Aryabhata, the Shadow, and the Temple Door

The courtyard goes quiet in the middle of the afternoon. The Sun is a crescent of itself. Someone says Rahu has taken it. Inside the temple the sanctum is shut. When the disk clears, the image will be bathed, and a household will set aside a gift. The shadow and the rite occupy the same hour.

Aryabhata states that he was twenty-three in the year that corresponds to 499, so his birth falls in 476. Later tradition places his work at Kusumapura, in the region of modern Patna. The town is less certain than the year. The book is the Aryabhatiya. In the section called Gola, the sphere, he gives the cause of an eclipse in physical terms. The Moon covers the Sun. The shadow of the Earth covers the Moon. The covering falls when the Moon is near the node: at new moon for the Sun, at full moon for the Moon.

One folk sentence, two geometries

Ordinary speech uses one demon for both events. The two events are different bodies doing different work. A solar eclipse is the Moon in front of the Sun. A lunar eclipse is the Earth standing between them, and the Moon walking into the dark cone. The crossing of the two paths is still required. Away from the node, the full moon passes above or below the shadow and the disk stays bright.

Technical books kept the old name for that crossing. Rahu is the ascending node. The other node came to be called Ketu. Varahamihira, in the next century, states a lunar eclipse as the Moon entering the Earth's shadow, and he still calls the nodes the head and the tail. Brahmagupta, writing in 628, argued with Aryabhata by name, and the eclipse was part of the argument. The shadow explanation travelled as a theorem. It did not travel as a decree that ended every other way of speaking.

The door still closes

The grahan rite sits in the religious calendar. Inscriptions that mention eclipses often record gifts made on the day. At many temples the garbhagriha stays shut while the luminary is covered, and the bath happens when the light returns. The sankalpa does not have to recite Aryabhata for the vow to be kept. A family can bathe, give, and also know which body is in front of which.

The hour of a grahan is a calculation: distance from the node, size of the shadow, how long the disk stays covered. People still ask what the eclipse means for one chart. That question is a reading, and it needs the birth time. For that, talk to an astrologer. The darkening itself is the geometry he already has the means to time.

Questions people keep asking

Did Aryabhata remove Rahu from the sky?

He gave the covering to the Moon and to the Earth's shadow. The name Rahu stayed in the astronomical books as the ascending node, the point an eclipse needs.

Why keep the grahan bath if the cause is a shadow?

The bath and the gift belong to the rite. The shadow belongs to the explanation. Temples and households have kept both, side by side, since long before printed panchangs.