home · Tool · Geocentric and heliocentric systems of the world: essence, meaning and differences. Geocentric and heliocentric systems of the world: comparison

Geocentric and heliocentric systems of the world: essence, meaning and differences. Geocentric and heliocentric systems of the world: comparison

The geocentric system of the world (from ancient Greek Γῆ, Γαῖα - Earth) is an idea of ​​​​the structure of the universe, according to which the central position in the Universe is occupied by the stationary Earth, around which the Sun, Moon, planets and stars revolve. An alternative to geocentrism is the heliocentric system of the world.

Development of geocentrism

Since ancient times, the Earth was considered the center of the universe. In this case, the presence of a central axis of the Universe and “top-bottom” asymmetry were assumed. The earth was kept from falling by some kind of support, which in early civilizations was thought to be some kind of giant mythical animal or animals (turtles, elephants, whales). The first ancient Greek philosopher Thales of Miletus saw a natural object - the world ocean - as this support. Anaximander of Miletus suggested that the Universe is centrally symmetric and does not have any distinguished direction. Therefore, the Earth, located in the center of the Cosmos, has no reason to move in any direction, that is, it rests freely in the center of the Universe without support. Anaximander's student Anaximenes did not follow his teacher, believing that the Earth was kept from falling by compressed air. Anaxagoras was of the same opinion. Anaximander's point of view was, however, shared by the Pythagoreans, Parmenides and Ptolemy. The position of Democritus is not clear: according to various evidence, he followed Anaximander or Anaximenes.

One of the earliest images of the geocentric system that have come down to us (Macrobius, Commentary on the Dream of Scipio, 9th century manuscript)

Anaximander considered the Earth to be in the shape of a low cylinder with a height three times less than the diameter of the base. Anaximenes, Anaxagoras, Leucippus believed that the Earth was flat, like a table top. A fundamentally new step was taken by Pythagoras, who suggested that the Earth has the shape of a ball. In this he was followed not only by the Pythagoreans, but also by Parmenides, Plato, and Aristotle. This is how the canonical form of the geocentric system arose, subsequently actively developed by ancient Greek astronomers: the spherical Earth is located in the center of the spherical Universe; The visible daily movement of the celestial bodies is a reflection of the rotation of the Cosmos around the world axis.

Medieval depiction of the geocentric system (from the Cosmography of Peter Apian, 1540)

As for the order of the luminaries, Anaximander considered the stars located closest to the Earth, followed by the Moon and the Sun. Anaximenes was the first to suggest that stars are the objects farthest from Earth, fixed on the outer shell of the Cosmos. In this, all subsequent scientists followed him (with the exception of Empedocles, who supported Anaximander). An opinion arose (for the first time, probably, among Anaximenes or the Pythagoreans) that the longer the period of revolution of a luminary in the celestial sphere, the higher it is. Thus, the order of the luminaries was as follows: Moon, Sun, Mars, Jupiter, Saturn, stars. Mercury and Venus are not included here because the Greeks had disagreements about them: Aristotle and Plato placed them immediately behind the Sun, Ptolemy - between the Moon and the Sun. Aristotle believed that there was nothing above the sphere of the fixed stars, not even space, while the Stoics believed that our world is immersed in endless empty space; atomists, following Democritus, believed that beyond our world (limited by the sphere of fixed stars) there are other worlds. This opinion was supported by the Epicureans; it was vividly expounded by Lucretius in his poem “On the Nature of Things.”


"Figure of the Celestial Bodies" is an illustration of Ptolemy's geocentric system of the world, made by Portuguese cartographer Bartolomeu Velho in 1568.

Stored in the National Library of France.

Justification for geocentrism

Ancient Greek scientists, however, substantiated the central position and immobility of the Earth in different ways. Anaximander, as already indicated, pointed out the spherical symmetry of the Cosmos as the reason. Aristotle did not support him, putting forward a counter-argument, later attributed to Buridan: in this case, a person located in the center of a room in which there is food near the walls should die of hunger (see Buridan's donkey). Aristotle himself justified geocentrism as follows: The Earth is a heavy body, and the natural place for heavy bodies is the center of the Universe; as experience shows, all heavy bodies fall vertically, and since they move towards the center of the world, the Earth is in the center. In addition, Aristotle rejected the orbital motion of the Earth (which was assumed by the Pythagorean Philolaus) on the grounds that it should lead to a parallactic displacement of stars, which is not observed.

