Science and Technology K–6 · Year 2

Moon phases with a ball and a lamp

Earth and Space (NSW 2017); Science understanding, Earth and space sciences, and Science as a human endeavour (ACARA v9)

Practical, model not builtLow risk

This site has no interactive model of its own. Where a step or a material names a Concept Studio model, simulation or tool, it has not been built; an external simulation a step names (for example PhET) is not part of this site.

The idea

Half the Moon is lit by the Sun at all times, and a phase is how much of that lit half faces Earth, which changes through a repeating cycle of about 29.5 days.

Safety card

Low riskAn adult supervises

Hazards

A darkened room with children turning on the spot and bumping one another
A lamp globe is a hot surface, and a lamp can be pulled over by its lead
Looking straight into a bright lamp
Evening observation away from school

Controls

The floor cleared and standing spots marked an arm's length apart before the lights go down
An LED globe in a lamp taped to the table with its lead run away from feet, out of reach of hands
Children look at the ball, never into the lamp, and the lamp is switched off before it is moved
The home half is done with an adult from a yard, window or balcony, and never involves looking at the Sun

Note

A lamp is a hot surface and an electrical appliance, so the NSW Department of Education science safety and compliance page applies. Record the activity on Primary School RiskAssess (riskassess.com.au).

What you need

1 desk lamp with a bare LED globe on a table at head height, as the Sun, taped down with its lead run away from feet
1 polystyrene ball 70 mm to 100 mm across per child, on a short skewer pushed in as a handle
A room that can be darkened with the blinds down
A chart of the eight phase names in order as NASA lists them: new Moon, waxing crescent, first quarter, waxing gibbous, full Moon, waning gibbous, third quarter, waning crescent
Chalk or tape for 8 stations marked in a circle around each child's standing spot
1 recording sheet per child with 8 empty circles for the room work, and a second sheet with 30 dated boxes for the home diary

How to do it

Clear the floor, mark a standing spot and eight stations for each child, then darken the room and switch the lamp on as the only light.
Stand facing the lamp with the ball held out at arm's length, a little above the line between your eyes and the lamp so your own head does not shade it. No lit face is turned towards you, which is new Moon. Draw it.
Turn to your right on the spot to the next station, keeping the ball out in front of you: a thin sliver on the left-hand side of the ball is lit, which is waxing crescent as it is seen from Australia. Draw it. Turn right again to the next station, a quarter turn from the start: the left half of the ball's face is lit, which is first quarter. Draw it.
Turn right to the next station and draw the waxing gibbous, then turn once more so the lamp is behind you, holding the ball above the shadow of your head. The whole face is lit, which is full Moon. Draw it, then lower the ball into your shadow and say what that would be if it happened to the real Moon.
Carry on turning the same way through waning gibbous, third quarter and waning crescent back to new Moon, drawing each shape and shading the dark part.
Write the eight names under the eight drawings from the class chart.
At home, with an adult, look for the Moon in the evening on as many nights as possible for a month and draw it in the dated box each time.
Back in class, lay the diary drawings in date order beside the eight room drawings, match them up, and count the days between one full Moon drawing and the next.

What you should see

In the room the shape changes in one fixed order and returns to where it started after a full turn, and every child in the ring sees the same phase at the same time, which is the point: the phase depends on where the Moon is, not on where the observer stands. NASA gives the cycle as about 29.5 days and the NASA Moon fact sheet gives the synodic period as 29.53 days, so the Sun-Earth-Moon angle opens at 360 divided by 29.53, which is 12.19 degrees a day: first quarter falls at day 7.38, full Moon at day 14.77 and third quarter at day 22.15. The lit fraction the children draw can be checked against (1 minus the cosine of that angle) divided by 2, which gives 0 at new Moon, 0.257 at day 5, a crescent about a quarter lit, 0.500 at day 7.38, 0.764 at day 10 and 1 at day 14.77. In the home diary the lit part thickens on the same side each evening for about a fortnight and then thins from the other side, and two full Moon drawings come 29 or 30 days apart. In Australia the waxing crescent is lit on its left-hand side, the opposite way round to pictures printed for the northern half of the world, which is why the room turn is made to the right: turning left gives the northern view, and saying so before the diaries come back saves an argument. The room model also shows why an eclipse is not monthly: the ball has to be lifted above the shadow of the child's head to reach full Moon, and the real Moon's orbit is tilted 5.145 degrees to Earth's orbit, so it usually passes above or below the shadow. The learner knows it worked when the eight room drawings and the diary drawings fall into the same order.

What changes

What you change: where the Moon is around Earth: the angle turned on the spot in the room, and the day of the cycle in the home diary
What you measure: how much of the lit face can be seen, drawn as a shaded shape and named
What you keep the same: one light source only, with the room dark and the blinds down
the ball held at arm's length and just above the shadow of the head
the same turning direction all the way round
the same observer and the same drawing sheet for the whole cycle

Common misconceptions

Each of these ideas is wrong, and the activity is a chance to test it.

The phases are Earth's shadow falling across the Moon.
The Moon has a permanently dark side, and the dark part of a phase is that side.
A crescent Moon is lit on its right-hand side, the way books from the northern half of the world draw it.
The Moon is only in the sky at night.
A full Moon means an eclipse is due.

Curriculum references

The NSW syllabus outcomes and Australian Curriculum v9 codes this activity supports. They are references, not a verified or complete curriculum alignment.

Science and Technology K-6 Syllabus (2017), NESA. Current syllabus; NESA's timeline is 2026 plan and prepare, 2027 start teaching the 2024 syllabus. Code read from the official syllabus document on 2026-09-22.ST1-10ES-S ST1-1WS-S
Science and Technology K-6 Syllabus (2024), NESA. Implementation from 2027, so this code describes the future syllabus. Code read from the outcomes page on 2026-09-22.ST1-SCI-01 ST1-DAT-01
Australian Curriculum v9AC9S2U01AC9S2H01AC9S2I01AC9S2I03AC9S2I04AC9S2I06

Sources

The pages the author read to write this activity.

All Concept Studio activities