Light pollution is not just a waste of money, argues astronomer Darren Baskill in this week's Green Room. He says badly designed lighting is also having an impact on the environment and our health, as well as denying millions of people the right to enjoy the beauty of the night sky.
Think of light pollution, and many will think of suffering astronomers.
Our desire for night-time lighting in a 24-hour society seemingly justifies any amount of wasted light
While the orange smog of night-time light pollution is the most graphic demonstration of wasted light obliterating our view of the stars, it is the financial, environmental and human cost of light pollution that is truly astronomical.
Light pollution is wasted artificial light; light that shines where it is neither needed nor wanted. Most light fittings waste a large fraction of the light they produce. More than 300 megawatts worth of light is wasted skywards from UK streetlights alone, at an annual cost of about £100m ($190m).
Even the most modern streetlights divert light away from the street, and shine light directly into the sky. This makes the night sky brighter and our streets dimmer, a "double whammy" for a cycling astronomer like me, suffering the evening challenge of avoiding yet another puncture caused by debris hidden in the gutter.
One medium-sized coal-fired power station is required to solely generate that wasted energy, which results in a million tonnes of carbon dioxide pollution being pumped into the atmosphere each year. Include inefficient lighting from homes, businesses, churches and sports facilities, and you begin to comprehend that the wastage is on a massive scale.
And light pollution is getting rapidly worse; according to the Campaign for the Protection of Rural England (CPRE), light pollution in the UK increased by a staggering 24% between 1993 and 2000, making Britain the third most light-polluted country in Europe.
Our desire for night-time lighting in a 24-hour society seemingly justifies any amount of wasted light - which has had tragic consequences.
In Oxfordshire a man was killed when a pub floodlight blinded a car driver. In Australia, ill-directed lighting surrounding an airport caused a fatal air crash.
Intrusive nuisance lighting can cause stress, leading to deterioration in health, heart attacks, and even thoughts of suicide.
Exposure to light at night may also increase the risk of cancer. Dr Chris Idzikowski, director of the Sleep Assessment and Advisory Service, says: "[It] could lead to a disruption of sleeping patterns, hyper-activity and may have a negative impact on a child's health."
Inefficient lighting has a detrimental impact on wildlife too, disrupting natural feeding and breeding cycles. A survey in Toronto found more than 2,000 migrating birds of 89 different species dead beneath brightly lit skyscrapers. Bats, moths and other insects such as glow-worms are also adversely affected.
The most common justification for lighting, however inefficient, is security, and the naive belief that "the brighter the light, the better" prevails. Visit any DIY store, and the shelves are brimming with 150W, 300W and even 500W floodlights.
However, the government's home security website states that such lighting "...is unfortunate, as in many locations this is the most inappropriate form of lighting available".
When you consider that the Smalls lighthouse (situated more than 20 miles off the coast of Wales) has a 35-watt bulb that produces a beam of light that is visible for 21 miles, you can understand why.
Ironically, such blindingly bright so-called "security" floodlights can hide criminal activity in their glare, and because the lights are frequently triggered by cats on a night-time prowl, neighbours soon learn to try to ignore them.
Research into street lighting by the UK Home Office showed that "better lighting by itself has very little effect on crime", suggesting that lighting can help everyone see their surroundings - including criminals.
The Government has introduced the Clean Neighbourhoods Act (2005), which aims to make light nuisance subject to criminal law. Unfortunately, the Act includes a long list of inexplicable exceptions. While a home owner can now be fined for installing obtrusive lighting, a bus station cannot. An increasing number of inefficiently floodlit buildings, especially churches, may also escape control.
While some local councils understand the problems of light pollution, others exacerbate the problem. Stockport City Council recently installed new street lighting that shines light into homes at five times the recommended levels.
Things are different in other countries. Light pollution laws exist in the Czech Republic, Italy, Chile and parts of the US. In 2005, the City of Calgary finished replacing all 37,500 street lights with efficient lighting, saving $2m (£0.9m) per year - which will offset the replacement costs in just six years.
Elsewhere, street lighting in Rome dims after midnight, reducing lighting costs by 40%, and in the US, the Long Island Power Authority converted all their outdoor operational-yard lighting to efficient fixtures.
These all prove that you can have light without light pollution. So please, make sure your home or business lighting only shines where it is needed and with appropriate power, without wasting light upwards into the sky, or outwards into neighbouring homes. Walk around your lights, and make sure they are not visible from beyond the area that needs to be lit.
Likewise for street-lighting, where dimming technology should be used wherever possible - it halved energy costs on the M65 while reducing visual stress to drivers.
These small steps will save significant amounts of energy and money, reducing carbon dioxide emissions, and improve our view of both the streets and the sky. While many people have heard of light pollution, regrettably few make the small effort needed to eradicate it.
Everyone needs lighting, including astronomers, but that need should not be used as an excuse to be unnecessarily inefficient on a massive scale. No-one should be denied the right to view, explore and be inspired by the night sky.
Dr Darren Baskill is an astrophysicist at the University of Leicester, working on the European XMM-Newton Space Telescope mission
He is also a member of the Campaign for Dark-Skies, a group initially set-up by amateur astronomers to encourage the use of efficient, responsible lighting
The Green Room is a series of opinion pieces on environmental issues running weekly on the BBC News website.