The Lighthouse of Alexandria: A Night Beacon, Not a Day Signal

One of the Seven Wonders, Designed for Darkness

The Pharos of Alexandria (c. 280–247 BCE) functioned only at night. It was a lighthouse—its purpose was maritime navigation in darkness and low visibility.

Operation

• Fuel: Wood, possibly resinous pitch, or oil (olive, sesame) in a large furnace/brazier at the summit.
• Optics: A curved bronze mirror (or polished metal reflectors) behind the fire collimated the light into a beam. Some accounts mention a lens (unlikely for period).
• Range: Estimated 30–50 km (visible over curvature due to height ~100–130 m).
• Daytime: The structure itself served as a daymark (visual landmark). No light emitted. A statue of Zeus/Poseidon/Helios crowned it.

Structure

• Three stages: Square base (government/military), Octagonal middle, Cylindrical top (lantern).
• Ramp for fuel transport. Hydraulic machine (legend) to lift fuel.
• Stood ~1,500 years. Destroyed by earthquakes (956, 1303, 1323). Ruins used for Qaitbay Citadel (1480).

Why Not Day?

Fire is invisible in bright sun. Smoke might mark position, but the tower's form and height were the daytime signal. The mirror/fire system was for night/overcast.