Notion of Obliquity of Ecliptic Implied in the Concept of Mount Meru in Jambudvipa Prajnapti

Summary

Using the Jain canonical work Jambudvīpa Prajñapti, S.S. Lish and S.D. Sharma examine whether the description of Mount Meru encodes knowledge of the obliquity of the ecliptic – the tilt of the earth’s axis relative to its orbital plane. The authors note that Jambudvīpa Prajñapti belongs to the post-Sūtrakṛtāṅga period of the Śvetāmbara canon and is significant for its cosmological descriptions. In the text Mount Meru is the axis around which the cosmos revolves and is described as having the shape of a truncated cone with precise dimensions. The paper explores whether the unusual dimensions of Meru – its height, girth and ratio of peak to base – correspond to the degree of axial tilt. It also examines sixteen name‑variants of Mount Meru found in other sources, ranging from Mandara and Padmarāṇa to Svaruṇasammā, and discusses their etymologies and astronomical significance. The authors argue that several Jaina notions, such as the idea of a flat earth encircled by circular continents and seas (sāmudra sīdhi), can be reconciled with a model in which Meru is inclined at an angle to the pole of the ecliptic. They propose that the projection of the pole of the ecliptic onto a flat earth would appear as a circular area whose centre corresponds to Mount Meru. This model would preserve the cosmographical symbolism of Meru while implicitly recognising that the celestial pole does not align perfectly with the axis of the earth. To support this interpretation, the paper analyses verses from the Jambudvīpa Prajñapti that describe the rising and setting of the sun and the relative lengths of day and night in different regions, noting that these observations can be explained by the earth’s axial tilt. The authors also compare Jain cosmology with early Hindu astronomical texts and with Ptolemaic models, highlighting similarities in the way ancient cultures conceptualised the heavens. Although the paper deals with highly specialised topics, it emphasises the interdisciplinary value of examining religious cosmology through an astronomical lens. By showing that the Jain description of Mount Meru may contain encoded observations about the obliquity of the ecliptic, the article encourages historians to revisit other cosmological myths for hidden scientific insights. The study thus bridges the gap between mythological symbolism and scientific understanding, demonstrating that medieval Indian scholars may have had a more sophisticated grasp of astronomical phenomena than is often acknowledged.