I saw a UFO once. I was eight or nine, playing in the street with a friend who was a couple of years older, and we saw a featureless silver disc hovering over the houses. We watched it for a few seconds, and then it shot away incredibly quickly. Even as a kid, I got angry it was ignoring the laws of physics. We ran inside to tell the grown-ups, and they were skeptical -- you'd be skeptical too, right? I got my own back a few years later: one of those grown-ups told me, "Last night I saw a flying saucer. I was coming out of the pub after a few drinks." I stopped him there. I said, "I can explain that sighting."
我见过一次不明飞行物。 那时我八、九岁, 和一个比我大几岁的朋友在街上玩, 我们发现一个普通的 银色碟子在上空盘旋。 我们盯着它看了几秒钟, 然后它飞走了,速度极快。 虽然我只是个小孩, 但我依然感到气愤, 因为它不符合物理规律。 我们跑回家告诉大人们, 但他们表示很怀疑—— 谁都会怀疑的,对吧? 几年后,我扳回一局: 那些大人中的一个对我说, “昨晚我看到一个飞碟, 我当时刚在酒吧喝了几杯出来。” 我当时就打断他说, “我可以解释你看到的是什么。”
(Laughter)
(笑声)
Psychologists have shown we can't trust our brains to tell the truth. It's easy to fool ourselves. I saw something, but what's more likely -- that I saw an alien spacecraft, or that my brain misinterpreted the data my eyes were giving it? Ever since though I've wondered: Why don't we see flying saucers flitting around? At the very least, why don't we see life out there in the cosmos? It's a puzzle, and I've discussed it with dozens of experts from different disciplines over the past three decades. And there's no consensus. Frank Drake began searching for alien signals back in 1960 -- so far, nothing. And with each passing year, this nonobservation, this lack of evidence for any alien activity gets more puzzling because we should see them, shouldn't we?
心理学家已经证明, 我们不能相信自己的大脑 说的都是事实。 我们很容易被自己欺骗。 我看到了某种东西, 但哪种情况可能性更大—— 我看到的是外星飞船? 还是我的大脑误解了眼睛传给它的数据? 从那以后,我一直在想: 为什么我们在周围看不到飞碟呢? 至少, 我们为什么看不到 宇宙中的其它生命呢? 这是一个谜, 过去的三十年里,我与不同领域的 数十位专家讨论过这个问题。 我们并没有达成共识。 弗兰克 · 德雷克从1960年 开始寻找外星信号—— 到目前为止,什么都没找到。 一年又一年, 什么也观测不到, 没有任何外星活动的证据, 这越来越让人困惑, 因为我们应该能看到它们的,不是吗?
The universe is 13.8 billion years old, give or take. If we represent the age of the universe by one year, then our species came into being about 12 minutes before midnight, 31st December. Western civilization has existed for a few seconds. Extraterrestrial civilizations could have started in the summer months. Imagine a summer civilization developing a level of technology more advanced than ours, but tech based on accepted physics though, I'm not talking wormholes or warp drives -- whatever -- just an extrapolation of the sort of tech that TED celebrates. That civilization could program self-replicating probes to visit every planetary system in the galaxy. If they launched the first probes just after midnight one August day, then before breakfast same day, they could have colonized the galaxy. Intergalactic colonization isn't much more difficult, it just takes longer. A civilization from any one of millions of galaxies could have colonized our galaxy.
