This paper describes a method to demonstrate that the plane of the lunar orbit around Earth and the plane of the ecliptic (the plane of Earth’s orbit around the Sun) are inclined with respect to each other, and to present a method for measuring the angle of the inclination. The angle between the diameter of the Moon’s orbit when the Moon passes through the local meridian and the diameter of Earth’s orbit when the Sun passes through the local meridian is the angle between the two planes. The paths of the Sun and the Moon as they appear when the Sun is at the local meridian were defined and the angle between them was measured as 42.5° by an observer. Then, these measurements were used to determine the inclination and to calculate an approximate value for the angle between the plane of the lunar orbit and plane of the ecliptic, which was found to be approximately 4.5°. This angle could be closely approximated with a simple method that everyone could use realistically and provide an answer for the question, “Since there is a full Moon every month as well as a new Moon, why is there no lunar eclipse and solar eclipse every month?”

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J.
Meeus
,
Mathematical Astronomy Morsels
, 1st ed. (
Willmann-Bell
,
Richmond, VA
,
1997
), pp.
11
12
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2.
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