Speed of Light in Hindu scriptures-
(Thread)

Speed of Light was well known in Ancient India, Acharya Sayana in his commentary on Rigveda 1.50.4 s
Mentions It

He says,

"It is to be remembered that light from sun travels 2202 Yojanas in half a Nimisha"

This Yojana and Nimisha are ancient units if Measurements, I will convert them to modern measurements here

According to Manusmriti 1.64

18 Nimesha = 1Kastha
30 Kastha = 1 Kala
30 Kala = 1 Muhurta
30 Muhurta = 24 hours

Hence I Nimisha = 1.777777778s

And Half Nimisha = 0.88888889s

Now Yojana it is generally taken as 8 Miles but that's an error, because it was used to measure distances on land and due to error in measurement and comparison the value should be 7.5 miles.

Same thing said by Alexander Cunningham In his Ancient Geography of India

Hence light travels 2202×7.5 miles in 0.888888889 seconds the result is

= 18579.37499.. Miles per second

Modern Measurement = 186282 miles per second

Very close considering Yojana is a Approximation and not exact.

So it is proved that Ancients knew speed of light

A slight typing error, it is 0.1777777 seconds, hence .5 Nimish = 0.088888889

Hence final speed would be =
185,793.74997677