Petrospheres and Cup-and-Ring Marks as Reflective Solar Instruments in Chalcolithic and Bronze Age Seafaring Contexts

Below is a publication‑ready Zenodo description tailored precisely to your paper, grounded directly in the uploaded document and citing it appropriately. It follows the tone and structure expected for a research‑data repository entry: concise, formal, and focused on contribution, method, and significance. Zenodo Description (Final Version) This paper presents the first systematic experimental evaluation of how Neolithic carved stone balls (“petrospheres”) interact optically with cup‑and‑ring petroglyphs when placed within their central cups. Fieldwork at Achnabreck, Argyll and Bute, combined with controlled solar and lunar experiments in Rugby, demonstrates that spherical objects of petrosphere dimensions produce predictable reflective highlights and shadow behaviours under sunlight and moonlight, especially when surfaces are wetted. As noted in the paper, “petrospheres or comparable spherical objects placed within cup‑and‑ring settings can produce predictable reflective and shadow behaviours under sunlight and moonlight” . Measurements of carved geometry at Achnabreck confirm deliberate proportions compatible with seating a sphere, while observations show that highlights and shadows correspond consistently with the Sun’s apparent azimuth and altitude. The study also extends the same optical principle to lunar conditions, demonstrating visible moonlight reflections and directional shadowing, supporting the possibility of night‑time lunar bearing awareness. As the paper states, “moonlight reflected from a wetted or polished spherical surface can form a visible highlight, while the sphere’s shadow extends in the opposite direction” . Within the broader Chalcolithic and Bronze Age maritime context, these behaviours suggest that petrospheres and cup‑and‑ring carvings may have served as practical solar–lunar indicators relevant to timekeeping, orientation, seasonal awareness, and tidal timing—skills essential for prehistoric seafaring communities operating without mechanical clocks. Comparative evidence from Atlantic Europe, including Iberian segmented ring carvings, further supports the plausibility of functional observational roles alongside symbolic interpretations. The paper emphasises falsifiability and outlines future testing across seasons, moon phases, and additional sites. While not claiming definitive proof, it demonstrates that the physical behaviour of spheres and carved panels warrants serious consideration as part of a broader prehistoric observational framework.