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

Wait, what?

[pwnyxpress]

Guy 1: We have amazing technology that allows us to know EXACTLY what happened.

Guy 2: Awesome, so we don't have to rely on humans in those really close calls.

Guy 1: Well...not really...

Guy 2: ?

Guy 1: We're only going to use it to record pitches...

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.

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.