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在法国曾经流传着这样一个童话:一个池塘里生长着一株水百合,它每天能由1株繁殖成2株,这样,第二天是2株,第三天是4株……第10天,池塘已经有了512株水百合。时间一天天过去,到了第29天,水百合占据了半个池塘。“拔掉一些吧!”有人建议。但主人却说:“还有一半水域,着什么急?”到了第30天,主人来到池塘边,一下子傻了眼:整个池塘被水百合覆盖,水中的其他生物都被闷死了。水百合的这种增长,在数学上称为“指数增长”。18世纪末,人口学家马尔萨斯提出了著名的人口“指数增长模型”,但当时并没有引起人们的重视,直到人口爆炸的今天,才成为一个令人关注而又焦虑的问题。
There was a fairy tale in France: a pond has a water lily that grows from 1 to 2 per day, so that the next day is 2 and the third day is 4... 10th day There are 512 water lilies in the pond. Time passed and on the 29th day, the water lily occupied half of the pond. “Unplug some!” Someone suggested. But the owner said, “Half of the water, what anxiery?” On the 30th day, the owner came to the pond and suddenly stared blindly: The entire pond was covered with water lilies, and other creatures in the water were suffocated. This growth of water lilies is mathematically called “exponential growth.” At the end of the 18th century, the demographer Malthus proposed the famous “exponential growth model” of population, but at that time it did not attract people's attention. It was not until the explosion of the population that it became an issue of concern and anxiety.