宇宙已经存在了大概 138亿年了。 如果我们用一年来代表宇宙的年龄, 那么我们这个物种形成于 12月31日午夜前的12分钟。 西方文明刚出现几秒钟。 而外星文明可能是夏季开始的。 想象一个夏季出现的文明 开发出比我们更先进的技术, 但我是说符合公认的 物理理论的技术, 而不是虫洞或曲速引擎 ——那种类型的—— 我只说像TED在这儿庆祝的 那种技术的进步。 这个文明也许会编写 可自我复制的探测器, 去访问银河系中的每一个星系。 如果他们在8月的某天午夜, 发射了第一颗探测器, 那么在当天早餐之前, 他们可能就已经统治银河系了。 银河系之外的星际统治也不算太难, 只是要多花点时间而已。 在数百万星系中, 任何一个星系的文明 都有可能统治我们的银河系。
Seems far-fetched? Maybe it is, but wouldn't aliens engage in some recognizable activity -- put worldlets around a star to capture free sunlight, collaborate on a Wikipedia Galactica, or just shout out to the universe, "We're here"?
听起来很牵强? 也许是的, 但外星人难道就不做一些 可以被探测到的活动吗? 比如在恒星周围造个小世界获取阳光, 合作一个星际维基百科, 或者只是对着宇宙大喊: “我们在这里!”
So where is everybody? It's a puzzle because we do expect these civilizations to exist, don't we? After all, there could be a trillion planets in the galaxy -- maybe more.
那么他们到底在哪儿? 这是个谜,因为我们确实认为 有这种文明存在,不是吗? 毕竟,银河系中可能有 一万亿颗星球—— 也许更多。
You don't need any special knowledge to consider this question, and I've explored it with lots of people over the years. And I've found they often frame their thinking in terms of the barriers that would need to be cleared if a planet is to host a communicative civilization. And they usually identify four key barriers.
你不需要任何专业知识 来思考这个问题, 多年来,我和很多人 都探讨过这个问题。 我发现他们对这个问题的 思考有个标准, 就是如果一个星球要 承载可交流的文明, 它需要清除一些障碍。 他们通常会考虑四个关键障碍。
Habitability -- that's the first barrier. We need a terrestrial planet in that just right "Goldilocks zone," where water flows as a liquid. They're out there. In 2016, astronomers confirmed there's a planet in the habitable zone of the closest star, Proxima Centauri -- so close that Breakthrough Starshot project plans to send probes there. We'd become a starfaring species. But not all worlds are habitable. Some will be too close to a star and they'll fry, some will be too far away and they'll freeze.
宜居性—— 这是第一个障碍。 我们需要一颗刚好位于 “适居带”中的陆地行星, 上面的水以液态形式流动。 这样的星球是存在的。 2016年,天文学家证实, 有一颗行星位于最近的恒星的 适居带中, 接近于半人马座—— 非常近,所以“突破摄星”工程 计划发送一个探测器过去。 我们已经成为 可以穿越星际的物种了。 但不是所有的星球都适合居住。 有些离恒星太近,会被烤焦, 有些离得太远,会被冻结。
Abiogenesis -- the creation of life from nonlife -- that's the second barrier. The basic building blocks of life aren't unique to Earth: amino acids have been found in comets, complex organic molecules in interstellar dust clouds, water in exoplanetary systems. The ingredients are there, we just don't know how they combine to create life, and presumably there will be worlds on which life doesn't start.
生命起源—— 从非生命中孕育出生命—— 这是第二个障碍。 构成生命的基本要素并非地球独有: 彗星上已经发现了氨基酸, 在星际尘埃云中的复杂有机分子, 在外层空间发现了水。 那些成分都是存在的, 我们只是不知道 它们如何结合起来创造生命, 而且可能在一些世界里, 生命还没有诞生。
The development of technological civilization is a third barrier. Some say we already share our planet with alien intelligences. A 2011 study showed that elephants can cooperate to solve problems. A 2010 study showed that an octopus in captivity can recognize different humans. 2017 studies show that ravens can plan for future events -- wonderful, clever creatures -- but they can't contemplate the Breakthrough Starshot project, and if we vanished today, they wouldn't go on to implement Breakthrough Starshot -- why should they? Evolution doesn't have space travel as an end goal. There will be worlds where life doesn't give rise to advanced technology.
