Weather & seasons · Earth’s axial tilt
Why do we have seasons?
Four memories fit onto one woodland path.
The short answer
Earth spins around an imaginary line through its North and South Poles: its axis. This axis is tilted relative to Earth’s path around the Sun. Day length and the Sun’s height therefore change through the year.
During summer in Germany, days are longer; the Southern Hemisphere has winter.
Same axis, different sunlight
1. June: north towards the Sun
Yellow is the Sun; blue and green are Earth. N marks the North Pole. The brown axis leans to the upper left: north points towards the Sun here. Germany has long days and a high Sun.
2. December: north away from the Sun
Half a year later, Earth is on the other side of the Sun. The axis still points to the upper left. North now tilts away from the Sun: Germany has shorter days and a lower Sun.
3. The same light spreads differently
The upper ground receives steep light, the lower ground receives slanting light. Each set of three arrows stands for a beam of the same width. Below, it spreads over a longer patch, so each area receives less energy.
The tilted line through Earth is its axis: an imaginary line Earth spins around. The thin cross-line is the equator, dividing the northern and southern halves.
Summer and winter are reversed in the Southern Hemisphere. These are selected times, not a scale map of sizes or distances.
Longer days and steeper sunlight work together.
Why can Germany have summer while Australia has winter?
Earth’s axis stays pointed in roughly the same direction during its orbit. In northern summer, north tilts towards the Sun, with longer days and a higher Sun. South tilts away at the same time. Half a year later this reverses; the distance of the whole Earth does not explain the contrast.
An imagined Wusel scene
Puschel and Flauschi investigate
Puschel remembers flowers, warm grass, colourful leaves and snow. Puschel“Our path has lots of outfits.” Flauschi smiles. Flauschi“And we keep visiting it through the year.”
They lay four blank picture cards side by side. Puschel describes each season without pretending every year is the same. Spring may come late and winter may be mild.
Flauschi“Four memories, one path,” says Flauschi. Puschel wants to collect the next one straight away, but the year takes its time.
Little Wusel quiz
Why is it winter in the Southern Hemisphere when it is summer here?
Show answer
In northern summer, the Northern Hemisphere is tilted towards the Sun: our days are longer and the Sun is higher. In the Southern Hemisphere, days are then shorter and the Sun is lower.
Word help
- orbit
- The path of one body around another.
- axis
- An imaginary line around which something turns; in machines it may also be a physical part.
Explore in more detail
Here you will find longer explanations and further details. You can explore them together.
Understand step by step
How it works – simply explained
Earth’s axis is tilted
Earth spins around an imaginary axis tilted relative to its orbit. The axis points roughly the same way throughout the orbit.
Light arrives differently
When the northern hemisphere tilts towards the Sun, the Sun is higher and days longer. More energy reaches an area over the day: northern summer.
The other half has the opposite
The southern hemisphere then has winter, reversing half a year later. Changing whole-Earth distance from the Sun cannot explain opposite seasons.
Why Australia does not share our summer
When the northern hemisphere tilts towards the Sun, days are longer and sunlight generally arrives more steeply. The southern hemisphere tilts away, so northern summer can coincide with Australian winter. Half an orbit later conditions reverse. Both hemispheres share the same Earth; their opposing tilt explains different seasons.
References for this explanation: [1]
The key points again
Discover
Earth’s axis is tilted. As Earth travels around the Sun, its northern and southern hemispheres receive different amounts of sunlight through the year.
Understand
Here in Germany the summer Sun is higher and days are longer than in winter.
Connections
Seasons mainly result from the tilt, rather than the whole Earth being closer to the Sun in summer. The Southern Hemisphere has opposite seasons.