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<p>The prediction of planetary First/Last Visibility features prominently in the observational records and calendrical computations of many ancient cultures, although the ways in which these events were conceptualised and operationalised differ substantially. Focusing on the First/Last Visibility of the five classical planets (Venus, Jupiter, Mercury, Mars, and Saturn), this article reviews and compares the relevant textual evidence and computational procedures in Babylonian, Greek, Arabic, Indian, and Chinese traditions. A cross-cultural analysis shows that these visibility events were widely recognised as salient nodes within planetary synodic cycles across the traditions examined. Babylonian sources, however, tend to treat them as observationally significant without articulating a single, explicit and general criterion for judgement. In Greek and Arabic astronomy, shaped by geometric modelling, visibility was commonly handled through dedicated procedures adjunct to core positional computation, with careful attention to geographic latitude, seasonal geometry, and planetary ecliptic latitude. By contrast, Indian and Chinese approaches, largely procedure-based and algorithmic, typically treated First/Last Visibility as special cases within broader planetary computations and often did not incorporate planetary ecliptic latitude as an explicit parameter. Nevertheless, with the partial exception of the Babylonian material, the traditions surveyed most consistently relied on the Sun–planet separation—usually ecliptic elongation, and in some cases separation expressed in equatorial coordinates—to decide visibility. Comparison with modern visibility theory and our numerical simulations further indicates that elongation-based criteria are strongly conditioned by geographic latitude and seasonal observing geometry. Although such criteria are not highly precise, they are practical and intelligible, and in many historical contexts they were adequate for the predictive needs of working astronomers and calendar-makers. By clarifying both shared assumptions and systematic divergences in these traditions, this study contributes a comparative framework for understanding how visibility phenomena were incorporated into ancient astronomical theory and practice.</p>

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Planetary first and last visibility in ancient astronomy: a cross-cultural comparison

  • 期刊论文

  • 发表日期：

    2026年3月7日

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  • Zhenhua Wang,
  • Ruilin Zhang,
  • Quan Tang

摘要

The prediction of planetary First/Last Visibility features prominently in the observational records and calendrical computations of many ancient cultures, although the ways in which these events were conceptualised and operationalised differ substantially. Focusing on the First/Last Visibility of the five classical planets (Venus, Jupiter, Mercury, Mars, and Saturn), this article reviews and compares the relevant textual evidence and computational procedures in Babylonian, Greek, Arabic, Indian, and Chinese traditions. A cross-cultural analysis shows that these visibility events were widely recognised as salient nodes within planetary synodic cycles across the traditions examined. Babylonian sources, however, tend to treat them as observationally significant without articulating a single, explicit and general criterion for judgement. In Greek and Arabic astronomy, shaped by geometric modelling, visibility was commonly handled through dedicated procedures adjunct to core positional computation, with careful attention to geographic latitude, seasonal geometry, and planetary ecliptic latitude. By contrast, Indian and Chinese approaches, largely procedure-based and algorithmic, typically treated First/Last Visibility as special cases within broader planetary computations and often did not incorporate planetary ecliptic latitude as an explicit parameter. Nevertheless, with the partial exception of the Babylonian material, the traditions surveyed most consistently relied on the Sun–planet separation—usually ecliptic elongation, and in some cases separation expressed in equatorial coordinates—to decide visibility. Comparison with modern visibility theory and our numerical simulations further indicates that elongation-based criteria are strongly conditioned by geographic latitude and seasonal observing geometry. Although such criteria are not highly precise, they are practical and intelligible, and in many historical contexts they were adequate for the predictive needs of working astronomers and calendar-makers. By clarifying both shared assumptions and systematic divergences in these traditions, this study contributes a comparative framework for understanding how visibility phenomena were incorporated into ancient astronomical theory and practice.