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Somewhere out there in that vast universe, there must surely be countless other planets teeming with life, but why don't we see any evidence of it? Well, this is the famous question asked by Enrico Fermi in 1950: "Where is everybody?" Conspiracy theorists claim that UFOs are visiting all the time and the reports are just being covered up, but honestly, they aren't very convincing. But that leaves a real riddle. In the past year, the Kepler space observatory has found hundreds of planets just around nearby stars, and if you extrapolate that data, it looks like there could be half a trillion planets just in our own galaxy. If any one in 10,000 has conditions that might support a form of life, that's still 50 million possible life-harboring planets right here in the Milky Way. So here's the riddle. Our Earth didn't form until about 9 billion years after the Big Bang. Countless other planets in our galaxy should have formed earlier and given life a chance to get underway billions or certainly many millions of years earlier than happened on Earth. If just a few of them had spawned intelligent life and started creating technologies, those technologies would have had millions of years to grow in complexity and power. On Earth, we've seen how dramatically technology can accelerate in just 100 years. In millions of years, an intelligent alien civilization could easily have spread out across the galaxy, perhaps creating giant energy-harvesting artifacts, or fleets of colonizing spaceships, or glorious works of art that fill the night sky. At the very least, you'd think they'd be revealing their presence, deliberately or otherwise, through electromagnetic signals of one kind or another. And yet we see no convincing evidence of any of it. Why? Well, there are numerous possible answers, some of them quite dark. Maybe a single, superintelligent civilization has indeed taken over the galaxy, and has imposed strict radio silence because it's paranoid of any potential competitors. It's just sitting there ready to obliterate anything that becomes a threat. Or maybe they're not that intelligent. Or perhaps, the evolution of an intelligence capable of creating sophisticated technology is far rarer than we've assumed. After all, it's only happened once on Earth in 4 billion years. Maybe even that was incredibly lucky. Maybe we are the first such civilization in our galaxy. Or, perhaps, civilization carries with it the seeds of its own destruction through the inability to control the technologies it creates. But there are numerous more hopeful answers. For a start, we're not looking that hard, and we're spending a pitiful amount of money on it. Only a tiny fraction of the stars in our galaxy have really been looked at closely for signs of interesting signals. And perhaps, we're not looking the right way. Maybe as civilizations develop, they quickly discover communication technologies far more sophisticated and useful than electromagnetic waves. Maybe all the action takes place inside the mysterious recently discovered dark matter, or dark energy, that appear to account for most of the universe's mass. Or maybe we're looking at the wrong scale. Perhaps intelligent civilizations come to realize that life is ultimately just complex patterns of information interacting with each other in a beautiful way, and that can happen more efficiently at a small scale. So just as on Earth, clunky stereo systems have shrunk to beautiful, tiny iPods, maybe intelligent life itself, in order to reduce its footprint on the environment, has turned itself microscopic, so the Solar System might be teeming with aliens, and we're just not noticing them. Maybe the very ideas in our heads are a form of alien life. Well, okay, that's a crazy thought. The aliens made me say it. But it is cool that ideas do seem to have a life all of their own, and that they outlive their creators. Maybe biological life is just a passing phase. Well, within the next 15 years, we could start seeing real spectroscopic information from promising nearby planets that will reveal just how life-friendly they might be. And meanwhile SETI, the Search for Extra-Terrestrial Intelligence, is now releasing its data to the public so that millions of citizen scientists, maybe including you, can bring the power of the crowd to join the search. And here on Earth, amazing experiments are being done to try to create life from scratch, life that might be very different from the DNA forms we know. All of this will help us understand whether the universe is teeming with life or, whether indeed, it's just us. Either answer, in its own way, is awe-inspiring, because even if we are alone, 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. And I have one more piece of good news for you. The quest for knowledge and understanding never gets dull. It doesn't. It's actually the opposite. The more you know, the more amazing the world seems. And it's the crazy possibilities, the unanswered questions, that pull us forward. So, stay curious.
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 但为什么我们没有找到任何证据呢? 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?” 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 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 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 如果更进一步你推测一下这个数据 那看起来有上万亿颗行星 在我们的银河系里面 如果一万颗中有一个 有条件来形成生命 那也有5千万个有生命的星球 就在我们的银河系中 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 我们银河系中有无数其他行星 都有可能在之前形成,并且有机会产生生命 十几亿年,或至少是几百万年 早于地球的形成 即使它们只有少数产生了智能生命 并且产生了科技 这些科技将会有几百万年的时间 来发展到很复杂,很强大的水平 在地球上 我们看到了 科技仅在100年里面就大幅发展 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 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 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 主动地告诉我们,或者是 通过某种磁场信号 但我们没看到任何这种证据 为什么呢? 我们现在有很多可能的答案 有些听起来比较黑暗 或许有一个超级智能的文明 已经控制了银河系 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 他们时刻准备着干扰 一切有威胁的东西 另有可能是,他们不是很智能 或者智能生命的进化 到能够到产生复杂科技的过程 比我们想象的要少见很多 毕竟,这在地球上40亿年也就发生了一次 也许那已经很幸运了 或许我们是银河系里第一个文明 或者那些外星文明自己 携带着可以摧毁自己的祸根 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 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 我们银河系里面至少有少部分 已经被仔细观测过 又或者,我们寻找的方式错了 也许随着文明的发展 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 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,它看起来占据了宇宙的大部分质量 或者我们的比例错了 可能是智能文明发现 生命最终是复杂的模式和信息 以一种美妙的方式相互交互 并且发现缩小比例之后效率更高 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 为了减少自己对环境的影响 便把自己变成微生物 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 也可能我们脑子里的想法就是一种外来生命的形式 好吧,这有点夸张 是外星人让我说的 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 或许生物的生命只不过是一个短暂的阶段 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,并且会告诉我们那里的生命状况 与此同时,SETI(寻找外星智能)组织 已经向公众发布它的数据 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 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 一种跟我们知道的DNA形式有很大差别的生命 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 不管怎样, 那都让人敬畏 因为即使我们这么孤独 那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 我还有一个好消息要告诉你 对知识和理解的探求永远不会枯燥 不会的。而且正好相反,你知道的越多 这个世界就越让人惊讶 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