Astronomy is the oldest science, with roots extending more than five thousand years to the building of Newgrange, Stonehenge and similar structures. It is a key part of mankind's cultural inheritance which attracts people towards science and into a scientific way of thinking. Concepts and ideas derived from astronomical theories and observations are often found in fields far removed from science and mathematics, and are frequently the central focus of works of art, literature, music, and film. The "inspiration" of astronomy extends into many areas of our lives, including philosophy and religion, and provides us with a unique, and rapidly changing, perspective on our place in the Universe.

  The work of professional astronomers can often be highly technical; but a few minutes spent searching the internet or a glance at the magazines on display in any newsagent will demonstrate its wide popular appeal and visual impact, and the fact that astronomy's basic concepts are easily explained and accessible to everyone. Until now, such access has included the view of the night sky, when stars, planets, comets and galaxies have been visible to challenge the mind and induce the questions and rational thinking about the world that gave rise to civilization. Countless scientists and engineers can trace the impetus of their careers in science and technology to a fascination with the night sky during childhood, with no less an impact on the humanities. However, what was once the world's grandest free show has become almost literally a shadow of its former self, capable of being seen only by those fortunate enough to live in the country or able to travel to a dark, remote site far removed from city lights.

  The intellectual stimulus provided by access to dark skies cannot be underestimated, whether to a child or a grown-up. The French physicist and Nobel Laureate, Jean Perrin, put it well: "It is indeed a feeble light that reaches us from the starry sky. But what would human thought have achieved if we could not see the stars?"

  To draw a veil across this aspect of humanity's cultural heritage—the slow march of the bright planets against the "fixed" stars, the daily cycle and seasonal advance of the constellations, the monthly phases of the Moon and its changing aspect through the year—is to deprive us of a source of inspiration that has operated for thousands of years. The loss of such an imagination driver is likely to have profound cultural consequences, leaving us all the poorer.

  The problem of light pollution has been accentuated in recent years by increased economic growth, urbanization and road-building programmes, and by a fashion which seems to dictate that domestic and civic amenities should be brightly lit after dark. Everyone is familiar with the problem, having been dazzled at one time or another by an intense light source such as a neighbour's security light or a stadium's floodlights, but few consider ways to mitigate it, or whether regulations should be passed to reduce the unnecessary, unsociable waste of poor lighting.

  Night lighting is a necessary part of our lives, enabling people to extend their activities after sunset and to provide security for public and domestic dwellings alike. However, poor lighting gives rise to light pollution. It comes in many forms: light trespass (eg when a neighbour's so-called security light shines into your garden or through your bedroom window); sky glow (the illumination of the atmosphere by unshielded or inappropriately directed lights that limit our view of the cosmos to a handful of the brightest stars); glare (the dazzling effect of floodlights or security lights which prevents us from making out objects such as people or vehicles near the source); and light waste (eg lights left on when no-one is present). Poor lighting costs money by wasting energy; it creates safety and security problems through glare; and it deprives us of our view of the night sky.

  Public safety and security at night require a certain amount of illumination, and there is evidence that improved lighting leads to cost-effective reductions in crime. However, detailed studies show that the benefits of improved lighting are often attributable to increased community pride and confidence—both day-time and night-time crime decreasing together. Bright lights help to allay the fear of crime, but do little to prevent crime itself. Similarly, glare from improperly directed lights detracts from security in the same way that a driver's ability to see an object in the road ahead is impaired by an oncoming car's headlights.

  Awareness of light pollution and interest in its adverse consequences has been growing almost daily on the national and international stage. In the United States, the International Dark-Sky Association has been coordinating efforts since 1988 to inform private citizens and local and federal government officials on the advantages of good lighting practices. A noteworthy example is the city of Flagstaff, Arizona, home to the historic Lowell Observatory. As a result of intensive efforts to pursue night-sky friendly lighting policies, Flagstaff was recently awarded the title of the world's first Dark-Sky City.

  Similarly, the City of Bisei, Japan, has recently passed a light-pollution ordinance to ensure compliance with the official policy to preserve dark, star-lit skies. Spanish authorities are protecting the night sky over the island of La Palma, famous for its astronomical observatory; and in February 2002 the Czech Republic became the first European country to enact national legislation to eliminate light pollution. These efforts are strongly supported by the International Astronomical Union. Closer to home, the Irish Minister for the Environment and Local Government, Mr Martin Cullen TD, has noted (Dâil Ireann, Debates, 9 October 2002) the emerging interest internationally in the concept of light pollution and of concerns to reduce artificial light in the outdoor atmosphere for reasons of public amenity, health, energy saving and otherwise, and that environmental impact assessments should require estimates of the expected residues and emissions from proposed developments that expressly cover the impact of artificial lighting. In the UK, the Campaign for Dark Skies, initiated in 1993 by the British Astronomical Association, has significantly raised awareness of the problem, leading the influential Institution of Lighting Engineers to issue its "Guidance Notes for the Reduction of Light Pollution".

  In summary, light pollution is simple to avoid, but has become so widespread that most of us have become inured to the problem. Put simply, we are used to inappropriately shielded lights in parks and around public buildings, to lights left on when no-one is present, and to upward-directed light from streetlights shining uselessly into space. When we visit the country or view the night sky from a dark site abroad, we are often astonished to see hundreds of bright, twinkling stars. Some of us may pause, briefly enjoying the spectacle, others may reflect on how small and seemingly insignificant is the Earth compared to the wider Universe beyond.

  The advantages of a regulatory framework to reduce and eventually eliminate light pollution are manifold. It will enhance our environment and preserve our view of the night sky—fully half our field of vision. It will restore a powerful source of inspiration, not just for professional and amateur astronomers but for the whole community, one that has driven ideas and intellectual activity for thousands of years. It will save electricity costing hundreds of thousands of pounds per unnecessary megawatt per year, and help the UK and local authorities to meet increasingly stringent targets on energy conservation, for example the UK's international obligations under the Kyoto protocol. To the extent that saving electricity reduces both greenhouse gas emissions and the production of atmospheric particulates that scatter light, the elimination of light pollution also produces a classic "win-win" scenario. Reducing light pollution will help amateur astronomers to pursue their hobby, and help to avoid potential unnatural biological, environmental or behavioural effects on plants and animals living in brightly lit areas.

  A strategy for the elimination of light pollution should begin with a census of lighting installations in each area and a systematic application of proven guidelines. The replacement of light fitments is a costly and time-consuming enterprise, so the primary initial effort should focus on developing appropriate guidelines for new developments. Such an approach has been used successfully in other spheres. When existing light fittings or fixtures are to be replaced, however, even after 10 or 20 years, the new, tighter regulations should be applied. In this way, elimination of light pollution will be seen as a cost-effective, energy-efficient programme with an appropriate long-term vision, and the new regulations will encourage local authorities to create district plans and development policies that are truly sustainable.

  Finally, "Right Light" policies, ie lighting that is necessary and sufficient for use, will attract positive publicity to towns and cities that adopt them, and enhance the country's image on the world stage. No-one loses out. The hackneyed phrase "Vision 2020" could perhaps be aptly applied to a programme for the reduction and eventual removal of light pollution.