Astronomy of ancient Greece. Astronomy in ancient Greece

In ancient times, astronomy received the greatest development among all other sciences. One reason for this was that astronomical phenomena are easier to understand than phenomena observed on the surface of the Earth. Although the ancients did not know it, then, as now, the Earth and other planets moved around the Sun in near-circular orbits at approximately constant speed, under the influence of a single force - gravity, and also rotated around their axes, in general, at constant speeds. All this is true in relation to the movement of the Moon around the Earth. As a result, the Sun, Moon, and planets appear to move in an orderly and predictable manner from Earth, and their motion can be studied with reasonable accuracy.

Another reason was that in ancient times astronomy had a practical meaning, unlike physics. We will see how astronomical knowledge was used in Chapter 6.

In Chapter 7 we look at what was, despite its inaccuracies, a triumph of Hellenistic science: the successful measurement of the sizes of the Sun, Moon, and Earth, and the distances from the Earth to the Sun and Moon. Chapter 8 is devoted to the problems of analyzing and predicting the apparent motion of planets - a problem that remained completely unresolved by astronomers in the Middle Ages and whose solution ultimately gave rise to modern science.

6. Practical benefits of astronomy {69}

Even in prehistoric times, people must have used the sky as a guide to compass, clock, and calendar. It's hard not to notice that the sun rises every morning in approximately the same direction; that you can tell whether night is coming soon by looking at how high the sun is above the horizon, and that warm weather occurs at a time of year when the days are longer.

It is known that stars began to be used for such purposes quite early. Around the 3rd millennium BC. e. The ancient Egyptians knew that the flood of the Nile, a major agricultural event, coincided with the heliacal rising of the star Sirius. This is the day of the year when Sirius first becomes visible in the rays of dawn before sunrise; in the preceding days it is not visible at all, but in subsequent days it appears in the sky earlier and earlier, long before dawn. In the VI century. BC e. Homer in his poem compares Achilles with Sirius, who can be seen high in the sky at the end of summer:

Like a star that rises in autumn with fiery rays

And, among the countless stars burning in the twilight of the night

(The sons of men call her the Dog of Orion),

It shines brightest of all, but it is a formidable sign;

She inflicts evil fire on unfortunate mortals... {70}

Later, the poet Hesiod, in the poem “Works and Days,” advised farmers to harvest grapes on the days of the heliacal rising of Arcturus; plowing should have taken place during the so-called cosmic sunset of the Pleiades star cluster. This is the name of the day of the year when this cluster first sets below the horizon in the last minutes before sunrise; before this the sun already has time to rise, when the Pleiades are still high in the sky, and after this day they set before the sun rises. After Hesiod, calendars called parapegma, which gave each day the rising and setting times of prominent stars, became widespread in the ancient Greek city-states, which had no other generally accepted way of marking days.

Observing the starry sky on dark nights, not illuminated by the lights of modern cities, the inhabitants of ancient civilizations clearly saw that, with a number of exceptions, which we will talk about later, the stars do not change their relative positions. Therefore, the constellations do not change from night to night and from year to year. But at the same time, the entire arch of these “fixed” stars rotates every night from east to west around a special point in the sky pointing exactly north, which is called the north celestial pole. In modern terms, this is the point where the Earth's axis of rotation is directed if it is extended from the Earth's north pole into the sky.

These observations made the stars useful from ancient times for sailors, who used them to determine the location of the cardinal points at night. Homer describes how Odysseus, on his way home to Ithaca, was captured by the nymph Calypso on her island in the western Mediterranean and remained captive until Zeus ordered her to release the traveler. In parting words to Odysseus, Calypso advises him to navigate by the stars:

Turning the steering wheel, he was awake; sleep did not descend on him

Eyes, and they did not move […] from the Ursa, in people there are still Chariots

The name of the one who bears and near Orion accomplishes forever

Your own circle, never bathing yourself in the waters of the ocean.

With her, the goddess of goddesses commanded him vigilantly

The path is to agree, leaving her on the left hand {71} .

Ursa is, of course, the constellation Ursa Major, also known to the ancient Greeks as the Chariot. It is located near the north pole of the world. For this reason, at the latitudes of the Mediterranean, the Big Dipper never sets (“... never bathes itself in the waters of the ocean,” as Homer put it) and is always visible at night in a more or less northern direction. Keeping the Ursa on the port side, Odysseus could constantly maintain a course east to Ithaca.

Some ancient Greek observers realized that there were more convenient landmarks among the constellations. In the biography of Alexander the Great, created by Lucius Flavius Arrian, it is mentioned that although most sailors preferred to determine the north by the Big Dipper, the Phoenicians, the real sea dogs of the Ancient world, used the constellation Ursa Minor for this purpose - not as bright as the Big Dipper, but closer located in the sky towards the celestial pole. The poet Callimachus of Cyrene, whose words are quoted by Diogenes Laertius {72} , stated that Thales came up with a way to search for the celestial pole using Ursa Minor.

