Ancient Indian Astronomy — Aryabhata, Varahamihira & Jantar Mantar

1. Vedanga Jyotisha — The Ritual Astronomy

The earliest surviving Indian astronomical text is the Vedanga Jyotisha (c. 1200–1000 BCE), one of the six Vedangas — the auxiliary sciences attached to the Vedas. Its primary purpose was not cosmological curiosity but calendrical precision: determining the correct times (muhurtas) for Vedic rituals (yajnas), especially the fire sacrifice.

The nakshatra system predates any Greek influence and shows a sophisticated understanding of the Moon's path. It became the basis of the Indian lunar calendar still used for festivals, and the 27 nakshatras are named in the Rigveda's Atharvaveda appendices and the Taittiriya Brahmana.

This tradition is calendrical astronomy — not predictive planetary computation. The transition from ritual timekeeping to systematic positional astronomy began with the siddhanta tradition from around the 4th–5th century CE.

2. The Siddhanta Tradition

A siddhanta (literally "established doctrine/conclusion") is a systematic astronomical treatise giving computational methods for calculating planetary positions, eclipses, and calendar data. The five classical siddhantas recorded by Varahamihira in his Pañcasiddhāntikā (c. 505 CE) are:

The Surya Siddhanta is the most celebrated — it gives the diameter of the Earth, the distance of the Moon, and provides heliocentric-adjacent orbital data that influenced later astronomers. It remains authoritative for traditional Hindu calendar computations today.

3. Aryabhata — The Rational Astronomer

Aryabhata I (born 476 CE, Kusumapura = Pataliputra, modern Patna; Gupta period) wrote the Aryabhatiya in 499 CE — one of the most important scientific texts in human history. He explicitly states his name, birthplace, and the year of composition — unusual in ancient Indian texts.

Major Astronomical Contributions

The Aryabhatiya has four chapters: Gitikapada (13 verses — cosmological constants), Ganitapada (33 verses — mathematics), Kalakriyapada (25 verses — time reckoning, planets), Golapada (50 verses — spherical astronomy). The text was translated into Arabic as Zij al-Arjabhar and influenced Islamic astronomy.

A second astronomer, Aryabhata II (c. 920–1000 CE), authored the Mahā-Siddhānta — he is a different person and should not be confused with Aryabhata I.

4. Varahamihira — Encyclopaedist of the Skies

Varahamihira (c. 505 CE, Ujjain, Gupta/early post-Gupta period) was court astronomer at the court of Chandragupta II's successors, working in the astronomical tradition of Ujjain — one of the two standard meridians in Indian astronomy (the other being Lanka/equator).

Varahamihira is important for two reasons in UPSC context: (1) he preserved knowledge of earlier siddhantas; (2) his Brihat Samhita is a primary source for Gupta-period culture, architecture, and natural science — and is cited in art history, water divining (dowsing), and horticulture questions.

He acknowledged Greek (Yavana) astronomical knowledge, famously stating that the Yavanas (yavanas = Greeks/foreigners) were mlechchha (foreigners) but should be honoured as rishis (sages) because of their astronomical knowledge — a remarkable statement of intellectual openness.

5. Brahmagupta and Later Medieval Astronomy

Brahmagupta (598 CE, Bhillamala/Bhinmal, Rajasthan) wrote the Brahmasphutasiddhanta (628 CE) — see also the Mathematics article. His astronomical contributions:

• Calculated the length of the solar year as 365 days, 6 hours, 5 minutes, 19 seconds
• Gave methods for computing positions of all five classical planets
• Described the Moon's distance and diameter
• Debated with Aryabhata's school on the Earth's rotation (Brahmagupta rejected it — ironic, since he was otherwise more advanced mathematically)
• His Brahmasphutasiddhanta was translated into Arabic in 773 CE as Sindhind under Caliph Al-Mansur at Baghdad — the key transmission of Indian astronomy to the Islamic world

Bhaskara II (Bhaskaracharya) (1114 CE, Bijapur; Siddhanta Shiromani): his astronomical text Siddhanta Shiromani contains Goladhyaya (spherical astronomy) — he discussed the concept of instantaneous velocity (tatkalika gati) — anticipating differential calculus concepts — and gave accurate distances for the Sun and Moon.

6. Kerala School of Astronomy and Mathematics

The Kerala School (c. 14th–16th century CE) — based around Thrissur and Thiruvananthapuram — made discoveries in astronomy and mathematics that anticipated European developments by 150–200 years. The school was founded by Madhava of Sangamagrama (c. 1340–1425 CE).

The Kerala School's geo-heliocentric model and series expansions were NOT transmitted to Europe, and European scientists (Copernicus 1543, Brahe 1588, Gregory 1671, Newton 1687) arrived at similar results independently — though the possibility of transmission via Jesuit missionaries has been debated by historians of science (George Joseph, Kim Plofker).

7. Jantar Mantar — Maharaja Jai Singh II's Observatories

Sawai Jai Singh II (1688–1743 CE), Maharaja of Jaipur, was a statesman and passionate astronomer who recognised that existing astronomical tables — both Indian and European — were inaccurate. Between 1724 and 1734 CE, he built five observatories (yantra mandira = "hall of instruments"):

Key Instruments at Jantar Mantar

• Samrat Yantra (Supreme Instrument) — a massive right-triangular sundial (gnomon); the Jaipur version is 27 m high and can give local time accurate to ±2 seconds. The gnomon's hypotenuse is parallel to Earth's axis.
• Jai Prakash Yantra — complementary hemispherical marble bowls, each representing the celestial sphere, with cross-wires to track the Sun's shadow and locate stellar positions.
• Ram Yantra — twin cylindrical structures for measuring altitude and azimuth of celestial objects.
• Misra Yantra (Delhi only) — composite instrument combining functions of five different instruments; used to determine the shortest and longest days.
• Rashivalaya Yantra (Jaipur only) — set of 12 instruments, one for each zodiac sign, to determine when the Sun enters each sign.

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