earth has the shape of a flat rectangle, above which a round, convex sky is supported on pillars. The enraged dragon seemed to bend the central pillar, as a result of which the Earth leaned towards the east. Therefore, all rivers in China flow to the east. The sky tilted to the west, so all the heavenly bodies move from east to west.

And only in the Greek colonies on the western shores of Asia Minor (Ionia), in southern Italy and in Sicily in the fourth century BC, the rapid development of science, in particular, philosophy, as a doctrine of nature, began. It is here that simple contemplation of natural phenomena and their naive interpretation are replaced by attempts to scientifically explain these phenomena, to unravel their true causes.

One of the outstanding ancient Greek thinkers was Heraclitus of Ephesus (c. 530 - 470 BC). It is to him that the words belong: “The world, one of everything, was not created by any of the gods and by any of the people, but was, is and will be an ever-living fire, naturally igniting and naturally extinguishing ...” Then Pythagoras of Samos (c. 580 - 500 BC) expressed the idea that the Earth, like other celestial bodies, has the shape of a ball. The Universe was presented to Pythagoras in the form of concentric transparent crystal spheres embedded in each other, to which the planets were supposedly attached. In this model, the Earth was placed in the center of the world, the spheres of the Moon, Mercury, Venus, Sun, Mars, Jupiter and Saturn revolved around it. Farther away was the sphere fixed stars.

The first theory of the structure of the world, explaining the direct and backward movement of the planets, was created by the Greek philosopher Eudoxus of Cnidus (c. 408 - 355 BC). He suggested that each planet has not one but several spheres attached to each other. One of them makes one revolution per day around the axis of the celestial sphere in the direction from east to west. The time of revolution of the other (in the opposite direction) was assumed to be equal to the period of revolution of the planet. This explained the motion of the planet along the ecliptic. It was assumed that the axis of the second sphere is inclined to the axis of the first at a certain angle. The combination of two more spheres with these spheres made it possible to explain the backward movement in relation to the ecliptic. All features of the movement of the Sun and Moon were explained using three spheres. Eudoxus placed the stars on one sphere containing all the others. Thus, all the visible movement of the celestial bodies Eudoxus reduced to the rotation of 27 spheres.

It is appropriate to recall that the idea of ​​a uniform, circular, perfectly regular movement of celestial bodies was expressed by the philosopher Plato. He also suggested that the Earth is in the center of the world, that the Moon, the Sun revolve around it, then the morning star Venus, the star of Hermes, the stars of Ares, Zeus and Kronos. Plato first found the names of the planets by the name of the gods, which completely coincide with the Babylonian ones. Plato first formulated the task for mathematicians: to find with the help of what uniform and regular circular motions one can "save the phenomena represented by the planets." In other words, Plato set the task of constructing a geometric model of the world, in the center of which, of course, the Earth should have been.

Plato's disciple Aristotle (384 - 322 BC) took up the improvement of the system of the world of Eudoxus. Since the views of this outstanding philosopher - encyclopedist reigned supreme in physics and astronomy for almost two thousand years, I will dwell on them in more detail.

Aristotle, following the philosopher Empedocles (c. 490 - 430 BC), suggested the existence of four "elements": earth, water, air and fire, from the mixing of which all the bodies found on Earth allegedly originated. According to Aristotle, the elements water and earth naturally tend to move towards the center of the world ("down"), while fire and air move "up" to the periphery, and then the faster, the closer they are to their "natural" place. Therefore, in the center of the world is the Earth, above it are water, air and fire. According to Aristotle, the Universe is limited in space, although its movement is eternal, it has neither end nor beginning. This is possible just because, in addition to the four elements mentioned, there is also a fifth, indestructible matter, which Aristotle called ether. It is as if all celestial bodies consist of ether, for which perpetual circular motion is a natural state. The "zone of ether" begins near the moon and extends upward, while below the moon is the world of the four elements.

This is how Aristotle himself describes his understanding of the universe: “The sun and planets revolve around the Earth, which is motionless in the center of the world. Our fire, in relation to its color, has no resemblance to the light of the sun, dazzling whiteness. The sun is not made of fire; it is a huge accumulation of ether; The heat of the Sun is caused by its action on the ether during its revolution around the Earth. Comets are transient phenomena that are quickly born in the atmosphere and just as quickly disappear. The Milky Way is nothing but vapors ignited by the rapid rotation of the stars around the Earth... The movements of celestial bodies, generally speaking, occur much more regularly than the movements noticed on Earth; for, since celestial bodies are more perfect than any other bodies, the most regular movement, and at the same time the simplest, befits them, and such movement can only be circular, because in this case the movement is at the same time uniform. The heavenly bodies move freely like the gods, to whom they are closer than to the inhabitants of the Earth; therefore, the luminaries do not need rest during their movement, and the cause of their movement is contained in themselves. The higher regions of the sky, more perfect, containing fixed stars, therefore have the most perfect movement - always to the right. As for the part of the sky closest to the Earth, and therefore less perfect, this part serves as the seat of much less perfect luminaries, such as the planets. These latter move not only to the right, but also to the left, and, moreover, in orbits inclined to the orbits of the fixed stars. All heavy bodies tend to the center of the Earth, and since every body tends to the center of the Universe, therefore the Earth must also be motionless in this center.

