【英语时差8,16】陨星（下）

But there’s another reason. Remember that the earth doesn’t sit still in space: it’s orbiting the sun at 18.5 miles per second. Meteors that are coming towards us go faster across the sky because of earth’s forward velocity¹. It’s like two cars passing in opposite directions. In general, the fastest meteors to enter our atmosphere move at about 26 miles-per-second. Add earth’s forward velocity to that and it goes up to almost forty-five miles a second. Zoom²! These kinds burn up and are gone in less than one second. Meteors that come from the other direction, however, are essentially³ chasing the earth through space. Their speed is decreased by the same amount as our forward velocity. That’s like two cars passing while travelling in the same direction. The speeds cancel out and the passing car seems to be going much slowly.

1 velocity   

n.速度，速率

参考例句：

• Einstein's theory links energy with mass and velocity of light.爱因斯坦的理论把能量同质量和光速联系起来。
• The velocity of light is about 300000 kilometres per second.光速约为每秒300000公里。

2 zoom   

n.急速上升；v.突然扩大，急速上升

参考例句：

• The airplane's zoom carried it above the clouds.飞机的陡直上升使它飞到云层之上。
• I live near an airport and the zoom of passing planes can be heard night and day.我住在一个飞机场附近，昼夜都能听到飞机飞过的嗡嗡声。

3 essentially   

adv.本质上，实质上，基本上

参考例句：

• Really great men are essentially modest.真正的伟人大都很谦虚。
• She is an essentially selfish person.她本质上是个自私自利的人。