Drawing of the geocentric system of the world from an Icelandic manuscript dated around 1750

A number of authors provide other empirical arguments. Pliny the Elder, in his encyclopedia Natural History, justifies the central position of the Earth by the equality of day and night during the equinoxes and the fact that during the equinox, rising and setting are observed on the same line, and the sunrise on the day of the summer solstice is on the same line , which is the same as sunset on the day of the winter solstice. From an astronomical point of view, all these arguments are, of course, a misunderstanding. Little better are the arguments given by Cleomedes in the textbook “Lectures on Astronomy”, where he proves the centrality of the Earth by contradiction. In his opinion, if the Earth were east of the center of the Universe, then the shadows at dawn would be shorter than at sunset, the celestial bodies at sunrise would appear larger than at sunset, and the duration from dawn to noon would be shorter than from noon until sunset. Since all this is not observed, the Earth cannot be shifted to the west from the center of the world. Similarly, it is proved that the Earth cannot be shifted to the west. Further, if the Earth were located north or south of the center, the shadows at sunrise would extend in a north or south direction, respectively. Moreover, at dawn on the days of the equinoxes, the shadows are directed exactly in the direction of sunset on these days, and at sunrise on the day of the summer solstice, the shadows point to the point of sunset on the day of the winter solstice. This also indicates that the Earth is not offset north or south of center. If the Earth were above the center, then less than half of the sky could be observed, including less than six signs of the zodiac; as a consequence, the night would always be longer than the day. It is similarly proven that the Earth cannot be located below the center of the world. Thus, it can only be in the center. Ptolemy gives approximately the same arguments in favor of the centrality of the Earth in the Almagest, Book I. Of course, the arguments of Cleomedes and Ptolemy only prove that the Universe is much larger than the Earth, and therefore are also untenable.


Pages from SACROBOSCO "Tractatus de Sphaera" with the Ptolemaic system - 1550

Ptolemy also tries to justify the immobility of the Earth (Almagest, book I). Firstly, if the Earth were displaced from the center, then the effects just described would be observed, but since they are not, the Earth is always in the center. Another argument is the verticality of the trajectories of falling bodies. Ptolemy justifies the absence of axial rotation of the Earth as follows: if the Earth rotated, then “... all objects that do not rest on the Earth should seem to make the same movement in the opposite direction; neither clouds nor other flying or hovering objects will ever be seen to move eastward, since the eastward movement of the earth will always throw them off, so that these objects will appear to move westward, in the opposite direction.” The inconsistency of this argument became clear only after the discovery of the foundations of mechanics.

Explanation of astronomical phenomena from the position of geocentrism

The greatest difficulty for ancient Greek astronomy was the uneven movement of the celestial bodies (especially the retrograde movements of the planets), since in the Pythagorean-Platonic tradition (which Aristotle largely followed), they were considered deities who should only make uniform movements. To overcome this difficulty, models were created in which the complex apparent movements of the planets were explained as the result of the addition of several uniform circular movements. The concrete embodiment of this principle was the theory of homocentric spheres of Eudoxus-Callippus, supported by Aristotle, and the theory of epicycles of Apollonius of Perga, Hipparchus and Ptolemy. However, the latter was forced to partially abandon the principle of uniform motion, introducing the equant model.

Refusal of geocentrism

During the scientific revolution of the 17th century, it became clear that geocentrism is incompatible with astronomical facts and contradicts physical theory; The heliocentric system of the world gradually established itself. The main events that led to the abandonment of the geocentric system were the creation of the heliocentric theory of planetary motions by Copernicus, the telescopic discoveries of Galileo, the discovery of Kepler's laws and, most importantly, the creation of classical mechanics and the discovery of the law of universal gravitation by Newton.

Geocentrism and religion

Already one of the first ideas opposed to geocentrism (the heliocentric hypothesis of Aristarchus of Samos) led to a reaction from representatives of religious philosophy: the Stoic Cleanthes called for bringing Aristarchus to trial for moving the “Hearth of the World”, meaning the Earth; it is unknown, however, whether Cleanthes’ efforts were crowned with success. In the Middle Ages, since the Christian church taught that the whole world was created by God for the sake of man (see Anthropocentrism), geocentrism was also successfully adapted to Christianity. This was also facilitated by a literal reading of the Bible. The scientific revolution of the 17th century was accompanied by attempts to administratively ban the heliocentric system, which led, in particular, to the trial of the supporter and promoter of heliocentrism Galileo Galilei. Currently, geocentrism as a religious belief is found among some conservative Protestant groups in the United States.

