Hydrometer and gutenberg printing press: what they have in common

1. Step 1. Hydrometer — uses — Archimedes’ principle. A hydrometer floats: the buoyant force depends on the liquid's density, so how deep it sinks shows the density.
2. Step 2. Archimedes’ principle — is used in — Boat. A vessel stays afloat by Archimedes’ principle.
3. Step 3. Boat — evolved into — Sailing ship. Sailing ships grew out of rowing boats.
4. Step 4. Sailing ship — uses — Mercator projection. Navigating along straight rhumb lines.
5. Step 5. Mercator projection — uses — Gutenberg printing press. Maps were printed in large numbers.

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