1.1 A Chance Observation
In a sunny parking lot its easy to observe strange patterns of highlights apparently moving across the car hoods. Rows of tiny parallel scratches in the paint behave as specular line-scatterers. If the angle between the observer and the surface is changing, these scratches produce patterns of reflected sunlight that appear to move across the hood. On one occasion I noticed a particularly striking example. The highlights on a black car hood were not just highlights, they were large images, and they appeared deep within the surface. They also had a distinct structure: close-spaced radial filaments surrounding an array of whitish patches. After some time in observing these, the nature of the shapes suddenly became clear. They were images of a lambs wool polishing mitt, complete with matted fibers in the center, straighter fibers forming a radial halo, and with the glowing shape of a human hand visible in the matted fibers. Even more intriguing, most of these patterns appeared to float many centimeters deep within the car hood. Apparently they were created as the hood was polished by a gritty polishing-mitt, and the mitt produced a large number of microscopic, curved, and somewhat parallel scratches in the paint.