Sūrya Siddhānta
From Sūrya Siddhānta — The Sun's Treatise of the Heavens, taught by Acharya T Krishnatrey. This lesson is free to read.
Fifteen centuries ago, Indian astronomers wrote down a complete system that could predict eclipses, track the five planets, and measure the length of the year to within minutes — and they wrote it as **Sanskrit verse**, spoken (the text says) by an emissary of the **Sun** to the asura **Maya**. The **Sūrya Siddhānta** is the foundational text of Indian mathematical astronomy (jyotiṣa): fourteen chapters that give the world's earliest surviving **trigonometric sine table**, a working theory of **time**, the geometry of **eclipses**, and the statement that the **earth is a globe in space**. This course is **verse-led and covers all fourteen chapters**: every idea is taught through the original ślokas — each in Devanāgarī, with meaning, translation, and commentary — because the verses themselves are the science, compressed and carried by heart for a thousand years. <pre data-block="objectives">Recite and understand key ślokas from every part of the Sūrya Siddhānta in the original Sanskrit Translate the verses and explain the astronomy each one encodes Follow the whole arc: time, true planetary positions, the gnomon, eclipses, conjunctions, the sphere Read the world's earliest sine (jyā) table and the value R = 3438 Separate accepted science, historical debate, and traditional interpretation throughout</pre>