One or other forms, the light has been guiding human beings through out their evolution and struggle for existence. The basic form of light we receive from the sun is the source of our food. Thus the life of human beings in this planet depends on the light from Sun. This explains why the Sun became an object for worship in many earlier civilizations. The beauty of sunlight and the rainbow it makes has attracted the creative minds throughout the world. Light in its many variations have been widely used in literature to symbolically describe the emotions of characters.
We, human beings used light for conveying messages. Many civilizations, especially those developed on the banks of Indus River, considered light as a symbol of knowledge. They symbolized light to the knowledge as it removes darkness (ignorance). Invention of fire by our ancestors added another chapter to the human triumph in this planet. They used fire for traveling in night, to keep away wild animals apart from cooking. They feared the lightning and started worshiping it.
For thousands of years we have used light to communicate. Use of light for communication has a long history. In the past, people have used light for basic forms of communication. People used fire and lanterns to convey their presence to the people at distant places at night. These kinds of communications are the primary methods similar to the gestures we use to communicate. Languages we use today can be compared to the coded communication signals.
The welcoming camp fire guided our ancestors’ home. Camp fires were used to keep wild animals at bay. Signal bonfires were lit on hilltops to alarm villages of possible invasion. Marine ships carry powerful lamps for signaling at sea even today. Signaling mirrors are standard issue in survival packs.
Our ancestors used light to effectively communicate their emotions. Mirrors were used to reflect light to get attraction of lovers. Victory in war or in elections was celebrated by supporters of a political leader by holding fire torches. I have seen even protesters holding fire torches marching in front of my houses during my childhood. I used to enjoy the beauty of waving fire torches in darkness.
In eighteenth century, people used signaling lamps, flags, and other semaphore devices. Claude Chappe in 1792, successfully demonstrated transmission of mechanically coded messages over 100 km using intermediate relay stations that resembled modern day regenerators or repeaters.