There is the equation $ds^2 = c^2dt^2-dx^2-dy^2-dz^2$ in special relativity(Special relativity). Special relativity theory assumes that gravity is constant. So, we can set $dr^2= dx^2+dy^2+dz^2$. If the $\gamma$ effect occurs along the arc of a circle with a constant diameter, it also affects the diameter $r$. In other words, $2\pi{dr}=2\pi\gamma{dr'}=>dr=\gamma{dr'}$ $r$ direction is the direc..
