ATD sighting

[David Morris]

On 10/24/06, Tore Rye Andersen <torerye at hotmail.com> wrote:
>
> Some thoughts: Iceland Spar is a form of calcite used for optical purposes, and one of its interesting features is that it causes double refraction. See the image on this link, and then compare it with the cover of the novel:
>
> http://geology.about.com/library/bl/images/blcalcite.htm

bi·re·frin·gence (br-frnjns)  Pronunciation Key
n.
The resolution or splitting of a light wave into two unequally
reflected or transmitted waves by an optically anisotropic medium such
as calcite or quartz. Also called double refraction.

http://micro.magnet.fsu.edu/primer/java/scienceopticsu/birefringence/index.html

Light bends when it moves at an angle from one transparent substance
through another. This bending of light is called refraction. Some
transparent substances cause light to bend or refract in two different
directions, causing light to divide into two rays. This is called
double refraction or birefringence. When you look at something through
a birefringent substance, you can see a double image. Iceland spar, a
type of calcite crystal, is birefringent. Below, you can see a double
image as you look through a piece of Iceland spar.