  A remarkably tight relation is observed between the Newtonian gravity sourced
by the baryons and the actual gravity in galaxies of all sizes. This can be
interpreted as the effect of a single effective force law depending on
acceleration. This is however not the case in larger systems with much deeper
potential wells, such as galaxy clusters. Here we explore the possibility of an
effective force law reproducing mass discrepancies in all extragalactic systems
when depending on both acceleration and the depth of the potential well. We
exhibit, at least at a phenomenological level, one such possible construction
in the classical gravitational potential theory. Interestingly, the framework,
dubbed EMOND, is able to reproduce the observed mass discrepancies in both
galaxies and galaxy clusters, and to produce multi-center systems with offsets
between the peaks of gravity and the peaks of the baryonic distribution.
