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Many students hold the misconception that its colder in winter because the Sun is further away. This demonstration shows it is the tilt of the Earth’s axis that is responsible.
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Seasonal Change
Earth and Space
Teaching seasons
Lesson for 11-14
Use this sequence of practical activities and diagnostic questions to develop your students' reasoning in three-dimensions and understanding of how seasons are caused by changes in sunlight angle and day length.
Attach thermochromic plastic to a globe to show that temperature in the UK depends on whether our hemisphere is tilted towards or away from the Sun.
Apparatus and Materials
- World globe
- Filament lamp (or electric heater)
- Self adhesive thermochromic plastic
Preparation
Cut the thermochromic plastic into a strip and place it vertically on the globe next to the UK. Set the lamp-globe distance to ensure the thermochromic plastic strip shows a range of colours.
Procedure
- Rotate the base of the globe so that the northern hemisphere is tilted directly towards the lamp (summer in the UK)
- Switch on the lamp and highlight the changing colours of the thermochromic plastic (counter-intuitively lower temperature is indicated by red and higher by blue).
- Switch off the lamp and rotate the base of the globe so the nothern hemisphere is tilted directly away from the lamp (winter in the UK). Emphasise that you have not changed the lamp-globe distance.
- Switch the lamp back on.
Discussion prompts
- When the northern hemisphere is tilted away from the Sun is it summer or winter in the UK?
- What season is it south of the equator?
Teaching Notes
This demonstration tackles the common misconception that winter happens because the Sun is further away. Compare the UK (55°N) to a similar latitude south of the equator (eg Bouvet Island in the South Atlantic at 54°S) to emphasise that summer in the northern hemisphere corresponds to winter in southern, and vice versa,
Explain that you are turning the globe around for convenience. The direction in which the Earth’s rotation axis points doesn't really swap between summer and winter. Which hemisphere is leaning towards the Sun changes because of the Earth’s annual journey around the Sun.
Learning outcome
Students identify corresponding seasons for northern and southern hemispheres.
In this activity students use a lamp and piece of paper to show how the light from the Sun spreads out more when it strikes the Earth at an angle.
Apparatus and Materials
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Each student will need
- Large piece of card
- Board to which card can be fixed
- Lamp with cardboard cylinder
- Two different coloured marker pens
Procedure
- Put a cardboard cylinder around the end of the lamp to provides a rougly circular area of light.
- Draw a line around the area where the light falls when the card is perpendicular to the light source,
- Repaet for when the board is at an angle.
Teaching Notes
The demonstration shows that when light hits a surface at an angle it is spread out over a greater area than if it strikes the surface perpendicularly. Any energy transfer is therefore spread over a greater area.
In place of the card, a photocopied map could be used to make the demonstration look more like a part of the Earth's surface.
Use a lamp and a transparent dome attached to a globe to show how the path of the Sun across the sky varies over the year.
Preparation
This activity works best in a darkened room.
Equipment
- Approx. 40 cm diameter globe
- A small transparent dome (eg half of a 4 cm clear plastic bauble)
- Lamp
- Blu Tack or sticky tape
- Books to adjust height of lamp (optional)
Procedure
- Use blu-tac or sticky tape to attach the dome to the globe so that it covers the UK.
- Place the globe about 1 m from the lamp (the Sun). Adjust the lamp's height so that it is the same as the globe’s equator.
- Position the globe so that the northern hemisphere is tilted away from the Sun.
- Spin the globe anticlockwise about its axis so that the reflection of the lamp appears on the base of the eastern edge of the dome, travels up the dome and sets on the western edge.
- Repeat, but this time tilt the globe's Northern Hemisphere towards the Sun (the arm of the globe may get in the way when you spin. Detach and re-attach dome as required).
Discussion prompts
- Which lasts longer: day or night?
- What season is it in the UK?
Teaching notes
This demonstration tackles the common misconception that the path of the Sun across the sky does not vary over a year. Students should see that when the northern hemisphere is tilted away from the Sun (first day of winter in the UK) sunrise to sunset takes less than half a spin, day is shorter than night and the Sun follows a low path across the sky. When the northern hemisphere is tilted towards (first day of summer in UK), the Sun follows a high path across the sky, days are longer than night and it is warmer because the sun's radiation warms the ground for more time.
You could also demonstrate the path of the Sun across the sky on the first day or spring/autumn to show that day and night lasts equal times and the Sun follows an intermediate path across the sky.
Learning outcome
Students explain why days are longer in summer and how this contributes to it being warmer.
This experiment was safety-checked in March 2020.
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Students use a ball and stick to model the motion of a planet around a star and deduce how seasons may be different to those on Earth.
Preparation and safety
Ask students to be careful when building planets as skewers may be sharp. Warn students not to stare directly into the lamp
Equipment
Each pair of students will need:
- Lamp
- Polystyrene ball
- Bamboo barbecue skewer (length of 30 cm approx.)
- Marker Pen
Procedure
Ask students to:
- Carefully push a skewer through the ball to make an planet
- Mark the N and S poles where the skewer passes through the ball.
- Draw a line round the ball to represent the planet’s equator.
- Spin the planet on its axis and discuss with a partner why this gives night and day.
- Tilt the axis of the planet and move it slowly round the star. Discuss when the planet will experience summer in the northern hemisphere and when it will experience winter.
- Model an exoplanet with a highly elliptical orbit.
- Model an exoplanet that has no tilt and orbits with the same face to its star at all times (a tidally locked planet)
Discussion prompts
- How long does an exoplanet day last compared to its year?
- Would there be seasons?
- Could life exist on such a planet?
Teaching notes
If students are unfamiliar with the idea of an exoplanet introduce it. Exoplanets are planets that orbit stars other than our Sun. Astronomers have discovered several thousand and would like to know if any might be home to life.
A planet with a highly elliptical orbit will have seasonal variations, but they would not be like those on Earth. The whole planet will experience the same season at the same time: summer when it is closest to its star and winter when it is furthest away. In the course of a year, its orbit may take it in and out of the ‘habitable zone’ where conditions for life are thought to be most favourable. Life might evolve to hibernate for part of the year, or to aestivate when the temperature is too high.
For a tidally locked planet there are no seasonal variations. Its day is as long as its year. One side of the planet will always be in daylight and hot, the other in permanent darkness and cold. There will be a twilight zone between these two regions which might be a suitable place for life. Alternatively, life might exist beneath the surface.
Learning outcome
Students use their understanding of how seasons arise on Earth to predict how they may be different on other planets.
Questions for students to complete individually or for use on the board with electronic or mini whiteboard voting.
Based on the Best Evidence Science Teaching resource produced by the University of York Science Education Group.
Explore the misconceptions mentioned in this collection and more on the topic of seasons.