Image credit: interactivestars.com
In 2015 this post discussed long-term lunar precession from an apsidal, or anomalistic, standpoint.
We saw that all the numbers related to an exact number (339) of Metonic cycles (19 tropical years each, as discussed below).
Here we show the equivalent from a nodal, or draconic, standpoint.
Again, all the numbers relate to an exact number (337 this time) of Metonic cycles.
6747 draconic years (DY) = 6403 tropical years (TY) = 344 lunar nodal cycles (LNC)
(6747 – 6403 = 344).
6747 * 346.62008 days = 2,338,645.68
6403 * 365.24219 days = 2,338,645.74
[click on chart to enlarge]
The original chart had anomalistic months (AM); this one has draconic months (DM).
Together these posts put the Metonic cycle at the heart of the long-term harmonics of lunar motion, as related to the Earth.
NB – Wikipedia says:
Nineteen tropical years are about two hours shorter than 235 synodic months. The Metonic cycle’s error is, therefore, one full day every 219 years, or 12.4 parts per million.
19 tropical years = 6,939.602 days (12 × 354-day years + 7 × 384-day years + 3.6 days).
235 synodic months (lunar phases) = 6,939.688 days (Metonic period by definition).
254 sidereal months (lunar orbits) = 6,939.702 days (19 + 235 = 254).
255 draconic months (lunar nodes) = 6,939.1161 days.
The contention here is that there is no ‘error’ in the Metonic cycle – it is 19 tropical years. What happens is that after every 6400 years or so, one synodic month and one tropical month have been ‘lost’ (compared to multiples of 235 and 254 respectively), a type of precession.
via Tallbloke’s Talkshop
August 30, 2019 at 01:54PM
Iowa Climate Science Education 
Reblogged this on Climate- Science.press.
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