Earlier we talked about forces, and about exerting forces on bodies. I exerted a force on the wall by pushing against it with my arm. We talked about a car exerting a force on a trailer by pulling on it. Ask the students. The answer is yes, the Earth exerts a force on all objects on its surface, called a gravitational force.
Earth too exerts a force on airplanes.
Indeed the Earth also exerts a gravitational force on objects like the Moon and the Sun and other planets for that matter. In the same way the Sun exerts a force on each and all of the planets. The discovery and understanding of that gravitational force is one of the greatest accomplishments of Newton. In trying to understand this force Newton which objects it affected and how strongly. Every particle of matter in the Universe attracts every other particle with a force that is proportional to the product of the masses of the particles and inversely proportional to the square of the distance between them.