Measuring The Speed of Light

Ancient Indians knew about the speed of light. In fact they calculated it accurately. But the western world says that , “Romar” has first estimated it in the year 1675. To substantiate the Indian version, let us observe the sāyanācārya's commentary on Vedas, which was written in 14th century A.D.

तरणिर् विष्वदर्षटो ज्योतिस्क्रदसि सूर्य विश्व्मा भासि रोचनम् ।

(Rigveda 1.50.4)

For the above Rig Vedic sloka/verse he has written an explanation , revealing the speed of sunlight.

योजनानम् सहस्रम् द्वे द्वे शते द्वे च योजने
एकेन निमिशाधेन क्रम माण नमोस्तु ते ॥

It means that the sunlight travels 2202 yojanas in half a nimisha. Here yojana means 9.11 miles. According to traditional Indian calculations in one fill day (including night) there are 8,10,000 half minutes. That means for one second there are 8/75 half minutes.

Then the speed if light should be 2202 x 9.11 /(8/75) = 1,88,064 miles per second.

The above calculation is very close to the modern value estimated by the 20th century scientists Michealson and Morley I.e 1,86,300 miles per second. The above fact had been clearly mentioned in Maxmullar's compilation of Rigveda,(1890), as he had taken Saayana Bhashya as authority for his work of translating Vedas. Maxmullar had referred to the manuscript of Säyanäcärya's commentary (1395 AD) copy of which is now available in Baroda library for reference.

Note: Yojana according to Arthasastra is equal to 9.11 miles, which is equal to 8000 dhanus. One dhanu is equal to average man's height that is six feet. But Indian Astronomers like Aryabhatta, Brahmagupta had considered one yojana as equal to four krosas, which is equal to five miles.