The sun also makes a visible path across the sky during the day from east to west, moving around the north pole of the world. Of course, during the day the stars are usually not visible, but, apparently, Heraclitus {73} and perhaps his predecessors realized that their light was lost in the brilliance of the sun. Some stars can be seen shortly before dawn or shortly after sunset, when its position on the celestial sphere is obvious. The position of these stars changes throughout the year, and from this it is clear that the Sun is not at the same point in relation to the stars. More precisely, as was well known in ancient Babylon and India, in addition to the apparent daily rotation from east to west along with all the stars, the Sun also rotates every year in the opposite direction, from west to east, along the path known as the zodiac, by which contains the traditional zodiac constellations: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces. As we will see, the Moon and planets also move through these constellations, although not along the same paths. The path that the Sun makes through them is called ecliptic .

Having understood what the zodiac constellations are, it is easy to determine where the Sun is now among the stars. You just need to look at which of the zodiac constellations is visible highest in the sky at midnight; The sun will be in the constellation opposite this one. It is said that Thales calculated that one complete revolution of the Sun through the zodiac takes 365 days.

An observer from Earth may believe that the stars are located on a solid sphere surrounding the Earth, whose celestial pole is located above the Earth's north pole. But the zodiac does not coincide with the equator of this sphere. Anaximander is credited with the discovery that the zodiac lies at an angle of 23.5° with respect to the celestial equator, with the constellations Cancer and Gemini being closest to the north celestial pole, and Capricorn and Sagittarius furthest from it. We now know that this tilt, which causes the change of seasons, exists because the Earth's axis of rotation is not perpendicular to the plane of the Earth's orbit around the Sun, which, in turn, coincides quite accurately with the plane in which almost all bodies in the solar system move. The deviation of the earth's axis from the perpendicular is an angle of 23.5°. When it is summer in the Northern Hemisphere, the sun is in the direction where the Earth's north pole is tilted, and when it is winter, it is in the opposite direction.

Astronomy as an exact science began with the use of a device known as a gnomon, with which it became possible to measure the apparent movement of the sun across the sky. Bishop Eusebius of Caesarea in the 4th century. wrote that the gnomon was invented by Anaximander, but Herodotus attributed the credit for its creation to the Babylonians. It is just a rod mounted vertically on a flat area illuminated by the sun. With the help of the gnomon, you can accurately tell when noon occurs - at this moment the sun is highest in the sky, so the gnomon casts the shortest shadow. Any place on earth north of the tropics at noon, the sun is located exactly south, which means that the shadow of the gnomon points at that moment exactly north. Knowing this, it is easy to mark the area according to the shadow of the gnomon, marking it with directions to all cardinal directions, and it will serve as a compass. The gnomon can also work as a calendar. In spring and summer, the sun rises slightly north of the east point on the horizon, and in autumn and winter – south of it. When the shadow of the gnomon at dawn points exactly to the west, the sun rises exactly in the east, which means today is the day of one of two equinoxes: either the spring, when winter gives way to spring, or the autumn, when summer ends and autumn comes. On the day of the summer solstice, the shadow of the gnomon at noon is the shortest, on the day of the winter - accordingly, the longest. A sundial is similar to a gnomon, but is constructed differently - its rod is parallel to the Earth's axis, not a vertical line, and the shadow from the rod points in the same direction at the same time every day. Therefore, a sundial is, in fact, a clock, but it cannot be used as a calendar.

The gnomon is a great example of the important connection between science and technology: a technical device invented for a practical purpose that makes it possible to make scientific discoveries. With the help of the gnomon, an accurate count of days in each of the seasons became available - the period of time from one equinox to the solstice and then until the next equinox. Thus, Euctemon, a contemporary of Socrates who lived in Athens, discovered that the lengths of the seasons do not coincide exactly. This was unexpected if we assume that the Sun moves around the Earth (or the Earth around the Sun) in a regular circle with the Earth (or the Sun) at the center at a constant speed. Based on this assumption, all seasons should be exactly the same length. For centuries, astronomers tried to understand the reason for their actual inequality, but the correct explanation for this and other anomalies appeared only in the 17th century, when Johannes Kepler realized that the Earth revolves around the Sun in an orbit that is not a circle, but an ellipse, and the Sun is not located in its center, but shifted to a point called focus. At the same time, the Earth's movement either accelerates or slows down as it approaches or moves away from the Sun.

For an earthly observer, the Moon also rotates along with the starry sky every night from east to west around the north pole of the world and, like the Sun, slowly moves along the zodiacal circle from west to east, but its full rotation in relation to the stars is “in the background” which it occurs takes a little more than 27 days, and not a year. Since for the observer the Sun moves across the zodiac in the same direction as the Moon, but more slowly, about 29.5 days pass between the moments when the Moon is in the same position in relation to the Sun (actually 29 days 12 hours 44 minutes and 3 seconds). Since the phases of the Moon depend on the relative position of the Sun and the Moon, it is this interval of 29.5 days that is the lunar month {74} , that is, the time that passes from one new moon to another. It has long been noted that lunar eclipses occur during the full moon phase and their cycle repeats every 18 years, when the visible path of the Moon against the background of stars intersects with the path of the Sun {75} .

