A vocabulary of landscape — a landscape of words
1469 entries
iridescence
Iridescence is color that changes with the angle you look from, produced by the physical structure of a surface rather than by any pigment in it. Light reflecting off microscopic layers, ridges, or films interferes with itself, reinforcing some wavelengths and canceling others, and the wavelength that survives depends on the geometry. A hummingbird’s throat, a beetle’s back, a film of oil on a puddle, and the inside of an abalone shell are all doing the same thing.
Etymology
The word is built on Iris, the Greek goddess of the rainbow, who also served as a messenger between the gods and the world. The Greek word for rainbow gave its name to the flower and to the colored ring of the eye as well, so a garden bed, an eyeball, and a beetle’s wing case are all named for the same messenger.
Notes
Structural color does not fade, because there is no pigment to break down. Beetles collected two hundred years ago are as bright as the day they were caught, and iridescent structures survive in fossils, so the color of some fifty-million-year-old beetles is known. Crush the structure and the color goes instantly, which is the simplest way to tell it from a pigment.