Heavenly talk:: Discourse, artifacts, and children's understanding of elementary astronomy

In the literature on children's understanding of astronomical concepts, such as the shape of the earth and gravitation, the difficulties that children have in conceptualizing these phenomena have been documented in many studies. The purpose of this research is to critically scrutinize these findings by taking a situated and discursive perspective on reasoning (and cognitive development). Instead of viewing understanding as the overt expression of underlying mental models, children's responses in interview studies should be regarded as situated and as dependent on the tools available as resources for reasoning. By modifying the interview situation through the introduction of a globe as a tool for thinking, the outcomes are radically different from those reported earlier. None of the problems that have been reported, where children, for instance, claim that people can fall off the earth, can be detected. Even among the youngest participants gravitation is often invoked as an explanatory concept. It is argued that the globe in this case serves as an efficient prosthetic device for thinking, and this illustrates the tool-dependent nature of human reasoning.