Science fiction authors tend to try to get the science right — or at least, we’d like to hope they will. There are many exceptions. We know a lot more about physics and biology today than was known even 50 years ago, so it’s not quite fair to the authors of the Golden Age to expect that they would avoid falling into what would today be classified as silly mistakes.
In Asimov’s famous robot novels, the robots had vacuum tubes for brains, because the transistor hadn’t been invented yet. He gets a pass on that one. Still, we feel entitled to hope that an SF author today has done his or her homework.
It’s harder to criticize a fantasy novel for not getting the science right. I mean, it’s fantasy! We know there are no dragons or unicorns. We know magic spells don’t really work.
But while a fantasy author has free license to invent cool magic systems and exotic creatures, readers will feel inclined to draw the line somewhere. If a character in a fantasy novel survives being frozen in a block of ice for days on end, we would naturally expect that there’s some magic-based explanation. Playing fast and loose with basic physiology is not advisable.
At the moment I’m contemplating doing a total rewrite of a novel I wrote during the last couple of years — a rewrite so complete that it might as well be a new novel. In addition to the thorny plot problems I hope to fix, I’d like to address a couple of the world-building deficiencies around which I skated rather too blithely.
Seasons, for instance. Have you noticed how many fantasy novels set on other worlds have Earth-type seasons? Our own planet has seasons because of its unusual 23-degree axial tilt. There’s no reason at all to suppose that another Earth-type planet would have seasons.
The approximately 24-hour day is probably too fundamental to want to tinker with. If your planet rotates every seven hours, you’re writing science fiction, not fantasy.
How about moons? This is a trickier question than it may appear. Our own planet has, if we’re to judge by what we see in our own solar system, an unusually large moon. And only one moon. Mars, Jupiter, Saturn, Uranus, Neptune, and Pluto all have multiple moons, but with the exception of the Pluto/Charon system, the other moons we know of are all much smaller than the planet around which they orbit. And of course Venus has no moon at all. We might guess that a planet in a fantasy novel could easily have more than one moon — and indeed, this is one of the cues fantasy authors use to make it clear that the story is not set on our own Earth.
But what would happen if Earth had two or three moons? First, some of them would be orbiting much further away than others. For that reason, they would be much smaller optically. And probably smaller physically too. If one of them was as large as our own moon, it would distort the orbits of the other moons in chaotic ways. A cataclysmic collision would not be out of the question.
On the other hand, if all of the moons are significantly smaller than our own, plate tectonics would operate poorly, if at all. There would be little volcanic activity on the planet. As a result, the distribution of elements might be quite different: The planet might be metal-poor, for instance.
And what if we go the other direction? What if we desire to give our fantasy planet a moon that is larger than the Earth’s moon? It would have an atmosphere. Clouds would drift across its face, and that would be a lovely literary effect.
Unfortunately, a larger moon would cause a major literary problem due to tidal locking.
Our own moon is tidally locked to the Earth. That’s why it always shows the same face. When two bodies are closer to the same size, they will both become tidally locked a lot sooner — like, millions of years sooner. The planet’s day will lengthen until the day is the same length as the month. The moon will always be visible on one side of the planet and never visible on the other side. And because the days will be very long, the temperature swings between day and night will be horrendous. This will impact the biology of all the animals and plants.
Kiss that big cloud-wrapped moon goodbye.
I’ve also been thinking about a red dwarf companion star with an elliptical orbit of 80 years or so. This 80-year cycle would substitute nicely for seasonal variations. Or would it? The gravitational pull of the companion star would probably make the orbits of the inner planets chaotic, and that would lead to all sorts of literary (and evolutionary) complications.
Maybe I should stick with one moon and four seasons. But that feels so lazy from a literary standpoint. I’m going to have to think some more about this.