Worldbuilding Wednesdays: Basic Physics
Welcome to Worldbuilding Wednesdays! Every Wednesday, we spend what is probably far too much time walking through our worldbuilding process. In this week's post, we address the consequences of messing with physics and introduce a common tactic in worldbuilding: exploring consequences, rather than fixing them.
What We Have So Far
We've got a bit of a list now: we've decided to begin making a world ruled by science-fantasy; one where real-world physics will dictate whatever we don't intentionally change; and it will be a world that features little people fighting massive creatures by leaping through the air at them.
Because we're building from the outside and working our way in, our next step will be to start working out how the world itself works. We already know that real-world physics dictates whatever we don't change, but what is it that we do need to change?
Well, probably the fastest way to make things bigger is to make everything bigger. And to do that, we should probably ask ourselves why things aren't already bigger.
The Square-Cube Law and Why it Sucks
The reason we can't have nice things is due to the Square-Cube Law, a fun little quirk of basic physics. Basically, the problem is that, if you double an object's dimensions, several things happen. First, it becomes twice as tall, twice as long, and twice as wide. Second, the areas contained by the object become four times greater; for a soon-to-be-relevant example, a slice of bone that doubles in width and length is, overall, four times larger than the original. Third, the volume of the object becomes eight times greater.
Why is this a problem? Because, generally speaking, the strength of an object is determined by its area... and the mass of an object, by its volume. A 12-foot tall human is, overall, four times stronger than a 6-foot tall human, but because they weigh 8 times as much as the 6-foot tall human, they are, pound for pound, half as strong. This works both ways, by the way; the reason that ants can carry 50 times their body weight with ease is because they're so freakishly small. An ant the size of a person would end up with strength comparable to a person.
Regardless, the problem remains: If we simply make everything bigger, what we'll end up with is a world of gingerly stepping near-invalids. That's no fun. We need to both make things bigger and address the cube-square problem.
...Well, what if we made things bigger and lighter?
The First Major Change
Okay, envision a world that is, say, 10 times bigger in every direction, but also 10 times more massive. The end result would be a planet with 100 times the surface area of Earth, but because gravity is linked to mass, the gravity of this Super-Earth is 1/10 that of regular Earth. That also means that a creature ten times bigger in every direction is, due to the cube-square law, exactly as strong (pound for pound) as its Earth equivalent.
The math is available upon request.
What else does this mean?
For starters, assuming that everything else about physics is normal, this means some very weird implications for our new world.
The Joy of Unintended Consequences
First off, yes, the animals will get bigger on this new world we're building. Not 10 times bigger, and we'll cover that in a different post, but they will be bigger. Normal-sized people will be able to leap through the air to a ridiculous extent (again, not 10 times higher, and again, we'll cover why later), which means that our Key Element is satisfied. Hooray!
...But remember how we decided that physics would default to real-world rules whenever we didn't personally make changes? That means that, in order for us to have a planet with 1000 times the volume and only 10 times the mass, one of two things had to happen.
- The planet is built like Earth, but the average density of the planet is 1/100 that of Earth. Quick, back-of-the-napkin calculations suggest that it would need to be less dense (on average) than Styrofoam.
- The planet isn't built like Earth. While it superficially resembles Earth, its innards are fundamentally different in a way that explains why it is missing 99% of the mass you would expect it to have.
Now, yes, you could have a secret third option of "It works that way because we said it does," but it is highly recommended that you don't go that route. Instead, whenever you make a big change from the norm, you should investigate the consequences of that change. Let those consequences guide your work, and you'll find yourself designing a world that not only conforms to your Key Elements, it does so in delightful ways that you never considered.
Case in point: Let's say that this world is only 10 times as massive as Earth because of scenario #2, above. There are a couple of ways that a world could be put together such that it is missing 99% of its insides, but one exceedingly simple, straightforward solution presents itself. Not only that, it leads to a whole slew of interesting new questions. For this week, we won't present the questions, or even state outright what the solution is. We will, however, give you a hint.
Conclusion
If we want a world where bigger objects and creatures are the norm, rather than the exception, and we want to be able to explain how these big creatures manage to be so big without being crushed under their own weight, probably the easiest thing to do is to make everything weigh less. If everything weighs less, though, and we're following our own rules, there's gotta be a reason for it. And no matter what reason we pick, it doesn't exist in a vacuum, which means that more is going to change than just the weight of our creatures. These consequences are a good thing, and one of the reasons that our worldbuilding is going to be so great is that we're going to investigate those consequences, rather than hide them... even if that means our planet now has something in common with a basketball.
Next time, we learn the healthy upper limit to how deeply we delve into the consequences. Then we straddle that line for awhile. Until then, happy worldbuilding!