In some ways, the Moon is more suitable for the calendar than the Sun. By observing the phase of the moon on any given night, you can tell approximately how many days have passed since the last new moon, and this is a much more accurate way than trying to determine the time of year simply by looking at the sun. Therefore, lunar calendars were very common in the Ancient world and are still used today - for example, this is the Islamic religious calendar. But, of course, in order to make plans in agriculture, navigation or military affairs, one must be able to predict the change of seasons, and it occurs under the influence of the Sun. Unfortunately, there is not a whole number of lunar months in a year - a year is about 11 days longer than 12 full lunar months, and for this reason the date of any solstice or equinox cannot remain the same in a calendar based on the changing phases of the Moon.

Another well-known difficulty is that the year itself does not take up an entire number of days. During the time of Julius Caesar, it was customary to consider every fourth year a leap year. But this did not solve the problem completely, since the year does not last exactly 365 days and a quarter, but 11 minutes longer.

History remembers countless attempts to create a calendar that would take into account all these difficulties - there were so many of them that there is no point in talking about them all here. A fundamental contribution to the solution of this issue was made in 432 BC. e. the Athenian Meton, who may have been a colleague of Euctemon. Using probably the Babylonian astronomical chronicles, Meton determined that 19 years corresponded exactly to 235 lunar months. The error is only 2 hours. Therefore, it is possible to create a calendar, but not for one year, but for 19 years, in which both the time of year and the phase of the Moon will be precisely defined for each day. The days of the calendar will repeat every 19 years. But since 19 years are almost exactly equal to 235 lunar months, this interval is a third of a day shorter than exactly 6940 days, and for this reason Meton prescribed that every few 19-year cycles one day should be removed from the calendar.

The efforts of astronomers to harmonize the solar and lunar calendars are well illustrated by the definition of Easter. The Council of Nicaea in 325 declared that Easter should be celebrated every year on the Sunday after the first full moon following the spring equinox. During the reign of Emperor Theodosius I the Great, it was established by law that celebrating Easter on the wrong day was strictly punishable. Unfortunately, the exact date of observation of the vernal equinox is not always the same at different points on the earth {76} . In order to avoid the terrible consequences of someone somewhere celebrating Easter on the wrong day, it became necessary to designate one of the days as the exact day of the vernal equinox, as well as agree on exactly when the next full moon occurs. The Roman Catholic Church in late antiquity began to use the Metonic cycle for this, while the monastic orders of Ireland adopted the earlier Jewish 84-year cycle as a basis. Erupted in the 17th century. The struggle between the missionaries of Rome and the monks of Ireland for control of the English Church was largely provoked by a dispute over the exact date of Easter.

Before the advent of modern times, the creation of calendars was one of the main activities of astronomers. As a result, in 1582, the calendar generally accepted today was created and, under the patronage of Pope Gregory XIII, put into use. To determine the day of Easter, it is now considered that the vernal equinox always occurs on March 21, but it is only March 21 according to the Gregorian calendar in the Western world and the same day, but according to the Julian calendar, in countries professing Orthodoxy. As a result, Easter is celebrated on different days in different parts of the world.

Although astronomy was a useful science already in the Classical Age of Greece, it made no impression on Plato. In the dialogue “The Republic” there is a passage in the conversation between Socrates and his opponent Glaucon that illustrates his point of view. Socrates argues that astronomy should be a compulsory subject to be taught to future philosopher kings. Glaucon easily agrees with him: “In my opinion, yes, because careful observations of the changing seasons, months and years are suitable not only for agriculture and navigation, but no less for directing military operations.” However, Socrates declares this point of view naive. For him, the meaning of astronomy is that “... in these sciences, a certain instrument of the soul of every person is cleansed and revived, which other activities destroy and make blind, and yet keeping it intact is more valuable than having a thousand eyes, because only with with his help you can see the truth" {77} . Such intellectual arrogance was less characteristic of the Alexandrian school than of the Athenian school, but even in the works of, for example, the philosopher Philo of Alexandria in the first century. it is noted that “what is perceived by the mind is always higher than everything that is perceived and seen by the senses” {78} . Fortunately, although under the pressure of practical necessity, astronomers gradually weaned themselves from relying on their own intellect alone.

Another reason was that in ancient times astronomy had a practical meaning, unlike physics. We will see how astronomical knowledge was used in Chapter 6.

6. Practical benefits of astronomy

Like a star that rises in autumn with fiery rays

And, among the countless stars burning in the twilight of the night

(The sons of men call her the Dog of Orion),

It shines brightest of all, but it is a formidable sign;

She inflicts evil fire on unfortunate mortals...

