Modelling Moon Phases with a Ball and a Lamp

None required — a lamp bulb can get warm, avoid touching it directly.

Disposal: No special disposal — reusable materials.

Materials

• A small ball (a polystyrene ball or even a tennis ball)
• A lamp with the shade removed, or a bright torch, to act as 'the Sun'
• A dark room

Steps

1. Place the lamp on a table and turn off other lights in the room.
2. Hold the ball at arm's length and slowly walk in a circle around the lamp, keeping the lamp roughly at your eye level.
3. Notice how the lit portion of the ball you can see changes as you move — this models what an observer on Earth sees as the Moon orbits.
4. Identify the position that models a 'new moon' (the ball's lit side facing away from you) and 'full moon' (the ball's lit side facing you).