Golf ball and rocket: what they have in common

1. Step 1. Golf ball — uses — Drag. The dimples reduce drag.
2. Step 2. Drag — is used in — Retractable landing gear. Retracting reduces drag.
3. Step 3. Retractable landing gear — is a kind of — Landing gear. Landing gear.
4. Step 4. Landing gear — is part of — Lunar module. Legs.
5. Step 5. Lunar module — has part — Liquid-propellant rocket engine. A descent engine.
6. Step 6. Liquid-propellant rocket engine — evolved from — Rocket. Goddard switched to liquid fuel.

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