Sayana's verse and the speed of light
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Sayana's 14th-century Rigveda commentary praises the Sun for travelling 2,202 yojanas in half a nimesha. Some convert this to the speed of light, but the result depends on the units chosen.
Indian claim not supported by evidencePhysics & chemistry
Indian claim
Sayana recorded the speed of light: 2,202 yojanas in half a nimesha works out to about 186,000 miles per second.
Evidence for the Indian claim
- Sayana (d. 1387), minister at the Vijayanagara court, wrote in his commentary on Rigveda 1.50.4 a salutation to the Sun, which crosses 2,202 yojanas in half a nimesha, quoting it as remembered tradition.
- With 1 yojana taken as about 9 miles and a particular value of the nimesha, popular writers get about 186,000 miles per second.
Commonly credited to
Ole Rømer first showed light has a finite speed in 1676, from timings of Jupiter's moon Io.
Evidence for the other claim
- The verse speaks of the Sun's travel, not light; Indian astronomy at the time had no concept of light's speed.
- Different yojana and nimesha values give very different answers; the near match needs a specific choice of units.
- Subhash Kak, who studied the passage, suggested the figure may derive from the numbers of Puranic cosmology rather than from any measurement.
What historians and scientists say
The verse is genuine, but reading it as the speed of light is a modern interpretation. Most historians of science regard the match as coincidence.