Week of wonder: In defense of darkness

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This is Part I of On Point's Week of Wonder.

Earth needs darkness just as much as it needs light.

But human light pollution is pushing back the dark, which is changing the natural world, and could be hurting us, too.

Johan Eklöf, scientist and bat researcher. Author of The Darkness Manifesto: On Light Pollution, Night Ecology, and the Ancient Rhythms That Sustain Life.

Emily Fobert, research fellow at the University of Melbourne who studies the impact of light pollution on marine species.

Geoff Goins, visitor services supervisor at New Mexico’s Capulin Volcano National Monument, a certified Dark Sky Park.

Keith Krueger, Pinal County, Arizona resident and citizen scientist whose neighborhood doesn’t have streetlights.

Casey Rodriguez, dark sky advocate in Pittsburgh, Pennsylvania.

Zach Thompson, dark sky advocate with the International Dark Sky Association in Lincoln, Nebraska.

Part I

MEGHNA CHAKRABARTI: I’m Meghna Chakrabarti. This is On Point.

INGRID HEDBOR: Hi, this is Ingrid Hedbor in South Hero, Vermont on the shore of Lake Champlain. It’s just about midnight. The moon is rising up through the trees and there’s still a few constellations. You can see stars. It’s a really clear night. It’s the first time in a few nights that it’s really clear. The geese have just come back, you can hear them here and there. But otherwise, it’s really quiet. It’s beautiful. Serene.

CHAKRABARTI: That was Ingrid Hedbor, in South Hero, Vermont. And this is Casey Rodriguez in Pittsburgh, Pennsylvania.

CASEY RODRIGUEZ: So I recently started a night shift job at a retail place stacking shelves. And it’s gotten me out a lot more at night. It’s about 3 a.m., I’m sitting in a strip mall parking lot. And it’s cold. (LAUGHS) Air’s nice and crisp. But the sounds travels pretty far. I hear the occasional passing truck or car on I-30, I-376. When it quiets down, I can hear the whirring of the machines from the supermarket. Not much wildlife here. It is the middle of March.

With the strip mall parking lot lights never turning off, it’s kinda hard to ever get a glimpse of stars. They recently switched to new LED lights which are more power efficient but they really block out the stars and it’s a shame. I noticed it first when I would visit family, that there’s just so much else out there that I typically don’t see. Be it at work or my apartment, it’s just blocked for miles around that you can’t see.

I can actually tell the direction that the downtown area is because the sky is brighter on one horizon. Not entirely, because it’s kinda bright all around. It’s also noisy. Just before recording this, I get interrupted by a train passing by. I thought it was clear and a garbage truck came barreling past. It’s convenient living in the city but you sacrifice a lot, I’ve learned.

CHAKRABARTI: Jenny Ward in Greenville, Maine.

JENNY WARD: (SNOW CRUNCHING) I’m walking out onto the frozen surface of a pond that’s located in northern Maine. This place where I’m at right now was recently protected by the Appalachian Mountain Club as its Maine Woods International Dark Sky Park. And tonight is an amazing night to be outside. There are no clouds. It is well into night. And the stars are amazing.

I look around me and they start on one side of me and they go to the other. It’s like I’m not under them, it’s like I’m in them. The stars are literally dripping from the sky. And they are so dense. Some of the familiar constellations and stars that are familiar to me, I’m having trouble picking out, because the stars are so bright. (BREATHING) It’s very quiet and still. Winter still has a pretty strong grasp on this region. But things are starting to change. And you can see that in the stars as they start to shift from winter sky to summer sky. It’s a great night to be out.

CHAKRABARTI: Johan Eklof joins us now and he's in Ulricehamn, Sweden. And Johan, what is nighttime like where you are?

JOHAN EKLÖF: It depends on the year. Us living in Scandinavia, we have these very long nights during the winter, but not as long as in summer. But where I live in a bit far, a bit outside, a smaller town, I can relate to the last person speaking here.

