🌙 Gravity and orbits

Unit 1 · Our cosmic neighbourhood · 10 min

Gravity pulls masses towards each other. The Moon is always “falling” towards Earth, but it moves sideways fast enough that it never hits the ground: that is an orbit. The International Space Station circles Earth about every 90 minutes.

Words in this lesson

• 引力 (yǐnlì) — gravity
• 轨道 (guǐdào) — orbit
• 月球 (yuèqiú) — the Moon

Project: Swing a soft ball on a string in a circle (in an open space), feel the inward pull, and think about what happens if you let go.