Lighthouse: why towns need it and how it works

Real world Why lighthouses are still needed

Ships carry most of the world's trade. Even with satellite navigation, ships need visible markers near dangerous coasts, in case electronics fail, and to confirm their position. Lighthouses, buoys and beacons are called aids to navigation.

A first-order Fresnel lens, made of rings of glass prisms, at Point Reyes Lighthouse, California. Photo: Frank Schulenburg, CC BY-SA 4.0, via Wikimedia Commons

Real world How a lighthouse works

Early lighthouses burned wood, coal or oil. In the 1820s, the French physicist Augustin Fresnel designed a lens made of rings of glass prisms that bends light into a strong, narrow beam. Fresnel lenses made lights visible many kilometers out to sea and were used around the world.

Each lighthouse has its own "signature": a pattern of flashes and a color, printed on nautical charts, so sailors can tell which light they are seeing at night. Painted stripes or colors help identify it by day.

Portland Head Light on the rocky coast of Maine. Photo: King of Hearts, CC BY-SA 4.0, via Wikimedia Commons

Real world From keepers to automation

For generations, lighthouse keepers and their families lived at remote stations, trimming wicks, winding clockwork and cleaning lenses. During the 20th century, electric lamps and automatic controls replaced most keepers. Many old lighthouses are now museums, while modern LED lights do the work.