Watching the stars, it's not as good as that, but still, I can see the Milky Way and I can just stand outside in my garden sometimes and just feeling a bit small and insignificant under this sky that just goes on.

CHAKRABARTI: You research bats, and I believe you're a professor at Stockholm University as well, and you've written this new book, which has really captivated my mind.

It's called The Darkness Manifesto: On Light Pollution, Night Ecology, and the Ancient Rhythms That Sustain Life. Johan, why does darkness need a manifesto now?

EKLÖF: First, I'm very often mixed up for this guy in Stockholm, which has, he has the same name as me, but he's a marine biologist.

CHAKRABARTI: Oh, okay.

EKLÖF: I'm a batologist from Gothenburg. Okay. So I did my research in Gothenburg. Just to clarify that, he emailed me the other day and say, "Hey, everybody calls me." But about the book, I've been doing research on bats for 25 years and being out a lot during the evenings and a few years ago, we realized that the bats often live in churches, at least here in Sweden.

And in the '90s, all the churches started to use floodlights. We have some hundreds or even thousand-year-old church buildings, and of course the municipality want to shoo off these buildings. And so they put floodlights on them, and we started to investigate what happens to the bats and it turned out they either move or they just starve to death.

So in 30 years' time, half of the bats living in church is actually gone. And when realizing that, I thought that this is not just about bats. It's not about killing bats; it's about killing the knight. And that must mean something to animals, to plants, and even to ourselves. So that's what I started to write a book about darkness.

CHAKRABARTI: Yeah. So the bats in the Swedish churches, it's not that they moved somewhere else, it's just their overall populations did drop precipitously, is that what you're saying?

EKLÖF: Yes. We don't know for sure that they just didn't move anywhere else, but there are similar studies in England suggesting that these bats actually stay put as long as they can. And as the night gets shorter and shorter, they eventually starve to death.

CHAKRABARTI: And it didn't have to do, every time we talk about bats, I always think about white nose disease. Would, did that play a role here? Or was the light the really the main issue?

EKLÖF: The light is the issue.

CHAKRABARTI: Okay.

EKLÖF: The white nose syndrome is a huge thing in America, but in Europe it's not the same problem. Perhaps it comes from here. So the bats are immune in Europe.

CHAKRABARTI: Okay. So we'll talk more about animals and how keenly they rely on darkness. But I did want to hear from you a little bit, Johan, about humans and what you think we humans lose out on as our world becomes evermore illuminated. Do we miss out on something?

EKLÖF: We do, as we heard from the voices in the beginning here. It was like very slow speaking, whispering voices trying to experience the night. And while in one case there was a lot of stars, but in another case, he was complaining about the LED light just blocking everything.

And there is something about the night sky that we, perhaps we don't realize that we miss it every day, but if we think about it, we want to see these stars. There's so many, they're just one fifth of the population. Population can actually see the milky way nowadays and somehow this connects us to history and to our forefathers, seeing the same stars and things like that.

That is, of course, very hard to measure. It's just a feeling of missing out. There are so many other things with the darkness that we actually need.

CHAKRABARTI: Yes. But I didn't realize that only one fifth of human beings on earth right now are able to see the Milky Way. Is that what you said?

EKLÖF: Yeah. At least in America, in Europe.

CHAKRABARTI: Oh, okay. In the United States and Europe as well. Okay. And so people may live their entire lives not having seen the night sky as it is without interference from human created illumination.

EKLÖF: Yeah. There is this story about the when the electric light went out in Los Angeles a few years ago. That the people starting to call the police because there was some weird lights in the sky, turned out to be the Milky Way. First, I didn't think that was really true. It was a bit exaggerated. But now, just the other day, I heard that people were calling in asking about when Jupiter and Mars were very close together on the sky.

So even here, people were actually calling the police wondering, "What is this? Are they drones?" So there is something about this that we're so unfamiliar with the night sky nowadays. So we think it must be something weird going on.

