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Physics · Key Stage 2 · The School
Three motions
Earth spins once a day (day and night); Earth orbits the Sun once a year; the Moon orbits Earth about once a month. Keeping the three separate is the key — most confusion comes from mixing up a spin with an orbit.
Seasons are about tilt, not distance
Earth is tilted 23.5°. In summer YOUR hemisphere leans towards the Sun, so light arrives more directly and days are longer. It is not that we are closer — in fact Earth is slightly closer to the Sun during the northern winter. Tilt, not distance: the most useful correction in primary astronomy.
Moon phases
The Moon makes no light of its own; we see the half lit by the Sun. As it orbits, we see that lit half from different angles — full, gibbous, half, crescent, new. Model it with a ball, a lamp and your head as Earth, and the phases appear in front of you in about a minute.
Hold a tennis ball at arm's length with a bright lamp across the room as the Sun. Face the lamp with the ball in front of you: the lit side faces away, so you see a dark ball — new moon. Turn a quarter of the way round, keeping the ball out at arm's length: half of what you can see is lit — first quarter. Turn until the lamp is behind you: the whole face you see is lit — full moon. Your head is the Earth, and nothing was ever in shadow.