Mythology of eclipse

In Hindu mythology there is a wonderful story that describes how the gods and the demons once formed an alliance to produce a nectar that could give them immortality. This is the story of the churning of the milk-ocean and the descent of Lord Visnu as the Kurma avatara, the divine tortoise. When the nectar that was churned from this ocean was being served to the gods, a demon, disguised as a god, sat between the Sun and the Moon in an attempt to procure the nectar. When he was detected by the Sun and the Moon, Lord Visnu immediately severed his head from his body. Unfortunately, it was not fast enough, for the demon had already tasted a small quantity of the nectar and had become immortal. Ever since, this demon is said to wreak vengeance on the Sun and Moon whenever they come near. The head of this great demon is known as Rahu and his tail is known as Ketu.Since then Rahu and ketu promised that they will going to trouble sun and moon from time to time to take the revenge.In Hindu astrology Rahu and Ketu are known as two invisible planets. They are enemies of the Sun and the Moon, who at certain times of the year (during conjunction or opposition) swallow the Sun or the Moon causing either a solar or a lunar eclipse.