Visual Illusions - Insensitivity of Vision to Time
How many of you have heard, or made the comment yourself, " I never saw what hit me!" after an accident? My guess is a lot of us have.
Why does a fawn (baby deer to city folk) remain motionless when danger is nearby. Their camouflage of birth is such that, unless they move, you can't see them as they lay in the brush.
Here's another example. When a train is moving across a bridge over a road, at a constant speed, and you look straight ahead while driving, the railroad car that doesn't change its visual position is the railroad car that will be directly above your car when your car passes underneath the bridge! Your speed should remain constant as well.
A little know fact about your sensation of sight. After about twenty seconds an image on your retina (inner sensory layer at the back of the eyeball) that doesn't change position will no longer be sensed and transmitted to the brain for interpretation. It "disappears" from your consciousness. That is exactly why you "didn't see the car you hit." It was there but it didn't move from its position on your retina. Hence its position was no longer being interpreted by your brain.
This is why your instructor tells you to continually scan the horizon in front of you while flying a plane (it also works in cars) because a target you will eventually collide with will be "truly seen" long enough to take evasive steps to avoid a collision.
Another factoid about the horizon. If another plane appears to be right on the horizon, and stays there, it is at the same altitude as you are.
If the other plane, coming toward you, at first appears on the horizon and then appears below the horizon a few seconds later, the other plane is descending.
If the other plane, coming toward you, at first appears on the horizon and then appears above the horizon the other plane is ascending.
If the other plane, coming toward you, appears below the horizon and remains below the horizon the other plane will pass below you.
If the other plane, coming toward you, appears above the horizon and remains above the horizon the other plane will pass above you.
Using the horizon is important in VFR flying. It disapears in IFR flying. It is repaced by a instrument called an "artificial horizon."
If you don't use a visual scan that keeps all objects "mentally there" you may be involved in a "close call" or accident that involves the above discussed peculiarity of the sense of sight.
How many of you have heard, or made the comment yourself, " I never saw what hit me!" after an accident? My guess is a lot of us have.
Why does a fawn (baby deer to city folk) remain motionless when danger is nearby. Their camouflage of birth is such that, unless they move, you can't see them as they lay in the brush.
Here's another example. When a train is moving across a bridge over a road, at a constant speed, and you look straight ahead while driving, the railroad car that doesn't change its visual position is the railroad car that will be directly above your car when your car passes underneath the bridge! Your speed should remain constant as well.
A little know fact about your sensation of sight. After about twenty seconds an image on your retina (inner sensory layer at the back of the eyeball) that doesn't change position will no longer be sensed and transmitted to the brain for interpretation. It "disappears" from your consciousness. That is exactly why you "didn't see the car you hit." It was there but it didn't move from its position on your retina. Hence its position was no longer being interpreted by your brain.
This is why your instructor tells you to continually scan the horizon in front of you while flying a plane (it also works in cars) because a target you will eventually collide with will be "truly seen" long enough to take evasive steps to avoid a collision.
Another factoid about the horizon. If another plane appears to be right on the horizon, and stays there, it is at the same altitude as you are.
If the other plane, coming toward you, at first appears on the horizon and then appears below the horizon a few seconds later, the other plane is descending.
If the other plane, coming toward you, at first appears on the horizon and then appears above the horizon the other plane is ascending.
If the other plane, coming toward you, appears below the horizon and remains below the horizon the other plane will pass below you.
If the other plane, coming toward you, appears above the horizon and remains above the horizon the other plane will pass above you.
Using the horizon is important in VFR flying. It disapears in IFR flying. It is repaced by a instrument called an "artificial horizon."
If you don't use a visual scan that keeps all objects "mentally there" you may be involved in a "close call" or accident that involves the above discussed peculiarity of the sense of sight.
