万物简史 第273期:砰!(8)

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　　Identifying an asteroid¹ doesn't make it safe. 确认一颗小行星不会使它安全一点。

　　Even if every asteroid in the solar system had a name and known orbit, 即使太阳系里的每颗小行星都有了名字，知道了它的轨道，

　　no one could say what perturbations might send any of them hurtling toward us. 谁也说不准什么摄动会使哪颗小行星朝我们飞来。

　　We can't forecast rock disturbances² on our own surface. 我们无法预测岩石会对地球表面产生什么干扰。

　　Put them adrift in space and what they might do is beyond guessing. 岩石在太空里飞行，我们无法猜测它们会干出什么。

　　Any asteroid out there that has our name on it is very likely to have no other. 外层空间里的任何小行星有了名字以后很可能就到此为止。

　　Think of the Earth's orbit as a kind of freeway on which we are the only vehicle, 假设地球的轨道是一条马路，上面只有我们一辆汽车在行驶，

　　but which is crossed regularly by pedestrians³ who don't know enough to look before stepping off the curb⁴. 但这条马路经常有行人穿过，他们踏上马路以前又不知道先看一眼。

　　At least 90 percent of these pedestrians are quite unknown to us. 至少有90%的行人我们不大认识，

　　We don't know where they live, what sort of hours they keep, how often they come our way. 我们不知道他们住在哪里，不知道他们的作息时间，不知道他们穿这条马路的次数。

　　All we know is that at some point, at uncertain intervals⁵, 我们只知道他们在某个地点，每隔不确定的时间，

　　they trundle across the road down which we are cruising at sixty-six thousand miles an hour. 慢步走过这条马路，而我们正沿着这条马路以每小时10万公里的速度行驶。

　　As Steven Ostro of the Jet Propulsion Laboratory has put it, 正如喷气推进实验室的史蒂文·奥斯特罗所说：

　　"Suppose that there was a button you could push and you could light up all the Earth-crossing asteroids⁶ larger than about ten meters, “假如你可以打开一盏灯，照亮所有越过地球的大于10米左右的小行星，

　　there would be over 100 million of these objects in the sky." 你会看到天空中有1亿个这类物体。”

　　In short, you would see not a couple of thousand distant twinkling stars, 总之，你看到的不是远方有2000颗闪闪发光的星星，

　　but millions upon millions upon millions of nearer, randomly⁷ moving objects, 而是附近有几亿甚至几万亿个随意移动的物体，

　　"all of which are capable of colliding with the Earth and all of which are moving on slightly different courses through the sky at different rates. “它们都可能与地球相撞，都在天空中以不同的速度在稍稍不同的路线上移动。

　　It would be deeply unnerving." 这真让人心惊胆战。”

　　Well, be unnerved because it is there. 那么，你就心惊胆战吧，因为它们就在那里。

　　We just can't see it. 我们只是看不见它们。

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