On a previous show we mentioned how not all shooting stars have the same speed.
前面的文章中我们提到为什么不是所有流星都有相同的速度。
Some disappear almost immediately, while others make a nice slow line across the sky.
有些几乎立即就消失了，而有些拖着长长的尾巴穿过天空。
If you enjoy watching the slow ones, there is a way of upping your chances of seeing them.
如果你喜欢观看缓慢的流星，那么有一种方法可以增加你看到它们的几率。
Go out just after sunset.
日落后就出门。
That's because the slowest meteors come in the evening and the fastest ones come in the morning, just before sunrise.
最慢的流星在夜晚出现，最快的流星出现在早晨，就在太阳升起之前。
Can you guess why?
你猜猜为什么呢？
The speeds of meteors we see are increased or decreased by the earth's motion.
我们看到的流星的运动速度随着地球的运动情况而增减。
If we charge into them head-on our speed is added to their speed.
如果地球正对着流星的方向运动，那么我们的运速就会增加至它的运动速度中。
If, on the other hand, we aremoving away from them, our speed is subtracted from their speed.
反之，如果我们背向它们运动，那么它们的运速中就会减去地球运速这一部分。
Now imagine yourself standing at the north pole, facing the direction the earth is moving through space.
现在想想你自己站在北极，面向地球穿过空间移动的方向。
You rise up magically, far enough away that you can see the whole planet rotating underneath you while you yourself remain stationary.
你奇迹般地上升，远到可以看到整个地球在你的脚下转动，而你自己保持静止。
Which direction is it turning?
它是在向哪个方向运动呢？
Counterclockwise. Where is thesunlight?
逆时针。太阳光在哪里呢？
From your perspective, it's on the left side of the planet.
从你的角度来看，在地球的左侧。
That means that the front of the planet, or the part that's charging into oncoming meteors, is the placewhere morning is beginning for people on earth.
这意味着在地球的前端，或者是在正对流星运动的地方，就是早晨的开始。
The back of the planet, meaning the part that's movingaway from meteors, is where evening is beginning.
地球的背面，也就是背向流星运动的地方，就是夜晚的开始。
It may seem funny, but every morning when you look up into the sky, you are looking in the same direction as the planet is moving.
这似乎非常有趣，但是每天早晨当你仰望天空时，你就是望着与地球转动相同的方向。
In the evening you are looking the other way.
晚上，你就是望着相反的方向。
And the speed ofshooting stars confirms it!
流星的速度证实了这一点。
