Lagadha

Almost nothing is known of Lagadha as a person; he survives entirely through the Vedāṅga Jyotiṣa, placed in the Vedic period, likely before 500 BCE, making it the oldest extant Indian text devoted to astronomy. Like several other Vedāṅgas — the auxiliary disciplines that support correct performance of Vedic ritual — its origin is anonymous scholarly practice more than individual authorship, with Lagadha's name attached as compiler or systematiser rather than sole inventor.

The Vedāṅga Jyotiṣa's purpose was intensely practical: Vedic yajñas (sacrifices) had to be performed at astronomically correct moments, and getting the timing wrong was considered to invalidate the ritual's efficacy. Lagadha's text systematises the lunar-solar calendar needed to fix those moments — tracking the relationship between the solar year, the lunar month, and the days on which specific rites fell due.

The text organises time into a five-year cycle (in this specialised sense, a yuga, distinct from the much longer cosmological Yugas of Puranic time-reckoning), within which it defines the ayana (solstitial half-year), ṛtu (season), and tithi (lunar day) — the basic vocabulary of Indian calendrical astronomy that every later siddhantic text would inherit and refine. Getting the sun and moon to reconcile over a five-year span, using only naked-eye observation, was a genuine computational achievement for its era.

Every later astronomer in the Indian tradition — Āryabhaṭa, Varāhamihira, Brahmagupta, Bhāskarācārya — worked within a lineage of observational astronomy whose earliest surviving textual root is Lagadha's Vedāṅga Jyotiṣa. It is not a sophisticated text by the standards of what followed it centuries later, but it is the foundation stone: the first attempt to make Vedic ritual practice answerable to a systematic, written astronomical method rather than purely local or oral convention.