Indian Astronomy and the Hindu Demon of Eclipse

Rahu consumes the sun. Art by ohnios/Deviant Art

If you witnessed this week's lunar eclipse, then perhaps you did a little time traveling.

What did ancient peoples make of such a cosmic spectacle? How did they attempt to understand a lunar or solar eclipse?

One of my favorite mythological takes on the eclipse is the Hindu god Rahu -- or Phra Rahu as he's known in Thailand. He's not the oldest eclipse deity, but his story and iconography are wondrously gruesome.

Fall of an Asura

He was once a proud Asura, a demigod of immense power and hunger. Seeking immortality (for demigods are but another realm in the Wheel of Samsara), Rahu drank the divine nectar known as Amrita. Before the drought could pass his throat, however, all-powerful Vishnu decapitated him for his transgression.

(Wikimedia Commons)

The power of the nectar made his disembodied head immortal, and so this cleaved and fallen god continually seeks his revenge on the two planetary deities who ratted him out to Big Vish: the sun and moon.

As such, ravenous Rahu regularly ascends into the sky and attempts to swallow the sun or moon. But since he's disembodied, his meals fall back out again -- an escape route if you will.

In Thailand, Phra Rahu iconography sees the powerful entity sliced in half at the stomach rather than beheaded, but it still amounts to the same digestive scenario.

Rahu, Science and Religion

I know what you're wondering: How is there possible room for discussion on science here? Surely science arises and simply wipes away our tales of disembodied gods and swallowed moons.

For starters, there has always been less conflict between science and Hinduism, due in some part to distinct linguist differences between teleological and causative whys. As professor Varadaraja V. Raman, author of "Truth and Tension in Science and Religion" points out, There's the "Why do I exist?" that a biologist can answer and then there's the "Why do I exist?" that a priest answers.


Also, in today's world we increasingly see an attempt to protect set-in-stone religious stories from the ever-evolving story that science gives us. Heaven forbid new findings force us to reconsider ancient Babylonian cosmology.

We see the opposite in the sixth-century Hunduism. As scientist Rajesh Kochhar discusses in "Rahu and Ketu in mythological and 'astronomological' contexts," treatment of the disembodied Rahu actually evolved with the scientific knowledge of the time.

Two millennia ago, Indian stargazers divided the cosmos into seven geocentric planets (graha) and then set aside calamitous phenomena like meteors, comets and eclipses, classified as utpata. So on one hand you had cyclical order and on the other ominous chaos.

But of course eclipses follow a pattern as well. And in 499 CE, the great Indian mathematician-astronomer Aryabhata introduced a mathematical theory of eclipses that pretty much nailed it: just our two lunar nodes, Earth shadows and moon shadows. No demons required.

And so Rahu received something of a promotion, along with his headless body known as the entity Ketu. Instead of chaotic utpata, they were upgraded to ordered graha. While not actual planets, they took on the distinction of "shadow planets."

For a full explanation of how these two lunar nodes factor into eclipses, read "How Solar Eclipses Work" and "How Lunar Eclipses Work."

Devotion to Rahu

Who would pray to a god of darkness like Phra Rahu?

Eight Black Offerings

A lot of people, actually.

You'll find temples to the cleaved Asura throughout the Hindu world, where the devoted seek his favor in order to dodge life's many chaotic misfortunes -- our own personal utpatas.

In Thailand, devotion to Phra Rahu takes the form of eight black offerings (black rice, blackened chicken, etc.), which is also the title I gave a short horror fiction collection I wrote, thematically presented as an offering to Rahu.

What can I say? I picked up a little Phra Rahu amulet while traveling in Thailand several years ago and the entity intrigued me.

And to be honest, he's always haunted me a little.

Rahu and Unicron?

On one final note, I'd like to point out an irresistible comparison between Hindu cosmology and the "Transformers" TV show.

(Transformers Wiki)

I know, I know. Bear with me.

Just as Rahu lost his body in his quest for greatness, so too does the giant, planet-eating robot Unicron. After the 1986 Transformers movie, he was reduced to an orbiting, sentient head.

Was Unicron a take on Rahu? I can find no definitive answer, but the character was designed by Filipino illustrator Floro Dery.

I have no idea to what degree Hindu cosmology played into his imagination when he created Unicron, but I can't help but notice the similarities.

About the Author: Robert Lamb spent his childhood reading books and staring into the woods — first in Newfoundland, Canada and then in rural Tennessee. There was also a long stretch in which he was terrified of alien abduction. He earned a degree in creative writing. He taught high school and then attended journalism school. He wrote for the smallest of small-town newspapers before finally becoming a full-time science writer and podcaster. He’s currently a senior writer at HowStuffWorks and has co-hosted the science podcast Stuff to Blow Your Mind since its inception in 2010. In his spare time, he enjoys traveling with his wife Bonnie, discussing dinosaurs with his son Bastian and crafting the occasional work of fiction.