The Speed of Light

The speed of light was determined by Roemer in 1675. Recently it has been pointed out that an ancient Sanskrit text of 14th century contains the value of the speed of light that is identical to the modern value.

Sayana (1315-1387 A.D.) was a very famous Vedic scholar. He was the prime minister in the court of Emperor Bukka I and his successors of the Vijayanagara Empire. In his commentary on the following verse in the Rigveda he gives the value for the speed of light.

"O Sun! You see all, create brightness and travel very fast. You brighten the whole sky." Rigveda 1.50.4

Sayana comments: "It is remembered that Sun traverses 2,202 yojanas in half a nimesa."

It is to be noted that Bhatta Bhaskara (probably in 10th century) made the same statement in his commentary on Taittiriya Brahmana. He says this to be an old Puranic tradition.

Yojana is an ancient unit of length. Arthasastra defines it as being equal to 8,000 dhanus, which is equivalent to 9 miles. Nimesa is an ancient unit of time. One nimesa is equal to 16/75 seconds. Thus 2,202 yojanas in half a nimesa is equal to 185,794 miles per second after conversion. This is very close to the value of 186,000 miles per second for the speed of light. Why would Sayana call this the speed of the Sun? The speed of the Sun calculated by Indian astronomers was very small compared to this value.

This subject has been discussed in detail in a scholarly article ("The Speed of Light and Puranic Cosmology", Subhash Kak, "Computing Science in Ancient India", editors T. R. N. Rao and Subhash Kak, 1998, pp 80-90).