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.

### Up next

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.

### Up next

An activity to introduce the idea that it is warmer in summer because the sunlight intensity is higher.

### Up next

A demonstration to illustrate the second reason it is warmer in summer: the days are longer.

Seasonal Change
Earth and Space

## Seasons: Skydome

Practical Activity for 11-14

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

1. Use blu-tac or sticky tape to attach the dome to the globe so that it covers the UK.
2. 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.
3. Position the globe so that the northern hemisphere is tilted away from the Sun.
4. 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.
5. 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.

### Up next

An activity to review how seasons arise on Earth and one that challenges students to apply their understanding to new situations.

Seasonal Change
Earth and Space

## Seasons on exoplanets

Practical Activity for 11-14

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

1. Carefully push a skewer through the ball to make an planet
2. Mark the N and S poles where the skewer passes through the ball.
3. Draw a line round the ball to represent the planet’s equator.
4. Spin the planet on its axis and discuss with a partner why this gives night and day.
5. 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.
6. Model an exoplanet with a highly elliptical orbit.
7. 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.

### Up next

Questions to check students' understanding.

Seasonal Change
Earth and Space

## Seasons: Questions

Diagnostic Questions for 11-14

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.