Friday, August 17, 2007

Ancient Astronomy in different civilizations

Dr. Nitish Priyadarshi
For tens of thousands of years, human beings have been fascinated by the patterns of stars in the sky above Earth. Early on, they noticed that the Moon changed shape from night to night as well as its position among the stars.

Early people noticed constellations of stars in the sky that looked like animals and people, and made up stories about what they thought they saw. In fact, the oldest records we have of astronomical observations are 30,000-year-old paintings found on the walls of caves.
People from around the world study of the heavens to define themselves and to unify their cultures. The study of ancient astronomy allows us to glimpse into a time when the forces of the universe were mysterious and dangerous. Often cultures relied on shamans or priests to mediate between the people and the heavens, and so the relation between religion and astronomy in ancient times is very close.

Long before recorded history, which began about 5000 years ago, people were aware of the close relationship between events on the Earth and the positions of heavenly bodies, the Sun in particular. People noted that changes in the seasons and floods of great rivers like the Nile in the Egypt occurred when the celestial bodies, including the Sun, Moon, planets and stars, reached a particular place in the heavens. Early agrarian cultures, which were dependent on the weather, believed that if the heavenly objects could control the seasons, they must also strongly influence all Earthly events. This belief undoubtedly was the reason that early civilizations began keeping records of the positions of the celestial objects. The Chinese, Indians, Egyptians, and Babylonians in particular are noted for this.
Ancient natives of North American lined up circles of stones with the Sun and stars to chart the rising Sun and the beginning of summers.

In southern Mexico, the Mayans built special buildings to watch the Moon and the planet Venus. They had a calendar by 800 A.D. that was more accurate than the calendar used in Europe.
The Maya were quite accomplished astronomers. Their primary interest, in contrast to "western" astronomers, were Zenial Passages when the Sun crossed over the Maya latitudes. On an annual basis the sun travels to its summer solstice point, or the latitude of 23-1/3 degrees north.
Most of the Maya cities were located south of this latitude, meaning that they could observe the sun directly overhead during the time that the sun was passing over their latitude. This happened twice a year, evenly spaced around the day of solstice.
The Maya could easily determine these dates, because at local noon, they cast no shadow. Zenial passage observations are possible only in the Tropics and were quite unknown to the Spanish conquistadors who descended upon the Yucatan peninsula in the 16th century. The Maya had a god to represented this position of the Sun called the Diving God.
Ancient Egyptians were very interested in the night sky. In particular, they were drawn to two bright stars that always could be seen circling the North Pole. The Egyptians referred to those stars as "the indestructibles."

Today we know them as Kochab, in the bowl of the Little Dipper (Ursa Minor), and Mizar, in the middle of the handle of the Big Dipper (Ursa Major).

Egyptians associated those two stars with eternity and the afterlife of a king -- a pharaoh. After death, a pharaoh would hope to join those circumpolar stars. Pharaohs were buried in pyramids.
The highest development of astronomy in the ancient world came with the Greeks in the period from 600 B.C. to A.D. 400. The methods employed by the Greek astronomers were quite distinct from those of earlier civilizations, such as the Babylonian. The Babylonian approach was numerological and best suited for studying the complex lunar motions that were of overwhelming interest to the Mesopotamian peoples. The Greek approach, on the contrary, was geometric and schematic, best suited for complete cosmological models. Thales, an Ionian philosopher of the 6th cent. B.C., is credited with introducing geometrical ideas into astronomy. Pythagoras, about a hundred years later, imagined the universe as a series of concentric spheres in which each of the seven "wanderers" (the sun, the moon, and the five known planets) were embedded. Euxodus developed the idea of rotating spheres by introducing extra spheres for each of the planets to account for the observed complexities of their motions. This was the beginning of the Greek aim of providing a theory that would account for all observed phenomena. Aristotle (384–322 B.C.) summarized much of the Greek work before him and remained an absolute authority until late in the Middle Ages. Although his belief that the earth does not move retarded astronomical progress, he gave the correct explanation of lunar eclipses and a sound argument for the spherical shape of the earth.
The ancient Babylonians viewed the Universe as a flat disk of land surrounded by water. They were the first people to keep detailed records of the paths of planets. Like most ancient people, Babylonians believed that studying planetary movements could help them predict the future. In fact, according to a biblical story, the people of a Babylonian city tried to build a stairway to the stars. That was the Tower of Babel.

