南非世界杯指定用球背后的科学真相

当普通球迷们翘首以盼的四年一届世界杯即将来临时，科学界也在为此而欢欣鼓舞，不过吸引他们的不是世界杯，而是世界杯指定用球 ——普天同庆。阿迪达斯为2010年南非世界杯研发的这款比赛用球号称是全面超越了2006年的“团队之星”，是有史以来最精准的足球，它到底是如何打造而成的呢？

While the sporting world watched the clock for the high noon announcement of the brackets for the 2010 World Cup in South Africa, we were salivating over another four-year tradition: the engineering and innovation that goes into the official World Cup ball. With the 2010 Cup's Jabulani ball (‘to celebrate’ in isiZulu), Adidas claims it has surpassed its own Teamgeist from 2006 in constructing the roundest and most accurate ball ever played. See how it's made inside.

阿迪达斯公司为世界杯所制造的比赛用球，从墨西哥世界杯的“泰世达（Telstar）”到如今南非世界杯的“普天同庆”，一代超越一代。足球运动员眼中的理想足球应该不但要有一流的足部触感，而且还要随心所欲的控制球的飞行路径。德国世界杯时的比赛用球“团队之星”只用了12块直接成型的球皮就完成了球面，而且在拼接过程中，用热粘合技术淘汰了不精确的缝合法。

And you thought a ball was just a ball? From the iconic 32 panel black and white Telstar introduced in Mexico City in 1970 to the latest unveiled today for South Africa, the goal for Adidas, naturally, has always been to build a better ball. Soccer players want a ball that feels good on the foot and flies predictably no matter where on the ball it’s struck. Teamgeist achieved its improvements by reducing the number of panels from 32 to just 12, by thermally bonding the panels thereby eliminating inaccurate stitching and by forming the outer panels in 3-D versus making them flat and bending them into shape.

南非世界杯的比赛用球“普天同庆”比“团队之星”所用的球皮数更少，它只用8块EVA和TPU皮块就完成了拼接，由于接缝减少，使得击打面增加了70％。由于“团队之星”独特的空气动力学设计，导致飞行的球在空中缺乏旋转，这种设计遭到了很多门将的诟病，他们认为这样的球飞行路径过于飘忽，难以判断。因此阿迪达斯公司在设计“普天同庆”时，在球体上加上特有的“空气动力凹槽”，球皮上长长的刻痕有助于提高足球的飞行稳定性，以获得最佳的飞行状态；另外，“普天同庆”表面覆盖的凸起小点有助于球员触球时的足部舒适感。

Jabulani takes another step towards perfection with just eight EVA and TPU panels that provide a 70% larger striking surface due to fewer seams. While the Teamgeist ball was great for strikers, many goal keepers complained that the ball's aerodynamics created a lack of rotation in the air, making its path at times erratic, like a knuckleball. Jabulani attempts to stabilize the flight pattern of the ball through what Adidas is calling ‘aero grooves’, essentially long indentations along the panels. The grooves divide the ball up into additional pseudo-panels but by molding the grooves Adidas can achieve consistent location and shape to achieve optimal flight. The surface of the ball has also been covered with raised nubbins to help with tactile feel on the foot.

阿迪达斯的机械踢球和风洞实验是在英国拉夫堡大学和公司的德国足球实验室完成的，为了达到国际足联苛刻的用球标准，他们还进行了更多的静态测试，实验结果表明，“普天同庆”是有史以来最精确的足球。

While Adidas would not provide numerical flight data, it claims that robotic kicking and wind tunnel testing at Loughborough University in England and at its own football lab in Germany show that Jabulani is its most accurate ball. To be sanctioned FIFA Approved, a ball is only subject to a handful of more static tests, which the Jabulani ball obviously meets.

以下是“普天同庆”的相关数据：

周长：国际足联标准：68.5-69.5厘米/普天同庆：69.0 +/- 0.2厘米

• Circumference: FIFA Standard: 68.5-69.5cm, Jabulani: 69.0 +/- 0.2

圆度：在16个不同地点进行检测，国际足联标准：最大误差1.5%/普天同庆：最大误差1.0%

• Roundness: Diameter is measured in 16 different locations. FIFA Standard: max 1.5% difference, Jabulani: max 1.0% difference

重量：国际足联标准：420-445 克/普天同庆：440 +/- 0.2克

• Weight: FIFA standard: 420-445 grams, Jabulani: 440 +/- 0.2 grams

吸水性：在水中进行250 次加压旋转测试，国际足联标准：最大增重10%/普天同庆：无增重，不吸水

• Water Absorption: A ball is pressed and rotated in water 250 times: FIFA Standard: max 10% weight increase. Jabulani: 0% weight increase

反弹性：国际足联要求的唯一一项动力学测试，足球要从两米高的高度反复10次坠向钢板，国际足联标准：最高和最低反弹之差要在10厘米以下/普天同庆：反弹高度在143至149厘米之间

• Uniform Rebound: The only dynamic FIFA test, the ball is dropped ten times onto a steel plate from a two meter height. The difference from the lowest to the highest bounce can be no more than 10 cm. Jabulani bounced in a range from 143 to 149 cm.

压力损失：充气完三天后检查气压情况，国际足联标准：最多损失20/普天同庆：最多损失10％

• Loss of Pressure: Air pressure measured three days after inflation. FIFA Standard: 20% max loss, Jabulani: 10% max loss