Indian astronomy refers to the body of astronomical observation, theory, and calculation developed on the Indian subcontinent from the Vedic period through the classical and medieval periods, encompassing texts such as the Vedanga Jyotisha, the works of Aryabhata, and later siddhantic traditions including those of Brahmagupta, Varahamihira, and Bhaskara II. The field includes calendrical astronomy (used to fix the timing of rituals and festivals), positional astronomy of the sun, moon, and planets, and mathematical methods such as trigonometry and algorithms for predicting eclipses. Some aspects of its history, particularly questions of originality versus external influence and the dating of foundational texts, are subjects of ongoing scholarly discussion.

Indian astronomy is generally divided by scholars into several broad phases: an early Vedic phase concerned primarily with calendrical reckoning, exemplified by the Vedanga Jyotisha (c. mid-first millennium BCE, though the precise date is debated); a classical “siddhantic” phase beginning roughly in the early centuries CE, in which mathematical astronomy texts (siddhantas) modeled planetary motion using epicycles and trigonometric functions; and later medieval developments, including regional schools such as the Kerala school, which produced advances in infinite series and trigonometric approximations. Aryabhata's *Aryabhatiya* (499 CE) is widely regarded as a foundational siddhantic text, presenting a value for pi, trigonometric tables, a model of planetary motion, and a description of the earth's rotation on its axis. Interpretation of specific claims in the text - for instance, whether Aryabhata intended a literal heliocentric or rotating-earth model in the modern sense - remains debated among historians of science; see Aryabhata - Debate.

The relationship between Indian astronomical methods and contemporaneous Hellenistic, Babylonian, and later Islamic astronomical traditions is an area of active historical research, with scholars differing on the extent, direction, and timing of cross-cultural transmission. Fuller historical treatment is provided at indian-astronomy-history.

There is broad consensus among historians of science that Indian astronomers from the siddhantic period onward employed sophisticated mathematical techniques, including trigonometry and iterative approximation methods, independently developed or adapted alongside techniques known elsewhere in the ancient and medieval world. There is no comparable consensus on more specific and contested questions, such as the exact chronology of early Vedic-period astronomical knowledge or the degree of originality of particular models relative to external sources; these are addressed in the relevant viewpoint and debate pages below.

• Diffusionist viewpoint: holds that key elements of classical Indian astronomy, particularly epicyclic planetary models and certain numerical parameters, were substantially influenced by Hellenistic or Mesopotamian astronomical traditions transmitted via trade and cultural contact. See indian-astronomy-diffusionist-viewpoint.
• Indigenous-development viewpoint: holds that Indian astronomical traditions developed largely independently from indigenous Vedic ritual and observational practices, with external contact playing a secondary or supplementary role. See indian-astronomy-indigenous-development-viewpoint.
• Synthesis viewpoint: holds that Indian astronomy reflects an active synthesis in which imported concepts were substantially reworked, mathematically extended, and integrated with indigenous methods, making strict diffusionist/indigenous categorization of limited use. See indian-astronomy-synthesis-viewpoint.
• Nationalist-revivalist viewpoint: a position, prominent in some contemporary popular and political discourse, that asserts ancient Indian astronomical and scientific achievements were more extensive, precise, or prior to other traditions than mainstream historical scholarship holds. See indian-astronomy-nationalist-revivalist-viewpoint.

• Dispute over whether Aryabhata's description of the earth's motion constitutes an early articulation of axial rotation or a computational device without cosmological commitment. See aryabhata-earth-rotation-controversy.
• Dispute over the chronology and astronomical content of the Vedanga Jyotisha and its implications for dating other Vedic texts. See indian-astronomy-vedanga-jyotisha-dating-controversy.

• History: indian-astronomy-history
• Debate: Aryabhata - Debate
• Viewpoint Debate: indian-astronomy-diffusionist-viewpoint-debate (diffusionist vs. indigenous-development viewpoints)
• Consensus: indian-astronomy-mathematical-techniques-consensus
• Controversy: aryabhata-earth-rotation-controversy, indian-astronomy-vedanga-jyotisha-dating-controversy
• Related Main Topics: Aryabhata, Vedanga Jyotisha, History of Astronomy, Indian Mathematics

1. Kim Plofker, *Mathematics in India* (Princeton: Princeton University Press, 2009).
2. David Pingree, “History of Mathematical Astronomy in India,” in *Dictionary of Scientific Biography*, vol. 15, ed. Charles Coulston Gillispie (New York: Charles Scribner's Sons, 1978), 533-633.
3. Aryabhata, *Aryabhatiya*, trans. Walter Eugene Clark (Chicago: University of Chicago Press, 1930).
4. Yukio Ohashi, “Astronomy in Vedic Texts,” in *Encyclopaedia of the History of Science, Technology, and Medicine in Non-Western Cultures*, ed. Helaine Selin, 3rd ed. (Dordrecht: Springer, 2016).
5. Subhash Kak, “The Astronomy of the Vedic Altars,” *Vistas in Astronomy* 36, no. 2 (1993): 117-140. (cited in connection with the nationalist-revivalist viewpoint and Vedanga Jyotisha dating controversy; see relevant viewpoint/controversy pages for context on reception of this source)