自然科学通俗读本

简介

《自然科学通俗读本》出版于1869年，美国纽约，它是深刻影响爱因斯坦少年时代的几本书之一。爱因斯坦在“自述”中回忆：“我还幸运地从一部卓越的通俗读物中知道了整个自然科学领域里的主要成果和方法，这部著作（伯恩斯坦的《自然科学通俗读本》是一部有五、六卷的著作）几乎完全局限于定性的叙述，这是一部我聚精会神地阅读了的著作”。虽然过去了140年，这本书仍具有传播价值。

第一部分：地球的重量

第一章  整个地球重多少磅

自然哲学家思考和研究的，往往是从不懂科学的人脑袋里冒出来的、超越了人类智力的问题。这些问题中也许包括这一个：“整个地球重多少磅？”

确实，有人以为这个问题容易回答。可以认为是任何一个重量，毫无疑问没有人能找来一个秤，检查一下是否差了一盎司。这个问题绝不是玩笑，回答也绝不是猜测，相反，问题和答案都是真实的科学结果。这个问题本身是非常重要的，我们能够给出的回答也是正确的。

人们认为，知道了我们这个星球的尺寸，确定它的重量就没有困难。要做到这一点，仅仅需要制作一个可以精确称出重量的小土球；然后我们可以很容易计算出地球比小土球大多少倍；如此做来，我们就可以掰着手指头说出，如果假定小土球重一百磅，那么地球大它多少倍，则必然重它多少倍。

可是，这样的做法极可能误导我们。因为一切取决于制造小球的物质。如果用酥松的泥土制造小球，它的重量就小；如果泥土中掺杂石头，它的重量就大一些；如果掺杂金属，取决于掺杂金属的种类，它的重量将更大。

于是，我们想根据那个小球的重量判定我们星球的重量，首先要知道我们的星球由什么物质构成；它是否包含石头、金属、或完全未知的物质；是否有空洞，或整个星球是否只是一个空心球，我们居住在它的表面，球内可能是另一个世界，要钻穿它的厚壳才能到达。

稍加思考，即可看清楚“地球有多重”这个问题，实际上将引导我们研究地球的物质；这是一个科学性的问题。

这个问题不久前被解决了。得到的结论是地球重60,690,942,120亿吨；作为一个整体，地球由一种比铁轻的物质构成；靠近地球表面的物质要轻一些；靠近核心的物质密度增大；最后，虽然靠近表面有很多空洞，但是地球自身并不是一个空心的球。

我们现在将尝试尽可能明白简洁地阐释，人们借以科学地研究这个问题的方式方法。

POPULAR TREATISE ON NATURAL SCIENCE

PAET I.

THE WEIGHT OF THE EARTH.



OHAPTEE I.

HOW MANY POUNDS THE WHOLE EARTH WEIGHS.

Natural philosophers have considered and investigated subjects that often appear to the unscientific man beyond the reach of human intelligence. Among these subjects may be reckoned the question, " How many pounds does the whole earth weigh?"

One would, indeed, believe that this is easy to answer. A person might assign almost any weight, and be perfectly certain that nobody would run after a scale, in order to examine, whether or not an ounce were wanting. Yet this question is by no means a joke, and the answer to it is by no means a guess; on the contrary, both are real scientific results. The question in itself is as important a one, as the answer, which we are able to give, is a correct one.

Knowing the size of our globe, one would think that there was no difficulty in determining its .weight. To do
this, it would be necessary only to make a little ball of earth that can be accurately weighed ; then we could easily calculate how many times the earth is larger than this little ball; and by so doing, we might tell, at one's fingerends, that — if we suppose the little earth-ball to weigh a hundred-weight — the whole globe, being so many times larger, must weigh so many hundred- weights.

Such a proceeding, however, would be very likely to mislead us. For all depends on the substance the little ball is made of. If made of loose earth, it will weigh little; if stones are taken with it, it will weigh more; while, if metals were put in, it would, according to the kind of metal you take, weigh still more.

If, then, we wish to determine the weight of our globe by the weight of that little ball, it is first necessary to know of what our globe consists; whether it contains stones, metals, or things entirely unknown ; whether empty cavities, or whether, indeed, the whole earth is nothing but a hollow sphere, on the surface of which we live, and in whose inside there is possibly another world that might be reached by boring through the thick shell.

With the exercise of a little thought, it will readily be seen that the question, " How much does our earth weigh?" in reality directs us to the investigation of the character of the earth's contents; this, however, is a question of a scientific nature.

The problem was solved not very long ago. The result obtained was, that the earth weighs 6,069,094,212 billions of tons; that, as a general thing, it consists of a mass a little less heavy than iron ; that towards the surface it contains lighter materials ; that towards the centre they increase in density ; and that, finally, the earth, though containing many cavities near the surface, is itself not a hollow globe.

The way and manner in which they were able to investigate this scientifically, we will attempt now to set forth as plainly and briefly as it can possibly be done.