用英语介绍万有引力定律，包括发现者的成就和定律意义

The law of universal gravitation, discovered by English scientist Sir Isaac Newton, states that every object in the universe attracts every other object with a force which is directly proportional to the product of their masses and inversely proportional to the square of the distance between them. This law explains why objects fall to earth and why planets orbit around stars. It is one of the most important scientific discoveries ever made, and has enabled us to understand many aspects of our universe.