SME
Grade 5 Science · Earth & Space Science
The sun as a star; brightness and distance
Record how the lit circle grows as a flashlight moves back, to see why faraway stars look dim.
Record and look
8
16
24
32
40
10 cm
20 cm
30 cm
40 cm
50 cm
10 cm
20 cm
30 cm
40 cm
50 cm
Lit circle across (cm)
8
16
24
32
40
The farther the flashlight, the wider the circle: 8 cm up to 40 cm.
The same light spread wider looks dimmer.
Tap a bar at the height you want.
Assumptions
•
Shine one flashlight at a wall. Move it back and measure the lit circle.
•
The same light spreads over a bigger circle, so each part looks dimmer.
•
The sun is a star. Other stars look dim because they are much farther away.
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Two flashlights at different distances
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