After many comments and requests, I have returned to writing my monthly (possibly even more often) science emails. This month, I will cover an interesting topic that peaked my interest recently as it delves into the Science from between two different fields....Biology and Physics.



Q: "Why are my veins blue, if my blood is red"?


A: "Your veins are actually red, they just appear blue to the observing eye".


Wait, what? Yes, seriously, what you see as blue is actually red. Confused? Ok, let me explain. And no, it has very little to do with the lack of oxygen in veins returning to the heart.


Visible light is split into different wavelengths throughout the entire color spectrum. The color spectrum is in itself a very small portion of the electromagnetic spectrum. For example:



So what does that have to do with my veins appearing as 'blue' even though they are 'red'? Alright...now to answer that question lets delve even deeper into this rabbit hole called Science. We need to learn a little about light absorption, scattering, refraction and reflection. We will focus on Absorption and Reflection for the purpose of this article to keep things simple. Each wavelength of visible light which has a certain energy potential. Notice on the chart above how Red has about 1.65-2.00 electron volts of energy, whereas the color Blue has 2.50-2.75 Electron volts of Energy. We call this energy potential the level of "Excitation". 


Also worth noting in the chart for the purpose of this explanation is that the wavelength for blue is far shorter at 450-495 nano meters as opposed to red with 620-750 nano meters. A good analogy to understand wavelengths is to take an incoming horizontal wave and have hit a wall with a slit only big enough for a smaller wave.




Notice how blue light has a a shorter wavelength and can get through the small opening, and red light being a longer wavelength will be blocked and not make it through. In this drawing, the red light would then be observed. Of course this is a wildly simplified analogy and I haven't even gone into the debate of light being a wave function or a particle, but that too is a subject for another monthly science email to come. Different materials, like water, glass, wood, skin and even air have different chemistry which are better at absorbing some colors better than others based on their particular light absorption and reflection characteristics at the atomic level. Ultraviolet radiation is, as you might have guessed, light from our Sun/Star. When this light hits our skin on a hot summer day what happens? A large percentage of the light is absorbed and converted into heat energy and causes your skin to get warm. 


The remaining light that isn't absorbed is scattered or reflected. Energy is never lost or destroyed, just converted into other forms of energy in itself. Some of these particles even carry enough energy to be absorbed down far enough to damage DNA in our skin and cause DNA coding errors which can lead to Skin Cancer. Which is why it's good to always wear sunscreen which will reflect more light away from the skin rather than absorbing it. Which is why you always feel a little bit cooler after applying sunscreen than without, as a larger portion of the light energy is reflected rather than absorbed and converted into heat energy. 



Now, getting back the blue vein question:



As you can see in this diagram above. Red light wavelengths are more likely to be absorbed beyond the skin surface and the red color will not bounce back to our eyes as much as blue. Blue light tends to reflect much better in the biological makeup of the skin and blood vessels. Even though the rumor about veins being blue because they have no oxygen, which many of us have been told, is not completely true, there is some truth to this rumor after all. Oxygenated blue does absorb more blue light then blood without as much oxygen, which is why arteries appear more red than blue to our eyes as they are carrying oxygen to our organs. But for the most part, the blue light being reflected back more so than the red is much more to do with the particular cells and their chemistry in our skin. So when we accidentally cut ourselves, our blood is definitely red and has nothing to do with exposure to oxygen in the least.


Now that we have learned a little something about colored wavelength absorption, I think for the next science email, we take this one step further and explain how astronomers are able to detect what the atmosphere of a distant planet in a distant galaxy over millions of light years away is made up of. The answer to this is very intriguing and ingenious and uses the basis of what we've just learned answering the query about blue veins. How does the question about blue veins tell us about Exo-planet atmospheric chemistry detection? Stay tuned to find out!!!


Thanks everyone for the continual encouragement and feedback with my Science Emails. I hope I have widened and educated some minds by sharing my science knowledge with others. There is so much joy in understanding more about the world around us and how it works.


Hope you have a great week and remember to keep learning every day,


Tyler Waldrop