Mon Prof Augmenté
Two Sticks at Noon
Age 16 · Science
At noon, two upright sticks far apart can cast shadows of different lengths because Earth’s surface is curved. The angle between the sunlight and each stick reveals how much of Earth’s circumference lies between them.
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Age 16: open this week
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In the picture
- The top of the left stick: where the vertical stick meets the incoming sunlight.
- The tip of the right stick’s shadow: the shadow’s length and direction.
- A parallel sunlight ray: incoming light striking both sticks at the same angle.
- The meeting point of the two lines at Earth’s center: the central angle between the two locations.
Examples
- Two friends in different cities compare their noon shadows by phone.
- A satellite dish and a flagpole in the same town cast unequal shadows at solar noon.
Key takeaways
- Earth’s curvature makes noon sunlight hit different places at different angles.
- A known distance between two locations and the angle difference can give Earth’s circumference.
Quiz: Two Sticks at Noon (Age 16)
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Why can two upright sticks far apart cast shadows of different lengths at noon?
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What does the angle between the sunlight and each stick reveal?
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If you know the distance between two locations and the difference in their noon shadow angles, what can you work out?
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