The Eddington-Finkelstein spacetime is
ds^2 = -(1-2M/r)dt^2 + 4M/r drdt +(1+2M/r)dr^2 +r^2dOmega^2
Use the t-r part of this metric and compute the behavior of scalar
radiation in this two-dimensional spacetiem. Note that the lapse is
not equal to one, and the twospace is not flat.