When building his system of the world, Aristotle used the ideas of Eudoxus about the concentric spheres on which the planets are located and which revolve around the Earth. According to Aristotle, the root cause of this movement is the "first engine" - a special rotating sphere located behind the sphere of "fixed stars", which sets everything else in motion. According to this model, only one sphere in each of the planets rotates from east to west, the other three - in the opposite direction. Aristotle believed that the action of these three spheres should be compensated by an additional three inner spheres belonging to the same planet. It is in this case that only a daily rotation acts on each subsequent (towards the Earth) planet. Thus, in the system of the world of Aristotle, the movement of celestial bodies was described with the help of 55 hard crystal spherical shells.

Later, in this system of the world, eight concentric layers (heavens) were distinguished, which transmitted their movement to each other (Fig. 1). In each such layer, there were seven spheres moving this planet.

At the time of Aristotle, other views on the structure of the world were also expressed, in particular, that it is not the Sun that revolves around the Earth, but the Earth, together with other planets, revolves around the Sun. Against this, Aristotle put forward a serious argument: if the Earth moved in space, then this movement would lead to a regular apparent movement of the stars in the sky. As we know, this effect (annual parallactic shift of stars) was discovered only in the middle of the 19th century, 2150 years after Aristotle...

In his declining years, Aristotle was accused of godlessness and fled from Athens. In fact in his understanding of the world he vacillated between materialism and idealism. His idealistic views and, in particular, the idea of ​​the Earth as the center of the universe was adapted to protect religion. That is why, in the middle of the second millennium of our era, the struggle against the views of Aristotle became a necessary condition for the development of science...

4. First heliocentric system

Aristotle's contemporaries already knew that the planet Mars at opposition, as well as Venus during the backward movement, is much brighter than at other times. According to the theory of spheres, they should always remain at the same distance from the Earth. That is why then there were other ideas about the structure of the world.

So, Heraclitus of Pontus (388 - 315 BC) assumed that the Earth moves "... rotationally, around its axis, like a wheel, from west to east around its own center." He also expressed the idea that the orbits of Venus and Mercury are circles, in the center of which is the Sun. Together with the Sun, these planets seem to revolve around the Earth.

Even more bold views were held by Aristarchus of Samos (c. 310 - 230 BC). The outstanding ancient Greek scholar Archimedes (c. 287 - 212 BC), in his work "Psammit" ("Calculation of grains of sand"), referring to Gelon of Syracuse, wrote about the views of Aristarchus as follows:

“You know that, according to some astronomers, the world has the shape of a sphere, the center of which coincides with the center of the Earth, and the radius equal to length straight line connecting the centers of the Earth and the Sun. But Aristarchus of Samos, in his "Proposals" written against astronomers, rejecting this idea, comes to the conclusion that the world is much larger than just indicated. He believes that the fixed stars and the Sun do not change their place in space, that the Earth moves in a circle around the Sun, which is at its center, and that the center of the sphere of fixed stars coincides with the center of the Sun, and the size of this sphere is such that the circle described by his assumption, the Earth, is to the distance of the fixed stars in the same relation as the center of the ball is to its surface.

5. Ptolemaic system

The formation of astronomy as an exact science began thanks to the work of the outstanding Greek scientist Hipparchus. He was the first to start systematic astronomical observations and their comprehensive mathematical analysis, laid the foundations of spherical astronomy and trigonometry, developed the theory of the motion of the Sun and Moon and, on its basis, methods for predicting eclipses.

Hipparchus discovered that the apparent movement of the Sun and Moon in the sky is uneven. Therefore, he took the point of view that these luminaries move uniformly in circular orbits, but the center of the circle is displaced with respect to the center of the Earth. Such orbits were called eccentres. Hipparchus compiled tables by which it was possible to determine the position of the sun and moon in the sky on any day of the year. As for the planets, according to Ptolemy, he “did not make other attempts to explain the motion of the planets, but was content with putting in order the observations made before him, adding to them a much larger number of his own. He limited himself to pointing out to his contemporaries the unsatisfactoriness of all the hypotheses by which some astronomers thought to explain the movement of the heavenly bodies.