Part II  

CHAKRABARTI: Today we're speaking with Johan Eklöf. He's a bat researcher and author of the new book "The Darkness Manifesto: On Light Pollution, Night Ecology, and the Ancient Rhythms That Sustain Life." Now about those ancient rhythms, human caused light pollution around the world not only affects terrestrial species, it affects aquatic species as well. And to that point, we spoke with Emily Fobert, who's a research fellow at the University of Melbourne in Australia, and she studies how humans impact underwater ecosystems, especially when it comes to artificial light. And her work was inspired by a research trip she took in 2017.

EMILY FOBERT: I went to French Polynesia with a colleague. And it's a relatively remote island, but there's all these hotels with overwater bungalows and lights shining right down on the reef. Some of them even have, you know, the glass floors and the bungalows with the lights directed on to the reef below. The tourists can look at the fish at night. And, you know, I've heard that there's impacts of light pollution on a lot of terrestrial animals and humans, for sure.

So just seeing all that light pollution in the marine environment made me realize that it's something we haven't been looking at, but it's probably an issue there as well.

CHAKRABARTI: So back at the lab, Emily decided to see whether light pollution had an impact on a specific underwater species Clownfish. There was orange and white fish that make their homes in anatomies on coral reefs.

FOBERT: So I had a bunch of clownfish in the lab and breeding pairs, so a female and a male each in their own aquarium kept track of how many eggs they're laying, how frequently they were laying them. And then I put lights on half of them. So half of them were mind control. So they still experience 12 hours of daylight and 12 hours of complete darkness. And then the other half had 12 hours of daylight and 12 hours where they are exposed to a dim light at night.

And that's kind of equivalent to what you might expect from a source of lights on marine infrastructure. So on a pier or over a water hotel that might have lights on it shining downwards. And then I monitored how many of the eggs actually hatched in both the control and the light conditions. So what I found is when the fish had 12 hours of daylight and 12 hours of darkness at night, we had about 80% match success. So 80% of the eggs crashed. It's pretty normal to have high mortality in early life stages of fish because they have thousands of eggs.

But then when I put the lights on at night so that when they're exposed to low levels of light at night, 0% of the eggs hatched. So none of them hatched. Pretty stark results. So I removed the lights and I continued to monitor them for another couple months. And essentially, as soon as I remove the lights, the next batch of eggs from the same cache would hatch. So 80% hunch rate again.

So it was very clearly the light that was inhibiting that hatching process. A lot of coral reef fish eggs actually hatch a couple hours after sunset. Translucent larvae are not very visible at night. There's not as many predators around. So they hatch, they get off the reef really quickly in the cover of darkness. Clownfish. Most fish. Most organisms on earth meet darkness for various reasons. But there's still not a ton of research done on light pollution in the marine environment.

So, yeah, there's a lot of questions still out there, but no doubt that animals need darkness. Whenever anyone asks me what I do and I mention, you know, like pollution, fish. There's like, what? Light pollution underwater. Really? Like, people don't get that, you know, light travels through water still. And everything that we do on land, on the coast, that's impacting everything underwater.

CHAKRABARTI: Emily Fobert is a research fellow at the University of Melbourne in Australia. Now Johan Eklöf, clownfish are just one of many marine species that require a difference between day and night to survive. And this was one of the surprising things I found in your book. That for example, the planet's most massive migration happens every single day, I should say, every single night in the oceans, and it requires darkness. And this is the vertical migration of Zooplankton in the seas.

EKLÖF: Yeah. But before we go into that, I just want to correct myself. I think I was talking about Mars and Jupiter before, and I meant Venus and Jupiter. I don't want you to get any angry emails from astronomers.

CHAKRABARTI: I'm sure we will. (LAUGHS)

EKLÖF: We cleared that out. Yeah. The impact of light pollution on marine animals. And there was something that surprised me as well when I started to research this. And as you say, every night a lot of plankton migrate from the depths up to the surface waters in protection of darkness. And when the morning comes, they migrate down again to avoid the lights. And this is all due to predation, just as in the case with the clownfish.

