The Arecibo Message, Described

On 16 November 1974, at a ceremony marking the upgrading of the great radio dish at Arecibo, in Puerto Rico, the telescope was turned for a few minutes from listening to speaking. It sent one message, once, toward the globular cluster Messier 13, a ball of several hundred thousand stars about 25,000 light-years away. The transmission lasted less than three minutes. It was sent at 2,380 megahertz, with a power of about 450 kilowatts, by shifting the frequency of the beam up and down by 10 hertz: one tone for a one, another for a zero, ten bits each second.

1974 年 11 月 16 日，在波多黎各阿雷西博，那面巨大的射电天线完成改造，人们为此举行了一个仪式。仪式上，这台望远镜有几分钟从“倾听”转为“说话”。它朝着球状星团 M13 发出了一条信息，只发了一次。M13 由几十万颗恒星聚成一个球形的星团，距离我们大约两万五千光年。整个发送不到三分钟。信号频率为 2380 兆赫，功率约 450 千瓦，靠让波束的频率上下移动 10 赫兹来编码：一个音调代表 1，另一个代表 0，每秒十位。

There were 1,679 bits in all. The number was chosen with care. It can be made by multiplying only two prime numbers, 23 and 73, so a patient receiver who wonders how to lay the bits out in a rectangle has very few choices. Arranged as 73 rows of 23, the ones and zeros become a picture. Arranged the other way, they become noise.

信息一共 1679 位。这个数字是精心挑选的：它只能由两个质数 23 和 73 相乘得到。因此，一个耐心的接收者如果想知道该把这些位排成怎样的长方形，可选的余地非常少。排成 73 行、每行 23 位，这些 1 和 0 就成了一幅图；换一种排法，就只是一片杂音。

The picture is read from the top down. First come the numbers one to ten, written in binary, so that the receiver learns how this message counts. Then five numbers: 1, 6, 7, 8 and 15, the atomic numbers of hydrogen, carbon, nitrogen, oxygen and phosphorus, the elements of DNA. Below them are the formulas for the sugar, the phosphate and the four bases from which DNA is built, and below those a twisting double strand with a long number running down its middle: the count of base pairs in a human genome, as it was estimated in 1974.

这幅图从上往下读。最先是用二进制写出的 1 到 10，好让接收者明白这条信息怎样计数。接着是五个数：1、6、7、8、15，分别是氢、碳、氮、氧、磷的原子序数，也就是构成 DNA 的元素。它们下面是组成 DNA 的糖、磷酸和四种碱基的化学式；再下面是一条盘旋的双链，中间竖着一个很长的数——人类基因组中碱基对的数目，按的是 1974 年的估计。

Then a figure of a human being. Beside it, a height, given as fourteen times the wavelength of the message itself, about 1.76 metres; on the other side, the number of people then living on Earth, a little over four billion. Under the figure is a row of shapes for the Sun and the nine planets counted in 1974, with the third planet lifted slightly toward the person standing above it. At the bottom is a drawing of the telescope that sent the message, with its width written underneath, again in wavelengths: about 306 metres.

然后是一个人的图形。它的一侧标着身高，用信息本身波长的十四倍来表示，约 1.76 米；另一侧是当时生活在地球上的人口数，四十多亿。人形下面是一排代表太阳和 1974 年时算作九大行星的图形，其中第三颗行星微微抬起，朝向站在它上方的那个人。最下面是发出这条信息的望远镜的图形，下方写着它的宽度，同样以波长为单位：约 306 米。

The message was designed by Frank Drake and colleagues at Cornell University and the Arecibo Observatory, with help from Carl Sagan and others. It was meant less as a real attempt to begin a conversation than as a demonstration of what a radio telescope could do. Travelling at the speed of light, it will reach the region of Messier 13 in roughly twenty-five thousand years. The cluster will have moved a little in its orbit around the galaxy by then, but not far.

这条信息由弗兰克·德雷克和康奈尔大学、阿雷西博天文台的同事们设计，卡尔·萨根等人也参与其中。它与其说是真想开启一场对话，不如说是在展示一台射电望远镜能做到什么。它以光速前进，大约两万五千年后到达 M13 所在的区域。到那时，这个星团会沿着它绕银河系的轨道移动一点，但不会走远。

The telescope itself no longer stands. Its platform fell into the dish on 1 December 2020. The message it sent is still travelling, and will be for a very long time.

那台望远镜本身已经不在了。2020 年 12 月 1 日，它的接收平台坠入了天线之中。而它发出的信息仍在路上，还将走很久很久。