The Australian Aborigines felt a strong connection to nature which shaped their view of the universe and their place in it. The sun for all Aborigines was female and associated with light and goodness. This reveals that the Aborigines believed women to be intrinsically good, for they are they ones who brought human life into this world. In one myth the sun came out of the earth at a certain place, which is marked by a large stone. It came out of the earth with two other women, who were left behind while the sun rose into the sky. Every day thereafter the sun rose into the sky and at night it returns to the spot where it first arose. Another myth tells how a woman left her son in a cave while she searched for food. Since it was dark she lost her way and wandered in to the sky region. Every day she travels through the sky with her torch, lighting up the sky, looking for her son.
The Polynesians relied upon astronomy to steer their canoes while sailing around the ocean. The sun guided them during the day, but at night the boatmen watched the stars and the planets to be certain of the direction they were sailing. It was therefore necessary for this group of islanders to keep strict records of which stars rose where, and when they were visible in the night sky. The Polynesians also used astronomy for calendrical purposes. The lunar calendar was used to determine feasting or fasting days, and the solar calendar to mark the passing of days, months, and years.
Ancient Indians' interest in astronomy was an extension of their religious preoccupations and inasmuch, astronomy and mathematics ran parallel. Both were faithful to the needs of objectivity and subjectivity. Astronomy began as mere wonder at what was observed in the heavens above, grew into a systematic observation and speculation, hence forward into scientific inquiry and interpretation, finally emerging as a sophisticated discipline. Mystical interpretations of the movement of stars and planets developed into astrological science, and astronomy grew into a major factor in the intellectual pursuits of different cultural periods.
The chief sources of astronomy-related information are the Vedic texts, Jain literature, and the siddhantas (texts), as also the endeavours in Kerala (southern state of India). Some seals of the Indus Valley period are believed to yield information of the knowledge available to those early settlers, as also the orientation of certain constructions clearly governed by such considerations. An interesting aspect is the Jantar Mantar observatories built by Sawai Jai Singh of Jaipur. There are 5 such structures for measuring time and for astronomy-related calculations, at New Delhi, Varanasi, Jaipur, Mathura and Ujjain. These eighteenth century astrolabes are important for both scientific and architectural reasons.
Rig Veda and Atharva Veda hymns point to the observance of a lunar year. The Moon itself was regarded as the 'maker of months' - masakrt. Many indications are present as to the awareness of the autumn equinox - references to Aditi (this corresponds to Pollux, longitude 113degree). Daksha (Vega longitude 284degree), Rudra (Betelgeuse, longitude 88degree) and Rohini (Aedebaran, longitude 69degree). The changing longitudes mentioned are a consequence of the precession of the equinoxes. These details are useful for another reason: they reveal the date of composition. Thus, allowing for 72 years per degree (plus, allowance for error) the years should be 6200 BC, 5400 BC, 4350 BC and 3070 BC respectively. Hymn 1.164 of the Rig Veda composed by the sage Dirghatamas refers to a wheel of time with a year of 360 lunar days and twelve lunar months. The year mentioned in the hymn begins with the Autumn star Agni , corresponding to the year circa 2350 BC. (The numbering of the hymns demonstrates use of the decimal system).
Yajur Veda and Atharva Veda reveal a definite calendrical awareness - many sacrifices, including the Gavam Ayana, are of different lengths of time based on the daily cycle of the Sun. For reasons of ritual, the day was divided into 3,4,5 or 15 equal divisions, each with a different name. Apart from naming twenty seven stars beginning with Krttika, these Vedas mention five planets and name two of them - Juipter (Brihaspati) and Venus (Vena).

Regardless of the exact details of an ancient site, the exploration into the lost world of our ancestors offers many fascinating rewards. In the process of discovering the past we can see within all the peoples of the world a common bond in the creative examination of the vastness of the night sky.

Dr. Nitish Priyadarshi
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