CHAKRABARTI: And those plankton are so important, right? Because just to point out why they matter, they are basically the foundation of much of the ocean's food webs, right? And so therefore, if there's a long-term negative impact to zooplankton in the world's oceans, that is going to reverberate across the entire marine ecosystem.

So one hidden example there, you have many other examples of animals that behave differently when they lose their access to the darkness in which they evolved, for example, can you tell us more about, I can't remember which species is it, of moths that emit a particular pheromone at night, but then when they lose the darkness, that pheromone changes and so therefore it interferes with their mating ability.

EKLÖF: Yeah. It was a study about cabbage moths, but in general, most moths behave in similar ways. To attract the opposite sex, they use pheromones like it's sense, and they can detect single molecule from miles away to find a partner. And timing is everything in nature.

And these moths, the pheromones are triggered when it's the safest time to be out. That is an hour or two after sunset. And if the sun never sets or if we hide the sunset with artificial lights, we fool the animals that it's still daylight out. The pheromones will never be triggered, or as you say, the composition of the pheromones will be actually different.

The males will never find the females and the opposite.

CHAKRABARTI: And there was a Swiss study that looked at the impact of, I guess the subsequent reduction in the moth population if they can't actually mate, due to losing the darkness and the pheromones. What did that Swiss study find?

EKLÖF: They found that they compared different meadows.

Half of these were dark in natural darkness, and the other half was lit by streetlights or an equivalent to streetlights, and they just counted how many flowers are visiting by moths every night, how many flowers are pollinated? And it turned out that on the meadows lit by streetlight, it was 60% fewer flowers that were pollinated.

So the pollination frequency, it dropped by 60% just due to the lighting.

CHAKRABARTI: So how common is this reduction in population or even just species level confusion amongst animals that have evolved in the darkness when human beings around them turn on the lights at night? This is probably very common.

We haven't studied this enough yet. Nobody ever talk talked about light pollution a few years ago, even though astronomers have been talking about it for a while. Biologists and physiologists, neurologists, whatever, haven't studied this until the last decade or so. And every animal group, or every organism group we study, we find something new about this.

CHAKRABARTI: One of those organisms is human beings.

EKLÖF: Oh yeah.

CHAKRABARTI: What are we actually doing to our own bodies when the amount of absolute darkness that we experience, it goes down?

EKLÖF: What we do is that as any other animal we have a cycle. We have a rhythm. We're active during the day and we sleep during the night.

And for the body to come to rest and relax we need our sleep hormone, the melatonin. And that is something that is triggered by darkness. And that makes us, the muscles are resting. Our body temperature drops, and a lot of things happen in your body to make sure your immune system works correctly.

And if we have the lights on for too long or if it never gets dark, this melatonin never really isn't triggered properly. So first of all, we have a hard time to sleep. But this hormone system also triggers other hormone systems. For example, making us hungry in the middle of the night, which we're not supposed to.

And there are all sorts of things happening, which we have been starting to see a link between different diseases and artificial light, actually.

CHAKRABARTI: One of them being obesity. Because it seems like there is some, a pretty strong link between not having uninterrupted sleep and obesity.

EKLÖF: Yeah. And even diabetes, which is also a connection to this.

CHAKRABARTI: And what about just, I think one of the most obvious differences between animals that dwell in the day versus those that dwell in the night is just vision. I don't necessarily think human beings were ever really evolved to be brilliant in terms of seeing things at night, but have we begun to change our capacity for night vision, especially in the cities where you can literally go 24 hours and never experience darkness?

EKLÖF: Yeah. You actually need half an hour or even more to fully use your night vision.

In your eyes, you have rods and cones. And the cones are, they see in color and the rods are very sensitive to light. And to shift to night vision, you need to use your rods. But it takes a while. And if you have lived in the city your whole life, you've probably never ever experienced that.

If you're out in the middle of the night and there is a full moon, you would probably realize that it's quite bright and you can do stuff. You can read a book or whatever just by the moonlight, but the moment you look at your cell phone or turn a light on, you will erase this night vision in an instant.

