Glasses and railway track: what they have in common

1. Step 1. Glasses — evolved into — Telescope. The first telescopes were assembled by spectacle makers.
2. Step 2. Telescope — is used in — Optical telegraph. Signals were read through a telescope.
3. Step 3. Optical telegraph — evolved into — Electrical telegraph. The electrical telegraph replaced semaphore lines.
4. Step 4. Electrical telegraph — is used in — Time zones. Synchronizing time by telegraph.
5. Step 5. Time zones — was inspired by — Railway track. Introduced because of railway timetables.

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