Why are polar bears white?: Reflective

       So how did polar bears that live in a snowy-white world come to have white fur? Believe it or not, their hair isn’t actually white! Their long outer hairs, which protect their soft, thick undercoat, are hollow and transparent. The thinner hairs of their undercoat are also colorless. Polar bear hair looks white because the air spaces in the hairs scatter light of all colors. When something reflects all of the visible wavelengths of light, we see the color white. Some scientists believe the polar bear was once a close relative to the brown bear. They think that, over time, polar bears moved to the Arctic, where they adapted to their surroundings by developing fur that would help them blend in with the harsh, white Arctic ice. Not all polar bears look white, though. If you’ve ever seen a polar bear in a zoo, you may have noticed that its fur can appear almost green. Scientists discovered that algae from the pond waters in the bears’ enclosures made the bears turn green. They learned these algae were found not on the surface of the hairs but inside the hollow hairs!