Transcript
This is an optical illusion based not in the human brain in psychology, but in physics. You cannot see right through me. But I see through you! But the reason why this occurs is related to why some people seem to have glowing skin, and why humans are so annoying to draw and to animate. So what the science? For those of you new here, hi, I'm Avisha. I'm a scientist focused on helping you use the latest research to better understand and improve your everyday life. When I posted my last video, I was hoping. hoping that you guys would comment about this particular effect. And y'all did not disappoint. So first up, let's put our science hats on. Now it certainly seems like this light is passing straight through my finger, thus proving that I'm at least partially translucent. So we've got an observation and a conclusion, which I'm going to label hypothesis. But one of the most important principles of science is that we cannot stop when we seem to have evidence that supports our hypothesis. Instead, we have to search for alternate explanations for our observation and try to disprove So, if light can pass straight through my flesh and out the other side, what else would I expect? Let's generate a few predictions. First, I should see the shadowed outline of my finger bone, which is definitely not translucent. Second, light should pass equally well through other regions of similar fleshyness and thickness. Thankfully, these are both pretty simple to test. You clearly cannot see my bone here. I've always been told that I have dainty slender hands. Now it comes in handy. The width of this area is basically the same thickness as that of my finger. and this area. So let's see... Nothing. No hint of light gets through. So what is happening here? It's a phenomena known as subsurface scattering. When light hits human skin, around 5% gets reflected right back. A bunch more gets absorbed by the melanin, the pigment that makes us halt pan, and also by the hemoglobin in our blood. And much of what's left gets scattered in different directions. Bouncing around the outer layers of our skin, almost like light through a fiber optic cable. The reason you don't see a bone shadow through my finger is because the light is not going straight through. It's just traveling around the outer layer and getting re-emitted. And our brains expect this effect in subtle ways that you've probably never even thought about. One of the reasons why someone's skin might appear to be healthy and glowing is actually because when something like sunlight hits the skin, a little bit of that goes through and gets re-emitted after bouncing around inside. But it sort of gets re-emitted in a softer way, which happens more in young skin than in older. This has been a pain for artists and animators over the years. When the first CGI movies came out, like Toy Story back in the early 2000, The animators didn't take this effect into account, giving everyone a flat sort of plasticy look. More recent animation software has started being able to take this into account, doing a ton of math to simulate the subsurface scattering effect. So that 10 times fast. This is with it turned off, weirdly textured, almost uncanny valley-like, and this is with it turned back on. Presto! Healthy, glowing skin. It even takes into account that virtual sort of translucency, again, for much more realism. So here's a fun game for you. Next time you're hanging out with friends, put your phone to your finger and challenge them to to figure out and explain what is happening here.
Additional notes
Replying to @Floral Overcast i was pretty blown away when i first learned this! 📚 Study Links DOI: 10.1117/1.JBO.17.9.090901 DOl: 10.1111/1523-1747.ep12479191 #science #health #anatomy #physics #optics #edutok