Air ambulance and optical telegraph: what they have in common

1. Step 1. Air ambulance — uses — Aeroplane. Aeroplanes.
2. Step 2. Aeroplane — includes — Wright Flyer. The first aeroplane.
3. Step 3. Wright Flyer — uses — Railway track. The Flyer had no wheels: it took off along a wooden rail.
4. Step 4. Railway track — inspired — Time zones. Introduced because of railway timetables.
5. Step 5. Time zones — uses — Electrical telegraph. Synchronizing time by telegraph.
6. Step 6. Electrical telegraph — evolved from — Optical telegraph. The electrical telegraph replaced semaphore lines.

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