Are we alone in the universe? Or is the cosmos teeming with life? And what difference would it make if we found the answer?

我觉得我们不可能在宇宙中是孤独的。在第一批系外行星发现之前，天文学家还不知道如何寻找它们，行星的形成是罕见的还是普遍的，这是一个悬而未决的问题。当我们还不知道答案的时候，我们更容易相信我们的星系可能是，如果不是唯一的，至少是星系中为数不多的行星系统之一。

但我们现在有理由相信星系中充满了行星。By conservative estimates there may beone hundred billionplanets and perhaps two or three times that number in the Milky Way alone. If the Milky Way is typical, that means the universe contains a truly vast amount of planetary real estate. You would think that the odds of there being life out there somewhere or other would be very high indeed.

不幸的是，考虑到宇宙如此之大，考虑到物理定律，我们似乎可以很确定地打赌，我们可能永远不会知道最终的答案。我们当然不应该指望外星人会在短时间内造访。我知道电影和电视讲述的是不同的故事。With warp drive inStar Trekand jumps through hyperspace inStar Wars在美国，星际旅行看起来既酷又轻松。但这都是科幻小说，不是科学事实。尽管如此，我还是不愿低估人类的想象力或我们最终实现我们最初只能想象的事情的能力。想想早期的人类，他们凝视着浩瀚的海洋，想象着他们有朝一日可能到达的未知领域。或是第一批渴望仰望天空、梦想飞翔的人。所以，谁能说最终我们永远不会去恒星旅行或在其他行星上找到生命的证据呢?

有些人会坚持认为，在某种意义上，我们是否孤独并不重要——尤其是当我们认为自己永远没有机会遇到外星生命形式的时候。如果我们永远无法从其他星球上的居民那里了解到任何东西，我们为什么要花时间去寻找呢?这意味着我们所能发现的关于它们的一切都没有任何实际意义。此外，还有一种危险是，我们无拘无束的想象力会让我们看不到真正重要的东西。地球上有生命!我们有很多工作要做——疾病要治愈，社会错误要纠正，环境要拯救。在这种情况下，把大笔的钱花在可能有生命存在的微小希望上——我们几乎肯定不会遇到生命，即使它确实存在——似乎有点可耻!

然而，我内心的幻想家却想要反抗这种世俗的思维。即使我们注定永远无法与它近距离接触，但只要发现外星生命……任何一种生命……微生物、老鼠或小绿人……都将是人类历史上最具影响力的发现之一。它将与哥白尼、牛顿、达尔文、沃森、克里克和爱因斯坦的发现齐名。这将改变一切。它将彻底改变我们对自己和我们在宇宙中的位置的认识。认为基督教的。它教导我们是按照上帝的形象和样式创造的，我们是他神圣计划的中心。如果事实证明宇宙中充满了智慧生命，也许我们真的只是这个伟大计划中的一小部分玩家。

Now, a lot of us havealready gone a long way in that direction. Thanks to modern astronomy and cosmology, we know, for example, that we inhabit one small planet around one insignificant star, in one galaxy in a universe that contains untold numbers of other galaxies and stars and, probably planets too. And I grant that there is a legitimate question about whether it’s worth spending the resources it would take to find out about them. Whether we’re all alone in the universe or it’s crowded with life, we humans will still live and love and fight and die just the same as we always have.

But human curiosity isn’t going to be satisfied just by earthbound answers to earthbound questions. Something deep within us wants to know what, if anything, is out there. I mean suppose you knew that evolution has had a million different chances, on a million different planets, to design intelligent life from scratch. Wouldn’t that blow your mind? Wouldn’t you want to know how humans compare to other intelligent life forms? Whether we’re at the pinnacle or nadir of all that evolution? I would.

On the other hand, we could also be in for some rather unpleasant surprises. Suppose that someday we do manage to make contact with advanced aliens. Think about it fromtheirpoint of view. After all their efforts to reach us, all the excitement and wonder about the possible wisdom they might gain, all they end up with is... us. Would you really want to be around to witness their cosmic disappointment?