Astronomy of Ancient Greece - astronomical knowledge and views of those people who wrote on ancient Greek, regardless of the geographical region: Hellas itself, the Hellenized monarchies of the East, Rome or early Byzantium. Covers the period from the 6th century BC. h. to the 5th century AD e. Ancient Greek astronomy is one of the most important stages in the development of not only astronomy as such, but also science in general. In the works of ancient Greek scientists are the origins of many ideas that underlie the science of modern times. Between modern and ancient Greek astronomy there is a relationship of direct succession, while the science of other ancient civilizations influenced modern only through the mediation of the Greeks.
The Hellenes, apparently, were interested in astronomy even in Homeric times, their map of the sky and many names have remained in modern science. Initially, knowledge was shallow - for example, morning and evening Venus were considered different luminaries (Phosphorus and Hesperus); the Sumerians already knew that it was one and the same star. The correction of the "doubling of Venus" error is attributed to Pythagoras and Parmenides.
The pole of the world at that time had already left Alpha Draconis, but had not yet moved closer to Polar; maybe that's why the Odyssey never mentions the direction to the north.
The Pythagoreans proposed a pyrocentric model of the Universe in which the stars, the Sun, the Moon and six planets revolve around the Central Fire (Hestia). In order to get the sacred number - ten - spheres in total, the Counter-Earth (Antichthon) was declared the sixth planet. Both the Sun and the Moon, according to this theory, shone with the reflected light of Hestia. It was the first mathematical system of the world - the rest of the ancient cosmogonists worked more with imagination than logic.
The distances between the spheres of the luminaries among the Pythagoreans corresponded to the musical intervals in the scale; when they rotate, the “music of the spheres” sounds, inaudible to us. The Pythagoreans considered the Earth to be spherical and rotating, which is why the change of day and night occurs. However, individual Pythagoreans (Aristarchus of Samos and others) adhered to the heliocentric system. The Pythagoreans first arose the concept of ether, but most often this word denoted air. Only Plato singled out ether as a separate element.
Plato, a student of Socrates, no longer doubted the sphericity of the Earth (even Democritus considered it to be a disk). According to Plato, the Cosmos is not eternal, since everything that is felt is a thing, and things grow old and die. Moreover, Time itself was born together with the Cosmos. Plato's call to astronomers had far-reaching consequences uneven movements shone on "perfect" movements in circles.
Eudoxus of Cnidus, the teacher of Archimedes and himself a student of the Egyptian priests, responded to this call. In his (non-surviving) writings, he outlined a kinematic scheme for the motion of the planets with several superimposed circular motions, over 27 spheres in total. True, the agreement with the observations for Mars was poor. The fact is that the orbit of Mars differs markedly from a circular one, so that the trajectory and speed of the planet's movement across the sky vary widely. Eudoxus also compiled a star catalog.
Aristotle, the author of the Physics, was also a student of Plato. There were many in his writings. rational thoughts; he convincingly proved that the Earth is a ball, based on the shape of the Earth's shadow during lunar eclipses, estimated the circumference of the Earth at 400,000 stadia, or about 70,000 km - almost doubled, but for that time the accuracy was not bad. But there are also many erroneous statements: the separation of the earthly and heavenly laws of the world, the denial of emptiness and atomism, the four elements as the fundamental principles of matter plus the celestial ether, contradictory mechanics: “air pushes an arrow in flight” - even in the Middle Ages this ridiculous position was ridiculed (Filopon, Buridan ). He considered meteors to be atmospheric phenomena, akin to lightning.
The concepts of Aristotle were canonized by some philosophers during his lifetime, and in the future many sound ideas that contradicted them met with hostility - for example, the heliocentrism of Aristarchus of Samos. Aristarchus also tried for the first time to measure the distance to the Sun and the Moon and their diameters; for the Sun, he was wrong by an order of magnitude (it turned out that the diameter of the Sun is 250 times larger than the earth), but before Aristarchus, everyone believed that the Sun was smaller than the Earth. That is why he decided that the Sun is at the center of the world. More accurate measurements of the angular diameter of the Sun were made by Archimedes, and it is in his retelling that we know the views of Aristarchus, whose writings have been lost.
Eratosthenes in 240 BC e. quite accurately measured the length of the earth's circumference and the inclination of the ecliptic to the equator (i.e., the inclination of the earth's axis); he also proposed a system of leap years, later called the Julian calendar.
From the III century BC. e. Greek science adopted the achievements of the Babylonians, including in astronomy and mathematics. But the Greeks went much further. About 230 B.C. e. Apollonius of Perga developed a new method for representing uneven periodical movement through the base circle - the deferent - and the secondary circle circling around the deferent - the epicycle; the luminary itself moves along the epicycle. This method was introduced into astronomy by the outstanding astronomer Hipparchus, who worked on Rhodes.
Hipparchus discovered the difference between the tropical and sidereal years, specified the length of the year (365.25 - 1/300 days). Apollonius' technique allowed him to build mathematical theory movements of the sun and moon. Hipparchus introduced the concepts of orbital eccentricity, apogee and perigee, clarified the duration of the synodic and sidereal lunar months (up to a second), and the average periods of planetary revolution. According to the tables of Hipparchus, it was possible to predict solar and lunar eclipses with an accuracy unheard of at that time - up to 1-2 hours. By the way, it was he who introduced geographic coordinates - latitude and longitude. But the main result of Hipparchus was the discovery of the displacement of celestial coordinates - "preceding the equinoxes." After studying observational data for 169 years, he found that the position of the Sun at the time of the equinox shifted by 2 °, or 47 "per year (actually - by 50.3").
In 134 BC. e. A new bright star has appeared in the constellation Scorpio. To make it easier to track changes in the sky, Hipparchus compiled a catalog of 850 stars, dividing them into 6 brightness classes.
46 BC BC: the Julian calendar was introduced, developed by the Alexandrian astronomer Sosigen on the model of the Egyptian civil. The chronology of Rome was conducted from the legendary foundation of Rome - from April 21, 753 BC. e.
The system of Hipparchus was completed by the great Alexandrian astronomer, mathematician, optician and geographer Claudius Ptolemy. He significantly improved spherical trigonometry, compiled a table of sines (through 0.5 °). But his main achievement is "Megale syntax" (Great construction); the Arabs turned this name into "Al Majisti", hence the later "Almagest". The work contains a fundamental exposition of the geocentric system of the world.
Being fundamentally wrong, Ptolemy's system, nevertheless, made it possible to predict the positions of the planets in the sky with sufficient accuracy for that time and therefore satisfied, up to to some extent, practical requests for many centuries.
The system of the world of Ptolemy completes the stage of development of ancient Greek astronomy.
The spread of Christianity and the development of feudalism in the Middle Ages led to a loss of interest in the natural sciences, and the development of astronomy in Europe slowed down for many centuries.
The next period in the development of astronomy is associated with the activities of scientists from the countries of Islam - al-Battani, al-Biruni, Abu-l-Hasan ibn Yunis, Nasir ad-Din at-Tusi, Ulugbek and many others.
The history of ancient Greek astronomy can be divided into four periods associated with various stages in the development of ancient society:
Archaic (pre-scientific) period (until the 6th century BC): the formation of the polis structure in Hellas;
Classical period (VI-IV centuries BC): the heyday of the ancient Greek policy;
Hellenistic period (III-II centuries BC): the heyday of large monarchical powers that arose on the ruins of the empire of Alexander the Great; in terms of science special role plays Ptolemaic Egypt with its capital in Alexandria;
Period of decline (1st century BC - 1st century AD) associated with gradual fading Hellenistic powers and the growing influence of Rome;
Imperial period (2nd-5th centuries AD): the unification of the entire Mediterranean, including Greece and Egypt, under the rule of the Roman Empire.
This periodization is rather schematic. In a number of cases it is difficult to establish the affiliation of one or another achievement to one or another period. So, although the general character of astronomy and science in general in the classical and Hellenistic periods looks quite different, on the whole, development in the 6th-2nd centuries BC e. appears to be more or less continuous. On the other hand, a number of scientific achievements of the last, imperial period (especially in the field of astronomical instrumentation and, possibly, theory) are nothing more than a repetition of the successes achieved by astronomers of the Hellenistic era.
The "father of philosophy" Thales of Miletus saw a natural object as this support - the oceans. Anaximander of Miletus suggested that the Universe is centrally symmetrical and does not have any preferred 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 shared by the Pythagoreans, Parmenides and Ptolemy. The position of Democritus is not clear: according to various testimonies, he followed Anaximander or Anaximenes.
Anaximander considered the Earth to have the shape of a low cylinder with a height three times less than the diameter of the base. Anaximenes, Anaxagoras, Leucippus considered the Earth to be 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, Aristotle. This is how the canonical form of the geocentric system arose, which was subsequently actively developed by ancient Greek astronomers: the spherical Earth is 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.
As for the order of the luminaries, Anaximander considered the stars located closest to the Earth, followed by the Moon and the Sun. Anaximenes first suggested that the stars are the objects farthest from the 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 (probably for the first time among Anaximenes or the Pythagoreans) that what longer period the circulation of the luminary in the celestial sphere, the higher it is. Thus, the order of the luminaries turned out to be the following: 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 after the Sun, Ptolemy - between the Moon and the Sun. Aristotle believed that there is nothing above the sphere of fixed stars, not even space, while the Stoics believed that our world is immersed in infinite 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 stated by Lucretius in the poem "On the Nature of Things."
