Investigating shadow lengths
Shadows change length as the Sun moves across the sky.
Sun shadows
Shadows made by the Sun change during the day. In the morning and evening, when the Sun is low, shadows are long. Around noon, when the Sun is high, shadows are short.
The Sun’s shadows can be used to find north and south. At solar noon in Bangladesh, a shadow points almost exactly north.
Sun height
The height of the Sun in the sky is its altitude. Low Sun → light comes in at a low angle → long shadow. High Sun → light comes from almost overhead → short shadow.
A low Sun also feels less hot, because its light is spread over a larger area of ground.
A shadow stick
Put a shadow stick in a sunny place. Every hour, mark the end of its shadow and measure the length. The shadow also moves round, from pointing west in the morning to pointing east in the evening.
Ancient people used shadow sticks, called gnomons, to keep track of the time and the seasons.
Through the year
In Bangladesh, the midday Sun is higher in summer than in winter. So midday shadows are shorter in June than in December.
In winter, the Sun is lower in the sky all day, so even at noon shadows are quite long.
What I learnt
- I know that Sun shadows are longest when the Sun is low and shortest around noon.
- I can carry out a shadow investigation and present results in a line graph.