Narrow stone passages and electric fan: what they have in common

1. Step 1. Narrow stone passages — is part of — Egyptian pyramid. Passages inside the mass.
2. Step 2. Egyptian pyramid — uses — Inclined plane. According to a common hypothesis, the blocks were raised on ramps.
3. Step 3. Inclined plane — evolved into — Screw. A screw is an inclined plane wrapped around a cylinder.
4. Step 4. Screw — is used in — Propeller. A propeller “screws” itself into the water, like an Archimedes’ screw.
5. Step 5. Propeller — is part of — Electric fan. The blades.

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