Thanks to the work of Hipparchus, astronomers abandoned the imaginary crystal spheres proposed by Eudoxus and moved on to more complex constructions using epicycles and deferents, proposed even before Hipparchus by Apollo of Perga. The classical form of the theory of epicyclic motions was given by Claudius Ptolemy.

The main work of Ptolemy "Mathematical Syntax in 13 Books" or, as the Arabs later called it, "Almagest" ("The Greatest") became famous in medieval Europe only in the 12th century. In 1515 it was printed on Latin translated from Arabic, and in 1528 translated from Greek. Three times "Almagest" was published on Greek, in 1912 it was published in German.

"Almagest" is a real encyclopedia of ancient astronomy. In this book, Ptolemy did what none of his predecessors could do. He developed a method by which it was possible to calculate the position of a particular planet at any predetermined point in time. This was not easy for him, and in one place he remarked:

“It seems easier to move the planets themselves than to comprehend their complex movement...”

By "setting" the Earth at the center of the world, Ptolemy presented the apparent complex and uneven motion of each planet as the sum of several simple, uniform circular motions.

According to Ptolemy, each planet moves uniformly in a small circle - an epicycle. The center of the epicycle, in turn, slides uniformly around the circumference of a large circle called the deferent. For a better agreement between the theory and observational data, it was necessary to assume that the center of the deferent is displaced with respect to the center of the Earth. But that wasn't enough. Ptolemy was forced to assume that the movement of the center of the epicycle along the deferent is uniform (i.e., its angular velocity of movement is constant), if we consider this movement not from the center of the deferent O and not from the center of the Earth T, but from some “leveling point” E, later called equant.

Combining observations with calculations, Ptolemy obtained by successive approximations that the ratios of the radii of epicycles to the radii of deferents for Mercury, Venus, Mars, Jupiter and Saturn are 0.376, 0.720, 0.658, 0.192 and 0.103, respectively. It is curious that in order to predict the position of the planet in the sky, it was not necessary to know the distances to the planet, but only the mentioned ratio of the radii of epicycles and deferents.

When constructing his geometric model of the world, Ptolemy took into account the fact that in the process of their movement the planets deviate somewhat from the ecliptic. Therefore, for Mars, Jupiter and Saturn, he "tilted" the planes of the deferents to the ecliptic and the planes of the epicycles to the planes of the deferents. For Mercury and Venus, he introduced up and down oscillations using small vertical circles. In general, to explain all the features noticed at that time in the motion of the planets, Ptolemy introduced 40 epicycles. The system of the world of Ptolemy, in the center of which is the Earth, is called geocentric.

In addition to the ratio of the radii of epicycles and deferents, in order to compare the theory with observations, it was necessary to set the periods of revolution along these circles. According to Ptolemy, all the upper planets make a complete revolution around the circumference of the epicycles in the same period of time as the Sun does along the ecliptic, that is, in a year. Therefore, the radii of the epicycles of these planets, directed towards the planets, are always parallel to the direction from the Earth to the Sun. In the lower planets - Mercury and Venus - the period of revolution along the epicycle is equal to the period of time, and during which the planet returns to its starting point in the sky. For periods of revolutions of the center of the epicycle along the circumference of the deferent, the picture is reversed. At Mercury and Venus they are equal to a year. Therefore, the centers of their epicycles always lie on the straight line connecting the sun and the Earth. For the outer planets, they are determined by the time during which the planet, having described a complete circle in the sky, returns to the same stars.

Following Aristotle, Ptolemy tried to refute the idea of ​​the possible motion of the Earth. He wrote:

“There are people who claim that nothing prevents us from assuming that the sky is motionless, and the earth rotates about its axis from west to east, and that it makes such a revolution every day. True, speaking of the luminaries, nothing prevents, for greater simplicity, from assuming this, if only visible movements are taken into account. But these people do not realize to what extent such an opinion is ridiculous, if you look closely at everything that happens around us and in the air. If we agree with them - which is not really the case - that the lightest bodies do not move at all, or move in the same way as heavy bodies, while, obviously, air bodies move with greater speed than earthly bodies; if we agreed with them that the densest and heaviest objects have their own movement, fast and constant, while in fact they move with difficulty from the shocks imparted to them, all the same, these people would have to admit that the Earth is due to of its rotation would have a movement much faster than all those that occur around it, because it would make such a large circle in such a small period of time. Thus, the bodies that would support the Earth would always seem to move in the opposite direction from it, and no cloud, nothing flying or thrown would ever seem to be heading east, for the Earth would outstrip any movement in this direction.

From a modern point of view, we can say that Ptolemy overestimated the role of centrifugal force too much. He also adhered to Aristotle's erroneous assertion that in a gravitational field bodies fall with velocities proportional to their masses...

In general, as A. Pannekoek noted, Ptolemy's "Mathematical Work" "was a carnival procession of geometry, a celebration of the deepest creation of the human mind in the representation of the Universe .. Ptolemy's work appears before us as great monument ancient sciences...

