【英语时差8,16】为什么最慢的流星出现在夜晚？（上）

On a previous show we mentioned how not all shooting stars have the same speed. Some disappear almost immediately, while others make a nice slow line across the sky. If you enjoy watching the slow ones, there is a way of upping your chances of seeing them. Go out just after sunset. That’s because the slowest meteors come in the evening and the fastest ones come in the morning, just before sunrise. Can you guess why? The speeds of meteors we see are increased or decreased by the earth’s motion¹. If we charge into them head-on our speed is added to their speed. If, on the other hand, we are moving away from them, our speed is subtracted² from their speed.

1 motion   

n.打手势，示意，移动，动作，提议，大便；v.运动，向...打手势，示意

参考例句：

• She could feel the rolling motion of the ship under her feet.她能感觉到脚下船在晃动。
• Don't open the door while the train is in motion.列车运行时，请勿打开车门。

2 subtracted   

adj.减掉的，除去的v.减，扣除，做减法( subtract的过去式和过去分词 )

参考例句：

• 6 subtracted from 9 is 3. 9减6等于3。
• We have subtracted $25 per adult to arrive at a basic room rate. 我们已给每位成人房客减去了25美元，这就是基本的房费价格了。 来自辞典例句