【英teresting】都在过520？单身狗还是探索方程式吧！

普天同庆的520，小编献出自己为你们讲述一个方程式...

（弗兰克·唐纳德·德瑞克和他的贡献He is most notable as one of the pioneers in the search for extraterrestrial intelligence（地外智慧）, including the founding of SETI（搜寻地外文明计划）, mounting the first observational attempts at detecting extraterrestrial communications in 1960 in Project Ozma, developing theDrake Equation, and as the creator of the Arecibo Message（阿雷西博信息）, a digital encoding of an astronomical and biological description of the Earth and its lifeforms for transmission into the cosmos.

The search for extraterrestrial intelligence (SETI) is a collective（集合的） term for the scientific search for intelligent extraterrestrial life. For example, monitoring electromagnetic radiation（电磁辐射） for signs of transmissions from civilizations on other worlds.

More recently, Stephen Hawking, British physicist, andYuri Milner, Russian billionaire announced a well-funded effort, called the Breakthrough Initiatives（突破计划）, to expand efforts to search for extraterrestrial life.

搜寻地外文明计划（SETI），是对所有在搜寻地外文明的团体的统称，不是只代表一个组织。

这其中较著名的有学术单位包括哈佛大学和柏克莱加州大学，非营利组织SETI协会。这些组织致力于用射电望远镜等先进设备接收从宇宙中传来的电磁波，从中分析有规律的信号，希望借此发现外星文明。

其中，SETI@home是一项旨在利用连入因特网的成千上万台计算机的闲置计算能力搜寻地外文明的工程。参加者可以用下载并运行屏幕保护程序的方式来让自己的计算机检测射电讯号。

德瑞克方程（Drake equation）又称萨根公式（Sagan equation）或格林班克公式（Green Bank equation），是由天文学家法兰克·德雷克（Frank Drake）于1960年代提出的一条用来推测“可能与我们接触的银河系内外星球高智文明的数量”之公式。

各家对此公式中的各项变数的估计值各有不同，不同的估计值可得出不同的N来。因此有些人据此认为银河系中有非常多的文明可与地球通讯。

The estimated values of the variables in each of the formulas are different, and different estimates can be derived from different N.

A possible version and its explanation

·在这里，巨大的星云气体坍塌形成恒星。一个比较好的关于恒星形成速度 的数值是每年20 颗恒星，所以R=20。

Here, a huge cloud of gas collapses to form stars. A relatively good numerical value of the star formation rate is 20 per year, so R=20.

我们可以估计一下，有二分之一的恒星是由行星的，而另一半的恒星是双子星系统， 所以f(p)=0.5。

We can estimate that there are 1/2 stars from the planet, while the other half of the stars is Gemini system, so f(p)=0.5.

·n(e)这个参数有点儿麻烦。在我们的太阳系里，以中等大小，黄色的太阳为中心的生态圈里面，有两颗（地球和火星）或者三颗 （金星）行星。那么处于“生命区”或者说生态圈（ecosphere）里的行星数量的保守估计是1，所以n(e)=1。

n(e) is a bit of a problem. In our solar system, with a medium sized, yellow sun, two (earth and Mars) or three planets in the center of the ecosystem. So a conservative estimate of the number of planets in the "living area" is 1.

下一个参数，f(l)的定义是比较困难的。问题在于，我们只有很少的有关行星可以适合于生命进 化的例子。如上面提到的，金星，地球和火星都应该具有合适的环境和条件。我们知道，在地 球上发生了生命的进化，而且似乎现在也有证据表明数十亿年前火星上就存在着简单的生命形 式。这个参数的保守估计是0.2，或者说五分之一的行星上具有可以让生命进化的合适的条件。 所以，f(l)=0.2。

The next parameter, f (l) is defined as the more difficult. The problem is that we have only a few examples of how the planets can be fit for life. As mentioned above, Venus, Earth and Mars should have the right environment and conditions. We know that life has evolved on earth, and it seems that there is now evidence that a simple life - shaped form of life on Mars, billions of years ago. A conservative estimate of this parameter is 0.2,or 1/5 of the right conditions for life to evolve. So,f(l)=0.2.

· 究竟有多少这样的星球能够孕育智慧生命？这是一个很难回答的问题。但是如果我们真的相信 自然选择和适者生存的话，几乎所有的科学家都会认为这个数字应该是百分之百。也就是说， 智慧生命是自然进化的结果。当然，我们只有一个这样的例子，那就是地球。所以，f(i)=1。

How many of these planets will be able to breed the wisdom of life? This is a very difficult question to answer. But if we really believe that natural selection and survival of the fittest, almost all scientists believe that this number should be one hundred percent. That is to say, the wisdom of life is the result of natural evolution. Of course, we have only one such example, that is the earth. So, f (i) =1.

·有多少智慧生命将会发展科技并用来与外界沟通？如果我们观察一下地球，我们会发现人类正 在做这样的事情；但是我们也同时可以看到鲸鱼和海豚，它们也拥有一定的智力，但是它们却 从来没有发展它们的科技。我们可以初步估计这个数字为0.5，即f(c)=0.5。

How much of the wisdom of life will develop technology and to communicate with the outside world? If we observe the earth, we will find that man is doing the same thing; but we can also see the whales and dolphins, they also have a certain intelligence, but they have never developed their technology. We can estimate the number of 0.5, that is, f(c)=0.5.

·最后，我们要看看最难决定的参数了。“L”代表的是一个具有高度发达科技和可以沟通交流 的文明所持续的年数。人类也不过仅仅处于进化的这一阶段中大约50年。 现在我们先不用数字来代替“L”，让我们先代入其他数字，看看我们可以得到什么。

Finally, we need to look at the most difficult parameters. "L" represents a highly developed technology and a number of years that can communicate with each civilization. Human beings are only in the evolution of this stage for about 50 years. Now we don't figure instead of "L", let us first look into other numbers, we can get what.

N=20*0.5*1*0.2*1*0.5*L=L

将所有的数字都代入等式，我们就得到了N=L!!

换句话说，在银河系里，智慧的可以沟通的文明的数量就等于这样的文明存在的年数。我们所用的计算方式至少给我们了一些很有意义的启示。很多科学家认为，如果一个文明能够在开始就克服科技发展而带来的毁灭自己的趋势，那么这个文明可能会持续非常长的时间。我们希望那些科学家是正确的。在任何情况下，文明至少应该持续50年（这也正是我们所开始经历的50年），而且如果文明可以存在上百万年的话，那么我们有可能能够寻找到上百万个文明。

In other words, the number of civilizations in the galaxy, the wisdom of the civilization, is equal to the number of years. At least some of the methods we use are very meaningful. Many scientists believe that if a civilization can overcome the destruction of its own development at the beginning, it could last a very long time. We hope that the scientists are right. In any case, civilization should last for at least 50 years (this is what we are going through for 50 years), and if there are millions of years of civilization, we are likely to be able to find a million civilizations.

Is all of these that simple ?

Though the accuracy of the equation remains controversial ,the method of it provides new insights into the discovery of life.

在银河系里，智慧的可以沟通的文明的数量就等于这样的文明存在的年数。我们所用的计算方式至少给我们了一些很有意义的启示。

(an excellent documentary)责任编辑：徐治仁

指导老师：孙由之

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