Today’s post is part of a special series here on Planet Pailly called Sciency Words. Each week, we take a closer look at an interesting science or science-related term to help us all expand our scientific vocabularies together. Today’s term is:
EQUILIBRIOCEPTION
The best writing engages all the senses. That’s worthwhile advise most writers will get at some point in their careers, but how many senses do we humans have?
Thousands of years ago, Aristotle concluded that we have five senses: sight, hearing, taste, smell, and touch. That seems reasonable enough, and five continues to be the traditional number of senses. But depending on whom you ask, you might get a different answer.
Equilibrioception is a sense we rarely have to think about, unless something goes wrong with it. It’s governed by the vestibular system, which is located in your inner ear.
Basically, equilibrioception is your perception of up and down. It’s your ability to orient yourself in relation to gravity so that you can keep your balance while standing or walking.
If you’re writing science fiction—especially hard Sci-Fi—this is a sixth sense you may want to think about (telepathy just got bumped to seventh sense!). The experience of zero-G, or fractional Gs, or Gs greater than one, could really screw with your characters’ heads.
Even experienced astronauts are known to have equilibrioception-related problems from time to time.
As for artificial gravity, it might “feel” a bit off too. If you’re simulating gravity by rotating your spaceship, as seen in movies like 2001: A Space Odyssey, you might experience a gravity-like pull that is skewed slightly relative to the floor. Or your feet might experience slightly more Gs than your head (especially on smaller spacecraft).
So science fiction writers, remember to engage all the senses in your writing, even senses like equilibrioception that we don’t normally think about. And if you manage to give your readers a bit of vertigo, you’ve done your job well.
Links
How to Pronounce Equilibrioception
Humans Have a Lot More than Five Senses from Today I Found Out
You Don’t Actually Have Five Senses from Modern Notion.
Planet Pailly 
I’m a descriptive minimalist myself, both in preference as a reader and in habit as a writer. I think good writing should remember that we have several senses, but not feel obligated to invoke them in every description. It makes sense to note the smell of, say, a battlefield, but not necessarily of an office the POV character is used to spending time in.
I’ve always wondered why someone on a rotating spacecraft wouldn’t feel like they were standing on an incline. I suppose designers could slightly tilted the floors to compensate for the expected rotation, but that seems like it would have all kinds of functional consequences throughout the structure.
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“Standing on an incline” is a great way to put it. That is basically what it would feel like, unless you built a spacecraft large enough to make the effect not-noticeable. And apparently it would have to be really, really freaking large to do that.
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Good point on the size requirements. Many space enthusiasts often wonder why NASA isn’t doing stuff like that, but the details are pretty daunting.
The environment has to be huge, depending on the spin rate it increases the structural requirements for the spacecraft (which increases the weight, which increases the launch costs, etc), and complicates communications and egress into and out of the craft. It’s definitely not an easy solution. (Of course, in space, almost nothing is.)
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I’m not sure I understand where you guys are coming from with this whole “standing on an incline” thing. Assuming the habitat is a perfect circle, the centrifugal force will always be pointing radially at all points along the circle, meaning you would feel as though you were standing on a “flat” surface at all points (or more like the bottom of a curved valley, since your position would feel flat, but the ground would curve up around you). Now, if you had a spinning octagon, then only the center of each side would be “flat,” and the rest would indeed feel like an incline, since the surface is not perpendicular to the radial direction. Am I missing something in the circle example?
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When this was first explained to me (by someone far smarter than I am) my understanding was that you’re dealing with vector forces. You experience one force pushing you towards the “floor” of your circular spacecraft, but you also experience a second force that is perpendicular to the first force due to the direction of the rotation.
When you add the two forces together, the net force is skewed slightly in the opposite direction of the ship’s rotation. As a result, you’d probably feel like you’re standing on an incline.
A good thought experiment for this secondary force would be to imagine you’re on one of these rotating spaceships when the rotation abruptly stops. You would not just start floating around freely. Instead, you’d retain your forward momentum in the direction of the ship’s rotation, at least for one awkward, lurching moment, before weightlessness sets in.
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