The Moon’s Phases and the Self Shadow by: Timothy Young and Mark Guy

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In this article, the authors present a new way of teaching the phases of the Moon. Through the introduction of a self shadow (an idea of a shadow that is not well-known), they illuminate students’ understanding of the phases of the Moon and help them understand the distinction between the shadows that cause eclipses and the shadows that relate to the phases of the Moon. Then, they follow with two easy-to-do demonstrations that help students further develop their understanding of the reasons behind the patterns of lightness and darkness in the Moon’s phases.

  • Elementary
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Reviews (9)
  • on Thu Jun 14, 2018 9:45 AM

The Figure 1 photo was eye-opening to me, as I realized I'd never fully grasped the relationship between a cast shadow and a self shadow. The concept of a self shadow can help clear up a student misconception that the phases of the moon are caused by the Earth's shadow. I also appreciated the activities that reinforced this concept! This was a great read.

Anna Powell
Anna Powell

  • on Tue Nov 29, 2016 9:41 PM

I love how this article not only explains the phases of the moon, but also highlights some of the common misconceptions students have when learning to make sense of them. It also provides teachers with clear models to use to demonstrate why the amount of light on the surface of the moon seems to grow and shrink. Additionally, the author provides an assessment rubric that is easy for teachers to use. Overall, an article worth reading!

Hilary P
Hilary P

  • on Wed Mar 20, 2013 9:26 AM

This article describes the phases of the moon as a self shadow. "A self shadow is a shadow on the object blocking the light. It forms on the opposite side of the light source." This is a novel way to explain moon phases caused by the sun. It also clears up the misconception that moon phases are the earth's shadow. The article continues with some activities to further explain the phases of the moon.

Betty Paulsell  (Kansas City, MO)
Betty Paulsell (Kansas City, MO)

  • on Fri Oct 12, 2012 11:55 AM

This article proposes a ‘new’ approach to teaching about the moon phases. This approach is different and involves views of the moon (Moon Ring) from outside of space and not just from Earth. The article provides the reader with how to carry out the activity (including materials) as well as a complete rubric for assessing students with both activities Moon Ring and Glow Moon. Before passing judgment about the effectiveness of these activities one needs to try it out in the classroom first.

Adah  (San Antonio, TX)
Adah (San Antonio, TX)

  • on Wed Apr 13, 2011 2:09 PM

This article gives several activities that can be done to teach about the phases of the moon, starting with one commonly held misconception, that the phases are caused by cast shadows rather than self-shadows. Overall there are a few really powerful activities that could be used to teach the basics of the moon phases if supplemented with good assessment along the way.

Wendy  (Pocatello, ID)
Wendy (Pocatello, ID)

  • on Sun Mar 27, 2011 5:07 PM

The first activities in this article about self-shadows provide important experiences for students learning about moon phases who may believe that the phases are caused by cast shadows. The additional activities further enhance the teaching of this concept but most teachers may have to be selective about how many and for which activities their curriculum will allow time. As a whole though this article outlines a complete unit about phases of the moon that addresses many of the common misconceptions about the subject.

Bambi Bailey  (Tyler, TX)
Bambi Bailey (Tyler, TX)

  • on Thu Jun 14, 2018 12:16 AM

Professor Young and Professor Guy have composed a well-organized, practical, interactive, and concise article regarding teaching the Moon phases. They propose a novel method to instruct the phases of the Moon, notably via a “self shadow,” in which learners’ comprehension of the Moon’s phases is informed by the difference between shadows that produce eclipses, and shadows that pertain to Moon phases. They explain that a “self shadow” (a shadow on an object) obstructs the light, forming on the light source’s opposite side — the self shadow is literally connected to the object impeding the light; this, in contrast to a “cast shadow,” which is distinct from an object. Young and Guy describe how self shadows can be recognized in the classroom “by turning on a bright light source and making the distinction between the cast shadow that is responsible for causing the eclipses and identifying the shadow on the surface of the object as the self shadow and responsible for causing the phases.” Therefore, the phases (conceptually) are detached from an eclipse. These professors understand and focus upon their audience deftly — teachers in grades 5-8 — by conveying their methodology in ways relevant to elementary teachers actually practicing their craft in the field. For instance, they convey two straightforward “demonstrations” that assist students apprehend the “patterns of lightness and darkness in the Moon’s phases.” I appreciate that the authors structure these demonstrations succinctly, suggesting a simple objective, teacher preparation, exploration, discussion, and assessment. They also include five “figures” (a photo, a worksheet, a diagram, a moon ring view, and an assessment rubric). . . all are uncomplicated and simplified; in fact, 5th graders (and up) could competently ascertain the information contained therein. I also appreciate the humor that the authors intersperse throughout the article. This is not an academic discourse, rather, it’s a pragmatic approach that enhances student learning of a too frequently complex scientific topic. This article also address standards, however, the citation stems from NRC (1996). If plausible, I’d suggest that Young and Guy revisit this article and update it for Common Core (2018). Additionally, it would be wonderful for the authors to adapt this strategy for K – 2 children as well. Kudos to the authors. I concur that their approach simplifies this curriculum while helping young learners heighten their scientific thinking through hands-on learning, especially by comparing day-to-day objects and their two shadows.

Joshua Click
Joshua Click

  • on Wed Jun 13, 2018 9:13 AM

I thought that the concept of a self shadow was a really helpful way to think about the moon's phases for both students and adults! Both of the demonstrations in this article seem engaging and well-prepared as far as their ability to address misconceptions about the moon's phases.

Anna-Marie S
Anna-Marie S

  • on Thu Jul 28, 2011 8:33 PM

The article introduces and defines two different kinds of shadows, cast and self. The authors use excellent examples, helping students understand the phases of the moon in a different way. I shared these concepts with my middle school students. It took them a little while, but once they began to understand, they were able to explain how the phases occur with a lot more confidence, and were able to explain how the Sun – Earth – Moon models worked. Within the article, the authors shared how they used a “glow moon model”, which is pretty similar to investigations included in most kit programs.

Sandra Gady  (Renton, WA)
Sandra Gady (Renton, WA)

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