Blue Bloods

Today in class we talked about common scientific misconceptions in greater detail.  The one misconception that has always plagued me is the postulation that our blood can change colors between blue and red.

I have had both adults and children tell me this "fact."  One summer, I argued, in vain (get it?!), with a group of my campers who vehemently insisted that our blood was blue when it wasn't carrying oxygen.  They simply could not be told that our blood was, in fact, always red.  They waved their arms around screaming, "See! See!  The veins are blue, so there!"

It seems that this question plagues many of us.  Just look at the screenshot I took of my very own Google search:

Well, Here I am to FINALLY put an end to the debate.

OUR BLOOD IS ALWAYS RED

And here is the science behind why:

The reason our blood is red is because a nifty molecule in our blood known as hemoglobin, the protein molecule in our blood, contains tiny amounts of iron. 

As most of us know, things with iron in them will eventually rust, and this rust is always an orangey-reddish hue.  What we may not know, is that rusting iron is a chemical reaction resulting from iron combining with oxygen.

Therefore, the iron in our blood gives it its reddish hue!  When our blood is de-oxygenated, it is simply a darker shade from its oxygenated version.

Another scientific tidbit about red vs. blue blood has to do with light, and how color wavelengths work.  Now, the nature of light and how it works is extremely advanced science.  But, the simplest explanation is this:

All the amazing colors we see are thanks to different combinations of ROYGBIV (red, orange, yellow, green, blue, indigo, violet) wavelengths.  Because light must penetrate the skin in order to illuminate our veins, and because different colors have different wavelengths, it is only the blue wavelength that makes it back to our eyes.

Here's a great little visual of a prism refracting light and its different wavelengths:

As you can see, the red wavelength oscillates much less than the blue, and therefore doesn't have the power (for lack of a better word) to make it out of your skin and to your eyeballs!

Now, just because HUMANS don't have blue blood, does not mean that blue blood doesn't exist!  

We know that animals have evolved and diverged over time.  Not every creature uses the same mechanism to transport oxygen through-out their body.  As stated earlier, we humans use iron to transport oxygen.  Arachnids, Mollusks, and Crustaceans, however, use copper!  When copper binds with oxygen (rusts) it turns a green-ish-blue-ish color.

If spiders didn't already terrify you enough, just remember that on top of having a freakish amount of legs and eyes, they also have blue blood!

Now you can confidently tell your friends that our blood is, indeed, red and the reasons why!

Sources:

http://scienceline.ucsb.edu/getkey.php?key=3964

http://www.livescience.com/32212-if-blood-is-red-why-are-veins-blue.html

http://animals.pawnation.com/animals-copperbased-blood-8379.html