Interesting question! The theory of gravity is generally associated with Newton’s careful observations of everyday interactions. He developed the Law of Universal Gravitation:

Where 𝐹 is the attractive force of two objects (how much two objects are attracted to each other) 𝑚₁ and 𝑚₂ are the masses of the two objects, 𝑟₂ is the distance squared between those objects, and 𝐺 is known as the Universal Gravitation Constant. This constant is found empirically, meaning through careful measurements in experiments. This equation is very accurate for many useful applications, such as sending satellites into deep space using the gravity of the different planets.