It is well known that in Ancient Greece (and Rome) the geocentric system of the world prevailed. In the descriptions of different philosophers it differs in detail. The most famous is the system of Aristotle, who apparently generalized the data known before him. Ptolemy also used this system (adding it with trims and epicycles). In this form, it was accepted by the Christian Church and medieval science and had a significant influence on the entire European culture. Figure 1 shows a diagram of Aristotle's geocentric system. Below we give its description according to A. Pannekoek.

Fig.1. Geocentric system of Aristotle-Ptolemy

“In the system of Aristotle, who united physics and astronomy into one harmonious system of the universe, all heavy elements tend to the center of the world and accumulate around it, forming a spherical mass of the Earth; lighter elements (water, air, fire) are collected in layers successively located one above the other. The word "down" means to the center of the world, the word "up" - to the surrounding celestial sphere. In addition to the four earthly elements, there is a fifth - perfect ether, from which the heavenly bodies are composed. Where the earth's elements end, there, according to Aristotle, is the orbit of the Moon. The planets and the Sun rotate behind the orbit of the Moon. The sphere of the Sun rotates throughout the year, the spheres of the planets each have their own rotation period. The celestial sphere, carrying the stars, rotates around the axis of the world per day. It carries with it all the internal spheres, and this explains the daily setting and rising of all the luminaries.”

I have always been surprised by the naivety and at the same time complexity of this system, reminiscent of the gears of a clock mechanism. The rotation of the firmament can be considered an observational fact, and the explanation for the daily movement of the luminaries seems quite natural. But to represent the annual movement of the Sun and the angular movement of the planets, it was necessary to introduce additional spheres - each luminary had its own sphere, and it was also necessary to link them all with the rotation of the sphere of the fixed stars (not to mention the trims and epicycles that appeared later). Apparently, some ancient philosophers felt this artificiality. Thus, Heraclides of Pontus explained the daily movement of the luminaries by the rotation of the Earth around its axis; Venus and Mercury in his system revolved around the Sun, but he still placed the Earth at the center of the universe. But Aristarchus of Samos, whom F. Engels rightly called the Copernicus of the Ancient World, taught that the Sun is in the center of the universe, and the Earth and planets revolve around it.

This means that the heliocentric system was already known in ancient times, but it was not widely used. As H. P. Blavatsky notes in “Isis Unveiled,” the heliocentric system, as well as the sphericity of the Earth, was known to the Egyptians from time immemorial.

INTRODUCTION

Claudius Ptolemy is a famous Alexandrian astronomer, mathematician and geographer of the 2nd century AD, one of the greatest scientists of antiquity. For a whole millennium, no one could compare with Ptolemy in the field of astronomy. There are no surviving references to his life and activities among historians of this period. Also, even the approximate dates of Ptolemy’s birth and death remained unknown, as well as any facts of his biography.

But thanks to his works, he remained in history. To the great fortune of modern historians, almost all of his major works have survived. Ptolemy's main work, the Almagest, was the main textbook on astronomy until the beginning of the 17th century.

In the Almagest, Ptolemy extensively applies the results of observations of his great predecessor Hipparchus (2nd century BC). Hipparchus followed and observed celestial bodies and sought to discover the patterns of planetary motion, since they represented a great mystery to astronomers of that time. The planets seemed to be describing loops as they moved across the sky. This difficulty is associated with the movement of the Earth itself. When the Earth seems to be “catching up” with another planet, then at first glance it may seem that the planet seems to pause and then move back. However, ancient astronomers thought that the planets actually make such complex movements around the Earth and based their theories on this.

