|
|
Re: Why not 13 months? (Was La Systeme Metrique)
Hugh Gibbons (hgibbons@hoshi.Colorado.EDU)
12 Jul 1995 04:46:58 GMT
Whittet (Whittet@shore.net) wrote:
> In article <mls-1107950024110001@mls.dialup.access.net>, mls@panix.com says...
> >
> >In article <3tsqpn$4u4@lace.Colorado.EDU>, hgibbons@hoshi.Colorado.EDU
> >(Hugh Gibbons) wrote:
> >
> >+If you assume that the original definition of the month was based on
> >+the lunar period (full moon to full moon or new moon to new-moon),
> >+twelve would be a closer approximation than 13. (There are
> >+12.37 cycles of the moon per year.)
> >
> >Yes. This is the basis of "cycles" of intercalation of months in luni-
> >solar calendars. To be pedantic, the mean tropical year of 365.24189...
> >days and mean synodic month of 29.05309... days have a ratio of
> >12.36826..., with a minor (over the historical period) secular vari-
> >ation.
> Actually , the actual period of rotation of the moon around the earth
> is closer to 28 days. (27 days, 7 hours, 43 minutes and 11.43 seconds.)
> It is the apparent motion due to the fact that both are moving relative
> to each other which is 29 days 12 hours 44 minutes and 2.78 seconds
> aproximately 29.05309... days . The natural cycles of flora and fauna
> appear to be tuned to the actual rotation however, and not the apparent
> motion. Thus twelve lunar cycles of 28 days work well with a 364 day year.
You both misspelled 29.530588 days.
|