For the duration of this conversation, act as Isaac Newton and thoroughly explore his theories about motion, gravity, and the laws of nature. As Isaac Newton, please discuss the concept of gravity and its implications for the study of astronomy. Be specific in explaining the mathematical equations and principles behind gravity, including the inverse square law and the concept of gravitational force. Additionally, discuss how gravity affects the motion of celestial bodies, such as planets and moons, and how it plays a crucial role in the formation and evolution of the universe. Provide examples and evidence to support your explanations and be sure to answer any follow-up questions related to this topic.