What is the function of navigation lights?

We have all seen harbor lights, whose main function is to guide ships to sail at night. In the 5th century BC, the Greeks knew to use it to represent ports. The most famous ancient lighthouse was built by Pharaoh in Alexandria, Egypt. It stands at the end of an island and is made of white marble. It has many layers and is very beautiful and spectacular. There is an ancient miracle in the world-the colossus of Rhodes, which is also a lighthouse. This colossus is generally regarded as the image of the sun god, spanning the population of Port Rhodes.

All early lighthouses (including those built by the Romans) were towers made of stone or gravel. Its main function is to guide the ship to sail, enter the port safely or avoid running aground and running out of rocks. At dusk, a special tower keeper burns charcoal or coal at the top of the tower with a capacity, and then switches to oil lamps or steam lamps for lighting. This kind of lighthouse is also common in the seaport of China. Quanzhou in Song and Yuan Dynasties was an international seaport city, with many ships moored. Pagoda of Six Harmonies in Quanzhou Port used to be a lighthouse, but now it has become a precious historical relic.

The lighthouse was not improved until the18th century. For example, the Eddie Si Tong Lighthouse in Britain was originally made of wood structure, then changed into oak and iron structure, and finally changed into concrete structure in 1759, with candles as the light source and a simple metal mirror reflecting the candle light behind it. This kind of lighthouse with steel structure or concrete structure can still be seen in some places on the west coast of the United States.

1780, a man named Argander invented a fuel device suitable for lighthouses, but this device was abandoned by the end of 19 because acetylene gas was better. 1822 someone made a lens, which can gather the light beams and then project them. This kind of mirror is used in the lighthouse to improve its lighting. This kind of compound lens has been used until now.