Lunar Nodes
For the orbit of the Moon around the Earth, the reference plane is taken to be the ecliptic, not the equatorial plane. The gravitational pull of the Sun upon the Moon causes its nodes, called the lunar nodes, to precess gradually westward, performing a complete circle in approximately 18.6 years.
Read more about this topic: Orbital Node
Famous quotes containing the words lunar and/or nodes:
“A bird half wakened in the lunar noon
Sang halfway through its little inborn tune.”
—Robert Frost (1874–1963)
“There are characters which are continually creating collisions and nodes for themselves in dramas which nobody is prepared to act with them. Their susceptibilities will clash against objects that remain innocently quiet.”
—George Eliot [Mary Ann (or Marian)