Investigation of children's understanding of the earth provides important insights into the origins of children's knowledge, the structure of their concepts, and the development of scientific ideas. Vosniadou & Brewer (Citation1992) proposed that, under the influence of intuitive constraints and observations, children form naïve but coherent mental models of the earth: for example they believe it to be flat, or that we live inside a hollow sphere. To test this claim, 59 children aged 6 – 8 years and 33 adults were given multiple-choice questions and a 3D model selection task. This approach avoided the criticisms of recent studies by providing participants with a full range of possible answers. Even the youngest children preferred scientific responses and so demonstrated some knowledge of the earth. Only 10% of the children showed any evidence of naïve mental models; other participants who gave non-scientific answers were inconsistent and unsystematic. It is argued that intuitive constraints have little or no influence on the development of children's ideas in this domain, and that emerging knowledge of the earth progresses from being fragmented to consistently scientific.