Montshire Minute: Flight of the Golf Ball

Originally aired during the week of June 4, 2001

Monday

If you've spent any time on the golf course, you've heard the same advice over and over again. Keep your front arm straight. Keep your head down. And above all else, you've heard that old axiom that seems to be true of almost every sport: keep your eye on the ball! Now, guess what? We're about to make golf even more complicated. Don't get teed off quite yet. You see, the flight of the golf ball is really all about wind resistance, gravity and turbulence. That's because the ball has been specially engineered over the years to travel further and straighter. Will a basic course in golf ball physics help improve your game? Well... no. But it will help you appreciate the aerodynamics the next time you hit that lovely tee shot right down the middle of the fairway. Or slice one into the water hazard.

Tuesday

Throughout the industrial revolution, ingenious Europeans were busy inventing all kinds of things, including a better golf ball. The Scots, who pioneered the game, learned to pack damp wool, hair, or boiled goose feathers into a leather case. When the leather shrank and the drying feathers expanded, the result was a rock-hard ball that really sailed. Before 1850, golf was played with these "featherie" balls and wooden clubs that looked more like hockey sticks. Around the mid-1800s, the gutta-percha ball, often called the "guttie" made its debut. Gutta-percha is a gum extracted from trees in Southeast Asia. After it is boiled, the substance can be molded into a sphere. Golfers began to notice a strange thing with the guttie - well-used balls full of dents and scratches seemed to travel further than brand new ones.

Wednesday

Duffers in the late 19th century noticed that old, beat up golf balls traveled further and straighter than brand new ones. In fact, manufacturers began to make balls with all sorts of dimples and pockmarks on the surface. They knew golfers would do anything to gain an advantage over the course. But why do the imperfect balls travel farther than smooth ones? In flight, the smooth ball has a thin "boundary layer" of air that clings to its surface. This layer creates more wind resistance, and the ball tends to slow down. On the other hand, dimples create more air turbulence around the ball. That forces the air in the boundary layer to hug the ball a little more closely. Instead of flowing past it, the air follows the curvature of the dimpled ball around to the back. The result is: less drag. So the ball goes further.

Thursday

Early golfers didn't know aerodynamics. But they did know that a ball with little dimples on its surface traveled further than a round, unblemished ball. When Tiger hits a tee shot, a very thin layer of slow moving air surrounds the ball. This is called the boundary layer. Air tumbling behind the ball forms an area of low pressure, creating a small vacuum that exerts a drag on the ball. Dimples on the ball's surface create more turbulence in the boundary layer. That forces the air in the boundary layer to hug the ball more closely. The wind resistance decreases, and the ball seems "slipperier." Smaller wake, less drag, and the ball moves right along. A smoother ball, on the other hand, leaves a bigger pocket of low-pressure air in its wake. It creates a real drag, man.

Friday

A golf ball with a dimpled surface will travel further than a ball of the same size that's perfectly smooth. In fact, one researcher found that a round, unblemished ball will travel only about half as far as the dimpled ball. The turbulence created by the dimples enhances the energy of the ball's travel. So it stands to reason that the more dimples, the more distance, right? Well, one can go too far with the dimple thing. We saw it with Shirley Temple. And we see it with golf balls. The June issue of Scientific American points out that if you added more and more tiny indentations to the surface of a ball - let's say thousands - you would be getting closer to creating a smooth ball again. A ball with between 300 and 500 dimples seems to produce the longest distances. Most golf balls today have around 400 of dimples. I didn't count them all - I took Titleists' word for it.