大学英语自学教程(上册) unit 18
18-A. Why Are Maps Drawn with North at the Top?
Now it is hard to visualize a map that does not feature north at the top, but this was not always so.
The oldest known map in the accepted sense of the word was drawn about 3, 800 BC, and represents the river Euphrates flowing through northern Mesopotamia, Iraq. This, and others that followed it, were little more than rough sketches of localized features; it was not until many centuries later that the ancient Greeks placed the science of map-making on a sound footing.
At the forefront of the pioneers in the field was the Greek mathematician and philosopher Claudius Ptolemaeus (c. AD 90 ?168), more popularly known to history as Ptolemy. The last great scientist of the classical period, he was the first to draw a map that was based on all available knowledge, rather than guess or imagination. Earlier, the Bahylonians had attempted to map the world, but they presented it in the form of a flattened disc rather than a sphere, which was the form adopted by Ptolemy.
Given the state of knowledge of those times, he got things wrong; for example, his estimate of China and the Atlantic Ocean was far from being accurate. Nevertheless, it was a useful effort, and the map remained a work of reference for over a thousand years. In fact, Christopher Columbus used a version of it when he set sail in search of the New World - which caused him some navigational problems, since Ptolemy had calculated wrongly the size of the Atlantic and was unaware that the Pacific Ocean existed.
The really important thing about Ptolemy's map was that north was at the top. The reason for this was that he decided to orientate the map in the direction of the Vole Star since Polaris was the immovable guiding light in which the voyagers of that era placed their trust.
North at the top remained the accepted arrangement until the early Middle Ages, when the Church began to interfere seriously with the advance of science. In accordance with the orders of the Church, maps were still produced in accordance with Ptolemy's principles ?but now Jerusalem was the central feature, as it was held to be the center of the Christian faith, and east was moved to the top.
These maps are often called "T" Maps because they show only three continents - Europe, Asia and Africa - separated by the "T" formed by the Mediterranean Sea and the River Nile. From a navigational point of view, they were almost useless.
More accurate maps began to appear in the 14th century, with the spread of trade and increasing reliance on the compass. Once again, north assumed its rightful place at the top of maps.
【课文译文】
为什么地图以北为上
今天，人们难以想像地图的上方指的不是北方。但过去并不总是这样的。
现在已知的最古老的被人们认可的地图是于大约公元前3800年绘制的。地图描绘的是流经伊拉克美索不达米亚北部的幼发拉底河。这幅地图以及随后出现的一些地图无非都是些局部地貌的草图。直到许多世纪以后，古希腊人才把地图绘制学置于坚实的基础上。
这一领域的先驱中最早的是希腊数学家和哲学家克劳迪?托勒密(约公元90年～168年)，历史上多称他托勒密。作为古典文化艺术时期的最后一位伟大的科学家，他是把地图绘制建立在当时所有可获得的知识上，而不是建立在猜想或想像之上的第一人。在这之前，巴比伦人曾试图绘制世界地图，但他们把它绘成平盘状而不是托勒密采用的球体状。
鉴于当时人们的知识水平，他把一些事情搞错了。例如，他对中国及大西洋的估计远不够精确。尽管如此，这仍是一次有用的尝试，这幅地图一千年以来一直作为一种参考。其实，克里斯长弗?哥伦布当时寻找新大陆时就使用该版本——这使他在航海中出了些问题，因为托勒密错误地计算了大西洋的面积，而且不知道太平洋的存在。
关于托勒密的.地图最重要的一点是北方为上方。其原因是他决定以北极星的方向来确定地图的方向，因为北极星是固定不动的航灯，那时的航海者依赖它进行航行。
在中世纪早期以前，人们一直接受北在上方的布局。此后，教会严重地妨碍了科学的发展。根据教会的命令，地图仍然按托勒密的原则进行绘制——但当时是以耶路撒冷为中心，因为它被认为是基督徒信仰的中心，所以东方成了地图的上方。
这些地图常被称为“T”形地图，因为它们只显示了三个大洲——欧洲、亚洲和非洲——由地中海和尼罗河形成的“T”字形将它们分开，从航海的观点看，这些地图几乎没什么用处。
14世纪，随着贸易的发展以及人们对指南针的日益依赖，出现了更精确的地图。北方又一次恢复了它在地图上方的正当位置。
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