Have you thought about your sun, moon and more?

[Mythopoet]

I find it interesting that something as loaded with mythological and superstitious significance (and is still not terribly well understood by the average person) as space is the area of a setting that worldbuilders try to make resemble reality so closely.

I like imaginative cosmologies as well. That's why I picked up the book "Under the Pendulum Sun" just based on the title. But then the story ended up being icky so you never can tell.

when the fantasy genre is supposed to be about doing anything so long as it all remains internally consistent.

Yes, but if you can do anything with fantasy then that also includes creating an imaginary world as "realistically" as you want to. You can't say you can do anything in fantasy and then suggest some people aren't being creative enough with their choices. Worldbuilding is about creating the type of world that appeals to and/or fascinates you no matter what kind of world that is.

 

[WooHooMan]

Yes, but if you can do anything with fantasy then that also includes creating an imaginary world as "realistically" as you want to. You can't say you can do anything in fantasy and then suggest some people aren't being creative enough with their choices. Worldbuilding is about creating the type of world that appeals to and/or fascinates you no matter what kind of world that is.

I think you might have taken what I said out of context. It’s fine if that’s the type of setting people want to make. I was just saying that I wish there were more examples of people getting weird with their settings. Personally, that’s something I want to see.

I’m just trying to suggest to people that IF you specifically want a unique and creative setting, one way you can try going about it is by getting nuts with the astronomy. You can do that without breaking immersion or getting dumb with your setting. And I don’t mean to disparage anyone who doesn’t go that route with their setting.

 

[Yora]

I had an idea and actually modelled a simulation of it in Universe Sandbox 2, to see if such a configuration would physically work and what that would mean for seasons and so on. I already had that programm around and put in the numbers just for fun. This is full on astronomy nerd stuff.

The sun is a K-type orange dwarf star, in size between a yellow dwarf like the sun and a tiny red dwarf. This is fairly arbitrary and comes simply from my astronomical opinion that orange dwarfs are by far the most likely stars to have inhabited planets in the universe. (They are much less volatile and more stable than red dwarf, and while they are much more rare and don't live nearly as long as red dwarfs, they are much more common and live many times longer than yellow dwarfs.)

Since the star is smaller and less hot than the Sun, the planet needs to be closer to get the same amount of heat. Being closer means that the star looks bigger, so in the end it looks almost the same size in the sky as the Sun. (There are ways to calculate this, and I did.) I am not going deeper into the physics of the light spectrum here, but my understanding is that the daylight would look a little dimmer and a slight bit more orange than the Sun. Which natives of that planet would not be able to tell, but whatever...
Since I was using (very simple) astronomical simulation software, it also gave me the number of days in a year, under the assumption that a day is 24 hours. (Which it is, because I don't think you could communicate different but similar day lengths in plot.)

The other thing I did was going all out with the moon. The planet and the moon are actually a binary pair, consisting of an Earth-like terrestrial planet and a blue gas dwarf. We don't have gas dwarfs in the solar system and they have only been discovered 8 years ago. (Cutting edge astronomy here.) I even went to the insane effort of researching if the gases that make a gas planet blue could exist at the temperatures the planet would have if it's the same distance from the star as an Earth-like planet. I think this is by far the most hilariously excessive piece of research I've ever done. I doubt many Hard Sci-Fi writers would have made that effort.
Again, I added this planet to my simulation of the star and the world and it told me how long a month would be, and also allowed me to calculate that this planet would have 8 times the diameter of the Moon when seen in the sky, and 72 times the area. This is about the area of sky covered by your outstreched fist, as opposed to the area covered by a fingertip for the Moon. (Yes, the Moon is really only that small. And this works for people of every body size because having shorter arms also means you have proportionally smaller hands, so that cancels out.)

With all this information, I was able to create a calendar that has 24 months, with every month having 16 days. However, this comes out to 384 days, while it only takes the planet 381 days to go around the star. (While the planet is closer to the star than the Earth is to the Sun, the gravity of the star is much smaller so the planet has to go much slower to stay in orbit, making a year actually a bit longer.) Then I did something that might be even sillier than researching the properties of gases in a gas planet and created a more refined callendar that consists of a 16-year cycle in which every 6th, 11th, and 16th year are leap years with only 23 months instead of the usual 24 months.
I admit I have no clue how this might ever become relevant or remotely worth mentioning.

