Phases of the Moon

Activities to try

1. 1

   Ball-and-lamp phase cycle (head as Earth)

   Why it works: The Sun always lights half the Moon; a phase is how much of that lit half we see from Earth as the viewing angle changes. The dark part of a crescent is the Moon's own unlit side, not Earth's shadow — and at the 'full' position your head's shadow passes just below the raised ball and misses it entirely, so no shadow is dimming it.

   1. In a darkened room, use a single bright lamp as the Sun and hold a polystyrene ball on a stick at arm's length as the Moon, held slightly above head height, with your own head as the Earth.
   2. Before turning, PREDICT with a reason: as you slowly turn the ball around your head, will it go through crescent → half → full, and what makes the dark part? Commit to your prediction out loud or in writing.
   3. Slowly turn on the spot and watch the lit fraction of the ball facing you grow and shrink through the full cycle.
   4. When the ball looks 'full', deliberately look for where your head's (Earth's) shadow points and check whether it passes just below the raised ball (it should if the lamp is at about head height or higher).
   5. Name each phase as it appears using waxing/waning vocabulary tied to the geometry (waxing = the lit part growing).
2. 2

   Linked orbit view and sky view

   Why it works: Coupling the orbit view to the sky view shows the phase morph continuously and lets learners test the Earth's-shadow account against what they actually see — it does not fit, most clearly for a crescent. At full Moon the lit face is turned fully toward us; Earth's shadow does point to the Moon's side of the sky (away from the Sun), but the Moon's tilted orbit usually carries it just above or below the shadow, which is why most full Moons are ordinary, not lunar eclipses. For a crescent, by contrast, the Moon is near the Sun's direction so Earth's shadow is on the far opposite side, nowhere near the Moon — the dark part is simply the Moon's own unlit side.

   1. Work with two linked views side by side: a top-down Sun-Earth-Moon diagram where you move the Moon around its orbit of a fixed, brightly lit Earth, and a synchronized view of how the Moon would appear from Earth.
   2. In the top-down view keep in mind the Moon is always half-lit toward the Sun; move it step by step around the orbit.
   3. At each position, read off the matching Earth-view phase and say why that fraction is visible.
   4. Park the Moon at the 'full' position, then trace where Earth's shadow points relative to the Sun and notice it extends toward the Moon's side of the sky.
   5. Use a 'line up the three bodies' challenge that arranges them in a row to show eclipse geometry, and a tilt control that lifts the Moon's orbit slightly high or low to show how the shadow usually misses.
3. 3

   Phase-wheel reference and 'why this phase?'

   Why it works: Naming and ordering the phases consolidates the cycle, and placing the phase wheel beside the eclipse diagram keeps the two ideas distinct: monthly phases from viewing angle versus rare shadow-casting alignments.

   1. Study a labelled phase sequence: new → waxing crescent → first quarter → waxing gibbous → full → waning gibbous → last quarter → waning crescent.
   2. For each phase, lift a flap or reveal the answer to 'why this phase?' and relate the sky appearance to the Moon's orbital position.
   3. Compare the phase wheel to an eclipse alignment diagram that distinguishes umbra and penumbra and the straight-line Sun-Moon-Earth (solar) versus Sun-Earth-Moon (lunar) arrangements.
   4. Use this as a consolidation reference after the hands-on and linked-view work.