Our project investigate how pre-service teachers and science experts (space physicists, chemists and biologists) engage with spatial scale reasoning through epistemic games - structured approaches to scientific inquiry and problem-solving. Spatial thinking is foundational to STEM success, yet understanding scales beyond direct human experience remains challenging for many learners (Tretter et al. 2006; Eriksson et al. 2014).Our studies involve four groups: primary school pre-service teachers, chemists, biologists and space physicists. Each group participates in a four-part game-based activity: arranging large astronomical objects by size, adding a human figure for scale reference, repeating the process with microscopic objects, and explaining their reasoning to a novice. Video recordings were analyzed using thematic analysis.We identified three major themes of epistemic games: Cognitive Anchoring, Object Relatedness, and Perspectives.While pre-service teachers employed similar epistemic games as science experts, they demonstrated unique engagement through pedagogical expertise, particularly in contextual perspectives. However, they made more errors with microscopic objects despite using similar reasoning strategies. This suggests that while epistemic games provide valuable reasoning tools, their effectiveness depends on underlying conceptual knowledge.Our findings have implications for teacher preparation programs and science programs, highlighting the need to strengthen both conceptual frameworks and strategic reasoning about spatial scales. This research contributes to understanding how future astronomy and science educators develop the spatial thinking skills that research has established as critical predictors of STEM success and scientific literacy in contexts ranging from the smallest to the largest structures known.