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Hi, I'm Marshall Brain. If you've ever looked at a golf ball, you know that it has dimples, but why is that? The reason why golf balls have dimples is a story of natural selection. Originally, golf balls were smooth, but golfers noticed that older balls that were beat up with nicks, cuts, and slices in the cover seemed to fly further. Golfers, being golfers, naturally gravitate toward anything that gives them an advantage on the golf course, so old beat up balls became standard issue.
At some point, an aerodynamicist looked at this problem and realized that the nicks and cuts were acting as turbulators. They induce turbulence in the layer of air next to the ball known as the boundary layer. In some situations, a turbulent boundary layer reduces drag. A sphere happens to be one shape that gets a big boost from turbulators. The dimples that we see today are simply organized, optimized turbulators on the surface of the ball.
If you want to get a little deeper into the aerodynamics, there are two types of flow around an object. There's laminar flow and turbulent flow. Laminar flow is good. It has less drag, but it's also prone to a problem called separation. Once separation occurs, you get a lot of drag because of eddies that form in the gap. Turbulent flow has more drag initially, but it's also got better adhesion. It, therefore, is less prone to separation.
If the shape of an object is such that separation occurs easily, as in a sphere, it's better to turbulate the boundary layer at a slight cost of increase drag in order to increase adhesion and reduce eddies, which means significant reduction in drag. Dimples on golf balls turbulate the boundary layer and help the ball fly farther. A golf ball with dimples can fly twice as far as a smooth sphere of the same size and weight. Do you have any ideas or suggestions for this podcast? If so, please send me an email at Podcast@HowStuffWorks.com.