After the high flowering of ancient culture on the European continent, a period of stagnation and regression began. This gloomy period of time lasting more than a thousand years has been called the Middle Ages.

It was preceded by the transformation of Christianity into the dominant religion, in which there was no place for the highly developed science of ancient antiquity. At this time, there was a return to the most primitive ideas about a flat Earth.

And only since the XI century. under the influence of the growth of commercial relations, with an effort in the cities of a new class - the bourgeoisie. Spiritual life in Europe began to awaken. In the middle of the XIII century. the philosophy of Aristotle was adapted to Christian theology, the decisions of church councils that forbade the natural philosophical ideas of the great ancient Greek philosopher were canceled. Aristotle's views on the structure of the world soon became integral elements of the Christian faith. Now it was no longer possible to doubt that the Earth has the shape of a ball, installed in the center of the world, and that all the heavenly bodies revolve around it. The Ptolemaic system became, as it were, an addition to Aristotle, helping to carry out specific calculations of the positions of the planets.

Ptolemy determined the main parameters of his model of the world in the highest degree skillfully and with high accuracy. Over time, however, astronomers began to become convinced that there were discrepancies between the true position of the planet in the sky and the calculated one. So, at the beginning of the 12th century, the planet Mars was two degrees away from the place where it should have been according to the tables of Ptolemy.

To explain all the features of the motion of the planets in the sky, it was necessary to introduce for each of them up to ten or more epicycles with ever-decreasing radii so that the center of the smaller epicycle revolves around the circle of the larger one. By the 16th century, the movement of the Sun, Moon and five planets was explained using over 80 circles! And yet, observations separated by large intervals of time were difficult to “fit” into this pattern. It was necessary to introduce new epicycles, slightly change their radii, and shift the centers of the deferents with respect to the center of the Earth. In the end, the geocentric system of Ptolemy, overloaded with epicycles and equants, collapsed from its own weight...

6. World of Copernicus

The book of Copernicus, published in the year of his death, in 1543, had a modest title: "On the rotation of the celestial spheres." But it was a complete overthrow of Aristotle's view of the world. The complex mass of hollow transparent crystal spheres is a thing of the past. Since that time, a new era has begun in our understanding of the Universe. It continues to this day.

Thanks to Copernicus, we have learned that the Sun occupies its proper position in the center of the planetary system. The earth is not the center of the world, but one of the ordinary planets revolving around the sun. So everything fell into place. Structure solar system was finally figured out.

Further discoveries of astronomers added to the family of large planets. There are nine of them: Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto. In this order, they occupy their orbits around the Sun. Many small bodies of the solar system - asteroids and comets - have been discovered. But this did not change the new Copernican picture of the world. On the contrary, all these discoveries only confirm and refine it.

Now we understand that we live on a small planet that looks like a ball. The earth revolves around the sun in an orbit that is not too different from a circle. The radius of this circle is close to 150 million kilometers.

The distance from the Sun to Saturn - the farthest planet known at the time of Copernicus - is approximately ten times the radius of the earth's orbit. This distance was quite correctly determined by Copernicus. The size of the solar system - the distance from the Sun to the orbit of the ninth planet, Pluto, is still almost four times greater and is approximately 6 billion kilometers.

This is the picture of the universe in our immediate environment. This is the world according to Copernicus.

But the solar system is not the entire universe. We can say that this is just our little world. What about distant stars? About them Copernicus did not dare to express any definite opinion. He simply left them in the same place, not the far sphere where Aristotle had them, and only said, and quite rightly, that the distance to the stars is many times more sizes planetary orbits. Like ancient scientists, he represented the Universe as a closed space, limited by this sphere.

7. Sun and Stars

On a clear moonless night, when nothing interferes with observation, a person with sharp eyesight will see no more than two to three thousand twinkling dots in the sky. The list, compiled in the 2nd century BC by the famous ancient Greek astronomer Hipparchus and later supplemented by Ptolemy, contains 1022 stars. Hevelius, the last astronomer who made such calculations without the help of a telescope, brought their number to 1533.

But already in antiquity, the existence of a large number stars invisible to the eye. Democritus, the great scientist of antiquity, said that the whitish strip that stretches across the whole sky, which we call milky way, is in reality a combination of the light of a multitude of individually invisible stars. Structural controversy Milky Way continued for centuries. The decision - in favor of Democritus' conjecture - came in 1610, when Galileo reported the first discoveries made in the sky with a telescope. He wrote with understandable excitement and pride that he had now succeeded in “making available to the eye stars that had never before been visible and whose number was at least ten times more number stars known from ancient times.

But this great discovery still left the world of stars mysterious. Are all of them, visible and invisible, really concentrated in a thin spherical layer around the Sun?

