optic blind spot experiment

I thought most people knew about this. but lately found it not so.
Cover your right eye & focus on the orange on the right.
move your face toward the monitor until the apple on the left seemingly disappears.
as you move closer or farther, you'll see the apple appear & disappear again.
this illustrates the human optic "blind spot". that is the area of the retina where the optic nerve connects & there is a lack of visual input from that area. with 2 eyes, the human brain normally compensates.

i've always credited this to the fact there are normally 2+ stoplights at almost every US intersection (used to be one at many) & US automobiles went to a third taillight in the 1980's from just 2 prior.

human optic anatomy is truly amazing. from the single lens element eyeball that naturally focuses on images upside-down (brain decodes an upright image) to the optic chiasm that partially criss-crosses sensory nerve cell image information to opposite sides of the brain. something of a day-to-day miracle.