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transcript:
Vision is arguably the most compelling human sense. Words and stories and sounds allow us to imagine strange beasts and faroff worlds, but seeing makes us truly believe they exist. And that's why we place so much effort into correcting the optics of our eyes when they don't work - whether with glasses or contact lenses or surgery. But if you're in a pinch, bleary-eyed or missing your glasses, there's a simple trick that will allow you to see clearly - just make a tiny, tiny hole using your fingers, look through it, and the world will become clear again. This works no matter how blurry your vision is -- take off your glasses and give it a try! Amazing, right?! But to explain this wizardry, we just need to remember how seeing works. Light travels outwards from a source, bounces off of objects in its path, travels into your eye and onto your retina, where it forms an image. If your eye had no lens, light from a single source would hit your retina in lots of places and result in a smeared-out mess - which is exactly what happens when I take the lens off of my camera. A lens focuses that spread-out light back into a single point, corralling it into a crisp image on your retina. And after a little excitation of light-sensitive nerves and interpretation from your brain, you see. But wait! When we look at an object, the background and foreground are usually blurry, because a lens can only focus light coming from one distance away. If an object is too near or too far, its light will again be spread out on your retina leaving you with a blur. Fortunately, muscles in our eyes allow us to accommodate by squeezing the lens, which changes its focal length so we can see at different distances - except when we can't, or when our lenses become damaged - in which case we need glasses. Unlike a lens, a pinhole or other small opening can focus light coming from ANY distance: because it's such a small opening, it only allows light to come through in one place, and thus in only one direction from any particular source. So there's no blur, and everything is in focus! If you're familiar with photography, this is why using smaller and smaller apertures makes everything in your photo come into focus. Of course, small openings like pinholes and camera apertures create crisp images by blocking rather than focusing light, so the images are much darker -- which is a major reason why we use lenses rather than pinholes for glasses, telescopes -- and eyes. And yet, in a pinch, looking through a tiny hole made with your fingers can help you see. Now do you see why?

auto_transcript:
mmm vision is arguably the most compelling human sense words and stories and sounds allows to imagine strange beasts and far-off worlds but seeing makes us truly believe they exist and that's why we play so much effort into correcting the optics our eyes when they don't work weather with glasses or contact lenses or surgery but if you're in a pinch bleary-eyed or missing your glasses there's a simple trick that will allow you to see clearly just make a tiny tiny hole using your fingers look through it and the world will become clear again this works no matter how bleary your vision is take after classes and give it a try the mold the mold amazing right but to explain this was retreat we just need to remember how seen works light to travel outwards from a source bounces off objects its path travels in here I not here right now where it forms an image if you're I had no lens light from a single source would hit you right now in lots of places and result in a smeared out mass which is exactly what happens when I think the lens of my camera on a lens focuses that spread out light corralling it into a crisp image on your et non and after a little excitation of light sensitive nerves and interpretation from your brain you see but wait when we look at an object the background and foreground are usually blurry because a lens can only focus light coming from one distance away if an object is to New Year more too far its light will again be spread out on your aetna leaving you with the blur fortunately muscles in our eyes allows to a comedy by squeezing the lens which changes in spoke a link so we can see a different distances except on weekends more when Ireland's has become damaged in which case we need glasses unlike a lens pinhole or other small opening can focus light coming from any distance because it's such a small opening it only allows light to come through in one place and us in only one direction from any particular source so there's no blurred everything is in focus if you're familiar with the tiger feat this is why using smaller and smaller apertures makes everything in your photo come into focus of course small openings like pin holes and camera apertures create crisp images by blocking rather than focusing light to the images are much darker which is a major reason why we use lenses rather than panels for glasses telescopes and eyes and yet in a pinch looking through a tiny hole made with your fingers can help you see now do you see why world the this video is brought to you in part by Audible dot com the leading provider of audio books across all types literature including fiction non-fiction and periodicals if you go to article dot com slash minute physics you can try out aloud by downloading a free audiobook at your choice like the particle at the end of the universe by my friend John Carroll who also raise an excellent blog about his ex called preposterous universe the party going into the universe is Sean's most recent book and it's about the search for and discovery of the Higgs bows on I highly recommend it again thanks to audible for helping me continue to make these videos and for giving you a free audiobook an audible dot com slash minute physics well