Why Can't We See Evidence of Alien Life?

为什么我们没有发现外星生命的痕迹？

翻译人员: Hom Liu 校对人员: Tracie Chen

（音乐）

在我们这个广阔无边的宇宙中

Somewhere out there in that vast universe,

一定有无数行星存在着生命

there must surely be countless other planets teeming with life,

但为什么我们没有找到任何证据呢？

but why don't we see any evidence of it?

这是恩里科·费米在1950年提出的一个著名问题

Well, this is the famous question asked by Enrico Fermi in 1950:

"Where is everybody?"

“大家都到哪去了？”

Conspiracy theorists claim that UFOs are visiting all the time

阴谋论专家们宣称不明飞行物常常光顾地球

and the reports are just being covered up,

但所有报道都被屏蔽了

but honestly, they aren't very convincing.

老实地说，他们不是很可信

But that leaves a real riddle.

不过这留给我们一个真正的谜团

In the past year, the Kepler space observatory

去年，开普勒太空天文台已经发现

has found hundreds of planets just around nearby stars,

在附近的星星中有上百个行星

如果更进一步你推测一下这个数据

and if you extrapolate that data,

it looks like there could be half a trillion planets

那看起来有上万亿颗行星

在我们的银河系里面

just in our own galaxy.

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

那也有5千万个有生命的星球

right here in the Milky Way.

就在我们的银河系中

谜团就在这里

So here's the riddle.

Our Earth didn't form

我们的地球直到宇宙大爆炸90亿年之后才形成

until about 9 billion years after the Big Bang.

我们银河系中有无数其他行星

Countless other planets in our galaxy should have formed earlier

都有可能在之前形成，并且有机会产生生命

and given life a chance to get underway

十几亿年，或至少是几百万年

billions or certainly many millions of years

earlier than happened on Earth.

早于地球的形成

If just a few of them had spawned intelligent life

即使它们只有少数产生了智能生命

and started creating technologies,

并且产生了科技

这些科技将会有几百万年的时间

those technologies would have had millions of years

来发展到很复杂，很强大的水平

to grow in complexity and power.

在地球上

On Earth,

我们看到了

we've seen how dramatically technology can accelerate

科技仅在100年里面就大幅发展

in just 100 years.

在几百年的时间里，一个智能生命的文明

In millions of years, an intelligent alien civilization

could easily have spread out across the galaxy,

能够很容易地扩展到整个银河系

perhaps creating giant energy-harvesting artifacts,

或者创造出巨大的能吸收能量的东西

or fleets of colonizing spaceships,

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

至少，他们会透露他们的存在

At the very least, you'd think they'd be revealing their presence,

主动地告诉我们，或者是

deliberately or otherwise,

通过某种磁场信号

through electromagnetic signals of one kind or another.

但我们没看到任何这种证据

And yet we see no convincing evidence of any of it.

为什么呢？

Why?

Well, there are numerous possible answers,

我们现在有很多可能的答案

some of them quite dark.

有些听起来比较黑暗

Maybe a single, superintelligent civilization

或许有一个超级智能的文明

已经控制了银河系

has indeed taken over the galaxy,

and has imposed strict radio silence

并且强行屏蔽了所有广播信号

because it's paranoid of any potential competitors.

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

他们时刻准备着干扰

anything that becomes a threat.

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

或者智能生命的进化

capable of creating sophisticated technology

到能够到产生复杂科技的过程

is far rarer than we've assumed.

比我们想象的要少见很多

After all,

毕竟，这在地球上40亿年也就发生了一次

it's only happened once on Earth

in 4 billion years.

Maybe even that was incredibly lucky.

也许那已经很幸运了

Maybe we are the first such civilization in our galaxy.

或许我们是银河系里第一个文明

或者那些外星文明自己

Or, perhaps, civilization carries with it

the seeds of its own destruction

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

但也有很多更有让人感到有希望的答案

But there are numerous more hopeful answers.

For a start, we're not looking that hard,

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

and we're spending a pitiful amount of money on it.

我们银河系里面至少有少部分

Only a tiny fraction of the stars in our galaxy

have really been looked at closely for signs of interesting signals.

已经被仔细观测过

又或者，我们寻找的方式错了

And perhaps, we're not looking the right way.

也许随着文明的发展

Maybe as civilizations develop,

they quickly discover communication technologies

他们迅速发现了其他通信手段

far more sophisticated and useful than electromagnetic waves.

比起电磁波更加复杂并且有用

或许这些东西

Maybe all the action takes place

inside the mysterious recently discovered dark matter,

都发生在最近发现的暗物质里面

or dark energy,

或是暗能量，它看起来占据了宇宙的大部分质量

that appear to account for most of the universe's mass.

或者我们的比例错了

Or maybe we're looking at the wrong scale.

可能是智能文明发现

Perhaps intelligent civilizations come to realize

that life is ultimately just complex patterns of information

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，或者说智能生命

maybe intelligent life itself,

为了减少自己对环境的影响

in order to reduce its footprint on the environment,

has turned itself microscopic,

便把自己变成微生物

so the Solar System might be teeming with aliens,

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

and we're just not noticing them.

也可能我们脑子里的想法就是一种外来生命的形式

Maybe the very ideas in our heads are a form of alien life.

Well, okay, that's a crazy thought.

好吧，这有点夸张

The aliens made me say it.

是外星人让我说的

But it is cool that ideas do seem to have a life all of their own,

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

and that they outlive their creators.

或许生物的生命只不过是一个短暂的阶段

Maybe biological life is just a passing phase.

在接下来的15年里

Well, within the next 15 years,

we could start seeing real spectroscopic information

我们将能够看到真正的光谱信息

from promising nearby planets

它们来自周边的行星，并且会告诉我们那里的生命状况

that will reveal just how life-friendly they might be.

与此同时，SETI（寻找外星智能）组织

And meanwhile SETI,

the Search for Extra-Terrestrial Intelligence,

已经向公众发布它的数据

is now releasing its data to the public

so that millions of citizen scientists, maybe including you,

可以让几百万市民科学家，说不定你也在其中

can bring the power of the crowd to join the search.

一起参与这个搜寻行动

在地球上，让人惊讶的实验已经完成

And here on Earth, amazing experiments are being done

实验尝试从零开始制作生命

to try to create life from scratch,

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

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

whether the universe is teeming with life

or, whether indeed,

还是确实只有我们存在

it's just us.

不管怎样，

Either answer, in its own way,

is awe-inspiring,

那都让人敬畏

because even if we are alone,

因为即使我们这么孤独

the fact that we think and dream,

那我们现在所想所问的这些问题

and ask these questions

可能是这个宇宙中最重要的事情

might yet turn out to be one of the most important facts

about the universe.

我还有一个好消息要告诉你

And I have one more piece of good news for you.

The quest for knowledge and understanding never gets dull.

对知识和理解的探求永远不会枯燥

It doesn't. It's actually the opposite.

不会的。而且正好相反，你知道的越多

The more you know,

the more amazing the world seems.

这个世界就越让人惊讶

And it's the crazy possibilities, the unanswered questions,

正是这些疯狂大胆的可能性，和没有被回答的问题

that pull us forward.

推动我们前进。所以，要保持好奇的心态

So, stay curious.