Stupid Question ™
Feb. 10, 2000
By John Ruch
Q: Why doesn’t Earth’s moon have a name like all the other moons?
A: Actually, the Moon is its name. And there’s never been a serious proposal to change it because it’s a pretty good one.
The key thing to remember is that until 1610, we didn’t know there were other moons. (Actually, some may have been sighted, but not identified as satellites.) “Moon” was simply the object in our night sky, with no larger astronomical meanings.
It’s also one with deep roots in human experience. “Moon” goes all the way back to Old Teutonic. The “Oxford English Dictionary” notes that in all Indogermanic languages, the words for “moon” and “month” are cognates; the linkage between them may be a verb meaning “to measure,” since the phases of the moon were the main way to measure time.
Then in 1610 Galileo discovered four objects orbiting Jupiter. He referred to them as “stars.” Kepler instead proposed “satellites.” Galileo also wanted to name them after his patrons, the Medicis. Outraged when the world preferred names suggested by his rival Simon Marius (Io, Europa, Ganymede and Callisto—all lovers of Jupiter in Greco-Roman myth), Galileo took to calling the objects by Roman numerals—which is still an alternative nomenclature for satellites.
By the 1660s, “satellite” had become a common term for such objects. But so had “moon.” Since it was now realized that the satellites behaved exactly like our Moon, the word was used generically.
More recently, astronomers have taken to capitalizing “Moon” to indicated the Earth’s moon. Now that we there are moons, making it a proper name is important.
Other moons have been given specific names as well, most culled from Greco-Roman myth or Elizabethan poetry.
So now we can easily tell that “the Moon” doesn’t refer to Ganymede. And you can see what sort of Galileo-type headache could be caused by trying to rename it.
However, there are some problems with retaining a traditional name as a proper name.
For one thing, it’s not universal. Scientists in various countries refer to the Moon simply by capitalizing their language’s traditional term. In Russian and most European languages, for example, the name is an offshoot of the Latin word “Luna” (also the source of our “lunar,” “lunatic,” etc.) Some cosmopolitan English-speaking astronomers have also started using “Luna.”
The traditional term also can lead to problems of definition and comprehension: Are we discussing the Moon, a moon, or a specific other moon in the solar system?
This was certainly confusing when Galileo’s discovery changed our worldview. And it may be confusing again when our worldview changes further. For instance, some scientists contend that due to its size and composition, the Moon should be classified as a planet.
So what happens if some moons, including the Moon, are planets? Maybe we’ll rename it “Lunacy.”