Before analog and digital clocks were invented, sundials were used to mark the passing of time every day. The Egyptians first developed this technology around 1500 BC and aptly called them shadow clocks. They constructed shadow clocks by using a crossbar and a vertical stick, called a gnomon, and marked 5 time increments on the shadow clock. The gnomon was exposed to the sun’s rays and cast a shadow from the sun on the ground. As the day progressed and the sun moved from east to west across the sky, the gnomon’s shadow moved and indicated the passage of time. They could refer to this every day to tell the time. With a few adjustments for the seasons and the orbit of the earth, it’s pretty accurate! Genius!
This time-telling tool is fun and easy to recreate at home with your kids to show them how people used to track the time long before clocks and cell phones did it for us. Here are a couple of different methods for how to make a sundial. It’s science time!
Paper Plate Sundial
- Paper plate
- Using your ruler, determine the very center of the paper plate. Poke a hole in this spot using a sharp knife or scissors.
- Turn the plate upside down.
- With a crayon or colored pencil, write the number 12 on the edge of the plate.
- With your ruler, draw a straight line from the 12 to the hole in the center of the plate.
- At 12:00pm (noon), take your plate outside and place it in a spot that receives sun all day long. Set the straw in the hole so that it stands up straight. If it’s wobbly or crooked, use tape or molding clay to secure it.
- Turn the plate until the shadow of the straw is exactly on the 12. This is where you’ll leave it for the rest of the day.
- Secure the plate with rocks so that it doesn’t get blown away or moved around at all.
- One hour later at 1pm, check on your plate and record where the shadow from the straw falls on the plate. Label it with a 1.
- Repeat step 8 for the next few hours and label each new hour with its corresponding number (1, 2, 3, etc.). After you have a few hours recorded you can start to predict where the shadows will fall. Set a timer to go off every hour so you don’t forget!
- Once your sundial is complete, you can set it up outside every day to tell the time without looking at your phone or watch.
- Test the accuracy of your new sundial by comparing it to the time on your phone or watch. Make adjustments if needed.
- Small, rectangular, flat piece of wood
- 7-inch dowel
- A drill
- Marking pieces (thumb tacks, rocks, etc.)
- Writing tool (marker, pen)
- Drill a hole through the very center of the piece of wood.
- Place the dowel in the hole so that it’s standing up straight. Use hot glue to keep it upright if it’s wobbly.
- Set your sundial in a place outside that has full sun exposure.
- At the top of the hour when you’re starting the recordings, mark where the shadow of the dowel falls by placing your thumbtack or rock on the shadow.
- Write the hour next to the thumbtack or rock.
- Set a timer to go off at the top of every hour.
- Repeat steps 4 & 5 until you have 13 hours marked.
- The pattern created by the thumbtacks or rocks will resemble a semi-circle.
- Depending on the time of day you begin your recordings, it may take a couple days for you to complete your sundial. Stop when the sun goes down and resume the next day once the sun comes up. Mark each hour until you reach the first mark from the day before.
- Compare the time on your sundial with the time shown on your phone or watch. Make any adjustments if needed.