Why Do People Get Seasick?
We get seasick because our brain doesn't know which way we are moving.
Our bodies use three ways to know whether we are moving or staying still. Don't believe me? First try balancing with both feet on the ground with your eyes open. Yeah, that's really easy - we call it standing. Ok, now close your eyes - it's still easy. Try standing on one foot with your eyes open. Still too easy? Now try standing on one foot with your eyes closed!
Our bodies use several ways to know whether we are moving or staying still. We use our vision, our sense of proprioception, and our sense of balance.
When we look out of a car window, our eyes tell us that we are moving. When we run on a baseball field, our eyes tell us that we are moving. When we close our eyes, our sense of vision cannot tell us if we are moving. Closing our eyes blocks out one way we can tell if we are moving.
The second way to tell if we are moving is the sense of proprioception. 'Proprioception' simply put, is how your legs knows they are touching the ground. When you walk you put one leg in front of the other. When you jump you contract the muscles in both legs. When you lean to the right, the right leg notices more pressure while the left notices less. If you lean too far to the right your brain says "hey right leg, push off a little bit because we don't want to fall." When you balance on one foot, you loose some of your sense of proprioception because the other foot does not know if you are moving.
There is one more way that our brains know if we are moving or not: our sense of balance. Our sense of balance is contained in our inner ear, in an organ called the labyrinth which means "maze." The labyrinth has three pretzel-like rings called semicircular canals. Each semicircular canal is at a 90-degree angle of each other. Inside each semicircular canal is fluid. The motion of fluid in the semicircular canals helps your brain tell if you are moving.
To better understand the labyrinth, next time you pour your favorite juice into a cup, try turning the cup. Notice that though the cup turns, the juice stays relatively in place. Your labyrinth works the same way. When your head turns, so turns your labyrinth! In each of the labyrinth's semicircular canals, the fluid stays relatively still, just like the juice in the cup you just turned!
The semicircular canals are lined with receptors that tell if the fluid has moved. Each of the three canals represents an axis of rotation. Since rotation in three dimensional space has three axises (X,Y,Z), your labyrinth has three semicircular canals! By knowing the relative motion of the semicircular canals your brain can help you keep your balance, even when you are balancing on one foot and have your eyes closed!
The brain needs to know when we are moving. That's how we can run to catch a baseball, look at it in the sky, and not fall over. When we slip on ice our brain instantly places our hands to catch our fall in the right direction!
But why do we get seasick?
A boat rocks back and fourth with the motion of the waves. Our body moves in space, but does not move relative to the boat. Our labyrinth is not fooled - it tells the brain we are moving. While sailing, we need to do many things like look at a chart to plot our course. The book is not moving relative to us, so our eyes tell our brain "hey brain, we are not moving." We are sitting at the navigation station so our legs (proprioception) tell our brain, "we are not moving." Our brain gets competing inputs and gets confused - our brain doesn't know which way we are moving. Our brains don't like to be confused in this manner, and we don't feel too good. We call that seasickness.
So how can we prevent seasickness?
We must un-confuse the brain. Rather than look at a map, we look out at the horizon. The eyes tell the brain "this line of white sky and blue ocean appears to be moving." Well, the brain is a little smarter than that! The labyrinth meanwhile is sensing that our bodies are moving the same way. The brain puts these two things together and says "oh, I am moving relative to the horizon!!!". Thus re-orienting itself and settling that ... unsettled feeling.
TSS
