{ "content": "

The History and Science of the Lighthouse<\/a><\/h1>

A Lighthouse<\/a> 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<\/a>, warning Mariners<\/a> of dangerous coastlines, Hazardous-Reefs<\/a>, and safe entries to harbors. The most famous ancient example is the Pharos-of-Alexandria<\/a>, constructed in Ancient-Egypt<\/a> around 280 BCE.<\/p>

Optical Innovations<\/h2>

The efficiency of the light emitted was vastly improved in 1822 with the invention of the Fresnel-Lens<\/a> by the physicist Augustin-Jean-Fresnel<\/a>. 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<\/a>.<\/p>

Modern Automation<\/h2>

With the advent of the Global-Positioning-System<\/a> (GPS) and Satellite-Navigation<\/a>, the reliance on visual lighthouses has decreased. Most modern lighthouses are now automated and use Solar-Power<\/a> and LED-Technology<\/a> to operate without a resident Lighthouse-Keeper<\/a>. The United-States-Coast-Guard<\/a> manages many of these aids to navigation today. Research on historic preservation is available via the National Archives<\/a>.<\/p>