In Defense of Sunlight with Rowan Jacobsen

What if sunlight isn't the enemy we've been told it is? In this episode of Sunlight Matters, science writer Rowan Jacobsen discusses his new book, In Defence of Sunlight, and explores the growing body of research linking natural light exposure to improved health, longevity, sleep, and well-being. From heliotherapy and vitamin D to infrared light, circadian rhythms, green light therapy, and modern light deficiency, this conversation challenges conventional assumptions and reveals why sunlight analysis and understanding our daily lightscape may become increasingly important for human health in the future. Discover how natural solar exposure, outdoor environments, and the rhythms of daylight continue to shape our biology in ways we're only beginning to understand.

Key Topics Discussed

Why Rowan Wrote In Defence of Sunlight

• How a research fellowship at MIT introduced Rowan to emerging studies linking sunlight exposure with improved longevity, cardiovascular health, and cognition.
• Discovering that sunlight exposure was often associated with better health outcomes despite decades of messaging encouraging people to avoid the sun.
• The gap between public health messaging and the broader body of scientific evidence surrounding sunlight and health.

The Forgotten History of Sunlight as Medicine

• The role sunlight played in treating rickets and tuberculosis during the late 19th and early 20th centuries.
• The rise of heliotherapy and mountain sanatoriums where patients were prescribed sunlight and fresh air.
• How sunlight was once considered a mainstream medical treatment.
• The shift from sunlight as medicine to sunlight as a health risk emerged with concerns about skin cancer.

How "Sunlight is Dangerous" Became the Dominant Narrative

• The rise of ultraviolet lamps and excessive sun exposure in the 1930s–1950s.
• The public health response to increasing skin cancer rates.
• Why public health campaigns became increasingly forceful in promoting sun avoidance.
• Whether the pendulum has swung too far away from balanced sunlight exposure.

The Modern Light Deficiency Problem

• Why today's children spend dramatically less time outdoors than previous generations.
• The health implications of spending most of life indoors.
• COVID-19's impact on outdoor habits and sunlight exposure.
• The concept of "light deficiency" as a modern environmental challenge.

Infrared Light: The Hidden Half of Sunlight

• Infrared light accounts for approximately half of the solar spectrum.
• Research suggesting infrared wavelengths may influence mitochondrial function and cellular efficiency.
• Why trees appear to "glow" in infrared imagery.
• How modern indoor lighting provides almost no infrared exposure compared with natural environments.

Light, Science and Research Bias

• Why sunlight benefits have often been discovered accidentally rather than through direct research.
• The role funding structures play in shaping scientific inquiry.
• Examples where studies focused on disease risk unexpectedly revealed benefits associated with sunlight exposure.
• The growing community of researchers connecting findings across multiple disciplines.

UV Light: Risks and Benefits

• Vitamin D production and nitric oxide release.
• Richard Weller's research into sunlight and cardiovascular health.
• Sunlight's role in inflammation regulation.
• The challenge of identifying optimal exposure levels for different individuals.
• Future research into obtaining the benefits of UV without excessive skin cancer risk.

The Rise of Light Medicine

• Red light therapy and its expanding use in healthcare.
• Emerging applications of green light for migraines and anxiety.
• New UV technologies designed to stimulate vitamin D production while minimizing risk.
• The possibility of personalized light-based treatments in the future.

Understanding "Lightscapes"

• Rowan's concept of "lightscapes" — the unique combination of light conditions that surround us at any moment.
• How different light environments may influence physiology, mood, and wellbeing.
• The importance of considering both place and time when thinking about light exposure.
• Potential future applications for tools such as Shadowmap.

Living Without Artificial Light

• Rowan's month-long experiment in the Arizona desert.
• Eliminating artificial light after sunset.
• The profound effect of darkness, natural dawns, and gradual sunsets on sleep quality.
• Why the contrast between bright days and dark nights may be more important than total light exposure.

Circadian Rhythms and Modern Lighting

• The role of blue light in regulating melatonin production.
• How LED lighting differs from traditional incandescent bulbs.
• The effects of light pollution and evening screen exposure.
• Why modern lighting environments may disrupt sleep and circadian health.

