However, when we look at the 100 billion stars in our galaxy (the Milky Way), and 100 billion galaxies in the observable Universe, it seems inconceivable that at least one of these planets does not have a life form on it; in fact, the best educated guess we can make, using the little that we do know about the conditions for carbon-based life, leads us to estimate that perhaps one in 100,000 stars might have a life-bearing planet orbiting it.

　　【句子主干】

　　when we…, it seems inconceivable that at least …; in fact, the best educated guess…leads us to estimate that…

　　【结构分析】

　　分号之前，when we…引导时间状语从句

　　it 是形式主语，实际主语是that引导的从句

　　分号之后，guess(we can make), we can make 是定语从句，修饰guess

　　using…现在分词修饰guess, the little (that…) that引导定语从句，修饰little

　　estimate (that…)that引导宾语从句

　　【重点词汇】

　　inconceivable adj. 难以置信的;不可思议的

　　in fact 确切地说;事实上;实际上

　　bear 具有;生;忍受;经得起

　　【句子翻译】

　　然而，当我们遥望银河系中1,000亿颗恒星和可见宇宙中的1,000亿个星系时，很难相信这些行星上没有一个生命存在。确切地说，凭我们对碳基生命仅有的了解，我们所能做出的最有根据的猜测是，也许每十万个恒星中的一颗会存在孕育生命的行星在围绕它旋转。

　　翻译练习

　　中翻英：

　　1. 几年前人们很难相信大街上跑着充电汽车。

　　2. 核泄漏造成的长期后果真是不堪设想。

　　英翻中：

　　This might be explained by the fact that the novel has evolved precisely because of technological developments that made it possible to print out huge numbers of texts, whereas oil paintings have always been produced as unique objects.

　　翻译答案

　　1. A few years ago a car fuelled by electricity running on the avenue would have been inconceivable.

　　2. The long-term consequences of a nuclear leak do not bear thinking about.