On the "possibly" side of the argument:
The diameter of the earth was calculated in 240 BCE by Eratosthenes (same guy that made the geographical coordinate system) in Alexandria, near the mouth of the Nile River by the Mediterranean coast, in northern Egypt. His result depended on measuring the distance between Alexandria and Syene, which was found to be 5000 stadia. Unfortunately, the stadion was not universally standardized and we don't know which one he was using. Worst case, he was off by 16%, which is pretty amazing for the measurement tools available and the multiplication of any errors by the resulting scaling up. Best case, he was only off by 1%, which is conceptually staggering.
I bring this up because the meter was originally based (in 1793) as one ten-millionth of the distance from the equator to the North Pole. If you know the size of the earth, you could easily derive a unit that would be similar, just with the decimal point in a different place depending on the scale you were interested in. I would expect such a thing to appear in records, but as mentioned, a great deal of knowledge was lost with the Library of Alexandria.
On the "pretty sure it isn't" side of the argument:
So, I can't rule out the meter side of the measurement, but I would like to throw a few other pieces of doubt at this theory:
- Precision: 299,792,458 is insanely precise. 1% error on that would give you numbers between 296,000,000 and 302,000,000. The tools necessary to get that precise are, shall we say, involved... And it's only that very specific number because in 1983 they redefined the meter in terms of the speed of light to get rid of some extra noise in the fractions that they'd worked out.
- "per second" requires accurate measurement of the second. I'm not sure if this is a problem or not... "Seconds" were derived from astronomical observation as early as the third millennium BC (thousands of years before the size of the Earth was calculated), but rather than being 1/3600 of an hour, they were 1/3600 of a day (so they were 24 modern seconds long). As far as we know, reliably measuring modern seconds was not possible until between 1560 and 1570 AD (or CE if you prefer), but, again, the loss of most of Western civilization's knowledge means we could be missing something. However, any variation at all in the length of a second will significantly change the resulting m/s value for the speed of light.
- A much bigger problem is the origin point for east/west measurement, the Prime Meridian. East/west positions are measured by angular distance away from the Prime Meridian, and in those times:
In the 1st or 2nd century, Marinus of Tyre compiled an extensive gazetteer and mathematically-plotted world map using coordinates measured east from a prime meridian at the westernmost known land, designated the Fortunate Isles, off the coast of western Africa around the Canary or Cape Verde Islands, and measured north or south of the island of Rhodes off Asia Minor. Ptolemy credited him with the full adoption of longitude and latitude, rather than measuring latitude in terms of the length of the midsummer day.[4]
Ptolemy's 2nd-century Geography used the same prime meridian but measured latitude from the Equator instead. After their work was translated into Arabic in the 9th century, Al-Khwārizmī's Book of the Description of the Earth corrected Marinus' and Ptolemy's errors regarding the length of the Mediterranean Sea,[note 2] causing medieval Arabic cartography to use a prime meridian around 10° east of Ptolemy's line.
Modern lat/lon coordinates use the Prime Meridian going through Greenwich instead (no longer technically true, as standardization moved it slightly, but the point remains). That change means that ancient and modern longitude differs by approximately 20 degrees. https://en.wikipedia.org/wiki/Prime_meridian#History
I have to chalk this one up as one of those insane coincidences. Either that, or God has a strange sense of humor...
Latitude, on the other hand, can be derived directly once you've got the size of the Earth, so if you found correlations with the North/South coordinate, those would be harder to argue with
(Debunked or not, it's still pretty cool that it happens to work out that well. I didn't bother to go look at the tectonic plate movement direction, but that was a fun thing to throw in there, and to remember in any similar theories.)
