The Physics of the Knuckleball

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."

Comments

Naming the followers

[Zephyn]

Back in the late 80's/early 90's the Mets had a very successful pitcher named David Cone, and his fans were known as Coneheads... and sometimes dressed the part.

Now for R.A. Dickey.... hm.... I think we'd better focus on his pitching style instead of his name. Let's go with Knuckleheads.

Hockey goalies

[SoupGuru]

I'm a hockey fan and it's not unusual to see goalies get beat by what seem like simple shots. Someone skates over the blue line into the offensive zone and shoots an average wrist shot towards the goal. It's a routine save for the goalie under normal conditions... a really low percentage shot. But if the shot gets tipped, even ever so slightly and even a long ways away from the goalie, the goalie can have trouble with it.

It's because the goalie reads the shot not by plotting the course of the puck but by seeing so many shots that by the motion of the shooter's stick and body language, he already knows where the shot is going and reacts accordingly. A tip, even a foot away from the shooter's release, turning a 20 foot shot into a 19 foot one, throws it all to the wind. You'd think it would give the goalie enough time to make the save but he's already moving to the top right corner before he realizes is going bottom left.

I'm sure it's the same in baseball. 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. When a knuckleball comes their way, there's nothing to read because even the pitcher doesn't know where it's going.

Re:Hockey goalies

[artor3]

I'm sure it's the same in baseball. 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. When a knuckleball comes their way, there's nothing to read because even the pitcher doesn't know where it's going.

You're close, but not quite right. Batters can pick up some aspects of the pitch from the delivery, especially at lower levels of play, but pitchers try very hard to avoid "tipping their pitches" in such a manner. So in the majors, what batters really look for is the spin of the pitch, judged by looking at the conveniently bright red seamsw. Since major league pitchers throw balls with 2000+ RPM of spin on them, the seams will mostly be a blur, except for key exceptions. For example a 2-seam fastball will appear to have two pinkish vertical stripes on it. On a sinker, those stripes will be tilted. Breaking balls look like they have dots (as the axis of rotation passes through or near the seam), with the dots in different places depending on the type of pitch. Of course, you only have about 200 ms to pick up the seams. On a 3" diameter circle. From fifty feet away. That sharp vision and quick thinking is probably the number one element in setting apart top hitters.

On knuckleballs, there's nothing to read. Which means that major league hitters need to forget about their standard approach. All their skills and practice count for nothing, and they're forced to just hack away at it the way you or I would (albeit with a swing that won't draw laughter from the crowd).

Been there, done that!

[Takionbrst]

Six years ago, from a professor at my alma mater: http://farside.ph.utexas.edu/teaching/329/lectures/node45.html 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!).

Nice to see skill over brawn

[msevior]

It's nice to see the pracitioner of a fine skill be successful where traditionally the best pitcher is the one who can throw the fastest (under control of course).

A similar scenario happens in cricker where a great spin bowler can dismantle a team. Until the 1990's bowling in cricket was dominated by extreme speed where the best bowlers could bowl at over 150 Km/Hr. Along comes Shane Warne, considered the 2nd most influential cricketer in the 20th century who bowls at less than 100 Km/Hr but with a wicked spin and fantastic control.

Check out the "Gatting ball" video below for a delivery of pure beauty.

http://www.youtube.com/watch?v=rOVei8iTyM8

It was Warne's first Test Match delivery in England!

Re:Wait, what?

[sjames]

Beyond the fact that many baseball fans LOVE to disagree with the ump, part of the game includes pitcher, catcher, and batsman working out where the ump is seeing the strike zone that day. Meanwhile, the pitcher tries to slowly expand the ump's strike zone, the catcher tries to frame the pitch as a strike and the batsman tries to crowd the plate and shrink the strike zone. The pitcher then tries to brush the batsman back. All of that gameplay is lost is a computer and cameras call the balls and strikes.

Beyond that, how will the computer decide if the batsman swung or not? We don't even have official rules for that.

I don't think it would really be the same game without the ump making the call.

What I do think is good is the umps themselves reviewing footage, their call, and what the computer says during the off season.

Mod down; wrong

[gottabeme]

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.)