Thursday, June 6, 2013

Night is vanishing.

Light pollution has become worldwide.
By
Dr. Nitish Priyadarshi

Glittering stars some 20 km outside Ranchi.


Light pollution with fog in Ranchi city.



                         Scattering of light on the sky of Ranchi city.


                  Over-Illuminated tree. Other example of light pollution.


For most human history, the phrase “light pollution” would have made no sense. Imagine walking on Ranchi (Jharkhand, India) street on a dark night some 50 years back when it was thin population. People carrying torches and lanterns in the Ranchi  Street were common. Even the rickshaw pullers use to attach small lantern in front or back of rickshaws. Cycles were fit with dynamos. Only few houses were lit by gas during power cut and there were few public gaslights in the street.

The natural night sky light comes from starlight, zodiacal light (sunlight scattering from dust in our solar system), and airglow (atoms and molecules in the atmosphere that glow in the night after absorbing solar radiation) in roughly equal quantities. Even a small amount of artificial light interferes with this delicate balance, changes the colour of the sky, and overwhelms the starlight. Light pollution has become a worldwide problem as it is gradually diminishing the capacity to observe the stars. This new kind of waste originates cultural, environmental and even energy impacts, with unforeseeable consequences.

The night sky in the country looks remarkably different than the sky view near a city. More stars are visible and brighter, and in some remote areas, the Milky Way galaxy extends across the sky from east to west. In contrast, lights in the city illuminate night skies, hiding many of the stars. Outdoor lighting that interferes with the natural landscape is called light pollution. As urban areas grow, so does this type of pollution.

Few days ago I got the chance to stay in a village for some research work. Village was without any power supply. In night while sleeping outside I viewed the sky. I was overwhelmed to see most of the glittering stars above me which I missed in my city. Viewing stars in my city is interrupted due to light reflection on the sky.

None of this is to say that electric lights are inherently bad. Artificial light has benefited society by, for instance, extending the length of the productive day, offering more time not just for working but also for recreational activities that require light. But when artificial outdoor lighting becomes inefficient, annoying, and unnecessary, it is known as light pollution. Many environmentalists, naturalists, and medical researchers consider light pollution to be one of the fastest growing and most pervasive forms of environmental pollution. And a growing body of scientific research suggests that light pollution can have lasting adverse effects on both human and wildlife health.

For three billion years now, life on this Earth has existed with a regular and dependable day-night schedule to the illumination levels in the environment. This regularity has become ingrained into the DNA of species up and down the evolutionary tree. It regularizes basic and fundamental biological activities across species from plants to us humans. It is the height of apathetic ignorance and insanity that we expect other living organisms on this planet to just "adapt" to newly created lighting schedules of our convenience. The effects of light pollution on plants and animals in the environment are numerous and is becoming more known. In general, the most common action is that light pollution alters and interferes with the timing of necessary biological activities. But for approximately half of all life, those nocturnal species that begins its daily activities at sundown, our artificial lights at night seriously constrain their lives, exposing them to predators and reducing the time they have to find food, shelter, or mates and reproduce.

Now most of humanity lives under intersecting domes of reflected light, refracted light, of scattering rays from overlit cities and suburbs, from light-flooded highways and factories. In most cities the sky looks as though it has emptied of stars. We have grown so used to this pervasive orange haze that the original glory of an unlit night-dark enough for the planet Venous to throw shadows on earth- is wholly beyond our experience, beyond memory almost.

Light pollution—the luminous orange glow that haloes cities and suburbs—threatens wildlife by disrupting biological rhythms and otherwise interfering with the behavior of nocturnal animals, new research shows. Now a movement is under way to turn off the lights, or at least turn them down, for the sake of all creatures that frequent the night.

Among the mammals alone, the number of nocturnal species is astonishing. Light is a powerful biological force, and on many species it act as a magnet. The effect is so powerful that scientists speak of songbirds and seabirds being “captured” by searchlights on land or by the light from gas flares on marine oil platforms, circling and circling in the thousands until they drop. Migrating at night, birds are apt to collide with brightly lit tall buildings, immature birds on their first journey suffer disproportionately. Insects, of course, cluster around streetlights, and feeding at those insect clusters is now ingrained in the lives of many bat species. Some birds-blackbirds and nightingales, among others-sing at unnatural hours in the presence of artificial light. Scientists have determined that long artificial days-and artificially short nights- induce early breeding in a wide range of birds. And because of longer day allows for longer feeding, it can also affect migration schedules.

Artificial lighting seems to be taking the largest toll on bird populations. Nocturnal birds use the moon and stars for navigation during their bi-annual migrations.When they fly through a brightly-lit area, they become disoriented. The birds often crash into brilliantly-lit broadcast towers or buildings, or circle them until they drop from exhaustion.

Its benefits come with consequences- called light pollution- whose effects scientists are only now beginning to study. Light pollution is largely the result of bad lighting design, which allows artificial light to shine outward and upward into the sky, where it’s not wanted, instead of focusing it downward, where it is. Ill- designed lighting washes out the darkness of night and radically alters the light levels-and light rhythms- to which many forms of life, including ourselves, have adapted. Wherever human light spills into the natural world, some aspect of life-migration, reproduction, feeding- is affected.

Medical research on the effects of excessive light on the human body suggests that a variety of adverse health effects may be caused by light pollution or excessive light exposure. Health effects of over-illumination or improper spectral composition of light may include: increased headache incidence, worker fatigue, medically defined stress, decrease in sexual function and increase in anxiety.

Scientists have warned that children who sleep with a light on during the night could be ruining their eyesight. US scientists found that children who sleep with a light on are significantly more likely to grow up short-sighted and having to wear glasses, when compared to children who sleep in the dark.

Light pollution is a side effect of industrial civilization. Its sources include building exterior and interior lighting, advertising, commercial properties, offices, factories, streetlights, and illuminated sporting venues. It is most severe in highly industrialized, densely populated areas. Specific categories of light pollution include light trespass, over-illumination, glare, light clutter, and skyglow. A single offending light source often falls into more than one of these categories.

Light trespass occurs when unwanted light enters one's property, for instance, by shining over a neighbor's fence. A common light trespass problem occurs when a strong light enters the window of one's home from the outside, causing problems such as sleep deprivation or the blocking of an evening view. Congested areas like Upper Bazar, Ratu road, Harmu road, Ashok Nagar, Main road, Circular road in my Ranchi city is causing problem of light pollution in the form of light trespass.

Over-illumination is the excessive use of light especially during the marriage season or in festivals when Ranchi city and other parts of the India are exposed to over-illumination. Over-illumination is responsible for million barrels of oil per day in energy wasted.

Skyglow refers to the glow effect that can be seen over populated areas. It is the combination of all light reflected from what it has illuminated escaping up into the sky and from all of the badly directed light in that area that also escapes into the sky, being scattered (redirected) by the atmosphere back toward the ground.
There are ways to reduce light pollution, starting in your own neighborhood. Make sure outdoor lights reflect downward in what are called fully-shielded fixtures. Also consider exchanging high-wattage bulbs for dimmer ones and selecting warm-white lights with low emission of blue light. A great way to save energy and reduce trespassing light is to turn off outdoor lights unless needed.

By now the effort to control light pollution has spread around the globe. More and more cities and even entire countries, such as the Czech Republic, have committed themselves to reducing unwanted glare.

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