万物简史 第274期:砰!(9)

  　　Altogether it is thought—though it is really only a guess, based on extrapolating from cratering¹ rates on the Moon, 据认为──虽然只是根据月球上形成凹坑的速度所作的一种推测，

　　that some two thousand asteroids³ big enough to imperil civilized⁴ existence regularly cross our orbit. 共有2000颗左右大得足以危及文明社会的小行星经常穿越我们的轨道。

　　But even a small asteroid²—the size of a house, say—could destroy a city. 但是，即使是一颗很小的小行星──比如房子那么大小的小行星──也能摧毁一座城市。

　　The number of these relative tiddlers in Earth-crossing orbits 穿越地球轨道的比较小的小行星，

　　is almost certainly in the hundreds of thousands and possibly in the millions, and they are nearly impossible to track. 几乎肯定数以十万计，很可能数以百万计，而它们几乎是无法跟踪的。

　　The first one wasn't spotted⁵ until 1991, and that was after it had already gone by. 第一颗有可能造成危险的小行星是1991年才被发现的。那是在它已经飞过去以后。

　　Named 1991 BA, it was noticed as it sailed past us at a distance of 106,000 miles, 它被命名为1991BA号；我们注意到，它在17万公里以外的地方跟地球擦肩而过，

　　in cosmic terms the equivalent of a bullet passing through one's sleeve without touching⁶ the arm. 按照宇宙的标准，这相当于一颗子弹穿过我们的袖子而又没有擦破胳膊。

　　Two years later, another, somewhat larger asteroid missed us by just 90,000 miles—the closest pass yet recorded. 两年以后，又有一颗较大的小行星险些碰着地球，只相差145000公里──这是记录到的最接近的一次擦肩而过。

　　It, too, was not seen until it had passed and would have arrived without warning. 这一次也是在它飞过去以后才发现的，它在毫无预兆的情况下光临地球。

　　According to Timothy Ferris, writing in the New Yorker, such near misses probably happen two or three times a week and go unnoticed. 蒂姆西·费里斯在《纽约客》杂志中写道，这样的擦肩而过每星期很可能要发生两三次而又不为人们注意。

　　An object a hundred yards across couldn't be picked up by any Earth-based telescope until it was within just a few days of us, 一个直径为200米的物体，要等到它距离我们还有几天的时候，地球上的天文望远镜才能发现，

　　and that is only if a telescope happened to be trained on it, 而且恰好是那台望远镜对准它，

　　which is unlikely because even now the number of people searching for such objects is modest. 这是不大可能的，因为即使现在，在搜寻这类物体的人也为数不多。

　　The arresting analogy that is always made is that the number of people in the world who are actively⁷ searching for asteroids 人们总是作这样的类比：世界上在积极寻找小行星的人数，

　　is fewer than the staff of a typical McDonald's restaurant. 还不及一家典型的麦当劳快餐店的职工人数。

　　(It is actually somewhat higher now. But not much.) （实际上，现在比这多了一些，但多不了多少。）

1 cratering   

n.缩孔（露底），陷穴（漆病），磨顶槽v.火山口( crater的现在分词 )；弹坑等

参考例句：

• In addition, cratering and ground shock phenomena are observed, as will be described in Chapter VI. 此外，还可以观察到巨坑或地面冲击波的现象，这些现象将在第六章中加以叙述。 来自辞典例句
• Check the page without pinhole, bubble cratering and fix it. 查抄版背有无针孔、气泡等弊病，并举动补缀。 来自互联网

2 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。

3 asteroids   

n.小行星( asteroid的名词复数 )；海盘车，海星

参考例句：

• Asteroids,also known as "minor planets",are numerous in the outer space. 小行星，亦称为“小型行星”，在外太空中不计其数。
• Most stars probably have their quota of planets, meteorids, comets, and asteroids. 多数恒星也许还拥有若干行星、流星、彗星和小行星。

4 civilized   

a.有教养的，文雅的

参考例句：

• Racism is abhorrent to a civilized society. 文明社会憎恶种族主义。
• rising crime in our so-called civilized societies 在我们所谓文明社会中日益增多的犯罪行为

5 spotted   

adj.有斑点的，斑纹的，弄污了的

参考例句：

• The milkman selected the spotted cows,from among a herd of two hundred.牛奶商从一群200头牛中选出有斑点的牛。
• Sam's shop stocks short spotted socks.山姆的商店屯积了有斑点的短袜。

6 touching   

adj.动人的，使人感伤的

参考例句：

• It was a touching sight.这是一幅动人的景象。
• His letter was touching.他的信很感人。

7 actively   

adv.积极地，勤奋地

参考例句：

• During this period all the students were actively participating.在这节课中所有的学生都积极参加。
• We are actively intervening to settle a quarrel.我们正在积极调解争执。