The truth is much more complicated - and a lot stranger! In fact, your brain adds quite a bit to the report it gets from your eyes, so that a lot of what you “see” is actually "made up" by the brain. It doesn't exist. Let’s try an experiment.
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Close your left eye and stare at the X with your right eye from about a foot and a half away. Off to the right in your field of vision you should be able to notice the circle. Don't look at the circle, just notice that it is there. Now slowly move your face towards the screen. Keep staring directly at the X with your right eye while you move in. At some point (about 12 inches), the circle will disappear (it will reappear again if you move even closer). If it doesn’t seem to work the first time, try again, keeping focused on the X the whole time and moving your face towards the page very slowly.
Click HERE to find out what the heck is going on!