Light Pollution: A Shooting scar in the sky

In a truly dark sky, shooting stars are too numerous to bother wishing on, writes David Owen for The New Yorker. But overly illuminated skies are not just a European or North American problem.

India is also prey to the lesser known but equally severe ‘light pollution’.

Defined alternately as ‘photo pollution’ or ‘luminous pollution’, this matter has long been considered as a soft environmental issue but it has a harsh impact on the lives of all creatures inhabiting the earth.

Light pollution refers to any nighttime artificial light flooding the dark night-sky and scattering lights in places where it is not needed, thus unusually illuminating the nocturnal hours. 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.

Given the rise in urbanisation and the subsequent patterns and forms of lighting and light-use, light pollution is eating into parts of India too.

“India does not really have a good report card on contamination of our surroundings through faulty use of light. It would come after Japan, Eastern United States and some parts of Europe – as the worst light polluted location – particularly the cities as centers. Overall, the view may not look as bad, but, individual cities and towns are falling to this pollution”, says Rathnasree Nandiwada, Director, Nehru Planetarium, New Delhi.

The Hazy Snags

Light pollution creates various problems of light clutter, sky glow, glare and light trespass. Clutter refers to poorly designed groupings of light, which occur in the excess. It generates confusion and causes potential accidents. The prime example of clutter is huge ad boards on roads and clusters of lights on roads, which distract the drivers.

Sky glow is the prominent reason why majority of the urban areas go without citing stars in the night-sky. It is a phenomenon of hugely populated areas where the illuminated light escapes upward into the sky in combination with the poorly directed light. Sky glow is of particular concern to astronomers because it makes difficult to spot even the brightest stars in the sky due to reduced contrast.

  Unaffected Night-sky      Night-sky under sky glow

 Light trespass is something most of us usually experience as a result of poor lighting design. Any extra light falling into places where it is not required (like light from a flash bulb on the street streaming into your room) is also light pollution, which is understood as light trespass.

All the extra light that is scattered to the sky is nothing but a waste of energy resources, which contribute to pollution. Reducing light levels not only aids in bringing down the levels of light pollution but also help in judicious use of light, accelerating cost cutting.


 An illustration depicting light trespass; spilling unwanted light

 The effects on animal and human health and psychology are also a consequence of this problem, which are usually ignored.



                               Glare from excessive light                            An example of sky glow

 The Dark side of Light

Light pollution leads to displacement of humans and other animals from their biological processes and night vision, depriving them of sleep and aiding depression, which poses a health hazard.

Humans and some animals are diurnal in nature. Our eyes and metabolic systems are adapted to consuming only certain amount of light, which we receive aptly from the daytime while we require alternate amount of darkness to keep our normal functions running.

Humans, animals, plants and many microbes follow a circadian rhythm, which is a 24-hour physiological process determining physical, mental and behavioral changes. This rhythm responds primarily to levels of light and darkness in an organism’s environment.


When artificial light affects organisms and ecosystems, it is called ecological light pollution. While light at night can be beneficial, neutral, or damaging for individual species, its presence invariably disturbs ecosystems.

Light pollution poses a serious threat in particular to nocturnal wildlife, having negative impact on plant and animal physiology. It confuses animal navigation; alter competitive interactions, change predator-prey relations and cause physiological harm.

The rhythm of life is orchestrated by the natural diurnal patterns of light and dark, so disruption to these patterns impacts the ecological dynamics.

Hundreds of nocturnal birds get deviated by excessive light in the nighttime which affects their flight, particularly in the migratory season. They circle around the source of light till they drop dead from exhaustion, confounded by the change in the degree of darkness.

Ill-designed lighting washes out the darkness of night, radically altering the light levels and light rhythms. Wherever human light spills into the natural world, some aspect of life-migration, reproduction, feeding, is affected.

                             Source: The World Atlas on Artificial Night-sky Brightness

 A world map showing the density of light pollution. Almost the entire world experiences hazy night cover while Europe, North America, Japan and parts of Asia have highly illuminated night-skies.


Besides disturbing the natural adaptation cycles of humans and animals alike, light pollution robs humans of the scenic starry skies. The over-mounting levels of pollution caused by spill of light into the sky have deprived humans of dark skies at night.

 It is an issue of concern for stargazers and scientists who study and base their research on dark skies.

In highly urban areas, one simply never experiences a star-filled sky at nighttime. It is usually an orange-brown color which is reflected in the night skies.

Sadly, light pollution is not restricted to metro towns alone. Air pollutants tend to scatter light and create an umbrella of light pollution over populated areas.

Even villages where relative levels of light-use are less, stargazing is not as raw as air pollution worsens the minimal degree of light pollution.

Although, there is no national body of the kind in the USA (International Dark-sky Association, US) – there are, however, voluntary bodies involved in astronomy education, like Special Program for Scientific Awareness (SPACE), that encourage students to take part in star-count activities.

A Protected Night Sky Over Flagstaff
Credit and Copyright: Dan & Cindy Duriscoe, FDSC, Lowell Obs., USNO

 The Great Indian Star Count by SPACE

 To scientifically observe how the night sky has altered the urban areas, Delhi-based NGO, SPACE, is organizing a campaign, called The Great Indian Star Count (GISC), in both Delhi and Gurgaon. Over 400 school students will be participating in this 10-day exercise, where data pertaining to night-sky visibility from different areas in Delhi and NCR would be compiled and compared.

 The organization held a similar survey last year, and reported a 5% increase in light pollution in the Delhi-Gurgaon region.


Bringing Back the Dark- Turn down the lights!

Lighting is synonymous to modernization, power, development and progress. To keep a check on light pollution, one cannot put forth a plan asking populations to stop using lights. What has to be done is to enforce a sound and planned use of lighting in both residential and commercial areas.


              Source: Wikipedia  (Image 1)         Source: Wikipedia  (Image 2)                               

Image 1

This drop-lens cobra luminaire allows  light to escape sideways and upwards, where it may cause problems.               

Image 2                      

A flat-lens cobra luminaire which is a  cut-off fixture, is very effective in reducing light pollution                  .

Use of night-sky-friendly light fixtures, which focus light downward where it is most needed than scattering it in all directions, are a key alternatives to bringing down the levels of illuminated light and its consequent wastage. Such fixtures ensure that light is directed below the horizontal, which means less light is wasted through avoiding outward and upward trespass of light.

“Policies for protecting the night sky and limiting the emission of light in upward direction have to come into place, as they are in place in many of the developed countries,” retorts Rathnasree Nandiwada.


 An optimally lit house: Planned lighting controls light spills and trespasses

Light pollution does more than just add that extra glare to our lives. It triggers depression and disturbs the day and night light partition, not to forget it takes away the plain old star-studded skies.

As technology advances, the extent of light pollution will go up. But, one thing about light pollution is that it is not irreversible. As and when we cut down on excessive light being thrown upwards, we will have a mitigation of the light pollution.

If not for the well-being of our natural balance, let’s bring down light pollution to be able to enjoy the stars under which you and I may have spent long slumbers in the sultry summer months and still wish to do.


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