Direction for [ Question No: 36 To 40 ] :
Passage I
Light pollution is one of the most rapidly growing threats to our environment. The resultant increase of brightness of the night sky is not only damaging our view of the starry sky, but is altering our perception of dark and moonlit nights and even our physical and mental health. It is only recently that these effects of outdoor lighting have been recognised. Light pollution also indicates wasted energy, since upward directed light does not usually provide useful or intended illumination. Dealing with light pollution and its adverse effects is a complex issue with potential conflicts of interest between the utility providers, environmentalists, astronomers, the lighting industry and various governmental agencies.
Satellite images looking down at the Earth at night have been available since the early 1970s. They measure the light beamed upwards from sources on the Earth's surface but do not give any direct information about the effects of this light pollution on the night sky brightness, as observed by humans on the surface of the Earth, or about its impact on the visibility.
These effects may be calculated by including a physical model of the effects of scattering of light by air molecules and other small particles. Maps that show this calculated sky brightness have now been prepared for the entire world and provide a vivid record of growth of light pollution in both developed urban areas and densely populated areas.