What it shows
The Moon’s lit shape changes in a steady cycle of about 29.5 days, and it rises roughly 50 minutes later each night. Your own sketches show this pattern better than any picture in a book.
The science
The Moon shines by reflected sunlight, and half of it is always lit. As the Moon goes round Earth once every month, we see different amounts of the lit half. The Moon also moves eastward against the stars, so it rises later each night than the night before.
Materials
Cost: free. Many items come from home or from waste; spare parts such as LEDs, motors and wire are in the store.
- A notebook with a circle printed or drawn on every page
- A pencil and a yellow crayon
- A watch or phone clock
- A free spot with a view of the sky
- A paper calendar
Safety
For this project: Observe from a roof or lawn only with an adult nearby, and never use a torch near other people’s eyes.
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.
Draw 30 circles in the notebook, one for each night, and write the date under each.
On the first clear evening, find the Moon and note which side is bright, the left or the right.
Sketch the lit shape by shading the dark part with pencil, and leave the bright part blank or yellow.
Write the time you saw it and the direction in which it appeared in the sky.
If a night is cloudy write "cloud" and carry on; do not draw from memory.
Look at the rise time again once or twice a week and write it down.
After the cycle, stick the circles in order on a long strip of chart paper.
Name each shape: crescent, quarter, gibbous, full and the matching waning ones.
What you should see
A strip of Moon shapes from thin crescent to full and back, with a rise-time table showing the Moon coming up about 50 minutes later each day.
Viva questions
A teacher or a judge will ask how it works. Try to answer each question before you open it, then compare.
1How long does the cycle of phases take?
About 29.5 days.
2Why does the Moon seem to change shape?
We see more or less of its sunlit half as it moves round Earth.
3Does Earth’s shadow cause the phases?
No, Earth’s shadow causes only a lunar eclipse.
4Why does the Moon rise later each night?
It moves eastward in its orbit while Earth turns.
Take it further
Compare your sketches with the dates of Purnima and Amavasya on a panchang calendar.
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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