The Sun: Make a sundial:
Learning outcomes:
• know that you can tell the time using a sundial
• tell the time using the Sun
• discover that long ago it was much more difficult to tell the time than it is today end product • a small sundial indoors
• a large sundial outdoors
Preparation For the activity The large sundial you will need a playing field that is in sunlight most of the day. What time is it? 5 min. Ask if any of the children is wearing a watch. Why is it handy to have a watch? Explain that 600 years ago nobody had a watch. Ask how the people back then knew what time it was. Before the mechanical clock was invented, people sometimes used the sun to tell the time. They did this using a sundial. Have any children ever seen a sundial? Do they know how it works? Explain that a sundial has a stick or pointer that makes a shadow. This is called the gnomon. It is important that in the Northern hemisphere the gnomon always points North, or you will not be able to read the sundial. Explain that the Earth turns on its axis. This means that the position of the Sun with regard to the Earth is always changing. If necessary demonstrate this using a torch and an orange. Explain that the shadow of an object also changes as the Earth rotates. The sundial uses this fact. By looking at the position of the shadow of the gnomon on the sundial, you can tell what time it is. The children make two sundials
The large sundial:. Make a large sundial with the children. Take the children outside to a location where the sun shines most of the day. Mark the direction of North, using a compass if necessary. Stand the large protractor upright on its long side in the grass. Use it to measure the correct angle to the ground, as described above. Stick the stick firmly in the ground at the chosen angle, facing North. See the picture for how this should be done. Every hour the children place a large stone on the ground where the shadow of the stick falls. One of the children uses the marker pen to write the number of the hour on the stone. You can use the smaller stones to mark the quarter and half hours. If you don’t want to take the children outside every hour, you can just place two stone markers, one in the morning for example at 9.00) and one in the afternoon (for example at 14.00). Of course your sundial will be less accurate. To finish the sundial, the rest of the day after school-time needs to be divided using the stones. In the example shown here, five hours have passed and so the time in between needs to be divided into five. Encourage the children to write the numbers of the hours on the stones and place them in the correct position. The next day, take the children outside to see if they can read what time it is. How accurate is their sundial? The children then make their own sundials at home as part of home/school links. Encourage the children to share their sundials on see-saw.