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What Happens When an Eclipse Occurs?

An eclipse occurs when one astronomical body moves in front of another, obscuring it from view. Eclipses of the sun and moon have been observed for millennia. They occur regularly, and their timing can be predicted by astronomers. Historically, many cultures have seen eclipses as significant events, signalling moments of great importance or revealing portents of danger.

Solar Eclipses
- A solar eclipse occurs when the moon moves between the sun and the Earth, casting a shadow over the Earth. Although the moon is much smaller than the sun, it is much closer to Earth, allowing it to partly or even completely block out the sun. Solar eclipses can occur up to five times per year, but this is relatively rare. There were five eclipses in 1935, and the phenomenon will not recur until 2206.
Lunar Eclipse
- An eclipse of the moon, or lunar eclipse, occurs when the Earth comes between the sun and the moon, casting the surface of the moon into shadow. The moon moves gradually into the umbra, or shadow cast by the Earth, so the eclipse appears as a shadow creeping across the face of the moon. Even when the moon is completely within the Earth's umbra, some sunlight, scattered by Earth's atmosphere, does strike it, making it partly visible. At these times, the moon appears to have a red hue.
Total and Partial Eclipses
- Most eclipses are partial eclipses, meaning the sun or moon is only partially obscured by shadow. In the case of solar eclipses, a total eclipse can only be seen from a relatively small area on Earth. Observers outside of the main shadow, or umbra, of the moon will see only a partial eclipse. Lunar eclipses are observable from anywhere on Earth's night side. Similarly, solar eclipses are very brief, lasting no more than 8 minutes, the time it takes the moon to move across the face of the sun. Lunar eclipses can last for several hours.
Beliefs Regarding Eclipses
- Historically, many cultures around the world considered the movement of the heavens to be a supernatural or divine process. Eclipses were therefore seen as highly significant events. They were often considered to be supernatural warnings or portents. The red of the moon during a lunar eclipse was associated with blood and thought to foretell bloodshed and war. Some ancient cultures successfully predicted eclipses, and ancient Indian astronomers developed accurate theories explaining the causes of eclipses.

Astronomy