外星生命是否存在吗？科学家终于给出了答案！｜TED演讲

演说者：Sarah Rugheimer

演说题目：外星生命真的存在吗？

浩瀚的宇宙中是否存在外星生命？如果有，TA们长什么样子呢？TA们又是如何生存的？人们对于外星生命的好奇心从未减弱。在各式各样的外星人电影中，人们更是充分发挥想象，展现出千奇百怪、精彩纷呈的外星生命场景！

[SHAPE YOUR FUTURE]

[塑造你的未来]

I want to find aliens. Finding life on another planet is not just going to be a little hard, it's going to be very hard. But for the first time in human history, we have a chance to detect signs of life on another planet. Or maybe we've already detected it on Venus. Or maybe not.

我想要找到外星人。要在另一颗星球上找到生命，绝对不会只有一点难，而是非常困难。不过人类史上第一次我们有机会探测到另一个星球上的生命迹象。我们可能已经在金星上找到了。或着其实没有。

There are still two big hurdles when it comes to confirming life on another world. The first is building a telescope big enough to do this, and the second is interpreting what we will find. When we think of extraterrestrial life, we tend to think of aliens like funny little green men, not aliens as single-celled microbes.

目前还有两个很大的障碍，如果要确认另一个世界的生命。第一个是要做一个够大的望远镜，第二个则是理解我们的发现。当我们想到外星生命，我们倾向于想象有趣的绿色外星人，而不是外星的单细胞微生物。

But it's actually detecting signs of microbial life on another planet that I'm most optimistic about, and what I focus my research on. I model how a star's high-energy radiation can make gases from microbes harder or easier to see with future telescopes.

但实际上探测在另一个星球上微生物存活的迹象，是我觉得最有可能，也是我专注在研究的。我研究恒星的高能量辐射是如何影响微生物产生气体的可见度难易，如果使用未来望远镜的话。

Microbes have dominated our planet's biosphere for most of Earth's history. They've been emitting gases that can be seen in our atmosphere -- even light years away -- for billions of years. Now, if an alien astronomer were looking at Earth, they would probably detect gases like oxygen, methane and nitrous oxide before detecting signs of us.

地球历史上的大部分时间，微生物主宰了我们星球的生物圈。它们排出的气体能够在我们的大气中被看见，就算是在数光年外，并持续了几十亿年。假如一个外星的天文学家在观察地球，他们可能会先探测到象是氧气、甲烷和一氧化二氮等气体，在发现我们存在的迹象之前。

Even with an active biosphere like Earth's, most of the gases that indicate life are coming from single-celled microbes, not from animals. This is what we'll try to do in the next decade of astronomy -- try to find signs of microbial life on planets orbiting other stars. But the technology to detect the atmosphere of a planet the size of Earth around another sun is incredibly difficult.

就算地球拥有这般活跃的生物圈，大部分生命迹象气体都来自单细胞微生物，而不是动物。天文学的下一个十年，这就是我们打算要做的：在其他行星系的星球上寻找微生物的迹象。但探测这种大气的技术，对于与地球差不多大小并绕着另个太阳绕的星球，是非常困难的。

It's like trying to determine the size of a firefly in front of a spotlight while looking from another continent. What's amazing is that with telescopes in the 2020s, we're overcoming this technological barrier.

就好比要判断灯光下萤火虫的大小，而且是从另一个洲看。但令人惊喜的是，2020年代的望远镜，可以克服这个技术的障碍。

The second issue defining alien life will be to interpret what these biosignature gases actually mean. Twenty-one percent of our atmosphere is oxygen, and nearly all of that oxygen comes from life. So here's the tricky question: Would detecting oxygen on another planet mean life? No, not necessarily, because we know of ways to get oxygen without biology.

第二个定义外星生命的问题，则是如何解释生物特征气体的意义。地球大气中有百分之二十一的氧气，而这些氧气几乎都来自于生物。所以棘手问题来了：在另一个星球发现氧气，是否等于发现生命？不是。不一定。因为我们知道没有生物也能产生氧气的方法。

I try to understand a planet's geology and its star's radiation so that we can better identify a true life signal. And this is what makes the preliminary detection on Venus of phosphine, a potential biosignature gas, so compelling but also so confusing. Venus is not where we expected to find life.

