Astronomy - Brief History of Ancient Astronomy

A Brief History of Ancient Astronomy



Nebra Sky Disc 1600 BC


Astronomy is the oldest of the natural sciences, dating back to antiquity, with its origins in the religious, mythological, cosmological, calendrical, and astrological beliefs and practices of prehistory:

The origins of Western astronomy can be found in Mesopotamia, the "land between the rivers" Tigris and Euphrates, where the ancient kingdoms of Sumer, Assyria, and Babylonia were located.



A form of writing known as cuneiform emerged among the Sumerians around 3500–3000 BC. Our knowledge of Sumerian astronomy is indirect, via the earliest Babylonian star catalogues dating from about 1200 BC.



Classical sources frequently use the term Chaldeans for the astronomers of Mesopotamia, who were, in reality, priest-scribes specializing in astrology and other forms of divination.

The first evidence of recognition that astronomical phenomena are periodic and of the application of mathematics to their prediction is Babylonian. Tablets dating back to the Old Babylonian period document the application of mathematics to the variation in the length of daylight over a solar year.

The Venus tablet of Ammi-saduqa, which lists the first and last visible risings of Venus over a period of about 21 years and is the earliest evidence that the phenomena of a planet were recognized as periodic.

A significant increase in the quality and frequency of Babylonian observations appeared during the reign of Nabonassar (747–733 BC).

The systematic records of ominous phenomena in Babylonian astronomical diaries that began at this time allowed for the discovery of a repeating 18-year cycle of lunar eclipses, for example.

The last stages in the development of Babylonian astronomy took place during the time of the Seleucid Empire (323–60 BC).

In the 3rd century BC, astronomers began to use "goal-year texts" to predict the motions of the planets.

These texts compiled records of past observations to find repeating occurrences of ominous phenomena for each planet.

About the same time, or shortly afterwards, astronomers created mathematical models that allowed them to predict these phenomena directly, without consulting past records.

Babylonian astronomy was the basis for much of what was done in Greek and Hellenistic astronomy, in classical Indian astronomy, in Iran, in Byzantium, in Syria, in Islamic astronomy, in Central Asia, and in Western Europe.

Greek Astronomy

Greek astronomy is astronomy written in the Greek language in classical antiquity. Greek astronomy is understood to include the ancient Greek, Hellenistic, Greco-Roman, and Late Antiquity eras.

It is not limited geographically to Greece or to ethnic Greeks, as the Greek language had become the language of scholarship throughout the Hellenistic world following the conquests of Alexander.

The development of astronomy by the Greek and Hellenistic astronomers is considered by historians to be a major phase in the history of astronomy.

Greek astronomy is characterized from the start by seeking a rational, physical explanation for celestial phenomena. Most of the constellations of the northern hemisphere derive from Greek astronomy, as are the names of many stars, asteroids, and planets.

The Ancient Greeks developed astronomy, which they treated as a branch of mathematics, to a highly sophisticated level. The first geometrical, three-dimensional models to explain the apparent motion of the planets were developed in the 4th century BC by Eudoxus of Cnidus and Callippus of Cyzicus. Their models were based on nested homocentric spheres centered upon the Earth. Their younger contemporary Heraclides Ponticus proposed that the Earth rotates around its axis.

The Antikythera Mechanism

An analogue computer from 150–100 BC designed to calculate the positions of astronomical objects.

A different approach to celestial phenomena was taken by natural philosophers such as Plato and Aristotle.

They were less concerned with developing mathematical predictive models than with developing an explanation of the reasons for the motions of the Cosmos.

Plato described the universe as a spherical body divided into circles carrying the planets and governed according to harmonic intervals by a world soul.

Aristotle proposed that the universe was made of a complex system of concentric spheres, whose circular motions combined to carry the planets around the earth.

Egyptian Astronomy

The precise orientation of the Egyptian pyramids affords a lasting demonstration of the high degree of technical skill in watching the heavens attained in the 3rd millennium BC. It has been shown the Pyramids were aligned towards the pole star.

Astronomy played a considerable part in Egyption religious matters for fixing the dates of festivals and determining the hours of the night.

The titles of several temple books are preserved recording the movements and phases of the sun, moon and stars.

The Astrologer's instruments (Horologium and palm) are a plumb line and sighting instrument. They have been identified with two inscribed objects in the Berlin Museum; a short handle from which a plumb line was hung, and a palm branch with a sight-slit in the broader end.

Astronomical ceiling decoration in its earliest form can be traced to the Tomb of Senenmut The tomb and the ceiling decorations date back to the 18th Dynasty of ancient Egypt (ca. 1473 B.C.).

The Celestial Diagram consisted of a northern and a southern panel which depicted circumpolar constellations in the form of discs; each divided into 24 sections suggesting a 24-hour time period, lunar cycles, and sacred deities of Egypt.

Egyptian Celestial Diagram

Indian Astronomy

Historical Jantar Mantar observatory in Jaipur, India

Astronomy in the Indian subcontinent dates back to the period of Indus Valley Civilization during 3rd millennium BC, when it was used to create calendars.

The oldest Indian astronomical text is the Vedanga Jyotisha, dating from the Vedic period. Which describes rules for tracking the motions of the Sun and the Moon for the purposes of ritual.

Aryabhata (476–550), propounded a computational system based on a planetary model in which the Earth was taken to be spinning on its axis and the periods of   the planets were given with respect to the Sun.

