Briahna Weiss
Earth Science 110
Phases of the Moon
Have you ever wondered what causes the moon phases? We all know that its appearance changes
over time. But why? The good way to understand the phases of the moon is to examine an earthmoon-sun diagram:
Materials:


Each pair of students will receive 7 Oreo cookies
Plastic Butter Knife
Procedure:
1. Each pair of students will receive seven Oreo cookies and an EarthMoon-Sun Diagram.
2. Separate your cookies carefully, so one ½ has all the frosting, and the
other ½ has no frosting. See Figure 1:
3. Use your plastic butter knife to scrape off the frosting from the first
cookie making a shape with the frosting that resembles the cookie in Figure 2:
4. Repeat step 3 with the other cookies scraping the frosting of the other 6 phases
as seen by Earth. You will need to create waxing and waning phases.
5. The Earth-Moon-Sun Diagram represents the Moon in its orbit around the Earth, as viewed
from the Earth’s North Pole. Position 1 on the diagram represents a certain location of the
Moon in its orbit. On Diagram B, place the cookie moons you created in their proper locations
starting from Position 1 working counterclockwise according to the order on the Earth-MoonSun Diagram.
6. On Diagram B, label each of the phases in order from position 1to the final phase on the EarthMoon-Sun Diagram.
DIAGRAM B – How Earthlings view the Moon (place your cookie moons here).
Position
___________
_____________
____________
_____________
Position 3
Position 4
Position 1
Position 2
__________
____________
_____________
Position 5
Position 6
Position 7
____________
Position 8
Follow-Up Questions:
2. Describe the process that causes the moon to appear as these different phases to Earth.
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
3. How long is one cycle of phases?
____________________________________________________________
4. What is the average time (in days) between phases?
____________________________________________________________
5. The small, white circle on each of the moons in the Earth-Moon-Sun Diagram represents the
impact crater “Tycho”. Formed only 108mya it is one of the youngest craters on the moon. It was
named after the famous astronomer Tycho Brahe. Explain why this crater is always facing the Earth.
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
____________________________________________________________
6. What is the greatest number of full-Moon phases visible from Earth that are possible in the span
of one year?
____________________________________________________________
7. Referring to Earth-Moon-Sun Diagram, an observer on Earth would see a solar eclipse when the
moon is at
Position _______, Lunar eclipse position? ________.
What We Learned:
We learned how to use the Earth-Moon-Sun diagram to figure out what phases the moon would be at
in each position on the diagram. We learned the process that causes the moon to appear as the
different phases. We learned how long one cycle of phases is and the average time between phases.
We also learned about the “Tycho” crater and how many full moon phases we can see in one year.
Similar Experiments:
Basketball Moon Phases