S3.12.2 For the adult
How big and how far
How far apart are the planets? Could I make a model of them with a string?
What this chapter teaches
A scale turns real distances into model distances by dividing. On a string where 1 m stands for 100 million km, the planets fit in 45 m. Planet sizes would be specks, so a model of sizes needs a different scale from a model of distances.
Three questions to ask
There is no one right wording. Listen for the idea.
- If 1 m of string stands for 100 million km, how far along is a planet that is 500 million km away?
- Why does a book show the planets big and close together?
- Where would you put the Sun and the first four planets if you made the string model in a yard?
After the chapter, the learner can
- Use a scale to turn real distances into model distances
- Make a scale model of the planets along a long string
What they copy into their notebook
A scale says how much real distance a piece of the model stands for. Model distance = real distance ÷ scale. 1 m = 100 million km puts Neptune 45 m out.