Physics KS3/KS4: Professor Brian Cox - Why do we have days, nights and seasons?

In this video, Professor Brian Cox uses a simple demonstration to explain why we have day and night, and why in the northern hemisphere, days are longer in the summer and shorter in the winter.

Using only an orange and a lamp, representing the Earth and sun respectively, this video demonstrates clearly the impact of the Earth's tilt on the amount of sun that falls on the northern hemisphere during different stages of the year, giving us seasons.

The demonstration also shows the impact of the Earth’s spin on day and night, which affects the length of the day.

Teacher Notes

Points for discussion

  • Students often find it difficult to visualise the movement of the Earth relative to the sun. This simple model is similar to one used in many classrooms, and uses video to ensure all students see and hear the same details.

  • Students often confuse the significance of the Earth’s tilt (seasons) with the significance of the Earth’s rotation (day and night). In this film, the two are highlighted separately and clearly.

Suggested activities

  • This demonstration could replace one that you would normally do in the classroom, or it could be used to reinforce it, particularly at KS3 but also for revision at KS4 in an introduction to a space topic.

  • The learning could then be assessed and reinforced by asking students to apply it to a different part of the Earth, such as at the Equator or in the southern hemisphere.

Curriculum notes

Suitable for KS3 England, Wales and NI and CfE Scotland, S1-3, Combined Science and Physics GCSE in England, Wales and Northern Ireland and at National 4 and 5 in Scotland

More from this series:

Why do astronomers use 'light years' to measure distance in space?
What is the Milky Way?
Moons in our solar system
The solar system