Spinning (Backspin) Baseball in a Water Tunnel
Note how the Flow Reacts When the Dye Hits the Baseball's Seams

Just before the start of the American Civil War, a New England boy named Arthur Cummings became fascinated with a newly popular game called "baseball." On the beaches near his home he imitated (copied) his heroes by endlessly pitching clam shells. Soon he discovered that by holding and throwing the shells in a certain way, he could make them curve. Arthur, nicknamed "Candy," by this friends, daydreamed that one day he would play with his heroes and make a baseball curve like the clam shell.

In 1867, 18 year old Candy Cummings, pitcher for the Brooklyn Excelsiors baseball team, tried out the pitch he had been perfecting in secret for years. He "wound up" and threw, snapping his wrist as he released the ball. He watched with delight as the ball made an arch and swept past the swinging batter into the catcher's glove. STRIKE! Again and again throughout the game, Cummings made batters "fan the air" (strike out) swinging at his secret pitch. Today, in the Baseball Hall of Fame in Cooperstown, New York, there is a plaque that reads: Candy Cummings, inventor of the curve ball.

Yet for more than 100 years after Candy introduced his new pitch, people have doubted their eyes. Does a baseball really curve or is it an optical illusion (a trick to the eye)? Several times through the years people tried to prove if the ball really curved.

First, two large hoops were placed between the pitcher's mound and home plate. The ball was pitched through the hoops. The ball curved past the first hoop and into the second. The ball seemed to curve but was still doubted by many. In 1941, both Life and Look magazines used stop-action photography to see if the ball really curved. Life concluded that the ball did not curve; Look determined that it did. It wasn't until 41 years later, 1982, that the Massachusetts Institute of Technology came out with the final word: a curve ball does curve, and can be explained by the laws of physics.

Throwing a Curve Ball

Throwing a curve ball is a snap - literally. A pitcher makes a finger-snapping, wrist twisting movement as the ball is released. This creates a top spin, so that the top of the ball is moving forward against the air, while the lower half is spinning backward and moving the same direction as the air. The air pressure above the ball is greater than the pressure below, causing the ball to curve downward. In the 60 feet between pitcher and batter a curving ball can fall a foot or more.

In addition to the curve caused by the effects of air pressure, gravity also effects the path of the ball. The pitcher throws the ball with just enough force to get the ball to the batter. Gravity makes objects move faster over time, so its effect on the ball increases as it reaches home plate. As the ball nears the batter, gravity becomes the dominate (higher) force and pulls the ball down as much as two feet. Remember, the ball began, at head level, with a pitcher standing on a mound one foot higher than the batter. The arc of the curve has become very significant (important).

A curve ball, then, is not an optical illusion (trick to the eye). Anyone who has stood in a batter's box and tried to hit a curve ball knows this is true! But, some batters say that the ball seems to make a sharp bend away from the bat as they swing, as if the wood of the bat repelled the ball. This is somewhat of an illusion. A curve ball makes a smooth, circular path from the pitcher to the batter but, because of the increasing influence of the gravitational pull on the ball and the difference in height between release and arrival, the ball appears from a batter's point of view to "fall off a table."

To add to the batter's dilemma (problem), a good pitcher knows a variety of curving pitches, such as:

Roundhouse - A curve ball thrown by a right handed pitcher to a right handed batter with a topspin and a twist of the wrist, as if turning a door handle. It causes the ball to move both down and to the left (away from the batter). The ball arrives lower and farther away than it would if it had been thrown in a straight line.

Screwball - This is the same as the roundhouse except the pitcher twists his wrist in the opposite direction causing the ball to curve in toward the batter instead of away.

Slider - A curve ball thrown with more force. Thus, gravity does not have as much of a "dominating" effect as in a regular curve ball. The ball drops very little, or not at all and seems to "slide" to the right or left.

Sinker - A ball thrown with top spin with but less force than a slider, and without the twist of the wrist. The ball does not move to the left or right, but it simply sinks (drops) as it arrives.

Knuckleball - The ball is held and thrown with little velocity (speed) or spin. This pitch is left to the random effects of air pressure and currents. Not only does the batter have to guess where it's going, so do the pitcher and the catcher!.

Consider: A ball travels from the pitcher to the catcher in about half a second. In order to hit the ball, the batter must be swinging before the ball arrives. This means the batter has about a quarter of a second to decide where the ball will be and how soon it will be there, and swing (or not swing) accordingly. Batting is considered the most difficult task (job) in baseball. And on the mound is the pitcher, who is often likened (compared) to an artist with a palette (list) of choices. Considering what we now know is involved - velocity, air pressure, gravity - one might call a pitcher not baseball's artist but its scientist.

If you'd like to see some of our students practicing different pitches click here.

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Last modified: Mon Jun 16 22:49:33 PDT 1997

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