Why the moon has ascending and descending nodes?

Why the moon has ascending and descending nodes?

The story goes, that the moon was very handsome, attractive and enjoyed its life with 28 constellations. One day, he saw Ganesh and laughed at his appearance, but Ganesh so humiliated cursed the moon that he should be destroyed by tuberculosis. The curse worked immediately with the moon thinner and darker every day. The worried moon went to Shiva who advised him to go and apologise to Ganesh.

Ganesh blessed him for his apology, and said that for only 15 days would he lose his rays, and again would begin to grow bigger and stronger. So now we have the cycle of the moon, growing to full moon and then waning.