Somewhere out there in that vast universe, there must surely be countless other planets teeming with life,
在我们这个广阔无边的宇宙中，一定有无数行星存在着生命，
but why don't we see any evidence of it?
但为什么我们没有找到任何证据呢？
Well, this is the famous question asked by Enrico Fermi in 1950: 'Where is everybody?'
这是恩里科·费米在1950年提出的一个著名问题，“大家都到哪去了？”
Conspiracy theorists claim that UFOs are visiting all the time and the reports are just being covered up,
阴谋论专家们宣称不明飞行物常常光顾地球，但所有报道都被屏蔽了，
but honestly, they aren't very convincing. But that leaves a real riddle.
老实地说，他们不是很可信。不过这留给我们一个真正的谜团。
In the past year, the Kepler space observatory has found hundreds of planets just around nearby stars,
去年，开普勒太空天文台已经发现，在附近的星星中有上百个行星，
and if you extrapolate that data, it looks like there could be half a trillion planets just in our own galaxy.
如果你更进一步推测一下这个数据，在我们的银河系里面，看起来有上万亿颗行星。
If any one in 10,000 has conditions that might support a form of life,
如果一万颗中有一个有条件来形成生命，
that's still 50 million possible life-harboring planets right here in the Milky Way.
那在我们的银河系中也有5千万个有生命的星球。
So here's the riddle. Our Earth didn't form until about 9 billion years after the Big Bang.
谜团就在这里。我们的地球直到宇宙大爆炸90亿年之后才形成。
Countless other planets in our galaxy should have formed earlier
我们银河系中有无数其他行星都有可能在之前形成，
and given life a chance to get underway billions or certainly many millions of years earlier than happened on Earth.
并且有机会早于地球十几亿年或至少是几百万年时间来产生生命。
If just a few of them had spawned intelligent life and started creating technologies,
即使它们只有少数产生了智能生命，并且产生了科技，
those technologies would have had millions of years to grow in complexity and power.
这些科技也将会有几百万年的时间来发展到很复杂、很强大的水平。
On Earth, we've seen how dramatically technology can accelerate in just 100 years.
在地球上，我们看到了科技仅在100年里面就大幅发展。
In millions of years, an intelligent alien civilization could easily have spread out across the galaxy,
在几百年的时间里，一个智能生命的文明，能够很容易地扩展到整个银河系，
perhaps creating giant energy-harvesting artifacts, or fleets of colonizing spaceships,
或者创造出巨大的能吸收能量的东西，或者是一直殖民星际舰队，
or glorious works of art that fill the night sky.
或者是在夜空中做出让人惊叹的艺术品，
At the very least, you'd think they'd be revealing their presence,
至少，他们会透露他们的存在，
deliberately or otherwise, through electromagnetic signals of one kind or another.
主动地告诉我们，或者是通过某种磁场信号。
And yet we see no convincing evidence of any of it. Why?
但我们没看到任何这种证据，为什么呢？
Well, there are numerous possible answers, some of them quite dark.
我们现在有很多可能的答案，有些听起来比较黑暗。
Maybe a single, superintelligent civilization has indeed taken over the galaxy,
或许有一个超级智能的文明已经控制了银河系，
and has imposed strict radio silence because it's paranoid of any potential competitors.
并且强行屏蔽了所有广播信号，因为他们对一切可能的竞争者过于敏感。
It's just sitting there ready to obliterate anything that becomes a threat.
他们时刻准备着干扰一切有威胁的东西。

Or maybe they're not that intelligent.
另有可能是，他们不是很智能。
Or perhaps, the evolution of an intelligence capable of creating sophisticated technology is far rarer than we've assumed.
或者智能进化到能够产生复杂科技的过程，比我们想象的要少见很多，
After all, it's only happened once on Earth in 4 billion years.
毕竟，这在地球上40亿年也就发生了一次。
Maybe even that was incredibly lucky. Maybe we are the first such civilization in our galaxy.
也许那已经很幸运了，或许我们是银河系里第一个文明。
Or, perhaps, civilization carries with it the seeds of its own destruction
或者那些外星文明自己携带着可以摧毁自己的祸根，
through the inability to control the technologies it creates.
因为没有能力控制自己所产生的科技。
But there are numerous more hopeful answers.
