Total eclipses are a cosmic fluke

The Sun's diameter is about 400 times larger than the Moon's. And by sheer chance, the Sun also sits about 400 times farther away. The result: seen from Earth, the two discs appear almost exactly the same size. That is why the Moon can cover the Sun to the millimetre, leaving only the corona visible — that pale ring of fire that stops your breath.

No other planet in the solar system enjoys such a fine fit. Mars's moons are too small to cover the Sun; Jupiter's are too big or too close for that perfect balance.

And there is one more fluke: the Moon is slowly drifting away from Earth, so its apparent disc is shrinking. In a few hundred million years, total eclipses will vanish forever. We happen to be alive right in time for the show.