  Teaching cosmology at the undergraduate or high school level requires
simplifications and analogies, and inevitably brings the teacher into contact
with at least one of the pedagogical interpretations of the expanding universe.
The by far most popular interpretation holds that galaxies in an expanding
universe are stationary, while space itself expands and thus causes the growing
distances that characterize cosmic expansion. The alternative relativistic
explosion interpretation regards cosmic expansion as a pattern of
(relativistic) galaxy motion. The aim of this article is to discuss the two
competing interpretations from the perspective of potential student
preconceptions, taking into account both beneficial anchoring conceptions and
potentially harmful preconceptions that can lead to misconceptions.
