A Most Peculiar Coincidence
Transits of moons across the Sun aren't rare at all. Solar eclipses are something else.
August 22, 2013 - 11:00 am
370年11月2日 (2339 AD November 2 Old Style) Earth — Tourists are gathering from all the Twenty Planets today to see a natural phenomenon unique to the Earth: a total solar eclipse. The Earth and its major natural satellite, Luna, align periodically so that the system’s primary Sol is exactly blocked from view in a small region of the Earth’s surface, producing an effect known as a “diamond ring” for its similarity to a traditional ornament among the indigenous sophonts, before precisely blocking the star from view and revealing the extended stellar corona to the naked eye.
While satellite transits of a stellar primary are common to all inhabited worlds, and most known planets, the coincidence of size and orbital distance that produces the spectacular visual effect is so unusual that some religious groups on Earth point to it as evidence that the God or Gods have taken a special interest in the Earth.
A solar eclipse happens when the Moon passes between the Earth and Sun, blocking the Sun from view. Normally, this would simply be called a “transit”, and having one body transit the Sun from another is not really all that uncommon. But solar eclipses as we see them on Earth depend on a coincidence so unlikely that it’s entirely possible the Earth and Moon are the only pair of a planet and satellite in the entire Milky Way galaxy for which it happens.
It happens that the Moon’s diameter and distance are such that at least in certain parts of the Moon’s orbit around the Earth, the Moon as seen from Earth is exactly the same size as the Sun. For the part of the Earth’s surface that is on the direct line from the Sun through the Moon, the Sun is perfectly obscured, so that it’s only visible through mountain valleys around the edge of the Moon, producing an effect known as “Bailey’s Beads”.