More polarized fun... A much more easily viewed demonstration of the effect we are discussing here is looking at clear glass table tops outside. If you happen to have some lawn furniture that includes a clear tempered glass table top, all you have to do is stand to the east or west of of the glass and look down at it at an angle of approximately 56 degrees and you will see beautiful pools of color. The colors outline the birefringence caused by the strains in the tempered glass.
Once in a while a random observation at my back yard of the phenomenon by a friend or family member will be alarmed at "something wrong with the glass". And of course, their eyes glaze over when I try to explain it. You might wonder why I immediately recognized Harry's noticing of mysterious color effects during his walk. It's simple. When I was very young, I used to see these colors in the pavement all the time, directly on, not peripherily. The reason is my brother and I were blessed, or cursed, with vision that was so sharp and light sensitive that we were accused all the time of "seeing things". We tested out at 20-05 on the eye charts. Our retinas must have been so stuffed withe rods and cones, I'm surprised they didn't explode. I could see close to 7th magnitude stars. That's all gone now that I'm old. Down to 20-20 with lens implants. Please pardon my self-indulgent nostalgia. MSF >>>
