Newton reasoned that if the Earth can attract an apple and the moon, then all objects in the universe must attract each other, leading to the concept of gravitational force between all objects.

Newton observed that all planets orbit around the Sun, suggesting the presence of a force between them, similar to the force between the Earth and the moon.

Newton observed that the motion of the moon around the Earth resembled the motion of objects falling towards the Earth’s surface, prompting him to consider whether the Earth’s gravitational force also affects the moon.

The centripetal force continuously pulls objects towards the center of their circular path, preventing them from moving in a straight line and maintaining their circular motion.

In circular motion, the tangent to the circular path represents the direction an object would take in the absence of a centripetal force, moving in a straight line.