Later, the poet Hesiod, in the poem “Works and Days,” advised farmers to harvest grapes on the days of the heliacal rising of Arcturus; plowing should have taken place during the so-called cosmic sunset of the Pleiades star cluster. This is the name of the day of the year when this cluster first sets below the horizon in the last minutes before sunrise; before this the sun already has time to rise, when the Pleiades are still high in the sky, and after this day they set before the sun rises. After Hesiod, calendars called parapegma, which gave the rising and setting times of prominent stars for each day, became widespread in the ancient Greek city-states, which had no other generally accepted way of marking days.

Turning the steering wheel, he was awake; sleep did not descend on him

Eyes, and they did not move […] from the Ursa, in people there are still Chariots

The name of the one who bears and near Orion accomplishes forever

Your own circle, never bathing yourself in the waters of the ocean.

With her, the goddess of goddesses commanded him vigilantly

The path is to agree, leaving her on the left hand.

Some ancient Greek observers realized that there were more convenient landmarks among the constellations. In the biography of Alexander the Great, created by Lucius Flavius Arrian, it is mentioned that although most sailors preferred to determine the north by the Big Dipper, the Phoenicians, the real sea dogs of the Ancient world, used the constellation Ursa Minor for this purpose - not as bright as the Big Dipper, but closer located in the sky towards the celestial pole. The poet Callimachus from Cyrene, whose words are quoted by Diogenes Laertius, stated that Thales came up with a way to look for the celestial pole using Ursa Minor.

The sun also makes a visible path across the sky during the day from east to west, moving around the north pole of the world. Of course, during the day the stars are usually not visible, but, apparently, Heraclitus, perhaps his predecessors, realized that their light was lost in the radiance of the sun. Some stars can be seen shortly before dawn or shortly after sunset, when its position on the celestial sphere is obvious. The position of these stars changes throughout the year, and from this it is clear that the Sun is not at the same point in relation to the stars. More precisely, as was well known in ancient Babylon and India, in addition to the apparent daily rotation from east to west along with all the stars, the Sun also rotates every year in the opposite direction, from west to east, along the path known as the zodiac, by which contains the traditional zodiac constellations: Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces. As we will see, the Moon and planets also move through these constellations, although not along the same paths. The path that the Sun makes through them is called ecliptic .

For an earthly observer, the Moon also rotates along with the starry sky every night from east to west around the north pole of the world and, like the Sun, slowly moves along the zodiacal circle from west to east, but its full rotation in relation to the stars is “in the background” which it occurs takes a little more than 27 days, and not a year. Since for the observer the Sun moves across the zodiac in the same direction as the Moon, but more slowly, about 29.5 days pass between the moments when the Moon is in the same position in relation to the Sun (actually 29 days 12 hours 44 minutes and 3 seconds). Since the phases of the Moon depend on the relative position of the Sun and the Moon, it is this interval of 29.5 days that is the lunar month, that is, the time that passes from one new moon to the next. It has long been noted that lunar eclipses occur during the full moon phase and their cycle repeats every 18 years, when the visible path of the Moon against the background of stars intersects with the path of the Sun.

The efforts of astronomers to harmonize the solar and lunar calendars are well illustrated by the definition of Easter. The Council of Nicaea in 325 declared that Easter should be celebrated every year on the Sunday after the first full moon following the spring equinox. During the reign of Emperor Theodosius I the Great, it was established by law that celebrating Easter on the wrong day was strictly punishable. Unfortunately, the exact date of observation of the vernal equinox is not always the same at different points on the earth. In order to avoid the terrible consequences of someone somewhere celebrating Easter on the wrong day, it became necessary to designate one of the days as the exact day of the vernal equinox, as well as agree on exactly when the next full moon occurs. The Roman Catholic Church in late antiquity began to use the Metonic cycle for this, while the monastic orders of Ireland adopted the earlier Jewish 84-year cycle as a basis. Erupted in the 17th century. the struggle between the missionaries of Rome and the monks of Ireland for control of the English Church was largely provoked by a dispute over the exact date of Easter.

Although astronomy was a useful science already in the Classical Age of Greece, it made no impression on Plato. In the dialogue “The Republic” there is a passage in the conversation between Socrates and his opponent Glaucon that illustrates his point of view. Socrates argues that astronomy should be a compulsory subject to be taught to future philosopher kings. Glaucon easily agrees with him: “In my opinion, yes, because careful observations of the changing seasons, months and years are suitable not only for agriculture and navigation, but no less for directing military operations.” However, Socrates declares this point of view naive. For him, the meaning of astronomy is that “... in these sciences, a certain instrument of the soul of every person is cleansed and revived, which other activities destroy and make blind, and yet keeping it intact is more valuable than having a thousand eyes, because only with with his help one can see the truth.” Such intellectual arrogance was less characteristic of the Alexandrian school than of the Athenian school, but even in the works of, for example, the philosopher Philo of Alexandria in the first century. It is noted that “what is perceived by the mind is always higher than everything that is perceived and seen by the senses.” Fortunately, although under the pressure of practical necessity, astronomers gradually weaned themselves from relying on their own intellect alone.

