Why did Sir Isaac Newton stick a needle in his eye?



He did indeed. Or more accurately, he pushed a needle behind his eye and with it, indented the sclera. The needle never entered the eye.



By doing so, he stimulated his retina in many spots and noted a "phosphene" or glowing spot that resulted from the pressure. From this he was able to "map" his own retina against where he saw the spots. This map conformed to the map on the back of a rabbit's retina that he made by shining light from a window, through a pinhole, into the rabbit's eye that had an opening cut away from the sclera allowing him to see into the rabbit's eye.



And thus Newton showed how the rays of light enter our eye by an optical system now called the camera design. And how the retina represents the outside world but with inversion (up is down and left is right).



Newton was a dedicated scientist who was willing to accept some pain and personal risk to satisfy his curiosity.



 



Credit : Quora



Picture Credit : Google