1Day and night
The Earth spins on its axis once every 24 hours. The half facing the Sun has day, and the half facing away has night. Spinning carries us from one to the other.
axis
Lesson 30.3 notes
Day, night and the seasons
Why we have day and night, why the Earth's tilt gives us seasons, and how day length changes round the world.
2The Sun's path in the sky
As the Earth spins, the Sun seems to cross the sky. It rises roughly in the east, is highest at midday, when it's due south from the UK, and sets roughly in the west.
3A year and a tilt
The Earth orbits the Sun once a year, about 365¼ days. Its axis is tilted by 23.5°, and always points the same way in space: towards the Pole Star.
4Summer and winter
In June the northern hemisphere, with the UK, leans towards the Sun: it's summer there, and winter in the south. In December it's the other way round.
hemisphere
5Why summer is warmer
In summer the Sun climbs higher, so its light hits the ground more directly and each square metre gets more energy. The days are longer too, giving more time to warm up.
6Day length
Near the Equator, days are about 12 hours long all year. Further from it, they change more: London gets about 16½ hours of daylight in June, but only about 8 in December.
7The midnight Sun
Near the poles, the Sun doesn't set at all in midsummer: it circles low round the sky, even at midnight. In midwinter it doesn't rise at all.
Explore: Seasons lab
Drag the Earth round the Sun and pick a place, from London to Sydney to the Arctic. See how high the Sun climbs at midday and how long the day lasts.
Common mistake: Seasons aren't caused by the Earth's distance from the Sun
The Earth's orbit is nearly a circle, and it's actually closest to the Sun in early January, in the UK's winter. The seasons come from the tilt of the Earth's axis.
Remember
- The Earth spins on its axis once every 24 hours, giving day and night.
- The axis is tilted by 23.5°. The hemisphere leaning towards the Sun has summer: a higher Sun and longer days.
- The two hemispheres have opposite seasons. Day length changes most near the poles and hardly at all at the Equator.
Going further at GCSE