Light pollution interferes with the breeding patterns of animals and insects. How can we look to the stars if we can’t even see them?

Two sky vistas. A starry night in a dark place and a black night over a lit city.

Two night scenes. On the left, stars fill the sky over the Coconino National Forest. (Credit: Coconino National Forest, U.S. Forest Service.) On the right, a dark sky covers a brightly-lit Los Angeles. (Credit Douglass Clem, CC BY-SA 3.0.)

When was the last time you were outside and the only bright lights came from the night sky?

Did you bask in the glow of the moon, the spectacle of the Milky Way or the dancing colours of the Northern Lights — the Aurora Borealis? If so, you were lucky.

Light pollution has dramatically diminished how much of the night sky we can see. And evidence is increasing of the negative effects of artificial light on humans and the natural world.

In short, light pollution is washing out our view of the night sky. In Europe, light pollution is increasing 6.5% each year and over 10% in North America. Brightness caused by artificial lights is doubling every seven years worldwide.

There are different terms for types of light pollution. Glare causes visual discomfort while skyglow brightens night skies in urban areas. Clutter is described as numbers of different artificial lights bunched together and light trespass is defined as light shining where it is not needed or intended.

The brightness of our lights darkens our future.

White LED lights emit light across the entire visible spectrum, which are the most disruptive for humans and wildlife. The yellow glow of old style sodium lighting, now considered more nature friendly than white LEDs, is often excessively bright.

Striking images from earth observation satellites illustrate the shrinking space on our planet that is free from artificial lights.

So how does light pollution affect us? The impact on the environment and public health is only beginning to be understood.

Scientists report that light pollution interferes with the breeding patterns of animals, insects and the migration of birds. Marine ecosystems are affected as well as terrestrial ecosystems. There is mounting evidence that the profound changes created by light pollution are even diminishing biodiversity. There are many examples.

Newly hatched turtles are now drawn towards bright artificial lights, usually away from the water, rather than heading for the safety of the ocean illuminated by dimmer moonlight.

The life cycle of insects is disrupted by artificial lights leading to what is called a ‘worrying’ decline in insect numbers. Even the blossoming of plants is affected by LED lights which are bright enough to create a physiological response causing negative effects on plant growth and the behaviour of pollinators.

The Milky Way seems to be melting away.

Artificial lighting also interferes with human sleeping patterns. The wave lengths of certain lights disrupts our circadian rhythms — the 24-hour cycle which governs our body’s internal clock. Insomnia is one result.

The environmental consequences of light pollution are being monitored and quantified in numerous studies, but the aesthetic, and some would say cultural, impact is immense. Simply, one third of humanity can no longer see the Milky Way, the stars that make up our galaxy.

Contemplating the night sky is something every human and every civilisation on our planet has done. Stargazing connects us with a tradition that creates a sense of wonder and awe and is thousands of years old.

The stars and planets are the source of creation myths of cultures through history.

The philosopher Plato, who gazed at the heavens in ancient Greece 2,400 years ago, was passionate about watching the stars. Plato even believed that our eyes were formed for the study of the night sky and that we could learn from stars and planets as well as admire its majesty.

Can we turn the night sky back on?

Can light pollution be reversed and allow our generation to see a clear sky full of stars? Campaigners for darker skies point out that artificial light can be used in a ‘dark sky friendly’ manner.

Organisations like the International Dark Sky Association offers practical suggestions for conserving darkness in urban areas. Saving remaining darkness, they say, needs policy support which requires awareness as well as regulations.

The practical solutions on offer include dimming streetlights in early hours, motion sensors to activate lights only when they are needed and intelligent light design. Commercial and private outdoor lighting can easily be designed—or re-designed—to illuminate downwards and sideways rather than upwards.

The International Dark Sky Association also lists official dark sky areas around the world to visit for dramatically dark skies.

Dr. Stuart Clark, the British astrophysicist who studies the universe and writes about the history of astronomy, offers advice to stargazers. Start by allowing time for your eyes to adjust, he says, a process that can take up to an hour.

“Don’t raise your gaze immediately… depending on the atmospheric conditions and the sensitivity of your eyes, you will be able to see some three or four thousand stars, each one a distant sun in its own right. Each one a possible home to a family of planets,” Clark said.

Astronomers remind us that even in cities, a bit of resourcefulness can allow urban inhabitants to do a spot of stargazing, which is also a proven way to reduce stress.

Find a star chart in a book or online, learn about the brightest stars of the season in your hemisphere. Then retreat to the centre of a large park, a garden or a balcony above the street lights. A pair of binoculars or a telescope is helpful but even with the naked eye, the brightest stars and planets will be visible.

They are the same stars and planets that Plato and all of our ancestors gazed at seeking knowledge and inspiration. Just look up to connect with our universe.

Questions to consider:

  1. Have you looked at whether artificial lights in your neighbourhood are well designed?
  2. Where are the darkest skies you have been to visit? Were you able to spot specific stars, planets or meteor falls?
  3. Can you spot the main stars and constellations in your hemisphere?
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Tira Shubart is a freelance journalist and media trainer based in London. She has produced television news and trained journalists across four continents for international broadcasters, including BBC News, Canadian Broadcasting Corporation and Al Jazeera, over several decades.

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Educators' CatalogWhen the lights black out, the night sky turns on