The end of night

Columbian Exposition in Chicago, 1893 - the dawn of the age of light. Image: PBS.orgOver 60 million Americans have problems sleeping. While insomnia has many causes, one is the use of electric lighting.  Our circadian rhythms developed from the 24-hour rotation of the Earth. At the end of the day, the slowly fading sunlight allowed the brains of our hominid ancestors to prepare for sleep. Around 1 million years ago, hominids began to use fire and congregate around campfires for warmth and safety. Socialization increased. Eventually cooking developed and led to further brain evolution.

The first lamps, made from moss or other plant material and animal fat placed in a natural stone recesses, are tens of thousands of years old. Portable lamps fueled by animal fat, and later oil, were carried by Cro-Magnon into the deep recesses of the Lascaux and Altamira caves where they painted remarkable images of ice age fauna 13,000-18,000 years ago.

First used around 400 AD, candles were an important form of lighting for 1,500 years until the development of gas lighting at the end of the eighteenth century. As noted in A History of Light and Lighting, candles could be linked together to create a spectacle:

In 1761, at the coronation of George III, groups of 3000 candles were connected together with threads of gun cotton, and lit in half a minute. Those clustered below were showered with hot wax and burning thread.

Campfires, oil lamps, candles and gas lamps cast a dim light and

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