Ancient Greek scientists, however, substantiated in different ways central position and the immobility of the earth. Anaximander, as has already been pointed out, pointed out the spherical symmetry of the Cosmos as the reason. Aristotle did not support him, putting forward a counterargument later attributed to Buridan: in this case, the person in the center of the room in which food is located near the walls must die of hunger (see Buridan's donkey). Aristotle himself justified geocentrism as follows: the Earth is a heavy body, and 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, the orbital motion of the Earth (which the Pythagorean Philolaus assumed) was rejected by Aristotle on the grounds that it should lead to a parallactic displacement of the stars, which is not observed.
A number of authors give 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, sunrise and sunset are observed on the same line, and sunrise on the summer solstice is on the same line as sunset on the winter solstice . From an astronomical point of view, all these arguments are, of course, a misunderstanding. Slightly better are the arguments given by Cleomedes in the textbook "Lectures on Astronomy", where he substantiates the centrality of the Earth from the contrary. 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 less than from noon to sunset. Since all this is not observed, the Earth cannot be shifted east of the center of the world. Similarly, it is proved that the Earth cannot be displaced to the west. Further, if the Earth were located north or south of the center, the shadows at sunrise would extend in the north or southbound, respectively. Moreover, at dawn on the equinoxes, the shadows are directed exactly in the direction of the sunset on those days, and at sunrise on the summer solstice, the shadows point to the point of sunset on the winter solstice. It also indicates that the Earth is not offset north or south of center. If the Earth were higher than 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 a day. Similarly, it is proved that the Earth cannot be located below the center of the world. Thus, it can only be in the center. Approximately the same arguments in favor of the centrality of the Earth are given by Ptolemy 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.
Ptolemy is also trying to justify the immobility of the Earth (Almagest, book I). First, if the Earth were displaced from the center, then the effects just described would be observed, and if they are not, the Earth is always in the center. Another argument is the verticality of the trajectories of falling bodies. Absence axial rotation Ptolemy justifies 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 reverse direction; neither clouds nor other flying or hovering objects will ever be seen moving eastward, as the Earth's movement towards the east will always throw them away, so that these objects will appear to be moving westward, in the opposite direction." The inconsistency of this argument became clear only after the discovery of the foundations of mechanics.
Scheme of the geocentric system of the world (from the book of David Hans "Nehmad Venaim", XVI century). The spheres are signed: air, the Moon, Mercury, Venus, the Sun, the sphere of fixed stars, the sphere responsible for the anticipation of the equinoxes.
Classical period (from VI - to IV century BC)
Main actors of this period are philosophers who intuitively grope for what will later be called the scientific method of cognition. At the same time, the first specialized astronomical observations are being made, the theory and practice of the calendar is being developed; for the first time, geometry is taken as the basis of astronomy, a number of abstract concepts of mathematical astronomy are introduced; attempts are being made to find physical patterns in the movement of the luminaries. Got scientific explanation a number of astronomical phenomena, proved the sphericity of the Earth. At the same time, the connection between astronomical observations and theory is still not strong enough; there is too much speculation based on purely aesthetic considerations.
Sources
Only two specialized astronomical works of this period have come down to us, the treatises On the Revolving Sphere and On the Rising and Setting of the Stars by Autolycus of Pitana - textbooks on the geometry of the celestial sphere, written at the very end of this period, around 310 BC. e. They are also adjoined by the poem Phenomena of Arata from Sol (written, however, in the first half of the 3rd century BC), which contains a description of the ancient Greek constellations (a poetic transcription of the works of Eudoxus of Knidos that have not come down to us, 4th century BC) .
Astronomical issues are often touched upon in the works of ancient Greek philosophers: some of Plato's dialogues (especially Timaeus, as well as the State, Phaedo, Laws, Post-law), Aristotle's treatises (especially On Heaven, as well as Meteorology, Physics, Metaphysics). The works of philosophers of an earlier time (pre-Socratics) have come down to us only in a very fragmentary form through second, and even third hands.
Philosophical Foundation of Astronomy
Presocratics, Plato
During this period, two fundamentally different philosophical approach science in general and astronomy in particular. The first of them originated in Ionia and therefore can be called Ionian. It is characterized by attempts to find the material fundamental principle of being, by changing which philosophers hoped to explain all the diversity of nature. In move celestial bodies these philosophers tried to see manifestations of the same forces that operate on Earth. Initially, the Ionian direction was represented by the philosophers of the city of Miletus Thales, Anaximander and Anaximenes. This approach found its supporters in other parts of Hellas. Among the Ionians is Anaxagoras of Clazomene, who spent a significant part of his life in Athens, to a large extent a native of Sicily, Empedocles of Acragas. The Ionian approach reached its peak in the writings of the ancient atomists: Leucippus (probably also from Miletus) and Democritus from Abdera, who were the forerunners of mechanistic philosophy.
The desire to give a causal explanation of natural phenomena was the strength of the Ionians. In the present state of the world, they saw the result of the action of physical forces, and not mythical gods and monsters. The Ionians considered the heavenly bodies to be objects, in principle, of the same nature as the earthly stones, the movement of which is controlled by the same forces that act on Earth. They considered the daily rotation of the firmament to be a relic of the original vortex motion, covering all the matter of the Universe. The Ionian philosophers were the first to be called physicists. However, the shortcoming of the teachings of the Ionian natural philosophers was an attempt to create physics without mathematics. The Ionians did not see the geometric basis of the Cosmos.
The second direction of early Greek philosophy can be called Italian, since it received its initial development in Greek colonies the Italian peninsula. Its founder Pythagoras founded the famous religious and philosophical union, whose representatives, unlike the Ionians, saw the basis of the world in mathematical harmony, more precisely, in the harmony of numbers, while striving for the unity of science and religion. They considered the heavenly bodies to be gods. This was justified as follows: the gods are a perfect mind, they are characterized by the most perfect type of movement; this is the circumferential motion, because it is eternal, has no beginning and no end, and always passes into itself. As astronomical observations show, celestial bodies move in circles, therefore, they are gods. The heir of the Pythagoreans was the great Athenian philosopher Plato, who believed that the entire Cosmos was created by an ideal deity in his own image and likeness. Although the Pythagoreans and Plato believed in the divinity of the heavenly bodies, they were not characterized by faith in astrology: an extremely skeptical review of it by Eudoxus, a student of Plato and a follower of the philosophy of the Pythagoreans, is known
Beginning with Thales of Miletus, phenomena associated with the Sun were also intensively observed: solstices and equinoxes. According to the evidence that has come down to us, the astronomer Cleostratus of Tenedos (about 500 BC) was the first in Greece to establish that the constellations of Aries, Sagittarius and Scorpio are zodiac, that is, the Sun passes through them in its movement through the celestial sphere. The earliest evidence of Greek knowledge of all the zodiac constellations is a calendar compiled by the Athenian astronomer Euctemon in the middle of the 5th century BC. e. The same Euctemon first established the inequality of the seasons, associated with the uneven movement of the Sun along the ecliptic. According to his measurements, the length of astronomical spring, summer, autumn and winter is, respectively, 93, 90, 90 and 92 days (in fact, respectively, 94.1 days, 92.2 days, 88.6 days, 90.4 days). A much higher accuracy characterizes the measurements of Callippus of Cyzicus, who lived a century later: according to him, spring lasts 94 days, summer 92 days, autumn 89 days, winter 90 days.
Ancient Greek scientists also recorded the appearance of comets, the occultation of the planets by the Moon.
Almost nothing is known about the astronomical instruments of the Greeks of the classical period. It was reported about Anaximander of Miletus that he used a gnomon, the oldest astronomical instrument, which is a vertically located rod, to recognize the equinoxes and solstices. Eudoxus is also credited with the invention of the "spider" - the main structural element of the astrolabe.
Spherical Sundial
To calculate the time during the day, apparently, often used a sundial. First, spherical sundials (skafe) were invented as the simplest ones. Improvements in the design of the sundial were also attributed to Eudoxus. It was probably the invention of one of the varieties of flat sundials.
The Greek calendar was lunisolar. Among the authors of calendars (the so-called parapegmas) were such famous scientists as Democritus, Meton, Euctemon. Parepegmas were often carved on stone stelae and columns set in in public places. In Athens, there was a calendar based on an 8-year cycle (according to some reports, introduced by the famous legislator Solon). A significant improvement in the lunisolar calendar belongs to the Athenian astronomer Meton, who discovered the 19-year calendar cycle:
19 years = 235 synodic months = 6940 days.
During this period of time, the dates of the solstices and equinoxes gradually change and the same lunar phase falls on a different one each time. calendar date, however, at the end of the cycle, the solstice and equinox fall on the same date, and on this day the same phase of the moon takes place as at the beginning of the cycle. However, the Metonic cycle was never put at the basis of the Athenian civil calendar (and its discoverer was ridiculed in one of Aristophanes' comedies).
The Metonic cycle was refined by Callippus, who lived about a century after Meton: he combined four cycles, while omitting 1 day. Thus, the duration of the callippe cycle was
76 years = 940 months = 27759 days.
