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This research paper, The Speed of Light and Puranic Cosmology, by Subash Kak discusses the various notions of distance between places and also the speed of Sun, light etc.

It mentions that the speed of light is mentioned in the Taittiriya Brahmana of the Yajurveda (in a commentary by Bhatta Bhaskara). This speed is also mentioned to be part of an old puranic tradition.

The speed of light is mentioned as 2,202 yojanas per half nimesa which converts to the correct speed of light (186,000 miles per second).


Question: What is the Shloka where the mention to speed of light is found?

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The speed of light is not directly from the Samhita. It is given by Sayana in commenting 1.50.4 verse of RigVeda. The devata of the verse is Surya. The verse is:

तरणिविश्वदर्शवो ज्योतिष्कृदसि सूर्य । विश्वमा भासि रोचनम् ।।
Swift and all beautiful art thou, O Surya, maker of the light, Illuming all the radiant realm.

As it talks about maker of light. Commentary of Sayana in this verse is as:

तथा च स्मर्यत योजनानां सहस्रम् द्वे द्वे शते द्वे च योजने । एकेन निमिषार्धेन क्रममाण नमोऽस्तु ते ॥

tathA cha smaryata yojanAnAM sahasram dve dve shate dve cha yojane | ekena nimiShArdhena kramamANa namo.astu te ||

It means:

It is remembered, [O Sun] bow to you, you who traverse 2,202 yojanas in half a nimesha.

Here it is talking about speed of Sun. But as it is in the commentary of verse containing maker of light, it is taken as speed of light.

Here by calculation from Purana we know 1 nimisha = 16/75 seconds.

For eg. 2.8 of Vishnu Purana says:

Fifteen twinklings of the eye (Nimeshas) make a Káshthá; thirty Káshthás, a Kalá; thirty Kalás, a Muhúrtta (forty-eight minutes); and thirty Muhúrttas, a day and night: the portions of the day are longer or shorter, as has been explained; but the Sandhyá is always the same in increase or decrease, being only one Muhúrtta. From the period that a line may be drawn across the sun (or that half his orb is visible) to the expiration of three Muhúrttas (two hours and twenty-four minutes), that interval is called Prátar (morning), forming a fifth portion of the day.

The summary is:

15 nimesha = 1 kastha
30 kastha =1 kala
30 kala = 1 muhurta
30 muhurta = 1 day-and-night

Thus 1 nimisha = 86400/(30×30×30×15) =16/75 sec.

Thus half-nimisha= 16/150 seconds.

But the distance yojana is highly debatable when converted to metre. Using 1 yojana= 9 mile (which is a general standard value). The value of Yojana is difficult in conversion. It is because value are defined as this way. For eg. In Markandaye Purana.

10 Paramáńus = 1 Parasúkshma; 10 Parasúkshmas = 1 Trasareńu; 10 Trasareńus = 1 particle of dust, or Mahírajas; 10 Mahírajasas = 1 Bálágra, 'hair's point;' 10 Bálágras = 1 Likhyá; 10 Likhyás= 1 Yúka; to Yúkas = 1 heart of barley (Yavodara); 10 Yavodaras = 1 grain of barley of middle size; 10 barley grains = 1 finger, or inch; 6 fingers = a Pada, or foot (the breadth of it); 2 Padas = 1 Vitasti, or span; 2 spans = 1 Hasta, or cubit; 4 Hastas = a Dhanu, a Danda, or staff, or 2 Nárikás; 2000 Dhanus = a Gavyúti; 4 Gavyútis = a Yojana.

Thus it is very difficult to convert exact value of Yojana. Standard value is taken as 8-9 miles. It is obtained as:

Normally 1 hasta= 45 cm. (Hasta is length of hand from elbow to tip of middle finger) We can measure it. Also see Hasta here Thus from above Puranic data. 1 yojana = 45×4×2000×4 = 1440000 cm = 9 miles

Speed=2202×9×150/16= 185793 miles/ second.

The standard scientific value for speed of light is 186322 miles/ second.

Thus they are pretty close together.

The points to be considered here are:

-- The verse itself do not mention the value as speed of light. But as it is in the commentary of "maker of light" people have associated it with speed of light.

-- The value of yojana is a debatable value.

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  • Thanks for the answer, it makes for a valuable asset for anyone unaware of Sayana's commentary, but it is not the answer I am looking for. I am more interested in Bhatta Bhaskara's commentary on the Yajurveda as it happened way earlier than Sayana's commentary on the Rigveda, and thus is more valuable from a chronological perspective. (Sayana's commentary and calculations are also available in the research paper I mentioned) May 12 '16 at 11:22
  • Also, the paper mentions two values of Yojana used: Standard and Puranic. So, I agree with you there. May 12 '16 at 11:23
  • @Amit Saxena Bhatta Bhaskara uses same sloka in his commentary... Anyway Sayana died in 1300 and speed of light was first measured only on 1600...
    – Tezz
    May 12 '16 at 11:25
  • Ya, still the older we can trace it to, the more valuable it becomes :) Also, I am unable to find a translated commentary by Bhatta Bhaskara and hence the question. I found a couple of them but both were purely in Sanskrit. May 12 '16 at 11:30
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The other answer has the shloka attributed to Acharya Sayana. Sayana quotes it in two places - Once while commenting on Rig Veda 1.50.4 and again while commenting on Rig Veda 1.71.9. At both places Rig Veda mentions that movement for Surya is very fast. To establish that Surya indeed moves fast he quotes this verse.

It should be noted that whenever commentators like Sayana refer to a verse with a phrase “तथाच स्मर्यते”, it usually refers to the body of Smriti literature (anything outside Shruti - so it includes Itihasas, Puranasa, Dharmashastra etc.). This is basically saying "this is how it is to be remembered"

In this case the verse is in fact available in Skanda Purana 4.2.18 as Vyasa’a words (notice the slight variation , no smartya )

योजनानां सहस्रे द्वे द्वे शते द्वे च योजने । योजनस्य निमेषार्धाद्याति सोपि चिरं स्थितः ।

He who traverses in half the time of the twinkling of the eye two thousand two hundred and two Yojanas according to human calculation, is also held up for a long time!

Also it is pertinent to point out there is no "नमोऽस्तु ते" in Skanda Purana verse as compared to Sayana's verse. Sayana had it as a prayer, which is not present in the original Skanda Purana verse.

The other answer has derived the value of nimesa as 16/75 secs. But this too isn't constant. There are 30 muhurtas between one sunrise to next. And sunrise does not take place at the same time everyday. So it is not accurate to consider 48 minutes as length of one muhurta.

However fluid definitions of muhurta and yojana mean that one needs to study texts in detail, and not as an excuse to reject the premise that speed of light was unknown.

And as far as सूर्यप्रकाश and सूर्य are concerned there is enough evidence in scriptures that they are used interchangeably

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    @Rickross - I guess i should have quoted from Wikipedia :-D Dec 21 '20 at 8:15
  • @Rickross I think the same person down-voted the question also..
    – hanugm
    Dec 21 '20 at 8:30
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    @Rickross - Msg sent through contact link Dec 21 '20 at 9:15
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    Sure @Rickross ............
    – hanugm
    Dec 21 '20 at 9:25

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