Does The Ball Really Curve?

If you ask a baseball player "does a curveball curve?" they'll tell you that it sure does, and they're right. It turns out it is a lot harder to prove than you may have expected.  In September 1941, Life magazine claimed to have proven, through a series of high speed pictures, that the curve ball didnít curve at all and it was just an "optical illusion." Again, as recently as November 1982, Science 82 magazine published an article that referred to the "apparent break in a curveball" as an "illusion."  If curveballs curve a lot, according to baseball players than where does this controversy stem from?






The bottom dotted line is tangent to the path of the ball when the pitcher releases the ball.  If the hitter thinks the ball is a fastball this is the path they would expect the ball to take, but the ball curves on its way to the plate, represented by the solid black line, and the hitter would claim the the ball curved the width of the plate.

However, if you were to draw a line from where the ball leaves the pitcher's hand to where it crosses the plate. The largest deviation from this line, called the sagitta, is much smaller. If you were to have three poles in a row it would be very difficult to throw a pitch which passes left of the first, right of the second, and left of the third.