A year in the Callippus cycle is 365.25 days (the same value is accepted in the Julian calendar). The length of the month is 29.5309 days, which is only 22 seconds longer than its true value. Based on these data, Kallippus compiled his own calendar.
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Cosmology
Depiction of a geocentric system (from Peter Apian's Cosmographia, 1524)
In the classical era, a geocentric system of the world arose, according to which the motionless spherical Earth is in the center of the spherical Universe and the visible daily movement of the heavenly bodies is a reflection of the rotation of the Cosmos around the world axis. Its forerunner is Anaximander of Miletus. His system of the world contained three revolutionary moments: the flat Earth is located without any support, the paths of celestial bodies are whole circles, celestial bodies are at various distances from the Earth. Pythagoras went even further, suggesting that the Earth has the shape of a ball. This hypothesis met with much resistance at first; so, among her opponents were the famous Ionian philosophers Anaxagoras, Empedocles, Leucippus, Democritus. However, after its support by Parmenides, Plato, Eudoxus and Aristotle, it became the basis of all mathematical astronomy and geography.
If Anaximander considered the stars located closest to the Earth (the Moon and the Sun followed), then his student Anaximenes for the first time suggested that the stars are the objects farthest from the Earth, fixed on the outer shell of the Cosmos. An opinion arose (for the first time, probably, among Anaximenes or the Pythagoreans) that the period of revolution of the star in the celestial sphere increases with increasing distance from the Earth. Thus, the order of the luminaries turned out to be the following: Moon, Sun, Mars, Jupiter, Saturn, stars. Mercury and Venus are not included here, because their period of revolution in the celestial sphere is one year, like that of the Sun. Aristotle and Plato placed these planets between the Sun and Mars. Aristotle substantiated this by the fact that none of the planets ever obscured the Sun and the Moon, although the opposite (the covering of the planets by the Moon) was observed more than once.
Beginning with Anaximander, numerous attempts were made to establish the distances from the Earth to celestial bodies. These attempts were based on speculative Pythagorean considerations about the harmony of the world. They are reflected, in particular, in Plato.
Ionian philosophers believed that the movement of heavenly bodies was controlled by forces similar to those that operate on an earthly scale. So, Empedocles, Anaxagoras, Democritus believed that celestial bodies do not fall to Earth, since they are held by centrifugal force. The Italians (Pythagoreans and Plato) believed that the luminaries, being gods, move by themselves, like living beings.
Aristotle believed that celestial bodies are carried in their movement by solid celestial spheres to which they are attached. In his treatise On the Heavens, he argued that the celestial bodies make uniform circular motions simply because such is the nature of the ether that composes them. In Metaphysics, he expresses a different opinion: everything that moves is set in motion by something external, which, in turn, is also moved by something, and so on, until we reach the engine, which itself is motionless. Thus, if the celestial bodies move by means of the spheres to which they are attached, then these spheres are set in motion by engines that are themselves motionless. Each celestial body is responsible for several "fixed engines", according to the number of spheres that carry it. The sphere of fixed stars located on the border of the world should have only one engine, since it performs only one movement - a daily rotation around its axis. Since this sphere covers the whole world, the corresponding engine (prime mover) is ultimately the source of all movements in the universe. All motionless engines share the same qualities as the Prime Mover: they are intangible incorporeal formations and represent pure reason (Latin medieval scientists called them intelligentsia and usually identified with angels).
The geocentric system of the world became the main cosmological model until the 17th century AD. e. However, scientists of the classical period developed other views. So, among the Pythagoreans, it was quite widely believed (promulgated by Philolaus of Croton at the end of the 5th century BC) that in the middle of the world there is a certain Central fire, around which, along with the planets, the Earth also rotates, making a complete revolution per day; The central fire is invisible, since another celestial body, the Counter-Earth, moves between it and the Earth. Despite the artificiality of this system of the world, it had essential for the development of science, since for the first time in history the Earth was named as one of the planets. The Pythagoreans also put forward the opinion that the daily rotation of the sky is due to the rotation of the Earth around its axis. This opinion was supported and substantiated by Heraclides of Pontus (2nd half of the 4th century BC). In addition, on the basis of the meager information that has come down to us, it can be assumed that Heraclid considered Venus and Mercury to revolve around the Sun, which, in turn, revolves around the Earth. There is another reconstruction of the system of the world of Heraclid: the Sun, Venus, and the Earth revolve in circles around single center, and the period of one revolution of the Earth equals a year. In this case, Heraclid's theory was an organic development of the system of the world of Philolaus and the immediate predecessor of the heliocentric system of the world of Aristarchus.
There has been considerable disagreement among philosophers about what is outside the Cosmos. Some philosophers believed that there is an infinite empty space; according to Aristotle, there is nothing outside the Cosmos, not even space; the atomists Leucippus, Democritus and their supporters believed that behind our world (limited by the sphere of fixed stars) there are other worlds. The views of Heraclides of Pontus were closest to modern ones, according to which the fixed stars are other worlds located in infinite space.
Explanation of astronomical phenomena from the standpoint of geocentrism
The greatest difficulty for ancient Greek astronomy was the uneven movement of the celestial bodies (especially the backward movements of the planets), since in the Pythagorean-Platonic tradition (which Aristotle largely followed), they were considered deities who should make only uniform movements. To overcome this difficulty, models were created in which the complex apparent motions of the planets were explained as the result of the addition of several uniform circular motions. The concrete embodiment of this principle was the theory of homocentric spheres of Eudoxus-Callippus, supported by Aristotle, and the theory of epicycles by Apollonius of Perga, Hipparchus and Ptolemy. However, the latter was forced to partially abandon the principle of uniform motions, introducing the equant model.
Already one of the first ideas opposed to geocentrism (the heliocentric hypothesis of Aristarchus of Samos) led to a reaction on the part of representatives of religious philosophy: the Stoic Cleanthes called for Aristarchus to be brought to justice for moving the “Center of the World” from its place, meaning the Earth; it is not known, however, whether the efforts of Cleanthes 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 also successfully adapted to Christianity. This was also facilitated by a literal reading of the Bible.
Imperial period (II-V centuries AD)
Astronomy is gradually reviving, but with a noticeable admixture of astrology. During this period, a number of generalizing astronomical works were created. However, the new heyday is rapidly replaced by stagnation and then a new crisis, this time even deeper, associated with the general decline of culture during the collapse of the Roman Empire, as well as with a radical revision of the values of ancient civilization, produced by early Christianity.
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Sources
The writings of Claudius Ptolemy (2nd half of the 2nd century AD) have come down to us:
Illustration from the Almagest (Latin translation by George of Trebizond, 1451)
Almagest, affecting almost all aspects of mathematical astronomy of antiquity - main source our knowledge of ancient astronomy; contains the famous Ptolemaic theory of planetary motions;
The Canopic inscription is a preliminary version of the parameters of his planetary theory, carved on a stone stele;
Hand tables - tables of planetary movements, compiled on the basis of the theories set forth in the Almagest;
Planetary hypotheses, which contains Ptolemy's cosmological scheme.
About the planisphere, which describes the theory of stereographic projection underlying a certain "horoscopic instrument" (probably the astrolabe).
On the rising of the fixed stars, which presents a calendar based on the moments of the heliactic risings of stars during the year.
Some astronomical information is contained in other works of Ptolemy: Optics, Geography and a treatise on astrology, the Four Books.
Perhaps in the I-II centuries. AD other works of the same nature as the Almagest were written, but they have not reached us.
During this period, two treatises on spherical astronomy, known as the Sferica, were also written. One of them is a fundamental work written by the outstanding astronomer Menelaus of Alexandria (1st century AD), which outlines the basics of spherical trigonometry (the internal geometry of spherical surfaces). The second work was written by Theodosius (1st or 2nd century AD) and is intermediate in level between the works of the early authors (Autolycus and Euclid) and Menelaus. Theodosius also owns two more works that have come down to us: On dwellings, where a description of the starry sky is given from the point of view of observers located at different geographical latitudes, and On days and nights, where the movement of the Sun along the ecliptic is considered. A short treatise Astronomy of Hyginus (1st century AD) is devoted to the description of the view of the starry sky.
Astronomy issues are also considered in a number of commentary works written during this period (authors: Theon of Smyrna, II century AD, Simplicius, V century AD, Censorinus, III century AD, Pappus of Alexandria, III or IV century AD, Theon of Alexandria, IV century AD, Proclus, V century AD, etc.). Some astronomical issues are also considered in the works of the encyclopedist Pliny the Elder, the philosophers Cicero, Seneca, Lucretius, the architect Vitruvius, the geographer Strabo, the astrologers Manilius and Vettius Valens, the mechanic Heron of Alexandria, the theologian Synesius of Cyrene.
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Practical astronomy
Triquetrum of Claudius Ptolemy (from a 1544 book)
The task of planetary observations of the period under consideration is to provide numerical material for the theories of the motion of the planets, the Sun and the Moon. For this purpose, Menelaus of Alexandria, Claudius Ptolemy and other astronomers made their observations (there is a tense discussion on the authenticity of Ptolemy's observations). In the case of the Sun, the main efforts of astronomers were still aimed at accurately fixing the moments of the equinoxes and solstices. In the case of the Moon, eclipses were observed (the exact moment of the largest phase and the position of the Moon among the stars were recorded), as well as quadrature moments. For inner planets(Mercury and Venus), the main interest was the greatest elongations when these planets are at the greatest angular distance from the Sun. At outer planets special emphasis was placed on fixing the moments of opposition with the Sun and their observation at intermediate moments of time, as well as on studying their backward movements. great attention astronomers were also attracted by such rare phenomena as conjunctions of planets with the Moon, stars, and with each other.
