In 499 CE, Aryabhata wrote down what every modern textbook says about eclipses: the Moon obscures the Sun; the Earth's shadow obscures the Moon. The geometric explanation. In 628 CE — 129 years later — Brahmagupta, India's most influential mathematician of the age, called Aryabhata's explanation false and reaffirmed the eclipse demon Rahu. The geometric reading didn't become Indian astronomical mainstream until the Kerala school ~1500 CE — almost a millennium after Aryabhata got it right.