Fashioning a sundial from a paper plate and a pencil is the perfect activity for a sunny day. This experiment teaches your child that because of the Earth’s rotation, the sun appears to move across the sky, giving us a way to tell time.
For this activity, you need the following materials:
- A paper plate (or a large circle cut from cardboard)
- A pencil (or a straw, chopstick, or skewer)
- A marker or pen
- A pointy object (such as a well-sharpened pencil)
- A compass or compass app (optional)
- A watch
- Rocks to keep the sundial in place (optional)
Start by finding a spot to set up outside, and bring all your materials there a little before noon. Stick the pencil (or straw, etc.) through the center of the paper plate or cardboard circle so that when standing perfectly vertical, it casts a shadow pointing north. If you like, you can check which way is north using a compass or a compass app on your phone. Leave the sundial where it is (if needed, hold it in place with rocks) and come back in an hour. At 1 o’clock, have your child write the number 1 at the spot on the edge of the plate that the pencil’s shadow is pointing to.
What does this activity demonstrate? The length of the shadow depends on the position of the sun: the higher the sun is on the horizon, the shorter the shadow. In the northern hemisphere, the sun reaches its highest point on the summer solstice because the North Pole is tilted towards it. To take this activity one step further; try doing it at different times of the year to see how the shadow changes.