Friday, February 12, 2010

Light and the Bright Green City

By Alex Steffen
February 9, 2010

It's become a common slide at conferences: a map of the Earth at night, with the wealthier and denser areas shining brightly. Africa seen at night is largely dark, and this is often the point of the slide: look at how much energy some people have access to, and how little others do (which is true: almost 90% of Africans lack ready access to electricity, according to the World Bank), and, by inference, what gaps in economic prosperity persist.

But these maps don't actually display prosperity, or even energy use: instead, maps of brightness illustrate light pollution and energy waste. The blazing lights our satellites photograph while whizzing above us in their orbits, well, that's light that's serving no useful purpose (unless you want to think of our glowing cities as a form of art meant for distant eyes). Light seen from space is bouncing off illuminated surfaces, or being shone directly from bulbs aimed up. Neither is helping us on the ground see our cities full story.

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