  A classical solution where the (scalar) field value moves by an ${\cal O}(1)$
range in Planck units is believed to signal the breakdown of Effective Field
Theory (EFT). One heuristic argument for this is that such a field will have
enough energy to be inside its own Schwarzschild radius, and will result in
collapse. In this paper, we consider an inverse problem: what kind of field
ranges arise during the gravitational collapse of a classical field? Despite
the fact that collapse has been studied for almost a hundred years, most of the
discussion is phrased in terms of fluid stress tensors, and not fields. An
exception is the scalar collapse made famous by Choptuik. We re-consider
Choptuik-like systems, but with the emphasis now on the evolution of the
scalar. We give strong evidence that generic spherically symmetric collapse of
a massless scalar field leads to super-Planckian field movement. But we also
note that in every such supercritical collapse scenario, the large field range
is hidden behind an apparent horizon. We also discuss how the familiar perfect
fluid models for collapse like Oppenheimer-Snyder and Vaidya should be viewed
in light of our results.
