From the beginning of civilization, when people began to contemplate, the stars, meteors, planets, moon, sun, and other masses in the heavens have been objects of mystery, wonder, and awe. Later in the early development of civilization, people began to study the heavens more scientifically-an important step in understanding the natural world and putting this knowledge to use. Imagine what our way of life would have been like if we were unable to see the sky due to an overcast of clouds. There would probably have been no way of telling time without the sun, nor would we have developed calendars.
The groundwork of much of our astronomical knowledge began in ancient times. The Egyptians, for example, separated a zone of heavens into thirty-six little clusters, or dekans, which by their rising characterized the start of each new ten day period. The Egyptians also obtained the knowledge of a year containing around 365.25 days, and had the knowledge for the obliquity of the Ecliptic before the Chinese in 1100 BC. They were the first group of people to adopt a year as the standard measurement of time and gave the year 365 days. They have also been given credit for the belief that the planets Venus and Mercury revolve around the sun. Observers, members of the Egyptian priesthood, were the only ones who possessed the knowledge of the subject. They performed the valuable function of fore- seeing the floods of the Nile River, which fertilized and irrigated parts of the country. Priests of Thebes claimed to be the only originators of exact astronomical study, due to the clear skies of their country. These priests determined the periods of the planets around the zones of the sky.
Some people of authority believe that the sundial and the gnomon were first introduced in Egypt. A gnomon is a vertical shaft or column erected on a horizontal plane. The measurement of the length of the shadows cast by it provide the means of the calculating angles of elevation of the sun. Portable instruments for observing transits of stars across the meridian, for orientation of monuments and probably for time measurement, certainly existed at, and perhaps before, the time of Tutankhamon (c 1355 BC).
The clepsydra, or water clock, is believed to have been invented by the astronomers of ancient Mesopotamia. The Babylonians are believed to have had this clock as early as the seventh century BC. Consisting of one container full of water with a hole in the bottom, the clesydra had a second container that collected the water, as the water level in the bottom container rose, a floater with a needle showed the time by pointing to the calculated scale.
More than four thousand years ago, the Chinese also had observed and recorded many different celestial phenomena. One of the earlier discoveries refers to the making of a sphere, to show the motions of the planets, by Yu Shih shortly after the reign of emperor Fuh Hsi around 2950 BC.
The Chinese also observed and recorded information on comets- 372 of them have been found within records between 611 BC and 1621 AD- have been used in modern times to identify comets that return to the Sun’s vicinity. Halley’s Comet was most likely observed in 240 BC and also in 467 BC. ( for an average period of about 76 years )
Chinese astronomers were aware also of the fact that the tail of a comet points away from the head in a direction that is opposite of the sun. In a collection of observations made, the Chinese astronomer Ma Tuan Lin noted, In general, in a comet east of the Sun, the tail, reckoning from the nucleus, is directed to the east , but if the comet appears to the west of the Sun, the tail is turned towards the west.
It is evident that the Hindus began to treat Astronomy as a real science around 300 AD and 1300 AD by looking at a series of works that appeared during this time period. In one of the works astonishingly accurate dimensions of the planet are given: 1600 yojans of four to about nine miles, or 7840 miles. A total amount of 51,570 yojans or 253,000 miles is given also for the distance of the Moon to the Earth.. The rules for calculating the positions of the heavenly bodies were found in some of the works, others showed knowledge of a sidereal and solar day and year.
All of this evidence indicates that from around 400 AD, the Hindus adopted the Greek system of Astronomy, their astronomers had absorbed Greek views although these views were not accepted until much later by the European society. It may accutauly be that Greek ideas were introduced much earlier , perhaps during the period of Hipparchus (c 150 BC) and Ptolemy (c 140 AD).
(624-545 BC) Thales is commonly named the founder of Greek Astronomy. From the Egytian and Mesopotamian astronomers, Thales knew the inequality in the length of the seasons, signs of the zodiac, and the length of a year. (611-547 BC) Anaximander, one of Thale’s students, introduced the sundial and the gnomon from Babylonia. Anaximander was familiar with the Obliquity of an elliptic and believed that the Earth was the shape of a cylinder. He appears to have been the very first person to theorize on the relative distances between heavenly bodies. Anaximander supposed the heavens to be sphereical in form, like the bark of a tree, enclosing the atmosphere.( Yenne, 11)
Around 130 AD the leading astronomer of the time was a man named Ptolemy. Most of our knowledge about Greek Astronomy comes from a book wrote by Ptolemy intitled Megale Syntaxis tes Astronomias. It contained the ideas and thoughts of the time period. One major idea was that of the Ptolemaic system. According to this system, the Earth is the center of the intire universe while the Sun and Moon move around the Earth and at a constant rate. Ptolemy knew that it was impossible for the orbits of the Sun and the Moon to move at a constant rate. He solved the problem by putting each planet on a little circular orbit, an epicycle. The planets rotate on the epicycle around a point called a deferent. The united motions of the planets on the epicycle and the rotation of the whole epicycle around Earth was held to clarify the irregular motion of the planets.