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ScienceSpace Systems & Earth's HistoryAges 11–12

Phases of the Moon

Explain the phases of the Moon as the changing angle of sunlight on the lunar surface as seen from Earth, and describe how solar and lunar eclipses occur

Lesson

Set out your lesson

“The Sun lights half the Moon. As the Moon orbits Earth, we see different amounts of that lit half. Ordinary phases are not made by Earth’s shadow. A full phase cycle takes about 29.5 days, not exactly 28 days. Eclipses require a special alignment because the Moon’s orbit is tilted. Safety: Never view the Sun or an eclipse as part of this task. No bright lamp needed. Stop: Stop at paper geometry; no sky observation or eclipse viewing is required.”

Bring to the table

  • Paper
  • Pencil
  • Eight paper Moon disks
Extra for the adult

Worked example. At full Moon, Earth lies between the Sun direction and Moon direction, so we see the Moon’s sunlit face. Usually the Moon passes above or below Earth’s shadow. Only a close enough alignment gives a lunar eclipse.

Optional challenge. Explain why first quarter looks half lit rather than one-quarter lit.

What to notice. Keep the diagrams. Note adult-supplied phase order or eclipse alignments.

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Selected Default Gakuva

The Sun lights half the Moon. As the Moon orbits Earth, we see different amounts of that lit half. Ordinary phases are not made by Earth’s shadow. A full phase cycle takes about 29.5 days, not exactly 28 days. Eclipses require a special alignment because the Moon’s orbit is tilted. Safety: Never view the Sun or an eclipse as part of this task. No bright lamp needed. Stop: Stop at paper geometry; no sky observation or eclipse viewing is required.

Materials: Paper; Pencil; Eight paper Moon disks 1. Draw Sun at the left and Earth near the page centre. Make a Moon orbit circle around Earth. Draw parallel sunlight arrows left to right. Put eight Moon disks around the circle, starting at Earth’s left and moving anticlockwise. On every disk shade its right half dark: the half away from the Sun. Label diagram not to scale. 2. Below, draw a separate row of eight appearance circles as seen from Earth. Label and mark the lit fraction: new—none; waxing crescent—less than half; first quarter—half; waxing gibbous—more than half; full—all; waning gibbous—more than half; last quarter—half; waning crescent—less than half. No fixed left/right lit orientation is required. 3. Match the row to orbit positions: new left; first quarter below; full right; last quarter above. Put intermediate phases between them. Explain why the orbit disks and appearance row show different viewpoints. 4. Draw two alignment strips: solar eclipse, Sun → Moon → Earth, Moon’s shadow reaches Earth; lunar eclipse, Sun → Earth → Moon, Earth’s shadow reaches Moon. Add: most new and full Moons are not eclipses because the alignment misses. 5. Cover the row labels and narrate a cycle. Contrast one ordinary phase with one eclipse using geometry, not a shadow explanation for all phases. Done: Finish both viewpoints, eight phase names, the cycle duration and two eclipse strips. Proof: Keep the diagrams. Note adult-supplied phase order or eclipse alignments. Stop: Stop at paper geometry; no sky observation or eclipse viewing is required.

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Learning resources

Extra practice links — they do not replace Gakuva’s teaching approach.

NASA Space Place · Practice link — not the full lesson

Moon

Open practice (new tab)
Before you open · source notes

Moon supports Phases of the Moon. An adult previews and guides; this is a learning page, not a scored quiz.

Free educational page, no sign-in required for the tested path.

Before you open

Ask the learner one fact they learned and one question they still have.

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Source, access and review notes

Public NASA Space Place page. An anonymous GET on 2026-11-12 returned HTTP 200 with no login or payment prompt for this URL. Opening the link does not save practice or assess mastery. An adult should preview and guide the learner.

NASA Space Place. “Moon.” External page; Gakuva does not copy, host, embed, or redistribute materials.

Unknown — link only

Check understanding

  • Explains that the phases of the Moon arise from the changing geometry of Sun, Earth, and Moon, not Earth's shadow
  • Describes the sequence of Moon phases over approximately 28 days
  • Distinguishes between a solar eclipse (Moon between Sun and Earth) and a lunar eclipse (Earth between Sun and Moon)
“If your child noticed the Moon looking like a thin crescent one night and a full circle two weeks later, could they explain what has changed and why — and describe what happens during a lunar eclipse?”

Curriculum record

Type
Conceptual
Subject
Science
Domain
Space Systems & Earth's History
Age range
Ages 11–12

Standards

ngss-ms:MS-ESS1-1the-ontario-curriculum-science-and-technology-20:ON-SCI-2022-G6-E2.5uk-nc-2013:KS3.Sci.Phys.SpacePhysics.3