Why Veins Look Blue Through Skin Even Though Human Blood Is Always Red
By James H. Sterling
The persistent myth that blood runs blue until exposed to air illustrates how easily an everyday visual illusion can overpower basic biological facts. Veins look blue for the same reason the sky looks blue: shorter wavelengths of light scatter through an intervening medium, while longer wavelengths penetrate deep and vanish.
Inside the human vascular network, blood maintains an uninterrupted spectrum of red. From the bright scarlet surging through the aorta to the dense burgundy returning through the deep femoral veins, the chemistry of iron and hemoglobin keeps blood thoroughly crimson throughout life. The blue visible beneath the skin is simply a trick of light passing through living tissue.
James Sterling reports on renewable energy developments, climate policy, ecological conservation, and green tech innovations around the globe.
