Lesson 08 — Earth, Moon, and Sun: Day Length and Moon Phases

Learners describe the Earth–Moon–Sun system: Earth's spin makes day and night (about 24 hours), and the Moon's orbit around Earth makes the phases, because we see different parts of the Moon's sunlit half as it travels. They model the system and predict the Moon's changing shape.

D06 P3: Intellectual & Cognitive Awareness D06.S4 55 minutes Draft

Objectives

D06.S4.05.01 Describe the Earth, Moon, and Sun system and explain day length, moon phases, and eclipses.

Essential question

Why do we have day and night, and why does the Moon change shape in the sky?

rotateorbitaxisdaynightmoon phasenew moonfull mooncrescentreflect

Materials

Standard materials

Earth–Moon–Sun diagram · 1 per pair The graphic showing Earth's spin, the Moon's orbit, and the eight phases
A ball (Earth) and a smaller ball (Moon) and a lamp or torch (Sun) · 1 set per group To model the Moon's orbit and watch the lit shape change
Moon-phase observation chart · 1 per learner A page to sketch the Moon's shape on several nights

Low-tech / no-cost

A ball, a smaller stone, and the Sun itself Hold the stone (Moon) out toward the Sun and turn; watch its lit shape change from your eyes
Voice and body One learner is the Sun (holds arms out), one the Earth (spins), one the Moon (walks around Earth, always facing the Sun); no objects needed

Enriched / lab & device

A short Moon-phase animation or a Moon-phase app · 1 per group To replay the orbit and watch the lit shape change over a month
A lunar calendar from a real tradition · 1 per group To connect the phases to how people have kept time by the Moon

Works in different contexts

large-group Model the Earth–Moon–Sun with three learners at the front while the group predicts the phase before each position is revealed
multi-age Younger learners act out day/night (spin) and point to "big light / no light"; older learners name all eight phases and explain why the lit half always faces the Sun
self-directed A learner studies the diagram, models the orbit with a ball and lamp if available, and sketches the phase they would see from each position
level-grouped Learners ready to extend explain why a full moon rises at sunset and a new moon is near the Sun in the sky, using the model
outdoor-only Hold a small ball (Moon) out toward the Sun and turn slowly; watch its lit shape change exactly as the real Moon's does

An Earth–Moon–Sun diagram. On the left, a large circle labeled Sun sends light rays to the right. In the center, a circle labeled Earth shows a lit day side and a dark night side, with an arrow showing it spins once in about 24 hours. Around the Earth, a dashed circle shows the Moon's orbit, with eight Moon positions spaced around it. Each Moon is half lit on the side facing the Sun, and each position is labeled with the phase seen from Earth: new moon, waxing crescent, first quarter, waxing gibbous, full moon, waning gibbous, last quarter, and waning crescent. Labels and shapes, not color alone, carry the meaning so it prints clearly in grayscale.

Lesson 8 — Earth, Moon, and Sun: Day Length and Moon Phases

Summary

Learners explain two movements of the Earth–Moon–Sun system: Earth rotates (spins) once in about 24 hours, making day and night; and the Moon orbits Earth about once a month, making the phases — because we always see only part of the Moon’s sunlit half. They model both movements and predict the Moon’s shape from where it stands.

Objectives

Describe the Earth, Moon, and Sun system, and explain day length and moon phases. (D06.S4.05.01)

Connection

Every evening, if you look up, the Moon may look different from the night before — a thin crescent, a half-circle, a full round face — then it thins again. People all over the world have kept time by this cycle: many calendars, from the Islamic calendar that sets the month of Ramadan to the lunar calendars that set many New Year festivals across Asia, follow the Moon. And every morning the Sun comes up because our own Earth is turning. Today you learn the two motions that make the day and the month.

Materials

Earth–Moon–Sun diagram
A ball (Earth), a smaller ball (Moon), and a lamp or torch (Sun)
Moon-phase observation chart

Preparation

Print or draw the Earth–Moon–Sun diagram and a moon chart per learner.
Set up one lamp (Sun) per group, or arrange to use the real Sun outdoors.
Recall Grade 3: Earth’s rotation makes day and night; its orbit makes the seasons.

Facilitator note

Written to the learner (“you”). Two movements, two effects: rotation → day and night (~24 hours, so “day length” is about one full turn); the Moon’s orbit → phases. The key insight to land is that the Moon does not make its own light — it reflects the Sun’s light, and its lit half always faces the Sun. The phases are just our changing view of that lit half, not Earth’s shadow on the Moon (that misconception is exactly what the next lesson, eclipses, corrects — preview it). The ball-and-lamp model is the worked example: model one full orbit slowly, and have learners predict the phase before you reveal each position. This honors the predict → test → observe loop. Keep the lunar-calendar mention respectful and factual: many cultures use lunar calendars, and none is “better” — that is a value we hold (docs/facilitation.md).

Procedure

Gather (5 min). Think of the last time you saw the Moon. What shape was it? Why do you think it changes? Say your guess — that is a prediction.
Meet the two motions (10 min). Look at the diagram. Earth rotates (spins) on its axis once in about 24 hours — that is one day and night, so our day length is about 24 hours. The Moon orbits Earth about once every 29–30 days. The Moon makes no light of its own; it reflects the Sun’s light, so its lit half always faces the Sun.
Why phases happen (10 min). As the Moon travels around Earth, we see different parts of its lit half: new moon (lit half faces away — we see none), waxing crescent, first quarter, waxing gibbous, full moon (we see the whole lit half), then waning gibbous, last quarter, and waning crescent. The Moon itself does not change — our view of it does.
Model it (15 min). With a lamp (the Sun) and a ball (the Moon), stand where Earth is and move the Moon slowly around you, always keeping its lit side toward the lamp. At each position, predict what shape you will see, then look. Record it on your chart. Compare with the diagram.
Close (5 min). One turning Earth gives you a day; one orbiting Moon gives you a month of changing faces. Both are just motion — spin and orbit — and both are happening right now, over your head.

Differentiation

Support: Start with only four phases (new, first quarter, full, last quarter) and the ball-and-lamp model; name each shape aloud.
Extension: Explain why the same phase is visible to people in different countries on the same night, and why a full moon rises around sunset.

Assessment

Formative (observation/peer): Can the learner model the Moon’s orbit and predict at least four phases correctly, and state that the Moon reflects sunlight?
Self-check: The learner asks, “Can I explain day/night with Earth’s spin and the phases with the Moon’s orbit — without saying Earth’s shadow makes the phases?”

Home connection

Watch the Moon for a few nights and sketch its shape on the chart. After several days, tell someone what changed and why.

Resources

NASA, “The Moon” — moon phases and the Earth–Moon–Sun system: https://science.nasa.gov/moon/
NASA Space Place, “What Are the Moon’s Phases?” (age-appropriate): https://spaceplace.nasa.gov/moon-phases/en/