History of science
Pre‑Rømer reflections on the speed of light in Indian texts: a scientific and philological reassessment of Sāyaṇa’s Ṛgveda commentary
Kartik Iyer1, Mohit Gour2, Govind Maurya3
- 1Vigyan Darshan Research Organisation, VDRO Educational Association, Mumbai, Maharashtra, India
- 2School of Artificial Intelligence and Data Sciences, Indian Institute of Technology, Jodhpur, Rajasthan, India
- 3Cell for Indian Sciences and Technology in Sanskrit, IIT Bombay, Mumbai, Maharashtra, India
- Journal / conference
- Proceedings of the Indian National Science Academy
- Pages
- 1–13
- Published
- 3 August 2026
- Citations
- 0
Abstract
In the history of human civilisation, light is one of the most fascinating topics in the fields of science and philosophy. The present study critically examines whether the speed of light was conceptually known in pre-Rømer India or whether its correspondence with modern values reflects a forced interpretation. In medieval India, the reputed commentator Sāyaṇācārya mentioned a formula in his commentary on the Ṛgveda that has been interpreted to represent the speed of light. While some scholars have supported this reading, others dismiss it as a forced interpretation. Drawing upon primary texts such as the Sūryasiddhānta and the works of Āryabhaṭa, Bhāskara II, and Brahmagupta, as well as the Mahābhārata, Manusmṛti, and Purāṇas, the study examines traditional units such as nimeṣa and yojana. These values are then analysed quantitatively and compared with modern measurements. Variations across textual traditions arise from differing reference values for these units, not from conceptual error. The study shows that Sāyaṇācārya’s numerical value for the speed of light, when analysed using traditional units, shows notable numerical proximity to the modern value under certain traditional assumptions.
Keywords
- Philology
- Value
- History of science
- Experimental science