# Why does the Split-finger baseball pitch break?

1. Jul 29, 2012

### TheEtherWind

Supposedly the Split-finger is suppose to 'tumble' or drop as you can find in most references to the pitch. But it's almost impossible to find the answer to "why?" (perhaps because baseball pitchers aren't physicists?) But I have a theory. It involves knowledge on the way the curveball (12-6 curveball) and the knuckle ball are thrown. So I'll give a brief summary of those two:

The 12-6 curveball is suppose to appear to rise to what looks like the 12 o' clock position of a clock (from the pitcher's view) and drop drastically to the 6 o' clock position. The reasoning behind this is pretty solid. Forward spin is imparted on the ball by the pitching delivery, and an area of low pressure is created below the ball, causing it to dive.

The knuckle ball is thrown with the least amount of spin as possible. Some pitchers have been known to throw a pitch 60'6" with only one half of a spin. The point is of course for an unpredictable, sometimes 'wiggling,' motion on the pitch. But to relate this to the Split-finger, the delivery is unique. The desired technique for the knuckleball is to create three points on the baseball where your fingers touch the ball, effectively allowing the pitcher to push the ball with as little spin as possible (usually thumb on bottom left of the ball, two knuckles on the top and ring finger on the bottom right creating an equilateral triangle for pressure points)

Now the Split-finger: my theory is that the way it is gripped; thumb on the bottom, and index and middle fingers spread on the top right and top left of the ball, allows for an almost knuckle ball like release, only with a little bit of backspin. Once the ball has a slight backspin, the bottom of the ball will have a higher translational velocity through the air, causing a greater air drag force and thus imparting a delayed forward spin on the ball. This causes the ball to wiggle a bit through the air (as seen by batters and pitchers) before the imparted forward spin during the moment of little spin, but tumbling at the last instance due to the magnus force of the curveball like spin.

Thoughts? Does anyone find my physics preposterous?

2. Jul 29, 2012

### Danger

I don't find anything preposterous (aside from my in-laws, of course).
My father was a baseball pitcher and catcher back in the day. He literally had his own team, as in it consisted entirely of him and his brothers. (The Almont Tigers; don't bother Googling it, because it doesn't show up. Apparently there was no internet in 1925 when he was playing.) According to him, the effectiveness of a slider, split-finger fastball, knuckleball, and a couple of other things was due to an optical illusion. At major-league speeds (like >90mph fastballs), it's physically impossible for a human batter to track the ball from the pitcher's hand to the plate. While it's possible at lower speeds, it's still difficult. The two approaches that a batter takes, therefore, are to watch the ball as it leaves the pitcher's hand and then extrapolate its path, or to wait until it's close to the plate and then pick it up and track it. Everyone is used to, and expects, a spinning ball. A splitter or knuckleball has no spin. When a baseball with prominent seams is ripping toward you, the lack of rotation makes it look as if it's just hanging in space. It therefore crosses the plate before the batter figures that it's time to swing.

3. Jul 29, 2012

### TheEtherWind

I completely, wholeheartedly disagree with optical illusions being the only thing contributing to the difficulty of baseball pitches. It's even been shown in fluid tunnels... on high speed cam... The magnus force is everywhere.

4. Jul 30, 2012

### Danger

Actually, I retract the previous post... it was the knuckleball that I was thinking of. My memory failed me, and I mistakingly attributed the "spinless" flight to the splitter as well. Now that I've re-read the OP, I realize that I somehow missed the part about the slight backspin on the splitter. The changing rotation due to the seams (there is none during release) is what makes a knuckler weird both visually and aerodynamically.
I was very tired when I answered, but that isn't a good excuse.

Last edited: Jul 30, 2012
5. Jul 30, 2012

### sophiecentaur

But Danger's statement about the batsman's (batter's???) inability to track the ball could still be relevant. There is no doubt about the effect of spin on a ball's path (in every ball game, pretty much) but, if he can't track it, the only clue he will have is the apparent spin as it leaves the thrower's hand. He would need to predict from that information rather than by looking at the trajectory.
It still seems really daft, to me, to have a bat with a cylindrical section, though. It introduces such a high uncertainty into the system. Now, Cricket uses a bat with a flat face, which makes far more sense to me - along with the deck chairs, curly sandwiches, the warm beer and the civilised buzz of approval and restrained clapping. Well played Sir!

6. Jul 31, 2012

### TheEtherWind

I, too, think that a faulty perception on the ball's flight due to rotation can contribute to its difficulty to track. However, I tend to believe breaking pitches actually break...

It's still a mystery as to where the split-finger gets its motion. Too bad there isn't a good reason to do extensive research on the physics behind baseball pitching...

7. Jul 31, 2012

### Danger

Isn't curiosity reason enough?

8. Jul 31, 2012

### sophiecentaur

I think funding is the reason he's thinking of.

9. Jul 31, 2012

### Danger

I hadn't considered it actually costing anything, but I suppose that you're right. Maybe a professional ball team would be willing to invest, on the speculation of learning some worthwhile tricks.