Four sources told it. That when they had the plague in Cambridge, and he went down to his mother's farm -- because the university was closed -- he saw an apple fall from a tree, or on his head or something.
它有四个来源。当剑桥大学爆发瘟疫时， 牛顿回到到他母亲的农场，由于大学停课了 他看到苹果从树上落下来, 砸到了他的脑袋或者其他什么东西，