大学英语自学教程 上册 un18

[07:51.28]除非为了方便，否则没有什么理由选一舍一。
[07:54.91]The relative speed between the trains remains the same, 10 mph;
[07:58.15]两列火车的相对速度每小时10英里保持不变；
[08:01.38]and the end result will be the same.
[08:03.51]并且最终结果也将是一样的。
[08:05.64]Now let's suppose that both trains are at the railroad station
[08:08.42]现在我们假设两列火车都停在车站，
[08:11.21]loading and unloading passengers and baggage.
[08:13.54]下旅客和装卸行李。
[08:15.88]A half-hour passes.
[08:17.71]半小时过去了。
[08:19.54]As we look at the other train through our window,
[08:21.67]当我们从车窗看另一列火车时，
[08:23.80]we see that our train seems to start moving, smoothly and slowly.
[08:27.02]我们看到自己的车好像开始平稳而缓慢地移动。
[08:30.25]For a minute or so, our train seems to travel at a uniform speed.
[08:33.63]一分钟左右以后，我们的火车似乎在匀速行驶。
[08:37.02]Our special speedometer
[08:38.99]我们的特殊的速度表
[08:40.96]shows that the relative speed between the two trains is 20 mph.
[08:44.38]显示两列车的相对速度是20英里每小时。
[08:47.80]But as we look out our window,
[08:49.83]但是当我们又往窗外看时，
[08:51.85]we suddenly see the last coach of the other train
[08:54.49]突然发现另一列火车的末节车厢从视野里消失，
[08:57.13]disappear from sight and notice the motionless station behind it.
[09:00.07]并且看到车站被除数留在后面一动不动。
[09:03.01]So we are not moving after all.
[09:05.03]所以我们根本没有移动。
[09:07.06]The other train has been moving!
[09:08.83]是另一列车在移动！
[09:10.61]This peculiar and often frustrating experienceis an effect of relative motion.
[09:13.99]这种奇怪又常令人尴尬的经历是相对运动的结果。
[09:17.37]At the train station we cannot tell whether it was our train
[09:20.65]在车站上我们分不清是我们的车
[09:23.93]that changed its speed from 0 mph to 20 mph or whether it was the other train
[09:28.16]还是另一列车从0英里每小时
[09:32.40]that changed its speed from 0 mph to 20 mph.
[09:35.48]变速为20英里每小时。
[09:38.56]Only after the other train pulled out of the'station could we see that it
[09:41.59]只是在另一列火车驶出车站以后，
[09:44.62]and not our train, was moving.
[09:46.75]我们才发现并非我们的车在动。
[09:48.88]Now let us again raise the question
[09:50.81]现在让我们再一次提出本文开头所提出的问题：
[09:52.74]that was raised at the beginning of this article
[09:54.82]在上述事例中我们
[09:56.90]can we be absolutely certain that the other train did indeed in crease its speed,
[10:00.23]能够绝对肯定是另一列车确实担速
[10:03.56]and in this case pull out of the station?
[10:05.53]并驶出车站了吗？
[10:07.50]If your answer is yes, then you are wrong again.
[10:09.99]如果你回答“是”，你又错了。
[10:12.47]All we can be certain of
[10:14.70]所有我们能肯定的
[10:16.93]is that the relative speed between the two trains changed.
[10:19.45]只是两列车的相对速度改变了。
[10:21.98]These examples illustrate an important principlein the spedal theory of relativity.
[10:25.21]这些例子说明了狭义相对论的一项重要原则。
[10:28.45]If A appears to be moving at a steady speed relative to B,
[10:31.24]如果A看上去以相对于B稳定的速度运动，
[10:34.02]we cannot know for sure if it is A that is really moving.
[10:36.96]我们并不能确定是否A真的在动。
[10:39.90]Perhaps A is standing still, and B is moving.
[10:42.77]也许A静止不动，而B在动。
[10:45.64]Or perhaps both are moving.
[10:47.47]或者也许两者都在动。
[10:49.30]According to relativity,
[10:51.04]根据相对论，
[10:52.77]there is no experiment that can be devised to solve the prolem.
[10:55.60]设计不出任何一方一个实验来解决这个问题，
[10:58.42]As there is no way of deciding which of the two objects is moving,
[11:01.20]因为无法来判定两个物体中的哪个在动，
[11:03.98]we can choose either one as the moving object.
[11:06.41]我们可以选择任何一个当作运动的物体。
[11:08.84]The reason is that their motion is relative, and relativity,
[11:11.92]其原因是在于它们运动是相对的；
[11:15.00]as we have seen, means that we have a choice.
[11:17.63]而相对性，正如我们所看到的那样，意味着我们面临选择。
[11:20.25]This principle--that if two objects are in uniform motionrelative to each other,
[11:23.79]如果两个物体彼此相对匀速运行，
[11:27.33]it is impossible to decide which one's moving and which one is at rest
[11:30.31]是不可能判定哪个在动，哪个是静止的，
[11:33.29]applies to all objects moving uniformlyin a straight line through the universe.
[11:36.76]这个原则通过适合于所有在宇宙中直线匀速运行的物体。
[11:40.24]In relativity you'll find that whenever you have a choice among
[11:43.52]在相对论里，你会发现每当你在两种具有相同
[11:46.80]things that are equally possible,
[11:48.78]可能性的事物中做出选择的时候，
[11:50.77]you are dealing with relative things.
[11:52.95]你都在与相对的事物打交道。
[11:55.13]For example, time, which is measured with clocks and watches,
[11:58.85]例如，用钟和表来测量的时间是相对的，
[12:02.57]is relative because it can be shown that there is more than one system of time.
[12:05.66]因为可以看出有不只一种时间系统。
[12:08.74]All systems of time are equally possible and you can choose any system you wish.
[12:12.37]所有时间系统都具有同样的可能性，进而你可以任选其一。