The late Carl Sagan, a renowned cosmologist and physicist was chief scientist at NASA. In his book Broca’s Brain, he describes how twentieth-century scientists calculated the length of the lunar month by reflecting a laser beam back to Earth from a glass prism placed on the moon by American astronauts. With the aid of powerful telescopes connected to an automatic clock, they’ve computed a time of 29.530388 days. This is the same calculation that Rabban Gamliel came up with thousands of years earlier. He is quoted in tractate Rosh Hoshana as saying , “I have received the traditional information from my paternal grandfather that the lunar month can never be less than 29 and a half days [a half-day being 12 hours], two thirds of an hour and 73 divisions.”and-a-half days, two-thirds of an hour and seventy-three divisions in a lunar month . The total of these two fractions of hours (comprising the ˙ ⅔ of an hour and the several minutes over the ⅔ hour which was stated by the sages as 73 divisions), are now converted to a common denominator of divisions. These two fractions of an hour when combined become 793 divisions. In modern terminology our final total of days is stated as 29.530359 days, which is a discrepancy of six-millionths of a day.

Parry, Aaron (2003-03-04). The Complete Idiot's Guide to the Talmud (p. 185). DK Publishing. Kindle Edition. 

This book [Kindle] is beautiful written and anybody interested in Wisdom is advised to have a look at it or consider purchasing it.