Want to get on an airplane? You might change your mind after reading this. It turns out that hurtling through the air messes with your senses. Sometimes it messes with them so much that you can be crashing without ever knowing anything is wrong.
Flying Messes With Physics
Einstein said his most important breakthrough was when he realized that, if you put someone in a steadily-accelerating spaceship without any windows, the motion of the spaceship would be indistinguishable from the force of gravity. The acceleration would hold the person to the floor, like gravity. If they stepped on a scale, they'd weigh a consistent amount, as if their mass was undergoing a gravitational pull. If they dropped something it would fall on the floor, just like it was being pulled down by gravity. For Einstein, this connection was a brilliant revelation that brought on joy.
For many pilots, the connection between gravity and acceleration isn't as joyful. The feeling of gravity helps us get our bearings. We feel it when we tilt backwards, forwards, to the left, or to the right. Planes simulate that feeling, which leads to charmingly-named problems like the Lawn Dart Effect.
If you can lean your head back on your seat, do so just for a moment. That pressing on the back of your head is the work of gravity. It, along with experience, lets you know that you're tilting up. Unfortunately, that press on the back of the head is very close to what you would feel if you were in a plane that's level, but accelerating. Pilots will feel they're tilting upwards when they're actually level, and dip the nose of the plane down, until they steer it into the ground like it's a lawn dart.
Decelerating the plane has the opposite effect. Drop your head forward and feel the pull. You'd feel something similar if your plane is level but decelerating. Pilots experiencing this, and not checking their instruments, will pull a plane up and up, thinking that they're leveling it out.
Think back to your last trip to the amusement park. You've gotten on one of those rides that essentially just hauls you to the top of a big tower, and then drops you. Exactly at the moment of drop, what do you feel? There's a kind of roiling in your stomach because it, being surrounded by goo, is not as tightly strapped into a plummeting chair as the rest of you. You often get that feeling on roller coasters, too, but not necessarily as you fall. You get it just as you hit the top of a hill and level out after moving quickly upwards. The similarity of those two feelings gets pilots into trouble all the time. A new pilot, leveling out after a steep climb, will feel as if they are falling backwards and down. This can lead them either to panic, or to jerk the plane upwards again to counteract a "fall" that never happened.
And fake gravity doesn't just mess with your head if you speed up or slow down. It can also throw you into something called the Graveyard Spiral. The name is not an exaggeration; turns, in a plane, are more subtle than most people imagine. After a few seconds, a gently turning plane will feel perfectly level. In fact, leveling out will make people believe they're being tilted the opposite direction. (Nervous fliers, like myself, will recall being on a plane and feeling the whole thing suddenly tilt, only to look out the window and see that the plane is flying level.) If the pilot can't see, and doesn't regularly check their instruments, the plane will spiral slowly down out of the sky, without anyone noticing.
Flying Also Messes with Biology
But flying doesn't just simulate physics, it also actively messes with biology. Sometimes the problem is internal. We sense the pull of gravity, and our own motion, with the semi-circular canals in our inner ear. These canals are filled with fluid, and the swishing of this fluid gives us an indication of how we are oriented in the world. During a spin, the fluid piles up along one side of the canals like the water in a bucket being twirled at the end of a string. Imagine someone slightly tipping the bucket during the twirl, and the wild swishing of the water inside it. That's what happens when you suddenly tilt or rotate your head quickly while you're in a turning airplane. The liquid in the ear canals moves around violently, giving pilots the sensation of being in a tumble-drier, or of rolling down a hill. It can last for 20 seconds, during which a great deal of unpleasant things can, and often do, happen.
Another biological screw-up is more likely to be evoked when you're looking at venetian blinds or a screen door. Sometimes, if you're looking at a pattern, and part of the pattern is out-of-sync with the rest, that part of the pattern will jump closer to you, or appear farther away than the rest of the pattern. This is what spurred that awful Magic Eye poster craze a couple of decades ago. It's also what causes pilots, looking down on waves or blocks of farmland, to think the ground is closer or farther away than it really is.
And finally, there's a problem with the way people perceive direction. We know where an object is because we see it in relation to reference points. Take away our reference points, and we're lost. Under the right circumstances, in a plane, a fixed point of light to one side of the pilot can seem to move in front of them. Although we don't notice it, our eyes are constantly making little jumps. Those jumps might make near objects seem to change position, but when it's light we have background objects to ground our point of view. On a dark night over the ocean, or over an empty stretch of land, a star or a single light gives a pilot no reference points. Because of the pilot's own eye movements, the star seems to be moving slowly in front of the pilot. A pilot, using a fixed star, can steer off course without ever knowing it. Just another way our biology combines with modern technology to steer us towards mountains.
So now that you're never flying again, what do you think you'll be doing this summer? Rafting trip? Train travel? Staying in one spot and allowing yourself a lot of reference points?
Top Image: Staff Sgt Simons. Moonlight Image: Aleksandr Markin.
[Via Fixational Eye Movements and the Autokinetic Effect, The Human Balance System, The Graveyard Spiral, Perception of Tilt]