Observations of the coordinates of stars were also made. Ptolemy cites a star catalog in the Almagest, where, according to him, he observed each star independently. It is possible, however, that this catalog is almost entirely the catalog of Hipparchus with the coordinates of stars recalculated due to precession.
The last astronomical observations in antiquity were made at the end of the 5th century by Proclus and his students Heliodorus and Ammonius.
Ptolemy describes several astronomical instruments in use during his time. These are the quadrant, the equinox ring, the noon circle, the armillary sphere, the triquetrum, and also special device to measure the angular size of the moon. Hero of Alexandria mentions another astronomical instrument - the diopter.
Gradually, the astrolabe, which in the Middle Ages became the main instrument of astronomers, is gaining popularity. The stereographic projection, which is the mathematical basis of the astrolabe, was used in the so-called "stormy weather indicator" described by Vitruvius and which is a mechanical analogue of a moving map of the starry sky. In his work On the Planisphere, Ptolemy describes the stereographic projection and notes that it is the mathematical basis for a "horoscopic instrument" that is described as the same as the astrolabe. At the end of the 4th century AD. a treatise on the astrolabe was written by Theon of Alexandria; this work has not come down to us, but its content can be restored on the basis of more works later authors. According to Synesius, Theon's daughter, the legendary Hypatia, took part in the manufacture of the astrolabes. The earliest treatises on the astrolabe that have come down to us were written by Ammonius Hermias at the end of the 5th or beginning of the 6th century and a little later by his student John Philopon.
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Mathematical apparatus of astronomy
A notable innovation of the Ptolemaic Almagest is the description of the equation of time - a function that describes the deviation of the mean solar time from the true solar time.
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Theories of motion of celestial bodies
The theory of bisection of eccentricity. The points on the circle show the positions of the planet through equal intervals time. O - center of deferent, T - Earth, E - point of equant, A - apogee of deferent, P - perigee of deferent, S - planet, C - middle planet (center of epicycle)
Although the theory of the motion of the Sun, Moon and planets has been developed since the Hellenistic period, the first theory that has come down to us is presented in Ptolemy's Almagest. The movement of all celestial bodies is presented as a combination of several movements in large and small circles (epicycles, deferents, eccentres). Ptolemy's solar theory completely coincides with the theory of Hipparchus, which we know about only from the Almagest. Significant innovations are contained in the lunar theory of Ptolemy, where for the first time a new type of unevenness in the movement of a natural satellite, evection, was taken into account and modeled. The disadvantage of this theory is the exaggeration of the interval of change in the distance from the Earth to the Moon - almost two times, which should be reflected in the change in the angular diameter of the Moon, which is not observed in reality.
The most interesting is Ptolemy's planetary theory (the theory of bisection of eccentricity): each of the planets (except Mercury) moves uniformly in a small circle (epicycle), the center of which moves in a large circle (deferent), and the Earth is displaced relative to the center of the deferent; most importantly, both the angular and linear velocity of the center of the epicycle changes when moving along the deferent, and this movement would look uniform when viewed from a certain point (equant), so that the segment connecting the Earth and the equant is divided by the center of the deferent in half. This theory made it possible to simulate with great accuracy the zodiacal inequality in the motion of the planets.
Whether Ptolemy himself was the author of the theory of the bisection of eccentricity is not known. According to Van der Waerden, who finds support in a number of recent studies, its origins should be sought in the works of scientists of an earlier time that have not come down to us.
The parameters of planetary motion along epicycles and deferents were determined from observations (although it is still unclear whether these observations were falsified). The accuracy of the Ptolemaic model is: for Saturn - about 1/2 °, Jupiter - about 10", Mars - more than 1 °, Venus and especially Mercury - up to several degrees.
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Cosmology and physics of the sky
In Ptolemy's theory, the following order of the luminaries was assumed with increasing distance from the Earth: Moon, Mercury, Venus, Sun, Mars, Jupiter, Saturn, fixed stars. At the same time, the average distance from the Earth grew with the growth of the period of revolution among the stars; still remained unresolved the problem of Mercury and Venus, in which this period is equal to the solar (Ptolemy does not give enough convincing arguments why he places these problems "below" the Sun, simply referring to the opinion of scientists of an earlier period). All stars were considered to be located on the same sphere - the sphere of fixed stars. To explain the precession, he was forced to add another sphere, which is above the sphere of the fixed stars.
Epicycle and deferent according to the theory of nested spheres.
In the theory of epicycles, including that of Ptolemy, the distance from the planets to the Earth changed. The physical picture that may be behind this theory was described by Theon of Smyrna (end of the 1st - beginning of the 2nd century AD) in the work that has come down to us Mathematical concepts useful for reading Plato. This is the theory of nested spheres, the main provisions of which are as follows. Imagine two concentric spheres made of solid material, between which a small sphere is placed. The arithmetic mean of the radii of large spheres is the radius of the deferent, and the radius of the small sphere is the radius of the epicycle. Rotating the two large spheres will cause the small sphere to rotate between them. If a planet is placed on the equator of a small sphere, then its motion will be exactly the same as in the theory of epicycles; thus the epicycle is the equator of a minor sphere.
This theory, with some modifications, was also followed by Ptolemy. It is described in his work Planetary Hypotheses. It notes, in particular, that the maximum distance to each of the planets is equal to the minimum distance to the planet following it, that is, the maximum distance to the Moon is equal to the minimum distance to Mercury, etc. Ptolemy was able to estimate the maximum distance to the Moon using the method similar to the method of Aristarchus: 64 radii of the Earth. This gave him the scale of the entire universe. As a result, it turned out that the stars are located at a distance of about 20 thousand radii of the Earth. Ptolemy also made an attempt to estimate the size of the planets. As a result of a random compensation of a number of errors, the Earth turned out to be a medium-sized body of the Universe, and the stars were approximately the same size as the Sun.
According to Ptolemy, the totality of the ethereal spheres belonging to each of the planets is a rational animated being, where the planet itself plays the role of a brain center; the impulses (emanations) emanating from it set in motion the spheres, which, in turn, carry the planet. Ptolemy gives the following analogy: the brain of a bird sends signals to its body that make the wings move, carrying the bird through the air. At the same time, Ptolemy rejects Aristotle's point of view about the Prime Mover as the reason for the motion of the planets: the celestial spheres move by their own will, and only the outermost of them is set in motion by the Prime Mover.
In late antiquity (starting from the 2nd century AD), there is a significant increase in the influence of Aristotle's physics. A number of comments were compiled on the works of Aristotle (Sosigen, II century AD, Alexander of Aphrodisias, end of II - beginning III century AD e., Simplicius, VI century). There is a revival of interest in the theory of homocentric spheres and attempts to reconcile the theory of epicycles with Aristotelian physics. At the same time, some philosophers expressed a rather critical attitude to certain postulates of Aristotle, especially to his opinion about the existence of the fifth element - ether (Xenarchus, I century AD, Proclus Diadochus, V century, John Philopon, VI century .). Proclus also owns a series criticisms to the theory of epicycles.
Views that went beyond geocentrism also developed. So, Ptolemy discusses with some scientists (without naming them by name), who assume the daily rotation of the Earth. Latin author of the 5th century. n. e. Marcianus Capella, in The Marriage of Mercury and Philology, describes a system in which the Sun revolves in a circle around the Earth, and Mercury and Venus around the Sun.
Finally, in the writings of a number of authors of that era, ideas are described that anticipated the ideas of scientists of the New Age. So, one of the participants in Plutarch's dialogue On the face visible on the disk of the Moon claims that the Moon does not fall to the Earth due to the action of centrifugal force (like objects placed in a sling), “after all, every object is carried away by its natural movement, if it is not deflected some other force aside. In the same dialogue, it is noted that gravity is characteristic not only of the Earth, but also of celestial bodies, including the Sun. The motive could be an analogy between the shape of celestial bodies and the Earth: all these objects are spherical, and since the sphericity of the Earth is associated with its own gravity, it is logical to assume that the sphericity of other bodies in the Universe is associated with the same reason.
The philosopher Seneca (1st century AD) testifies that in antiquity views were widespread, according to which the force of gravity also acts between celestial bodies. At the same time, the backward movements of the planets are only an appearance: the planets always move in the same direction, because if they stopped, they would simply fall on each other, but in reality their very movement keeps them from falling. Seneca also notes the possibility of a daily rotation of the Earth.
Pliny and Vitruvius describe a theory in which the motion of the planets is controlled Sun rays"in the form of triangles". What this means is very difficult to understand, but it is possible that the original text from which these authors borrowed their descriptions spoke of the movement of the planets under the influence of gravity and inertia.
The same Seneca expounds one of the opinions on the nature of comets, according to which comets move in very elongated orbits, being visible only when they reach the lowest point of their orbit. He also believes that comets can return, and the time between their returns is 70 years (recall that the period of revolution of the most famous of the comets, Halley's comet, is 76 years).
