时差N小时:为何高尔夫球上有小窝?

You're out on the golf course one pleasant afternoon.

在一个舒适的下午，你站在高尔夫球场上。

Your ball is set on the tee.

把球在球托上放好，

You lean overthe ball.

身体倾斜到球的上方，

You grip the club just right.

握好球杆。

Your arms are straight. Your stance perfect.Whoosh!

呼地一声!你挥杆了，高尔夫球飞了起来，

You swing, and the ball takes off toward the green, sailing in a beautiful arc–almost as if it'sweightless.

奔向绿地，划出一道优美的弧线，轻盈得似乎没有重量。

Your impeccable technique certainly has a lot to do with the success of that drive, but yougot amajor assist from the little dimples on the golf ball-and they're the subject of this MomentofScience.

这一杆的成功当然和你完美的技术密不可分，但高尔夫球上的那些小窝也帮了你的大忙，它们就是本期《科学一刻》的主题。

Combined with the proper spin, the dimples help keep the ball in the air longer, and here'show.

如果加上适当的旋转，这些小窝可以帮助高尔夫球在空中停留更长时间，原因如下。

Your picture-perfect swing puts back spin on the ball.

你完美的挥杆动作使球向后旋转。

The dimples trap a layer of air next to theball, and this layer spins with the ball.

球上的小窝吸附了周围薄薄的一层空气，这层空气会与球一块旋转。

The air being dragged across the top of the spinning ball moves in the same direction as theairthat's rushing past.

球所吸附的这层空气转到球的上方时，它的运动方向与周围空气流动方向一致。

As the air spinning with the ball comes around the bottom it is moving in theopposite directionfrom the air on top, and therefore against the onrushing air.

而这层空气到球下方的时候，它的运动方向与上方空气相反，因此与周围气流相抵。

Consequently it'sslower than the air on top.

这样就使得下方的空气的速度比上方的要慢。

A slow moving air stream has higher pressure than a fast moving air stream.

速度慢的气流压强较大，速度快的气流压强较小。

So, the higherpressure on the bottom of the ball is going to hold the ball up longer.

因此，球底部较高的气压可以把球向上托使它在空中驻留更长时间。

The effect of the dimples is so significant that a drive of two-hundred yards hit with a dimpledgolf ball, would be shortened with a non-dimpled ball to about one hundred yards.

这些小窝的作用是十分重要的，同样的一杆，如果可以把有小窝的高尔夫球击出200码，那它只能把没有小窝的球击出大约100码。