The psychophysics of baseball

This is a pretty interesting article on msnbc.com about baseball, visual illusions, psychophysics, etc.

When a hitter swings under the ball and misses, baseball announcers sometimes say the pitcher got him with a "rising fastball." But technically, this pitch cannot exist if thrown overhand — it's impossible for a pitch thrown downward to buck gravity and achieve upward lift.

The rising fastball deceives the hitter in almost the opposite way a good curve does. A 90-mph fastball will drop significantly less than one thrown at 80 mph. So instead of dropping a few inches in the last few feet, a fastball with some serious zip will maintain a nearly straight trajectory.

"If he thinks it's an 80-mph fastball, but it's really 90 mph, since it didn't drop it will appear to rise in that last instant," Fuld said. "It looks like it hops up, and that's the illusion of a rising fastball."

The picture is pretty informative (click on it for a bigger version) - its from Robert Adair of Yale. I got this from a physics of baseball site hosted here at UIUC, well worth checking out.