第三个障碍是技术文明的发展。 有人说我们已经在和外星人 共享我们的星球。 2011年的一项研究表明, 大象可以合作解决问题。 2010年的研究表明, 人工饲养的章鱼可以识别不同的人。 2017年的研究表明, 乌鸦可以为未来的事件做规划—— 多么奇妙的、聪明的生物—— 但是它们想不出“突破摄星”计划, 如果今天,我们消失了, 它们也不会继续“突破摄星”之旅—— 它们为什么要去呢? 进化的最终目标又不是太空旅行。 有些世界里的生命 没有发明先进的技术。
Communication across space -- that's a fourth barrier. Maybe advanced civilizations choose to explore inner space rather than outer space, or engineer at small distances rather than large. Or maybe they just don't want to risk an encounter with a potentially more advanced and hostile neighbor. There'll be worlds where, for whatever reason, civilizations either stay silent or don't spend long trying to communicate.
跨太空通信——这是第四个障碍。 也许先进的文明选择探索内部空间, 而不是外太空, 或者在小范围内而不是大范围上活动。 或者,他们只是不想冒险, 遇到一个潜在的,更先进的敌对的邻居。 会有一些世界,无论出于什么原因, 那里的文明要么保持沉默, 要么不花太长的时间交流。
As for the height of the barriers, your guess is as good as anyone's. In my experience, when people sit down and do the math, they typically conclude there are thousands of civilizations in the galaxy. But then we're back to the puzzle: Where is everybody? By definition, UFOs -- including the one I saw -- are unidentified. We can't simply infer they're spacecraft. You can still have some fun playing with the idea aliens are here. Some say a summer civilization did colonize the galaxy and seeded Earth with life ... others, that we're living in a cosmic wilderness preserve -- a zoo. Yet others -- that we're living in a simulation. Programmers just haven't revealed the aliens yet. Most of my colleagues though argue that E.T. is out there, we just need to keep looking, and this makes sense. Space is vast. Identifying a signal is hard, and we haven't been looking that long. Without doubt, we should spend more on the search. It's about understanding our place in the universe. It's too important a question to ignore.
至于障碍的高度, 大家的猜测都差不多。 根据我的经验, 当人们进行数学计算, 通常得到的结论是, 银河系中存在数千个文明。 但我们又回到了刚才的谜题: 外星人到底在哪儿? 根据定义, 不明飞行物—— 包括我看到的那个—— 是身份“不明”的。 我们不能简单地推断 它们是宇宙飞船。 你仍然可以饶有兴趣地 想象着外星人就在这里。 有人认为,夏季文明确实统治了银河系, 并给地球播下了生命的种子…… 还有人认为,我们生活在 宇宙的野生保护区—— 动物园。 也有人说—— 我们生活在一个模拟世界里。 只是程序员还没安排外星人出场而已。 大多数我的同事认为 外星人是存在的, 只是我们仍需寻找, 这是有道理的。 宇宙空间是巨大的。 识别一个信号是很难的, 我们寻找的时间也不算很久。 毫无疑问,我们应该在搜寻上加大投入。 这有助于理解 我们在宇宙中的位置。 这个问题太重要了,不容忽视。
But there's an obvious answer: we're alone. It's just us. There could be a trillion planets in the galaxy. Is it plausible we're the only creatures capable of contemplating this question? Well, yes, because in this context, we don't know whether a trillion is a big number. In 2000, Peter Ward and Don Brownlee proposed the Rare Earth idea. Remember those four barriers that people use to estimate the number of civilizations? Ward and Brownlee said there might be more.
