Build a sundial: tell time like ancients
Make a cardboard sundial with a stick and learn how Earth rotation tells time.
Materials and 15-minute setup
You need a flat cardboard square, a straight 15 centimeter stick, tape, a compass, a marker and a sunny spot. Push the stick through the center and fix it with tape so it stands firm and straight for shadows.
Point the top of the stick toward true north using your compass. Tilt it upward by your latitude, for example 40 degrees in New York or 51 degrees in London, so it stays parallel to Earth axis.
Mark hours and understand rotation
Start at 10 in the morning and mark where the shadow falls every hour until 4 in the afternoon. Label each line with the clock time and check next sunny day to see how accurate your ancient clock really is.
Shadows move because Earth rotates 15 degrees every hour and completes 360 degrees in 24 hours. The first shadow clocks appeared in Egypt around 3500 years before present and used the same simple principle daily.
- Use true north, not magnetic north
- Tilt angle equals your latitude
- Best hours are 10 to 4
- Winter shadows are longer
- Egypt made clocks 3500 years ago