Turn off the lights

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Turn off the lights

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In July 1938, physiologist Nathaniel Kleitman of The University of Chicago emerged from a cave with an overgrown beard, after having spent 32 calendar days underground. During this time he tried living on a 28-hour cycle but failed to adapt himself to the new biorhythm, indicating that the human body contains a powerful clock clinging to the 24-hour cycle.

Plants and animals, as well as humans, are strongly influenced by sunlight. Paddy rice, perilla and cosmos require daily exposure to sunlight to bloom and bear fruit during autumn. Last March, teams from the Roslin Institute in Britain and Japan’s Nagoya University found that birds begin to sing more often to attract potential mating partners in the spring, when they receive more light. Some birds, such as quails, burst into song in the spring, because cells on the surface of the brain trigger hormones when the days get longer, expanding male testes as a result.

The average temperature of the Earth’s surface is around 15 degrees, and plants go through the process of photosynthesis, thanks to light energy from the sun. However, night is also important to living organisms. In the dark, male fireflies expose themselves to females. Small and weak animals hunt at night to hide from their predators.

Human-made light sources also impact the order of the night. As seen from a satellite, the strong light from the Earth’s night dazzles our eyes.

Living organisms are used to day and night, and seasonal change throughout the long history of the Earth, but if they receive more light at a strange season or time, they will naturally fall into confusion.

Artificial light is a murky subject for humans as well. Perhaps two-thirds of the world’s population can no longer see the Milky Way at night. Australia is losing sight of the Southern Cross. The stars depicted on its flag are no longer visible to the naked eye.

Last February, a new study by Israeli researchers revealed that females exposed to artificial lighting such as lamps or television screens at night have a 37 percent higher risk of breast cancer than females living in the dark with no lamps.

Recently, experts at Michigan State University pointed out that light from buildings, cars and vinyl covering, such as that used in farming, disorients animals. Light pollution is invading their lives by day and by night, as it includes light reflected from the sun.

In recent years, more and more lights have been turned on to create vibrant cityscapes. As we develop technology designed to shed light only where it’s necessary, we can reduce light pollution as we wish.

It is high time that we have some consideration for other living organisms that require more darkness, rather than striving to satisfy people’s needs and convenience.


The writer is a JoongAng Ilbo reporter who specializes in environmental issues.

By Kang Chan-soo [envirepo@joongang.co.kr]

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