The history of astronomy differs from the history of other natural sciences primarily
its special antiquity. In the distant past, when out of practical skills,
accumulated in everyday life and activities has not yet formed
no systematic knowledge of physics and chemistry, astronomy was already
highly developed science.
Throughout all these centuries the doctrine of the stars has been an essential part
philosophical and religious worldview, which was a reflection
public life. The history of astronomy was the development of that idea
which humanity has made up its mind about the world.

Astronomy in Ancient China
The oldest period of development of Chinese civilization dates back to the times of the Shang and Zhou kingdoms.
The needs of everyday life, the development of agriculture, and crafts prompted the ancient Chinese
study natural phenomena and accumulate primary scientific knowledge. Such knowledge, in particular,
mathematical and astronomical, already existed in the Shang (Yin) period. About it
This is evidenced by both literary monuments and inscriptions on bones. The legends included in “Shu”
Jing,” they say that already in ancient times the division of the year into
four seasons. Through constant observations, Chinese astronomers have established that the picture
The starry sky, if observed from day to day at the same time of day, changes. They
noticed a pattern in the appearance of certain stars and constellations in the firmament and
the time of onset of one or another agricultural
season of the year. In 104 BC. e. an extensive conference was convened in China
conference of astronomers dedicated to improving
the calendar system "Zhuan-xu" in force at that time
whether. After a lively discussion at the conference there was
the official calendar system “Taichu Li” was adopted,
named after Emperor Tai Chu.

Astronomy in Ancient Egypt
Egyptian astronomy was created by the need to calculate the periods of the Nile flood. Year
was calculated by the star Sirius, whose morning appearance after
temporary invisibility coincided with the annual offensive
flood. The great achievement of the ancient Egyptians was the compilation of a fairly accurate calendar. The year consisted of 3 seasons, each
season - 4 months, each month - 30 days (three decades of 10
days). 5 additional days were added to the last month, which
made it possible to combine the calendar and astronomical year (365
days). The beginning of the year coincided with the rise of water in the Nile, that is, with
July 19, the day of the rise of the brightest star - Sirius. The day was divided into 24 hours, although the hour was not the same as it is now,
and fluctuated depending on the time of year (in summer, daytime
the hours were long, the night hours were short, and in winter it was the other way around).
The Egyptians thoroughly studied the starry sky visible to the naked eye,
they distinguished between fixed stars and wandering planets.
The stars were united into constellations and received the names of those animals whose contours, according to the priests, they resembled (“bull”,
“scorpion”, “crocodile”, etc.).

Astronomy in Ancient India
Information on astronomy can be found in the Vedic literature, which has a religious and philosophical direction, related to
II–I millennium BC It contains, in particular, information about
solar eclipses, intercalations using the thirteenth
months, list of nakshatras - lunar stations; finally,
cosmogonic hymns dedicated to the Earth goddess, glorification
The suns, the personification of time as initial power, also have
a certain attitude towards astronomy. Information about the planets
are mentioned in those sections of Vedic literature that
dedicated to astrology. The seven Adityas mentioned in the Rig Veda can be
interpreted as the Sun, Moon and five planets known in ancient times -
Mars, Mercury, Jupiter, Venus, Saturn. Unlike the Babylonian
and ancient Chinese astronomers, Indian scientists have practically no
were interested in studying stars as such and did not compose
star catalogues. Their interest in the stars is mainly
focused on those constellations that lay on the ecliptic or
near her. By choosing suitable stars and constellations they were able
obtain a star system to indicate the path of the Sun and Moon. This
the system among Indians was called the “nakshatra system”,
among the Chinese – “xiu systems”, among the Arabs – “systems
manazili". The following information on Indian astronomy
date back to the first centuries AD.

Astronomy in Ancient Greece
Astronomical knowledge accumulated in Egypt and Babylon was borrowed
ancient Greeks. In the VI century. BC e. Greek philosopher Heraclitus said
the idea that the Universe has always been, is and will be, that there is nothing in it
unchangeable - everything moves, changes, develops. At the end of the 6th century. BC e.
Pythagoras first suggested that the Earth has the shape
ball. Later, in the 4th century. BC e. Aristotle with the help of witty
considerations proved the sphericity of the Earth. Lived in the 3rd century. BC e.
Aristarchus of Samos believed that the Earth revolves around the Sun.
He determined the distance from the Earth to the Sun to be 600 Earth diameters (20
times less than actual). However, Aristarchus considered this distance
insignificant compared to the distance from the Earth to the stars. At the end of the 4th century. before
n. e. after the campaigns and conquests of Alexander the Great, Greek
culture penetrated all countries of the Middle East. Originated in Egypt
the city of Alexandria became the largest cultural center. In the II century. BC e.
the great Alexandrian astronomer Hipparchus, using already accumulated
observations, compiled a catalog of more than 1000 stars with fairly accurate
determining their position in the sky. In the II century. BC e. Alexandrian
the astronomer Ptolemy put forward his system of the world, later called
geocentric: the stationary Earth was located in the center
Universe.

