In the present study, we test the effectiveness of a teaching intervention aiming at acquainting children aged four to six years with the concept of the sphericity of the earth and the causes of the phenomenon of day and night. The treatment comprised three units of activities that were developed collaboratively by a researcher and early years teachers employing action research processes. In the present study, student knowledge is considered context specific. The selected approach to learning can be characterized as socially constructed. In the activities, children were presented with appropriate information along with conceptual tools, such as a globe and an instructional video. The activities were implemented in a sample of 104 children of the above age group. Children's learning outcomes were assessed two weeks after the activities. Assessment tasks comprised children's construction and handling of concrete 3-D material models, children's use of pictures and the globe, and children's verbal explanations. Results revealed awareness of the concepts and events that the activities dealt with in high percentages of children and children's storage of new knowledge in the long-term memory and easy retrieval from it. The outcomes suggest that the approach adopted in the present study is fruitful and promising for helping very young children develop their understanding of fundamental astronomical concepts and events considered difficult for their age and for raising their motivation for astronomy. The approach used in the present study could also find application in other areas of science. (Contains 1 table and 7 figures.)