Still, statistically¹ the probability that there are other thinking beings out there is good. 不过，从统计角度来看，外层空间存在有思想的生物的可能性还是很大。

Nobody knows how many stars there are in the Milky² Way 谁也不清楚银河系里有多少颗恒星

estimates range from 100 billion or so to perhaps 400 billion 估计有1000亿颗到4000亿颗

and the Milky Way is just one of 140 billion or so other galaxies³, 而银河系只是大约1400亿个星系之一，

many of them even larger than ours. 其他许多比我们的银河系还要大。

In the 1960s, a professor at Cornell named Frank Drake, excited by such whopping numbers, 20世纪60年代，康奈尔大学的一位名叫弗兰克·德雷克的教授为这么巨大的数字所振奋，

worked out a famous equation designed to calculate the chances of advanced life in the cosmos⁴ based on a series of diminishing probabilities. 根据一系列不断缩小的可能性，想出了一个著名的方程式，旨在计算宇宙中存在高级生命的可能性。

Under Drake's equation you divide the number of stars in a selected portion of the universe by the number of stars that are likely to have planetary systems; 按照德雷克的方程式，你把宇宙某个部分的恒星数除以恒星可能拥有行星系的数；

divide that by the number of planetary systems that could theoretically support life; 再用那个商除以理论上能够存在生命的行星系数；

divide that by the number on which life, having arisen, advances to a state of intelligence; and so on. 再用那个商除以已经出现生命，而且生命提高到了有智力的状态的行星系数；如此等等。

At each such division, the number shrinks colossally⁵ 每这样除一次，那个数字就大大缩小

yet even with the most conservative inputs⁶ the number of advanced civilizations just in the Milky Way always works out to be somewhere in the millions. 然而，即使以最保守的输入，仅在银河系里，得出的高等文明社会的数字也总是在几百万个。