Students' Understanding of Sidereal and Tropical Years and Axial Precession: A Pre- and Post-Instruction Study

The distinction between the sidereal year and the tropical year, and the role of Earth's axial precession in producing this difference, represents a foundational element of celestial mechanics. Yet these concepts are rarely addressed in secondary physics education, leaving students with limited conceptual grounding in astronomical timekeeping. This study investigates higher secondary students' baseline understanding of these ideas and evaluates the extent of conceptual change following a targeted instructional intervention. Three groups of Grade 11 and Grade 12 students participated: two classroom-based cohorts completed both a pre-instruction awareness survey and a post-instruction conceptual assessment, while a third online cohort completed the same surveys remotely using Google Forms. Pre-survey results reveal exceptionally low awareness of key astronomical constructs, including the sidereal year, the tropical year, axial precession, and equinox drift, indicating the absence of meaningful prior conceptual frameworks rather than the presence of misconceptions. Following a concise instructional session supported by a custom-animated visualisation that depicted orbital geometry and precessional motion, significant improvements were observed in students' ability to explain the physical basis for the differing lengths of the year and the associated observational phenomena. Nonetheless, tasks requiring hypothetical or counterfactual reasoning about precession remained challenging, suggesting limitations in the depth of short-term conceptual restructuring. The findings demonstrate the efficacy of dynamic visualisation tools in supporting conceptual understanding of complex astronomical processes and underscore the pedagogical value of explicitly integrating such phenomena into the physics curriculum.