Astronomy and Astrology have always been a part of Indian Society from time immemorial and Ancient India’s contribution in this field has been immense. The Vedas which were sacred texts comprising of a series of hymns composed over hundreds of years offer intriguing insights into how the Indian society believed that the heavens and the Gods had direct effects on people’s lives. The desire to learn about the future and the effects of the stars on their lives was a driving force and the most important factor in the advancement of astronomy as a Science. Religion was closely associated with astronomy as correct performance of religious rituals required astronomical observations. The planets have always been connected with the determination of human fortunes and hence Astronomy has always been interwoven with astrology.

__Astronomy in Vedic Times__

The Rig Veda was the earliest sacred text written around 2000BC which first mentioned astronomy. The stars, sun and comets were deified by the Vedic Aryans. Thus the earliest astronomers were generally the priests. With the help of the stars and planets, the ancient Indian astronomers developed interesting theories, read omens, created astrological charts and devised sophisticated mathematical models. Many of these theories passed into Europe and the Islamic world.

According to the Rig Veda, the year was divided into 12 months of 30 days with the total number of days in each year being 360. To ensure that the years averaged 366 days, two intercalary periods were added every five years to bring the calendar back in line with the solar year. Over the millennia Indian astronomers constantly adjusted and tweaked their calendars as the Indian calendar still migrated four days in every five years.

According to the text, they used four cardinal points to orient the altars in the correct manner. The first Vedic text to mention astronomical data was the Jyotisha Vedanga which contains events as far back as 4000 BCE although many astronomers believe that observations as early as 11000 BCE may be included. Since many of the references are couched in religious terminology, they are unclear and more research is needed in this area.

In connection with Yajnas astronomy gained great importance. It was the responsibility of the astronomer to calculate eclipses, and to foretell the time and duration of the eclipses. For certain rituals, it was necessary to know the time of the full moon, new moon, the first appearance and last disappearance of the moon etc. The list of all 27 stars or ‘Nakshatras’ is contained in the Atharva Samhita. Rig Veda mantras contain several mention of stars. It mentions Jupiter and the effects of its movement. Earlier, scientists felt that because of its distance from the Earth, it did not have any effect on its inhabitants. But our ancient sages announced that it was Jupiter or Guru which affected not only collectively but also individually and was responsible for the progress of all living beings on the earth including the good attributes of man. This has now been verified by modern scientific inventions.

Before 1500 BC Lagadacharya summarised the Vedanga Jyothisha. His summary consists of a collection of astronomical formulae. Around 4500 BC there were Vedic notices marking the beginning of the year and that of the Vernal equinox in Orion. In the third millennium cities of India, fire altars with astronomical basis have been discovered. Though their contents appear much older, their texts describing their designs are dated conservatively to the first millennium BC.

To synchronise the motions of the sun and the moon, in 1800 BC Sage Yajnavalkya is said to have advanced a 95 year cycle. He believed in the universe being heliocentric and in his book ‘Shatapatha Brahmana’, he gave the distance of the sun from the earth to be 108 times the diameter of these bodies which in modern days has been calculated as 107.5. He also gave the distance of the moon from the earth to be 108 times the diameter of these bodies which is actually 110.6, so one is awe stricken at the levels of accuracy with which the Ancient Rishis could foretell the stars.

This was followed by Surya Prajnapati a treatise by Jain astronomers in 200 BC. It contributed remarkably to astronomical facts such as celestial latitude, measurement of celestial distances, length and arc division, celestial latitude, motions of declination, obliquity of ellipse, systems of unit of time, use of shadow lengths to determine time of day etc. These developments paved the way for Siddhantic astronomy.

Many advances were made in measuring time and theories propounded on the structure of the universe. From as early as 3000 BC, vague references to the sun being the centre of the universe exist in the Vedic writings.

Astronomy has been mentioned in Upanishads like Chandogya and the epics like Ramayana and Mahabharata extensively mention the stars and their effects eg Bhishma waiting on his bed of arrows for the auspicious time of death, the various ceremonies like birth, nuptials etc conducted after consulting the family priest etc and on various other occasions implying that Astronomy was well known in those days.

As time progressed Astronomy became less spiritual and more scientific. One of the greatest discoveries of the Indian astronomers was that they recognised the sun also as a star, though it was the nearest one.

__Siddhantic astronomy__

Siddhanta astronomy was founded by Aryabhata and it focused on connecting mathematics with astrology as mathematical algorithms and formulas were required to predict astronomy accurately.

