Science & Technology
Hindu astronomy, also known as Indian astronomy, is the study of celestial phenomena within the Indian subcontinent, with roots in the Vedic period (c. 1500–500 BCE). It developed a sophisticated mathematical framework, blending indigenous observations with influences from Greek and Babylonian traditions, and profoundly shaped calendars, astrology, and cosmology. Its texts, such as the Surya Siddhanta and the works of Aryabhata, introduced concepts like the Earth's rotation and the use of sine functions, centuries before similar ideas in the West.
The earliest astronomical ideas in India appear in the Vedas, particularly the Rigveda and Yajurveda, which contain hymns referencing the Sun, Moon, and stars. The Vedanga Jyotisha (c. 1400–1200 BCE) is the oldest known Indian astronomical text, providing rules for calculating the timing of sacrifices based on lunar and solar positions.1 This period also saw the development of the lunar mansions (nakshatras), a system of 27 or 28 divisions of the ecliptic used for tracking the Moon's motion. The Kalpa and Yuga time cycles, later central to cosmology, were also conceptualized during this era.
The classical period (c. 400–1200 CE) produced the Siddhantic texts, which systematized planetary theory and mathematics. The Surya Siddhanta, likely compiled around the 5th century CE, gives rules for computing planetary positions, eclipses, and the lengths of the year and month. Aryabhata's Aryabhatiya (499 CE) proposed that the Earth rotates on its axis and explained the apparent westward motion of the stars as a result of this rotation.2 His work also introduced the concept of the sine function (jya) and provided accurate approximations for π. Later astronomers like Brahmagupta and Bhaskara II refined these models, with Brahmagupta calculating the Earth's circumference and Bhaskara describing a form of the law of gravitation.
Hindu astronomers developed various instruments for observation, including the gnomon (shanku) to measure the Sun's altitude and the clepsydra (water clock) for timekeeping. The Jantar Mantar observatories built by Maharaja Jai Singh II in the 18th century, though later, reflect the continued tradition of monumental instruments. Observational data were meticulously recorded in almanacs (panchangas), which remain in use for religious and agricultural purposes. The eclipse predictions in Siddhantic texts were remarkably accurate, often within a few minutes of actual times.
Beyond the well-known texts, Hindu astronomy includes lesser-known contributions. The Kerala school of astronomy and mathematics (c. 14th–16th centuries) produced the Yuktibhasa (c. 1530), which contains proofs for infinite series expansions of trigonometric functions, predating European developments by centuries. The Āryabhaṭīya also describes a system of astronomical constants that were used to compute planetary positions with a precision that was not matched in Europe until the 16th century. Additionally, the Vākya texts, such as the Vākyakaraṇa, provided mnemonic rules for quick calculations, enabling astronomers to compute planetary positions without extensive tables. The Zīj-i Shāhī, a Persian translation of Indian astronomical tables, shows the transmission of Indian ideas to the Islamic world.3
This article is based on scholarly sources and authoritative references.
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