Experiment: Day length in Summer and Winter
AIM To explain why the number of daylight hours varies
METHOD
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Do this experiment in a darkened room; this will help you see more clearly the contrast between
light and dark.
Hold the skewer vertically. Push two pins into your sphere — one about where Sydney is and the
other directly above it at the top of the sphere, near the skewer.
Set the torch up in a central place (such as on a table you can move around).
Stand to the left of the torch. Turn on the torch. Hold the skewer so it leans away to the left from
the vertical. The southern half of your sphere should be leaning more towards the light.
Slowly turn your sphere in the light, making sure you keep the skewer slightly tilted. Turn it in an
anticlockwise direction. Observe how long the two locations marked with pins remain in the light.
Now stand to the right of the torch holding your skewer tilted to the left as before. This time the
northern half of your sphere should be leaning more towards the light. Repeat what you did in the
previous step.
Repeat the whole procedure above two more times. The first time, look at what happens at each of
the poles. The second time, look at what happens at the equator.
DISCUSSION
1. Which pin comes into the light first when the southern half of the sphere leans towards the light?
Ask your partner which pin moves out of the light first.
2. What does this tell you about the number of daylight hours in each hemisphere when the Southern
Hemisphere tilts towards the sun?
3. Which pin comes into the light first when the northern half of the sphere leans towards the light?
Ask your partner which pin moves out of the light first.
4. What does this tell you about the number of daylight hours in each hemisphere when the
Northern Hemisphere tilts towards the sun?
5. What is the approximate length of day and night at the equator in each season?
6. Suggest why the sun never sets at certain times of year at the North and South Poles. Which
season is the Southern Hemisphere experiencing when the South Pole has several months of
darkness?