by Floro Mercene
Beginning in the 17th century, as travel on the high seas increased, major coastal lighthouses were constructed to warn mariners of dangerous rocks, reefs, and currents.
In 1782, the Argand lamp was invented and revolutionized lighthouse illumination with its steady smokeless flame. Then, the Fresnel lens developed in 1822 is a collection of multiple glass prisms. The magnifying lens projects an intense beam of light that is visible up to 28 miles away. With the introduction of automated electric beacons, the lighthouse keeper became all but obsolete.
Many lighthouses are equipped with a horn to help guide ships sailing in foggy weather. These foghorns make their sound by quickly releasing compressed air, which can be heard for distances of up to 13 km. Ship captains can determine their position by identifying distinctive combinations of long and short horn blasts specific to each lighthouse. Some lighthouses are also equipped with radio beacons that transmit Morse code radio signals. These radio signals, which are distinguished by short (dot) and long (dash) combinations, have a range of up to 320 km.
Today, lighthouses use sophisticated illumination methods that use electricity and can be seen a long way away. There are about 50,000 lighthouses that exist in the world. At the end of the 20th century, most of these lighthouses were either automated or abandoned.
Lighthouses that have been automated are used primarily as backups for marine navigation, while many other lighthouses are no longer in operation. Most ships and boats, even the smallest boats these days, have GPS of some sort, VHF radio and other electronics, but those can fail. Most mariners and fishermen still use the lighthouse as a back up on top of their electronic equipment.