Measuring $T_k$

From the previous post, "Only If You Started Somewhere" dated 27 Dec 2017,

in the case of,

when $\Delta T=0$ ie. $T=T_g$,  $r$ is a measure for $T_k$ up to $V=0$.  $r$ need not be at infinity, just

$\left.V=0\right|_{r=r_o}$

when ever $V=0$ at $r_o$.