When Edme Mariotte stared at marks on a wall in the 1660s, one mark vanished inside a six-degree hole where the optic nerve leaves the eye and the brain has been filling in wallpaper, sky, and faces ever since (opens in new tab)

Edme Mariotte made a spot disappear on a wall in the 1660s, not by tricking the wall, but by finding the place where the human eye has no light detectors at all. The French priest and physicist fixed one eye on one mark, moved another mark sideways, and watched it vanish at a precise point […]