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Time to switch off

india Updated: May 11, 2008 23:21 IST
Prakash Chandra

We worry a lot about smog, water and noise pollution, but seldom think of light pollution: one of the fastest environmental alterations caused by humans. Orbiting satellites show our planet awash in its own light, which drowns incident light from space. Light literally spills out of everything manmade — from industry to public and residential buildings and roads. Astronomers first noticed it in the 1980s, when the telescope atop Mt. Wilson in San Diego was shut down due to this ‘sky-glow’ or ‘light trespass’ from the town. It was reducing their ability to observe the night sky.

Because of artificial light, songbirds serenade a false dawn, and others migrate prematurely. The moon is a directional reference for birds. On moonless nights, confused migrating flocks have been known to fly into tall illuminated buildings — sometimes killing thousands of them. Nocturnal birds and mammals like bats, badgers, and otters are often discouraged from using their feeding grounds if they are artificially lit. And newly-hatched turtles that aim for the glow of the horizon above the sea find themselves blindly heading inland, instead, to their deaths. Many photosensitive plants, too, are affected by light pollution, mistiming their blooms, or failing to flower at all.

Look around and see how many street lamps — some of them aglow even at midday — toss light energy skywards, instead of down onto the ground. If you are old enough to remember how the sky looked, say, 30 years ago, you’ll probably remember seeing our own galaxy, the Milky Way. But not any more. Of the dozen constellations of the zodiac, five are now ‘invisible’ in most light-polluted skies, while the other seven have many of their stars ‘missing’. If only we realised that better lighting leads to lesser energy needs — ergo, less pollution from unnecessary power stations. Bit by bit, we are losing a direct connection with the universe. For the light from stars takes millions of years to reach us — only to be lost when it touches Earth.