Seasons and how day length changes
Physics · Key Stage 1 · The School
Days get longer and shorter
In December it is dark before teatime; in June it is light after bedtime. The change is gradual and constant. Write down the sunset time once a week for a term and you will see a clear pattern — a real dataset you collected yourself.
Why: the tilt
The Earth is tilted. For half the year our part of the world leans TOWARD the Sun, so days are long and the light hits us more directly, which is summer. Six months later we lean away: short days, light hitting at a shallow angle, winter. It is not about being closer or further from the Sun.
Shadows tell you too
Put a stick in the ground and mark the tip of its shadow at noon each month. In summer the Sun is high and the shadow is short; in winter the Sun is low and the shadow is long. A shadow is a measurement, and this one has been used for thousands of years.
Write down the sunset time every Monday from September to December. Early September: about 19:45. Mid-October: about 18:10. Late November: about 16:00. Plot them and you get a smooth curve, not a straight line — the change is fastest around the equinox in late September and slows near the solstice in December. That curve is your own measurement of the Earth's tilt.