Answer:

• The orbital plane of the Moon is not in the ecliptic plane. The orbital plane of the Moon is inclined 5 degrees or so with respect to the ecliptic plane. This has the following consequence. If new (or full) Moon occurs when the Moon is not passing through the ecliptic plane then the shadow formed will not strike the Earth (Moon).

• The points where the Moon passes through the ecliptic plane are referred to as nodes. If we draw a line through the nodes, we define what is called the line of nodes. Eclipses will occur only when the line of nodes points roughly toward the Sun. The direction in which the line of nodes points is roughly fixed, i.e.,

  

  which means that the line of nodes will point toward the Sun every 6 months or so. (Actually the period is shorter than 6 months--the eclipse year is 346.6 days long. What does this imply about the line of nodes?)

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