Even before the discovery of Galileo, a completely unexpected, at that time remarkably bold idea was expressed. It belongs to Giordano Bruno, whose tragic fate is known to all. Bruno put forward the idea that our Sun is one of the stars of the Universe. Only one of the great many, and not the center of the entire universe. But then any other star could also have its own planetary system.

If Copernicus indicated the place of the Earth by no means in the center of the world, then Bruno and the Sun deprived of this privilege.

Bruno's idea gave rise to many striking consequences. From it followed an estimate of the distances to the stars. Indeed, the Sun is a star like the others, but only the closest to us. That's why it's so big and bright. And how far should the luminary be moved so that it looks like, for example, Sirius? The answer to this question was given by the Dutch astronomer Huygens (1629 - 1695). He compared the brightness of these two celestial bodies, and this is what turned out: Sirius is hundreds of times farther from us than the Sun.

To better imagine how great the distance to a star is, let's say that a beam of light flying 300,000 kilometers in one second takes several years to travel from Sirius to us. Astronomers speak in this case of a distance of several light years. According to modern updated data, the distance to Sirius is 8.7 light years. And the distance from us to the sun is only 8 light minutes.

Of course, different stars differ from each other (this is taken into account in the modern estimate of the distance to Sirius). Therefore, determining the distances to them even now often remains a very difficult, and sometimes simply unsolvable task for astronomers, although since the time of Huygens many new methods have been invented for this.

Conclusion

We know the structure of the universe in a vast volume of space, which light takes billions of years to cross. But the inquisitive thought of man strives to penetrate further. What lies beyond the observable region of the world? Is the universe infinite in volume? And its expansion - why did it start and will it always continue in the future? And what is the origin of the "hidden" mass? And finally, how did intelligent life originate in the universe?

Does it exist anywhere else besides our planet? There are no definitive and complete answers to these questions yet.

The universe is inexhaustible. The thirst for knowledge is also tireless, forcing people to ask more and more new questions about the world and persistently seek answers to them.

sun moon planet star

Bibliography

1. Space: Collection. “Popular science literature” (Compiled by Yu. I. Koptev and S. A. Nikitin; Introductory senior academician Yu. A. Osipyan; Design and layout by V. Italiantsev; Drawings by E. Azanov, N. Kotlyarovsky, V. Tsikoty. - L .: Det. lit., 1987. - 223 p., ill.)

2. I. A. Klimishin. “Astronomy of our days” - M .: “Nauka”, 1976. - 453 p.

3. A. N. Tomilin. “Sky Earth. Essays on the history of astronomy ”(Scientific editor and author of the foreword, Doctor of Physical and Mathematical Sciences K. F. Ogorodnikov. Drawings by T. Obolenskaya and B. Starodubtsev. L., “Det. Lit.”, 1974. - 334 p., ill. .)

4. “Encyclopedic Dictionary of a Young Astronomer” (Compiled by N. P. Erpylev. - 2nd ed., Revised and added. - M .: Pedagogy, 1986. - 336 p., ill.

Featured on Allbest.ur

Similar Documents

Picture of the world. The movement of the planets. The first models of the world and the heliocentric system. The system of the world is ideas about the position in space and the movement of the Earth, Sun, Moon, planets and stars. The system of Ptolemy and Copernicus. Galaxy. star worlds. Universe.

abstract, added 07/02/2008


Systems of the world are ideas about the location in space and the movement of the Earth, the Sun, the Moon, planets, stars and other celestial bodies. Since ancient Greece, the universe has been called cosmos, and this word originally meant "order" and "beauty" of the universe.

abstract, added 06/13/2008


Analysis of the work of Copernicus "On the Revolution of the Celestial Spheres". Provisions on the sphericity of the world and the Earth, the rotation of the planets around the axis and their circulation around the Sun. Calculation of the apparent positions of stars, planets and the Sun in the firmament, the actual movement of the planets.

abstract, added 11/11/2010


Space travel in astronomy class. Nature of the Universe, evolution and motion of celestial bodies. Discovery and exploration of the planets. Nicolaus Copernicus, Giordano Bruno, Galileo Galilei on the structure of the solar system. The movement of the sun and planets in the celestial sphere.

creative work, added 05/26/2015


Picture of the world, the movement of the planets. The first models of the world, the first heliocentric system, the systems of Ptolemy and Copernicus. Sun and stars, Galaxy, star worlds, Universe. What lies beyond the boundaries of the observable region of the world, how life originated in the Universe.

abstract, added 11/03/2009


Picture of the world. The movement of the planets. The first models of the world. The first heliocentric system. Ptolemaic system. World of Copernicus. Sun and Stars. Galaxy. star worlds. Universe. Is there life anywhere else besides our planet?

