seeingteacupsindragons:

@quill-of-thoth and @mixeduppainter asked for this, so:

Lately, I’ve been seeing a lot of beanpot’s adorable YoI Day/Night AU. And while I love it and it’s adorable, it reminded me of a couple of issues I have with day/night and sun/moon AUs, which can be summed up as “Marr cares wayyyy too much about astronomy”

But basically:

• The moon is out during the day most of the time. Moonrise and moonset have nothing to do with sunrise and sunset. The only times when they’re the same is during the full moon. In fact, during the new moon, the moon is only visible during the day. The longest period these two will go without seeing each other is the new moon. One day.

And:

• We usually have more than two solar eclipses a year. Not all of these will be total (which are more interesting to watch, of course), but eclipses are not all that rare. The moon and sun will see each other quite often, even if solar eclipses only last about eight minutes (well, during totality; this doesn’t include the approach/departure).

So, I decided I would write up a list of Astronomy Facts that might inspire some people writing these kinds of things, fanfic aus or original. These are really meant more as “Writing inspiration/prompts” more than anything, and I hope that comes across.

• Lunar eclipses happen 2-4 times a year, but this is when the Earth is between the sun and moon, so, eh.
• The equinoxes are the times of year when the length of day/night are equal. Seems like a thing to consider.
• Venus is the Morningstar: it’s only visible near dawn and dusk. I don’t really know what to make of that in these AUs, but it sounds like it has potential.
• Sunspots cycle between fading and coming back stronger. Kiss marks? I dunno, you decide.
• The Auroras (the Northern and Southern Lights) are solar radiation reacting with the Earth’s magnetic field. Literally the sun creeping into nighttime here. How romantic, right?
• The moon’s “dark side” is mostly un-cratered because the Earth uses its near side for target practice, basically. Don’t worry, the sun sees this side plenty.
• The sun is a pretty average star. Something to consider when characterizing it.
• While we think of tides as a “moon” thing, the sun actually does affect the tides, too: and when they work together, the tides are much higher or lower, and when they oppose each other (at right angles from each other, so about once every two weeks), they tides are more subdued.
• Comets only have tails when they’re near the sun, because solar radiation kinda vaporizes them. Yes, this means the sun slowly kills comets.
• The moon is definitely younger than the sun, but our current Best Theory about how the Earth ended up with the thing is that a large object hit the planet while it was still cooling after formation—so it’s been around for a long time, longer than most of the satellites in our solar system.