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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.

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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.

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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.

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