This longitudinal study examined the acquisition of early knowledge of astronomy to determine whether children's knowledge at any point in time is consistent with a naive "mental model." Children were first assessed by means of open questions and drawing tasks at 2 and 3 years of age (N = 143). The knowledge was reassessed over the course of the following 3 years. The results showed that although a few indications of naive mental models were found, in most cases young children's knowledge was fragmented and accurate knowledge was often expressed alongside inaccurate/synthetic ideas. Furthermore, it was shown that children need to know scientific facts before they start taking the global perspective when describing the world and, when faced with ambiguous open questions, children often experience difficulties that can induce them to change the types of answers they provide. (Contains 3 tables.)