万物简史 第287期:砰!(22)

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　　which makes it difficult to study, Anderson went on, "while Manson is really quite accessible. 这就使得研究工作很困难，”安德森接着说，“而曼森大坑是完全进得去的。

　　It's because it is buried that it is actually comparatively pristine³." 它被埋在地下，处于比较原始的状态。”

　　I asked them how much warning we would receive if a similar hunk of rock was coming toward us today. 我问他们，要是今天有一块类似的岩石朝我们飞来，我们有多长的警报时间。

　　Oh, probably none, said Anderson breezily. “哦，很可能没有，”安德森轻松地说，

　　"It wouldn't be visible to the naked eye until it warmed up, and that wouldn't happen until it hit the atmosphere,  “要等它发热肉眼才看得见，而它在接触大气以前是不会发热的。

　　which would be about one second before it hit the Earth. 到了那个时刻，大约再过一秒钟它就要撞击地球。

　　You're talking about something moving many tens of times faster than the fastest bullet. 它的速度比最快的子弹还要快好几十倍。

　　Unless it had been seen by someone with a telescope, and that's by no means a certainty, it would take us completely by surprise." 除非有人用天文望远镜发现它，而那根本是没有把握的事，它会完全对我们来个突然袭击。”

　　How hard an impactor hits depends on a lot of variables, 一个物体撞击地球的力量，取决于许多变数，

　　angle of entry, velocity⁴ and trajectory⁵, whether the collision is head-on or from the side, 其中包括冲击物进入大气的角度，它的速度与轨道，是迎面相撞还是从斜里相撞，

　　and the mass and density⁶ of the impacting object, among much else—none of which we can know so many millions of years after the fact. 以及它的质量与密度──这一些，事后几百万年我们都无法知道。

　　But what scientists can do—and Anderson and Witzke have done—is measure the impact site and calculate the amount of energy released. 但是，科学家们能做的是──安德森和威策克已经做的是──测量撞击现场和计算释放出的能量。

　　From that they can work out plausible⁷ scenarios⁸ of what it must have been like—or, more chillingly, would be like if it happened now. 根据那些结果，他们可以推断出当时肯定是什么情景──或者更令人寒心地说，如果现在发生的话，将会是什么情景。

　　An asteroid⁹ or comet traveling at cosmic velocities¹⁰ would enter the Earth's atmosphere at such a speed  当一颗以宇宙速度飞行的小行星或彗星进入大气层的时候，它的速度如此之快，

　　that the air beneath it couldn't get out of the way and would be compressed, as in a bicycle pump. 下面的空气来不及让路，会像自行车打气筒里的空气那样被压缩。

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