Chapter I. Geocentric system of the world of Ptolemy

1.1.Development of geocentrism

Since ancient times, the Earth was considered the center of the universe. At the same time, the existence of a central axis of the Universe and a “top-bottom” asymmetry were assumed. Some kind of support saved the earth from falling. In early civilizations, a huge mythical animal or animals (elephants, whales, turtles) acted as a support. The first ancient Greek thinker and philosopher Thales of Miletus imagined a natural object - the world ocean - as this support. Anaximander of Miletus admitted the idea that the Universe is centrally symmetrical and does not have any specific direction. For this reason, the Earth, located in the center of the Cosmos, has no reason to move in any direction, that is, it directly rests freely in the center of the Universe without support. Anaximander's student Anaximenes did not agree with his teacher's theory, believing that compressed air kept the Earth from falling. Anaxagoras also adhered to this point of view. Anaximander's position was, however, shared by the Pythagoreans, Parmenides and Ptolemy. The position of Democritus was not clear: according to various evidence, he followed Anaximander or Anaximenes.



Anaximander assumed that the Earth has the shape of a low cylinder with a height three times less than the diameter of the base. Anaximenes, Anaxagoras, Leucippus assumed that the Earth was flat, something like a table top. A completely new step was taken by Pythagoras, who assumed that the Earth has the shape of a ball. In this assumption, he was followed not only by the Pythagoreans, but also by Plato, Parmenides, and Aristotle. This is how the canonical form of the geocentric system appeared, which was subsequently developed by ancient Greek astronomers: a spherical Earth at the center of the spherical Universe; The visible daily movement of the celestial bodies is a reflection of the rotation of the Cosmos around the world axis.

Anaximander believed that the stars were closest to the Earth, followed by the Moon and the Sun. Anaximenes was the first to suggest that stars are the objects farthest from the Earth, which are fixed on the outer shell of the Cosmos. In this, all subsequent scientists followed him (Exception: Empedocles; he adhered to the theory of Anaximander). A judgment appeared (for the first time, most likely, among Anaximenes or the Pythagoreans) that the longer the period of revolution of a star in the celestial sphere, the higher it is and, therefore, further away. Thus, the order of the luminaries was as follows: Moon, Sun, Mars, Jupiter, Saturn and then the stars. This list does not include Mercury and Venus, since the Greeks had disputes about them: Aristotle and Plato placed them immediately behind the Sun, Ptolemy - between the Moon and the Sun. Aristotle believed that there was nothing above the sphere of the fixed stars, including space, while the Stoics believed that our world is immersed in endless empty space; following the judgments of Democritus, they assumed that beyond our world (which is limited by the sphere of fixed stars) there are other worlds. This opinion was supported by the Epicureans, and was also vividly expressed by Lucretius in the poem “On the Nature of Things.”



1.2. Justification for geocentrism

Ancient Greek scientists had different opinions, justifying the central location and immobility of the Earth. Anaximander pointed out the spherical symmetry of the Cosmos as the reason. He was not supported by Aristotle, who put forward a counter-argument: in this case, a person located in the center of the room, near the walls of which there is food, should die of hunger. This argument was later attributed to Buridan. Aristotle himself directly substantiated geocentrism as follows: The Earth is a heavy body, and the natural place for heavy bodies is the center of the Universe; and, as experience shows, all heavy bodies fall vertically, and since they move towards the center of the world, the Earth is in the center. In addition, Aristotle denied the orbital motion of the Earth (this was assumed by the Pythagorean Philolaus) on the grounds that it should lead to a parallactic displacement of stars, which is not observed.

Several authors provide other empirical arguments. Pliny the Elder, in his encyclopedia Natural History, argues for the central location of the Earth by the equality of day and night during the equinoxes, and also by the fact that during the equinoxes, sunrise and sunset can be observed on the same line, and the sunrise on the summer solstice is located on the same line as sunset on the winter solstice. From the point of view of astronomy, these arguments and arguments are naturally misleading. The arguments that Cleomedes gave in his textbook “Lectures on Astronomy” are no better. He explains the centrality of the Earth by contradiction. He believed that if the Earth were located east of the center of the Universe, then the shadows at dawn would be shorter than at sunset, the celestial bodies at sunrise would appear larger than at sunset, and the duration from dawn to noon would be shorter than from noon until sunset. But since all this is missing, we can conclude that the Earth cannot be shifted to the west from the center of the world. By analogy it is proved that the Earth cannot be shifted to the west. Further, if the Earth were located north or south of the center, the shadows at sunrise would be in the north or south direction, respectively. In addition, at dawn on the days of the equinoxes, the shadows would be directed exactly in the direction of sunset on these days, and at sunrise on the day of the summer solstice, the shadows would point to the point of sunset on the day of the winter solstice. This also explains that the Earth is not displaced north or south of the center. If the Earth were located above the center, then less than half of the sky could be observed, including less than six signs of the zodiac; which would result in the night always being longer than the day. By analogy: The Earth cannot be below the center of the world. From all of the above, we can conclude that it can only be located in the center. Ptolemy expressed approximately similar arguments in favor of the centrality of the Earth in the Almagest, Book I. Of course, the arguments of Cleomedes and Ptolemy only confirm that the Universe is incomparably much larger than the Earth, and for this reason they are also unfounded.

