One from Tolkien: There’s a Dwarven festival on a certain day of the year. If, on that day of the year, the Sun and Moon can be seen together in the sky, it’s called Durin’s Day, but (as of the time of the story) nobody any more has enough lore to predict whether that’ll happen in any given year.
But it takes a remarkably small amount of astronomy lore to know that, on almost every day, there will be some time when both the Sun and Moon are up.
Not quite what he was driving at, I think. Tolkien was definitely quite astronomy-conscious and took things like lunar phases seriously in his worldbuilding!
Thorin identifies “the first day of the dwarves’ New Year” as “the first day of the last moon of Autumn on the threshold of Winter”. The “first day of the last moon” phrasing suggests a definite characteristic lunar phase that marks the transition from one (synodic) month to the next. “Durin’s Day” refers specifically to when “the last moon of Autumn and the sun are in the sky together”.
And indeed, on the Lonely Mountain in “the last week of autumn”, Bilbo happens to see “the orange ball of the sun sinking” in the west, and “there pale and faint was a thin new moon above the rim of Earth”. Evidently the “first day” of the month according to the dwarves occurs after new moon. But what’s at issue here is a problem in determining the first visibility of the lunar crescent, which throughout the history of ancient astronomy was notoriously hard to predict. It’s still a challenging problem for globally accurate predictions of month transitions in the Islamic calendar, which likewise begins months at first-crescent visibility.
Whether observers will actually see the new crescent moon before sunset at the theoretically earliest possible moment depends on a lot of factors, including the moon’s position in its orbit, the sun’s longitude, the terrestrial latitude, and of course horizon terrain and weather. If “Durin’s Day” means that the very earliest appearance of the crescent moon is physically visible while the sun is still above the horizon, that’s not a trivial theoretical prediction, and it’s not surprising or anomalous that the dwarves of this period didn’t know how to do it.
P.S. This appears to be another instance of Tolkien borrowing themes and tropes for Middle-earth Dwarves not only from Norse legends but also from Jewish history and culture. Ancient Jewish observance of Rosh Hodesh or the first day of the new month likewise depended on physical observation of the first visible lunar crescent in the west (which generally happened after sunset).
That just makes it worse, though. If the first day of the New Year is defined by the first visible crescent, then the Sun and Moon will absolutely be right next to each other in the sky.
But it’s very unlikely that you will see both sun and crescent moon at the theoretically earliest possible moment, while the sun is still above the horizon. The sun’s a fairly bright object, remember, and it tends to be hard to see stuff near it in the sky till after it sets!
However, if that particular combination of date and place happens to give you an ecliptic/lunar orbit angle with an unusually large elongation of the new crescent away from the sun’s disk, then you may be able to see both of them together. Seriously, it’s a nontrivial spherical geometry and/or period-relations problem, ancient astronomers spent a lot of time coming up with prediction models for this sort of thing.
Hmm, good point. I actually like that song, and the lyrics are- "You’ve been as constant as the Northern Star
The brightest light that shines,
It’s been you, woman"
Are we talking about Middle Earth, where the moon is a flower and the sun is a fruit, and they both orbit the earth, which was once flat until it was bent into a sphere? I’m not sure normal astronomy rules apply.
Calendrically speaking, normal terrestrial astronomy rules definitely do seem to apply in Middle-earth, although Elves seem able to supersede them at times (cf. Eärendil).
Just the idea of a crescent moon rising after the sun sets is making my head hurt. Like you said, a crescent moon rises shortly before sunrise or sets shortly after sunset.
That reminds me of when a movie shows a sunset by playing a sunrise in reverse or vice versa. In the Northern Hemisphere, the sun rises and sets moving to the right. It it’s moving left, you’re in the Southern Hemisphere.