Describe how the tilt of the Earth's axis and the Earth's orbit around the Sun together cause the seasons experienced in the northern hemisphere.
Written & reviewed by James Millett — Biology (Imperial College London), PGCE Science (University of Cambridge).
Model answer (4 marks)
The Earth’s axis is tilted at about 23.5° to the plane of its orbit. As the Earth travels round the Sun, the tilt causes one hemisphere to lean toward the Sun while the other leans away. When the northern hemisphere is tilted toward the Sun it receives more direct sunlight and longer daylight hours, producing summer (or spring). When it is tilted away it receives less direct sunlight and shorter days, producing winter (or autumn). The two hemispheres therefore have opposite seasons at the same time.
Examiner tips
- Use the exact tilt angle (≈23.5°) to show knowledge of the axis orientation.
- Explain the link between tilt, daylight length and intensity of sunlight.
- Show that the seasons are opposite in the two hemispheres.
Common mistakes
- Confusing the tilt angle with the orbital eccentricity.
- Saying the Earth’s orbit is the cause of seasons instead of the tilt.
- Forgetting to mention the opposite seasons in the two hemispheres.
Mark scheme (4 marks)
- The Earth's axis is tilted (relative to its orbital plane / at an angle)
- When the northern hemisphere is tilted towards the Sun, it receives more sunlight / has longer daylight hours, causing summer (or spring)
- When the northern hemisphere is tilted away from the Sun, it receives less sunlight / has fewer daylight hours than hours of darkness, causing winter (or autumn)
- The two hemispheres experience opposite seasons at the same time / whilst one hemisphere is tilted towards the Sun the other is tilted away
Key terms in this question
axis · orbit · hemisphere
Related
- All Cambridge International IGCSE Physics (0625) revision notes →
- How to answer a "Describe" question →
- Decode the mark scheme abbreviations →
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