In golf, the most important thing is how far your ball goes. It’s your score, regardless of how good you are.
If you have a rather unusual golf ball, it makes sense to design it so that it will do well on all kinds of courses. So they make balls that are solid and so won’t go as far through the air but will still go very far on the right course. And they make balls that bounce a lot more than solid balls and be the same distance through the air. And then there are dimpled balls.
Most golfers know dimpled balls bounce worse than solid ones, but not why or how much worse. When I first started playing golf I had no idea why dimpled balls were bad; I just knew they were. If a dimpled ball hit me in the chest I would catch it and try to hit it again with my other hand instead of taking it for a putt.
The reason dimples in golf balls cause problems is that there is nothing special about where dimples are on the surface of a golf ball—or any other solid object. If you put a hole in one into the middle of a tennis ball, the tennis ball will fly off at the same speed as before. If you put a
Golf balls have dimples. You always thought they were smooth and round, but it turns out they have small air pockets inside them, which act like small holes to let hot air escape as the ball is struck.
Dimple golf balls are an astonishingly bad idea for all sorts of reasons: if you don’t play golf, you’re not going to notice that golf balls have dimples; if you do play golf, you can hardly avoid hitting them; and in any case, since the dimples are very small, a golfer shouldn’t have to deal with them at home.
Here’s another reason dimples are a bad idea: if you hit the ball hard enough, it will bounce back at you. The dimple model would predict that the ball would bounce back in some particular direction. It doesn’t.
In some ways, golf balls look just like regular balls, but they have a lot of little holes in them.
Why do they have holes? The short answer is that the dimples keep golf balls from bouncing back and forth too much. That way, it’s easier for the ball to fly straight. If the ball bounces around on its own, the harder it is to hit straight.
The long answer starts with how a golf ball behaves when you hit it. If you hit a ball in the air at exactly 90 degrees from the ground with a bat or club, it will roll through the air in a nice figure eight pattern. The pattern is called an ellipse and looks something like this:
The ball rolls as if it had pneumatics inside, which means that it does not roll on its own but has to push itself forward with each bounce. Just like a cat walking across carpet – except that when cats walk across carpet they use their fur to push themselves forward. Golf balls have dimples so that they can’t roll too much during flight and instead roll in the shape of an ellipse.
The dimple on the golf ball is a very clever piece of design. It works to increase the aerodynamic lift of the ball and to decrease drag. It does both by producing an increased pressure distribution on the upper surface of the ball, thus increasing the lift and decrease the drag.
The dimples are made in a series of steps, beginning with a die that creates a flat surface. A stamping machine then stamps out multiple cavities from this surface. The cavities are then filled with molten lead or tin and allowed to cool.
The result is a ball that has a very slight edge in lift and run; it flies straighter than one without dimples and it carries much less drag.
Golf balls are made of vulcanized rubber, which is soft and flexible. But it’s not as flexible as the air inside them. The air presses on the outside of the ball, compressing it a little bit—this is known as pressure-induced flow. The pressure-induced flow can make the ball rise or fall slightly. If it rises, it will tend to roll to one side; if it falls you get a hook (the ball hooks over).
The dimples in golf balls were originally designed so that they would just pop out when hit by a club. Because they were pressed into the ball by the air, they distorted its natural curvature, making it more likely that it would roll away from you.
A golf ball is a sphere with a dimple in the middle. Where does the air come out? It comes out at the bottom, of course, and that is where you put your hands to hit it. But it doesn’t come out straight down like a fountain. Instead it shoots out in a high arc
It is true that a golf ball has dimples, but you take your eye off the ball in flight and the dimples disappear. We see the ball without dimples because those dimples interfere with our vision.
It’s not just golf balls. In fact, it’s not just any object that has dimples, but only a few kinds of solid objects. And you can tell them apart by how they behave when you let go: if two objects have the same dimple pattern, they will always have the same flight trajectory; if they have different pattern, their trajectories are likely to diverge as time passes.