Scientific Interpretation of the story of Rahu and Ketu

The traditional explanation given in India for Solar Eclipse is based on the story of Rahu eating up the Sun. This story is often used as an example to tell us how our traditional Indian society was so superstitous. What most people do not know is that the scientific expalantion for why Solar Eclipse happens has long been known in India. In this article let us learn more about what Rahu and Ketu really are.

The traditional story of Rahu and Ketu as mentioned in the Puranas is associated with the story of Samudra Manthan. Where after the Amrita was extracted from the churning of the ocean, Vishnu took the avatar of Mohini and took the responsibility of distributing the Amrita. Mohini tricks the Asuras and starts ditributing the Amrita only to the Devas. However there was on Asura Svarbahnu who sat in the row of Devas and drank the Amrita. Realizing this Mohini severed his head with the Sudarshan Chakra. His head came to be known as Rahu and his body as Ketu. Rahu still haunts us by swallowing the sun during a solar eclipse.

Now this is just mythology related to Rahu and Ketu as mentioned in the Puranas, but if you go into the texts on Vedic astrology, then you realize what Rahu and Ketu actually are. Puranas have a lot of such stories where scientific facts have been enmeshed into interesting stories. In previous articles I have already shown you two such examples. One is the story of Dhruv and other is the story of the Yugas. Here I am presenting you the third example, which is about Rahu and Ketu

In Vedic astronomy Rahu and Ketu correspond to North Lunar Node and South Lunar Node respectively. What are these Lunar Nodes? Well, sitting on this earth we see that the sun travels from east to west in a circular path during a day. This movement is because of the rotation of earth. However, there is another motion of the Sun that our ancestors knew very well even when it is not as obvious to understand. As earth revolves around the sun, we notice the position of the sun is changing with respect to the stars. And so if you were to assume the earth to be stationary then you can picture the sun to be rotating around the earth. This plane of rotation is called the ecliptic

Now we also know that the moon revolves around the earth and that this plane of revolution of the moon is tilted at about 5.14 degrees with respect to the ecliptic plane of the apparent movement of the sun. These two planes, the ecliptic plane and plane of revolution of the moon around the earth, due to their tilt with respect to each other, overlap at two points. These two points are called the lunar nodes. Our ancient texts on Vedic astronomy mention these two nodes to be Rahu and Ketu. The ascending node where the moon moves from the south of the ecliptic to the north is the Rahu and the descending node when the moon moves from the north of the ecliptic to south is called Ketu.

The important thing to note here is that the case when moon clearly overlaps over the Sun will only happen at these two nodes, which is the cause of Solar Eclipse. This explains the story of Rahu swallowing the Sun, which was just an allegory to explain this phenomenon. Here we must keep in mind that intially Rahu and Ketu were thought of as pseudo-planets, which were part of navagrahas used in Indian astrology, which includes 7 visible objects, which were the Sun, Moon, Mars, Mercury, Jupiter, Venus and Saturn and 2 invisible objects, which were the Rahu and Ketu.

By the classical Era we see that our ancestors had a very good understanding of the Eclipses. Aryabhata in his work Gola explained the solar and lunar eclipse completely scientifically, where he mentioned that the Moons and the planets are illumined by the reflected light of the Sun and that the eclipses were caused by the shadows of one astronomical object on the other. He also provided numerical methods to make calculations about the duration of the eclipses. These methods were further perfected by subsequent Indian scholars; clearly showing that Aryabhata’s theory was widely accepted in India. These calculations were more accurate than the methods used by Europeans until the late 18 thcentury as noted by French Astronomer Guillane De Gentil in 1765.

So, after reading this article, I hope that you will see the story of Rahu and Ketu from a new perspective and understand how science and mythology have been mixed in India

Originally published at on February 8, 2020.




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Rahul Yadav

Rahul Yadav

Discover Indian Heritage: Arts, Science, Religion and Philosophy of India

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