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crazy raven
12-08-2008, 06:09
I read there will be two new Moons in August. Could someone explain the significance of this........as it doesn't happen too often!

ravenest
12-08-2008, 13:34
It's just our calendar, isn't it? If we had a lunar calendar like some cultures do, we would always have 1 new moon each month ;)

A lunar calendar will show some 'unusual' features as well, where it tries to slot into the solar cycle.

Minderwiz
12-08-2008, 20:35
That's right. The synodic period of the Moon (time between New Moons) is 29.5 days - the lunar month. From the paleolithic period, as humans began to practice agriculture, there was a need to track the passage of time and the cycles of the Moon are the most easily measured. However, predicting the seasons is also vital for the practice of agriculture. The solar cycle, measured from some cardinal point, such as the Spring or Autumn Equinox or the Summer or Winter Solstice. This period is 365.25 days.

Clearly 29.5 does not divide into 365.25 exactly. There are 12 complete lunar months in a solar year. But this still leaves 11 days short of a full solar cycle. Using 12 lunar months as a measure of a year means that the solar year and the lunar year soon get out of snch. For societies that use a lunar month as the basis of their calendar there can be real problems. In the Islamic calendar the annual (solar year) time of the feast of Ramadan varies throughout the year as a result. One solution is to add additional intercalary months as needed to bring the two cycles back into synch.

Our solar based year has additional days added to the months so that there are still 12 months to the year but not of equal length, some are 30, most are 31 and February has 28, raised to 29 in leap years to allow for the slight difference between the calendar year and the solar year.

This means that in any one calendar year there are usually 12 New Moons but there can be 13 (possibly the reason why 13 was considered an unlucky number because it is not the 'normal' situation). It also means that if the New Moon in any one calendar month falls on the 1st day (first and second for a 31 day month)then there will be a second New Moon that month.

Does this have Astrological significance? From the point of view of natural Astrology, yes it does but not from the point of view of horoscopic Astrology. Eclipses are much more important, so this month is special because of the total eclipse of the Sun on 1st August and the partial eclipse of the Moon on the 16th.