translation.en: Newton had given the world a theory of gravity in the late 1600s that works well, describes the motion of planets, the motion of the moon and so forth, the motion of apocryphal of apples falling from trees, hitting people on the head.
translation.zh: “牛顿”已经在17世纪末提出了重力理论 该理论可以正确地描述了星球间的运动， 月亮的运动等等， 但这个导致苹果坠落的令人质疑的运动， 一直困扰着大家。