CHAKRABARTI: Do we know if that's having long-term impacts on our night vision?

EKLÖF: I think there are a few studies that actually suggest that we are slowly losing our ability. I'm not sure if this is true yet, but I wouldn't be surprised if we never use it, we will eventually lose it as well.

CHAKRABARTI: We've got about a minute before our next break, I note that not only do you have a lot of science and natural observations in your book, but there's a sort of almost like a moral outcry in the book about losing darkness. What do you think about that?

EKLÖF: It's like everything with conservation and biodiversity. What we humans do to nature. It's just another thing we like in the cities, for example we cut down forests. We have asphalt instead of grass, and we chase all the animals away. And now we're even killing the night. We can't go any further than that.

CHAKRABARTI: We're going to talk more about what we all lose when we lose the darkness, and we'll do so after the break. But I want to use some of the thoughts and experiences of our listeners to take us to that break because we received so many responses, Johan, when we said we were going to be doing this show with you.

So let's hear from a few more people who took out their phones at night and described to us what they see where they live.

Here’s Alison Ritrovato in Lyme, Connecticut; Susie Reimensyder in Steuben, Maine; and Alice Kerber in Cassopolis, Michigan.

ALISON RITROVATO: Right now there's a great horned owl calling on the other side of the lake, and the night sky is so bright I see Orion's Belt, the Seven Sisters, the big Dipper, and the air is slightly scented with a fire that someone must have nearby.

SUSIE REIMENSYDER: In the springtime, we have lots of peepers that are really loud and we can hear whipper wheels. Sometimes I hear owls and coyotes or dogs, neighboring dogs bark.

ALICE KERBER: Outside on my tiny deck after dark, what do I smell? Because of the snow, it smells like rain. Some nights I hear coyotes, and just this year that hoot of an owl's mating call. Soon I'll hear peepers. I love the sound of peepers.

Part III

CHAKRABARTI: We also heard from a gentleman named Geoff Goins. Who's been leading astronomy programs in the southwestern United States for some 30 years. So obviously, as you said earlier, the astronomers have long been attuned to the negative impacts of light pollution. He now works in New Mexico at Capulin Volcano National Monument, which was named a Dark Sky Park by the International Dark Sky Association several years ago.

It's the response that people give him when they come to see his astronomy shows at the Dark Sky Park that really astound him. And here's what he said.

GEOFF GOINS: The number of times that I have done programs and people have looked at the sky and asked me if that cloud was going to be a problem, and I have to explain that's our own Milky Way galaxy that they're seeing, when they finally wrap their head around that, that we can go outside in a dark place and look at our own galaxy.

It really makes you understand your place in this universe a lot more. You get these moments where your brain suddenly goes, it opens up, and you're like one with everything for just an instant, and then you lose it.

CHAKRABARTI: Now Johan, I will admit that I share the romanticist view about the importance of night and darkness.

But I also want to note that electrification really, which is what we're talking about, is the source of all the light pollution that's pushing back the dark, it's such a recent development in human history. It's like the blink of an eye, honestly. When you think about it, in the book, you take it even beyond, it's bad for the planet argument, and you talk about light pollution is almost a demonstration of humanity's will to power over nature.

Can you talk a little bit more about that?

EKLÖF: Yeah, life has been around for 3.5 billion years or so, and electrical light has been here for 150 years. So evolutionary wise, it's really new and man has always used light to show off things and to be able to work at night to extend his territories.

Just my great-grandfather, he installed electric light in the factory he worked, and at that time, that was the most modern thing. But today we live in a 24/7 society, and we don't even think about the light. We just expect it to be there, that we could expect to be able to borrow a library book at 3:00 a.m. or go to the gym in the middle of the night and we have gone so far away from where we were. So it's nothing you even think about anymore.

CHAKRABARTI: Really you see this as an indictment against industrialized capitalism, it sounds like.

EKLÖF: In one way. There are so many good things about this. When it comes to safety issues and we can see what we are doing.

