  It is the common consensus that the expansion of a universe always slows down
if the gravity provided by the energy sources therein is attractive and
accordingly one needs to invoke dark energy as a source of anti-gravity for
understanding the cosmic acceleration. To examine this point we find
counter-examples for a spherically symmetric dust fluid described by the
Lemaitre-Tolman-Bondi solution without singularity. Thus, the validity of this
naive consensus is indeed doubtful and the effects of inhomogeneities should be
restudied. These counter-intuitive examples open a new perspective on the
understanding of the evolution of our universe.
