Moon Inquiry: Part 5 – Earth/Moon Orbits and Moon Phases

Introduction:

• Project the video “How Big is the Solar System?” for students to view (to avoid the introduction and conclusion of the video, start at 1:22 and stop at 6:55.
  • After watching the video, rewind and pause it at 3:26 so the video’s model of the Earth and Moon is visible.
• Ask students how the model made yesterday compares to the model in the video.
  • Possible answers may refer to the size of the paper model compared to the push pin and grain of salt used in the video or the smaller distance between objects in the paper model. Depending on students’ familiarity with scale, students may identify that the size of the Moon relative to the Earth is very different in their paper model than the representation in the video.

Lesson:

• Distribute the 2D Sun-Earth-Moon models that were built yesterday to the students.
• Ask students to position the model so that the Moon is directly between the Sun and the Earth (the Moon will be resting on top of the paper that connects the Sun and Earth). It may be easiest to instruct all students to position the Sun on the left side, which means the Earth will be on the right side and the Moon will be in the middle.
• Ask students:
  • Where is the light from the Sun hitting the Moon?
  • What part of the Moon is in darkness?
• Give students a minute or two to discuss with their partner from Part 4.
• Ask a few groups to share their thinking.
  • Students will hopefully recognize that the Sun’s rays hit the side of the Moon that is facing away from the Earth. The dark side of the Moon is therefore facing the Earth (new moon). 
• Ask students: Based on our conclusion, what would the Moon look like from Earth if you were looking up at the sky?
  • Students try to take the perspective of someone on Earth looking up and imagine what they will see. They should recognize the Moon will not be visible because there is no light hitting the side that is facing Earth. 
• Ask students to re-position the model so the Sun is on the left and the Moon is immediately below the Earth. The model will look like an upside-down capital letter “L.”
• Repeat the prompts from above: Where is the light from the Sun hitting the Moon? What part of the Moon is in darkness?
• After students have studied the new positions and come to a conclusion, ask a few different pairs to share and defend their answers. 
  • Ask students: Based on our conclusion, what would the Moon look like now if you were looking up at the sky from Earth?
• Now ask students to re-position the model so that the Sun remains on the left, and the Moon is now immediately above the Earth. The model will look like a capital letter “L.”
  • Again, repeat the prompts from above, and lead a brief discussion about where the light from the Sun hits the Moon, and how the Moon appears from Earth.
• Finally, ask students to re-position the model so the Sun remains on the left, the Earth is in the middle and the Moon is on the right. 
  • Repeat the prompts and discussion points from above.
  • This position may be the most difficult for students to assess because the scale and design of the model may prompt some students to wonder why the Earth does not block all sunlight from reaching the Moon (this is why it is the last position in the activity). If this happens, project the “Lunar Eclipse 101” video for them to view.
    • Lunar eclipses (when the Earth either fully or partially blocks the light of the Sun from reaching the Moon) don’t happen every month because the Moon’s orbit around the Earth is tilted – that is, the Moon’s orbit around the Earth is not on the same plane as the Earth’s orbit around the Sun. The 2D model, because it is flat, misrepresents the movement of the Moon around the Earth.
    • If students continue to struggle with the concept, project the “How Big is the Solar System?” video for them one more time, pausing at 3:26. Allow students to consider how small the Earth and Moon are relative to the Sun, as well as how far the Moon is from the Earth, how far both the Earth and Moon are from the Sun, and how light traveling over such vast distances would interact with such tiny objects in space.

Conclusion:

• To conclude the day, project the Lunar Phase Simulator on the whiteboard.
  • The simulator is a digital version of the activity they just completed and will reinforce the ideas students are experimenting with.
• Slowing the speed of the simulator down allows students to more easily observe the details of the model. It is also helpful to check the box that reads “show time tickmarks” in the Diagram Options section.
• As the simulator runs, focus students’ attention to:
  • The Moon and how sunlight is hitting its surface differently in different parts of the lunar cycle
  • The person “standing” on Earth, and what they might be seeing as the Earth rotates on its axis
  • The Horizon Diagram in the lower right corner where they can see how closely together the Sun and Moon travel in the sky (from Earth’s perspective) at different points in the lunar cycle
  • The Moon Phase in the upper right corner where they will see how the Moon’s appearance changes throughout the lunar cycle – and hopefully recognize when it looks like the drawings they have been making!