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Home » Why We Need Darkness: Paul Bogard at TEDxBratislava (Transcript)

Why We Need Darkness: Paul Bogard at TEDxBratislava (Transcript)

Paul Bogard at TEDxBratislava

In this eye-opening talk at TEDxBratislava event, Paul describes what we call “light pollution,” the overuse and misuse of artificial light at night.


When I was young, I was lucky. I knew a wild sky. I grew up in Minnesota, which is a state in the United States near Canada. It’s a country of forests and lakes, and so my memories of nights as a child are of the moon over water and the stars over pine trees.

I would often take our canoe out onto the water and lie back in the bow under a sky that looks like this. And I would hear the sounds of wolves and loons and frogs. I would see the stars.

I would feel the summer air on my skin. And that imprinted on me. That made me who I am and years later created the book that I wrote, and it’s why I’m here today.

I have known nights as night has been for almost all of human history, which is darkness. Something full of beauty and sometimes fear but always something greater than us, something that filled our souls and inspired our imagination, and, it turns out, something our bodies need for their health.

We’re losing this experience of night’s natural darkness. I’ll give you one example.

In the U.S., more than 80% of the people living there can no longer see the Milky Way. And in Europe, it’s about 60%. We have taken what was once one of the most common human experiences, that of walking out your door and coming face to face with the universe, and we have made it one of the most rare of human experiences.

Why? How? Artificial light.

Now, let me say here that light is good. We like light. We all have light at nights. The question is what kind of light we will have and how we will use it.

Right now, all over the world, in cities and towns and villages, we’re using more light than we need. And we’re using light in ways that harm our health and harm the environment and waste money and energy and take away the stars.

But we’re so used to this kind of lighting, we’re so used to light pollution – the overuse and misuse of artificial light at night – that we almost don’t notice it any more.

Light pollution is spreading all over the world. That’s the bad news.

The good news is that we know how to control it. It is readily within our ability to solve this problem. Let me show what I’m talking about. Three examples.

The first, this is something that’s called “glare.” This is that bright light that’s shining in your eyes, that’s shining in your bedroom, that’s shining straight up into the sky. Glare.

Next, we have “light trespass.” This is when lights from one building shine onto another building. You can see in this image that the light from the building on that side is shining across the street and bathing that house in light, and the students living in that house have had to hang black curtains in the windows so that they can go to sleep at night. Light trespass.

Third, this is something called “sky glow.” That’s what you see on this side of the picture. You might not notice it at first, but these are actually photographs taken from the exact same location.

On the one side, you have what it usually looks like at night. Sky glow. On the other side, you have what it looked like for one night in 2003 when there was a power outage.

So all this together – glare, light trespass, sky glow – creates this. This is what our world looks like at night. And I always say, when I see this image, it’s quite beautiful in many ways.

Light in the context of darkness is often very beautiful. But please know that what we’re looking at here is also an image of waste because almost all the light that we’re seeing in these photographs is going straight up into the sky. It’s not making anyone any safer, it’s not doing any good; it’s just being wasted straight up into the sky.

I want to show you something even more impressive. Because sometimes when we look at these images of Earth from space, these photographs, it looks like, sure, the cities are bright, but if we just get out of the cities, into the countryside, it’s dark there.

It turns out that a team of Italian and American astronomers have created a world atlas of artificial light – of light pollution, essentially. They wanted to show the true extent. They wanted to show us that, at least in the industrialized world, almost none of us live untouched by light pollution.

So, here’s this image of Europe in their atlas of light pollution. You can see the hot white blobs of the cities, where it is the brightest, but look all over the country – light pollution spreads everywhere. We shouldn’t think, though, that light pollution is just a concern for astronomers or people, like me, who love the night sky.

There are many costs to light pollution. There’s a monetary cost, for one thing. Worldwide, more than US $100 billion every year is wasted in outdoor light, mostly that light going straight up that we were just looking at. And that monetary cost is also a cost that we can talk about in terms of burning fossil fuels, in creating greenhouse gases, in contributing to climate change.

