Why does a golf ball have dimples? They make the ball go further.
Golf balls didn’t always have dimples. The game was invented in Scotland in the 15th century, but it could be connected to a game called paganica that was played in Rome. It could also be connected to a Chinese game called chui. Wherever it came from, the game that we play today was created in Scotland. It had definitely been invented by 1457 because James II, king of Scotland, banned the game that year. It was unbanned by his grandson, James IV, 55 years later. The first balls were probably made of a hardwood like beech, but there is no evidence for that and they could also have been made of leather filled with cows’ hair.
In or around 1618, a new type of golf ball called a featherie was invented. It was made of cowhide and stuffed with goose feathers. The ball was made while the hide and the goose feathers were wet. When they dried, the goose feathers would expand and the hide would shrink, making a very hard and durable ball that was also aerodynamic. Featherie golf balls were very expensive to make and they didn’t last very long. Golf was only really played by wealthy people because of the cost involved.
In 1850, a new type of ball called a guttie was invented. It was called the guttie because it was made from the dried sap of the Malaysian Sapodilla tree, which was called Gutta Percha. It was a hard rubber ball. It could be made perfectly round thanks to the properties of rubber when heated. Gutties were very cheap and they could be remelted if they broke, so they became very popular.
It was thanks to the guttie ball that golfers realized having dimples in the ball was a good thing. A rubber golf ball can get chipped when it is played with and small chunks can be cut out by the golf club. Players thought that a smooth round ball would go further because it would have less wind resistance, so they would heat the gutties and remove the chips. However, through experimentation, it was noticed that the balls with the chips actually flew further and more accurately than the balls without the chips. And thus, the dimpled golf ball was born. Players would chip and dimple their own balls before they played with a knife or a hammer, but it wasn’t long before golf ball companies started to make dimpled balls.
So, why do golf balls with dimples go further than golf balls without dimples? It is because of lift and drag. When a smooth golf ball is hit, it is pushed through the air by the force of the golf club and the air flows around the golf ball. A high-pressure area builds up in front of the ball because the ball is compressing the air in front of it, and the air flows around the sides of the ball and away behind it. The air that passes around the golf ball leaves a wake, just like a ship does through the sea, and that wake is a low-pressure area. This low-pressure area pulls the golf ball and produces drag, which slows it down. The more drag a golf ball has, the faster it will slow down and the less distance it will cover. The dimples on a golf ball affect the drag because they trap a thin layer of air on the sides of the ball, which pushes the air flowing over the ball out a little more, so the wake forms further back behind the ball. This doesn’t sound like much, but it is enough to reduce the drag on a dimpled golf ball by half that of a smooth golf ball.
The second reason is because of lift. A plane’s wing lifts because it alters the speed with which the air passes over the wing, creating low-pressure above it and high-pressure below it. A dimpled golf ball does exactly the same thing, but it doesn’t just produce lift in the one place. As the golf ball is spinning, every dimple produces a tiny bit of lift, creating high-pressure below the ball and low-pressure above it.
Modern golf balls have between 300 and 500 dimples, and a lot of money is put into working out just what shape they should be, how deep they should be, and how many of them there should be. A tiny difference in depth could be the difference between winning a game or coming second. Because of this, golf competitions have standardized rules about what balls can and can’t be used. And this is what I learned today.
Photo by tyler hendy: https://www.pexels.com/photo/titrist-golf-ball-near-golf-hole-54123/
Sources
https://www.scientificamerican.com/article/how-do-dimples-in-golf-ba/
https://en.wikipedia.org/wiki/Golf_ball
https://en.wikipedia.org/wiki/Golf
https://www.wonderopolis.org/wonder/why-are-there-dimples-on-a-golf-ball