Investigating shadow lengths
This Topic is About...
- I will explain how changes in shadows happen because Earth spins on its axis.
- I will make predictions and check if results support them.
- I will measure the lengths of shadows and describe simple patterns in the results.
- I will repeat measurements to get more reliable data.
- I will make a conclusion from the results.
You’re going to be a science explorer!
Key Words
- apparent movement
Tap to Learn the Meanings!
- apparent movement: When something looks like it is moving, but it’s actually caused by the movement of something else, like Earth.
Nice work! You’re learning to see how things can seem to move in science.
Big Idea
Shadow lengths change: The length of a shadow depends on where the Sun is in the sky. When the Sun is low, shadows are long. When the Sun is high, shadows are short.
Next time you're outside, try watching your own shadow during the day — it’s a fun way to see the Sun’s movement in action!
FUN QUESTIONS
1. What causes the shadows?
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2. What is the difference between the two shadows?
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3. Which shadow do you think was formed at midday and which shadow was formed in the late afternoon?
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4. Why do you think the shadows are different at different times of day?
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In the next task you will investigate how shadows change in length and direction throughout the day.
Let’s Investigate!
Question: How does the length and position of a shadow change during the day?
Equipment: A sunny day, a stick about 20 cm high, a sheet of white paper, some modelling clay, four stones, a ruler, a marker pen
Safety First:
- Make sure you do not look directly at the Sun as you may damage your eyes.
Method:
- Choose a place in full sunlight where there are no nearby shadows.
- Push the stick into the ground or fix it upright with modelling clay.
- Lay the sheet of white paper flat and mark where the stick stands at 09:00.
- Observe the shadow that falls on the paper and mark the end of it with a marker pen. Write the time beside it.
- Go outside every hour and mark the new position of the shadow, noting the time each time.
- Observe where the Sun appears to be in the sky at each observation. Does it seem to move across the sky?
- Continue until the afternoon, then bring the stick and paper indoors for analysis.
- Join the dots marking the ends of each shadow line to the stick’s base. Use a ruler to measure the length of each shadow and record them in a table.
- If it’s cloudy on the first day, repeat on several sunny days to gather more accurate data.
Follow-up Questions:
Tap to See Answers
- 1: Shadows are longest in the early morning and late afternoon, and shortest around midday.
- 2a: When the Sun is high in the sky, shadows are short; when it is low, shadows are long.
- 2b: The Sun appears to move from east to west, causing shadows to move in the opposite direction.
- 3: The shadow length decreases until midday, then increases again.
- 4: The shadow direction changes gradually throughout the day.
- 5: On cloudy days, sunlight is blocked, so shadows may disappear or blur.
- 6: The Sun’s apparent movement is due to Earth’s rotation, making shadows change in both length and direction.
Brilliant work! You’ve tracked the Sun’s movement like a real scientist.