但也有很多更让人感到有希望的答案。
For a start, we're not looking that hard, and we're spending a pitiful amount of money on it.
我觉得，我们并没有太花心思去寻找。我们只投入了一丁点钱。
Only a tiny fraction of the stars in our galaxy have really been looked at closely for signs of interesting signals.
我们银河系里面至少有少部分已经被仔细观测过。
And perhaps, we're not looking the right way. Maybe as civilizations develop,
又或者，我们寻找的方式错了。也许随着文明的发展，
they quickly discover communication technologies far more sophisticated and useful than electromagnetic waves.
他们迅速发现了其他通信手段，比起电磁波更加复杂并且有用。
Maybe all the action takes place inside the mysterious recently discovered dark matter, or dark energy,
或许这些东西都发生在最近发现的暗物质里面，或是暗能量，
that appear to account for most of the universe's mass.
它看起来占据了宇宙的大部分质量。
Or maybe we're looking at the wrong scale.
或者我们的比例错了。
Perhaps intelligent civilizations come to realize that life is ultimately just complex patterns of information
可能是智能文明意识到，生命最终是复杂的模式和信息，
interacting with each other in a beautiful way,
以一种美妙的方式相互交互，
and that can happen more efficiently at a small scale.
并且发现缩小比例之后效率更高。
So just as on Earth, clunky stereo systems have shrunk to beautiful, tiny iPods,
就像地球上笨重的立体音响缩小到小巧的iPod随身听，
maybe intelligent life itself, in order to reduce its footprint on the environment, has turned itself microscopic,
或者说智能生命为了减少自己对环境的影响，便把自己变成微生物，
so the Solar System might be teeming with aliens, and we're just not noticing them.
所以太阳系可能已经到处存在外星生命，只不过我们没察觉。
Maybe the very ideas in our heads are a form of alien life.
也可能我们脑子里的想法就是一种外来生命的形式。
Well, okay, that's a crazy thought. The aliens made me say it.
好吧，这有点夸张。是外星人让我说的。
But it is cool that ideas do seem to have a life all of their own, and that they outlive their creators.
但这很有趣，脑子里的想法好像自己有生命，并且活得比创造者还久。
Maybe biological life is just a passing phase.
或许生物的生命只不过是一个短暂的阶段。
Well, within the next 15 years, we could start seeing real spectroscopic information from promising nearby planets
在接下来的15年里，我们将能够看到真正的光谱信息，它们来自周边的行星，
that will reveal just how life-friendly they might be.
并且会告诉我们那里的生命状况。
And meanwhile SETI, the Search for Extra-Terrestrial Intelligence, is now releasing its data to the public
与此同时，SETI（寻找外星智能）组织，已经向公众发布它的数据，
so that millions of citizen scientists, maybe including you, can bring the power of the crowd to join the search.
可以让几百万市民科学家，说不定你也在其中，一起参与这个搜寻行动，
And here on Earth, amazing experiments are being done to try to create life from scratch,
在地球上，让人惊讶的实验已经完成，实验尝试从零开始制作生命，
life that might be very different from the DNA forms we know.
一种跟我们知道的DNA形式有很大差别的生命。
All of this will help us understand whether the universe is teeming with life or, whether indeed, it's just us.
所有这些都会帮助我们去了解这个宇宙到底是不是充斥着生命，还是确实只有我们存在。
Either answer, in its own way, is awe-inspiring, because even if we are alone,
不管怎样，那都让人敬畏，因为即使我们这么孤独，
the fact that we think and dream, and ask these questions might yet turn out to be one of the most important facts about the universe.
我们现在所想所问的这些问题，可能是这个宇宙中最重要的事情。
And I have one more piece of good news for you.
我还有一个好消息要告诉你。
The quest for knowledge and understanding never gets dull. It doesn't.
对知识和理解的探求永远不会枯燥。不会的。
It's actually the opposite. The more you know, the more amazing the world seems.
而且正好相反。你知道的越多，这个世界就越让人惊讶。
And it's the crazy possibilities, the unanswered questions, that pull us forward. So, stay curious.
正是这些疯狂大胆的可能性和没有被回答的问题，推动我们前进。所以，要保持好奇的心态，