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Description
Understanding how non major undergraduates conceptualise astronomical sizes and distances is critical for effective introductory teaching. We report a pre instruction diagnostic survey (n = 220) from a first year, first semester breadth astronomy unit. The instrument used a scale model framing (1 cm “blueberry” Earth) to elicit numeric estimates for Moon, Sun, Proxima Centauri, Milky Way, Andromeda, and the observable Universe, together with a relational ordering task, conceptual multiple choice items, confidence ratings, affective prompts, and open ended explanations. Preliminary inspection shows widespread order of magnitude errors and four dominant misconception clusters: scale compression, hierarchy/containment confusion, scale inversion, and unit confusion. Confidence ratings and affective items indicate many students hold these misconceptions with at least moderate certainty, suggesting stable but inaccurate mental models. Open responses emphasise three recurring themes: incomprehensible magnitude, human smallness, and questions about expansion and measurement. The survey functions as the primary diagnostic instrument: it both reveals common error patterns and provides the raw material for subsequent coding and intervention evaluation. We present a provisional taxonomy of misconception clusters, illustrative student reasoning, and recommendations for short diagnostic checks instructors can deploy immediately to detect the most frequent errors in reasoning about cosmic scale. These diagnostics are intended to guide targeted instruction and to improve alignment between teaching strategies and the conceptual bottlenecks they aim to resolve.
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