Physics · Earth and space
Why We Have Seasons
The Earth’s axis is tilted. As the Earth travels round the Sun, first the northern half and then the southern half leans towards the Sun.
- Date
- 21 Jun
- Season in Assam (north)
- Summer
- Season in Australia (south)
- Winter
- Noon Sun overhead at about
- 23.5° N
- In Assam
- Days longer than nights
Try this
- Move to June. Which half of the Earth leans towards the Sun?
- Move to December. What season is it in Assam? And in Australia?
- Find the two days when the Sun is overhead at the equator.
Key ideas
- The Earth’s axis is tilted by about 23.5°.
- The half leaning towards the Sun gets more direct sunlight and longer days: summer.
- Seasons are caused by the tilt, not by the Earth being closer to or farther from the Sun.
- The northern and southern hemispheres have opposite seasons.