万物简史 第287期:砰!(22)

 　　Chicxulub is buried under two to three kilometers of limestone¹ and mostly offshore²,  “奇克休留布大坑在两三公里的灰岩深处，而且大部分在近海。

　　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。

1 limestone   

n.石灰石

参考例句：

• Limestone is often used in building construction.石灰岩常用于建筑。
• Cement is made from limestone.水泥是由石灰石制成的。

2 offshore   

adj.海面的，吹向海面的；adv.向海面

参考例句：

• A big program of oil exploration has begun offshore.一个大规模的石油勘探计划正在近海展开。
• A gentle current carried them slowly offshore.和缓的潮流慢慢地把他们带离了海岸。

3 pristine   

adj.原来的，古时的，原始的，纯净的，无垢的

参考例句：

• He wiped his fingers on his pristine handkerchief.他用他那块洁净的手帕擦手指。
• He wasn't about to blemish that pristine record.他本不想去玷污那清白的过去。

4 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。

5 trajectory   

n.弹道，轨道

参考例句：

• It is not difficult to sketch the subsequent trajectory.很容易描绘出它们最终的轨迹。
• The path followed by a projectile is called its trajectory.抛物体所循的路径称为它的轨道。

6 density   

n.密集，密度，浓度

参考例句：

• The population density of that country is 685 per square mile.那个国家的人口密度为每平方英里685人。
• The region has a very high population density.该地区的人口密度很高。

7 plausible   

adj.似真实的，似乎有理的，似乎可信的

参考例句：

• His story sounded plausible.他说的那番话似乎是真实的。
• Her story sounded perfectly plausible.她的说辞听起来言之有理。

8 scenarios   

n.[意]情节；剧本；事态；脚本

参考例句：

• Further, graphite cores may be safer than non-graphite cores under some accident scenarios. 再者，根据一些事故解说，石墨堆芯可比非石墨堆芯更安全一些。 来自英汉非文学 - 环境法 - 环境法
• Again, scenarios should make it clear which modes are acceptable to users in various contexts. 同样，我们可以运用场景剧本来搞清楚在不同情境下哪些模式可被用户接受。 来自About Face 3交互设计精髓

9 asteroid   

n.小行星；海盘车(动物)

参考例句：

• Astronomers have yet to witness an asteroid impact with another planet.天文学家还没有目击过小行星撞击其它行星。
• It's very unlikely that an asteroid will crash into Earth but the danger exists.小行星撞地球的可能性很小，但这样的危险还是存在的。

10 velocities   

n.速度( velocity的名词复数 )；高速，快速

参考例句：

• In experimenting we find out that sound travels with different velocities through different substances. 在实验中，我们发现声音以不同的速度通过不同的物质而传播。 来自《现代汉英综合大词典》
• A gas in thermal equilibrium has particles of all velocities. 处于热平衡的气体，其粒子有一切速度。 来自辞典例句