A shadow that tells the time
Fix a stick upright, straight up, in the ground. Its shadow moves through the day. Can it measure a day?
Step 1 of 3
- The Sun is low. The shadow is long.
- The Sun is highest. The shadow is shortest.
- The Sun is low on the other side. The shadow is long again.
The rule
Yes, a shadow can measure a day.
A stick's shadow is shortest when the Sun is highest. The time from one shortest shadow to the next is one day.
In the table, 24:01 means 24 hours 1 minute.
| Day | Shortest shadow at | Length of the day |
|---|---|---|
| 1 | 12:26 | — |
| 2 | 12:26 | 24:00 |
| 3 | 12:27 | 24:01 |
Watch out!
The shadow points away from the Sun. When the Sun is in the west, the shadow points east.
Read the times. Work out each day.
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