1.3. Geocentric system of the world of Ptolemy

Ptolemy, emphasizing and building on the achievements of Hipparchus, explored the movable celestial bodies. He made a significant contribution to complementing and clarifying the concept of the movement of the Moon, and also improved the theory of eclipses. However, the scientist’s truly great scientific feat was his formation of a mathematical theory of the visible motion of planets. This theory was based on the following principles:

· Sphericality of the Earth;

· Huge distance from the sphere of stars;

· Uniformity and circular nature of the movements of celestial bodies;

· Immobility of the Earth;

· The central position of the Earth in the Universe.

Ptolemy's theory combined the concepts of epicycles and eccentrics. He made the assumption that around the stationary Earth there is a circle (deferent) with a center slightly shifted relative to the center of the Earth (eccentric). According to the deferent, the center of the smaller circle - the epicycle - moves with an angular velocity that is unchanged with respect to the deferent's own center and not to the Earth itself, but to a point that is located symmetrically to the center of the deferent relative to the earth (equant). The planet itself in the Ptolemaic system moves uniformly along the epicycle. In order to describe the newly discovered irregularities in the movements of the planets and the Moon, new additional epicycles were introduced - second, third, etc. The planet was located on the latter. Ptolemy's theory made it possible to pre-calculate the complex loop-like movements of the planets (their acceleration and deceleration, stationary and retrograde movements). Based on the astronomical tables formed by Ptolemy, the positions of the planets could be calculated with a very high accuracy for those times (there was an error of less than 10").

From the basic properties of planetary movements, the concept of which was defined by Ptolemy, several very important patterns can be identified:

1. The conditions for the movement of the planets above and below the Sun differ significantly.

2. The Sun plays a characteristic role in the movement of both planets.

The stages of planetary revolution, either by deferents (for the lower planets) or by epicycles (for the upper ones), will be equal to the period of revolution of the Sun, that is, a year long. The direction of the deferents of the lower planets and the epicycles of the upper ones is in connection with the plane of the ecliptic. A careful study of these properties of planetary motions would have led Ptolemy to a simple conclusion, which would have been this: the Sun, not the Earth, is the center of the planetary system. This conclusion was put forward by Aristarchus of Samos long before Ptolemy. He argued that the Earth is several times smaller than the Sun. Without a doubt, it is clear that the smaller body moves around the larger one, and not vice versa. Although Ptolemy was not able to determine the scale of other planets directly, it was nevertheless clear that they were all much smaller than the Sun.

Ptolemy's system not only explained the apparent motions of the planets, but also made it possible to calculate their positions for the future with an accuracy that fully satisfied imperfect research with the naked eye. That is why, although fundamentally incorrect, the system at first did not stimulate serious contradictions, and later open objections to it were brutally suppressed by the Christian Church.

Discrepancies between this concept and observations, which appeared as the accuracy of observations increased, were eliminated by increasing the complexity of the system. For example, some inaccuracies in the apparent movements of the planets, revealed by subsequent observations, were explained by the fact that it is not the planet that revolves around the center of the first epicycle, but the center of the second epicycle, along the circumference of which the planet moves. When inaccuracies appeared in a similar construction for any planet, a third, fourth, etc. were introduced. epicycles, until the position of the planet on the circle of the last of them gave more or less acceptable agreement with observations and research.

By the beginning of the 16th century. Ptolemy's system was so difficult that it was no longer able to satisfy the conditions and requirements that were imposed on astronomy by practical life, and primarily by navigation. Simpler methods were needed to calculate the positions of the planets. And thanks to the creation of the brilliant Polish scientist Nicolaus Copernicus, who subsequently developed and laid the foundation of astronomy, such methods were created and without them modern astronomy could not have appeared and developed.

> What is the geocentric model of the Universe?

: description of the movement of celestial bodies in orbits, model of Ancient Greece, Ptolemy and the Middle Ages, comparison with heliocentrism.