Macrobius (5th century AD) mentions the existence of a school of astronomers who assumed the existence of proper motions of the stars, imperceptible due to the great remoteness of the stars and the insufficient period of observation.
Another ancient Roman author, Manilius (1st century AD), cites the opinion that the Sun periodically attracts comets to itself and then makes them move away, like the planets Mercury and Venus. Manilius also testifies that at the beginning of our era the point of view was still alive that the Milky Way is a joint glow of many stars located close to each other.
Period further development astrological representations in ancient Rome
(1st–5th century AD)
In the interval between the two eras: the Hellenistic and Augustan, the ancient consciousness underwent significant changes: if the Diadochi still believed in the unpredictability of human fate, personified in Tycho, then Augustus already believed in the inevitability of fate. Thus, despite the resistance of Carneades and other opponents of astrology, astrological ideas continued to take hold of the minds of people.
Greek astrology penetrated Rome simultaneously with Greek culture: even the very fact of the expulsion of all Greek astrologers from Italy by the Roman praetor Knidos Cornelius Hispals in 139 BC, which gave them a peculiar halo of martyrdom, served more to affirm astrological views than to debunk them.
The vigorous activity of astrologers caused the appearance of numerous works in this area, which found their generalization in the study of the famous Alexandrian mathematician, geographer, astronomer and astrologer Claudius Ptolemy "Tetrabiblos" (about 150 AD). The work of Ptolemy, a representative of scientific astrology, finally secured the victory of the geocentric system of the world proposed by him over the heliocentric system discovered by Aristarchus of Samos around 270 BC.
"Tetrabiblos" contains four books: the first - "Fundamentals of Astrology", the second - "The Relationship of Stars and Peoples", the third and fourth books were called "Destiny of the Stars in Relation to Certain Persons". As one of the arguments in favor of astrology, Ptolemy put forward the pneumatological factor, according to which the knowledge of the future provided by astrology relieves a person of the affective perception of the blows of fate and leads him to an inner liberation comparable to Buddhist nirvana.
In the Tetrabiblos, Ptolemy attempted to develop the foundations of astroethnography, dating back to Babylonia, where the heavenly bodies were associated with countries and peoples. This is what Moses had in mind when explaining the prohibition of the cult of the stars to the Israelites by the fact that Yahweh, their God, gave the stars to all nations located in all parts of the world. As an example of astrogeography in Greek, we can cite a text that arose at the time of the power of Persia, in which each country was associated with a certain sign of the Zodiac, and the list opened with Aries, which rules Persia. Ptolemy used a different principle and divided the Oikoumene - the whole world known to the Greeks - into four triangles facing each other. These trigons, corresponding to the trigons of the Zodiac (four elements), include the planets, countries and peoples belonging to them. Ptolemy's attempt to develop astroethnography is not the only one: it was preceded by the studies of Hipparchus and Manilius.
Astrology has always considered the relationship of certain periods of human life with the seven planets. The seven deadly sins also corresponded to the seven planets, which was reflected in Horace: Saturn - laziness, Mars - anger, Venus - voluptuousness, Mercury - greed, Jupiter - ambitiousness, Sun - gluttony, Moon - envy.
Sun
Mars
Saturn
Mercury
Jupiter
According to Suetonius, at the birth of Octavian, a senator experienced in astrology, Nigidius Figulus, predicted a great future for the future emperor. Before the birth of her child, Livia also consulted the astrologer Scribonius regarding the fate of her son (Tiberius).
According to the chronicles of Suetonius, once Octavian Augustus and Agrippa consulted the astrologer Theogenes. Agrippa, Julia's future husband, less hesitant and more impatient than Caesar's nephew, demanded that his horoscope be taken first. Theogen announced to him amazing chances for the future. Octavian, jealous of such a happy fate, fearing that the answer regarding his own future would turn out to be less favorable, flatly refused to tell Theogenes his birthday, without knowing which it is impossible to make a horoscope. The astrologer insisted. Finally, curiosity won out and Octavian named a date. Hearing the answer of the young man, Theogen rushed to the feet of Octavian, welcoming the future emperor in him. The astrologer instantly managed to read the fate that awaited Octavian from the stars. Starting from that moment, Octavian believed in the power of astrology, and in memory of the happy influence of the sign of the Zodiac (Virgo), under which he was born, having come to power, he ordered to mint medals with the image of this sign.
However, already during the triumvirate of Octavian, Antony and Lepidus, astrologers, according to Tacitus, were expelled from Rome, and the prophetic books, Greek and Latin, were burned, as a result of which more than two thousand books perished.
Tiberius, who studied astrology in Rhodes, banned private astrological practice and expelled astrologers from Rome. At the same time, one of the astrologers, Pituanius, was thrown from the Capitol, and the other, Marcius, was punished by ancient custom behind the Esquiline Gate. This, however, did not mean that the emperors denied credit to astrology, on the contrary, they sought to use it only for their own purposes, leaving their subordinates in the dark. Nero, for example, forbade the study of philosophy under the pretext that the study of it provides a reason for predicting the future. But at the same time, the chambers of Poppea, the wife of Nero, according to Tacitus, were overflowing with astrologers who gave her advice, and one of the soothsayers attached to the house even predicted to Otto that he would become emperor after an expedition to Spain. And, indeed, why should subjects know the future, often hidden even from the ruler? Who can be sure that curiosity of this kind will not reach the point of wanting to find out the date of the emperor's death and hurry up with the conspiracy?
According to Juvenal, even astrologers, who enjoyed unlimited confidence at court, were often persecuted all the more, the more unsuccessful this or that enterprise turned out to be, the possible outcome of which was read by the stars. So, Septimius Severus took a certain Julia as his wife only because she was predicted to become the wife of the emperor; Alexander Sever also patronized astrologers and even established a department of astrology.
The fall of the cultural and moral foundations of the Romans in the last years of the Empire contributed to the growth of the prestige of astrology. After the death of Marcus Aurelius, astrologers significantly strengthened their position at the court of the emperor. And only as a result of the collapse of the entire Roman culture and the transformation of Christianity into the state religion, astrology was forced out and subjected to persecution, like other pagan cults, persecuted and destroyed by the Christian church.
Aristarchus (about 310-250 - III century BC) was born on the island of Samos. He was a student of the physicist Strato of Lampsak. His teacher belonged to the school of Aristotle and at the end of his life even led the Lyceum. He was one of the founders of the famous Library of Alexandria and Museyon - the main scientific center late antiquity. Apparently, here, among the first generation of scientists of Alexandria, Aristarchus studied and worked.
All this, however, does not explain the personality of Aristarchus, which seems to be completely falling out of his era. Before him, theories of the sky were constructed purely speculatively, on the basis of philosophical arguments. It could not be otherwise, since the sky was considered as the world of the ideal, eternal, divine. Aristarchus tried to determine the distances to celestial bodies with the help of observations. When he succeeded, he took the second step, for which neither his contemporaries nor scientists many centuries later were ready.
How Aristarchus solved the first problem is known for sure. His only surviving book, “On the Sizes of the Sun and Moon and the Distances to Them,” is devoted to this problem. First, Aristarchus determined how many times the Sun is farther than the Moon. To do this, he measured the angle between the Moon, which was in the phase of a quarter, and the Sun (this can be done at sunset or sunrise, when the Moon is sometimes visible simultaneously with it). If, according to Aristarchus, "The moon seems to us cut in half," the angle that has the Moon as its top is right. Aristarchus measured the angle between the Moon and the Sun, at the top of which was the Earth. He got it equal to 87 ° (actually 89 ° 5 2 "). In right triangle with such an angle, the hypotenuse (distance from the Earth to the Sun) is 19 times longer than the leg (distance to the Moon). For those who know trigonometry, we note that 1/19 to cos 87 °. At this conclusion - the Sun is 19 times further than the Moon - Aristarchus stopped.
In fact, the Sun is 400 times further away, but it was impossible to find the correct value with the tools of that time. Aristarchus knew that the visible disks of the Sun and the Moon are approximately the same. He himself observed solar eclipse when the disk of the Moon completely covered the disk of the Sun. But if the visible disks are equal, and the distance to the Sun is 19 times greater than the distance to the Moon, then the diameter of the Sun is 19 times the diameter of the Moon. Now the main thing remains: to compare the Sun and the Moon with the Earth itself. The pinnacle of scientific daring then was the idea that the Sun is very large, perhaps even almost as large as the whole of Greece. Observing lunar eclipses when the Moon passes through the shadow of the Earth, Aristarchus found that the diameter of the Moon is half the size of the Earth's shadow. With the help of rather ingenious reasoning, he proved that the Moon is 3 times smaller than the Earth. But the Sun is 19 times larger than the Moon, which means that its diameter is more than 6 times larger than the earth's (actually 109 times). The main thing in the work of Aristarchus was not the result, but the very fact of fulfillment, which proved that the unattainable world of celestial bodies can be known with the help of measurements and calculations.
Apparently, all this prompted Aristarchus to his great discovery. His idea has come down to us only in the retelling of Archimedes. Aristarchus guessed that big sun cannot revolve around a small Earth. Only the Moon revolves around the Earth. The sun is the center of the universe. The planets also revolve around it. This theory is called heliocentric. Aristarchus explained the change of day and night on Earth by the fact that the Earth rotates around its axis. His heliocentric model explained many things, such as the noticeable change in the brightness of Mars. Judging by some data, Aristarchus also guessed that his theory also naturally explains the loop-like motion of the planets caused by the revolution of the Earth around the Sun.
