美国国家公共电台 NPR The Science Behind The World Cup Ball

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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, BYLINE¹: 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 sensors².

JOHN ERIC GOFF: It's actually recording³ 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 dreaded⁴ 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 fixed⁵ for the 2014 World Cup in Brazil. The ball had longer seams joining its panels, which roughened it up a bit. After crunching⁶ the numbers, Goff says this year's ball probably won't create big controversies⁷.

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 phenomena⁸ 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 marketing⁹. Adidas sells these balls to the public for a hundred and twenty-four bucks¹⁰ each. Merrit Kennedy, NPR News.