Polar Bear Fur: Newsletter Challenge (February 2012)

The coat is made up of hollow hairs (fur) and are translucent.

The skin underneath is actually black.

Source: Armchair Reader - Book of Misconceptions - One of my Christmas gifts from the wifey - happened to read about Polar Bear fur the other morning whilst in the library

I believe that the hair (fur) lacks pigment because it is hollow, just my guess

Polar Bear Hair or PBH, appears white in colour due to the properties of the hair...PBH is actually translucent with a thin hollow core and only appears white due to light diffraction...PBH contains keratin which absorbs heat keeping these beasties comfortable on the frigid temperatures of the North...The fur can take on a yellow color from the oils it ingests mostly from seals..

Diffraction, just like my 'gray' hair which is actually colorless

Well, there are three effects at work.

Since the hairs are translucent, they actually conduct sunlight to the skin to provide some warmth.

The density of the fur hides the skin coloration and traps a layer of air next to the skin as insulation to maintain body heat (and traps a layer of water against the skin to provide insulation when it swims.)

The whiteness, which is due to fresnel reflections and diffraction, allows the polar bear to blend into the background as a disguise; useful when it is hunting.

Or the head of a beer.

Indeed.

well spotted - GA

_{(but probably aught to have employed quotes. Naughty YL!)}

Little bit too well known, but for added spice they can also be green.

Explanation.

the hairs of the polar bears are tubes (optical effects, like glasfiber)?

The reason the polar bears fur lacks pigment is tied directly to keep the animal warm. The hair acts like a fiber optic strand. Directing sunlight to the bears skin. The polar bear's skin is actually black. This is very efficient in absorbing the heat transmitted by the sun. If I'm not mistaken, the hair is also hollow. Making it a great insulator as well.

Fibre optics at play!

Polar bears do not have white fur, each hair shaft is pigment-free and transparent with a hollow core containing keratin.. These hollow hairs are called guard hairs. These clear-colored, air-filled guard hairs serve two primary purposes. 1) Help transmit heat from the sunlight to their black skin as a solar heat collector. Their guard hairs are waterproof, which help keep the polar bear warmer in water.

The dense fur completely hides the black skin underneath, which absorbs the heat energy from sunlight plenty of light still passes through the transparent hairs. Viewed side-on the hair will appear colorless, viewed from the top the hairs will not look semi-transparent.

The black skin is hidden from view and it is also prevented from emitting any heat energy back out from the polar bear's body. If you tried to photograph a polar bear with a thermal imaging camera, all you would see is the stream of breath coming out of its mouth. It is so well insulated, it just doesn't show up. 2) The hollow core of the hair shaft reflects visible light the same way as reflection of the sunlight makes snow and ice look white. When it is piled on top of itself it reflects all light and becomes white , much like sugar crystals. This light which is absorbed is literally trapped in the hair shaft.

This trapped Light heats the body?

If no pigment in the fur, then the white incident light finds nothing that can absorb some frequency or frequencies of which is composed, then is reflected in the same condition showing the same white perception. The same happens with white hair, that also lack of pigment.