但有一个显而易见的答案: 我们是孤单的。 宇宙中只有我们存在。 银河系中可能有一万亿颗行星。 是否可能,我们是唯一有能力 思考这个问题的生物呢? 没错,因为在这种情况下, 我们不知道一万亿这个数量大不大。 2000年,彼得 · 瓦尔德和唐 · 布朗尼 提出了“稀有地球”的概念。 还记得人们用来 估算文明数量的四个障碍吗? 瓦尔德和布朗尼认为, 可能还有更多的障碍存在。
Let's look at one possible barrier. It's a recent suggestion by David Waltham, a geophysicist. This is my very simplified version of Dave's much more sophisticated argument. We are able to be here now because Earth's previous inhabitants enjoyed four billion years of good weather -- ups and downs but more or less clement. But long-term climate stability is strange, if only because astronomical influences can push a planet towards freezing or frying. There's a hint our moon has helped, and that's interesting because the prevailing theory is that the moon came into being when Theia, a body the size of Mars, crashed into a newly formed Earth. The outcome of that crash could have been a quite different Earth-Moon system. We ended up with a large moon and that permitted Earth to have both a stable axial tilt and a slow rotation rate. Both factors influence climate and the suggestion is that they've helped moderate climate change. Great for us, right? But Waltham showed that if the moon were just a few miles bigger, things would be different. Earth's spin axis would now wander chaotically. There'd be episodes of rapid climate change -- not good for complex life. The moon is just the right size: big but not too big. A "Goldilocks" moon around a "Goldilocks" planet -- a barrier perhaps.
咱们来看一个可能存在的障碍。 这是地球物理学家大卫 · 沃尔瑟姆 最近提出的建议。 这是我对大卫的复杂论证 做了简化处理的版本。 我们能够存在于此, 是因为地球的早期居民享受了 40亿年的好天气—— 时好时坏,但基本上是温和的。 但是气候的长期稳定是值得探究的, 因为仅仅是天文影响, 都会让一个星球走向冰冻或炙烤。 有一种迹象表明, 我们的月球起了作用, 这很有趣, 因为普遍流行的理论是, 月球形成的时候,一个火星大小的 天体忒伊亚 撞上了刚形成的地球。 那次撞击的结果可能产生了 一个截然不同的地月系统。 然而实际上,我们最终 得到的是一个大月球, 这使得地球既可以稳定地轴向倾斜, 也可以缓慢地旋转。 这两个因素都影响着气候, 它们有助于缓和气候变化。 对我们来说很棒,对吧? 但沃尔瑟姆指出, 如果月球的直径再大几英里, 情况就会不同了。 地球的自转轴将会混乱地漂移。 气候会快速变化—— 这对复杂生命的形成非常不利。 月亮的尺寸正合适: 不大不小,正好。 一颗“刚刚好的”月球环绕着 一颗“刚刚好的”行星—— 也许这也是障碍之一。
You can imagine more barriers. For instance, simple cells came into being billions of years ago ... but perhaps the development of complex life needed a series of unlikely events. Once life on Earth had access to multicellularity and sophisticated genetic structures, and sex, new opportunities opened up: animals became possible. But maybe it's the fate of many planets for life to settle at the level of simple cells.
你可以想象更多的障碍。 例如, 简单的细胞是数十亿年前形成的…… 但也许复杂生命的孕育和发展 需要一系列的不可能事件为前提。 一旦地球上的生命发展为多细胞生物、 复杂的遗传结构, 和性别, 新的机会就出现了: 动物就会诞生。 但是,可能许多行星的命运是 只有简单细胞级别的生命存在。
Purely for the purposes of illustration, let me suggest four more barriers to add to the four that people said blocked the path to communicative civilization. Again, purely for the purposes of illustration, suppose there's a one-in-a-thousand chance of making it across each of the barriers. Of course there might be different ways of navigating the barriers, and some chances will be better than one in a thousand. Equally, there might be more barriers and some chances might be one in a million. Let's just see what happens in this picture.
