He eats both plants and meat. A strict plant-eater spends too much time stuffing himself with food to build the kind of civilization which is necessary to produce a spaceship. Animals which can digest meat only would not be likely to survive the occasional adverse periods which very likely occur on all planets and wipe out the less adaptable forms of life.

　　Hes probably not much larger than the largest human being. The limiting factor here is something called the spare-cube law. If you double the height of a, person without changing his proportions, you have a being with weight times the weight. This means that a person 12 feet tall, for example, must be clumsy and cannot perform precision work. And precision work will be essential, of course, in building the spaceship.

　　He weighs at least 40 pounds, and probably more. A brain of a certain size and complexity would be required for the building of a spaceship. The brain of our spacemen would weigh at least 2 pounds.

【四级冲刺练习阅读61】相关文章：

★ 六级经典的阅读3

★ 英语四级考试仔细阅读每日一练(12.24)

★ 2011年6月英语六级考试冲刺的练习阅读篇62

★ 英语六级考试标准的阅读27

★ 六级深度阅读练习与解析 12.22

★ 英语六级考试标准的阅读5

★ 英语六级考试标准的阅读17

★ 英语四级考试仔细阅读每日一练(12.15)

★ 六级阅读练习 2011.03.23

★ 大学英语六级考试快速阅读冲刺的练习