abstract, added 03/06/2007


The origin of the theory of the movement of the sun and planets in Ancient Greece. First scientific knowledge in the field of astronomy. Heliocentric system in the version of N. Copernicus, characteristic of the work "On the rotations of the celestial spheres". Significance of heliocentrism in the history of science.

test, added 05/18/2009


Picture of the world. The movement of the planets. The first models of the world. The first heliocentric system. Ptolemy system. World of Copernicus. Sun and stars. Galaxy. star worlds. Universe.

abstract, added 06/13/2007


The formation of the solar system. theories of the past. Birth of the Sun. Origin of the planets. Discovery of other planetary systems. Planets and their satellites. The structure of the planets. Planet Earth. The shape, size and movement of the Earth. Internal structure.

abstract, added 06.10.2006


Plotting the distribution of officially known planets. Determining the exact distances to Pluto and the beyond-Pluto planets. The formula for calculating the rate of shrinkage of the Sun. The origin of the planets of the solar system: Earth, Mars, Venus, Mercury and Vulcan.

For the gravitational field created by a massive body, one can formulate a theorem that is similar to Newton's theorem on the field of a spherically symmetric body.

This theorem bears the name of Birkhoff. essence Birkhoff's theorems consists of the following. Let us assume that the gravitational field is created by a system of bodies that move in a limited space. Then if the mass distribution in such a system is spherically symmetric, and the velocities are all directed along radii and also do not depend on angles, the field of such a system does not depend on time and coincides (outside the system) with zero material point, which has a mass equal to the mass of the system.

Consequently, the observer cannot conclude anything about the distribution of masses and velocities within such a system if he confines himself only to measuring the force of gravity. Therefore, considering the problem of the field of the Sun, we can use the solution of the problem of the field of a point mass. The conditions of the theorem are violated if the field source rotates. In this case, the system loses spherical symmetry and remains with axial symmetry. For the Sun, this effect is small. There is a project to study the interaction of the field of a rotating Earth with a rotating gyroscope. This effect is very similar to the interaction of two magnetic moments, each of which is created by the movement electric charges. However experimental studies gravitational fields of rotating bodies are very difficult.

But we will see that in black holes the rotating fields turn out to be quite significant.

First of all, we can estimate the magnitude of the corrections that the theory of gravitation makes to the classical laws of planetary motion.

Newton did not know that the speed could not be greater than the speed of light. Let's see when the speed of the planet reaches the speed of light, if we count according to the formula of Newtonian mechanics. Kepler's third law in Newtonian mechanics can be written as follows:

ω 2 R 3 = γM c

where ω is the frequency of the planet's revolution (2π/ω is the period); R is the average distance of the planet from the Sun; γ is the gravitational constant and M c is the mass of the Sun. Replacing ω for a circular orbit with υ/R, where υ is the linear velocity, we get:

The speed of the planet reaches the speed of light at a distance from the Sun R ≈ γM c / s 2 . This is an estimate of the distance from the Sun at which the effects of general relativity will be very large. In fact, we simply calculated the radius at which the first cosmic velocity (speed in a circular orbit) will be equal (according to Newtonian mechanics) to the speed of light. It can be equated to the second space velocity- so did Laplace back in 1796 - and get R c = 2γM c: c 2 . This value plays an important role in the theory of relativity and has a special name - the gravitational radius of the Sun. It is designated R gr s and is approximately 3 km. A similar value for the Earth is Rgrz ≈ 7 mm.

Laplace derived his formula from the equality potential energy body on a star, γmM/r, and its kinetic energy calculated by the usual classical formula mυ 2 /2. If we equate these two quantities, then they can be reduced by m. Since Laplace believed that light consists of corpuscles, he substituted the speed of light into the formula and came to the conclusion, which he stated in 1798 in the second volume of his work "Exposition of the System of the World": "A luminous star with the same density, that the earth, which is two hundred and fifty times the diameter of the sun, will not allow any of its rays to reach us; it is possible that the largest of the luminous bodies for this reason remain invisible.

Laplace's argument is, of course, wrong, but the formula for the gravitational radius remains the same in general relativity.

Laplace made one of the most amazing predictions: he realized that "black holes" could exist. Let's check the Laplace numbers again. It can be seen from the formula for the gravitational radius that R r p grows in proportion to the body mass. Laplace considered a star with a density equal to that of the Earth, and in this case the masses of stars are related as cubes of their radii. Then the radius of the black hole R d can be expressed in terms of the radius of the Earth:

where R s is the radius of the Earth, and R gr s is its gravitational radius.

which exceeds the radius of the Sun by about 250 times.

For the Sun, distances of the order of its gravitational radius lie near its center.

