Outdoor

Nasa highlights light pollution with dramatic picture

The earth at night showing New Delhi and Lahore as bright spots on the globe
The bright metropolis of the Indian capital New Delhi is top right. Below it is Lahore in Pakistan. In the centre, the Himalayas divide India and Pakistan from Tibet. The square shadow on the right is a solar panel on the International Space Station. The picture was taken with a Nikon D5 digital camera with a 28 millimetre lens. Copyright Nasa/JSC

THE UNITED States’ National Aeronautics and Space Administration has today unveiled a dramatic photograph which demonstrates the current extent of light pollution.

The image – taken by a member of the crew aboard the International Space Station and released to Lux Review and other media today  – shows India, Pakistan and Tibet at night.

It highlights the sharp contrast in artificial light between the sparsely populated Tibetan plateau—the so-called ‘roof of the world’—from the fertile and densely inhabited plain of northern India and Pakistan. 

The India capital of New Delhi is a bright metropolis as is Pakistan’s second largest city, Lahore.

Also visible are the lesser India cities of Chandigarh, Ludhiana, Jalandhar and Amritsar. 

The region is home to more than 400 million people and one of the most densely populated regions on Earth. 

For astronauts, this is also one of the few areas where geopolitical boundaries come to life at night, as the high-pressure sodium security lights make clear the international border between India and Pakistan.

The rugged mountains of the Himalayas divide India and Pakistan from Tibet. 

Nighttime light emissions are increasing in most countries worldwide, but which types of lighting are responsible for the increase remains unknown.

A recent study found that street lighting – long suspected of being the major culprit of light pollution – only contributes to a fifth of the problem.

The team of scientists asked the city of Tucson, USA, to intentionally alter its streetlight output over 10 days, so that the change in emissions could be observed by satellite. 

The researchers found that streetlights operated by the city were responsible for only 13 per cent of the total radiance (in the 500–900 nm band) observed from Tucson from space after midnight. 

If the City of Tucson did not dim its streetlights after midnight, the contribution would be 18 per cent. 

When streetlights operated by other actors are included, the best estimates rise to 16 per cent and 21 per cent, respectively. 

The scientists – who reported their findings in the journal Lighting Research & Technology – say that the results suggest an urgent need for consideration of other types of light sources in outdoor lighting policy.

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