S3.12.3 For the adult
Gravity and orbits
Why does the Earth not fall into the Sun, or fly off into space?
What this chapter teaches
Gravity pulls every planet towards the Sun, and a planet moving sideways is bent into an orbit. Without the pull it would fly off in a straight line. Planets far from the Sun have a longer path and move more slowly, so their year is longer.
Three questions to ask
There is no one right wording. Listen for the idea.
- What would a planet do if the Sun's pull stopped?
- Why does Neptune take so much longer than Mercury to go round the Sun?
- What does the ball on the string show about gravity?
After the chapter, the learner can
- Explain that gravity keeps planets and moons in orbit
- Explain why planets far from the Sun take longer to go round
What they copy into their notebook
Gravity pulls planets towards the Sun. A planet also moves sideways, so its path curves into an orbit. Planets far out go slower and have a longer year.