Common Misconceptions about Dark-Sky campaigning



  • Does the CfDS want everyone to turn their outdoor lights off?

    No, definitely not!
    We all need lighting! The CfDS just wants people to make sure that their outdoor lights all shine downwards, and not upwards or outwards where they cause so many problems.

  • New street-lights do not contribute to light pollution

    Unfortunately, new streetlights can often cause more light pollution than the older lights they replace!
    Light pollution is not solely caused by the old Low Pressure Sodium lights. Mathematical modelling shows that the main cause of light pollution is from light emitted at or just above the horizontal (mostly in the first few degrees). Modern high pressure sodium luminaires often have bowl-shaped lamps, or are tilted by up by 5° - both result in light being emitted a few degrees above the horizontal, and so both contribute significantly to light pollution.

  • Full cut-off (non-polluting) street-lights illuminate a smaller section of the road

    This is a very common misconception. It is simply not true that you need more street-lights if you use full cut-off units. Take a look to the image to the below, which shows the hood of the lighting unit at different positions over the bulb, and the areas which are illuminated.

    The bottom three lighting units are all full cut-off. Such a light as in the bottom right case would illuminate a smaller section of road, but not so the bottom-middle case. Indeed, in the bottom-left case, the bottom of the bulb is just above the bottom of the hood, so no light can escape upward although the light can shine horizontally outwards to infinity. Such a light however, would also shine into neighbouring homes, disturbing people's sleep. So the CfDS recommends the ideal street-light to be the bottom-middle; there is no upward shining light, although there remains a good spread of light.
    Other arguments against this misconception are:

    • Even if full cut-off lighting did illuminate smaller section of road, taller poles can be used
    • The City of Calgary are currently replacing all their old street-lights with EnviroSmart full cut-off Street Lighting?
    • In many places, they are putting full cut-off lighting units on the same columns
    • On the M5 motorway, every five old style lighting units have been replaced by FOUR full cut-off lights. (i.e. futher apart!)

    Full cut-off street-lights don't need to be closer together, as it is the optics and the street-light height that determine the spread of the light.

  • There are more suicides in winter than summer

    It is well known that living within the Arctic circles can cause psychological stresses on inhabitants, due to the 24 hour daylight in summer, and 24 hours darkness in winter. Suicide rates in Finland are among the highest in the world. Many assume incorrectly that 24 hours of darkness is the most stressful time, but apparently not.
    The thesis of Dr Helina Hakko states: "A significant excess of total suicides was found during spring/summer (May-July) and a significant trough during winter/spring (December-March) months."
    The 24 hour daylight appears to cause more stress and suicides than at any other time of the year. For more information, please look at Dr Helina Hakko's PhD thesis

  • More lights will decrease crime

    There is no direct link between highter levels of lighting and crime levels.
    In 1996, the National Institute of Justice in the USA conducted an assessment of crime and violence, and published their work in Preventing Crime: What Works, What Doesn't, What's Promising. The study found little support to support the misconception that "brighter is safer", and even suggested that poorly designed lighting might actually increase personal vulnerability. The report states:

    • "The problematic relationship between lighting and crime increases when one considers that offenders need lighting to detect potential targets and low-risk situations. Consider lighting at outside ATM machines, for example. An ATM user might feel safer when the ATM and its immediate surrounding area are well lit. However, this same lighting makes the patron more visible to passing offenders. Whom the lighting serves is unclear."

    Other studies on light and crime include those in Clark's "Outdoor Lighting Principles for Australia" (crime was cut drastically during a period of power cuts); the success of IDA's "Dark Campus" program (Dark Campus Programs Reduce Vandalism and Save Money); the Ramsey and Newton studies for Home Office/CPU (no link between lighting and crime); the West Sussex experience in the period in the '80s when many street lights were turned off late at night.
    Also there is an idea that an active amateur astronomer is likely to be more of crime deterrent than a light, so encourage the former by turning off the latter!
    More details on the CfDS' standpoint on lighting and crime can be found on our lighting and crime page.

  • We should accept light pollution as part of living in a city

    No - unless you also want to accept that £100 million (see our economics page) of your money (if you live in the UK) should be wasted per year on producing light that never hits the ground. Neither light pollution, nor wasting large sums of money is acceptable, wherever you live.
    The City of Calgary in Canada has proved this by eliminating light pollution from all their street-lights, while the Czech Republic has passed a prevention of light pollution law throughout the entire country.

  • It is just astronomers that want dark skies.

    This is not so. In the International Dark Sky association, for example, less than 50% of the members are astronomers; the majority being made up of the medical profession, bird-watchers, wildlife watchers, environmentalists, crime prevention officers,lighting engineers, etc.

  • Surely the problem of light pollution is just too big for us to make a difference?

    Wrong! This is often heard, but can be proven wrong with two arguments and plenty of examples. Admittedly, light pollution is not a problem that can be solved overnight - but we can and are making a difference.
    Politicians are beginning to listen to the problem of light pollution, and convincing just one MP may lead to a city-wide change - just look at the example of Calgary, where they are retro-fitting their street-lights city-wide.
    The important thing is the momentum the CfDS have got going - a vast amount of people have now heard of, and are doing something about, light pollution. If you tell 10 people about light pollution, and convince them to do something and tell others, 6 steps down the line and over a million people are doing something about it! (10 to the sixth power is a million!)
    Let's also look at examples from the past. 50 years ago, the City of Sheffield had a serious smog problem caused by its huge steel industry (many other major cities in the UK had similar problems, including London). That all changed in the 1960's, when the law only allowed smokeless fuels to be used. Another example is the ozone hole - CFCs have been successfully banned rapidly world-wide. And the level of pollution from cars is being reduced dramatically with recent legislation.