The part of light we never see
Sunlight contains far more than what human eyes register. The visible spectrum, the band of wavelengths our photoreceptors detect, runs roughly from 380 to 700 nanometres. Ultraviolet light sits just below that, between 10 and 380 nanometres. We cannot see it. Many animals can, and for them it is not a bonus feature. It is the primary channel through which the world makes sense.
