A polar bear’s fur looks white, but it contains no white pigment: its long guard hairs are transparent, hollow tubes that scatter light like crushed ice, while the skin underneath is black, helping absorb what little Arctic sunlight reaches it

A polar bear’s fur looks white, but it contains no white pigment: its long guard hairs are transparent, hollow tubes that scatter light like crushed ice, while the skin underneath is black, helping absorb what little Arctic sunlight reaches it

A single polar bear guard hair, held up to the light, is almost invisible. It is clear, not white. The animal that reads as the most solidly coloured thing on the ice is wearing a coat that contains no white pigment anywhere. The white we see is a trick of structure rather than colour. The long guard hairs that form the outer coat are transparent, hollow tubes, and they scatter incoming light in every direction. All the visible wavelengths bounc…