# why is exchange force inversely proportional to square of distance? [duplicate]

Gravitational force is inversely proportional to the square of distance. Coulomb's force is inversely proportional to the square of distance. By biot savart law, magnetic field is inversely proportional to the square of distance. It can be explained by using field lines that these quantities are inversely proportional to the area (circle which is $\frac{1}{4}\pi \times$ diameter$^2$) produced by the two charges . But in reality they extend in three dimensions then it should be inversely proportional to cube of distance. It can also be explained using different data collected from experiments where all other quantities except distance is kept constant. What is the theoretical explaination for them to be inversely proportional to the square of distance ?