  We apply the effective approach to evaluating semiclassical relational
dynamics to the closed Friedman--Robertson--Walker cosmological model filled
with a minimally coupled massive scalar field. This model is interesting for
studying relational dynamics in a more general setting because (i) it features
a nontrivial coupling of the relational clock to the evolving degrees of
freedom, (ii) no temporally global clock variable exists, and (iii) it is
nonintegrable which is typical for generic dynamical systems. The effective
approach is especially well geared for addressing the concept of relational
evolution in this context, since it enables one to switch between different
clocks and yields a consistent (temporally) local time evolution with transient
observables so long as semiclassicality holds. We provide evidence that
relational evolution in this model universe, while possible for sufficiently
semiclassical states, generically breaks down in the region of maximal
expansion. This is rooted in a defocusing of classical trajectories, which
leads to a rapid spreading of states that are initially sharply peaked and to a
mixing of internal time directions in this region. These results are
qualitatively compared to previous work on this model, revisiting conceptual
issues that have been raised earlier in the literature.
