It’s impossible to have been so accurate back when the gemara was written
I blogged about this two years ago. To summarize:
1. If you can count days and lunar cycles, you can come up with a pretty good estimate for the lunar period. All you have to do is note the number of days and lunar months between solar or lunar eclipses and divide. The more data points you have (i.e. the more eclipses observed), the more exact your figure for the lunar cycle will be.
2. Secondly, this is presented in the Gemara as a tradition that Rabban Gamliel received from his father that the moon’s period is not less than 29 days, 12 hours, 40 minutes and 73 chalakim. Let’s assume, for the moment, that the statement is true (which, to the best of my knowledge, it is). What does it prove? It proves that Rabban Gamliel’s father knew the period of the moon, nothing more. Even if you posit that HKBH came to Rabban Gamiliel’s ancestors and told them “The period of the moon is not less…,” all it proves is that they knew it. It certainly doesn’t prove that everything (or even anything) is in the Torah is true.
Do we really know how much knowledge the Greeks and Romans garnered before the onset of the Dark Ages?
Forget the Greeks and Romans… it’s older than that. The Babylonian astronomer Naburimani calculated the synodic period of the moon several centuries before Rabban Gamliel.
The Wolf
P.S. By the way, it’s a common assumption/fallacy that the ancients (i.e. non-Jewish) astronomers/scientists couldn’t have known anything without watches, telescopes and the like. If you want to get a good idea of how much you can learn about the Earth from just a stick, stone and a rope, read Chapter 5 of Neil DeGrasse Tyson’s excellent book “Death by Black Hole.”
The Wolf