Torsten:
> How would you correlate 3 groups with the appearance of the moon?
Exactly. Everybody knows that the length of a lunar cycle from new
moon to new moon is approximately 7*4 days long. It's easier for
people to use integers rather than fractions and we see that we
can get nice even numbers that approximate the cycle in this way.
We can do this for any cycle. The yearly cycle is approximately
365 days long. That can be divided up with integers too. In fact,
we use the same integer 7. We all know that there are 52 weeks in
a year. So 52*7 days approximates the year nicely and by using the
same integer as the lunar cycle ("7"). Now 52*7 is really 13*4*7 and
since we see that 4*7 is a month, we might choose to seperate the year
by 13 months -- note 13*(4*7).
= gLeN