But when we started taking this for granted and when people started complaining about this road is too dark because it's not as bright as the other one and we need to go here. And even though just two people every night you see there, there are so many, I'm not sure what to say, but then we have changed the world so rapidly and so much that we are not aware.

CHAKRABARTI: I also think though that the same lights that blast out the stars at night over cities around the world, that same technology and that development allows for lighting of city streets for additional safety, it leads to the kinds of specialized lighting that we need for life-saving surgeries, just a couple random examples there.

With that in mind, I wonder if we're being a little too absolutist in our conception of the impact of illumination. And to this point, I want to quote Adam Gopnik, who reviewed your book in the New Yorker, and he said, "Undoubtedly, the loss of night to artificial illumination is a loss for diversity, in every sense ecological and experiential.

Yet we can wonder if what human beings mainly experience as improvements must, in every instance, be subordinated to the welfare of the planet. A concept that is itself only available to humans." Essentially, you're saying it's not all that bad. What do you think?

EKLÖF: There are so many things we can do if we choose to turn off the lights when we don't need them.

For example, if you're in your garden having a barbecue, whatever, in the evening and when you go inside and watch TV instead, you could just turn off the lights in your garden and then would still have night outside. If you have a bicycle path through a park and the lights are just turned on the moment someone actually uses it.

And then we turn off the lights again using timers or motion sensors or something like that. We would still have night, and at the same time we would benefit from the lights as we intended to. So there are so many things that we can do, we just use the technology that we have.

CHAKRABARTI: We talked to someone who is in fact doing some of those things that you just talked about, Johan. This is Keith Krueger. He lives in Northern Pinal County in Arizona, and his neighborhood does not have streetlights, which is one of the reasons why he moved there about 20 years ago.

KEITH KREUGER: When the moon's out, you really see the moon without having to deal with looking at lights.

And of course, you can see the stars much better at night. You do have to pay attention where you're putting your foot because you don't want to step on a rattlesnake. Sometimes javelina go by our house in the back here you can hear them and smell them. They have a pungent smell. They come by at night.

They're pretty cute. They look like pigs. They're more, probably more primitive than pigs.

CHAKRABARTI: So that's part of what he sees because there are no streetlights in his neighborhood. But nevertheless, Keith has noticed changes in the night sky.

KREUGER: Tonight, it's actually pretty cloudy. It's high, thin clouds.

You can still see some stars shining through the clouds, but the clouds are very lit up from Phoenix and Apache Junction, and also Florence to the south. When we first moved here, it would be darker on a cloudy night then on a clear night. Because the clouds were obstructing the stars.

CHAKRABARTI: And Keith told us that these days it's actually brighter on those cloudy nights because of the reflected light.

KREUGER: I have been participating in the Globe at Night Project over the last 10 or 15 years and measuring the sky brightness here and noting the lowest magnitude star you can see, which I would say used to be able to quite easily see down to six magnitude here. It's probably looking at four and a half, five now.

So it's definitely fewer stars than we used to see, but still pretty good here compared to most places people live.

CHAKRABARTI: So that's Keith Krueger, again in Arizona. Now Johan, can you tell us a little bit more about some of the coordinated efforts going around in different places in the world where people are trying to reduce light pollution?

Because as you note in the book, of all the forms of human pollution, it seems that light pollution may be one of the easiest ones to actually solve.

EKLÖF: Yeah. Of course, we could just switch the button and turn off the lights, but that is something we not do. But there are so many other things, like I said before, using timers and motion sensors and we could direct the light, that we can shield the light off so it's not spreading as much.

And things like that. And one of the groups that perhaps it surprised me a bit that light designers really liked my book. I thought they would be the enemy, but it was rather the opposite because they don't, as they say themselves, they don't design light. They design an experience.

They design a way for us to see things and experience things, and they play around with both light and darkness. So in the light designer world, there are nowadays so many people working with these questions. And on top of that we have all the dark sky movement with all the Dark Sky Parks, which are, there are more and more every year.

