Light pollution’s wasted energy seen from space

The city of Tucson, in Arizona, US, dimmed its 14,000 streetlights over that period.

“We used a satellite to measure what fraction of the total light emissions are due to the streetlights,” explained physicist Dr Christopher Kyba.

Artificial light has been shown to affect our sleep and our health.

“And late at night, when people are sleeping – that is exactly when we can save a lot of energy,” Dr Kyba, who is based at the German Research Centre for Geosciences in Potsdam.

His light-from-space experiment, published in the journal Lighting Research & Technology, showed that most of the artificial light wasted – by being sent upwards into space, rather illuminating a sign, street or building on Earth – does not actually come from streetlights, but from other sources.

Prof Kelsey Johnson, an astronomer from the University of Virginia, who gave a TED talk about ways to solve the light pollution problem: “We waste tremendous resources on light that goes out into space and doesn’t do anyone any good.”