2017 考博英语 阅读题源经济学人文章每日精析（五十五）

考博英语阅读大部分博士研究生招生院校都使用《经济学人》杂志文章作为题源，考博信息网|http://www.kaoboinfo.com教育考博频道为考博生们将其中的文章进行深度分析，希望能提高大家的考博英语阅读水平，读懂长难句。

导读

日食月食在古代被认为是不吉祥的征兆，统治者就用这个来麻痹百姓。在今日，日食月食却是考古界推算统计过去时间的一个重要手段，种种迹象和演算表明，在远古时代，地球自转是23小时而不是24小时。

Ancient eclipses show how days are getting longer

古代日食表明日长正在变长

The value of ancient records

古文献的价值

Dec 10th 2016

2016年12月10日

AS THE well-known Australian philosopher, Kylie Minogue, once pointed out, it can be a source of comfort to remember that, no matter what else is happening, the world still turns. Unfortunately, things are not quite so simple. Thanks to the moon’s gravitational tug, the speed at which Earth spins has been slowing since the satellite’s birth about 4.5bn years ago. Physicists can calculate from first principles how big the effect should be. It turns out that the moon should be adding about 2.3 milliseconds to the length of the day with each century that passes. This means, for instance, that 100m years ago, when dinosaurs ruled Earth, a day was nearer 23 than 24 hours.

正如著名的澳大利亚哲学家Kylie Minogue曾说过，无论发生什么，世界都不会改变---经常被用作心灵鸡汤之言。不幸的是，世界似乎没有这位哲学家形容的这么简单：由于月球的引力作用，相比于45亿年前月球成为地球卫星时，地球的自转一直都在变慢。物理学家能够利用第一性原理计算出地球自转变慢的影响有多大。结果是每100年地球日长就增加2.3毫秒。这意味着一亿年前恐龙时代，地球自转一周大概只需要23小时而不是现在的24小时。

gravitational tug：引力作用

satellite：n. 卫星

dinosaur：n. 恐龙

注：第一性原理：根据原子核和电子互相作用的原理及其基本运动规律，运用量子力学原理，从具体要求出发，经过一些近似处理后直接求解薛定谔方程的算法，习惯上称为第一性原理。

But that 2.3 milliseconds is only an average. Geological events within Earth can speed the process up, or slow it down. Tracking changes in day length over time is thus of interest. And that requires data. Thanks to the development of super-accurate atomic clocks in the 1950s, and to laser range-finding equipment left on the moon by the Apollo astronauts, researchers have plenty of such data from the past half-century. But more information is always welcome. And extra data are exactly what a team led by Leslie Morrison, a retired professional astronomer, have just provided. In a study just published in the Proceedings of the Royal Society they use observations made by ancient Chinese, Babylonian, Greek and Arab astronomers to reconstruct the history of Earth’s rotation over the past two and a half millennia.

不过2.3微秒只是一个平均值。地球上每一次地质变化都能加快或减慢这个速度。追踪日的长短不仅需要兴趣，还需要数据。多亏了二十世纪五十年代的超高精度原子钟的发展，以及阿波罗宇航员在月球上安装的激光测距设备，研究人员得以掌握了近半个世纪以来的大量的数据。不过信息肯定是越多越好的。一位名为Leslie Morrison的退休的前专业天文学家及其领导的团队恰好证实了这一点并于近日在《英国皇家学会学报》发表了他们的研究成果。他们利用古代中国，巴比伦，希腊以及阿拉伯几个国家近两个半世纪的观测数据揭露了地球自转的历史。

Observation：n. 观察值

Plenty of ancient cultures were keen on astronomy, for the patterns of the heavens were the basis of their calendars and timekeeping systems (not to mention their systems of astrology). But Dr Morrison and his colleagues were interested in two particular phenomena: eclipses of the sun and of the moon. A solar eclipse happens when the moon moves in front of the sun, as seen from a particular spot on Earth, and blocks out its light. A lunar eclipse happens when the moon moves behind Earth in such a way that Earth blocks the sunlight that, when reflected from the lunar surface, renders the moon visible.

大部分古代的文化都跟天文学息息相关，因为历朝历代的历法和计时系统(更不用说古代还有天体系统)都是基于天体的轨迹得出的。不过Morrison博士和他的同事们兴趣点主要集中于两种天体现象：日食和月食。从地球上某个特定位置点观察，当月球运行到太阳与地球之间时，月球遮住了太阳的光芒，日食便会发生。同样的，当地球运行到日月之间时，地球遮挡住了太阳照射到月球上使月球可见的光芒，月食便会发生。