Astronomy

Indian Astronomy –

Astronomy was developed by the ancient Indians and the oldest text, ‘Vedanga Jyotish’ is estimated to be around 1200 BCE and that is associated with the study of the Vedas. This text has the details like Sun, Moon, Nakshatras (constellations), lunisolar calendar etc. Even in Ramayan and Mahabharat, there are references to cosmic events. In Hindu traditions, there is a close association of astronomy and mundane life and rituals where astronomical observation being necessitated by spatial and temporal requirements of correct performance of religious ritual. For example, there is another ancient text ‘Shulba Sutras’, dedicated to altar construction, which discusses advanced mathematics and basic astronomy. It is believed that Twenty-seven constellations, eclipses, seven planets, and twelve signs of the zodiac were also known as 1200 BCE when Vedanga Jyotish was compiled.

Ancient Indian Astronomical Instruments –

The study of celestial bodies and events was not possible with the naked eyes. Thus, the ancient Indian astronomers used various devices to study astronomy. Later on, using the same principles, Raja Sawai Jai Singh made the astronomical observatories during the medieval period. Following are some of the instruments used by ancient Indian astronomers.

1. Sanku (gnomon) – This instrument uses the shadow of a vertical rod on a horizontal plane in order to ascertain the cardinal directions, the latitude of the point of observation, and the time of observation. This instrument is mentioned in the astronomical work of Varahamihira, Aryabhata, Bhaskar and Brahmagupt etc.

2. Yasti-Yantra (Cross Staff) – This instrument has a simple stick or V-shaped staffs designed specifically for determining angles with the help of a calibrated scale. It was used in 12^th centrury during the time of Bhaskar-II.

3. Ghati-Yantra (clepsydra)- This instrument was in use till recently. This a timepiece by which time is measured by the regulated flow of liquid into (inflow type) or out from (outflow type) a vessel, and where the amount is then measured.

4. Armillary Sphere – This instrument is a model of the celestial sphere, consisting of a spherical framework of rings, centred on the Earth or the  It represents the lines of celestial longitude and latitude and other astronomically important features, such as the ecliptic. The earliest reference of this instrument can be traced back to the 5th-century work of Aryabhat. Later a detailed treatise Goldipika was dealing with globes and the armillary sphere was compiled by Parmesvara around the 14th century.

5. Phalaka-yantra – This instrument was invented by the mathematician and astronomer Bhaskara II in the 12th century. It had a rectangular board with a pin and an index arm used to determine time from the sun’s altitude.

Great Indian Astronomers –

1. Aryabhat – He was the author of Aryabhatiyaand the Aryabhaṭasiddhanta. He explicitly mentioned that the Earth was a sphere with a circumference of 39,967 km. He also described the diurnal (daily) rotation of the Earth. He also mentioned that reflected sunlight is the cause behind the shining of the Moon. He gave the idea of the day beginning at midnight.

2. Brahmgupta – He was a mathematician and astronomer of 7^th In his work Khandakhadyaka,  he reinforced the idea of the day beginning at midnight. He calculated the instantaneous motion of a planet. He defined the correct equations for parallax and the computation of eclipses. He also told that all bodies with mass are attracted to the earth.

3. Varahmihir – He was a mathematician and astronomer in 6^th He authored Panchsiddhantika drawing from several knowledge systems.

4. Lalla– He was the astronomer in 8^th He authored Siṣyadhivṛddhida dealing with planetary calculations, determination of the mean and true planets, three problems pertaining to diurnal motion of Earth, eclipses, rising and setting of the planets, the various cusps of the Moon, planetary and astral conjunctions, and complementary situations of the Sun and the Moon.

5. Bhaskar-I – He was an astronomer of the 7^th century who authored the texts like Mahabhaskariya, Laghubhaskariya, and the Aryabhatiyabhashya (a commentary on Aryabhat’s Aryabhatiya). He is credited for Planetary longitudes, heliacal rising and setting of the planets, conjunctions among the planets and stars, solar and lunar eclipses, and the phases of the Moon.

6. Bhaskar-II – He was a 12th-century astronomer and had an observatory in Ujjain (Madhya Pradesh). He authored Siddhantaśiromaṇi and Karaṇakutuhala dealing with  planetary positions, conjunctions, eclipses, cosmography, geography, mathematics, and astronomical equipment used in his observatory.