How many RPMs does a CD spin at?

It depends. The old phonograph records spun at a constant speed (for example, 33 or 45 revolutions per minute).

That made it easy to make a turntable to handle them, but it meant that the music recorded near the outside of the record had better sound than the music recorded on the inner grooves.

A CD solves this by varying its speed as it plays, so that the speed of the bumps below the laser beam always stays constant.

That means that as the CD begins playing, the music on the inside groove (yes, the album starts on the inside and works its way toward the outside) sounds as good as the music near the outside.

On the inside grooves, a CD spins at a rate of 200 revolutions per minute and gets as fast as 500 rpm as the laser beam approaches the outside edge.