# Where does a Curveball get its Curve?

A curveball, as defined by Merriam-Webster Dictionary is, “a slow or moderately fast baseball pitch thrown with spin to make it swerve downward and usually to the left when thrown from the right hand or to the right when thrown from the left hand”. If you are familiar with the sport of baseball, then you probably have seen or heard of the term curveball. As a kid who loved everything about baseball I was always amazed how professional pitchers could put so much movement on the ball. It was my dream to replicate the same throwing motion that caused the world’s greatest hitters to swing and whiff.

### The Discovery

The first person to be credited with throwing a curveball is Candy Cummings in 1867. Some people believed the curveball was an optical illusion. It was not until 1959, when Lyman Briggs, a physicist and former director of the National Institute for Standards and Technology, proved that the ball really did curve using physics.

### The Science

So where does the curve come from? The rotation of the baseball’s seams generates air around the ball in a “whirlpool shape” which causes pressure to be lower on one side of the baseball. This difference in pressure makes the ball push sideways and generate a curve shape that will tail-off from the hitter causing them to swing and miss.

Lyman Briggs measured that a curveball’s maximum rotation is 17.5 inches from 60 feet 6 inches if the ball is pitched at the optimal speed at 68 mph. Major League Pitchers throw the curveball at an average of 76.4 MPH focusing on a mixture of velocity, control, and break. The evolution of the curveball over the years has turned the pitch from being a gimmick, to one that is in almost 2/3 of every MLB pitcher’s arsenal. There have also been new variations of the curveball, such as the 12-6 curveball that focuses primarily on dropping straight down like the 12 and 6 hands on a clock.

### The Illusion

Physics say that it is impossible for a curveball to have a sudden dip, and that the ball must be gradually declining on its entire flight from the mound to the plate. However, from a hitter’s perspective it would appear as though it really does drop. A hitter’s brain is the mostly the cause for misjudging a breaking ball pitch. Arthur Shapiro, a neuroscientist, did a study that tested major league hitter’s visual perspectives when faced against a curveball. The results were that a batter’s brain has the first 0.2 seconds of a pitch to identify where the ball will be when it reaches the plate. Different parts of the visual system are being used while the ball goes through the field of vision. Meanwhile, the ball is rotating while its position is changing creating what is basically an optical illusion to the hitter.

Sources:

Kaplan, Sarah. “The Surprising Science of Why a Curveball Curves.” The Washington Post. WP Company, 12 July 2016. Web. 02 Dec. 2016.

Pictures/GIFs:

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## 2 thoughts on “Where does a Curveball get its Curve?”

1. Johann Michael Kok

I enjoyed this article a lot. I too enjoyed baseball throughout my whole childhood I found it interesting that the baseball doesn’t just drop instantly but instead gradually curves over the whole path of the time. I have been on the receiving end of a curve ball and it truly does look like the ball drops instantly. Now I’m wondering about the physics of a knuckle ball.

2. Zachariah Watkins

Great article, sheds a new light on a great subject. It is interesting that although the curve ball was invented or first thrown in 1867 people did not believe the ball was actually curving until it was proven to indeed curving by Lyman Briggs in 1959. With it seeming like it is physically impossible to hit a curve ball at 76 mph I wondered what it was like for batters to hit a Major League fastball which on average travels about 20 mph faster than a curve ball. After reading the article it surprised me that batters have such minutes amount of time to hit the baseball and most of the hitting is based off of seeing the same pitch numerous amounts of time basically attributing the hit to muscle memory and luck.