Why Isaac Newton Once Stuck A Needle In His Eye
Yeah, yeah, we know, smart guy, you already know all about Isaac Newton. He was the guy who discovered gravity when an apple hit him on the head, and also he invented those fig cookies and maybe that terrible tablet that Apple made in the 1990s. Or something. Right?
You're sort of right — about the gravity thing, at least. Newton's biggest contribution to physics was (obviously?) not so much noticing that stuff falls as it was discovering that the force that made apples fall was the same force that made the moon circle endlessly around the Earth (and could be predicted with the same equations).
Beyond the gravity thing, though, Newton was absolutely vital to the development of both modern physics and modern math. He single-handedly invented calculus, established a theory of physics so rock-solid that it literally took Einstein to overturn it, and laid the groundwork for optics. He also dabbled in alchemy, biblical history, and served in Parliament (via History). Oh, and once, he stuck a needle in his eye.
Wait, he did what?
Yep. At one point in his career, the genius who discovered gravity and invented calculus decided it was a good idea to jam a huge needle in his eye and smoosh it around. According to Pacific Standard, while he was working on his book "Opticks," Newton wrote that he chose, of his own free will, to take a bodkin (a large sewing needle) and "put it betwixt my eye and bone as neare to [the] backside of my eye as I could." He then proceeded to press on his eye with it and observed that he was seeing spots. Which — go fig, Newton.
The motivation, according to The Gruesome, was apparently to see what he could learn about how the eye perceives color, but all he really learned was that poking yourself in the eye disrupts your vision. Based on the experiment, Newton conceived that light was made of particles exerting physical pressure on the eye, which ... is not right, but good guess, guy who invented calculus. Also, as AAPT films on YouTube points out, you can get the exact same results by just gently poking your eye with a finger.
The correct explanation for these eye spots (technically referred to as "phosphenes"), according to the Duke Eye Center, is that the physical pressure excites certain cells electrically, which the brain then misreads as light. So now you know! And you don't have to stick any needles in your eyes. You're welcome!