美国国家公共电台 NPR The Science Behind The World Cup Ball（在线收听）

The Science Behind The World Cup Ball

DAVID GREENE, HOST:

If you've been watching the World Cup, maybe you've noticed that there is a custom-designed soccer ball being used. NPR's Merrit Kennedy reports that scientists ran tests in a wind tunnel to understand how the new ball plays.

MERRIT KENNEDY, BYLINE: It's called the Telstar 18. It has six panels and a slick black-and-white design inspired by Russian cityscapes. But is it actually a good soccer ball? To find out, scientists stuck it in a wind tunnel with a bunch of sensors.

JOHN ERIC GOFF: It's actually recording the size of the forces on the ball.

KENNEDY: That's John Eric Goff, a physics professor at Lynchburg College. Adidas has redesigned the World Cup ball for each tournament since 1970, and Goff says tiny changes to the design can make a big difference in how the ball responds during play. For example...

GOFF: The dreaded 2010 Jabulani ball that was used in South Africa.

KENNEDY: It was too smooth, he says, which caused it to behave in ways that players sometimes weren't expecting. The smoothness issue was basically fixed for the 2014 World Cup in Brazil. The ball had longer seams joining its panels, which roughened it up a bit. After crunching the numbers, Goff says this year's ball probably won't create big controversies.

GOFF: I don't see that this ball is going to be so drastically different from the 2014 ball.

KENNEDY: But there is one way the players might notice a difference - on high-speed kicks, the kind that a goalkeeper might do to send the ball way down the field. The scientists expect an 8 to 9 percent drop in range with the new ball. So why do they change the ball every time?

GOFF: It's an interesting phenomena that the world's most popular sporting event for the world's most popular sport and the most important piece of equipment in that sport is changed every World Cup.

KENNEDY: Goff says it's not about physics; it's about money and marketing. Adidas sells these balls to the public for a hundred and twenty-four bucks each. Merrit Kennedy, NPR News.