# Why is the Lunar Node in a daily motion?

I've read a lot about the Lunar Nodes online (on Wikipedia, astro.com and a bunch of other websites), but there is one thing I cannot figure out and the sources don't seem to clearly explain: why are the nodes moving on a daily basis? As the node is a point of intersection of Moon's orbit and the Ecliptic I understand that this point does not fall in the same place in space every time, but I would expect that once it's passed by the Moon it stays where the crossing occurred and its position gets updated on the next crossing of the Ecliptic, so in ephemeris I would expect to see the same values of the coords between the crossings, but instead I can see they're changing on the daily basis (ie. this ephemeris has 2 columns showing true and mean nodes' positions: http://www.astro.com/swisseph/ae/2000/ae_2016.pdf). I'm sure the ephemeris cannot be wrong, so I must be missing some details. I thought that finding the Moon's nodes would be as easy as finding the dates/times/longitudes when the Moon's latitude equals 0, but apparently this way I can only find the times and static points of the crossings of the Ecliptic, not the moving nodes as they're shown in ephemeris tables.

• pyephem knows ascending node. m=ephem.Moon();m.compute('2016/9/1');print(m._raan) – James K Aug 27 '16 at 7:09