Nature & Physics
Why Is Snow White?
Snow is white because millions of tiny ice crystals scatter all wavelengths of light equally in every direction. Your eyes receive the full spectrum at once, which looks white.
snowlight
Light & Atmosphere
Why Is the Sky Blue?
The sky is blue because blue light scatters off air molecules more strongly than red light, filling the daytime sky with scattered blue wavelengths.
skylight
Blood
Why Is Blood Red?
Blood is red because of iron. But the full story — involving protein folding, oxygen chemistry, and why veins look blue — is far stranger and more beautiful.
bloodhemoglobin