The immediate past century saw an unprecedented advancement in science and technology and an acceleration of economic well being. At the same time it also experienced an ever more polluted world, specially an ever-increasing environmental pollution which has emerged as a major global concern for the very survival of human beings as well as all other life forms and the balance of ecosystem. When man of this modern era, especially in the developed world, is busy to make life easier and more comfortable, light pollution is emerging as a serious menace surreptitiously. This write up intends to elucidate from geographic and environmental points of view how light pollution is having its awful and appalling effect on human health, astronomy and ecosystem. Light pollution, also known as photo pollution or luminous pollution, refers to the obtrusive, misdirected or misused light created by humans generally resulting from an inappropriate application of exterior lighting products. It comes in several modes each with its own negative effects including sky glow, glare and light trespass. Light pollution is basically a side effect of industrial civilization. Its sources include building exterior and interior lighting, advertising, commercial properties, offices, factories, street lights, LED screens, electronic billboards, illuminated sporting venue etc. Geographically, it is most severe in highly industrialized, densely populated areas of North America, Europe and Japan and in major cities of the Middle East and North Africa like Dubai and Cairo. In North America from east coast to west, from Texas up to the Canadian borders there is very significant global light pollution. This is not only true in cities but also in suburbs and in rural areas where street lamps and other sources of light obscure the view of constellations, meteor showers and even the planets. Human health: A variety of adverse health effects may be caused by light pollution or excessive light exposure. These include increasing headache incidence, worker fatigue, medically defined stress, and increase in anxiety. Some studies reveal that lengthy daily exposure to moderately high lighting leads to diminished sexual performance (Mc Cohen, 1988). Several published studies also suggest a link between exposure to light at night and risk of breast cancer, due to suppression of the normal nocturnal production of melatonin (Mac Gregor, 2006). In 1978 Cohen et al proposed that reduced production of the hormone melatonin might increase the risk of breast cancer citing "environment lighting" as a possible causal factor. Astronomy: For astronomy and science the impact of light pollution has been even mere dramatic. Astronomers require observation of extremely faint objects that can be made only with large telescopes. But sky glow resulting from light pollution reduces the contrast between stars and galaxies in the sky itself, making it more difficult to detect fainter objects. The light from these objects can be lost at the very end of its journey in the glare of our own sky. About 90 percent of all Americans live under skies that are "affected" by light pollution while roughly half cannot see the Milky Way from their homes. Mankind has throughout history looked to the stars to try to understand the events around them. The stars above us are a priceless guide -- not only for astronomers but for all humans. Ecosystem: All life forms, both flora and fauna, exist with natural patterns of light and dark. So disruption of these patterns influences many aspects of animal behaviour. Light pollution can confuse animal navigation, alter competitive interactions, change predator-prey relations, and influence animal psychology. This type of pollution around lakes prevents zooplankton, such as daphnia, from eating surface algae, helping cause algal blooms that can destroy the lakes' plants and lower water quality. Lepidopterists and entomologists have documented that night-time light may interfere with the ability of moths and other nocturnal insects to navigate. Night blooming flowers that depend on moths for pollination may be affected. This can lead to decline of plants that are unable to reproduce, and change an area's long term ecology. Migrating birds can be disoriented by lights on tall structures. The Fatal Light Awareness Program (FLAP) works with building owners in Toronto, Canada and other cities to reduce mortality of birds by turning out lights during migration periods. Nocturnal frogs, salamanders and other species are also affected by light pollution. Since they are nocturnal, they wake up when there is no light. Light pollution may cause salamanders to emerge from concealment later, giving them less time to mate and reproduce. Many wildlife won't even go near an area that has bad lighting. Also many species will simply stop reproducing if habitat destruction from overly bright lights becomes too severe. It currently threatens all Florida sea turtles. Apart from the above impacts, it also wastes incredible amount of valuable natural resources and money. Hundreds of millions of barrels of oil...and hundreds of millions of tons of coal are just used in this respect every year throughout the world. It does little to increase night time safety, security or utility. Rather it produces only glare and clutter, costing more than one billion dollars annually in the US alone. After seeing through all the above mentioned negative effects, movements have already been launched against this pollution. For instance, since the early 1980s, a global Dark-Sky Movement has emerged, with concerned people campaigning to reduce the amount of light pollution. A number of organizations have also been formed in response to rising light pollution including 'International Dark Sky Association' and 'SELENE -- Sensible Efficient Lighting to Enhance the Night-time Environment'. Reduction strategies: Reducing light pollution is not a difficult job at all. It just needs to make sense and awareness of the problem and to act to counter it. On an individual level, people can help reduce this pollution. However, some control strategies are suggested here: * All exterior lighting should be ordinance compliant. * Outdoor lights should be kept on only when needed. * Dawn to dusk lighting should be strictly avoided. * The wattage of our bulbs should be reduced. * Choosing well-shielded lighting fixture. * Utilizing light sources of minimum intensity necessary to accomplish purpose. * Turning lights off using a timer or occupancy sensor or manually when not needed. * Improving light fixtures so that they direct their light more accurately towards where it is needed, and with fewer side effects. * Evaluating existing lighting plans, and re-designing some or all of the plans depending on whether existing light is actually needed. Concluding remarks: To sum up, light pollution is a wasteful habit that provides nothing positive to society, rather it threatens us in a number of very fundamental ways. Like any other form of pollution, it disrupts ecosystems,causes adverse health effects, obscures the stars for city dwellers and interferes with astronomical observations. Under these circumstances, light pollution control has become a matter of urgency. First we should think that we are going to be part of the problem. But we can also be a part of its solution. Each one of us can contribute to the reduction of light pollution in our own way. We should keep in mind that curing light pollution saves money while reducing glare and sky glow detrimental to human health, astronomy and environment. So let us think of it seriously, do the duties and discharge responsibilities normally and morally bestowed on us from our respective platforms towards a light pollution free environment. Muhammad Selim Hossain is studying Geography and Environment at the University of Dhaka.