The Blue Jays just got better. This is now a common weekly theme for the team. First it was Josh Johnson, Mark Buehrle, and Jose Reyes, then it was Melky Cabrera, and now R.A. Dickey is headed to Canada. They've lost a number of prospects to get to this point, but the organization is still full of young high-upside talent. I could go on about how the Blue Jays have rebuilt their team, but this post is about their newest knuckleballer.
If you've ever heard a baseball announcer talk about the knuckleball, you've probably heard that it's random. They say it "dances" and "flutters" in different directions as it approaches the plate. They say the perfect knuckleball has no spin at all. They say that pockets of air and wind create the erratic movement. Not that wind or air pockets don't exist inside a dome stadium, but the forces are definitely limited, even if the roof is opened. So why would the Blue Jays pay the Mets two top prospects to acquire a pitcher that will start half his games inside a dome?
I've read quite a bit of speculation on this topic, mostly from fans, and there are numbers to prove Dickey has both succeeded and failed inside domed ballparks. My real question is whether or not the physics are right. Does the knuckleball really rely on the environment to create it's erratic movement?
The truth is, the knuckleball does not "flutter", nor does it depend on wind or air pockets. When we talk about pitching, most of the physics that we discuss is centered around the Magnus Effect. Depending on the angle of spin, a low and high pressure force will surround opposite sides of a baseball, causing a fastball to fight the effects of gravity ("rising" action), and a curveball to have a "tumbling" action. Because there is little to no spin on a knuckleball, the Magnus Effect is nearly absent, and the science behind the knuckleball is fairly new.
Back in the 1970's, a study by Robert G. Watts and Eric Swayer was done to better understand the effects on a knuckleball inside a wind tunnel. They found that the movement of the pitch was largely dependent on the angle of which the ball was thrown. The seams of the baseball could be oriented in such a way to create what's called boundary layer separation. If you're unfamiliar with the term or interested in the physics here, I recommend you read up on Freddy Garcia's "Swing" Ball and the accompanying links. Basically, the seams of a knuckleball create asymmetric flow separation. The air surrounding the sides of the baseball, where the seams are present, rapidly cuts the air surrounding it, creating a turbulent boundary layer. The sides of the baseball without the seam flow more smoothly around the air as it's moving, this creates laminar air. The differences in pressure created by the laminar layer of air and the turbulent layer create the forces necessary to move the knuckleball in a certain direction.
When Watts and Sawyer completed their experiment, they believed that a knuckleball that had little spin would have the erratic "dancing" movement due to the seams changing directions while spinning slowly. Thanks to new PITCHf/x data, earlier this year, Professor Alan M. Nathan of the University of Illinois studied the knuckleball movement from both Tim Wakefield and R.A. Dickey. The data calculating pitch break showed that the knuckleball did not have the erratic "fluttering" movement that's commonly associated with the pitches' success. Instead, he attributed the myth to the randomness to which the pitch moves. In other words, the the idea that a knuckleball moves in different directions during it's movement is a myth, the pitch has the same smoothness in trajectory of any other pitch. He surmised that the idea of fluttering movement was likely due to the random movement of different knuckleballs, as first found in work done by John Walsh of The Hardball Times.
This isn't to say that the environment plays no part in the movement of a pitch, but the movement of a knuckleball is nearly fully dependent on the orientation of the seam, the spin angle, and the rotation rate. In theory, the air inside a domed stadium should have no significant effect on R.A. Dickey's knuckleball. Unfortunately, the Yankees now have to face a very difficult pitcher to hit.