上图为William Stukeley的手稿，记录了 1726年他和牛顿的一次对话。完整的手稿可以在皇家学会网站看到[1]。
转录英文如下（粗体是我加的）：
... We went into the garden, & drank tea under the shade of some appletrees, only he, & myself. amidst other discourse, he told me, he was just in the same situation, as when formerly, the notion of gravitation came into his mind. "why should that apple always descend perpendicularly to the ground," thought he to him self: occasion'd by the fall of an apple, as he sat in a comtemplative mood: "why should it not go sideways, or upwards? but constantly to the earths centre? assuredly, the reason is, that the earth draws it. there must be a drawing power in matter. & the sum of the drawing power in the matter of the earth must be in the earths centre, not in any side of the earth. therefore dos this apple fall perpendicularly, or toward the centre. if matter thus draws matter; it must be in proportion of its quantity. therefore the apple draws the earth, as well as the earth draws the apple."
不过，牛顿本人这个信源可靠吗？
这件事情牛顿在自己的书里只字未提。1726年牛顿已经83岁了（次年他就去世了），苹果事件发生在整整60年前。如果这个故事确实就是这样发生的，他为啥不早讲给别人听呢。
从他的手稿来看，他已经确信重力的存在了。当时在考虑的问题不是苹果为何下坠，而是重力是否能外推到月球这样地外的物体。再说，关于苹果为什么下落而非向上的问题，又不是没人问过，亚里士多德两千年前就给出过一个解答了（虽然是错误的）。
所以可能性比较大的猜测是，牛顿也许真的见到了苹果落地，但是苹果的作用在他晚年”讲故事“的时候，被夸大了。我们给别人讲故事的时候也会有意无意戏剧化一些细节，何况牛顿一个八十岁老人讲的是他一生中最辉煌的发现之一呢。
作者: 单线程 时间: 2016-6-25 17:25
生活的主要悲剧，就是停止斗争。
