New Ball WC 2010

Why are there dimples on a golf ball? Why do the stitches on a baseball affect the way it moves when it is thrown or batted?
Reynolds numbers ( density of the fluid ie; air) , Magnus forces, velocity of the soccer ball etc. A totally smooth sphere will 'knuckle" due to asymmetric forces at the laminar flow boundary. The picture of the ball shows very shallow 'seams'. This ball will move in unusual ways in flight vs. the ball with more seams that are deeper.

You will see some very strange replays at this World Cup!!
Coincidently, an excellent book is The Physics of Baseball by Dr. Robert K. Adair, Harper & Row 1990. In a very real sense, baseball is played the way it is because there are raised stitches on a baseball.