The Question:

A project I am working on for this class requires that I know the exact distance between the grooves on a CD. I've looked everywhere, and I cannot find this information. I was hoping that you could tell me what the distance is, or at least where I could find such information on the Internet.

The Answer:

According to How Stuff Works, a CD is imprinted with pits and bumps which form a track that spirals out from the center of the CD to its edge.

The pits and bumps that make up the spiral track are approximately 0.5 microns wide. Each track is separated by 1.6 microns (millionths of a meter) of space.

—The Fact Monster