Spark a conversation with this video showing some stunning sundials. This activity is great for describing observations and applying ideas in unfamiliar contexts.
Run the activity
1. You’re going to watch a short video. The aim isn't to find right answers, it's to explore ideas and find out what they know.
- Do they know what might happen based on the image?
2. After you've watched the video, lead a discussion with your class:
- Have the class seen sundials before?
- Do they know how sundials help us tell the time?
- Why do they think we no longer use sundials as our main method of time keeping?
- What are some similarities and differences between modern watches and sundials?
3. Ask the class to describe what they saw using only one word.
The Earth spins on its axis once every 24 hours and this creates the illusion that the sun is moving in the sky. In the morning, the Sun appears to rise and moves upwards in the sky and then, during the afternoon, to descend in the sky. As a result, shadows are longer at the beginning and end of the day, when the Sun is low in the sky, and shorter in the middle of the day. If it is observed carefully, the Sun also appears to move from east to west across the sky. This means that the shadows change direction as well as length.
A sundial uses this apparent movement of the sun to tell the time. Over the course of a day, sunlight casts shadows over different parts of a sundial, as the sun is blocked by the sundial point. The point of a sundial is called a gnomon (pronounced nom-on) and casts a shadow over the dial, which has markings to show what time of day it is.
Watch out for
A common misconception some children have is that the Sun is actually travelling across the sky. This can lead them to conclude that the Sun orbits the Earth. Other children may think that during a day, the Sun rises straight up in the sky and falls straight down in the same place. However, it is the Earth’s rotation that changes the position in which we see the Sun at different times.
For a detailed guide to children’s misconceptions and a guide to questions to assess prior knowledge look at these BEST resources.
Take it further
Carry on the investigation into shadows and sundials with this pack from Royal Observatory Greenwich, which includes more information and a Human Sundial activity.
This BBC Terrific Scientific resource (activity 3) helps children explore how shadow position can be used to tell the time and tackles the common misconception about the Sun moving across the Earth.
Linked Explorify activities- our recommendations:
Can children apply their knowledge of shadows in, What if there were two suns? or Have you ever had to move position because of a shadow?
Watch this BBC bitesize film and activities exploring shadows.