Sunday, October 5, 2008

Aerodynamics of a Baseball in Flight

It's the MLB Postseason! As the days grow shorter and the leaves turn, how can anyone think of anything but baseball ...

Nine inches in circumference. Weighing in at about five ounces. Made of cork wound with woolen yarn covered with two layers of cowhide stitched by hand precisely two hundred sixteen times… Every baseball used in Major League play today is made to these specs.

Over the years there have been claims of juicing, concerns about the effects of altitude and humidity, and changes to the cork in 1910, the yarn in 1920, and a switch to cowhide from horsehide in 1974. But every ball has been manufactured to exact specifications since 1874. And every ball is still handstitched – currently at the Rawlings manufacturing facility in Costa Rica.

The real news relating to the ball itself occurred in 1920 after Yankee pitcher Carl May’s fastball bounced off Cleveland Indians batter Ray Chapman’s skull with the resounding crack of a pitch well hit. Chapman reportedly took two steps toward first before dropping to the ground - skull crushed - to die twelve hours later.

Ever since, dirty, misshapen, barely discernible lumpy balls rushing toward the batter have been outlawed. Only spotless, flawless baseballs can remain in play. The designation of “flawless” isn’t left up to the perception of the batter or the pitcher. The umpire inspects each ball frequently. When he decides one is unfit, he puts a new one into play.

But a new baseball is a gleaming white orb of perfection that’s slick to the touch. The cowhide ensures that. For a pitcher to get a good grip, something has to be done to make the ball less glossy. Spit, nicks, gels — any tampering or foreign substance altering the appearance or aerodynamic properties of the ball is illegal. Something was needed that could make the ball uniformly easier to handle — without amending the ball in any way.

An ex-player and manager named Lena Blackburne was the one who solved the problem in the 1930’s with his discovery of the perfect mud. He harvested it from a still-secret location in New Jersey until his death. The location was passed on and this ‘magic mud’ that doesn’t discolor, soften, or stink up the ball has been rubbed on every ball in Major League play before every game ever since.


But any batter can tell you that seeing the ball and hitting the ball are two different things. It’s not enough to figure out the probable pitch racing toward you. You’ve got to get the bat in the precise position needed to connect solidly.

It’s a humbling experience and today with two balls, two outs, and men on first and second, there’s now as much pressure on the batter standing ready at the plate, as there has been on the pitcher all day.

On the mound, the pitcher nods at the catcher’s signal and makes the throw.
The batter steps into his swing. The crack of the bat reports a solid hit as the left fielder races to make the catch.

No one has control of the ball now.

Now that it’s airborne air temperature, the amount of moisture in the air, wind and wind direction all come into play. And that’s not all. The speed of the bat when it met the ball, the angle of the bat on the swing, where along the bat the ball was hit – all of these matter, too.

How much any of it matters has been the subject of much debate. So much so that in 1987 President of the National Baseball League, Bart Giamatti, named Dr. Robert K. Adair Physicist to the National League. Adair’s wonderful book, The Physics of Baseball, resulted. Its detailed scientific and conversational explanations cover the effect of factors ranging from the length of time a batter has to reach a decision on a pitch and what a pitcher can do to minimize that time, to the optimal weight of a bat.

It’s safe to assume that batting and pitching coaches are familiar with the theories in this seminal work and the works that have followed. It might even be safe to assume that an individual pitcher or batter is familiar with these theories or, through trial and error, has come up with ways to use them to his benefit.

Every player out there has a vested interest in the behavior of a ball in flight. Their success depends upon their ability to manipulate the aerodynamic properties of the baseball to their advantage.


Aerios: concerning the air. Dynamics: force. The Ancient Greeks coined the term aerodynamics for their study of forces and the resulting motion of objects through air. Today, all the attention a pitcher pays to the placement of his fingers in relation to the seams is done to take advantage of the aerodynamic properties of a ball in flight. Because the seams are the only raised portion of the ball, a baseball made to spin as it moves alternates its smooth and raised surfaces. The cowhide – cut in two peanut-shapes – is smooth. The 216 stitches used to hold the cowhide together, a raised saddle pattern, or double horseshoes, on the ball. These smooth and raised surfaces are the cause of the ball’s performance as it responds to the effects of Lift, Thrust, Drag, and Gravity.

Daniel Bernoulli’s work with fluid mechanics in the 1700’s provides the basis for many of the concepts used in the study of aerodynamics today. According to Bernoulli, an increase in the speed of the fluid occurs in concert with a decrease in pressure or a decrease in the fluid’s gravitational potential energy. That’s why, for a baseball, it’s not only the accuracy and strength of a pitcher’s arm that decides the ball’s path. It’s also the orientation of the stitches as the ball moves through the atmosphere.

