You know what’s awesome? The moon. And I’m gonna tell you why.
Of the other rocky planets in our solar system, two don’t have moons at all, and the other, Mars, has two little rocks that are so small that you could walk around the small one, Deimos, in less than a day. An elite ultrarunner could run around the bigger one, Phobos, in about 8 hours. Scientists who study how moons form have found that only one in four hundred stars of planet forming age had evidence of the kind of activity that would lead to a moon like Earth’s.
Our moon is a rare and precious thing.
And if we didn’t have it, Earth would be radically different. Nights would all be dark. Tides would be negligible. Earth’s axis would wobble wildly, leading to climate chaos. And, awesomely, Earth’s days would be only be about 8-12. That’s so goddamn cool.
Even if something human-like would possibly evolve on a world like that, our knowledge of astronomy may have been way behind what it actually is.
The moon’s 29 ½ day cycle of phases is probably the reason that humans figured out how to keep time. And most cultures that invented calendars tracked months (moonths) long before they could track the year by the sun. Because it is friggin hard to figure out when a year begins and ends. Maybe successes with sorting out months was what inspired early people to examine the sun at all.
Without the moon, there would be no eclipses. Mars actually has lots of eclipses, but, if you were there, you might not even notice them. Deimos eclipses are barely noticeable. And even Phobos only obscures about a quarter of the sun.
But by some absolutely stunning coincidence, our moon and the sun appear to be almost the exact same size from Earth. I mean, this is an illusion, the sun could actually contain about 64 million moons, and yet, because the moon is exactly the right distance, it appears to almost perfectly cover the sun during a total eclipse.
The moon itself also gets eclipsed and this proved to be an essential clue, because during a lunar eclipse, we can see the shape of Earth’s curved shadow. And it was this fact that first convinced people like Aristotle that Earth was indeed, round.
It was mountains on the moon, as seen through telescopes, that gave truly convincing evidence that the celestial bodies were made of the same old stuff as we find here on Earth and not some otherworldly element as early thinkers had guessed.
And it was the movements of our moon that inspired Galileo to realize that that bright lights he saw circling Jupiter might be same kind of thing–a discovery that harkened in the era of truly modern science and the end of the old ideas that the Earth, and therefore us, were at the center of everything.
It is undeniable that we live on the best planet for light-years in any direction. But I think a case can be made that our moon, also, is one of the best we could hope for.