www.whyville.net Jun 14, 2009 Weekly Issue

Science Specialist

Secrets of the Curveball

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The curveball has long been one of baseball's most famous (or infamous) pitches. Besides being tricky for a batter to hit, the science of the curveball is pretty neat, governed by two separate, but related scientific principles: Bernoulli principle and the Magnus effect. Here's the short-and-sweet version: when a curveball is thrown, the speed of the wind moving across the ball causes a change in the air's pressure; the faster the wind moves, the lower the pressure. Perhaps the most common example of the Bernoulli Principle is seen on an airplane - the shapes of their wings allow air to move faster on top of the wing (lower pressure) than underneath the wing (higher pressure), helping to create the lift needed for planes to take off.

Bernoulli Effect - Science Theater 17

The Magnus Effect adds on to this principle, and in the case of the curveball, the stitches on the ball are believed to create this difference in pressure from one side of the ball to the other, causing the ball to curve.

But the full challenge of hitting a curveball lies in more than just the physics, it also involves the batter's ability to properly see the ball and judge its trajectory (or path). Some researchers believe that the difficulty lies in whether the batter views the ball straight-on, through his/her peripheral vision (from the sides of the eyes), or switches between the two. This can make a crucial difference, but until recently it was tricky figuring out how to explain this concept. But thankfully, the 2009 Illusion of the Year contest has saved the day. The winning entry, The Break of the Curveball, is a fairly simple demonstration of how very different a curveball can look, and has definitely increased my respect for the players who can successfully hit one! Check out the winner and all the finalist entries here - there are some amazing illusions that test your eyesight and perception - I keep going back to it and trying to outsmart my own brain . . . no such luck :-) Have fun!



Editor's Note: For more blogs from Dr. Rabiah, visit Science Chicago's website at: http://www.sciencechicagoblog.com


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