Push a straight stick into open ground in a sunny spot. Every hour, mark the exact tip of its shadow with a stone or chalk and write the time beside it. By the end of the day, a row of marks shows how the sun has moved across the sky. Return the following day at any of the marked times — the shadow matches the mark within minutes.

What you need

straight stick
stones or chalk for marking
watch

How to do it

1"We're building a clock that runs on sunlight — let's set it up." Push a straight stick into the ground in a sunny spot, first thing in the morning.
2Every hour on the hour, mark the tip of its shadow with a stone. Write the time.
3By evening, a curve of marks shows exactly how the sun crossed the sky.
4Come back tomorrow at any marked hour. The shadow will land on the mark within minutes.

Variations

If they forget or lose interest between markings: mark the shadow yourself and just call them over for ten seconds each hour — "come see where it landed" — the tiny, repeated reveal keeps them checking in without needing to commit to the whole day.
End the day's marking with tomorrow already promised: "last mark for today, we test it in the morning" turns stopping into a cliffhanger, not a finish.

💡 Parent tip

The difference between the morning and afternoon marks is striking: the shadow is long in the morning, short at midday, long again in the evening — but on the opposite side. A child who notices this without prompting has intuited the earth's rotation. This runs across a whole day and needs supplies on hand — if things are already heated right now, use a physical/sensory reset instead, like Stone Balancing or Sit Spot.

What your child develops

Astronomy — the sun's apparent movement across the sky is caused by the earth's rotation
Measurement across time — each hourly mark is a data point in a day-long observation
Navigation thinking — shadows told time for thousands of years before mechanical clocks