|MadSci Network: Physics|
A perfectly smooth ball cannot be made to curve. The stitches on a baseball disrupt the airflow around the ball, creating forces which move the ball out of a linear path. Golf balls do not hook or slice because of their surface, but rather because of the angle at which they are struck by the club. That is why the golfer's swinging technique is so important. What the dimples on a golf ball do is create small pockets of air around the ball, decreasing drag by improving what is known as "laminar flow", essentially greasing the ball's path through the air.
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