Green Light and Human Evolution

• Emerging evidence linking green light to migraine relief.
• Why forests and tree canopies create distinctive light environments.
• The relationship between green light, infrared light, and plant biology.
• How natural environments may provide complex light exposures humans evolved alongside.

Key Takeaways

• Sunlight is far more than a source of vitamin D.
• Human beings evolved under vastly different light conditions than those experienced today.
• Modern life has dramatically reduced our exposure to natural light.
• The relationship between sunlight and health is more nuanced than "sun good" or "sun bad."
• Infrared, ultraviolet, and visible light may each play important biological roles.
• Sleep quality may depend as much on bright daytime light as on darkness at night.
• Future medicine may increasingly use specific wavelengths of light as therapeutic tools.
• Small increases in natural light exposure may provide meaningful health benefits for many people.

Rowan Jacobsen is an award-winning science writer and author whose work explores the relationships between humans, nature, food, energy, and the environment. His latest book, In Defence of Sunlight, examines the science, history, and health implications of humanity's relationship with sunlight.

More info on the book is available here: https://www.rowanjacobsen.com/books/in-defense-of-sunlight

Sunlight Matters is a podcast exploring the role of the Sun in human health, architecture, cities, and everyday life.

Through conversations with scientists, architects, and technologists, the series examines how natural light shapes our bodies, our buildings, and the way we live indoors.

Hosted by Dave Wallace, Sunlight Matters asks a simple but overlooked question: what happens when we disconnect from the Sun?

Because sunlight isn’t optional. It matters.

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Transcript

Rowan (00:00)
it just happened to be when some new studies were published  indicating that light had some interesting

like health benefits that we hadn't thought about before, that it was associated with reduced mortality and improved cognition and reduced cardiovascular disease in particular. so that was curious to me, because like many people, I'd sort of unthinkingly absorbed this conventional wisdom which we've had  in the world over the past few decades that

sunlight is bad for you and you should minimize it whenever possible. so I remember actually like looking up, if this is true, like how bad is sunlight for you? Like how much does it lower your lifespan? And so sure enough, as you know, I've what I found out is that it's quite the opposite.

The the issue is we're now in this weird place in civilization where most of us

almost literally get zero during the course of an average day. And that's where the real health problems happen. So it's not it's not going from a little to a lot, it's going from zero to a little that will help for most

So a the the big takeaway is just make sure you don't get none. it's not that you have to get a ton of light to get these health benefits.

Dave (01:24)
welcome, Ron, to Sunlight Matters. I'm really delighted to have you. You've got a new book coming out. I think in the UK we've got to wait a little while, but I'm chomping at the bit and I've got it on pre-order. But before we talk about your book, I wondered if you could just briefly introduce yourself.

And give us a bit of background in terms of what you do and what you're interested in.

Rowan (01:48)
Sure, yeah. So ⁓ my name's Rowan Jacobson and I have been a full time writer for most of my adult life for the past, you know, twenty plus years. I've been writing books and magazine features for ⁓ magazines across sort of like ⁓ the the subject ⁓ spectrum, ⁓ on all kinds of different topics, all sort of relating to, you know, what it is to be a human being in this

world of relationships with with light and energy and other creatures, all the things that all the inputs that ⁓ go into us to make us what we are and to keep us going. So some of that's been food writing, a lot of it has been science writing. I've also, you know, I focus on conservation and nature as well. So

Dave (02:34)
Yeah, I saw

you'd written an article about swimming with whales I went swimming with whales in East Timor last year. yeah, they're blue whales. they're big ones. Yeah, it's quite something. But yeah, I could see that there's a theme going through.

Rowan (02:41)
did you? What kind of whales?

⁓ wow. Wow. The big ones.

Dave (02:59)
the writing that you've done, but you have this book which is coming out ⁓ and ⁓ it's called In Defence of Sunlight. ⁓ And I just wondered if you could sort of briefly talk about what the book is trying to do and some of the themes that you're kind of drawing out from.