In our planetary system, the orbit of Mercury, the planet closest to the Sun, lies at a distance of about 60 million km. The magnitude of the correction to the motion of Mercury should be in order of magnitude equal to the ratio of the gravitational radius of the Sun to the distance to Mercury. This value is of the order of √5∙10 -6 .

Corrections to the motion of Mercury will be of two types - by changing the mass of the planet with speed and by changing the law of gravity.

The speed of Mercury, according to the same third Kepler's law, is greater than the speed of the Earth (30 km / s) to the root of the ratio of their distance, ~ 1.7, i.e., it is about 50 km / s, or 1/6000 of the speed of light. The corrections are usually determined by the square of the ratio υ 2 /c 2 , and therefore have the order of 1/36∙10 -6 . In the law of gravity, apart from the usual term 1/r 2 ; the term 1/r 3 appears; which leads to a correction of the same order.

The latest astronomical measurements of the motion of Mercury agree with the predictions of the theory with an error of no more than 2%.

Some time ago, the comparison of theory with experience was called into question when Dicks noted that the conclusion could be greatly affected if the Sun was even slightly flattened. So, if it is flattened only by 10 -4 (1 + 10 -4 is the ratio of the lengths of the ellipsoid axes, if the Sun is an ellipsoid). This will change the theoretical number by 7″ in 100 years. Apparently, more accurate observations will rule out even such a small oblateness.

In any case, now the picture of the movement of Mercury looks like this:

If there were no other planets and the movement would take place according to Newton's laws, then Mercury would describe an ellipse. The effects associated with the theory of relativity would lead to a perihelion shift of 41″ in 100 years. In fact, the total displacement is 575″ per 100 years due to interactions with other planets (Venus accounts for half of the effect). But Newton's mechanics explains only 534″ - the rest is left to the mechanics of the theory of relativity.

Recall that the changes in the motion of Mercury are relatively small due to the fact that Mercury is always far from the Sun. At distances of the order of one to three gravitational radii (3 km for the Sun), the corrections to the law of gravity would be so large that the compensation of the centrifugal force by the force of attraction to the Sun would be violated and the planet would fall into the Sun.

For the Sun, whose size is many times greater than its gravitational radius, such a region simply does not exist. However, for black holes, all this looks very serious. But more on that later.

If you find an error, please highlight a piece of text and click Ctrl+Enter.

Against the background of fixed stars, one can trace the constant movement of luminaries of a completely different nature - planets that move around the Sun. In the night sky, 7 celestial bodies are clearly visible, constantly changing their position. These include the Sun, Moon, Mercury, Venus, Mars, Jupiter and Saturn. The method for determining the position of the Sun relative to the stars was developed in ancient times; for this, a regular study of the starry sky was organized at dawn or immediately after sunset. Thanks to close observations, it was found that the Sun changes its position in the starry sky daily, shifting 1 degree to the east. Such a phenomenon is observed for 365 days, after which it returns to its previous position relative to the location of the stars. According to the results of such studies, the trajectory of the motion of the Sun relative to the stars was established.

Characteristic features of the motion of the planets in the solar system

During its constant movement, the Sun passes through 12 notorious constellations for 1 year: Aries, Taurus, Gemini, Cancer, etc. The belt along the ecliptic (the width is about 16 degrees), in which these constellations are located, is commonly called the zodiac. On the days of the summer and winter equinoxes, the Sun moves to the celestial equator, after which it begins to slowly move away from it. The largest deviation in 2 directions is approximately 23.5 degrees, these are the days of the summer and winter solstices. According to the ancient Greeks, it was found that the speed of the Sun along the ecliptic is slightly faster in winter than in summer. The rest of the planets are also characterized by a daily movement towards the west and a slight movement towards the east.
As for the Moon, it moves to the east a little faster than the Sun, its trajectory is characterized by a slight randomness. Its movement along one sign of the zodiac occurs within 27 and 1/3 days (moving occurs from east to west). The sidereal period of revolution is usually called the time period during which the moon passes along one sign of the zodiac. Its error can be 7 hours. Moon's trajectory certain period time completely coincides with the ecliptic, after which it begins to move away from it. This situation continues until a maximum deviation of 5 degrees is reached. After that, the Moon again approaches the ecliptic and begins to deviate from it by a similar angle, but only in the opposite direction.

The periods of revolution of the planets and the degree of their distance from the Sun

Depending on the characteristic features the movements of the planets in the celestial sphere, they are usually divided into 2 groups: lower and upper. The first group includes Mercury and Venus, and the second - all the other planets (with the exception of the Earth). The lower planets during their movements are characterized by a phase change (like the Moon). In the upper planets, this phenomenon is not observed, they constantly turn to the Earth with the illuminated side. During movement in the celestial sphere, the lower planets are not characterized by a significant distance far from the Sun (Mercury - no more than 28 degrees, and Venus - no further than 48 degrees). The location of the planet at the greatest angular distance to the east of the Sun is called the eastern (evening) elongation, and to the west - the western (morning) elongation.
Such large planets as Mercury, Venus, Mars, Jupiter and Saturn can even be seen with the naked eye in the starry sky, they look like large and bright dots. The average sidereal period of revolution for Mercury and Venus is 1 year each, for Mars it is 687 days. Jupiter makes a complete revolution along one zodiac sign in 12 years, and Saturn in 29.5 years. In fact, the time interval of the revolution of these planets may differ slightly.

