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The end of the Space Age 太空时代的结束 HOW big is the Earth? Any encyclopedia will give you an answer: its equatorial diameter is12,756km, or, for those who prefer to think that way, 7,926 miles. Ah, but then there is theatmosphere. Should that count? Perhaps the planets true diameter is actually nearer13,000km, including all its air. But even that may no longer be an adequate measure. For theEarth now reaches farther still. The vacuum surrounding it buzzes with artificial satellites,forming a sort of technosphere beyond the atmosphere. Most of these satellites circle only afew hundred kilometres above the planets solid surface. Many, though, form a ring likeSaturns at a distance of 36,000km, the place at which an object takes 24 hours to orbit theEarth and thus hovers continuously over the same point of the planet. 地球有多大?任何一本百科全书都会给你答案：赤道直径是12,756公里，或者，用英里来表达7,926英里。嗯，但是大气层有多大呢?也能计算吗? 包括空气在内，地球的直径可能接近13,000公里。甚至连这个数据也不够充分。因为现在地球的变化太大。包围大气层的外部空间人造卫星来去匆匆，形成一个在大气层外面的所谓技术层。大部分卫星绕行高度离地球地表仅几百公里。然而，在距地球36,000公里的轨道上物体绕转地球一周的时间为24小时，这个物体飞行时持续面对的是地球上的不变的同一个点，这样许多地球同步卫星的运行会形成一个类似的土星环。 | 
