Arc lights had been used in lighthouses for several years when Thomas Edison began seeking a way to improve them. Arc lamps use two rods of carbon arranged so that their tips are almost touching. When sufficient electricity is sent to each, the current jumps between them and causes the carbon to become incandescent. Although carbon burns very slowly, over time the rods erode and have to be replaced. The year was 1881 when Edison embarked on a solution and the result of his success spread around the globe to both light and inadvertently curse the darkness.
Edison set out to solve several problems: create a sufficient vacuum to prevent the carbon from oxidizing, find more suitable material to serve as a filament and reduce the scale needed to produce an artifical electrical light source. After securing a German pump that could produce a high vacuum, Edison tested 6,000 different materials until a carbonized cardboard filament remained lit for 170 hours. It was the first practical incandescent light bulb. Of course, Edison’s real achievement lay in his design of a system that enabled many lights powered from a common source to be switched on and off independent of each other. This idea has evolved into the modern power grid. During the more than one hundred and twenty years that have followed, the incandescent light and its halogen, neon and florescent descendants have proliferated into every corner of the world.
For thousands of years prior to this, humankind had lived in darkness after sunset with only the light of burning wood, wax or oil to provide illumination. Our connection to the night sky during this period ran very deep. From all but the largest cities, people venturing outside at night would see a black sky punctuated by the glow of over five thousand visible stars, the planets and the Milky Way arcing overhead. It filled our forebears’ minds with wonder, reminded them that they were surrounded by the Universe and found its way into their most profound beliefs.
Today, electricity is plentiful, night lighting is ubiquitous but the night sky that was visible throughout all of human history is no longer with us. It’s been replaced by a soft glow from our urbanized areas. Now, for over two thirds of the world’s population, views of the Milky Way and all but the brightest stars and planets are hidden behind domes of artificial daylight. These bright blankets continue to expand in all directions limiting our personal connection with the Universe to an ever dwindling number of remote locations.
When night lighting extends beyond its purpose, it’s called light pollution. It comes from poorly designed streetlights. Billboards, decorative lights, and poorly shielded security lights but street lighting is the largest contributor. Some cities and communities are joining with astronomers to work together and address their local situation. For example, Los Angeles now recognizes three problems associated with light pollution: light trespass- when glare shines into neighboring windows or the eyes of an automobile driver; night sky loss – when glare is directed into the sky above – and energy waste, estimated to be hundreds of millions of dollars annually for the United States, alone. Organizations like the International Dark Sky Association of Tucson, Arizona, have also formed to reduce the problem though educational outreach and legislative lobbying.
Belgium astronomer Josch Hambsch, who produced the remarkable picture that accompanies this article, pursues his astrophotography projects and variable star studies from his light polluted backyard observatory. However, his vacation travels occasionally include a visit to a dark site in Namibia and earlier this summer Josch made another trip.
If you take a camera and anchor it to a fixed location, like a tripod, aim it at the sky and open the shutter for several minutes, the stars will form tails due to the spinning of the Earth. This picture was produced using this method. It represents an entire night, looking south from Namibia. 128 separate five-minute images were combined to produce this result. The stars form circles about the south celestial pole but the background glow is not from light pollution. It is produced by the combined light from some of the Milky Way’s four hundred billion stars. This image was exposed with a Canon 20D camera and a 12-24mm f/4 Sigma zoom lens, set to a focal length of 12mm.
Josch also combined the individual images into an animation that shows the stars’ motion during the night and the spectacular arcing of the Milky Way as it sets.
Written by R. Jay GaBany