  Condensed matter systems, such as acoustics in flowing fluids, light in
moving dielectrics, or quasiparticles in a moving superfluid, can be used to
mimic aspects of general relativity. More precisely these systems (and others)
provide experimentally accessible models of curved-space quantum field theory.
As such they mimic kinematic aspects of general relativity, though typically
they do not mimic the *dynamics*. Although these analogue models are thereby
limited in their ability to duplicate all the effects of Einstein gravity they
nevertheless are extremely important -- they provide black hole analogues (some
of which have already been seen experimentally) and lead to tests of basic
principles of curved-space quantum field theory. Currently these tests are
still in the realm of *gedanken-experiments*, but there are plausible candidate
models that should lead to laboratory experiments in the not too distant
future.
