Liberal Arts Blog —Phases of the Moon: Oreo Cookies, A Clock, Two Thumbs, and “D-O-C”

Liberal Arts Blog — Wednesday is the Joy of Science, Engineering, and Technology Day

Today’s Topic — Phases of the Moon: Oreo Cookies, A Clock, Two Thumbs, and “D-O-C”

It’s a half moon out. How long before the next full moon? Think about it before reading on. Do you have an answer? What is your confidence level? My experience is that less 1% of Harvard science majors get the answer correct. But most are extremely confident in their solutions. Today’s post is devoted to using oreo cookies, the clock analogy (thank you, Leon), and the D-O-C mnemonic to teach about the phases of the moon. Experts — please chime in. Correct, elaborate, elucidate.


1. “I’ve always been a fan of science activities that you can eat. One of my favorites is the Oreo Cookie Moon Phases activity. It’s almost as if Oreo cookies were made for this lesson, and it’s a great way to learn how to match a moon phase name with a moon phase appearance.”

2. Needed: An Oreo cookie for each moon phase, a popsicle stick or other tool for scraping the frosting.

3. “Separating Oreo cookies while keeping the frosting intact is a fun challenge. I like to slowly twist the Oreo to maximize the amount of frosting on one side, Cooling the cookies in the refrigerator can make it easier…You can always transfer frosting if needed.”

THE WALL CLOCK ANALOGY: if it’s a full moon at 12, what does the moon look like at 6?

1. What does it look like at 3?

2. What does it look like at 9?

3. Why?

NB — Now turn a paper plate into a clock and place the appropriate oreo cookie in the appropriate location. See second link.


1. “The most common mnemonic used to remember the phases of the moon is “DOC,” which switches to “COD” if you are in the southern hemisphere.”

2. The “D” is curved to the right and is a waxing moon. That would be the moon at 9 in above analogy. The “O” is the full moon at 12, The”C” is the waning moon at 3.

3. Align your two thumbs facing each other — your left thumb is the “D” (waxing at 9), your right thumb is the “C” (waning at 3). See last link.

Oreo Cookie Moon Phases —

Oreo Moon Phases Activity

Oreo Moon Phases — The Stem Laboratory

9 Strategies For Teaching Moon Phases

A link to the last three years of posts organized by theme:

PDF with headlines — Google Drive


Please share the coolest thing you learned this week related to science, engineering, or technology. Or, even better, the coolest or most important thing you learned in your life related to science and engineering.

This is your chance to make someone else’s day. Or to cement in your mind something that you might otherwise forget. Or to think more deeply about something dear to your heart. Continuity is key to depth of thought.

Passionate about education, thinking citizenship, and art.