Science // Space Exploration

The Moon's Orbit

Know that the Moon orbits Earth approximately once a month, that it does not make its own light but reflects sunlight, and that its changing appearance (phases) is caused by how much of the sunlit side we can see from Earth

Ages
7 to 9
Type
Concept
Builds on
2 topics
Leads to
0 topics

Quick check

Can the learner explain why the Moon seems to change shape — that it’s always round but we only see the part lit up by the Sun?

Ask this to see whether the topic is secure.

Topic // Mastery

What mastery looks like

What a learner can do once this topic is secure.
  • State that the Moon orbits Earth roughly once every 28-30 days
  • Explain that the Moon reflects sunlight rather than producing its own light
  • Describe how Moon phases happen: we see different amounts of the lit-up side as the Moon orbits Earth

Topic // Map

Where this fits

What to learn first and what this topic opens up, with the reason for each link. Required links come first.
  • RequiredMust come first
  • HelpfulHelps, but not essential

Before this

2 topics
  • Moon PhasesRequired

    Space Exploration // Ages 5 to 7

    Must have observed Moon phases before learning the causal explanation (reflected sunlight)

  • Earth's Spin & OrbitHelpful

    Space Exploration // Ages 7 to 9

    Understanding orbits helps contextualise the Moon's orbit around Earth

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The Moon's Orbit

Ages 7 to 9 // Concept

Leads to

0 topics

Nothing in the catalogue builds on this topic yet. Browse Space Exploration

Topic // Research-informed

Teaching notes

From the Marble Skill Taxonomy. These notes have not been validated in classrooms, so treat them as a starting point for your own judgement.

The approach

Teaches the causal explanation of Moon phases for ages 7-9: the Moon orbits Earth about once a month, makes no light of its own but reflects sunlight (so one half is always lit by the Sun), and the phases we see are caused by how much of that lit half faces us from Earth as the Moon moves around us. The central, hard idea is that phases are a viewing-angle effect, NOT the Earth's shadow falling on the Moon (that rarer event is a lunar eclipse). The canonical activity is a lit ball (Moon) orbiting the child's head (Earth) under a single lamp (Sun) so the child watches the lit fraction change from their own vantage point; screen models and a reference diagram support and extend this.

Common misconceptions

  • Believing phases are caused by the Earth's shadow falling on the Moon (the single most common and persistent error) — rather than by our changing view of the lit half.
  • Thinking the Moon produces its own light, rather than reflecting the Sun's.
  • Believing clouds, or an object passing in front, cover the Moon to make the phases.
  • Thinking only part of the Moon is lit at any time (not realising a full hemisphere is always lit; what changes is our viewing angle).
  • Confusing the ordinary monthly phase cycle with a lunar eclipse (which IS Earth's shadow, but rare) — merging two different phenomena.
  • Assuming the Moon is only visible at night, or that a new moon means the Moon has 'gone away'.

Useful representations

  • Ball (Moon) + single lamp (Sun) + child's head (Earth) — the canonical phases model seen from the child's own viewpoint
  • Half-lit sphere: the Sun always lights exactly one hemisphere of the Moon (fixed toward the Sun)
  • Coupled dual view: overhead space view of the Moon at 8 orbit positions PLUS the matching Earth-view shape for each position
  • Phase wheel / strip: new → waxing crescent → first quarter → waxing gibbous → full → waning … mapped around the orbit
  • The terminator on the Moon (the line between its lit and unlit halves) as the boundary we see cutting across the disc

Teaching practices

  • Use the classic ball-and-lamp model: a single lamp (Sun) lights one half of a ball (Moon) at all times; the child holds the ball at arm's length and slowly turns around, watching how much of the lit half faces them — reproducing new, crescent, half, gibbous, full from their own point of view.
  • Make the reflected-light idea explicit and testable first: half the Moon is ALWAYS lit by the Sun; what changes is only how much of that lit half we see — not how much is lit.
  • Directly confront the Earth's-shadow misconception: show that in most phases the Earth is not between the Sun and Moon at all, so its shadow is not on the Moon; reserve Earth's shadow for the separate rarer event (a lunar eclipse), which is NOT the cause of ordinary phases.
  • Link the phase cycle to the orbit period the child already met: one trip of the Moon around Earth ≈ one month ≈ one full phase cycle, connecting motion to appearance.
  • Couple the space view (Moon orbiting Earth, lit half fixed toward the Sun) with the Earth view (what the Moon looks like tonight) so the child maps position-in-orbit to shape-in-the-sky.

Activities to try

  1. 1

    Ball-and-lamp: orbit the Moon around your own head

    Why it works: Phases are caused by our changing view of the always-half-lit Moon as it orbits, not by anything covering or shadowing it.

    1. In a darkened room, shine a single lamp (the Sun) on a ball (the Moon); notice one half of the ball is always bright and the other half dark.
    2. Hold the ball at arm's length and slightly above head height (so your own shadow does not fall on it), stand with your head as Earth, and slowly turn all the way around so the ball orbits your head.
    3. As you turn, watch how much of the bright half you can see and name the views you pass through: all of it (full), half the disc lit (quarter), a thin sliver (crescent), or none at all (new) — these appear at different points as you rotate, not only at the quarter-turns.
    4. Say aloud for one position: 'The Moon is still fully half-lit by the lamp — I am just seeing more / less of the bright side from here.'
    5. Point to where the dark side is pointing when you see a crescent, to confirm nothing is covering the Moon.
  2. 2

    Does the Moon make its own light?

    Why it works: The Moon produces no light of its own; it shines only by reflecting the Sun's light, so with no Sun there is nothing to see.

    1. Put the ball where you can see its bright and dark halves.
    2. Predict what happens to the ball if the lamp is switched off.
    3. Switch off the lamp and observe: the ball goes dark, or only stays dimly visible from any other light leaking into the room, because it makes no light of its own.
    4. Explain in a sentence where the Moon's glow comes from, using the word 'reflect'.
  3. 3

    Where is Earth's shadow really? Separating phases from eclipses

    Why it works: In ordinary phases Earth's shadow does not touch the Moon, so phases cannot be caused by it; Earth's shadow on the Moon is a separate, rare event (a lunar eclipse).

    1. For an ordinary crescent or half phase, work out where the Sun is, where the Moon is, and where Earth's shadow would stretch (straight away from the Sun).
    2. Check whether Earth's shadow actually falls on the Moon in that position — in ordinary phases it points off into empty space, nowhere near the Moon.
    3. Describe the special, rare line-up when Earth is EXACTLY in line between the Sun and the full Moon, so the shadow does reach the Moon — name this a lunar eclipse.
    4. Write one sentence stating what causes ordinary phases and one sentence stating what causes a lunar eclipse, keeping them separate.

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