These longitudinal studies investigated the cultural mediation of children’s thinking about the Earth using an interview technique designed to elicit responses from children from all “levels” of their conceptual organization (intuitive, cultural, and scientific). Close scrutiny of the research literature in this field reveals that some strategies used in the past to probe children’s ideas have been influenced by the background of the interviewer, either in the design of their questions or in the use made of concrete props (e.g., of the Earth’s shape). This has tended to obscure the degree of cultural influence in those interviewed. Central to the current research was the development of an interview method (“instrument attunement”) that was flexible, culturally adaptable, and could be tuned to the response level of the child. The participants included 129 boys and 113 girls from China, and 217 boys and 227 girls from New Zealand. The methodology utilizing observational astronomy led into discussion of the motion and shape of the Earth, Sun and Moon. Surprisingly, the development of children’s concepts was found to be remarkably similar within the three main ethnic groups (Han, New Zealand European and New Zealand Maori) in the two cultures (China and New Zealand). Cases of cultural mediation were detected using the new methodology but these could be assimilated into a common taxonomy of cosmological concepts for all participants.