Lunar illusions (and the origin of the Moon's name)
Where did the word "moon" come from? And "lunar"?
Three lunar illusions
During these holidays, on one of those summer nights that we miss so much (and September hasn't even come to an end), my three-year-old son, Matias, pointed at the full moon and said, laughing: "Look, there's a man there!”
The Man in the Moon is an old companion of humanity... The best-known image is from Georges Méliès' film, Le voyage dans la Lune (1902), where the man in the moon has a spaceship in his eye.
We see a face there because of pareidolia, our tendency to see patterns where there is nothing more than (in this case) random specks — if you look long enough at clouds or rocks, you also start to find objects and people.
The Moon, which has been with us forever, deceives us in more ways than one. When it's near the horizon, for example, we all see it as being much bigger than when it's a little higher up.
If we use a ruler or a coin to compare, we see that the circle neither increases nor decreases — but we all remember the giant (and often orange) moon of certain nights... Our brain interprets the moon as being much bigger than it really is.
Finally, the biggest illusion of all: the Moon and the Sun seem to be the same size. To humans who thought about these things a good few thousand years ago, it would seem perfectly natural for the king of days and the queen of nights to be the same size. So much so that the Moon can cover the Sun perfectly during a total eclipse.
In fact, the Moon is 400 times smaller than the Sun — but it is also 400 times closer to the Earth... What would seem natural in prehistory seems an extraordinary coincidence to us today, now that we know the real dimension of the Sun and the Moon.
The origin of the word "moon"
But what about the name Moon? Where did it come from? The word comes, ultimately, from Proto-Indo-European, the language that gave rise to almost all the languages of Europe (and its surroundings), and which has been reconstructed by linguists in the last 200 years.
In that language, there were two ways of designating the moon. The first, and most common, was "*mḗh₁n̥s", which was derived from the verb meaning "to measure" — the moon was used to measure time... The same word was used to designate the subdivision of the year and, with that meaning, it has come to us in the form "month". It was the same word that gave origin to the English name "Moon" — and many other words for Moon around Europe.
There was another word, which was probably used in more poetic discourse: "*lówksneh₂". It meant something like "shiny object" (incidentally, the root of this word has also given us words like "light"). With the constant weeding out of sounds over the centuries (always compensated for by materials being added elsewhere in the lexicon or grammar), this word ended up in the Latin "luna".
“Luna” not only gave rise to the various words for moon in the Latin languages - starting with the Romanian "lună" and going through the Italian "luna", the French "lune", the Catalan "lluna", the Castilian "luna" (there are a few more along the way, I know), ending up in the Galician and Portuguese "lua" — but also gave English words like "lunar".
It was in the lunar module that, not even seven decades after Méliès' film, we actually reached the Moon, landing not in one eye, but in the Sea of Tranquillity. About this achievement, I recommend the amazing documentary Apollo 11, by Todd Douglas Miller (2019). It was composed exclusively with archive footage — and leaves us open-mouthed, even knowing how the story ends.
The story, in fact, doesn't end. We will go back to the Moon sooner or later — and in the meantime there will always be a child looking at the moon, imagining a human face there and asking questions.
I’d like to thank Jennifer King, my colleague at Eurologos-Portugal, for proofreading the text. You can find a Portuguese version of the article in Certas Palavras.
“Moon” is the 4th word in our 101-word series. Don’t forget to subscribe to receive the following 97 words from around the world.