My Guess

Resu Eman · Post by **Resu Eman** » Wed Sep 22, 2004 3:22 pm

I have seen this many times! Most recently I have noticed it at an intersection in Spokane, WA after a crew had placed down some striping for a crosswalk. The stripes were not painted, but were a type of decal placed on the road. The halo is caused by tiny beads used to ‘sandblast’ the area to ensure a clean surface suitable for adhesion of the decal. The beads used in this sandblasting are of either a glass or silicone substance, and the residue made for some slippery walking!

The colors are due to the light being refracted from the light source in similar fashion to a prism or a halo, and is similar to those rarely seen circular rainbows, or halos around the sun or moon. In my experience the rainbow halo moved along with me as I crossed the sidewalk. The bright area, I believe, was due to the light being focused into the center of the halo.

Dan Cordell · Post by **Dan Cordell** » Thu Sep 23, 2004 4:31 am

Please keep all discussion related to Dr. Lewin's challenge in this thread.