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Carry the globe round the lamp. Why is summer long and winter short?
Earth's Seasons lab · Last updated: 16 October 2026
You carry a globe round a lamp, just as Earth travels round the Sun, and watch how the light falls on each part. They find out why summer brings long days and winter short ones. It clears up a very common mistake: seasons are not caused by Earth getting closer to the Sun.
What you'll discover
- Earth's axis is tilted by about 23.5 degrees, and it keeps pointing the same way as Earth goes round the Sun.
- When your half of Earth leans towards the Sun, days are longer and the Sun is higher, so it is summer.
- The northern and southern halves of Earth have opposite seasons at the same time.
The science in plain words
Earth spins on an axis that is tilted by about 23.5 degrees compared with its path round the Sun. The axis keeps pointing in the same direction in space all year, towards the North Star. So for part of the year the northern half of Earth leans towards the Sun, and six months later it leans away.
When your hemisphere leans towards the Sun, two things happen. The Sun climbs higher in the sky, so its rays strike the ground more directly and their energy is concentrated on a smaller area. And more of each turn of Earth is spent in sunlight, so days are long and nights short. The ground has many hours to warm up and few to cool down: that is summer. When your hemisphere leans away, the Sun stays low, its light is spread thinly, days are short and it is winter.
Distance is not the cause. Earth's orbit is nearly circular, and Earth is actually closest to the Sun in early January, during the northern winter. This also makes the northern summer half of the year a few days longer, because Earth moves a little more slowly when it is furthest from the Sun. Near the equator the tilt matters less, so day length hardly changes and seasons there are often wet and dry rather than hot and cold.
Where it fits
- India, NCERT: Class 7 science, Chapter 12: Earth, Moon, and the Sun
- United States: Grades 6 to 8
- Next Generation Science Standards: MS-ESS1-1
Common questions
What causes the seasons?
The seasons are caused by the tilt of Earth's axis, about 23.5 degrees. As Earth orbits the Sun, each hemisphere takes turns leaning towards it. The hemisphere leaning towards the Sun gets longer days and more direct sunlight, giving summer, while the other has winter.
Is summer caused by Earth being closer to the Sun?
No. Earth is actually closest to the Sun in early January, which is winter in the northern hemisphere. The difference in distance through the year is small. The tilt of Earth's axis, which changes day length and the angle of sunlight, is what causes the seasons.
Why are days longer in summer?
In summer your hemisphere is tilted towards the Sun, so a larger part of each daily turn of Earth is spent in sunlight. The Sun rises earlier, climbs higher and sets later. Near the poles the effect is so strong that the Sun may not set at all.
Related labs
- Moon Phases: A lamp, a globe and a Moon on real gravity: why does the Moon change shape?
- Solar System: A desk orrery run by real gravity: why does Mars take longer than Earth to go round?
- Solar & Lunar Eclipses: Line up the lamp, the globe and the Moon: why is there not an eclipse every month?
See all earth and space labs or every Taz science lab.
Try it yourself
The Earth's Seasons lab is one of the interactive 3D science labs inside Taz. Change one thing, predict what will happen, then run it and watch. Labs open after you sign in.