Abstract
The purpose of this research is to clarify how ninth graders in lower secondary schools acquire a spatial understanding of planetary phases and an ability to explain them in a scientific way by asking them to draw planetary phase angles and grasp the positional relationship between the Earth and other planets in the learning of the phases of the Moon and Venus. Subjects in an experimental group were asked to make hypotheses that explain the phases of planets and to verify them after grasping the positional relationship between the Earth and other planets by drawing planetary phase angles. On the other hand, subjects in a control group were asked to do the same thing without drawing them. Then, each group's levels of spatial perception, understanding of planetary phases, and ability to make a scientific explanation of how they occur were examined by conducting a questionnaire survey. The results showed that the level of spatial perception of the phases of the Moon and Venus in the experimental group was statistically significantly higher than in the control group. The number of students who could explain them in a scientific way was also higher in the experimental group than in the control group at a statistically significant level. It is suggested that the attempt to help students grasp the positional relationship between the Earth and other planets by drawing planetary phase angles was effective in enhancing their spatial perception and understanding of the phases of planets, and helped developing their ability to explain it in a scientific way.