For thousands of years, people have looked at the night sky and tried to understand what the Universe is. And sometimes opinions differed radically. A long time ago, magicians and ancient sages firmly believed that the world is a flat (square) surface around which are located, and. Later they noticed that some stars did not move and began to call them planets.

Some time passes and humanity realizes that we live on a round object, so they began to adjust the surrounding mechanisms to this understanding. Gradually a new model was formed, from which emerged geocentric model of the world. Although it has not been used for a long time, it once answered fundamental questions about the structure of the Universe.

Of course, it is not surprising that people believed that our planet Earth stands at the center of everything, not just the solar system, but the entire Universe. Eventually, it was noticeable that the Sun and Moon were changing positions in the sky. So from the point of view of earthly observers, we are standing still, and everything around is moving.

Thus, the documents of the ancient Babylonians and Egyptians were taken into account, which fueled the theory that the Earth was at the center of everything. They continued to believe in this in the 17th and 18th centuries. But many inconsistencies arose, which forced us to look for a new model, since the geocentric model could not explain them.

Comparison of geocentric and heliocentric models of the Universe

Geocentric model of the Universe in Ancient Greece

There is no precise record of who first developed the geocentric model of the world, but early references date back to the 6th century BC. The philosopher Anaximander suggested that the Earth stands still, and the Sun and Moon revolve around. At the same time, the Pythagoreans add that our planet is round, since they saw eclipses. Until the 4th century BC this idea was combined with the geocentric Universe, which helped build the cosmological system.

Plato and Aristotle made great contributions to this idea. The first believed that the planet does not move. Spheres extend from it, on which the moving Sun, Moon and other planets are located. The model was extended by Eudoxus of Cnidus, who relied on a mathematical explanation of planetary motion. Aristotle then intervened and added that objects around move in concentric spheres.

Illustration of models of the Anixamadra Universe. On the left is during the day in the summer, and on the right is at night in the winter.

The spheres moved at different speeds and represented an indestructible substance - ether. Next, he added a description of the 4 most important elements: earth, water, fire, air, and also added “heavenly ether”.

Aristotle wrote that earth is the heaviest element, therefore it is attracted to the center, and the rest form layers around it. At the very end was the ether, in which celestial objects “floated”. Another important innovation is the addition of an “engine”. The philosopher believed that there was some force or even a being that sets the mechanism in motion.

Of course, all this was confirmed by certain theories. For example, if the planet were moving, then a significant displacement of the stars or . It turns out that they are motionless or located much further away. Of course, they preferred to choose the first option, since it is the simplest explanation.

The brightness of Venus served as further evidence. They believed that it was always located at the same distance from us at any time period. Of course, it later turned out that the planet has phases. But ancient people did not have telescopes.

Geocentric model of the Universe Ptolemy

Naturally, the described model had shortcomings, and the authors knew it. For example, the brightness of Mercury, Jupiter and Mars changed periodically. In addition, “retrograde movement” was noticed behind them, when they slowed down, found themselves behind, and then again advanced in movement.

All this introduced even more disagreements, which the Egyptian-Greek astronomer Ptolemy had to resolve. In the second century AD. he writes "Almagest". It introduced the geocentric model of the Universe from Ptolemy, which would be considered dominant for the next 1500 years. He followed the ancient traditions and repeated that the Earth is located in the center, and objects move around it.

Here a new idea appears - the existence of two spheres. The first is the deferent, which is a circle distant from our planet. It was used to account for differences in the length of seasons. The second is the epicycle. It was in the first sphere (a circle within a circle) and explained the retrograde movement of the planets.

But even this did not dispel all doubts. What was especially disturbing was that the retrograde loop of the planets (primarily) was sometimes larger or smaller than expected. To remove this issue, Ptolemy created an equant - a geometric instrument near the center of the planetary orbit, which set it in motion with a uniform angular velocity.

To the observer at this point it seems that the epicycle is always moving at a constant speed. The system lasted throughout the Roman Empire, medieval Europe and the Islamic world, remaining unchanged for a thousand years. But this mechanism seemed incredibly complex and cumbersome.

Geocentric model of the Universe in the Middle Ages

In the Middle Ages, the theme of the geocentric model again became relevant, as it fit well with Christian beliefs. Thomas Aquinas took up the development of the system, trying to unite faith and reason.

