Phases of the Moon Exercise

In this exercise, you will investigate the cause of the phases of the Moon. The figure below shows an orbital diagram of the Earth-Moon system as viewed from above the Earth's north pole. Light from the Sun is coming from the left. Note that the drawing is not to scale.

Section I

Shade in the part of the Moon that is in shadow and the part that is unobservable from Earth in each of the eight numbered positions. The first has been completed as an example. (Use dark shading for the shadow, light cross-hatch for the unobservable side.)

[Phases of the Moon Diagram]

Section II

Record the phase and appearance of the Moon in Table 1 for each of the eight positions in the diagram. (Again, the first has been done as an example.) Also determine the Moon's elongation. Note that if you know the Moon's elongation, you know its phase, and vice versa.

Position 1 Position 2 Position 3 Position 4


Position 5 Position 6 Position 7 Position 8

Section III

Use the diagram to fill in the missing data.

Phase of Moon Time of Day Moon's Position in Sky
  00:00 (midnight) rising in the East
waning crescent   15° above Western horizon
waxing gibbous 20:00  
  12:00 (noon) directly overhead

Last updated: Wed Jan 19 11:11:35 EST 2000