Is blood ever blue? - Big Questions (Ep. 17)

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 Bribe-Biesca's big question

Is blood blue when it is in an oxygen-starved environment? And if so, how can I prove it

I assume you're talking about human blood, Pablo, because that's a common misconception. I'm going to 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 it. 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, these 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

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

Well, Dr. Keenla and his team figured out some stuff in 1996. It's pretty complicated, so

so if you want some more in-depth information, there's a link in the duble-do. 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 a refresher 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 Miriam and Webster, scattering of light by particles small enough to render the effect selective

so that different colors are deflected through different angles. Well, that definition's 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. 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, you're like, oh hi, Miss Piggy, your car is pink

But then at night, when it's all dark in different color, it still looks pink to you

And she's probably nagging you the whole time. Like, yeah, oh, crummy, oh

The same goes for how your veins appear when you look at them. You can thank your visual cortex for that

Don't think Miss Piggy. She just fell on the ground. Thanks for watching Mental Floss on YouTube

made with the help of these Miss Piggy's. If you have a question, please leave it in the comments below

See you next week. Miss Piggy keep falling off of my leg