Building and using a sundial gives children direct experience with one of humanity's oldest scientific instruments — and more importantly, direct perception of Earth's rotation. Marking the shadow's position every hour throughout a sunny day creates a tangible record of the sun's apparent movement. The sundial works: children can actually tell the approximate time from it. This is authentic science with a real practical application.

Simple Sundial Construction

1. Place a large paper plate (or cardboard circle) flat on the ground in full sun.
2. Push a straight stick (25–30cm) through the center of the plate at a right angle.
3. At each whole hour, mark where the stick's shadow falls and write the time.
4. By the end of the day, you have a working sundial.
5. The next sunny day, the sundial will tell the time without clocks (within about 15 minutes).

Science to Explore

• Why does the shadow move? (Earth is rotating, making the sun appear to move.)
• Why is the shadow longest in the morning and evening? (Sun is low on the horizon.)
• Why does the shadow point roughly north at noon? (Sun is due south at solar noon in the Northern Hemisphere.)

Frequently Asked Questions

Why don't sundials match the clock exactly?

Several factors cause sundials to differ from clock time. Time zones group large areas under one official time even though the sun position varies across the zone. Daylight saving time adds an extra hour offset. The equation of time describes small variations in the sun's apparent speed throughout the year (Earth's elliptical orbit and axial tilt cause these variations). Despite these offsets, a well-made sundial is accurate to within 15–20 minutes throughout the year — remarkable for an instrument with no moving parts.

Related activities: Shadow Investigation | Cloud Watching Journal | Homemade Compass