Pages from the Treatise of the Sphere (1550), depicting the Ptolemaic system

It all started with the fact that the planet was divided into “heaven” and Earth. The earth was located at the center of creation, and the heavens were beyond it. All this fueled the Christian belief that man is the main creation of God. In addition, Aristotle’s “engine” came in handy, whose place was taken by God.

Of course, no one dared to challenge the idea that the heavens revolved around the planet, because it was heresy and even punishable. The situation remained this way until the publication of the book “On the Rotation of the Celestial Spheres” in the 16th century. Its author is Nicolaus Copernicus, who dared to prove the correctness of the heliocentric model of the Universe. Of course, under conditions of persecution and persecution, the work had to be published posthumously, and the geocentric and heliocentric models became rivals.

It is worth noting that in the Muslim world the geocentric model also existed in the Middle Ages. But already from the 10th century AD. Astronomers emerged to challenge Ptolemy's work. Among them was As-Sijizi (945-1020). He believed that the Earth rotates around its axis and around the Sun. But he approached from the side of philosophy, not mathematics.

Several Andalusian astronomers also opposed the geocentric model in the 11th and 12th centuries. Arzakel completely abandoned the Greek theories of uniform circular motion and said that Mercury travels in an ellipse.

In the 12th century Alptragius became involved. He created a new model that did not need an equant, epicycle and eccentricity. This idea was accompanied by the publication of Fakhruddin al-Razi's Mataliba, which dealt with conceptual physics. It refuted the idea of ​​the centrality of the Earth. Instead, he suggested that there is our world, beyond which there are thousands of other worlds.

The Earth's rotation was a popular topic of discussion at the Magar Observatory (Eastern Iran) in the 13th to 15th centuries. Although all this developed at the level of philosophy and did not concern heliocentrism, many of the evidence were reminiscent of those that Copernicus would later voice.

Heliocentric model and geocentric model of the Universe

Nicolaus Copernicus begins developing the heliocentric model in the 16th century. It contains all his thoughts and scientific works. It was not created from scratch, but used the developments of the opposition geocentrists.

In 1514, Copernicus published a small treatise, “Little Commentary,” which he distributed to his friends. The manuscript was only 40 pages, succinctly describing the heliocentric hypothesis. It was all based on 7 main principles:

  • The center of the Earth is the center of the lunar sphere (the Moon revolves around the Earth).
  • All spheres revolve around the Sun, which is located near the universal center.
  • The distance between the Earth and the Sun is a small fraction of the distance from the Sun to other stars, so we do not see parallax.
  • The stars are motionless. It seems to us that they are moving because the Earth rotates around its axis.
  • The Earth revolves around the Sun, which makes the Sun appear to migrate.
  • The Earth has more than one movement.
  • The Earth moves in orbit around the Sun, which makes the planets around it appear to be going in the wrong direction.

Another equally famous scientist of antiquity, Democritus - the founder of the concept of atoms, who lived 400 years BC - believed that the Sun is many times larger than the Earth, that the Moon itself does not glow, but only reflects sunlight, and the Milky Way consists of a huge number of stars. Summarize all the knowledge that had been accumulated by the 4th century. BC e., was able to the outstanding philosopher of the ancient world Aristotle (384-322 BC).

Rice. 1. Geocentric system of the world of Aristotle-Ptolemy.

His activities covered all natural sciences - information about the sky and Earth, about the patterns of movement of bodies, about animals and plants, etc. Aristotle's main merit as an encyclopedist scientist was the creation of a unified system of scientific knowledge. For almost two thousand years, his opinion on many issues was not questioned. According to Aristotle, everything heavy tends to the center of the Universe, where it accumulates and forms a spherical mass - the Earth. The planets are placed on special spheres that revolve around the Earth. Such a system of the world was called geocentric (from the Greek name for the Earth - Gaia). It was not by chance that Aristotle proposed to consider the Earth as the immovable center of the world. If the Earth moved, then, according to Aristotle’s fair opinion, a regular change in the relative positions of the stars on the celestial sphere would be noticeable. But none of the astronomers observed anything like this. Only at the beginning of the 19th century. The displacement of stars (parallax) resulting from the movement of the Earth around the Sun was finally discovered and measured. Many of Aristotle's generalizations were based on conclusions that could not be verified by experience at that time. Thus, he argued that the movement of a body cannot occur unless a force acts on it. As you know from your physics course, these ideas were refuted only in the 17th century. during the times of Galileo and Newton.

