# The lunar month and gestation

Fri May 30 00:49:46 UTC 1997

At 05:51 PM 5/27/97 BST, Jonathan Silk wrote:
>>Dominique wrote:
>>
>>        P.S. 1: I don't believe human gestation has anything to do with 9:
>>273 (statistical duration) : 29.5 (lunar month) = 9.25 and this 0.25 is too
>>great (birth's moon and conception's mood are not the same!). More: I don't
>>know how Indians counted the durations before Indian mathematicians, but in
>>ancient Greece where the Olympic Games were 'pentaeterikoi' (each 'five'
>>years), human gestation was 10 months.
>
>
>I confess that I am entirely ignorant of mathematics, and I don't
>understand the first half of this paragraph, but: there is considerable
>information available about old Indian ideas of embryology and gestation.
>One interesting fact -- I think it is a fact, and I plan to write about it
>in the context of a study of the Buddhist text Garbaavakraanti-suutra -- is
>that discussion of gestation in terms of *weeks* in this text, which almost
>certainly comes from the Northwest, and probably belongs to the
>Muulasarvaastivaadins, appears to show Greek influence.  Unfortunately this
>text is not extant in Skt, only Chinese and Tibetan, but probably the word
>for week is saptaka.  The progress through the various embryonic stages is
>denoted by weeks, and the total gestational period is, if memory serves (I
>don't have the text at hand) 38 weeks.

The average duration of pregnancy is about 280 days, or 40 weeks of 7 days.
The sidereal lunar month currently lasts 27 days 17 hrs. 43 min.  Ten of
these months equal about 280 days.  So when old texts talk of a gestation
period of 10 months they are, most likely, referring to these 10 sidereal
lunar months.

The sidereal lunar month is the time it takes the Moon to go once around the
Zodiac and return to the same place with respect to the stars.  In other
words, the time elapsed since the Moon is in conjunction with a certain star
until it reaches the same star again.

The synodic lunar month, on the other hand, is the time elapsed from new
Moon to new Moon, or from full Moon to full Moon.  Put differently, it is
the time between two consecutive conjunctions of the Sun and the Moon (in
the case of the new Moon to new Moon scenario).  It is longer than the
sidereal month because by the time Moon goes around the Zodiac, the Sun has
also advanced slightly, and the Moon must catch up.
The current duration of the synodic lunar month is 29 days 12 hrs. 44 min.

I remember having read about a ten month gestation period in the
KathAsaritsAgara, but I don't have access to the reference at the moment.
I'm sure there are many more, probably in Buddhist texts.

Both lunar months were used in ancient India.  The synodic lunar month was
divided into 30 so-called lunar days, the tithis.  And the sidereal month is
the one that defines the nakSatras, the lunar constellations of the Zodiac
(as opposed to the solar constellations, the rA'sis).

Best,

Luis Gonzalez-Reimann
University of California, Berkeley