Aristarchus thought out his theories well. He took into account, in particular, the fact that an observer on a moving Earth should notice a change in the positions of the stars - a parallactic displacement. Aristarchus explained the apparent immobility of the stars by the fact that they are very far from the Earth, and its orbit is infinitely small compared to this distance. The theory of Aristarchus could not be accepted by his contemporaries. Too many things needed to be changed. It was impossible to believe that our support is not at rest, but rotates and moves, and to realize all the consequences of the fact that the Earth is also a celestial body, like Venus or Mars. Indeed, in this case, the thousand-year-old idea of Heaven, majestically gazing at the earthly world, would collapse.
Aristarchus' contemporaries rejected heliocentrism. He was accused of blasphemy and expelled from Alexandria. In a few centuries, Claudius Ptolemy will find convincing theoretical arguments refuting the motion of the Earth. It will take a change of epochs so that heliocentrism can enter the consciousness of people.
Aristarchus compares the distance to the Sun and the Moon
Plato claimed that the Sun is exactly twice as far from the Earth as the Moon. “Let's see if this is so,” thought Aristarchus and drew a triangle.
The observer looks from the Earth T to the sun and moon. The moon is in its first quarter phase. This happens when the angle TLS straight. According to Plato, TS = 2TL, so the angle TLS= 60°. But this cannot be, because during the phase of the first quarter, the Moon is separated from the Sun by about 90 °. What if it's accurate? Aristarchus tried on TLS at the time of the first quarter and received an angle of 87 °.
hipparchus
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“This Hipparchus, who cannot but deserve sufficient praise ... more than anyone has proved the relationship of man with the stars and that our souls are part of the sky ... He decided on a deed bold even for
gods - to rewrite for posterity the stars and count the luminaries ... He determined the places and the brightness of many stars, so that you can make out if they disappear, if they reappear, if they do not move, if they change in brightness.
He left heaven to his descendants as an inheritance, if there is someone who will accept this inheritance, ”the Roman historian and naturalist Pliny the Elder wrote about the greatest astronomer of Ancient Greece.
The years of Hipparchus' birth and death are unknown. It is only known that he was born in the city of Nicaea, in Asia Minor.
Hipparchus spent most of his life (1b0 - 125 BC) on the island of Rhodes in the Aegean Sea. There he built an observatory.
Of the works of Hipparchus, almost nothing has survived. Only one of his works has come down to us - "Comments on Aratus and Eudoxus." Others perished along with the Library of Alexandria. It existed for more than three centuries - from the end of the 4th century. BC e. and before
47 BC e., when the troops of Julius Caesar took Alexandria and plundered the library. In 391 AD e. a crowd of Christian fanatics burned most of the manuscripts that had miraculously survived during the invasion of the Romans. The complete destruction was completed by the Arabs. When in
641, the troops of the Caliph Omar took Alexandria, he ordered to burn all the manuscripts. Only accidentally hidden or previously transcribed manuscripts survived and later came to Baghdad.
Hipparchus was engaged in systematic observations of celestial bodies. He was the first to introduce a geographical coordinate grid of meridians and parallels, which made it possible to determine the latitude and longitude of a place on Earth in the same way that astronomers had previously determined star coordinates (declination and right ascension) on an imaginary celestial sphere.
Long-term observations of movement daylight allowed Hipparchus to verify the statements of Euctaemon (5th century BC) and Callippus (4th century BC) that the astronomical seasons have unequal duration. They begin on the day and even at the time of the equinox or solstice: spring - from the spring equinox, summer - from the summer solstice, etc.
Hipparchus found that spring lasts about 94.5 days, summer - 92.5 days, autumn - 88 days and, finally, winter lasts about 90 days. From this it followed that the Sun moves unevenly along the ecliptic - slower in summer and faster in winter. This had to be somehow reconciled with the ancient notions of perfection. celestial movements: The sun should move evenly and in a circle.
Hipparchus suggested that the Sun revolves around the Earth uniformly and in a circle, but the Earth is displaced from its center. Hipparchus called such an orbit an eccentric, and the magnitude of the displacement of the centers (in relation to the radius) - eccentricity. He found that in order to explain the different lengths of the seasons, it is necessary to take the eccentricity equal to 1/24. The point in the orbit at which the Sun is closest to the Earth was named by Hipparchus perigee, and most remote point - apogee. The line connecting perigee and apogee is called line of apses(from the Greek "apsidos" - "vault", "arch").
In 133 BC. e. in the constellation of Scorpio, a new star flared up. According to Pliny, this event prompted Hipparchus to draw up a star catalog to record changes in the sphere of the "unchanging stars". He determined the coordinates of 850 stars relative to the ecliptic - ecliptic latitude and longitude. At the same time, Hipparchus also estimated the brightness of stars using the concept he introduced magnitude
. He attributed the brightest stars to the 1st magnitude, and the weakest, barely visible, to the 6th.
Comparing his results with the coordinates of some stars measured by Aristylus and Timocharis (contemporaries of Aristarchus of Samos), Hipparchus found that the ecliptic longitudes increased equally, but the latitudes did not change. From this, he concluded that the matter was not in the movement of the stars themselves, but in a slow displacement celestial equator.
So Hipparchus discovered that celestial sphere Besides diurnal movement it still rotates very slowly around the pole of the ecliptic relative to the equator (the exact period is 26 thousand years). He called this phenomenon precession(before the equinoxes).
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Hipparchus found that the plane of the lunar orbit around the Earth is inclined to the plane of the ecliptic at an angle of 5 °. Therefore, the Moon changes not only the ecliptic latitude, but also the longitude. The lunar orbit intersects with the plane of the ecliptic at two points - nodes. Eclipses can only occur if the Moon is at these points in its orbit. Having observed several lunar eclipses during his life (they occur on a full moon), Hipparchus determined that the synodic month (the time between two full moons) lasts 29 days 12 hours 44 minutes 2.5 seconds. This value is only 0.5 s less than the true value.
Hipparchus first began to make extensive use of the ancient observations of Babylonian astronomers. This allowed him to determine the length of the year very accurately. As a result of his research, he learned to predict lunar and solar eclipses with an accuracy of one hour. Along the way, he compiled the first trigonometric table in history, in which the values \u200b\u200bof the chords corresponding to modern sines were given.
Hipparchus, the second after Aristarchus, managed to find the distance to the Moon, also estimating the distance to the Sun. He knew that during the solar eclipse of 129 BC. e. it was complete in the Hellespont region (modern Dardanelles). In Alexandria, the Moon covered only 4/5 of the solar diameter. In other words, the visible position of the Moon did not coincide in these cities by 0.1°. Knowing the distance between cities, Hipparchus easily found the distance to the Moon, using the method introduced by Thales. He calculated that the Earth-Moon distance was about 60 Earth radii (a result very close to reality). The distance Earth - Sun, according to Hipparchus, is equal to 2 thousand radii of the Earth.
Hipparchus discovered that the observed motions of the planets are very complex and cannot be described by simple geometric models. Here, for the first time, he faced a problem that he was unable to solve. Only three centuries later, the "heavenly inheritance" of the great astronomer was accepted by Ptolemy, who was able to build a system of the world consistent with observers.
Claudius Ptolemy. CREATOR OF THE THEORY OF THE SKY
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“Let no one, looking at the imperfection of our human inventions, consider the hypotheses proposed here too artificial. We must not compare the human with the divine... Celestial phenomena cannot be considered in terms of what we call simple and complex. After all, with us everything is arbitrary and variable, but with heavenly beings everything is strict and unchanging.
With these words, the last of the outstanding Greek scientists, Claudius Ptolemy, completes his astronomical treatise. They seem to sum up ancient science. They echo her achievements and disappointments. A millennium and a half - before Copernicus - they will sound in the walls medieval universities and be repeated in the works of scientists.
Claudius Ptolemy lived and worked in Alexandria, located at the mouth of the Nile. The city was founded by Alexander the Great. For three centuries it was the capital of the state, which was ruled by kings from the Ptolemaic dynasty - the successors of Alexander. In 30 BC. e. Egypt was conquered by Rome and became part of the Roman Empire.
Many outstanding scientists of antiquity lived and worked in Alexandria: mathematicians Euclid, Eratosthenes, Apollonius of Perga, astronomers Aristillus and Timocharis. In the III century. BC e. the famous Library of Alexandria was founded in the city, where all the main scientific and literary works of that era were collected - about 700 thousand papyrus scrolls. This library was constantly used by Claudius Ptolemy.
He lived in the Alexandria suburb of Canope, devoting himself entirely to science. The astronomer Ptolemy has nothing to do with the Ptolemaic dynasty, he is simply their namesake. Exact years his life is unknown, but indirect evidence suggests that he was probably born around 100 AD. e. and died around 165. But the exact dates (and even hours) of his astronomical observations, which he conducted for 15 years, are known: from 127 to 141.
Ptolemy set himself the difficult task of constructing a theory of the apparent movement of the Sun, Moon, and the five then known planets across the firmament. The accuracy of the theory should have made it possible to calculate the positions of these celestial bodies relative to the stars for many years to come, to predict the onset of solar and lunar eclipses.
