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Hi, I'm Craig; If you prick me, do I not bleed? And this is Mental Floss on YouTube. Today, I'm going to answer Pablo Bribesca's big question, "Is blood blue when it is in an oxygen-starved environment, and if so, how can I prove it?

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I assume you're talking about human blood, Pablo, because that's a common misconception. I'm gonna explain the reasoning behind that myth for you today, so don't try to prove it, because that sounds dangerous. Let's get started. You get stop-ed.

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When you look at white skin, your veins appear blue. People believe that because there's less oxygen in veins, the blood pumping through those veins is blue. In order to explain why we don't actually see blue blood, the same people will tell you that the blood turns red when it comes into contact with oxygen. These people are vampires, they're trying to get you to shed blood, do not listen to them. They're also wrong. 

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The truth is, deoxygenated blood isn't blue, its a darker red. Veins themselves are translucent, so they're the color of whatever's pumping through them, so why do they appear blue?

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Well, Doctor Kienle and his team figured out some stuff in 1996. Its pretty complicated, so if you want some more in-depth information, there's a link in the doobly-doo. 

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Allow me to bring you back to those fun days in high school science. Remember the electromagnetic spectrum? I never forget. And how we can see what is called visible light? Well, here's a refresher. 

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Violet light has the highest frequency and shortest wavelength, and red light has the lowest frequency and tallest wavelength. You may have also learned about Rayleigh scattering, which is, to quote our friends Merriam and Webster, "scattering of light by particles small enough to render the effect selective so that different colors are deflected through different angles" 

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Well, that definition was not confusing at all, sarcasm, sarcasm. Basically, what you need to know is that when light hits your red blood in your veins, we see blue light because short, blue waves cause more scattering, whereas red light gets absorbed.

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Rayleigh scattering is also why the sky is blue. In addition to Rayleigh scattering, color constancy also has a role. Color constancy is how your brain perceives an object as being the same color all the time, even when you're looking at it in drastically different light. Like this Miss Piggy car, for instance. You wake up in the morning and you're like, "Oh, hi Miss Piggy, your car is pink!" but then at night when its all dark and a different color, it still looks pink to you. And shes probably nagging you the whole time. Like "Nehhhhh, oh Kermy, ohhhh"

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The same goes for how your veins appear when you look at them, you can thank your visual cortex for that. Don't thank Miss Piggy. She just fell on the ground.

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Thanks for watching Mental Floss on YouTube, made with the help of these Miss Piggies. If you have a question, leave it in the comments below. See you next week. Miss Piggy keeps falling off of my leg.

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