Light Pollution: Meaning, Causes, Effects, Solutions

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Light Pollution: Meaning, Causes, Effects, Solutions

Around a century ago, people in large cities were still able to look up and see the stars at night. That is not the case now, due to the phenomenon of light pollution.

What is light pollution?

Light pollution is referred to as ‘pollution’ because it adversely affects the night sky, contaminating the darkness with light.

Light pollution means excess light that obliterates the darkness of the sky at night. It is the reason stars cannot be seen at night in many big cities.

Light pollution refers to the way that electric lights, street lamps and so on leave cities brightly lit right round the clock. Any kind of light can cause light pollution, but electric lights and sodium vapor lamps are the most common.

Causes of light pollution.

1. Electricity. The advent of electricity has enabled us to light our homes brightly through the night. Very often, people act carelessly and illuminate very bright lights at homes and business places – no matter what the hour.

2. 24 hour culture. People are becoming more and more accustomed to restaurants, bars, shops, entertainment and transport networks being available right round the clock – this results in businesses staying lit up 24/7. The effect is cumulative: when one business stays open 24 hours, other businesses often feel that they must follow suit in order to compete for profits.

3. Population density. More and more people have moved to big cities over the last hundred years, and as a result their combined use of light has resulted in more and more light pollution.

4. Brighter bulbs. As bulbs get brighter, the amount of light pollution that they cause increases. Light bulbs should be used for simple illumination, but we have got too much used to over illumination.

5. Street lighting. Street lighting is a safety essential in many areas of the world. These lights help to keep us safe. However, they also create artificial light at night. When super bright street lights are used, they can substantially contribute to light pollution. Light pollution is measured by a scale known as the Bortle Scale, which measures the sky’s brightness.

Effects of light pollution.

1. Skyglow. Skyglow is the name for the reddish-yellow glow in the sky that persists throughout the night due to light pollution in the city below. Another type of glow is known as ‘gegenschein’: this refers to the way that the sun’s rays illuminate gas and dust in the atmosphere causing a wide-ranging glow. Gegenschein is more pronounced in cities where the air is full of pollutants.

2. Disrupted sleep patterns. When it seems that the city never sleeps – neither can we. When the lights are on all through the night, we may find it hard to sleep well or relax. Especially if we live with a street lamp burning outside our window. The pituitary gland in the human body responds to bright lights: when the light is bright, this gland will release chemical signals that cause us to feel awake, and when our surroundings are dark it releases signals that leave us feeling sleepy. Obviously this is useful in non light polluted areas as it helps us to wake up when the sun rises and sleep when it sets. When we live in a light polluted area, however, the activity of our pituitary gland can lead to us feeling awake all the time.

3. Ecological light pollution. Nocturnal and diurnal animals alike may become confused by the presence of light pollution. Light pollution can disrupt the feeding and sleeping habits of nocturnal animals (such as owls and foxes). This can result in populations of these animals dwindling and thus effecting biodiversity in the region as a whole.

4. Impact on astronomy. Observational astronomy is near impossible when the sky is highly light polluted. Further, stargazing can become impossible and real darkness may never be experienced by some city dwellers.

5. Loss of touch with the natural rhythms of life. When we live in a 24 hour culture, with the skies brightly lit all the time, we lose touch with the natural rhythms of life where periods of rest and darkness are alternated with periods of activity. Instead, we are encouraged to be active all the time! This can result in us feeling anxious, stressful and over worked. It is hard to get the rest and repose that we need when everyone else is working or playing hard.

Solutions to the problem of light pollution.

1. Changing the bulbs in street lamps. Street lighting is often lit by sodium vapor bulbs. Lowering the pressure in these bulbs results in a light that is less bright, yet still perfectly fine for illuminating the streets. These less bright bulbs are also less disruptive to species of animals living nearby.

2. Downward facing street lights: These lamps turn light down onto the pavement (and so do their job) but are hooded to prevent it from being scattered into the sky. When the light from the bulb only falls downwards, rather than streaming up into the sky, its effect on light pollution will be negligible.

3. Reducing air pollution. Light pollution is significantly worsened by the presence of dust and polluting gases in the air, as these can be lit up by the city below and cause a fiery glow in the air. Reducing the amount of fumes, sprays and so on that we release into the air will thus help in our fight against light pollution.

4. Switching lights off at night. Turn off unnecessary lights: both at home and in commercial premises. It sounds simple, but turning our lights off at bedtime, whether at home or in a business, is the easiest solution to the problem of light pollution! Our sleeping patterns will then be much more regular and if we want to read in bed, we can use a dim reading light which does not contribute to light pollution.

5. Dark hours. Initiatives such as ‘earth hour’, which encourage people to turn off all of their electrical appliances for an hour every week can significantly reduce the amount of light pollution in the atmosphere. These initiatives have the added benefit of saving electricity and energy – which also help to battle climate change.

6. Cultivating an interest in astronomy. Getting ourselves and our kids interested in astronomy will help us to appreciate the beauty and wonder of a dark sky. If you have never seen the Milky Way, for example, you are in for a treat! Learning to know and love the stars above us – and perhaps engaging in a little observational astronomy – is a great way to motivate ourselves in the fight against light pollution.


Light pollution is a very real problem. Just take a look at an aerial photo of the earth at night and you will see that many of our cities are so light-polluted that they glow incredibly brightly in the darkness. Light pollution is disruptive to both human and animal life.

However, there are several simple ways that we can stop light pollution. So why not take a few positive steps today to diminish the amount of light pollution in your area, and encourage other people and businesses to do the same? That way, we will all be able to appreciate the beauty of a starry sky even if we live in one of the world’s big cities.

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