PITTSBURGH – In 1738 Daniel Bernoulli – a Swiss physicist and mathematician – discovered that for an inviscid flow of a non-conducting fluid, an increase in the speed of the fluid occurs simultaneously with a decrease in pressure or a decrease in the fluid’s potential energy.*
This is known as the Bernoulli Principle.
As it applies to baseball, the Bernoulli Principle is what allows pitches to curve.**
When throwing a curveball, the pitcher imparts spin on the ball as it is leaving his hand. As the ball travels￼ through the air, the spin causes the ball to disturb the air around it.
Friction provided by the stitches of the baseball causes a thin layer of air to move around the spinning ball in such a way that air pressure on top of the ball is greater than on the bottom. this causes the ball to curve downward. Consequently, a spinning baseball has more air turbulence on top of the ball, which produces a slower air speed over the ball.
At the same time, air moving under the ball accelerates and moves faster, producing less pressure on the bottom of the ball. The ball moves downward faster than would normally be expected because of this.
Here’s a specific example of the Bernoulli Principle from The New York Times Book￼ of Science Literacy.
“The ordinary curveball, breaking to the left or the right, relies on a lateral force caused by its rapid spin. The sideways spin lowers the pressure on one side and raises it on the other. The effect of spin is potent. A ball spinning at 1,800 revolutions per minute a ball that will turn about 15 times in its 60-foot, 6-inch journey to the plate will feel a sideways force of more than an ounce, which will turn its path by about one and a half feet.”
Moreover, here is a video explantation from the Ohio State School of Engineering (click on the bottom left for sound):
If baseball were to be played in a vacuum, the pitcher would have a very difficult time fooling the batter since there would be zero air pressure to allow for these scientific principles to happen.
However, the game is not played in a vacuum and while the pitcher must possess the necessary skills in order to make a pitch curve, the Bernoulli Principle is there to help the pitcher as the ’10th man’ on the field.
* Source: https://en.wikipedia.org/wiki/Bernoulli%27s_principle
** It goes without saying the pitcher has a lot to do with pitches curving as well.