A Straight Dope Classic from Cecil's Storehouse of Human Knowledge

Why do golf balls have dimples?

June 11, 1993

Dear Cecil:

I have read your column ever since my then-13-year-old daughter pointed out your discussion on the subject of breaking the penis. The years of keeping track of you have been very entertaining and mildly informative. I feel I owe you one. Perhaps the following will satisfy that obligation.

You are undoubtedly aware that the Washington Post prints a poor imitation of your column called "Why Things Are" by Joel Achenbach. If you are the least bit human, you would welcome the opportunity to nail the bastard. Herewith, two possible approaches.

The first one is easy. Achenbach's explanation of why golf balls have dimples (enclosed) is so full of errors and so clearly down your street that you will have no trouble slaughtering the bum.

The second is tougher but potentially more rewarding. We are, after all, dealing with a fellow who begins a paragraph, "Me, I don't read," and ends it claiming that The Brothers Karamazov is " … thematically the same story as Return of the Jedi."

This angered me so much that I have been trying to write my own rebuttal for three weeks. The approach I was working on was based on Georges Polti's classic The Thirty-Six Dramatic Situations.

I had no trouble pointing out that the theme of The Brothers Karamazov is Polti's #3, Crime Pursued by Vengeance. Nor did I have trouble with Return of the Jedi, clearly Polti's #8, Revolt.

But the job turns out to be harder than I had counted on, largely because the story line of Brothers is so complicated. Perhaps you might care to give it a shot and use it as an excuse for blasting the twit.

Cecil replies:

You know, Bill, we had a message along these lines not long ago on the Straight Dope message board. It went like this:

"How do you put dimples on a golf ball?"

I wrote back:

"Tickle its little feet."

Listen, _I_ thought it was funny. But back to Joel Achenbach.

Joel is a good fellow, and he will surely get the hang of this know-it-all business eventually. [Actually, maybe he won't, because I understand he has now stopped writing his column. But it was 1993 when I wrote this.]

Joel's explanation of golf ball dimples isn't wrong, but it isn't as clear as it might be.

He writes, "Increased turbulence [due to dimpling] mean less drag on the surface of the ball. … The backspin imparted by the club face is what gives a ball lift, but without dimples the air will `cling' to the ball, and will flop to the ground."

Now, _I_ know what's he talking about. But I can see where the ordinary citizen might be confused.

So let's turn to the bookshelf. A few volumes to the left of Joel's two epics we find ... well, I guess Aquinas isn't the ideal source on this. Here's something more to the point: Theodore Jorgensen's The Physics of Golf.

Jorgensen patiently explains that there are two things that help a golf ball travel great distances: (1) backspin, and (2) dimples.

You know, I can't help it, every time I see that dimples thing I want to work in a Shirley Temple joke. Come on, Cecil, get a grip.

Backspin gives the ball lift. This is due to the Magnus effect, which is a special case of the Bernoulli principle, which is what enables airplanes to fly. In other words, this has major engineering consequences, so let's not let our attention drift.

The spinning ball drags a layer of air around with it. On the top of the ball, the dragged layer is moving in the same direction as the air streaming past. On the bottom of the ball, the dragged air is moving OPPOSITE the direction of the air streaming past. (One hopes Mr. Slug's cartoon makes this clear.)

So the air on the bottom slows down. The Bernoulli principle tells us that slow moving air has higher pressure than fast moving air. The difference in pressure forces the golf ball up.

Now to the dimples.

A smooth ball flying through the air drags a good-size wake (region of turbulent air) behind it. This wake slows the ball down.

Dimples grab the air streaming past the ball and make it follow the ball's surface more closely. That decreases the size of the wake behind the ball. The smaller the wake, the lower the drag and the farther the ball goes.

Having perfected our understanding of the physical world, we now turn to literature.

Joel's reference to Return of the Jedi and The Brothers Karamazov gave me pause, too.

However, rather than waste a lot of time trying to trying to explain what The Brothers K was really about, which sounds perilously close to what I used to write in college blue books, I called up Joel and asked what the hell he had in mind.

Here's his explanation: he got through the first 60 or 70 pages of The Brothers K and noticed that the brothers seemed to have problems with their father. So, after a manner of speaking, did Luke Skywalker in Jedi. (His father, you'll recall, was Darth Vader. Many of us can relate.)

Both books also had to do with good and evil and stuff like that. Ergo, they are thematically equivalent.

OK, so it's not what you'd call a closely reasoned argument. But come on, says Joel, it was mostly a joke.

Joel, sez I, in this business you make jokes at risk of your life. This guy Balderston has been stewing about this for three weeks. Just be glad the Post has guards at the doors.

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