伽利略和灯

    300多年前，意大利有一个名叫伽利略的年轻人。和阿基米德一样，他也在一刻不停地思考问题。还喜欢探究事物的根源。他发明了温度计，还发明了简单的望远镜和显微镜。在科学上，他有许多重要的发明。

    18岁那年，快到掌灯的时候，他正在比萨大教堂。那个时代，灯只能靠油来点燃，并用一根木竿挂在天花板上。当灯夫碰到它们，或者风吹过教堂时，它们就会像钟摆似的来回摇摆。伽利略注意到了这个问题。于是他开始仔细地研究它。

    他注意到，长度相同的木竿上的灯来回摆动的时间相同。那些较短的木竿的灯比那些较长木竿的灯摇晃速度要快。伽利略观察来回摇摆的灯，非常入迷。数百万人曾看到过灯的摇摆，却没有一个人想到要找出重要、实用的发现与现象之间的关系。

    伽利略回到自己的房间，便开始了试验工作。他找出一些不同长度的绳子，挂在天花板上，并在每个绳子的末端挂了一个砝码。接着他晃动所有的绳子，让它们像教堂里的灯一样来回摇摆。每根绳子就就像竹竿一样成了钟摆。

    经过长期的观察，他发现：如果是一根长39■英寸的绳子，一分钟正好晃动60次。而绳子是前面绳子的四分之一长的话，晃动速度正好是前面速度的2倍；反之亦然。要使它的晃动快两倍，或是原来速度的三分之一，绳子的长度必须是39■的1/9。伽利略使用了各种方式进行试验，最后他终于发现，怎样把摆装在时钟上，也就是今天我们看到的时钟的样子。

    因此，世界的一个最普通却最实用的发明——钟摆，因为教堂摇摆的灯和伽利略勤于思考、敢于探索而诞生了。

    你也可以自己用绳子和任何的重物制作一个钟摆。假如愿意的话，你还能用它来做试验。也许你就会算出每两秒钟摆动一次的钟摆的摆长应该是多少。

    galileo and the lamps

    in italy about three hundred years ago there lived a young man  and al the reasons for things. he invented the thermometer and simple forms of the telescope and the microscope. he made many important discoveries in science.

    one evening hteen years old he hted. the lamps— by long rods from the ceiling. hter knocked against them, or the h the cathedral, they  back and forth like pendulums. galileo noticed this. then he began to study them more closely.

    he sa on rods of the same length s back and forth, or vibrated, in the same length of time. those that er rods. as galileo ing to and fro he became much interested. millions of people had seen lamps moving in this same ht of discovering any useful fact connected an to experiment. he took a number of cords of different lengths and hung them from the ceiling. to the free end of each cord he fastened a ht. then he set all to sing back and forth, like the lamps in the cathedral. each cord  study that , it vibrated just sixty times in a minute. a cord one fourth as long vibrated just tth. by experimenting in various ing lamps in the cathedral, and to galileo’s habit of thinking and inquiring, the ht of any kind. you can experiment  a pendulum must be to vibrate once in two seconds.</p>

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