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When we think of looking for extra-terrestrial life, we tend to focus on “earth-like” planets, that is, planets with conditions that are similar to our own.
当我们考虑寻找外星生命时，我们倾向于关注“类地”行星，即条件与我们相似的行星。
“Life exists on earth,” the logic goes, “so earth-like conditions are probably a good bet to find more life.”
“地球上存在生命，”由此推出，“所以类地环境可能是发现更多生命的好机会。”
And yet.
但是。
There are hundreds of billions of galaxies in the observable universe, each with billions if not trillions of stars, and most stars have planets orbiting them.
在可观测的宇宙中有数千亿个星系，每个星系都有数十亿甚至数万亿颗恒星，而大多数恒星都有围绕它们运行的行星。
That’s roughly a million billion billion planets.
这大概有十万亿亿亿颗行星。
The enormity of this number means it’s probably safe to assume that there are many many many other planets with life - even intelligent life.
这个庞大的数字意味着，我们可以有把握地假设有许许多多其他星球上有生命——甚至是有智慧的生命。
And this, together with some basic physics and fancy statistics,
这一点，再加上一些基本的物理原理和复杂的数据统计，
implies it’s more likely that species of intelligent extraterrestrials will live on habitable planets unlike earth and will be unlike humans.
意味着更有可能的是，智慧的外星生物将生活在与地球并不相像的宜居星球上，而它们长得也不像人类。
More precisely, they’ll be bigger than us and live in smaller groups on smaller planets.
更准确地说，它们将比我们更大，并且在更小的行星上以更小的群体生活。
Now, I know it sounds crazy that with only one data point – us – we can make any predictions at all about aliens we don’t even know exist.
现在，我知道这听起来很疯狂，仅凭一个数据点——我们——我们就可以做出任何关于外星人的预测，我们甚至不知道它们是否存在。
But we can – here’s how: A basic result in statistics is that there’s a big difference between the properties of a typical individual and the properties of an individual in a typical group.
但我们可以，我们是这样做的:统计学的一个基本结果是，一个典型个体的属性和一个典型群体中的个体属性之间存在很大差异。
The majority of humans, for example, live in countries with a population of at least 180 million people.
例如，大多数人生活在人口至少为1.8亿的国家。
But the majority of countries have populations of less than 6 million.
但大多数国家的人口不足600万。
And the majority of religious humans are members of religions with more than a billion followers, while the majority of religions have fewer than a million followers.
大多数有宗教信仰的人信仰的都是拥有超过10亿信徒的宗教，而大多数宗教的信徒不到100万。
And the majority of people who follow the English Premier league are fans of teams with hundreds of millions of fans like Manchester United, while most teams have just a few million fans each.
大多数英超球迷都是像曼联这样拥有数亿球迷的球队的球迷，而大多数球队只有几百万球迷。
It doesn’t matter how many individuals you have, or how you make the groups – they can be religions, or fans of sports teams, or the ingredients of this trail mix.
不管有多少个人，不管这个团体是如何组成的——它们可以是宗教信徒，可以是球队的球迷，可以是这个什锦果干的成分。
It is a mathematical fact that the group that the median individual belongs to will be at least as big as the median group.
这是一个数学事实，中位数个体所属的群体至少和中位数群体一样大。
Or, simply put, any time groups are not all the same size, most individuals will be members of groups that are bigger than most of the other groups.
或者，简单来说，当群体的规模不完全相同时，大多数个体将属于比大多数群体更大的群体。
The takeaway is that an individual should expect to be a member of a large group, not an ordinary one.
由此得出的结论是，个人大概率是一个大群体的一员，而不是一个普通群体的一员。
If you don’t know what group you fall into (like, I don’t know what my blood type is), the most likely groups to be in are the biggest ones – I’m probably O or A positive.
如果你不知道自己属于那个群体(比如，我不知道我的血型是什么)，最有可能的血型是人数最多的那种——我很可能是O型血或A型血阳性。
And when it comes to intelligent life forms, we humans don’t know what kind of group we fall into.
说到智慧生命形式，我们人类不知道自己属于哪一类。
So statistics tells us that we, as individuals, should expect to be members of a large group of intelligent beings.
所以统计学告诉我们，作为个体，我们大概率是一个大的智能生物群体中的成员。
That is, we should expect that our species has a higher population than most other species.
也就是说，大概率上我们的物种比大多数其他物种拥有更多的种群。
And just knowing that we probably have a high population tells us a lot.
仅仅我们可能拥有很多的人口这一点就告诉了我们很多。
For example, individual living beings require space to live – I mean, the countries with the biggest populations tend to have large land areas –
例如，个体生物需要生存的空间，我的意思是，人口最多的国家往往有大片的土地，
so earth, with its high population, is probably bigger than most other planets with intelligent life.
因此，地球人口众多，可能比其他大多数有智慧生命的行星都要大。
Similarly, smaller living creatures need less space and energy per creature, and accordingly tend to have higher population densities:
同样地，小一点的生物需要更少的空间和能量，相应地就会有更高的人口密度：
that’s why there are way more ants on earth than elephants.
这就是为什么地球上的蚂蚁比大象多得多。
So humans, with our high population, are probably physically smaller than most other species of intelligent life.
所以，人口众多的人类，在生理上可能比大多数其他智慧生命物种要小。
In fact, we should expect to be abnormal among intelligent aliens when it comes to anything that influences overall population size.
事实上，当涉及到影响总体人口规模的任何因素时，我们都应该预料到在智能外星人中会出现异常。
Like, easily available energy makes it easier to maintain higher populations,
比如，容易获得的能量使得维持较高的人口数量更容易，
so we should expect our sun to be somewhat hotter and brighter and closer than the stars of most intelligent alien species;
所以我们应该推测我们的太阳比大多数智能外星物种的恒星更热、更亮、更近;
and we should expect our atmosphere to be more transparent to our star’s light; and so on.
我们应该推测我们的大气层对我们的恒星的光透光性更好;等等。
If this all sounds a bit unspecific, well, with just a few more simple and reasonable assumptions based on basic physics, we can be more precise.
如果这听起来有点不具体，那么，通过基于基础物理的一些更简单和合理的假设，我们可以更加精确。
Researchers have predicted that the population of most intelligent alien species should be below 20 million individuals;
研究人员预测，大多数外星物种的数量应该低于2000万;
the majority of planets with intelligent life should have less than 80% the radius of the earth;
大多数有智慧生命的行星的半径应该小于地球半径的80%;
and the individuals of most intelligent alien species should be at least as massive as polar bears.
大多数外星物种的个体至少应该和北极熊一样大。
So instead of looking for nearby intelligent extraterrestrials on “earth-like planets”,
因此，与其在“类地行星”上寻找附近的智慧外星生物，
the intelligent approach might be to look for habitable planets slightly smaller, darker, and hazier than our own.
明智的方法可能是寻找比我们的星球更小、更暗、更模糊的宜居行星。
In short, we should expect to be the Manchester United of the universe, searching for AFC Wimbledon.
简而言之，我们应该作为宇宙中的曼联，寻找温布尔登。
