  We investigate aspects of the four-dimensional effective description of brane
world scenarios based on warped compactification on anti-de Sitter space. The
low-energy dynamics is described by visible matter gravitationally coupled to a
``dark'' conformal field theory. We give the linearized description of the 4d
stress tensor corresponding to an arbitrary 5d matter distribution. In
particular a 5d falling particle corresponds to a 4d expanding shell, giving a
4d interpretation of a trajectory that misses a black hole only by moving in
the fifth dimension. Breakdown of the effective description occurs when either
five-dimensional physics or strong gravity becomes important. In scenarios with
a TeV brane, the latter can happen through production of black holes near the
TeV scale. This could provide an interesting experimental window on quantum
black hole dynamics.