Again, no one’s saying, “Let’s not have light at night.” We will have light. The question is how will we have light? How will we light our nights? We need darkness. We need darkness in many ways. Our bodies need darkness, for one thing.

Like all living creatures on Earth, human beings evolved with bright days – we need light – and with dark nights – we need darkness. Scientists are telling us now that our exposure to artificial light at night is harming our physical health in three primary ways.


First, it’s disrupting our circadian rhythms – those 24-hour rhythms that orchestrate our body’s health. We actually have cells in the back of our eyes that have nothing to do with vision. They’re all about telling our body when it’s daylight and when it’s night.

And one researcher I talked to when I was writing the book told me:

“Think of the circadian rhythm as the conductor of an orchestra and your organs as the musicians. If that conductor is confused, all your other organs, all the other musicians will be confused as well.”


Next, our exposure to light at night is contributing to sleep disorders, something that millions of people around the world are suffering from, and more and more people. Sleep disorders are tied to every major disease as well: diabetes, obesity, depression.


Third, and maybe most troubling, our exposure to light at night impedes the production of the hormone melatonin. And a lack of melatonin in our bloodstream has now been linked to an increased risk for breast and prostate cancer.

The World Health Organization now considers working the night shift a probable carcinogen. And what’s the worst kind of light for us to see at night? Blue light. Exactly the kind of light that we’re seeing more and more of in our screens, on our phones and, it turns out, in our street lights as well, which I’ll talk about in just a minute.

But first let me tell you we’re not the only creature that needs darkness at night. I like to say that when we go inside at night, the wide world comes alive outside. More than 60% of invertebrate species – mostly insects – are purely nocturnal, and 30% of vertebrate species are nocturnal. And so many other species are what we call crepuscular; they’re most active at dawn and dusk.

All these creatures have evolved to depend on darkness for their time to move and mate and migrate and feed and be out in the world. When we flood their habitat with our artificial light, we essentially destroy that habitat.

There are so many examples. Let me quickly give you three.

Number one: sea turtles. Sea turtles have evolved to come on the shore to lay their eggs. And when the hatchlings come up out of the sand, they have evolved over hundreds of millions of years to crawl toward the brightest light on the horizon, which for hundreds of millions of years was a beautiful big moon, the moon and the stars on the ocean water.

But now, the brightest light on the horizon is often the hotels, the condominiums, the street lights. And when the little baby turtles go that way, they don’t survive.

Migrating birds suffer greatly from our lights at night. We have in the US more than 400 species of birds that migrate at night, and the number is similar in Europe. Lots and lots of migration at night, and they’re drawn off course by our bright lights. They run into our towers, our wires, our buildings.

And maybe worst of all, they’re trapped in the city, and when the day comes, they fly into the windows. We lose billions of birds every year because of this.

Insects are drawn to our lights. And so what’s so wrong with this? When moths, for example, are drawn to our lights, they’re not doing what they ought to be doing, which is pollinating the plants and flowers that fill our world.

And, in fact, moths and insects are a vital part of the food chain in any ecosystem. So when our lights draw them out of the ecosystem – we actually call it a vacuum, the way that the lights draw them out – we impact up and down the ecosystem. We need darkness for our souls and spirits as well.

For all of human history, we’ve walked outside and looked up and thought about our place in the universe. We’ve thought about our God, our spirituality, our religion. We’ve thought about who we are.

What happens to us as a people when we no longer have this experience? We also need metaphorical darkness, those times of sadness and not knowing, of not understanding what’s happening. These are actually really important times for us in terms of creating us as whole human beings.

Every traditional culture knew this, and their myths always included a time of darkness, going underground or into the dark wood or into the forest. We need darkness for creativity. Think of the writers and the musicians and the dancers, the painters who were inspired by darkness.