He accurately calculated many astronomical constants, such as the periods of the planets, times of the solar and lunar eclipses, and the instantaneous motion of the Moon.

Astronomy was advanced during the Shunga Empire and many star catalogues were produced during this time. The Shunga period is known as the "Golden age of astronomy in India".

It saw the development of calculations for the motions and places of various planets, their rising and setting, conjunctions, and the calculation of eclipses.

Indian astronomers by the 6th century believed that comets were celestial bodies that re-appeared periodically.

And by the 10th-century astronomer Bhattotpala listed the names and estimated periods of certain comets, but it is unfortunately not known how these figures were calculated or how accurate they were.

Chinese Astronomy

Su Song's star maps the oldest existent ones in print

Astronomy in China has a long history. Detailed records of astronomical observations were kept from about the 6th century BC, until the introduction of Western astronomy and the telescope in the 17th century. Chinese astronomers were able to precisely predict eclipses.

Much of early Chinese astronomy was for the purpose of timekeeping.

The Chinese used a lunisolar calendar, but because the cycles of the Sun and the Moon are different, astronomers often prepared new calendars and made observations for that purpose.

Astrological divination was also an important part of astronomy. Astronomers took careful note of "guest stars" which suddenly appeared among the fixed stars.

They were the first to record a supernova, in the Astrological Annals of the Houhanshu in 185 AD. Also, the supernova that created the Crab Nebula in 1054 is an example of a "guest star" observed by Chinese astronomers, although it was not recorded by their European contemporaries.

Maya Astronomy

El Caracol observatory temple Mexico

Maya astronomical codices (book) include detailed tables for calculating phases of the Moon, the recurrence of eclipses, and the appearance and disappearance of Venus as morning and evening star.

The Maya based their calendric in the carefully calculated cycles of the Pleiades, the Sun, the Moon, Venus, Jupiter, Saturn, Mars, and also they had a precise description of the eclipses.

A number of important Maya structures are believed to have been oriented toward the extreme risings and settings of Venus.

To the ancient Maya, Venus was the patron of war and many recorded battles are believed to have been timed to the motions of this planet.

Mars is also mentioned in preserved astronomical codices and early mythology.

Although the Maya calendar was not tied to the Sun, it has been proposed that the Maya calculated the solar year to somewhat greater accuracy than the Gregorian calendar.

Both astronomy and an intricate numerological scheme for the measurement of time were vitally important components of Maya religion

Islamic Astronomy

The Arabic and the Persian world under Islam had become highly cultured, and many important works of knowledge from Greek astronomy and Indian astronomy and Persian astronomy were translated into Arabic, used and stored in libraries throughout the area.

An important contribution by Islamic astronomers was their emphasis on observational astronomy. This led to the emergence of the first astronomical observatories in the Muslim world by the early 9th century.

In the 10th century, Abd al-Rahman al-Sufi (Azophi) carried out observations on the stars and described their positions, magnitudes, brightness, and colour and drawings for each constellation in his Book of Fixed Stars.

He also gave the first descriptions and pictures of "A Little Cloud" now known as the Andromeda Galaxy.

In the late 10th century, a huge observatory was built near Tehran, Iran, by the astronomer Abu-Mahmud al-Khujandi who observed a series of meridian transits of the Sun, which allowed him to calculate the tilt of the Earth's axis relative to the Sun.

He noted that measurements by earlier (Indian, then Greek) astronomers had found higher values for this angle, possible evidence that the axial tilt is not constant but was in fact decreasing.

Other Muslim advances in astronomy included the collection and correction of previous astronomical data. 

The invention of numerous astronomical instruments, including the development of the universal latitude-independent astrolabe

Arabic astrolabe from 1208 AD

Muhammad Mūsā believed that the heavenly bodies and celestial spheres were subject to the same physical laws as Earth.

The first elaborate experiments related to astronomical phenomena, the introduction of exacting empirical observations and experimental techniques, and the introduction of empirical testing, which produced the first model of lunar motion which matched physical observations.  

Medieval Western European Astronomy

9th century diagram of the positions of the seven planets on 18 March 816

Western Europe entered the Middle Ages with great difficulties that affected the continent's intellectual production.

The advanced astronomical treatises of classical antiquity were written in Greek, and with the decline of knowledge of that language, only simplified summaries and practical texts were available for study.

In the 6th century Bishop Gregory of Tours noted that he had learned his astronomy from reading Martianus Capella, and went on to employ this rudimentary astronomy to describe a method by which monks could determine the time of prayer at night by watching the stars.

In the 7th century the English monk Bede of Jarrow published an influential text, On the Reckoning of Time.

By the 9th century rudimentary techniques for calculating the position of the planets were circulating in Western Europe; medieval scholars recognized their flaws, but texts describing these techniques continued to be copied, reflecting an interest in the motions of the planets and in their astrological significance.

Building on this astronomical background, in the 10th century European scholars began to travel to Spain and Sicily to seek out learning which they had heard existed in the Arabic-speaking world.

There they first encountered various practical astronomical techniques concerning the calendar and timekeeping, most notably those dealing with the astrolabe.

The renaissance came to astronomy with the work of Nicolaus Copernicus, who proposed a heliocentric system, in which the planets revolved around the Sun and not the Earth.

Nicolaus Copernicus

His De revolutionibus provided a full mathematical discussion of his system, using the geometrical techniques that had been traditional in astronomy since before the time of Ptolemy. His work was later defended, expanded upon and modified by Galileo Galilei and Johannes Kepler.