To do this, it was necessary to form the basis for counting the positions of the planets - a catalog of the positions of fixed stars. Ptolemy had such a catalog at his disposal, compiled two and a half centuries before him by his outstanding predecessor, the ancient Greek astronomer Hipparchus. There were about 850 stars in this catalog.
Ptolemy built special goniometric instruments for observing the positions of stars and planets: astrolabe, armillary sphere, triquetra and some others. With their help, he made many observations and supplemented the Hipparchus star catalog, bringing the number of stars to 1022.
Using the observations of their predecessors (from astronomers Ancient Babylon to Hipparchus), and also own observations, Ptolemy built a theory of the motion of the sun, moon and planets. In this theory, it was assumed that all the luminaries move around the Earth, which is the center of the universe and has a spherical shape. To explain the complex nature of the motion of the planets, Ptolemy had to introduce a combination of two or more circular motions. In his system of the world around the Earth
great circle - deferent(from lat. deferens - “bearing”) - it is not the planet itself that moves, but the center of some other circle called epicycle(from the Greek “epi” - “above”, “kyklos” - “circle”), and the planet is already circulating along it. In fact, the movement along the epicycle is a reflection of the actual movement of the Earth around the Sun. To more accurately reproduce the uneven motion of the planets, even smaller epicycles were mounted on the epicycle.
Ptolemy managed to select such sizes and speeds of rotation of all the “wheels” of his Universe that the description of planetary movements reached high accuracy. This work required a huge mathematical intuition and a huge amount of calculations.
He was not entirely satisfied with his theory. The distance from the Earth to the Moon changed greatly (almost twice) for him, which should have led to striking changes in the angular dimensions of the star; the strong fluctuations in the brightness of Mars, etc., were not clear either. But neither he, nor even his followers, could offer a better one. All these problems seemed to Ptolemy a lesser evil than the "absurd" assumption of the Earth's motion.
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After the creation of the Almagest, Ptolemy wrote a small guide to astrology - Tetrabiblos (Quadbook), and then his second most important work - Geography. In it, he gave descriptions of all the then known countries and the coordinates (latitude and longitude) of many cities. Ptolemy's "Geography" was also translated into many languages and already in the era of printing went through more than 40 editions.
Claudius Ptolemy also wrote a monograph on optics and a book on music theory ("Harmony"). It is clear that he was a very versatile scientist.
"Almagest" and "Geography" are among the important books created throughout the history of science.
Armillary sphere.
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As a result, all objects not resting on the Earth should appear to make the same movement in the opposite direction; neither clouds nor other flying or hovering objects will ever be seen moving to the east, as the movement of the Earth to the east will always throw them ... in the opposite direction.
Choosing between the mobile and immovable Earth, Ptolemy, based on the physics of Aristotle, chose the immovable. For the same reason, he probably took and geocentric system peace.
"I know that I am mortal, I know that my days are numbered; but when in my thoughts I tirelessly and greedily follow the paths of the stars, then I do not touch the Earth with my feet: at the feast of Zeus I enjoy ambrosia, the food of the gods."
(Claudius Ptolemy. Almagest.)
In those places on Earth where the most ancient civilizations originated, many written documents have been preserved, from which it is clear that with the advent of writing, astronomy began to develop. The presence of writing allowed astronomers to more reliably preserve their observations and knowledge about the world around them. written history Astronomy originates in the III-II millennium BC. e.
At first, observational astronomy developed, which was considered as part of astrology. In order to receive more accurate information about the movements of celestial bodies, man invented the gnomon and the astronomical calendar. Beyond this, the oldest astronomical instruments include devices such as a plumb line with a movable ruler. They were sent to the Sun to determine the angular distance from the zenith.
The accumulation of observations and information about the patterns of celestial phenomena led to the development new science, and in different countries paid attention to various astronomical phenomena. People solved the same problems, described the movements of the stars. But the main thing was still the socio-economic difference, a different way of life in society. The largest states (Babylon, Egypt, China) had developed trade and state ties. Because of this, they had mutual influence in the field of science.
The state of Babylon arose on the banks of the Euphrates around the 2nd millennium BC. e. According to written sources, the Babylonians already in those days systematically observed the sky. At first, they simply recorded celestial phenomena, which they perceived as astral deities. And only in the 7th century BC. e. received rapid development Babylonian mathematical astronomy. She used unusual models and methods to describe the movement of the stars. First of all, the Babylonians singled out the Moon in the sky, then Sirius, Orion and the Pleiades. All these stars are described in clay tablets relating to the II millennium BC. e. At the same time, the official position of court astronomer appeared in Babylon. He observed and recorded the most important changes and phenomena in the sky.
By systematizing all astronomical records, the Babylonians invented the lunar calendar. A little later it was improved. The calendar had 12 synodic lunar months of 29 and 30 days equally, the year was equal to 354 days. The Babylonians also knew the solar year. In order to harmonize the lunar calendar with this year, they occasionally inserted the 13th month.
Starting from 763 BC. e. the Babylonians compiled an almost complete list of eclipses. Subsequently, these records were used by Ptolemy. Inserts in the calendar, eclipse prediction and other needs - all this required the development of mathematics. The achievements of the Babylonians in mathematics were very high. They were familiar with stereometry, long before the Greeks formulated the theorem, which is now called the Pythagorean theorem. In the IV century BC. e. invented in Babylon ecliptic system celestial coordinates. In the same place, astronomers compiled tables of lunar ephemeris, accurately showing the position of the moon.
The state of Egypt, as historians believe, existed already in the 4th millennium BC. e. The motive for the interest of the Egyptians in the study of the sky was, most likely, Agriculture, completely dependent on the floods of the Nile. The floods occurred strictly periodically, in a certain season, and the Egyptians immediately noticed their connection with the midday height of the Sun. Therefore, they began to worship the Sun as the main god Ra.
In Egypt, the power of the pharaohs was established, which simple people deified. The pharaohs established the position of court astronomer and carefully followed the development of this science, which had not only applied, but also economic and socio-political goals. In addition, priests and special officials who kept records were engaged in astronomy.
According to Egyptian myth, the sun arose from a lotus flower, which, in turn, arose from the primary watery chaos. Almost from the very beginning of the dawn of civilization, the Egyptians had a religious and mythological picture of the world, which has an astronomical basis. In their opinion, the Earth is the center of the universe, around which all the stars revolve. Mercury and Venus also revolve around the sun.
Late astronomy inherited from the Egyptians a 365-day calendar without inserts. It was used by European astronomers until the 16th century.
Astronomy as a science was also known in China. Approximately in the II-I millennium BC. e. Chinese astronomers divided the sky into 28 constellation sections, in which the Sun, Moon and planets moved. Then they singled out the Milky Way, calling it a phenomenon unknown nature. The earliest star catalog, including over 800 stars, was compiled by Gan Gong and Shi Shen around 355 BC. e. This is about a hundred years earlier than Timocharis and Aristillus in Greece. A little later, the famous Chinese astronomer Zhang Heng divided the sky into 124 constellations and recorded about 2.5 thousand visible stars.
From the III century BC. e. China used sun and water clocks. All astronomical observations were carried out from special sites-observatories.
Like other peoples of antiquity, general ideas Chinese about the universe had a mythological basis. They considered the Chinese Empire (“Celestial, or Middle, Empire”) to be the center of the world. In general, the history of the cosmogonic ideas of the ancient Chinese has come down to the present in the chronicles of the early dynasties. At this time, the doctrine of the five earthly primary elements-elements was created. These are water, fire, metal, wood, earth. The number of elements is associated with the ancient division into five cardinal points, and also corresponds to the number of moving planetary stars. Symbolically, this can be represented in combinations: water - Mercury - north, fire - Mars - south, metal - Venus - west, wood - Jupiter - east, earth - Saturn - center. In addition, there was also a sixth element - qi (air, ether).
In the VIII-VII centuries BC. e. the idea of a general change in nature and the birth of the universe itself arose. It was believed that it appeared as a result of the struggle of two opposite principles - positive, light, active, masculine (yang) and negative, dark, passive, feminine (yin).
Due to the fact that China eventually became a closed country, the development of sciences, including astronomy, slowed down.
India is of no less interest. The most ancient sources that tell about the astronomical studies of the ancient Indians are seals with images on cosmogonic mythological themes (which date back to the 3rd millennium BC). The short inscriptions contained on them have not been deciphered to this day. The seals belong to Indian civilization, the main cities of which were Harappa, Mohenjo-Daro, Kalibangan. By the 17th-16th centuries, the centers of Indian culture were significantly weakened by earthquakes and internal contradictions, and then finally destroyed by the Aryans and Indo-Iranian-speaking tribes, which gave rise to the current population of India.
There are very few documents on astronomical observations of the period of the Indian culture, but from them one can still understand how the ideas of the ancient Hindus about the Universe developed. The first objects of study were the Sun and Luke. Like other ancient peoples, priests were engaged in astronomical research, who subsequently compiled a calendar. In it since the VI century BC. e. the names of the seven moving luminaries were used in the names of the days of the seven-day week: the first day of the Moon, the second of Mars, the third of Mercury, the fourth of Jupiter, the fifth of Venus, the sixth of Saturn, the seventh of the Sun. Some similarity with the Egyptian calendar was given by the division of the month into two halves. In ancient Indian astronomy, these were the light and dark halves.
