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Eclipses:

From our discussion of phases we know that each month there is a time when

1)  The Moon is between the Sun and the Earth:  (at new Moon)
2)  The Earth is between the Sun and the Moon:  (at full Moon)

Whenever the Earth, Sun and Moon are all on a line and the Earth or Moon cast a shadow on the other we call this an Eclipse.

Why don't we see an Eclipse every month?

Because the Moon's orbit is inclined to the Ecliptic (now where did it get that name?).

The missing ingredient is the line of nodes.  Only when the Moon is crossing the Ecliptic at the same time that the Line of Nodes is pointing at the Sun will we have an Eclipse.

1)  Lunar Eclipse:  Moon passes into the Earth's Shadow.

2)   Solar Eclipse:  Earth passes into the Moon's shadow (most people think only of these when discussing Eclipses)

2--5 eclipses (of both types) per year.

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