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In 1997, in a game between France and Brazil,
1997年，在一场法国与巴西之间的比赛中，
a young Brazilian player named Roberto Carlos set up for a 35 meter free kick.
一名名叫罗伯托·卡洛斯的年轻巴西球员从35米外发出了任意球。
With no direct line to the goal, Carlos decided to attempt the seemingly impossible.
没有任何通向球门的直线，卡洛斯的尝试看起来是不可能的。
His kick sent the ball flying wide of the players,
他的射门让球飞过球员，
but just before going out of bounds, it hooked to the left and soared into the goal.
但是就当球要出界时，却向左边变向，然后进门。
According to Newton's first law of motion,
根据牛顿第一定律，
an object will move in the same direction and velocity until a force is applied on it.
一个物体会以同样的方向和速度移动，除非被施加一个外力。
When Carlos kicked the ball, he gave it direction and velocity,
当卡洛斯踢球时，他已经给了球一个速度和运动方向，
but what force made the ball swerve and score one of the most magnificent goals in the history of the sport?
但是是什么力让球改变方向，然后成为运动史以来最伟大的进球之一呢？
The trick was in the spin.
诀窍是旋转。
Carlos placed his kick at the lower right corner of the ball, sending it high and to the right, but also rotating around its axis.
卡洛斯从右下方踢球，让球边绕轴心旋转，边向右侧高飞。
The ball started its flight in an apparently direct route, with air flowing on both sides and slowing it down.
球从一个明显的直线起飞，空气飞过两边使其变慢。
On one side, the air moved in the opposite direction to the ball's spin, causing increased pressure,
在一边，空气以球转的反方向旋转，导致压力上升，
while on the other side, the air moved in the same direction as the spin, creating an area of lower pressure.
然而在另一边，空气以与球相同的方向旋转，产生一部分低压区。
That difference made the ball curve towards the lower pressure zone.
这个差异，使球向低压区变向。
This phenomenon is called the Magnus effect.
这个现象叫做马格努斯效应。
This type of kick, often referred to as a banana kick, is attempted regularly,
这种踢法，也被叫做香蕉球，被经常使用，
and it is one of the elements that makes the beautiful game beautiful.
而且它会让一场精彩的比赛更加精彩。
But curving the ball with the precision needed to both bend around the wall and back into the goal is difficult.
但是香蕉球所需的使其躲开人墙然后进门的精准度，是非常难做到的。
Too high and it soars over the goal. Too low and it hits the ground before curving.
太高的话球会飞过球门。太低的话会在旋转前击地。
Too wide and it never reaches the goal. Not wide enough and the defenders intercept it.
角度太大的话会永远进不了球门。角度不够大的话，防守者就可以拦截。
Too slow and it hooks too early, or not at all. Too fast and it hooks too late.
太慢的话球会早转弯，甚至不转。太快的话球会转的太晚。
The same physics make it possible to score another apparently impossible goal, an unassisted corner kick.
同样的物理理论，使看起来不可能、没有收到任何帮助的角球进球成为可能。
The Magnus effect was first documented by Sir Isaac Newton after he noticed it while playing a game of tennis back in 1670.
马格努斯效应最初是由伊萨克·牛顿记录袭来的。在1670年打完一场网球后，他发现了这一现象。
It also applies to golf balls, frisbees and baseballs.
这个原理同样适应于高尔夫球、飞碟和棒球。
In every case, the same thing happens.
在每个案例中，都会发生相同的事情。
The ball's spin creates a pressure differential in the surrounding air flow that curves it in the direction of the spin.
球的旋转在周围的气流中产生压差，从而导致球向其旋转。
And here's a question. Could you theoretically kick a ball hard enough to make it boomerang all the way around back to you?
又有一个问题了。从理论上来讲，你可以使劲踢球，让球转回到你这里吗？
Sadly, no. Even if the ball didn't disintegrate on impact, or hit any obstacles,
很遗憾，不行。即使球没有在冲撞中分解，或者击中任何障碍物，
as the air slowed it, the angle of its deflection would increase,
随着空气使其速度变慢，偏转角会增加，
causing it to spiral into smaller and smaller circles until finally stopping.
使螺旋变成越来越小的圆，最终停下来。
And just to get that spiral, you'd have to make the ball spin over 15 times faster than Carlos's immortal kick.
只是要达到这种旋转，你就需要使球转的比卡洛斯那记不朽的进球快15倍。
So good luck with that.
所以，祝你好运吧。
