NAAP – Lunar Phase Simulator 1/11
Lunar Phase Simulator – Student Guide
Part I: Background Material
Answer the following questions after reviewing the background pages for the simulator.
Page 1 – Introduction to Moon Phases
Is there a dark side of the moon? (Note: this question can be effectively answered either
yes or no, so it is important to explain your reasoning.)
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These are the points the moon was at
when the sketches above were drawn. Identify each position with the letter of the
Page 3 – The Time of Day
NAAP – Lunar Phase Simulator 3/11
Use the interactive diagram at the bottom of the page to determine the direction of the
earth’s rotation when viewed from above the North Pole. (Hint: rotate the observer – the
stickfigure – to the noontime position, then sunset position, then midnight position, and
finally back to sunrise position. The earth has made one complete rotation and the
observer has experience one daily (diurnal) cycle of day and night.)
When viewed from above the North Pole, does the earth rotate clockwise or
Page 4 – Rising and Setting
When the moon crosses the western side of the horizon plane it is rising / setting
(circle). When it crosses the eastern side of the horizon plane it is rising / setting (circle).
Page 5 – The Horizon Diagram
Describe the location of the moon in the sky of the horizon diagram at bottom.
Use direction words (like north, west, etc.) and estimate its altitude in degrees.
Page 6 – The Witness and the Detective
If we know the moon's position in the sky and its phase, we can estimate the
____________. In general, knowing any two of the following three things allows us to
estimate the third:
1. moon's position in the sky
NAAP – Lunar Phase Simulator 4/11
Part II: Visualizing Phases
Question 1: We can determine the appearance of the moon based on the orientation of the
moon and sun with a simple heuristic. In the figure below, bisect the moon twice.
a) Draw a line (perpendicular to the direction of sunlight) that shows the half of the
entire moon that is illuminated and shade the shadowed region.
b) Draw a line (perpendicular to the Earth-moon line) that shows the half of the
moon visible for an observer on earth.
c) Mark the region that is both visible from earth and illuminated by the sun. That
region will be the phase of the moon we on earth see.
We normally draw the phases of the moon with the terminator (the dividing line
between light and shadow) from the north pole to the south pole of the moon. This is
how the moon would be seen if it were on the observer’s meridian. We can use the
drawing above to determine the amount of illumination and whether it is on the left or
right hand side of the moon. Use the drawing above to draw the appearance of the moon
in the box below.
Open the Moon Bisector Demo and use the simulator to check your answer to the above
NAAP – Lunar Phase Simulator 5/11
Part III: Working with the Lunar Phase Simulator
The items below will help familiarize yourself with the controls...