But a baseball doesn’t create aerodynamic forces in the same way as the wing on an airplane or other airfoil. The spinning of the ball and the raised surface of the stitches create a whirlpool of rotating air around the ball. This exerts pressure and the ball moves in the direction of least resistance. This Magnus Force is what causes a perfect curve ball to curve right at the plate as the disequilibrium reaches it’s maximum at the end of it’s seconds-long, sixty feet six inch journey.

A successful pitcher knows how to use his arm and wrist to optimal effect. He also knows throwing the ball with the proper speed and arm movement isn’t enough. If his fingers aren’t positioned correctly, there’s no way he can count on the ball to cross the plate where he wants. It all comes down to where he positions his fingers on the ball.


Throwing a curveball? The index and middle fingers are positioned so the middle finger is on the right horseshoe seam with the index finger between the seams. It’s released with the wrist angled so the thumb is on top to give the ball a downward spin - top to bottom. With the right flick of the wrist and a pitch speed of 70 mph or more the ball will curve just as it reaches the batter. How much it curves is determined by the extent of the disequilibrium created by the seams as the ball spins on the way to the plate. If a righty pitcher facing a righty batter wants a big break to the outside, he’ll create a large area of disequilibrium by orienting the ball so four of the seams are rotating toward the batter on the way to the plate. If he requires a smaller curve, he’ll orient the ball so only two seams rotate toward the batter.

For the four-seam fastball essential to the arsenal of every Major League pitcher, the index and middle finger are placed across one side of the horseshoe portion of the seam as it’s thrown at full velocity. The ball rotates bottom to top.

Prefer a Slider? That’s thrown with the index and middle finger close together and off-center as they run down the length of a horseshoe portion of the seam. The tight spin apes the fastball but it has a striking late break down and away when thrown by a righty pitcher to a righty batter. The pitcher creates the spin with a downward pull at release but the aerodynamics of the seams - not the action of the wrist - causes the spin. It’s the off-center spin that causes the ball to break.

You don’t see many Knuckleballs. They’re difficult to learn, locate — and hit! The pitcher puts the tips of both his index and middle fingers on one side of the narrow portion of the seam. He uses his thumb on the bottom of the ball to form the secure grip he needs to hurl the ball. The Knuckler is pushed straight out at release, with as little spin as possible. Because there’s virtually no spin, the wind pushes the ball around on its way to the plate.


The batter is intent on reaching first as the pitcher conspires with the catcher to keep him from doing just that. With absolutely no control over the ball, the batter will shrink his strike zone to maximize the number of pitches he receives. He’ll also do what he can to perfect his stance. Ready his bat. None of which will matter if he can’t get a sense of the ball rushing toward him. A sense of what the pitcher has done with his grip on the ball upon release.

Since a pitcher does his best not to betray his choice of pitch with the position of his arm or the type of motion he uses, that leaves the batter to read the pitch while it’s on the way. He doesn’t have much time. A fastball takes just seconds to reach the plate. A curveball slightly longer. The sooner he can identify the pitch from the pattern of seams and smooth surfaces streaking toward him, the better his chances of getting a clean hit.

If the ball is rotating top-to-bottom and feels slower than a fastball, the batter will prepare for a curve. Rotating bottom-to-top? He’ll watch to see if it’s six-to-twleve or four-to-ten as he readies himself in the seconds before the fastball reaches him. A slider will come in like a fastball, but the orientation of the stitches as it spins is different. And a knuckleball? Few pitchers throw it. When he’s facing one who does the batter’s decision to hit or hold will depend on the count and whether or not it looks like this particular pitch is headed for the strike zone.

Some batters have described the ball as looking big as the moon as it nears the plate. Others have described it as coming at them in slow motion. More often it’s just a fast moving streak with alternating seams. No matter what, the batter has milliseconds to use what he can discern of the ball’s movement to reach his decision about when to swing. Or whether or not to swing at all.

The lowly baseball.

Not very impressive.

Until it’s in flight.


Carol Pentleton said...
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Carol Pentleton said...

The aerodynamics of a baseball in flight is even more interesting to the small fraternity of amateur (in the best sense of the word) baseball players who play a variety of the game known as vintage baseball.

Operating under various sets of 19th century rules, teams typically use only one baseball per game. No matter what happens to that ball, it is the only one used.

Should a ball be hit into a stand of trees, everything stops, and both teams, along with any spectators, comb the woods until the ball is found.

By the end of the game, the cover is usually cut, the stuffing is hanging out, and the stitching has loosened to a degree that would induce cataplexy in Major League umpires.

I don't know whether any vintage league players throw knucklers, but the one-ball rule seems to introduce an additional element of chance no longer experienced on a regular basis in MLB.

Gina Hagler said...

Do the pitchers maintain enough control to throw curveballs by the last innings?

Carol Pentleton said...

I'm not sure how much vintage league pitchers rely on the curve. In any case, command of any pitch might be a bit iffy once the stitching comes loose and the stuffing starts to peep out!

Gina Hagler said...

Good point!