读者“葡萄果”问:“从超市购买的食品,通过称重可以知道它的质量,那么像地球这样大的物体,我们如何获知它的巨大质量呢?”要回答这个问题,先要了解牛顿在1687年正式发表的万有引力定律.它表述为:任何两个物体间均存在相互吸引力,若物体可视为质点,则两质点间的相互吸引力f沿两质点的连线,与两质点的质量m_1和m_2的乘积成正比,与它们间距离r的平方成反比,即 Readers “grapefruit ” Q: “From the supermarket to buy food, weighed to know its quality, so big objects such as the Earth, how do we know its great quality?” "To answer this question, First understand Newton’s law of universal gravitation formally published in 1687. It states: any two objects are attractive to each other, if the object can be regarded as particle, the mutual attraction between the two particles f along the two points of the line , Proportional to the product of the masses of the two masses m_1 and m_2 and inversely proportional to the square of the distance r between them