Science Experiment – Sundial

By AG Education 12 December 2017
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Create your own sundial to tell the time

About this experiment

In this experiment, you can create your own version of a sundial. Before we had wristwatches and wall clocks, or even established our modern time measurement system with hours and minutes and seconds, humans relied on this ancient invention to tell the time of day by examining the changing shadow from the Sun as it moves from rising to setting.


  • Large paper cup, with a lid that has a hole for a straw (like the ones given for takeaway)
  • Straight straw
  • Sharp pencil
  • Sticky tape
  • Stones or sand (about a handful or two)
  • Clock or watch
  • Compass

Make sure you try this experiment on a day when you’re free to track the Sun’s progress.


  1. Use the pencil to poke a hole in the side of the cup, about 5cm below the cup’s rim. The hole should be wide enough for the straw to pass through.
  2. Fill the cup about halfway with sand or stones to weigh it down, and then place the lid on the cup.
  3. Push the straw through the hole in the lid, and then through the hole in the side of the cup. The straw should not have bent, and the top of it should stick up about 5cm above the lid.
  4. Tape the bottom end of the straw onto the side of the cup.
  5. Go outside and find a spot that’s usually filled with sunlight throughout the day. Use the compass to correctly point the straw north.
  6. At 10am mark a line on the lid to show where the shadow of the straw falls. Continue to mark the shadow’s changing placement every hour until 4pm. Be sure to label each marking with the correct hour.
  7. After the final marking at 4pm, your sundial is complete!
  8. Next time there’s a sunny day, set up your sundial in the exact same place, making sure it’s facing north, and read the time! You can test your sundial by looking at your watch and seeing if the times appear to match.

Do you want to keep learning? Find more experiments here!