Lighthouses have played a crucial role as navigational aids for sailors since early human civilization. Although lighthouses have been built as early as BC, the technology at that time was still very backwards.

Due to the limitations of construction methods, people could not build lighthouses in offshore waters. Instead, lighthouses were generally built on the coast or on islands not far from the shore.

A lighthouse is a tall tower-shaped building with lighting equipment installed on the top of the tower. The location of the lighthouse should be conspicuous and have a specific architectural shape, making it easy for ships to distinguish.

At the same time, it should be one of the highest points in the port to increase its visibility. The tower body must have sufficient height to allow the light to be seen by long-distance ships, with a general line-of-sight distance of 15-25 nautical miles. However, the light should not be too high, so as not to be obscured by high clouds.

The tower body is typically constructed of stone or reinforced concrete and can be round, hexagonal, or square. The top equipment includes the lighthouse's light and lens system, usually made of glass or plastic material.

The lens system is an important part of the light as it can focus the light into a strong beam and adjust the direction and range of the light by rotating and tilting. Modern lens systems consist of lenses and reflectors that project light in all directions from the height of the lighthouse.

In very old lighthouses, kerosene lamps were used as the light source, and the lighthouse chief manually operated the clockwork to rotate the lens system that concentrated the light.

The lens system was often floated in mercury to prevent friction. In a modern lighthouse, the lights and clockwork are powered by an external supply, while a diesel-driven generator provides electricity for the life of the lighthouse owner.

The range of a lighthouse is related to two basic conditions: the geographic line-of-sight or initial display distance of the light, which mainly depends on the height of the observer's eyes and the light from the sea surface, and the line-of-sight distance of the light, which mainly depends on the luminous intensity of the light source.

Therefore, in addition to the luminous intensity, the lighthouse light must have a certain height to reach a certain range.

Apart from being a navigation aid, lighthouses have other essential functions. For example, a lighthouse can serve as a safe haven for seafarers during a storm or other emergencies at sea.

Many lighthouses have rescue equipment and communication tools to assist in an emergency. In earlier times, lighthouses were also used as prisons or forts to protect the coastline from foreign invasion.

Lighthouses often appear in literature and art. For example, the novel "The Lighthouse" by British writer Virginia Woolf tells the story of three generations of a family with a lighthouse as the background. Lighthouses are also often used as subjects in paintings and photography.

Despite the development of modern navigation technology, lighthouses remain a valuable heritage of maritime culture and history. With the increasing importance of GPS and other modern technologies in maritime navigation, lighthouses have gradually lost their significance in navigation. However, they remain a place of romance and mystery.

Today, some lighthouses have been transformed into homestays or museums, attracting tourists from all over the world to visit and experience the rich history and culture of these iconic structures.