纯粹为了说明的目的, 让我再加四个障碍, 基于人们所说的阻碍了 文明交流渠道的四个障碍。 强调一下,纯粹为了解释清楚, 我假设跨越每一个障碍的 几率是千分之一。 当然,可能会有不同的方法 来克服这些障碍, 有些机会可能不止千分之一。 同样,也可能有另一些障碍, 它们的机会只有百万分之一。 那么,就按这假设来看看会发生什么。
If the galaxy contains a trillion planets, how many will host a civilization capable of contemplating like us projects such as Breakthrough Starshot? Habitability -- right sort of planet around the right sort of star -- the trillion becomes a billion. Stability -- a climate that stays benign for eons -- the billion becomes a million. Life must start -- the million becomes a thousand. Complex life forms must arise -- the thousand becomes one. Sophisticated tool use must develop -- that's one planet in a thousand galaxies. To understand the universe, they'll have to develop the techniques of science and mathematics -- that's one planet in a million galaxies. To reach the stars, they'll have to be social creatures, capable of discussing abstract concepts with each other using complex grammar -- one planet in a billion galaxies. And they have to avoid disaster -- not just self-inflicted but from the skies, too. That planet around Proxima Centauri, last year it got blasted by a flare. One planet in a trillion galaxies, just as in the visible universe.
如果银河系里有一万亿颗行星, 那么有多少个行星上存在 像我们这样的文明, 能计划出“突破摄星”项目的文明? 适居性—— 合适的行星围绕着合适的恒星—— 一万亿里面有十亿个。 稳定性—— 永远保持良性的气候—— 十亿里面有一百万个。 必须孕育生命—— 百万里面有一千个。 拥有复杂的生命形式—— 一千里面只有一个。 必须开发出精密的工具—— 上千个星系中只有一颗行星能做到。 为了了解宇宙, 必须发展科技和数学—— 百万个星系中只有一颗行星能做到。 要接触其他恒星, 必须有社会性的生物, 能够用复杂的语法 相互讨论抽象概念—— 十亿个星系中只有一颗行星能做到。 而且它们必须避开灾难—— 不只是人祸,还有天灾。 围绕比邻星的那颗行星, 去年被一个耀斑烤焦了。 所以,一万亿星系中 只有一颗行星能做到, 可见的宇宙就是如此。
I think we're alone. Those colleagues of mine who agree we're alone often see a barrier ahead -- bioterror, global warming, war. A universe that's silent because technology itself forms the barrier to the development of a truly advanced civilization. Depressing, right?
我想我们是孤单的。 我的同事们,那些同意 人类是孤单存在着的同事们, 常会看到摆在我们面前的障碍—— 生物恐怖主义、 全球变暖、战争。 宇宙是沉默的, 因为科学技术本身会形成障碍, 让真正先进的文明无法发展。 听起来令人沮丧,是吧?
I'm arguing the exact opposite. I grew up watching "Star Trek" and "Forbidden Planet," and I saw a UFO once, so this idea of cosmic loneliness I certainly find slightly wistful. But for me, the silence of the universe is shouting, "We're the creatures who got lucky." All barriers are behind us. We're the only species that's cleared them -- the only species capable of determining its own destiny. And if we learn to appreciate how special our planet is, how important it is to look after our home and to find others, how incredibly fortunate we all are simply to be aware of the universe, humanity might survive for a while. And all those amazing things we dreamed aliens might have done in the past, that could be our future.
而我的观点恰恰相反。 我是看《星际迷航》和《禁星》长大的, 并且我亲眼见过一次不明飞行物, 所以,这种宇宙独有的概念 肯定让我有些伤感。 但对我来说, 宇宙的沉默是在呼喊, “我们是幸运的生物。” 我们跨越了所有障碍。 我们是唯一扫清所有障碍的物种—— 唯一能够决定自己命运的物种。 如果我们意识到这个星球的特殊性, 意识到:照顾好我们的家园 和找到其他生命的重要性; 意识到:我们十分幸运地 了解了宇宙的存在, 那么人类可能会存活得更长。 所有那些不可思议的事情, 我们幻想外星人曾经做过的事, 也许就是我们的未来。
Thank you very much.
非常感谢。
(Applause)
(掌声)