The myth goes like this… polar bears are white, but they have to keep warm in the winter. But white reflects light and heat, so how do they do it? By having fiber optic fur. “Fiber optics” are a type of “light pipe” that channels light extraordinarily well, sort of like an electric wire does for electric current. So, this is supposed to heat them up by channeling light to their black skin.
This is based on research that showed that polar bears are white to you and me, but don’t emit any ultraviolet (UV) light (they’re black in the ultraviolet). They thought the UV radiation was being absorbed by fiber optics and transported to the skin. It turns out instead that polar bear fur just absorbs UV on its own because of what it’s made of. So this is an example of an early, incorrect science report getting circulated and taking hold in the popular mind.
This myth gets perpetuated by the fact that polar bear fur is hollow. Fiber optics are also hollow, but not every hollow thing is a fiber optic (this is like the “a square is a rectangle but a rectangle isn’t always a square” thing).
Paul D. has an SEM picture of polar bear fur on his website (and some more information).
I was interviewing a scientist/economist (who does a lot of popularization of science) once and he mentioned that “polar bear is fiber optic” as he was discussing solar energy. I told him that, indeed, I had only recently found out that that is a myth, and asked him to retake his answer without that reference (since this was for radio). He did, but I thought his manner was odd. I saw him speak — for a LIVE TELEVISION BROADCAST — on solar energy a few weeks later. And while I sat there flabbergasted in my seat, he repeated the “polar bear is fiber optic” myth right there in front of the cameras!
Do a Google right now for “polar bear fur fiber optic” and you’ll find a variety of links, many of which shed doubt (and some which don’t) on this myth. I wonder if he researched the topic and found something compelling to convince him it was true, or whether the story was just too good to drop? So, this is how myths are perpetuated.