By MIKAEL ANGELO FRANCISCOMarch 21, 2014 11:27am
Pick up any old photograph at home. It could be that photo your father always pulls out of his wallet whenever he tries to convince you that you look so much like your mother, or a snapshot taken at the beach or the zoo, back when you were still a toddler. Take a good look at the photo. Chances are, the colors are already faded—or at least beginning to.
Fading happens because paints absorb light energy.
“Most color you get in paints, coatings or cosmetics, even, comes from the selective absorption and reflection of light,” explained Vinothan N. Manoharan, a Gordon McKay Professor of Chemical Engineering and Professor of Physics at Harvard's School of Engineering and Applied Science. “What that means is that the material is absorbing some energy, and that means that over time, the material will fade.”
Interestingly, though, bird feathers don’t seem to have that problem: they can maintain their bright hues for centuries with virtually no difference in color quality. Unlike photographs, posters, or paintings, bird feathers don’t rely on energy-absorbing pigments that degrade over time; rather, they contain nanostructures with tiny pores arranged in such a way as to amplify specific wavelengths of light. The resulting hues are known as structural color.