The idea of the ancient Greeks about the universe was greatly influenced by more early cultures: Egyptian, Sumero-Babylonian and, probably, ancient Indian. Greece had connections with Egypt, Babylon, with the states of the Middle East.
Many Greek philosophers and astronomers were engaged in astronomical observations. From the poems of Hesiod and Homer it is known that the ancient Greeks were familiar with many constellations. They even created their own legend about almost every one of them.
Sergei Zhitomirsky
Ancient astronomy occupies a special place in the history of science. It was in ancient Greece that the foundations of modern scientific thinking. For seven and a half centuries, from Thales and Anaximander, who took the first steps in comprehending the Universe, to Claudius Ptolemy, who created the mathematical theory of the movement of the stars, ancient scientists have come a long way, on which they had no predecessors. Astronomers of antiquity used data obtained long before them in Babylon. However, to process them, they created completely new mathematical methods, which were adopted by medieval Arab and later European astronomers.
Universe in traditional Greek mythology
How did the Greeks imagine the world in the VIII century. BC e., can be judged from the poem of the Theban poet Hesiod "Theogony" (On the origin of the gods). The story of the origin of the world he begins like this
Above all in the universe
Chaos was born, and then
Broad-breasted Gaia, universal shelter
safe ... Gaia - Earth - gave birth to herself
equal in breadth to the starry sky, Uranus, so that exactly
covered it all over.
The sky is established on a flat earth. On what, then, does the Earth itself rest? But on nothing. It turns out that under it stretches a huge empty space - Tartarus, which has become a prison for the titans defeated by the gods.
They threw them underground as deep as far to the sky, For it is so far from us
multi-gloomy Tartarus. If, taking a copper anvil,
throw it from the sky, In nine days and nights to the earth
she flew, If, taking a copper anvil,
to throw it off the ground, In nine days and nights, the weight would fly to Tartarus.
In the ideas of the ancient Greeks, the Universe was divided by the Earth into light and dark parts: the upper one was the sky, and the lower one was dominated by Erebus - underground darkness. It was believed that the sun does not look there. During the day it circles the sky in a chariot, and at night it floats in a golden bowl along the ocean surrounding the Earth to the place of sunrise. Of course, such a picture of the world was not very suitable for explaining the movements of the heavenly bodies; however, it was not intended for this.
Calendar and stars
In Ancient Greece, as in the countries of the East, the lunar- solar calendar. In it, the beginning of each calendar month was to be located as close as possible to the new moon, and average duration calendar year, if possible, correspond to the time interval between the vernal equinoxes ("tropical year", as it is called today). At the same time, months of 30 and 29 days alternated. But 12 lunar months are about a third of a month shorter than a year. Therefore, in order to fulfill the second requirement, from time to time it was necessary to resort to intercalations - to add an additional, thirteenth, month in some years.
Insertions were made irregularly by the government of each city-state. For this, special persons were appointed who monitored the magnitude of the lag of the calendar year from the solar year. In Greece, divided into small states, calendars had local meaning- there were about 400 names of months in the Greek world. The mathematician and musicologist Aristoxenus (354–300 BC) wrote about the calendar disorder: “The tenth day of the month for the Corinthians is the fifth for the Athenians and the eighth for someone else.”
Simple and precise, the 19-year cycle, used as far back as Babylon, was proposed in 433 BC. e. Athenian astronomer Meton. This cycle included the insertion of seven additional months in 19 years; his error did not exceed two hours per cycle.
Since ancient times, farmers associated with seasonal work also used the stellar calendar, which did not depend on the complex movements of the Sun and Moon. Hesiod in the poem "Works and Days", indicating to his brother Persian the time of agricultural work, notes them not according to the lunisolar calendar, but according to the stars:
Only in the east, the Pleiades Atlantis will begin to rise, Hurry up to reap, and start to enter - start sowing. Sirius is high in the sky
got up with Orion, The rose-fingered dawn is already beginning
see Arcturus, Cut, O Persian, and take home
bunches of grapes.
Thus, a good knowledge of the starry sky, which few people in the modern world can boast of, was necessary for the ancient Greeks and, obviously, widespread. Apparently, this science was taught to children in families from an early age.
The lunisolar calendar was also used in Rome. But even more "calendar arbitrariness" reigned here. The length and beginning of the year depended on the pontiffs (from Latin pontifices), Roman priests, who often used their right for selfish purposes. Such a situation could not satisfy the huge empire into which the Roman state was rapidly turning. In 46 BC. e. Julius Caesar (100-44 BC), who acted not only as the head of state, but also as the high priest, carried out a calendar reform. The new calendar, on his behalf, was developed by the Alexandrian mathematician and astronomer Sosigen, a Greek by origin. He took the Egyptian, purely solar, calendar as a basis. The refusal to take into account the lunar phases made it possible to make the calendar quite simple and accurate. This calendar, called the Julian, was used in the Christian world until its introduction in Catholic countries in the 16th century. revised Gregorian calendar. chronology according to julian calendar began in 45 BC. e. The beginning of the year has been moved to January 1 earlier first the month was March). In gratitude for the introduction of the calendar, the Senate decided to rename the month quintilis (fifth), in which Caesar was born, into Julius - our July. In 8 AD e. in honor of the next emperor, Octavian Augustus, the month sec-stylis (sixth) was renamed Augustus. When Tiberius, the third princeps (emperor), was asked by the senators to name the month of Septembre (seventh) after him, he allegedly refused, replying: "What will the thirteenth princeps do?"
The new calendar turned out to be purely civil, religious holidays, by virtue of tradition, were still celebrated in accordance with the phases of the moon. And at present, the Easter holiday is coordinated with the lunar calendar, and the cycle proposed by Meton is used to calculate its date.
Thales and the prediction of the eclipse
Thales (the end of the 7th - the middle of the 6th century BC) lived in the Greek trading city of Miletus, located in Asia Minor. Since ancient times, historians have called Thales the "father of philosophy." Unfortunately, his writings have not come down to us. It is only known that he sought to find natural causes phenomena, considered the beginning of everything water and compared the Earth with a piece of wood floating in the water.
Herodotus, talking about the war of the eastern states of Lydia and Media, reported: “So this war continued with varying success, and in the sixth year, during one battle, the day turned into night. This solar eclipse was predicted to the Ionians by Thales of Miletus and even determined in advance the year in which it would come. When the Lydians and the Medes saw that the day had turned into night, they hastily made peace.
This eclipse, according to modern calculations, occurred on May 28, 585 BC. e. To establish the frequency of eclipses, the Babylonian astrologers took more than one century. It is unlikely that Thales could have had enough data to make a prediction on his own.
Thales brought even greater benefit to astronomy as a mathematician. Apparently, he was the first to come to the idea of the need to search for mathematical proofs. For example, he proved the theorem on the equality of angles at the base of an isosceles triangle, that is, things that are obvious at first glance. It was not the result itself that was important to him, but the principle of logical construction. For astronomy, it is also very significant that Thales became the founder of the geometric study of angles.
Thales could have been the first to say, "Don't mathematician let him not enter the temple of astronomy.”
Anaximanar
Anaximander of Miletus (about 610 - after 547 BC) was a student and relative of Thales. Like his teacher, he was engaged not only in the sciences, but also in social and commercial affairs. His books "On Nature" and "Spheres" have not been preserved, and we know about their content from the retellings of those who read. The world of Anaximander is unusual. The scientist considered the heavenly bodies not as separate bodies, but as windows in opaque shells that hide the fire. The earth, according to him, looked like a part of a column, on the surface of which, flat or round, people live. She floats in the center of the world, without leaning on anything. Gigantic tubular rings-tori filled with fire surround the Earth. In the closest ring, where there is little fire, there are small holes - - planets. In the second ring with stronger fire there is one large hole - the Moon. It can partially or completely overlap (this is how the philosopher explained the change of lunar phases and eclipses of the star). There is also a giant hole the size of the Earth in the third, farthest, ring. Through it shines the strongest fire - the Sun. Perhaps Anaximander's Universe was closed by a full sphere with a scattering of holes through which the fire that surrounded it looked through. These holes people called "fixed stars". They are motionless, of course, only relative to each other. This first in the history of astronomy geocentric model of the Universe with rigid orbits of stars, covering the Earth, made it possible to understand the geometry of the movements of the Sun, Moon and stars.
Anaximander sought not only to accurately describe the world geometrically, but also to understand its origin. The philosopher considered the beginning of everything that exists apeiron - "infinite": "a certain nature of the infinite, from which the firmaments and the cosmos located in them are born." The universe, according to Anaximander, develops on its own, without the intervention of the Olympian gods.
The philosopher imagined the emergence of the Universe something like this: apeiron gives rise to warring elements - “hot” and “cold”. Their material embodiment is fire and water. The confrontation of the elements in the emerging cosmic vortex led to the appearance and separation of substances. In the center of the vortex turned out to be “cold” - the Earth, surrounded by water and air, and outside - fire. Under the action of fire, the upper layers air shell turned into a hard crust. This sphere of hardened aer (air) began to burst with vapors of the boiling earth's ocean. The shell could not stand it and swelled up, “torn off,” as one of the sources says. At the same time, she had to push the bulk of the fire beyond the boundaries of our world. This is how the sphere of fixed stars arose, and the pores in the outer shell became the stars themselves.
