Vaidya metric
= Vaidya metric
{c}
{title2=$ds^2=-(1-2M(v)/r)dv^2+2dv\,dr+r^2d\Omega^2$}
The ingoing Vaidya metric describes a spherically symmetric spacetime sourced by radial null matter, using advanced time $v$ and areal radius $r$. In geometrized units it is $ds^2=-(1-2M(v)/r)dv^2+2\,dv\,dr+r^2d\Omega^2$. A constant mass function reduces it to the <Schwarzschild metric> in ingoing null coordinates; a varying mass function changes the curvature and the radial <null geodesics>.