Expert: Harry Hayfield - 2/8/2010

Question
Is it correct and/or is there a better way of saying the following?
For an eclipse to occur the Sun, Moon and Earth have to line up in the same plane. This can only happen when the Moon is full or new and when the Moon passes through the ecliptic. Because the Moon's orbit is inclined 5 degrees to the Earth's, it spends most of its time below or above the plane of the Earth and the ecliptic.
(ecliptic linked to: http://www.souledout.org/nightsky/nsglossary.html#ecliptic)

I had posted this online and received this response:
The very first paragraph of this article has a passage which is a little misleading:  For an eclipse to occur the Sun, Moon and Earth have to line up in the same plane.   By definition, three points define a plane.  The sun Earth and Moon are always in the same plane.  The article almost implies they are not.

Thanks for any clarity you can offer. I'd like to make a correction if needed.
Susan Sun
p.s. If needed the entire article can be seen here:
http://www.souledout.org/nightsky/eclipsefrequency/eclipsefrequency.html

Answer
For an eclipse to occur the Sun, Moon and Earth have to line up in the same plane.

Correct

This can only happen when the Moon is full or new and when the Moon passes through the ecliptic.

Correct (Full for a Lunar Eclipse, New for a Solar Eclipse)

Because the Moon's orbit is inclined 5 degrees to the Earth's, it spends most of its time below or above the plane of the Earth and the ecliptic.

Correct