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## The Physics of the Knuckleball87

snoop.daub writes "R.A. Dickey, pitcher for the New York Mets, has been in the news this week after two dominant pitching performances in a row, holding opponents to one hit in each of the games for the first time since Dave Stieb did it in 1988. He has taken over as the league's only knuckleball pitcher after Tim Wakefield retired last season. But just what is it about the knuckleball that makes it hard to hit? Conventional wisdom has it that the lack of spin on the knuckleball causes it to move in completely unpredictable ways, even changing directions in mid-flight. In the last few years, there has been a lot of good science done to understand baseball pitch trajectories, and a few months ago Prof. Alan M. Nathan showed that knuckleballs aren't really so different from other pitches. It turns out that the same 9-parameter equation that can be used to describe other pitch trajectories applies just as well to the knuckleball. The difference appears to be that, like in a chaotic system, knuckleballs depend sensitively on the initial conditions, so that small changes can cause randomly different forces at the start of the pitch which determine the resultant trajectory. Much of this and similar work depends on the Pitchf/x tool, which has recorded the complete trajectory, spin angle and spin rate of every MLB pitch since 2007! Baseball really does have the best sports stats geeks."
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## The Physics of the Knuckleball

• #### stats geeks (Score:3, Informative)

by Anonymous Coward on Wednesday June 20, 2012 @06:19PM (#40391699)

Baseball really does have the best sports stats geeks.

Meh. You've clearly never met any cricket fans.

Just ask one to describe the Duckworth-Lewis method of calculating scores for a rain-interrupted match.

• #### Been there, done that! (Score:5, Informative)

on Wednesday June 20, 2012 @06:39PM (#40391867)

Six years ago, from a professor at my alma mater: http://farside.ph.utexas.edu/teaching/329/lectures/node45.html [utexas.edu] This being slashdot, I didn't RTFA but the author seems to come to the same conclusion that Fitzpatrick did. Incidentally, if you ever need to know something about physics, chances are this fellow has excellent lecture notes posted on his website covering the topic (in hyperlinked html, pdf, and even a git repository for the latex code!).

• #### Mod down; wrong (Score:5, Informative)

on Thursday June 21, 2012 @12:22AM (#40394479)

Batters don't have time to judge the ball's trajectory itself so they rely on the pitcher's delivery to tell them where the pitch is going.

Yeesh. You're just plain wrong. At least you were nice about it. But you're just wrong.

Hitters watch the pitcher's release point and try to "pick up" the ball as soon as it leaves his hand. If a hitter doesn't visually lock onto the ball as soon as it leaves the pitcher's hand, he probably won't hit it--at best, he'll foul it off.

Pitchers generally try to maintain a consistent release point; it makes it easier to develop fine control and helps prevent injury. The release point can be the same, yet the pitch location can be all over the place.

I haven't even mentioned spin yet. A four-seam fastball and a two-seam fastball behave very differently, yet they begin the same, coming straight out of the pitcher's hand with backspin. If the hitter doesn't read the spin, he probably won't hit it well. A changeup or a splitter are even more different than those pitches, yet they also come straight out of the pitcher's hand with backspin. The hitter must see the seams of the ball as it's in flight in order to recognize the pitch type and be able to estimate its trajectory. And I haven't even mentioned curveballs and sliders yet.

I'll never forget the first time I recognized a slider while hitting. I remember seeing the dot right after the ball left the pitcher's hand. I had seen enough of them on TV replays while watching games that my mind recognized it quickly, and I knew the pitch would be a ball, low and away. If I hadn't seen the dot, it would have looked like a fastball down the middle, and I would have swung and missed. And all of that visual and mental recognition and processing has to happen in a fraction of a second. It was exciting! (If only I had had my vision corrected years earlier! I didn't realize I was capable of seeing the spin on the ball.)

As for knuckleballs, it's an exaggeration to say, "even the pitcher doesn't know where it's going." Not that a pitcher has fine control over it, but if it were as wild as you suggest, it would be useless. If you can throw a baseball already with decent accuracy, you can try a knuckleball for yourself and see. It's not that hard to get it in the strike zone if you're a decent pitcher.

Yes, I used to play baseball, both pitching and hitting.

(As an aside, while you might know a lot about hockey, please don't speculate so authoritatively about something you don't actually know about. It's a shame to see a post that's just plain wrong modded +5 Insightful.)

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