A reminder that there is no inherent reason that the apparent size of the moon happens to be the same as the sun creating perfectly aligned solar eclipses (except when it isn't, in the case of annular eclipses).
But how much of a coincidence is it? According to some random person's calculations on Quora:
"Given all the assumptions made let us say the probability of earth having a moon that would cause a total eclipse is between 1% and 4%."
@alan I was wondering though. The moon size is a close match, but do I understand correctly, that if it was a perfect size match it would be less exciting? Less exciting because it would mean the shadow is zero miles wide instead of 100 miles wide (much harder to see), and even in that perfectly aligned path we would experience totality for just an instant instead of about four minutes.
@harry_wood Due to the elliptical nature of the moon's orbit we do get some variation in terms of how much of the sun is covered by the moon. This is called the Magnitude of the eclipse.
And this varies even over the course of each eclipse. There are some "hybrid" eclipses that begin as annular eclipses then become total as the shadow moves across the earth.
@harry_wood So in a hybrid eclipse, if you were standing at the transition point (where the eclipse magnitude is exactly 1) you'd get an incredibly short moment of totality. And the path of totality would be incredibly narrow at that point. So yes that would be somewhat less exciting.
However! You'd see more of the corona right up to the sun's edge, which is probably exciting for astronomers but maybe not a general viewer. You might also get more exciting "Baily's beads" https://en.wikipedia.org/wiki/Baily%27s_beads
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