I’m writing about a lot of celestial stuff at the moment—mostly circumpolar stars, but occasionally a planet, and maybe some Sun and Moon too. One issue that’s come up, which is technically minor, but is obviously major enough for me to have a little rant here about it, is the capitalization (or not) of celestial bodies. Specifically, the Sun, Moon and Earth.
Now, Mercury, Venus, Pluto, Polaris, Vega, Mirphak, Zubenelgenubi, they all get capitalized, no questions asked. But Sun, Moon and Earth? I challenge you to find any real consensus on this.
The most common answer seems to be that you capitalize them when you’re talking astronomy to someone, e.g. “The Earth orbits the Sun, and the Moon orbits the Earth.” But if you’re just talking about them in an everyday context, you don’t, e.g. “The sun’s warm today.”
Now, that last instance looks right to me. It’s how most people write. But I don’t see any sense in it. Or any other instance of these bodies being uncapitalized. They’re all proper nouns: “a noun representing a unique entity (such as London, Jupiter, John Hunter, or Toyota)”. There are some variations in the definition of proper nouns—the names of days and months are proper nouns in English, but not in many other languages. Fair enough, they’re abstract entities. But the Sun, Moon and Earth are as proper as nouns get. They’re unique, and very concrete.
There is the fact that these words can also refer to a class of entity, e.g. every star is a sun, in its own context; Jupiter has moons. But surely if you’re talking about the Sun or the Moon, capitalizing them is a way of being clear. I guess that until we start travelling to other planets (or stars), saying, “The sun is warm today” doesn’t need much clarification. But still, the principle holds.
As to why anyone would lowercase “Earth”—I’m lost on that one. Sure, you pick up a handful of dirt, you say, “Look at this lovely earth!” That’s a different meaning of the same word, which isn’t a proper noun, so you don’t capitalize it. Simple. But when you’re saying “the Earth rotates on its axis” or “he’s the most pedantic person on Earth”—why would anyone lowercase it? Because a style guide says so? What reason does it give?
I guess there’s an argument that it’s just the natural drift of language that’s commonly used, like “e-mail” becoming “email”. But I talk about London more than the Earth, and no one has ever started writing “london” (outside SMS and people who don’t write properly anyway).
The thing is, I’ve started coming across excellent books on the history of astronomy, recent books published by reputable academic presses, and they’re lowercasing “Earth” always, even in an astronomical context.
I would say (with tongue in cheek), “It’s XYZ gone mad.” But for the life of me, I can’t think what that “XYZ” even is.