Grahaṇa-Gaṇita: Eclipse Science
Learn how Indian astronomers computed eclipses with remarkable precision: in the 1760s the French astronomer Le Gentil recorded a Tamil almanac-maker computing the length of a lunar eclipse to within about 41 seconds. Explore the mathematics of shadows and the refinement of methods over centuries.
Lessons in this chapter
- Rāhu-Ketu: From Mythology to Mathematics — How a swallowing demon became two computed points, and an eclipse became a shadow
- Sūrya-Grahaṇa: Calculating Solar Eclipses — Why a solar eclipse is a local event, and the parallax correction that pins it to a place
- Candra-Grahaṇa: Calculating Lunar Eclipses — Entering the Earth's own shadow, and forecasting the very colour the Moon will turn
- Chāyā-Gaṇita: Shadow Calculations — How a vertical stick and its shadow gave the astronomer the time, the latitude, and the size of the world
- Grahaṇa-Kāla: Timing Eclipse Events — Computing the exact minute an eclipse begins, peaks, and ends, and staking a reputation on the clock
- Varāhamihira-Paddhati: Varāhamihira's Eclipse Methods — The astronomer who weighed five rival schools, chose the best, and declared Rāhu was not the cause
- Śuddhi-Paramparā: How Accuracy Improved Over Centuries — The unbroken lineage of correction, and how ancient eclipse records became a tool to weigh the Earth's slowing spin