"The State of The World" Number 15
Complete Index Of All Issues
What Is Unique About Earth's Sun And Moon?
Eclipses of the Sun and Moon are always reported in the news because they are beautiful and spectacular exhibitions of the nature of the heavens. But why do they happen? Moreover, what is unique about the Sun and Moon of Earth?
The diameter of the Sun is about 1,391,400 kilometers. The diameter of the Moon is about 3,476 kilometers. The Sun is therefore about 400 times greater in diameter than the Moon.
The scale illustration below shows the actual difference in diameter of the Sun and Moon - if they were viewed from the same distance.
It would be a very different world (or no world all if the Sun were much closer) if the Sun and Moon were seen as they actually are in size.
But why aren't they seen that way?
The Sun is about 149,597,887 kilometers from Earth. The Moon is about 384,403 kilometers from the Earth. The Sun is therefore about 389 times greater in distance from the Earth than the Moon.
The distance factor makes the Sun and Moon appear practically the same size when viewed from Earth i.e. the Sun is about 400 times greater in diameter, but it's also nearly 400 times more distant (never look directly at the Sun or a Solar Eclipse - permanent eye damage can happen in seconds).
The same-size visual effect enables eclipses of the Sun and Moon to happen.
Due to the geometry of the orbits of the Sun, Moon and Earth, an eclipse of the Moon can only occur when the Earth is between the Sun and the Moon i.e. at Full Moon. Eclipses of the Moon do not occur every month because the alignments, above or below the ecliptic, must also be the same in their cycles.
Also due to the same geometry of the orbits of the Sun, Moon and Earth, an eclipse of the Sun can only occur when the Moon is between the Sun and the Earth i.e. at New Moon. As with eclipses of the Moon, an eclipse of the Sun doesn't occur every month because the alignments, above or below the ecliptic, must also be precise in their cycles.