# Was the Speed of Light known in 13th century India?

The following links claim that there is evidence of the correct speed of light in a Rig Veda Commentary:

Quora: Did Sayana know the Speed of Light

Speed of light in the Rig veda

In the hymn, the author pays respect to the one who moves 2202 yojanas in half a nimish

The metric conversions to support this are:

1 yojan = 4 kose

1 kose = 8000 British yards

1 British yard = 0.9144 m.

and

In the Shrimad Bhagavad:

15 nimishas = 1 kashta

15 kashtas = 1 laghu

30 laghus = 1 muhurta

30 muhurtas = 1 diva-ratri

If these conversions and the hymn are true, then the claim follows (Speed of light under these conversions and using the hymn calculated as 302031036.422 m/s, which is very accurate)

• Is the hymn by Sayana in the 13th-something century
• Are the conversions correct?
• Related question: Did the Quran prodict the speed of light? Commented May 28, 2017 at 6:43
• Possibly too theoretical for an answer, but the person writing it out to the nearest millimetre per second is probably unfamiliar with significant figures Commented May 28, 2017 at 9:41
• @Truth-seek: Both claims seek to validate the miraculous nature of historical religious texts by demonstrating the exact same anachronistic understanding of the physical universe. If you like one, you are likely interested in the other. To be clear, the answer to one might not be the same as the answer to the other (although, one might suspect the fudging techniques, if any, might be similar). Commented May 28, 2017 at 12:04
• @Truth-seek Is related because it's the same kind of nonsense claim, using a similar deceptive spin to lie to people. Commented May 28, 2017 at 12:05
• @KonradRudolph You are quite right, i see Commented May 28, 2017 at 12:37

## 1 Answer

This looks very much as if the units may have been converted to obtain the desired result. Indeed the different conversion factors but similar result in your second link increase the likelihood that there may cognitive bias involved

For example, your distance conversions lead to 1 yojan being 29.2608 kilometres. Compare this with Wikipedia's 12–15 km and your second link's 9.09 miles (about 14.5 km)

Similarly on time, your calculation gives 202,500 nimishas (twinklings of the eye) in a day-night while Wikipedia quotes Manusmṛti to give 486,000 and your second link gives 409,050

Both references reach the same result by different conversion factors, which implies they're both biased and unreliable.

• I think this answer is saying that both references reach the same result but via different means (i.e. by different conversion factors), which implies they're both biased and unreliable. Commented May 28, 2017 at 15:30
• @ChrisW You summarize the answer much better than the actual answerer did. I think the answer could use some edits for clarity. Commented May 28, 2017 at 16:01
• @BobTheAverage or ChrisW - I do not mind if either of you make such an edit, though I had thought that point was clear enough Commented May 28, 2017 at 19:40
• Good answer that show that unit conversions are allowed. Commented May 28, 2017 at 22:21