We list the average values ​​of the arcs of backward movements:
- Mercury - 12 degrees, Venus - 16 degrees;
- Mars - 15 degrees, Jupiter - 10 degrees;
- Saturn - 7 degrees, Uranus - 4 degrees;
- Neptune - 3 degrees, Pluto - 2 degrees.

The location of the planets 90 degrees east of the Sun is commonly called the eastern quadrature, and 90 degrees west, respectively, the western quadrature. The movement of planets from west to east is called direct (proper) motion, the speed of which is constantly changing. It should be noted that the movement to the east periodically stops, and they begin to move in the opposite (western) direction. In this case, the trajectories can form loops, after which the direct movement resumes. It was found that the brightness of the planets increases during the movement.
Mercury retrogrades every 116 days, Mars every 780 days, Jupiter every 399 days, and Saturn every 378 days. Mercury and Venus do not tend to move away from the Sun at a decent angular distance, which cannot be said about Mars, Jupiter and Saturn. In the process of studying the movement of the planets, it was quite difficult for scientists to associate with the movement of stars. Therefore, the list of established relationships can be considered successive attempts to overcome the identified discrepancies.

The configurations of the planets are called characteristic mutual arrangements planets of the Earth and the Sun.

All planets relative to the Earth are divided into internal(whose orbits are located inside the earth's orbit) and external. To inner planets include Venus and Mercury, external- other. The inner planets are characterized by a conjunction configuration.

A conjunction is such a position of the planets when the inner planet is either between the Earth
and the Sun, or behind the Sun. In such cases, it is invisible. The position of the planet between the Earth and the Sun is called inferior conjunction; in it the planet is closest to the Earth. The presence of a planet behind the Sun is called an upper conjunction, and the planet
farthest from the earth.

The inner planets do not depart from the Sun at large angles (the maximum angle for Mercury is 28°, for Venus - 48°). The greatest deviations of the planets from the Sun to the west are called the greatest western elongation, to the east - the greatest eastern elongation.

For the outer planets is also possible connection configuration(position "behind the sun"). At the same time, they are invisible to an observer from the Earth, since they are lost in the rays of the Sun. The position of the outer planets on the Earth-Sun line is called opposition. This is the most convenient configuration for observing the planet.

Periods of the planets

The synodic period of the planet called the time interval between repetitions of its identical configurations.

The speed of the planets is greater, the closer they are to the Sun. Therefore, after the confrontation, the Earth will overtake those planets that are farther from the Sun. Over time, opposition will occur again as the Earth overtakes the planet by a full circle.

We can say that the synodic period of the outer planet is the period of time after which the Earth overtakes the planet by 360 ° in their movement around the Sun.

The sidereal period is the time after which, for an observer located on the Sun, the planet returns to the same star.

Between synodic ( S, in days) and sidereal ( T, in days) for months there is a ratio. For planets between the Sun and Earth:

Kepler's laws

Johannes Kepler (1571-1630) discovered his laws by studying the periodic revolution of Mars around the Sun.

Kepler's First Law: Each planet revolves in an ellipse with the Sun at one of its foci. The point of the orbit closest to the Sun is called perihelion, and the point farthest from it is called aphelion. The degree of elongation of an ellipse is characterized by its eccentricity.

Kepler's second law (law of areas): the radius vector of a planet describes equal areas in equal periods of time. If we consider the motion of the planet, then the arcs described by the planet for the same time intervals in different places of the orbit are different, although they limit equal areas. Consequently, the linear speed of the planet is not the same in different points her orbits. The speed of the planet when moving it in orbit is the greater, the closer it is to the Sun. At perihelion, the speed of the planet is greatest.

Thus, Kepler's second law quantitatively determines the change in the speed of a planet moving along an ellipse.

Kepler's third law: the squares of the sidereal periods of the planets are related as the cubes of the semi-major axes of their orbits. If the semi-major axis of the orbit and the sidereal period of revolution of one planet are denoted respectively by a 1, T1, and another planet - through a 2, T2, then the formula of the third law will be as follows:

Kepler's third law relates the lengths of the semi-major axes of planetary orbits to the length of the semi-major axis of the earth's orbit. In astronomy, this length is taken as the basic unit for measuring distances - the astronomical unit (AU).