I have a question on convention regarding the universal law of gravitation formula. Sometimes the distance is represented with the lowercase r and sometimes with the uppercase R. Why is it listed two different ways? I am thinking that r is the total distance and R is the radial distance, no? For example, the distance to a satellite might be r = R + h, where r is total distance, R is the radius of the planet and h is the distance from the surface of the planet to the satellite. I am wondering what the convention is.