World ‘losing night’ due to light pollution

Bright lights, big cities: Densely populated areas are brightly lit. © NASA Earth Observatory

Should we be less afraid of the dark? A new survey shows that light pollution is increasing, posing risks to us and our environment. Campaigners are trying to reverse that trend.

When was the last time you saw the Milky Way? Unless you live in the countryside, your chances of glimpsing all the stars above are slim. And according to a new study, they are only going to get slimmer.

A US government satellite has been taking regular snapshots of Earth at night in order to track our use of artificial outdoor lights. The resulting images of the illuminated planet are beautiful, but the picture they paint of our society is less pretty. They reveal that our use of lights has increased by more than 2% every year since 2012.

Trends vary across the world. Light use in wealthy countries has stayed quite steady. In some developing nations, like India, it has skyrocketed. It has only decreased in a handful of places, like war-torn Syria and Yemen. Overall, the study’s authors conclude that we are experiencing a “loss of night”.

The invention of electric light in the 19th century changed the world. It created more time for work, travel and socialising. But its overuse leads to problems, too. Light pollution has been found to mess with animals’ habitats, the cycles of trees and our own health. It also blots out the stars.

This has triggered a backlash, known as the “dark-sky movement”. Campaigners encourage governments to turn street lamps off late at night, introduce intelligent lighting systems and so on.

They organise events like National Dark-Sky Week, for which people turn out their lights at the full moon. “Astrotourists” flock to special areas that restrict light pollution in order to see stars.

However, these measures have caused anger in their turn. In urban areas, people often associate dark nights with crime. MPs have campaigned against light-cutting policies for this reason. While studies do not agree on whether they actually encourage crime, the fear that people feel is real enough.

Fear of the dark has deep evolutionary roots. Our ancestors were threatened by predators who roamed at night, so they learned to stay near light. As this study shows, that instinct has not left us.

Dark prospects

Too right, say some. Artificial light is the most valuable invention of all time. By letting us see in the dark, it brings us fun, comfort and practical benefits; it gives relief to our deepest anxieties. Imagine going back to our ancestors’ way of life, when the sunset effectively ended the day. It would be miserable.

But think of what we have lost, reply others. The dark actually sharpens our other senses. Paradoxically, it makes us more aware of our surroundings. And it allows for stargazing, which connects us to the universe we belong to. Artificial light lets us see things, but the dark makes us truly perceive them.

You Decide

  1. Do you think you waste light?
  2. Is day better than night?


  1. Try to name the most brightly lit places in the map above.
  2. Spend one night this week trying to use as little artificial lighting as possible. How easy did you find it, and would you try it again? Write down your thoughts in a one-page report.

Some People Say...

“We are all in the gutter, but some of us are looking at the stars.”

Oscar Wilde

What do you think?

Q & A

What do we know?
Researchers have been using satellite images of Earth at night for at least 25 years. This satellite, the Suomi NPP, was launched in 2011. The map released as part of the new study was stitched together from the images it has taken since then. Sources of non-artificial light, such as natural light reflecting off snow, were filtered out.
What do we not know?
NASA’s satellite cannot detect LED lights, which are becoming more widespread (especially in wealthy countries), as they are energy-efficient. This means that light pollution is actually rising even faster than the study’s calculations suggest. Experts had assumed that the rise of LED would lead to a fall in the lights visible in the satellite images. They were shocked to find out that this is not the case.

Word Watch

The authors of the online World Atlas of Artificial Night Sky Brightness estimate that 60% of Europeans and 80% of North Americans cannot see the Milky Way at night.
Animals’ habitats
For example, pollution disrupts pollination by nocturnal insects and can send birds who migrate by night off course.
Our own health
The science here is complex, but excessive exposure to light is known to mess with our circadian rhythm (aka body clock). Such disruptions have been linked to a range of issues, from obesity to cancer.
Intelligent lighting systems
These are lights that adapt their brightness to factors like the weather and the number of people about. Think of a football stadium that dims its lights after the game has finished and the crowds have left.
Special areas
There are a number of certified Dark Sky Places in the UK, including Galloway Forest Park in Scotland, Exmoor National Park in England and the Brecon Beacons National Park in Wales.
Fear of the dark
There are various official terms for this, including nyctophobia, lygophobia and scotophobia.

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