Astronomy in Ancient Babylon
Babylonian culture - one of the oldest cultures on the globe - dates back to IV
millennium BC e. The most ancient centers of this culture were the cities of Sumer and Akkad, as well as Elam,
has long been associated with Mesopotamia. Babylonian culture had a great influence on the development of ancient peoples
Western Asia and the ancient world. One of the most significant achievements of the Sumerian people was
the invention of writing, which appeared in the middle of the 4th millennium BC. It was writing that allowed
establish a connection not only between contemporaries, but even between people of different generations, as well as
pass on to posterity the most important cultural achievements. The significant development of astronomy is evidenced by the data
recording the moments of rising, setting and culmination of various stars, as well as the ability to calculate intervals
time separating them. In the VIII–VI centuries. Babylonian priests and astronomers accumulated a large amount of knowledge,
had an idea about the procession (preceding the equinoxes) and even predicted eclipses. Some
observations and knowledge in the field of astronomy made it possible to construct a special calendar, partly based on
lunar phases. The main calendar units of time were the day, lunar month and year. Day
were divided into three guards of the night and three guards of the day. At the same time, the day was divided into 12 hours, and the hour - into 30
minutes, which corresponds to the six-base number system that was the basis of Babylonian mathematics,
astronomy and calendar. Obviously, the calendar reflected the desire to divide the day, year and circle into 12
large and 360 small parts.

Who is Aristarchus of Samos? What is he famous for? You will find answers to these and other questions in the article. Aristarchus of Samos is an ancient Greek astronomer. He is a philosopher and mathematician of the 3rd century BC. e. Aristarchus developed the scientific technology for finding the distances to the Moon and the Sun and their sizes, and also for the first time proposed a heliocentric world system.

Biography

What is the biography of Aristarchus of Samos? There is very little information about his life, like about most other astronomers of antiquity. It is known that he was born on the exact years of his life are unknown. In the literature, the period is usually indicated as 310 BC. e. - 230 BC e., which is established on the basis of indirect information.

Ptolemy claimed that Aristarchus in 280 BC. e. watched the solstice. This evidence is the only authoritative date in the astronomer’s biography. Aristarchus studied with the outstanding philosopher, a representative of the Peripatetic school, Strato of Lampascus. Historians suggest that for a long time Aristarchus worked in the Hellenistic scientific center in Alexandria.

When the heliocentric theory was put forward by Aristarchus of Samos, he was accused of atheism. Nobody knows what this accusation led to.

Constructions of Aristarchus

What discoveries did Aristarchus of Samos make? Archimedes, in his work “Psammit,” provides brief information about the astronomical system of Aristarchus, which was set out in a work that has not reached us. Like Ptolemy, Aristarchus believed that the movements of the planets, the Moon and the Earth, occur within the sphere of fixed stars, which, according to Aristarchus, is motionless, like the Sun, located in its center.

He argued that the Earth moves in a circle, in the middle of which the Sun is located. The constructions of Aristarchus are the highest achievement of the heliocentric doctrine. It was their courage that brought the author to the accusation of apostasy, as we discussed above, and he was forced to leave Athens. The only small work of the great astronomer, “On the Distances of the Sun,” has survived, which was published for the first time in Oxford in the original language in 1688.

World order

Why are the views of Aristarchus of Samos interesting? When they study the history of the development of humanity’s views on the structure of the Universe and the place of the Earth in this structure, they always remember the name of this ancient Greek scientist. Like Aristotle, he preferred the spherical structure of the universe. However, unlike Aristotle, he did not place the Earth at the center of universal circular motion (like Aristotle), but the Sun.

In the light of current knowledge about the world, we can say that among the ancient Greek researchers, Aristarchus came closest to the real picture of the organization of the world. Nevertheless, the structure of the world he proposed did not become popular in the scientific community of that time.

Heliocentric world design

What is the heliocentric construction of the world (heliocentrism)? that the Sun is the celestial central body around which the earth and other planets revolve. It is the opposite of the geocentric construction of the world. Heliocentrism appeared in antiquity, but became popular only in the 16th-17th centuries.

In the heliocentric design, the Earth is represented as rotating around its own axis (a revolution takes one sidereal day) and at the same time around the Sun (a revolution takes one sidereal year). The result of the first movement is the visible revolution of the celestial sphere, the result of the second is the annual movement of the Sun along the ecliptic among the stars. Relative to the stars, the Sun is considered motionless.

Geocentrism is the belief that the center of the universe is the Earth. This world construct was the dominant theory throughout Europe, Ancient Greece and elsewhere for centuries. In the 16th century, the heliocentric world design began to gain prominence as industry developed to gain more arguments in its favor. The priority of Aristarchus in its creation was recognized by the Copernicans Kepler and Galileo.

