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The importance of Astronomy in world building
So, you have decided to start creating a new world for your story? Congratulations! Now it is time to actually start fleshing out your world with some details. Although this is your own world that you are in charge of, if you want your readers to be able to relate to it, it should still follow some of the basic laws of nature. This means that you probably shouldn’t have planets that are phasing through each other, or a star exploding and propelling the planet into an entirely new solar system (and not killing all of the inhabitants in the process), or anything else that is physically impossible in our universe.
The caveat to that of course is that it is your story and does not necessarily need to be set in our universe and you can create or change any laws of physics that you desire. But if you are trying to keep things both relatable and believable, here are some important things to consider while designing the astronomy in world building your own unique world.
Number of moons
That’s no moon! One of the most quoted lines from Star Wars, this goes to show the importance of determining exactly how many moons are circling your planet, and how many giant space stations might also be visible. But what impact do these moons have on your planet? A great way to start determining the impact of something on a fictional world is to compare/contrast it to similar things in our world. For instance, one of the most well-known effects of our moon is the impact that it has on our tides. So, how would it be different with two moons instead? Would the tides cancel each other out? Would they be in unison, resulting in super tides? Are their orbits not synchronous so that the tides end up vacillating between no tides and super tides?
What other impacts has the moon had on our world? Well, for starters there is the month. Although our calendar months are no longer exactly one moon cycle long, that was the original measure of a month. In fact, the word month even has its origin in the word moon. So, with multiple moons, what impact will that have on the development of a calendar for your society?
Another impact of the moon to consider is it’s effect on the behavior of both people and animals. While the moon might not really induce people to turn into werewolves, it does have an apparent effect on both humans and animals. While there may not be any studies confirming the “lunar lunacy” theory, just ask anyone that works in an ER, prison, or mental health facility what the busiest time of the month is for them and they will practically all tell you that it coincides with the full moon. The light of the full moon is also a boon for nocturnal hunters.
The Earth’s rotation
While we refer to the sunset and rise as constants that never change, that may not necessarily be true in your world. So, what differences will that mean for your world? Again, let’s look at the impacts of the 24-hour day that we enjoy here. Well, one of the first and most obvious is the telling of time. How would people tell time in your world if the days there were equal to 30 twenty-four-hour days? Would time be as important to them even? Would their society learn to focus more on the here and now? Is it possible that they push themselves to work constantly for the 15 days of light and then sleep for the next two weeks of darkness? Would some creatures have evolved to completely hide during the light period and only come out to hunt at night?
What if the day/night cycle was even more extreme than it is here on earth, going from freezing to boiling hot in a matter of minutes like in Chronicles of Riddick? Would everyone live at the poles of the planets where the changes would take longer? Would they all live underground? Have evolved some means to deal with the temperature extremes?
What if the days were extremely long? Would your people have to migrate to constantly stay in either the dusk or dawn portions of the planet? Would you have two separate societies that never actually see each other but are able to leave messages for the other to find in 6 months when they have circled the planet to that location again? What if they are circling the globe parallel to each other but never actually crossing a mountain range or something else that separates their tracks?
Weather would be another thing to consider if you are altering the rotation period or speed of the planet around the sun. Our weather is bases off of hot and cold air interacting, so if you have a faster or slower day/night cycle, you will end up with either less or more predictable and severe weather events.
The night sky
Going along with the multiple moons that you may have visible in your sky at any given time, what else is up there? Besides giant space station death stars anyway. Are there other planets that people are able to see either with the naked eye or with whatever level of technology they have developed? Are there any superstitions or religions associated with these planets? What about constellations of stars? Are they just used to determine seasons and global position like they are here on earth? Are there any stars or planets visible during the day at times? How reflective is your moon? Does it give the light it reflects a different tint? If you have multiple moons do they both reflect light the same?
Hopefully these questions give you a bit more of a basis for developing the astronomy of your world. Let me know in the comments below if you have some other things to consider when setting up the astronomy in world building adventures!