But the one thing I was really interested in with all this effort was to calculate what solar eclipses would be like. Here on Earth we live in a remarkably and extraordinarily rare place in the universe where the Sun is almost exactly 400 times as wide as the Moon, but also almost exactly 400 times as far away. Because of this, the Moon can cover up the Sun exactly when seen from the surface of the Earth. (Every sci-fi universe should have alien tourists visiting Earth for this amazingly unique natural event.) If the planets were all perfectly aligned, you would get a total eclipse every month during the new moon. This would also be the case with Earth, but in nature planets aren't that perfectly aligned (unless in extremely care coincidental cases, like with the Sun and Moon size), and so the Moon keeps passing the Sun a little bit too high or a little bit too low to cover it up. But with the moon being having 72 times the area of sky than the star, it doesn't need to pass in front of it anywhere nearly as exactly to cause an eclipse, so eclipses will be much more common. I made the decision that the angles will be at whatever degree is needed to have a total eclipse happen on average once every spring and once every summer. Some years there might no eclipse happen during a season, and in other years there might even be two happening two days in a row.
This makes eclipses very predictable, but not 100%. People know that an eclipse could happen at the end of the 4th, 5th, 6th, or 7th month, but you won't know which one. And just because there was one in the 5th does not mean you're completely safe at the end of the 6th. Probably, but it could happen. And because the moon is so much larger than the star, it will take a lot longer for it to pass in front of it. And again, if you're crazy enough, you can calculate this. If the moon just covers the star with its edge, it won't take much longer than on Earth and will be over in 5 minutes or so. If passes over the star right with its own center, the eclipse will last over half an hour. And eclipses are dangerous because that's the time when the borders to the Spiritworld open and the spirits are getting super agitated. When you make any travel plans, always make sure that you won't be on the road during once of the eclipse days. And when it is an eclipse day, always stay close to home. If the sky isn't overcast, always look up around noon to check if the moon gets dangerously close to the star. And when the sky is overcast, maybe better don't go outside at all.
After I had lost the last shreds of sanity, I also figured out where the summer and winter solstices would be on my 16-year, 381-month, 6096-day calendar would be. And the spring and fall equinoxes as well. These are traditionally very magical days, and as it happens, in some years these can be eclipse days. Storytellers might be embellishing things for dramatic effect, but there is a staggering number of great cities and kingdoms that are said to have been destroyed by disasters on these days. And this is where these 20ish hours of work actually have a payoff! This is great story material.

I very much discourage anyone from making anywhere near this effort, unless you are a huge astronomy hobbyist.

 

[D. Gray Warrior]

I’m not currently using it for any of my worlds yet, so it’s not officially canon, but I am working on a world that does not have a sun, at least not in the traditional sense.

Instead, there is a Phoenix that serves as the world’s source of light and heat. It flies around the world, stopping to rest and eat. The Phoenix’s natural lifespan is only a thousand years or so, but can be extended beyond that. When the Phoenix dies, it combusts and its remains fall to the ground, setting the world ablaze. This event is known as the apocalypse and has happened three times before, with a new Phoenix being born each time. The Phoenix also alternates between male and female. The first Phoenix was male, but the current one is female.

The inhabitants of the world believe they can prevent or at least postpone the apocalypse by worshiping the Phoenix and giving her offerings and using those to extend her lifespan. Neither one can survive without the other. Eventually, a whole religion was founded upon this idea, and a theocracy rules the world.

Originally, the moon was the same as our world, a ball of rock orbiting the planet, but I think it also might be a bird as well, making the religion dualistic.

 

[SMAndy85]

The planet of Aitera is tide-locked to the god of light, who just so happens to look like a red dwarf star. The people believe that being too close to one of the gods will kill you, because they are too powerful. This is fairly true, as travel too far into the hot side and you'll die from heat exposure and lack of water... Likewise, go too far the other way, and the goddess of dark will kill you with the ice that litters her realm.

The goddess of life was created when the two first gods met, an explosive meeting that also shattered the moon and imbued it with power, leaving the people created by the goddess of life to look up at a broken sphere with a trail of rocks. The goddess of life is the only one that people can directly interact with, as she expended most of her power creating all the life on the planet. No one knows who she is though, as she reincarnates through the generations, and doesn't go around telling everyone who she is; why would she? She's been imprisoned in past lives and forced to use her remaining powers to heal people against her will, so anonymity is her ally now.

The moon was imbued with power in the explosion too, so now that is the god of magic, and imbues that power through crystals that people implant in their skin.