“On the distances and magnitudes of the Moon and the Sun”

So, you already know that Aristarchus of Samos believed that the center of the Universe was the Sun. Let's consider his famous essay “On the distances and magnitudes of the Moon and the Sun,” in which he tries to establish the distance to these celestial bodies and their parameters. Ancient Greek scholars spoke on these topics more than once. Thus, Anaxagoras of Klazomen argued that the Sun is larger in parameters than the Peloponnese.

But all these judgments were not scientifically substantiated: the parameters of the Moon and the Sun and distances were not calculated on the basis of any observations by astronomers, but were simply invented. But Aristarchus of Samos used a scientific method based on the observation of lunar and solar eclipses and lunar phases.

His formulations are based on the hypothesis that the Moon receives light from the Sun and looks like a ball. From which it follows that if the Moon is placed in quadrature, that is, cut in half, then the angle Sun - Moon - Earth is straight.

Now the angle between the Sun and the Moon α is measured and, by “solving” the right triangle, the ratio of the distances from the Moon to the Earth can be established. According to Aristarchus' measurements, α = 87°. As a result, it turns out that the Sun is almost 19 times farther than the Moon. In ancient times, there were no trigonometric functions. Therefore, to calculate this distance, he used very intricate calculations, described in detail in the work we are considering.

Next, Aristarchus of Samos drew on some data about solar eclipses. He clearly imagined that they happen when the Moon blocks the Sun from us. Therefore, he indicated that the angular parameters of these luminaries in the sky are approximately identical. It follows from this that the Sun is as many times larger than the Moon as it is farther away, that is (according to Aristarchus) the ratio of the radii of the Moon and the Sun is approximately 20.

Then Aristarchus tried to measure the ratio of the parameters of the Moon and the Sun to the size of the Earth. This time he drew on the analysis of lunar eclipses. He knew that they occur when the Moon is in the cone of the Earth's shadow. He determined that in the zone the width of this cone is twice the diameter of the Moon. Aristarchus further concluded that the ratio of the radii of the Earth and the Sun is less than 43 to 6, but greater than 19 to 3. He also estimated the radius of the Moon: it is almost three times less than the Earth's radius, which is almost identical to the correct value (0.273 radii Earth).

The scientist underestimated the distance to the Sun by approximately 20 times. In general, his method was quite imperfect and unstable to errors. But this was the only method available in ancient times. Also, contrary to the title of his work, Aristarchus does not calculate the distance from the Sun to the Moon, although he could easily do this if he knew their linear and angular parameters.

The work of Aristarchus is of great historical significance: it was from him that astronomers began studying the “third coordinate”, during which the scale of the Universe, the Milky Way and the Solar system were revealed.

Calendar improvements

You already know the years of life of Aristarchus of Samos. He was a great man. Thus, Aristarchus influenced the updating of the calendar. Censorinus (a writer of the 3rd century AD) indicated that Aristarchus established the length of the year at 365 days.

In addition, the great scientist introduced a calendar span of 2434 years. Many historians argue that this period was a derivative of a several times larger cycle of 4868 years, which is called the “Great Year of Aristarchus.”

In the Vatican lists, Aristarchus is chronologically the first astronomer for whom two different values for the length of the year were created. These two types of year (sidereal and tropical) are not equal to each other due to the precession of the earth's axis, in accordance with the traditional opinion discovered by Hipparchus a century and a half after Aristarchus.

If Rawlins' reconstruction of the Vatican lists is correct, then the distinction between the sidereal and tropical years was first determined by Aristarchus, who should be considered the discoverer of precession.

Other works

It is known that Aristarchus is the creator of trigonometry. According to Vitruvius, he modernized the sundial (he also invented a flat sundial). In addition, Aristarchus studied optics. He thought that the color of objects appears when light falls on them, that is, that paints have no color in the dark.

Many believe that he conducted experiments to identify the resolving susceptibility of the human eye.

Meaning and memory

Contemporaries understood that the works of Aristarchus were of outstanding importance. His name has always been mentioned among the famous mathematicians of Hellas. The work “On the Distances and Magnitudes of the Moon and the Sun,” written by his student or by him, was included in the mandatory list of works that novice astronomers had to study in Ancient Greece. His works were widely quoted by Archimedes, whom everyone considered the brilliant scientist of Hellas (in the surviving works of Archimedes, the name of Aristarchus appears more often than the name of any other scientist).

An asteroid (3999, Aristarchus), a lunar crater, and an air hub on his homeland, the island of Samos, were named in honor of Aristarchus.

In ancient times there was no science. Priests watched over all celestial bodies. But the great thinkers of Ancient Greece were the first to engage in scientific research of the Universe. They created the basis for the further development of the science of astronomy.

Astronomers of ancient and modern times

Aristotle

Aristotle was born in 384 BC. in Estagir and died in 322 BC. in Chalcedonia. He studied philosophy, botany, zoology, psychology, medicine, physics and astronomy. Aristotle was sure that the Earth is the center of the universe, being a motionless sphere. The rest of the planets, stars, the Sun and the Moon constantly revolve around our planet. Aristotle tried to prove this proposition using philosophical reasoning. He was confident in his theory to explore the Universe.

