What it shows
The Moon always has one half lit by the Sun, but we see different amounts of it as it moves round the Earth. The box shows each phase from the viewer’s eye.
The science
The Moon takes about 29.5 days to complete its phases because it orbits the Earth in that time relative to the Sun. When the Moon lies between the Earth and the Sun we see none of its lit side (new moon). A quarter of the orbit later we see half of it lit, and at the far side we see all of it (full moon). The phases do not come from the Earth’s shadow, which only causes lunar eclipses.
Materials
Cost: under Rs 50. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A shoebox with a lid
- A polystyrene or paper ball painted white
- A torch
- A skewer to hold the ball
- Black paper
- A small hole as an eye window (adult cut)
Safety
For this project: An adult must cut the box. Use a torch, not a candle or a flame.
Never use mains electricity: power models with cells, batteries or a low-voltage adapter. Sharp and hot tools, flames and lab chemicals need an adult or your teacher beside you. Keep magnets, button cells and small parts away from young children, and wash your hands after making.
All the safety rulesStep by step
8 steps. Do them in order, and test each part before you go on to the next. Write what you notice in a notebook as you go.
Paint the inside of the shoebox black.
Cut a small peephole on one side as the viewer, which is the Earth.
Cut a hole in the opposite side and put the torch there as the Sun.
Fix the ball on a skewer at the centre and move it around the viewer.
Stand the ball at eight positions in a circle: new, crescent, first quarter, gibbous, full and back.
Look through the peephole at each position and sketch what you see.
Label each sketch with its name and number of days since new moon.
Explain why the Moon is not a shadow of the Earth.
What you should see
Eight sketches showing the correct sequence of phases from new moon to full moon and back.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1Why do we see phases?
We see different amounts of the lit half as the Moon orbits.
2How long does a cycle take?
About 29.5 days.
3What causes a lunar eclipse?
The Earth’s shadow falling on the Moon.
4Which phase is when the Moon is between the Earth and Sun?
New moon.
Take it further
Keep a real Moon diary for a month and compare it with your sketches.
Change one thing, measure what happens, and add a table or chart of your readings: that is what turns a model into your own investigation.
Free ebooks for this project
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