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Re: _Sinosauropteryx_ fibers

Ralph Miller said:
>Polar bears, it seems, have black skin and clear, hollow fur.  The
>transparent fur conducts the warmth of the arctic sunlight to the
>heat-absorbent black skin, much as man-made fiber optics convey light from
>one end of a transparent fiber to the other.  So polar bear fur is cold on
>the surface, but the animal's skin is warm.  Moreover, the hollow fibers
>trap air inside, providing additional insulation.  I find these adaptations
>most remarkable, but it is the implications of the "hollow fibers" that I
>will discuss here.  (Unfortunately, I have no references; please correct me
>if I'm misrepresenting the functional morphology of polar bear fur).

I'm not sure why this would work in the polar bear.  Optical fibres depend
on having a medium surrounding the fiber (e.g. air) which has a lower index
of refraction than the fiber.  Only in this way can you get the total
internal reflection on which optical transmission depends.  If the hair or
feather is hollow, then the transmission medium is air.  Its hard to see how
the fur could have a lower index of refraction than air.

  --Toby White