A lot in the U.S. but starting to become a bigger thing even in Europe. Not in Sweden though, but perhaps that will come as well. But they are starting to, it happens a lot in different areas. A lot of municipalities also, they ask for not just a light designed city, but also a dark designed city to keep parks dark for the animals.

And that doesn't have to mean that we're less safe. We just use better lighting.

CHAKRABARTI: To that point we spoke with Zach Thompson. He is with the International Dark Sky Association, or IDA, he's one of their advocates in Lincoln, Nebraska. And since he started his darkness advocacy work, he's done some of the things that you talked about, Johan, he's swapped out his outdoor light fixtures. And now, instead of being on all the time, they are motion activated and also importantly, they're pointed downward.

ZACH THOMPSON: And it's very helpful because it's where my points of entry are, which is where the light really needs to be anyway.

So if something triggers it, which is most of the time the wind. your attention is drawn to where that light is. I hope that you with at least what I do with IDA, it's not me just trying to beat this drum and say, here's what you all need to be doing. You're doing it all wrong.

Look how I've done it. It's more just casually pass along to some family or friends and say, "Hey, what do you think? What do you think my fixtures?" Oh, that's nice. Or in fact, I actually had some neighbors ask me about it. Because they hadn't seen it before, and they were curious about it. And I thought this is what they are and here's what they do.

CHAKRABARTI: So again, that's Zach Thompson. With the International Dark Sky Association, he's in Lincoln, Nebraska.

Now, you heard a few minutes earlier from Geoff Goins who works at the Capulin Volcano National Monument in New Mexico again, that has been named a gold tier Dark Sky Park in 2016. And Geoff told us about how quickly things can change when you let the darkness back in.

GOINS: When I first moved here got this job, I lived in the park for four months. And I walked outside one night and was looking up at the night sky because it was just incredibly dark that night. Great air, just sharp, crisp stars everywhere. And I walked into a tree. I just could not see it. Normally if you got it out, get out in a really dark place, starlight actually provides enough light that you can see trails and things. But this tree was shadowing everything just enough. It was embarrassing, but it just kind of showed me how dark it really is out here.

CHAKRABARTI: That's Geoff Goins again at the Capulin Volcano National Monument in Northeast New Mexico.

Johan, you make a really interesting observation towards the end of your book, "The Darkness Manifesto," you write about how in a sense when we oftentimes think about silence, we think about it only as defined by the absence of sound, and that perhaps we reflexively do something similar when we are thinking about darkness, that we define it just very simply as the absence of light, but it sounds like you're calling for a completely different conception, a completely different definition of darkness. Not as defined by the absence of something, but rather an experience, an environment that is a complete hole within itself.

EKLÖF: Yeah. Yes. It would be interesting to look at it from the other way. I don't have the definition, because it's there already. It's the absence of light. But when you think about it, you can almost, if you're out in such a dark place, as was described here earlier, you can almost feel the darkness.

It surrounds you and it's like having a blanket to where you head or something. So the darkness is out there. Also, there are so many negative words connected to darkness. So it's hard to say something positive about it. We have all, the light is always the good side, and darkness is always the bad side.

That's why I started to think about how can we redefine darkness in a way. I don't think I had the definition, but it was interesting to just speculate around it.

CHAKRABARTI: We have just a few seconds left, Johan. And you encourage us to think of darkness perhaps in this way, that when we lose it, then we're losing the magic also that comes with the coming of the light.

You say life's renewal every morning and every spring loses a little bit of its magic. Just a few seconds for a last thought there, Johan.

EKLÖF: I think that everybody I've talked to really likes darkness even though it's a bit scary, but that's also what makes it interesting and gives us a feeling of awe under the needs of stars. So just go out there and experience the darkness.

Journal of Ecology: "Ecological effects of artificial light at night on wild plants" — "Plants use light as a source of both energy and information. Plant physiological responses to light, and interactions between plants and animals (such as herbivory and pollination), have evolved under a more or less stable regime of 24-h cycles of light and darkness, and, outside of the tropics, seasonal variation in day length."