Astronomy in India | Class 11 Knowledge Traditions Practices of India Notes

Explanation of Eclipses

Eclipses are significant astronomical phenomena that have fascinated humans for millennia. Ancient Indian astronomers sought to understand these events scientifically. They realized that the moon does not emit its own light but shines by reflecting the sun's light. Accurate knowledge of the distances between the Earth, moon, and sun was essential to explain eclipses.

A solar eclipse occurs when the moon comes between the Earth and the sun, blocking the sun's light from reaching parts of the Earth. Observers in these shadowed regions see a partial or total obscuration of the sun. Conversely, a lunar eclipse happens when the Earth comes between the sun and the moon, casting its shadow on the moon and causing it to darken.

It is important to note that during eclipses, the sun continues to emit its usual radiation; no special rays are emitted. However, looking directly at the sun during a solar eclipse can harm the eyes, so precautions are necessary.

Ancient astronomers observed that eclipses only occur on full moon or new moon days. They explained this by understanding that the orbital planes of the Earth and the moon are inclined relative to each other. The two planes intersect along a line called the line of nodes, with two points known as nodes. Eclipses can only occur when the moon is near one of these nodes, aligning the sun, moon, and Earth in a straight line.

These nodes were mythologized as Rahu and Ketu, two demons who periodically 'devour' the sun or moon, causing eclipses. This myth persists in some cultural beliefs, leading to rituals such as charity and blowing conches during eclipses to ward off evil.

Scientifically, the period of an eclipse is considered inauspicious because the absence of sunlight can promote the growth of germs. People observe fasts and discard perishable foods during this time to avoid harm.

Thus, Indian astronomy provided a rational explanation for eclipses, dispelling myths and enabling predictions of these celestial events.

📊 Diagram: See figure_9: Intersection of the orbital planes of the moon and the sun showing the line of nodes and two nodes; figure_10: Illustration showing that eclipses occur only when Earth, moon, and sun lie in the same plane.

🔗 Connection: This section connects to the next topic on the apparent movement of the sun and its relation to seasons, including Uttarāyaṇa and Dakṣiṇāyana.