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1、1.Can We Know the Universe? - Reflections on a Grain of Salt Carl Sagan Science is a way of thinking much more than it is a body of knowledge. Its goal is to find out how the world works, to seek what regularities there may be, to penetrate to the connections of things - from sub-nuclear particles,
2、which may be the constituents of all matter, to living organisms, the human social community, and thence to the cosmos as a whole. Our intuition is by no means an infallible guide. Our perceptions may be distorted by training and prejudice or merely because of the limitations of our sense organs, wh
3、ich, of course, perceive directly but a small fraction of the phenomena of the world. 与其说科学是一套知识体系倒不如说是一种思维方式。其目标是弄清世界如何运转，探求可能存在的规律，洞察事物之间的联系-从可能是构成万物的基本单位的亚核粒子到生命有机体及人类社会乃至整个宇宙之间的联系。我们的直觉是一点也不可靠的。由于教育和偏见，或者由于我们感觉器官的局限，我们的认知会出现偏差，我们的感觉器官只能直接感知世界上的一小部分现象。Even so straightforward a question as whether
4、 in the absence of friction a pound of lead falls faster than a grain of fluff was answered incorrectly by Aristotle and almost everyone else before the time of Galileo. Science is based on experiment, on a willingness to challenge old dogma, on an openness to see the universe as it really is. Accor
5、dingly, science sometimes requires courage-at the very least, the courage to question the conventional wisdom. 甚至像“在没有摩擦力的情况下，一磅铅是否要比一点绒毛下落得快”这样简单的问题，在伽利略之前的亚里士多德和几乎所有的人都回答错了。科学基于实验，基于勇于怀疑古训，基于渴求探索宇宙真理。因此，科学有时需要勇气，至少需要有敢于怀疑传统知识的勇气。But to what extent can we really know the universe around us? Sometim
6、es this question is posed by people who hope the answer will be in the negative, who are fearful of a universe in which everything might one day be known. And sometimes we hear pronouncements from scientists who confidently state that everything worth knowing will soon be known - or even is already
7、known. 我们对周围的世界能认识多少呢？有时那些提出这样问题的人希望得到否定的答案，他们害怕一个终将可能被完全认识的世界。有时这样的问题是一些科学家提出的，他们自信地宣称，一切值得我们认识的事物很快就会被认识，甚至已经被认识了。Let us approach a much more modest question: not whether we can know the universe or the Milky Way Galaxy or a star or a world. Can we know ultimately and in detail, a grain of salt? C
8、onsider one microgram of table salt, a speck just barely large enough for someone with keen eyesight to make out without a microscope. In that grain of salt there are about 1016 sodium and chlorine atoms. This is a 1 followed by 16 zeros, 10 million billion atoms. If we wish to know a grain of salt,
9、 we must know at least the three-dimensional positions of each of these atoms. (In fact, there is much more to be known - for example, the nature of the forces between the atoms - but we are making only a modest calculation.) Now, is this number more or less than the number of things which the brain
10、 can know? 让我们来考虑一个要小得多的问题：不是我们能否认识宇宙，或者银河系，或者一个星球，或者一个世界的问题，而是我们能否最终完全认识一粒盐的问题。设想一微克的食盐，只有一个视力好的人不借助显微镜刚好能看到的那么大一粒。在那一粒盐中，有约1016个钠和氯的原子，也就是1后面有16个0，即1亿亿个原子。如果我们想要认识一粒盐的话，至少我们得知道每一个原子的空间位置。（事实上，还有许多需要知道的-比如，原子之间力的性质等问题，不过我们现在尽量少考虑一些。)这个数字和人脑能够认知的事情相比是多还是少呢？How much can the brain know? There are perh
11、aps 1011 neurons in the brain, the circuit elements and switches that are responsible in their electrical and chemical activity for the functioning of our minds. A typical brain neuron has perhaps a thousand little wires, called dendrites, which connect it with its fellows. If, as seems likely, ever
12、y bit of information in the brain corresponds to one of these connections, the total number of things knowable by the brain is no more than 1014, one hundred trillion. But this number is only one percent of the number of atoms in our speck of salt. 人脑有多大认知能力呢？大脑中约有1011 个神经元，它们是在电和化学反应中控制我们大脑活动的电路元件和
13、开关。典型的神经元上面有约1000个须状物，叫做树突, 树突把这些神经元与其同类连接起来。如果大脑中的每条信息对应一个树突的话（情况很可能是这样的），大脑最多可以认知1014 个事物，也就是100万亿，不过这个数字仅仅是我们那一粒盐中原子数量的1%。So in this sense the universe is intractable, astonishingly immune to any human attempt at full knowledge. We cannot on this level understand a grain of salt, much less the un
14、iverse. 因此，在这个意义上，宇宙是难以认识的，人类想要获得完全的认知是不可能的，这个结论出乎我们的意料。在这个层面上，我们连一粒盐也认识不了，更不用说认识宇宙了。But let us look more deeply at our microgram of salt. Salt happens to be a crystal in which, except for defects in the structure of the crystal lattice, the position of every sodium and chlorine atom is predetermine
15、d. If we could shrink ourselves into this crystalline world, we could see rank upon rank of atoms in an ordered array, a regularly alternating structure - sodium, chlorine, sodium, chlorine, specifying the sheet of atoms we are standing on and all the sheets above us and below us. An absolutely pure
16、 crystal of salt could have the position of every atom specified by something like 10 bits of information. This would not strain the information-carrying capacity of the brain. 不过，让我们再深入研究一下我们这一微克的盐。盐正好是晶体，在晶体中，除非晶格结构有缺陷，每个氯原子和钾原子的位置是固定的。如果我们能缩小身体，走进这个晶体世界的话，我们就会看到一排排的原子有序排列，呈规则的交互结构-氯、钠、氯、钠，这样的结构规则统治着我们所站立的这排原子，以及我们上面和下面所有的原子。一粒纯晶体盐中原子的位置可以说是由10位信息的规则所规定的，这就不会让大脑的信息负荷能力感到吃力了。If the universe had natural laws that governed its behavior to the same degree of regularity that
