A DIY model to support understanding of the phases of the Moon

Students often experience difficulties in understanding the phases of the Moon, particularly in relating Earth-based observations to the spatial configuration and motion of the Sun–Earth–Moon system. Persistent misconceptions are well documented. This paper presents a simple, low-cost, do-it-yourself model designed to support conceptual understanding by linking two frames of reference: a heliocentric coordinate system, used to explain the physical origin of lunar phases, and a geographic coordinate system, from which the phases are observed. The model combines a planar representation of orbital motion with a three-dimensional viewing element that enables an Earth-based perspective. By explicitly connecting these viewpoints, the model supports the transition from observation to explanation. The model can be easily constructed from readily available materials and is suitable for use in primary and secondary school classrooms.