Shapiro time delay
= Shapiro time delay
{c}
Extra propagation time of a light or gravitational-wave signal through a <gravitational field> compared with an appropriate flat-space reference. In a weak static field with <Newtonian potential of a point mass> $\Phi_N<0$, the leading delay along an approximately straight ray is $\Delta t=-2\int\Phi_N\,dl/c^3>0$. The local <speed of light> remains $c$; the integrated geometry changes the relation between emission and reception times.