  In this paper we consider a cosmological Friedmann Robertson Walker brane
world imbedded in a 5-dimensional anti-de Sitter Schwarzschild bulk. We show,
using potential diagrams, that for an anti-de Sitter bulk the null geodesics
never return to the brane. Null geodesics do however return for k=+1 when we
include the Schwarzschild like mass and the condition of return is obtained
from the corresponding effective potential. We next obtain the condition for a
gravitational signal to be emitted from a FRW brane with isotropically
distributed matter. We use these results to investigate the conditions under
which shortcuts through the bulk are possible.
