From the Ground Up

For any type of fiction that’s not based in our own world in the present day, world-building is both essential and deeply challenging. If you’re writing historical fiction based in our own world you can rely to a great extent on research materials, but the further back you go in time, the less settled the available research will be. Go back even a hundred years and you’ll likely be getting a lot of the details wrong.

Once you venture out into the future, or into outer space, or into a world of fantasy, you’re in utterly uncharted territory.

Consider, for instance, seasons. Here in the northern hemisphere we take seasons very much for granted, though they’re less prominent the closer you get to the equator. In many fantasy novels set in other worlds, there will be winter, spring, summer, and fall, with pretty much the familiar features, snow being one of the more obvious.

Our own seasons are caused, of course, by a pronounced axial tilt. The Earth’s axis is about 23 degrees off of the vertical with respect to the plane of its orbit. As a result, the passage of the seasons corresponds neatly to the length of the year. But this is probably an accident of celestial mechanics. There’s no reason to suppose that any other habitable Earth-type planet would have seasons. Conversely, if the rotational axis of a planet were non-vertical and precessed rapidly, the cycle of seasons might be out of sync with the length of the year.

Or consider the moon. Quite a few fantasy stories, though they’re not set on our Earth, include a moon that is indistinguishable from our own. The best scientific models suggest that our moon is very much an oddity, the result of an unimaginably cataclysmic collision between two blobs of planetary matter during the formation of our solar system. It could be argued that no matter how much a fantasy planet is like our own, it probably wouldn’t have this type of moon.

On the other hand, our moon is likely responsible not only for tides but for the circulation of the molten interior of the Earth, which causes volcanic activity and recycles both minerals and essential lighter elements. In the absence of a large moon, life might not have evolved on Earth at all. We just don’t know. Without a moon, there might not be plate tectonics, and if there are no plate tectonics mountains won’t form. Erosion will flatten all of the land masses — assuming there’s rainfall to cause erosion. Rainfall (and oceans to cause water to evaporate, leading to cloud formation) would seem to be inevitable. You can’t have an Earth-type world without oceans.

Speaking of life, of course fantasy worlds generally have horses, cats, dogs, wheat, flowers, and so forth, none of which could possibly have evolved on another world in anything like the forms we’re familiar with. Neither would humans, of course.

It becomes a real question for the writer how much of this world-building lumber should just be borrowed, without apology, from our own world and how much should be open to reconsideration. In science fiction we can expect to encounter strange animals and perhaps non-human aliens, who are after all only another species of animal (as are we). I mostly write fantasy, and in fantasy the challenge is inescapable. I gave the world in Woven of Death and Starlight two small moons and conventional seasons.

Seasons could be caused by a planet having an elliptical orbit. If this were the case, the whole planet would experience winter and then summer at the same time rather than having winter in one hemisphere correspond to summer in the other. But if the orbit is elliptical, there won’t be any other nearby planets, and what we know about the formation of planetary systems suggests that there will usually be a number of planets, not just one.

How long should the year be? If your fantasy novel features human characters (as it quite likely does), you’ll need to give your readers some idea how old they are, and that will mean using numbers that correspond to years. If the planet’s year is much longer or shorter than our own year, this will get very awkward. A young hero who is now ready for marriage because he’s six years old, or sixty, is perfectly sensible in terms of another world’s celestial dynamics, but there’s no way to explain it to the reader, other than with a messy authorial intrusion.

And I haven’t even mentioned human cultures yet. Maybe I’ll post some meditations on that topic at some point, but it’s only about a hundred times as complex as celestial dynamics, so don’t hold your breath.

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