The gravity model is a quantitative technique used in economics and geography to explain and predict the flow of goods, services, people, and information between two locations. It is based on the principle that the volume of interactions between two locations is proportional to their sizes (e.g., population or economic activity) and inversely proportional to the distance between them. The gravity model has been widely used in various fields such as international trade, transportation planning, migration studies, and urban economics. It helps researchers understand the factors driving these interactions and can be used to forecast future patterns of movement or trade. The model typically takes the form of a mathematical equation that incorporates variables such as the size of the origin and destination locations, the distance between them, and potentially other factors such as transportation costs or cultural similarities. By estimating the parameters of the equation using data on actual interactions, researchers can quantify the strength of the relationship between the variables and make predictions about future patterns of movement or trade.