__Aryabhata__

In the Fifth century Aryabhata, the great Indian astronomer and mathematician discussed that the Sun is the source of moonlight and studied eclipses. With the help of astronomical and mathematical theories he advanced his heliocentric theory which meant that the earth spun around its own axis and considered planets and their motion with respect to the sun. This theory predated Copernicus by almost one thousand years. He propounded that day meant one sunrise to another. He calculated the oldest astronomical constant to great accuracy which gave the ratio of 1,582,237,500 rotations of the earth to 57,753,336 lunar orbits as 27.3964693572. He founded a continuous system of counting solar days. He discovered the numerical and geometrical rules for eclipse calculations. These observations were written in his two books Aryabhatiya and Arddharatrikapaksha. It is said that in the 13^{th} century his books were translated into Latin which was a profound source of inspiration to European astronomers and mathematicians. His astronomical calculations were used for fixing the Panchanga or the Hindu calendar. He was the first to propagate the theory that the earth is a sphere.

The first famous astronomical laboratory at the Nalanda University was called Khagola which is probably the reason for astronomy in India to be called Khagola Shastra. It was at this place that Aryabhata studied and expanded his knowledge on the subject.

In the 6^{th} century several Indian astronomers advanced the idea of gravity. They surmised that a special force keeps objects stuck on earth without hurling them into space and the same force also helps to keep heavenly objects in their place without them falling outwards. This was 1100 years before Newton propagated his theory of gravity.

__Brahmagupta__

Brahmagupta(598-668) was a great Indian astronomer who was the head of the astronomical observatory in Ujjain. He wrote the book Brahmasphuta Siddhanta. He estimated the circumference of the Earth to be 5000 yojanas with 1 yojana=7.2 kms. This estimate of 36000 kms is very close to the actual circumference of 40075 kms known today. He calculated rising and setting of the sun, places and motion of the various planets in the solar system, conjunctions and eclipses of the sun and the moon.

__Varahamihira__

He was an Indian astronomer and mathematician who lived in Ujjain. He wrote the Panchasiddhantika which was the first to mention that the shifting of the equinox is 50.32 seconds. The book is about mathematical astronomy and summarises five earlier treatises on astronomy. He also wrote the book Brihat Samhita covering astrology, eclipses, planetary movements, rainfall, crops and many other wide ranging subjects. He also wrote many treatises on Hindu astrology.

__Bhaskara__

Bhaskara(1114-1185) continued the mathematical tradition of Brahmagupta. He wrote the book Siddhanta Shiromani which was made up of two parts, Goladhyaya (Sphere) and Grahaganita (mathematics of the planets). He was later on the head of the astronomical observatory in Ujjain. He calculated upto 9 decimal places the time taken for the earth to orbit the sun.

__Madhava__

He was a great astronomer and mathematician who wrote a number of treatises on the positions of the moon, spherics and a number of astrological topics though unfortunately many of them are purported to be lost or damaged.

__Nilakanta__

In 15^{th} century, Nilakanta of the Kerala School of Astronomy and mathematics wrote a commentary on Aryabhata’s book and later developed his own system to make a planetary heliocentric model which was mathematically more accurate. He revised Aryabhata’s model for Mercury and Venus.

__Instruments used in Astronomy__

The oldest device called the gnomon or Sanku was used to measure time and has been mentioned in the works of Indian astronomers like Aryabhata, Varahamihira, Bhaskara and others. This is clearly mentioned in the Jain text Surya Prajnapati. It is said to be still preserved in the Manamandir observatory at Varanasi. This device has also been mentioned by the author of Grahalaghava, Ganesh Daivagna in 1522 AD in Pratoda Yantra.

**TOOL TO KEEP TRACK OF THE CONSTELLATION**

The water clock or Ghati Yantra (Clepsydra) and Star clock to determine time and seasons were also used by them.

The cross staff or the Yasti Yantra and another instrument called the Phalaka Yantra was used at the time of Bhaskara.

The armillary sphere or Gola yantra is mentioned in Aryabhata’s works.

__Observatories__

Celestial Observatory

In order to minimise errors and increase accuracy in the field of astronomy and astrology, in the 17^{th} century Sawai Jai Singh, the Maharaja of Jaipur constructed some observatories at Delhi, Ujjain, Mathura, Jaipur and Varanasi. Several huge instruments were constructed like a huge sundial or Samrat Yantra to locate the Pole star, estimate the local time and to measure the angle of celestial objects. He built the Rama Yantra to measure the altitude of celestial objects and Shanku Yantra to measure the latitude of the place and he also constructed a number of telescopes.

__Conclusion__

The greatness of Indian Astronomy lies in the fact that with the aid of crude instruments and without the help of powerful telescopes, the Indian astronomers could forecast and arrive at near perfect measurement in astronomical movements and in the prediction of eclipses. Also the desire to predict the future and acquire the knowledge of the universe and its celestial objects led to the further development of Mathematics which was another great contribution of India.

**References**

**Published On:**29-03-2014

**(Others):**

1) Wikipedia.com

2) Starteachastronomy.com

3) Crystalinks.com

4) Istina.rin.ru

5) Indicstudies.us

6) Dli.gov.in

7) Indianetzone.com

8) Explorable.com

9) Cpdarshi.wordpress.com