Wobbly Ball

From a couple of weeks ago, but still interesting. Heading backwards, it seems:

Adidas produces a new ball for each World Cup and players invariably gripe. Four years ago, the German sporting goods giant switched from the traditional 32 stitched panels to 14. The current Jabulani model — its name means "to celebrate" in Zulu — is down to eight.

This configuration piqued the curiosity of Caltech professors and graduate students, a multinational group that includes a few soccer fans. They took the Jabulani and a traditional ball to their lab even as the U.S. scrambled to victory over Algeria.

The Lucas Wind Tunnel can generate monstrous gusts, but in this case they set the dial to about 30 meters per second, simulating the average speed of a ball kicked by an elite player.

...Consider the history of the golf ball, which was smooth back in the mid-1800s.

"The Scots learned the hard way," McKeon said.

The addition of dimples made for a rougher surface but a narrower wake and less drag, which contributed to straighter, longer trajectories.

To some degree, the Jabulani represents a shift in the opposite direction, even with tiny ridges covering its skin. Caltech's study suggests that it starts with a smooth — or laminar — airflow, shifts to something more turbulent, then shifts back again.

These variations can have a big effect.

"So as the goalkeeper sees the ball coming, it suddenly seems to change its trajectory," McKeon said. "It's like putting the brakes on, but putting them on unevenly."