我试着了解星球的地质以及它恒星的辐射，以让我们更能确认真正的生命迹象。这也就是为何在金星上初步发现的磷化氢，一种潜在的生物特征气体，引人注目的同时也很让人疑惑。金星并不是我们预期会有生命的地方。

It is a hellish world, with a surface temperature of nearly 900 degrees Fahrenheit. Could life be floating in the more temperate upper atmosphere? But then how would such life eat and reproduce? This discovery will have to be vetted over the coming decade.

它的环境就像地狱，地表温度将近华氏九百度。还是生命可能漂浮在高大气层？但这些生命要如何进食跟繁殖？这个发现会需要在接下来的十年接受严格检视。

First, we must verify the detection of phosphine itself, and then later, we would have to confirm that this gas is coming from life and not from some unexpected geological or photochemical process. If true, this would be one of the most profound discoveries of our generation. If it turns out that we were fooled, that we mistook this gas for biology when it's from some other process, we will have a sobering lesson to apply to planets orbiting distant stars.

第一，我们得确认发现磷化氢这件事。之后，我们要确定这气体来自生命。而不是意料之外的地质或光化学过程。如果是真的，这将是我们这个世代最重要的发现之一。假设我们错了，将此气体误会成与生物相关，而实际上是透过其他方式产生的话，会让我们在研究更遥远的行星系时多一点省思。

Venus is close -- literally, our next-door neighbor -- and yet we still have trouble understanding it. The planets we're finding orbiting other stars are weird and unexpected. Some have the density of cotton candy, and others rain molten iron.

金星很近，真的就是我们隔壁邻居，但我们却连了解它都有困难。我们发现的太阳系以外行星，很奇怪并且出乎意料。有些的密度就像棉花糖，有些则会下熔铁的雨。

And most stars are different from our sun, with high-energy flares that can make it difficult for life. So the more we're looking at different biosignature gases, the more we realize that there's no single gas that's enough to understand a planet and to claim alien life. It is just really difficult to distinguish life from nonlife from light years away.

而且大部分恒星跟太阳不一样，高能量的火焰让生命的存在很困难。所以当我们看越多不同生物特征气体时，我们就更能意识到没有特定一种气体，足够让我们了解一个星球并且代表外星生物的存在。要区分生物与非生物很困难，从数光年远的地方。

And here's where the ambiguity lies. How will we know if a clue is a sign of life or is not? Well, first, we'll need to understand as much as we can about a planet's geology and the star it orbits. We'll learn vital lessons by exploring our own solar system in places such as Venus and Mars. We're getting closer to answering one of humanity's biggest questions: Are we alone in the universe? Any claim will be hotly debated.

这部分是个模糊地带。我们要如何辨别一个线索是否代表生命的迹象？第一点，我们需要尽可能了解一个星球的地质和它环绕的恒星。我们可以藉由探索所在的太阳系来更学习宝贵的经验，例如金星跟火星。我们距离人类最大问题之一的解答越来越近：宇宙是否只有我们存在？任何一种主张都会被激烈的讨论。

So basically, I'm stretched between two desires. I want to find alien life, but likely will not have a clear answer. And that's OK; science is nuanced and self-correcting. It's what I love about it. Science is about balancing this duality of skepticism and of hope. We won't be able to teleport ourselves to another planet and take pictures of alien kangaroos jumping around.

基本上，我渴望的有两点。我希望能找到外星生物，但可能不会有明确答案。但没关系，科学很微妙，而且会自我修正。这就是为什么我喜欢它。科学就是在怀疑与希望两者之间取得平衡。我们无法瞬间移动到其他星球，然后把外星袋鼠跳来跳去的样子拍下来。

And without an intelligent "Hello, Earthlings!" signal, we might still feel lonely, even if we find out we're not alone in the universe. Despite these challenges, I'm super excited about alien microbes and what they could teach us. Even if we find just one other sign of life, then likely the universe is teeming with it, from single-celled to complex.

在还没收到「你好地球人」的讯号之前，我们可能还是会感到孤单，就算我们发现自己在宇宙里并不是唯一的。尽管有这些挑战，我对于外星微生物还是很兴奋，也很期待它们能教我们什么。就算我们只再找到一个生命存在的证据，那很有可能整个宇宙都充满了生命，从单细胞到更复杂的。

If we search for decades and find nothing, then that is equally humbling. But we must try. We must do this search even when it means sitting with uncertainty along the way. Thank you.

如果我们花了数十年都没找到，这结果同样令人谦卑。但我们还是得尝试。我们还是要继续找寻，就算沿路都充满着不确定性。谢谢。

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