Aristotle wrote a philosophical treatise called “On the Heavens,” which dealt with the planets and stars. Since modern knowledge in the field of mathematics did not exist in Ancient Greece, there were no modern tools for astronomical calculations, and given the authority of the scientist, no one could object to Aristotle.

Aristotle's statements and reasoning regarding astronomy were considered infallible for 2000 years.

Hipparchus of Nicaea

Very little is known about this scientist. Hipparchus of Nicaea lived in the 2nd century. BC. It is he who has the right to be considered the founder of scientific astronomy. Hipparchus made important calculations regarding the movements of the Moon and the Sun. He managed to quite accurately describe the orbit of the Earth's satellite.

Hipparchus also created a star catalogue, which described more than 1000 stars. In this catalog, the founder of scientific astronomy divided stars into six classes by brightness. This method is still used by astronomers today.

Eratosthenes

Eratosthenes was born in Cyrene in 275 BC, and died in Alexandria in 193 BC. He was not only an astronomer, but a geographer and philosopher. Eratosthenes also left his mark in mathematics. he has the right to be the inventor of a device with which it was possible to find the locations of villages and cities, the distance to which was known in advance. It is also known that Eratosthenes was in charge of the Library of Alexandria.

One of the most important achievements of Eratosthenes is that he managed to determine the circumference of the Earth. During his research, the astronomer discovered that on the day of the summer solstice (June 21), the Sun is reflected in the wells of the city of Aswan, and in Alexandria (which was located to the north, but practically on the same meridian) objects cast a small shadow. Eratosthenes suggested that this phenomenon could be due to the curvature of the Earth's surface. By measuring the distance between two cities, the astronomer was able to determine the radius of the Earth.

Claudius Ptolemy

Ptolemy was a philosopher, mathematician and astronomer. He was born and lived in Alexandria in the 2nd century. BC. In his monumental work, called "Sintaxis matematica", Ptolemy collected all astronomical knowledge. This work had 13 volumes.

Ptolemy compiled astronomical tables and created a work on cartography, which became a good help in drawing up the most accurate maps for those times. The astronomer also managed to compile a star catalog, which included about 1200 stars.

Ptolemy created a planetary geocentric system, which he described in five books. His astronomical ideas were unquestioned for thirteen centuries. Just like Aristotle, Ptolemy considered the Earth to be the center of the Universe, around which are the Moon, planets and the Sun, rotating according to their orbits. Ptolemy imagined the earth as a sphere.

Nicolaus Copernicus

Nicolaus Copernicus - Polish astronomer. He was born on February 19, 1473 in Toruń and died in Frombork on May 24, 1543. He had the opportunity to study at the universities of Krakow, Bologna and Padua, where Copernicus studied various sciences, including astronomy. In 1512 he became a canon of Frombork, devoting himself to his duties as well as to astronomical observations and exploration of the universe. He created a hydraulic system that could provide water supply.

Copernicus very carefully studied and analyzed all the astronomical theories known at that time, conducting a comparative analysis with the latest data at that time. From all this painstaking work, the scientist concluded that the Earth is not the center of the Universe. Copernicus wrote a treatise in which he outlined his heliocentric theory. His work was banned by the church, but it still saw the light shortly before the astronomer’s death.

According to Copernicus, the Sun is the center of the Universe, and the other planets (including the Earth) revolve around it.

Johannes Kepler

Johannes Kepler was a German astronomer born in Weil der Stadt. This happened on December 27, 1571. He died on November 15, 1630. Kepler created a new model of telescope that made it possible to improve the study of the solar system. Johann also made mathematical calculations of the trajectories of the planets, which made it possible to discover the laws governing their movement.

According to Kepler's laws, all planets move in elliptical orbits. The Sun is located at one of the foci of these orbits. Depending on the distance from the Sun, the speed of the planet’s orbit decreases or increases. To formulate his laws, Kepler studied the orbit of Mars for 10 years.

Galileo Galilei

“But still she spins!” - Galileo Galilei

Galileo is a famous Italian mathematician, physicist and astronomer. He was born on February 15, 1564 in Pisa and died on January 8, 1642 in Florence. He discovered the laws of motion of the pendulum, created hydraulic scales and invented the gas thermometer. In 1609, Galileo managed to create a telescope of an improved design, which gave a thirteen-fold magnification. With its help, the scientist observed celestial bodies and explored the Universe.

Galileo discovered spots on the Sun, calculated the rotation period of this star and concluded that the stars were located very far from our planet. He is the author of the statement that the Universe is infinite.

Galileo was a zealous adherent of the Copernican theory, which caused a conflict between Galileo and the church. Galileo was put on trial and, in a desperate situation, he was forced to publicly renounce his beliefs. This happened in 1632. While under house arrest, Galileo continued his work with his students, although he was half blind.

An astronomer managed to prove that the Milky Way is not a cloud. He proved that this is a mass of stars, discovered mountains on the Earth's satellite (on the Moon) and discovered four satellites of Jupiter.

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