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THE SCIENCE OF THE SINKERBALL

David Barker

David Barker is a graphic designer at The Exploratorium, a position he's held for 24 years. In that position, he's worked on the design and editorial content for the "Science of Baseball" site, as well as writing several magazine articles on the topic. He's appeared on Bay Area TV station KQED to discuss the physics of hitting and pitching as well; his personal ties with baseball involve "some Little League and some Babe Ruth ball" followed by a long layoff, at which point he found a Men's Senior League in San Francisco and started playing again (P/SS). We talked to Barker about the science of the sinker—and baseball in general.

The Magazine: What is it about science and baseball overall? What makes it such an easy—and for a lot of people who aren't scientists, compelling—study?

Barker: Baseball players are amateur scientists in a way. They go out and experiment. They may not know about Reynolds numbers or Magnus effect or other things that make a ball curve, but they experiment, make variations, and discover things intuitively.

How does a sinkerball work?

A sinker is basically a two-seam fastball; you hold your fingers parallel between the two seams of the ball. The Magnus effect [Ed's note: See diagram above] says that as a baseball spins, it kind of carries the air around with the ball. The seams "grab onto the air" and jet it out. As the air jets in one direction, the ball will go in another. So with a sinker, you want to spin it over the top, because if the rotation has topspin, the air will be jetted backwards and up and the ball is going to head down. Good sinkerballers put an unequal pressure on the index and pointer fingers, depending on which way they want the pitch to break. Index finger pressure makes it go left (for a righty) and pointer pressure makes it go right.

What makes it so effective for pitchers?

A good sinker is just a good pitch, first of all. It can break 6 to 12 inches. It usually breaks late, and seems to slow down on its way to the plate. Because it breaks late and it breaks down, batters don't hit it squarely. They hit it low, off the sweet spot. It makes the ball feel "heavy," which is how people usually describe hitting a sinkerball pitcher. Catchers also describe it that way because of the late break; you tend to catch it in the heel of the mitt, rather than the main spot. It makes the ball feel heavier. If you're getting a not-great swing on a ball coming in low, it's likely going to be a ground ball. As a pitcher, you're told from Little League up that if you can't throw 95 or above, you better be able to keep it on the ground. Ground balls = double plays and those = a pitcher's best friend. If you can throw it well, it's a great pitch.

Does the climate of Arizona benefit Webb at all?

I'm sure it does, but I don't know how much. My team is the Giants; when they go to AZ for spring training, you see it's harder for the pitchers to get a break, and the environment benefits hitters. The ball tends to carry farther. So if you're a good sinkerballer and can get a lot of balls on the ground instead of in the air, that's going to be beneficial in Arizona.

As Buster Olney profiled Webb, he was going through a little bit of a rough patch. What are the dangers of the sinkerball?

A lot of sinkerball guys will say, "I just throw it down the middle and let the sinking take care of the effect." The danger with that is, if anything is off and the ball's not sinking, it's right there in the hitter's wheelhouse. Right now I think Webb—he's still a great pitcher—he could be having issues with release point, topspin, or even velocity; if it sinks too much or too fast, you're losing control. If something is off with your mechanics, the ball's right down the middle.