Vanishing Head

I don’t know if you’ve ever played the game where you hold an outstretched hand and pretend to squeeze people and objects in the distance between your thumb and forefinger.  Well, there’s another way you can make-believe cause someone’s head to disappear.  Now I don’t really want to be the type of blog that just regurgitates other posts from around the web, but I suppose I’ll make the occasional exception for exceptionally neat things.  Check it out:

I already knew about the blind spot; it was something to think about paying attention to while star-gazing.  Sky and Telescope relates it with a little more precision:

As it turns out, your eye is most sensitive to a faint object when that object lies 8° to 16° from the center of vision in the direction of your nose. Almost as good a position is 6° to 12° above your center of view. Avoid placing the object very far on the “ear side” of your center of vision; it may fall on the retina’s blind spot there and vanish altogether.

Sure enough, the YouTube video utilizes the blind spot on the “ear-side”, of your left eye.  I guess I also knew that your brain compensates for it, because it’s not as if you’re conscious of a gaping hole in your vision.  But I was quite surprised that it was sophisticated enough to complete the black bar swept through the blind spot, preserving its continuity.

Wikipedia shared another neat fact; the octopus and other cephalopods do not suffer from blind spots; their optic nerves travel behind the receptors, and so they do not form a bundle in front of the retina.

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