20. Optical Delusion
The picture of the world we "see" is artificial. Our brains don't produce an image the way a video camera works. Instead, the brain constructs a model of the world from the information provided by modules that measure light and shade, edges, curvature and so on. This makes it simple for the brain to paint out the blind spot, the area of your retina where the optic nerve joins, which has no sensors. It also compensates for the rapid jerky movements of our eyes called saccades, giving a false picture of steady vision.
But the downside of this process is that it makes our eyes easy to fool. TV, films and optical illusions work by misleading the brain about what the eye is seeing. This is also why the moon appears much larger than it is and seems to vary in size: the true optical size of the moon is similar to a hole created by a hole punch held at arm's length.