I sometimes think of all the young Van Goghs out there who are not being inspired right now because of light pollution. Light pollution wasn’t a problem for Van Gogh in 1888, when he painted the “Starry Night.” The only artificial light we see are the gas lamps burning in the houses here.

Van Gogh, he knew a night that we don’t get to know anymore. He used to write to his brother Theo about the colors of the stars in Paris. And now, we’re lucky if we see any stars in Paris. A friend of mine who is an astronomer decided to update this painting for us as though Van Gogh were alive today, what he might paint if he were living with light pollution, and here it is.

Van Gogh painted a number of beautiful paintings of night time, of the stars. I love this painting, the “Starry Night over the Rhone River” in Arles.

For my book I went to Arles, in the south of France. I wanted to go. You can actually go to the exact spot where Van Gogh stood under the gas lamp to paint this painting. And so I waited until it got dark. I went to the spot – they actually have a poster there that says, “On this spot, Van Gogh painted the painting.”

I got there, and this is what I found. It turns out that …we are afraid of the dark. We’re afraid of darkness. And we’re taught that darkness is bad, and light is good, and more light is better. We hear this a lot when it comes to safety and security, because some light is good, that more light is better.

Now I want to show you two images back-to-back that will at least raise the question of the wisdom of this thinking.

Here in the first image we see a very bright light. It’s what we call in the States a “security light.” They’re on the houses and buildings all over the country. I’ve seen them all over Europe; they’re all over the world. I want you to notice a few things about this image. This very bright light is making it hard for you to see, and it’s casting shadows.

And maybe the worst thing that it’s doing, it’s giving you the illusion of safety. You think, because it’s a bright light, that therefore it’s safe. I’m going to show you another image now, and the only difference with this next image is that the photographer will hold his hand to shield the light.

And when he does that, then you can see the bad guy in the shadows. So this idea that, because some light helps us be safe, more light will make us safer, it’s really not true.

In fact, as we shield our lights, we move from not being able to see the bad guy or the stars, to being able to see the bad guy and the stars.

I really like this idea because there never has been a more important time to be thinking about light pollution and the value of darkness than right now. We’re really at a crossroads when it comes to the way that we light our nights. A big reason why that is: cities everywhere around the world are adopting LED street lights.

Now, LEDs have great promise. They’re programmable; you can raise them and lower them according to the time of night or where they are. They’re far more efficient than electric lighting, which is saving money, saving energy. Fantastic.

But the peril of LEDs is that because they’re more efficient, we just use more of light, we create more light, we worsen the problems that we have. And the type of LED lighting that’s being used most, because it’s the cheapest, full of that blue light that we’re seeing in our screens, and that is the worst for us.

When you think of blue light, think of it this way. In the morning when you wake up, the blue sky’s telling you to get up; when you’re seeing that blue light at night, it’s telling your body the same thing. So the choice is ours.

We can choose how we want to light our nights. Do we want to light our nights like this: wasteful, dangerous, bad for us and for the environment?

Or do we want our lights like this: beautiful, thoughtful, responsible, intelligent lighting? We will have light at night.

The question is: what kind of lights and how much? Toward the end of my research for The End of Night, I went to Dead Valley National Park in California, Nevada, and I found that wild sky that I had known as a child. This is what it looked like, a photograph that I took that night.

And I’ll never forget standing in the desert that night, staring north, watching the stars rise out of the horizon on one side and fall off the edge of the Earth on the other. I could feel the universe revolving over me. And I realized what we’re losing. But also what we can regain.

A world where seeing the Milky Way is part of what it means to be alive on this beautiful planet, and where night’s natural darkness is part of every human life.

Thank you.

For Further Reading:

Dragana Rogulja: How Artificial Light Affects Our Health (Full Transcript)

Rogier van der Heide: Why Light Needs Darkness (Transcript)

Why We Need Darkness to Survive: Diane Knutson (Transcript)

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