This article first appeared in MAPE Focus on Science Autumn 2000
The British weather makes it notoriously difficult to plan for any outdoor activities, far less those requiring full sun all day! The introduction of new government initiatives has made things even harder. No longer is it acceptable to abandon all one's planning and devote a day to study sun and shadow just because the weather is clement.
For this reason alone many children never get the opportunity to prove for themselves that the movement of the earth alters shadow direction and length, although it is almost certainly something they have observed and tucked away in the back of their minds as a curiosity.
By the end of the lesson (s) children will:
National Curriculum references
Key Stage 2 Science
v Sc1 Scientific enquiry
- Ideas and evidence in science
- Investigative skills
Obtaining and presenting evidence
v Sc4 Physical Processes
- The Earth and beyond
How the position of the Sun appears to change during the day, and how shadows change as this happens
How day and night are related to the Earth spinning on its own axis
That the Earth orbits the sun once each year . . .
There are further links with KS2 Geography (weather) and KS2 Maths (handling data, shape space and measures).
Links with ICT
1. Tell the rest of the school what you are doing and ask them not to touch your experiment.
2. Get a stick of suitable length, 50 cm or 1 m is ideal.
3. Fix the stick securely in a pot in a vertical position. You may need a spirit level to check this.
4. Choose a suitable location for the experiment. It might be worth observing different locations beforehand to make sure that the shadow length can be measured all day.
5. Put a large sheet of paper under the pot so that the shadow always falls on it.
6. Set alarms to remind you to take measurements.
7. On each hour (or whatever time interval you decide upon) measure and record the length of the shadow. Carefully mark the direction of the shadow on the sheet of paper. If your stick is short enough and your paper large enough you could mark the length as well.
Diagram showing the direction of shadows through the day.
8. At the end of the day collect your data and enter it into the computer.
9. Draw appropriate graphs.
10. Discuss what they show. This is the most important part of the activity and must not be rushed.
Key questions leading to additional activities
1. What happens if the stick isn't vertical?
2. Does this graph tell us at exactly what time the shadow is at its shortest?
3. Why isn't the shadow at its shortest at noon?
4. Will the shadows be the same length if we measure them next week? Month?
5. Will the shadows be the same length in another part of the country? World?
6. If we measure the shadow of 50cm stick and another school uses a 100 cm stick will that shadow be twice as long as ours?
7. Will the angles between the shadows always be the same?
8. If we don't have a protractor can we calculate the angle?
9. Can we predict how long the shadow was at 5 pm?
You may find that printing graphs out and photocopying onto OHTs makes it easier for everyone to see and compare.
Linking sun and shadow activities to Science Explorer
Science Explorer includes a simulation of the earth's rotation, demonstrating how seasons and day and night occur, and how these differ across the globe. This will need a lot of explanation for some children.
Of course it is only a simulation. The children in our classrooms are unlikely to be in a position to see for themselves the effect of the curvature or rotation of the earth on shadows in, for example, Singapore. What better way of making use of modern communications than to link up with other schools across the world and compare shadow lengths? Some of you may already have established links with other schools. If you haven't then why not send your data to MAPE and we will post it on our website for other schools to access?
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