Heliocentric model of the Universe

Among ancient scientists, Aristarchus of Samos, who lived in the 3rd century, stands out for the boldness of his guesses. BC e. He was the first to determine the distance to the Moon and calculate the size of the Sun, which, according to his data, turned out to be more than 300 times larger than the Earth in volume. Probably, these data became one of the grounds for the conclusion that the Earth, along with other planets, moves around this largest body. Nowadays, Aristarchus of Samos has come to be called the “Copernicus of the ancient world.” This scientist introduced something new into the study of the stars. He believed that they were immeasurably further from the Earth than the Sun. For that era, this discovery was very important: from a cozy little home, the Universe was turning into an immense giant world. In this world, the Earth with its mountains and plains, with forests and fields, with seas and oceans became a tiny speck of dust, lost in a grandiose empty space. Unfortunately, the works of this remarkable scientist have practically not reached us, and for more than one and a half thousand years, humanity was sure that the Earth was the immovable center of the world. To a large extent, this was facilitated by the mathematical description of the visible movement of the luminaries, which was developed for the geocentric system of the world by one of the outstanding mathematicians of antiquity - Claudius Ptolemy in the 2nd century. AD The most difficult task was to explain the loop-like motion of the planets.

Ptolemy, in his famous work “Mathematical Treatise on Astronomy” (better known as “Almagest”) argued that each planet moves uniformly along an epicycle - a small circle, the center of which moves around the Earth along a deferent - a large circle. Thus, he was able to explain the special nature of the movement of the planets, which distinguished them from the Sun and Moon. The Ptolemaic system gave a purely kinematic description of the motion of the planets - the science of that time could not offer anything else. You have already seen that using a model of the celestial sphere to describe the movement of the Sun, Moon and stars allows you to carry out many calculations useful for practical purposes, although in reality such a sphere does not exist. The same is true for epicycles and deferents, on the basis of which the positions of the planets can be calculated with a certain degree of accuracy.


Rice. 2.

However, over time, the requirements for the accuracy of these calculations constantly increased, and more and more new epicycles had to be added for each planet. All this complicated the Ptolemaic system, making it unnecessarily cumbersome and inconvenient for practical calculations. Nevertheless, the geocentric system remained unshakable for about 1000 years. After all, after the heyday of ancient culture in Europe, a long period began during which not a single significant discovery was made in astronomy and many other sciences. Only during the Renaissance did a rise in the development of sciences begin, in which astronomy became one of the leaders. In 1543, a book by the outstanding Polish scientist Nicolaus Copernicus (1473-1543) was published, in which he substantiated a new - heliocentric - system of the world. Copernicus showed that the daily motion of all the stars can be explained by the rotation of the Earth around its axis, and the loop-like motion of the planets by the fact that all of them, including the Earth, revolve around the Sun.

The figure shows the movement of the Earth and Mars during the period when, as it seems to us, the planet is describing a loop in the sky. The creation of the heliocentric system marked a new stage in the development of not only astronomy, but also all natural science. A particularly important role was played by Copernicus’s idea that behind the visible picture of occurring phenomena, which seems true to us, we must look for and find the essence of these phenomena, inaccessible to direct observation. The heliocentric system of the world, substantiated but not proven by Copernicus, was confirmed and developed in the works of such outstanding scientists as Galileo Galilei and Johannes Kepler.

Galileo (1564-1642), one of the first to point a telescope at the sky, interpreted the discoveries made as evidence in favor of the Copernican theory. Having discovered the change of phases of Venus, he came to the conclusion that such a sequence can only be observed if it revolves around the Sun.

Rice. 3.

The four satellites of the planet Jupiter that he discovered also refuted the idea that the Earth is the only center in the world around which other bodies can rotate. Galileo not only saw mountains on the Moon, but even measured their height. Along with several other scientists, he also observed sunspots and noticed their movement across the solar disk. On this basis, he concluded that the Sun rotates and, therefore, has the kind of motion that Copernicus attributed to our planet. Thus, it was concluded that the Sun and Moon have a certain similarity with the Earth. Finally, observing many faint stars in and outside the Milky Way, inaccessible to the naked eye, Galileo concluded that the distances to the stars are different and that no “sphere of fixed stars” exists. All these discoveries became a new stage in understanding the position of the Earth in the Universe.