The History and Science of the Lighthouse
A Lighthouse is a specialized structure, typically a tower, designed to emit light from a system of lamps and lenses. It serves as a critical beacon for Maritime-Navigation, warning Mariners of dangerous coastlines, Hazardous-Reefs, and safe entries to harbors. The most famous ancient example is the Pharos-of-Alexandria, constructed in Ancient-Egypt around 280 BCE.
Optical Innovations
The efficiency of the light emitted was vastly improved in 1822 with the invention of the Fresnel-Lens by the physicist Augustin-Jean-Fresnel. This design allowed for the concentration of light into a powerful horizontal beam, visible for over 20 miles. Before this, lighthouses relied on inefficient reflectors and open fires. For more on the physics of these lenses, visit Britannica.
Modern Automation
With the advent of the Global-Positioning-System (GPS) and Satellite-Navigation, the reliance on visual lighthouses has decreased. Most modern lighthouses are now automated and use Solar-Power and LED-Technology to operate without a resident Lighthouse-Keeper. The United-States-Coast-Guard manages many of these aids to navigation today. Research on historic preservation is available via the National Archives.