Hot air balloon and greenhouse: what they have in common

1. Step 1. Hot air balloon — evolved into — Airship. A steerable balloon.
2. Step 2. Airship — has part — Propeller. Air propellers.
3. Step 3. Propeller — evolved from — Archimedes’ screw. The first propellers by Smith and Ericsson were a variation on the Archimedes’ screw.
4. Step 4. Archimedes’ screw — is used in — Irrigation. The Archimedes’ screw lifted water for irrigation.
5. Step 5. Irrigation — is used in — Greenhouse. Watering plants.

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