Rowan (03:20)
Yeah, so I first got interested in this subject about eight or nine years ago. ⁓ I was doing a a fellowship at MIT, which is for science journalists, where you don't publish for you're not allowed to publish for a year, you're just meant to research ⁓ with the idea that you're gonna be able to write about science at a deeper level on the other side of that year. And it just happened to be when some new studies ⁓ were published  indicating that light had some interesting

like health benefits that we hadn't thought about before, that it was associated with reduced mortality and improved cognition ⁓ and reduced cardiovascular disease in particular. ⁓ so that was curious to me, ⁓ because like many people, I'd sort of ⁓ unthinkingly ⁓ absorbed this conventional wisdom which we've had ⁓  in the world over the past few decades that

sunlight is bad for you and you should minimize it whenever possible. ⁓ so I remember actually like looking up, like, well how bad if this is true, like how bad is sunlight for you? Like how much does it lower your lifespan? And so sure enough, as you know, I've what I found out is that it's quite the opposite. It actually sun exposures correlated with improved lifespan and lower rates of all the standard ⁓ chronic diseases that are associated with aging. So it seemed it seemed that that was surprising to me, because I thought

you know, if if light is good for us, why aren't we hearing about that and and what do we actually know about it? And it turned out there was a whole lot more research there than I had realized. So then I spent a couple of years really going into the research and meeting the researchers and then I started attending their conferences eventually and and realized there was this huge body of evidence and we needed a new message out there ⁓ about light

that sort of was ran counter to the current message that we'd received, but also had a much longer, like h historical track record. Like it made me realize that we were we're in a bit of an aberration with this idea that light is bad for us. That most people at most times would have thought that was a very strange idea.

Dave (05:35)
Can I ask, that whole notion of light is bad for us. Do you talk in the book about how that narrative got kind of embedded into our thinking? ⁓ I'm just kind of interested in what happened.

Rowan (05:54)
Yeah, and that was one of my questions too. Like how how on earth did we ever get here? So I actually do spend ⁓ a lot of time in the book sort of going over the history of it all. And it it's a fascinating history. But it it really all starts with Ricketts and tuberculosis in the late eighteen hundreds. So these were two of the diseases that were like the scourges of Europe.

i in that era, that Victorian era, I think tuberculosis was responsible for one out of four deaths in in Europe by the late 1800s. ⁓ and almost coincidentally it it turned out that both those diseases, Ricketts and tuberculosis, could be treated with sunlight. ⁓ Ricketts we know ⁓ now is ⁓

it's a disease of vitamin D deficiency. If you don't have enough D, you can't get the calcium into your bones to make s har hard bones. So ⁓ kids who were n not exposed to any light ha were deficient in vitamin D and they would have soft bones and all kinds of problems because of that. ⁓ and just literally a little bit of light solved the problem. tuberculosis is a bacterium that can

infect your lungs, which is sort of the classic consumption of the Victorian era, but it can also infect your skin and basically be like this flesh eating bacterium. Also really terrible. There's, you know, you can find some horrifying pictures from the late 1800s and early 1900s of what it was doing to people. But then a ⁓ a Danish doctor discovered that just concentrated sunlight

would kill the bacterium and cure the cutaneous version of tuberculosis. He won the Nobel Prize for that discovery in nineteen three. He had an institute in Copenhagen. And kind of coming out of those two things, it suddenly looked like light might might be really good for you. And people started wondering what else it might cure. And so there was this whole era of heliotherapy, ⁓ kind of, you know, like the Magic Mountain era, when people would head up to sanitariums in the Alps

to take in the air, but also to take in the light. ⁓ and we've almost forgotten that the light was a big part of it. So they would, ⁓ you know, they would wheel their patients out onto sun decks to give them a little more light each day. And and the idea was that it was gonna cure your tuberculosis, but also that it was sort of gonna like be good for your constitution in general and just h make you more resilient. And it seemed to work. Like

people often not always, but often got healthier with those kind of treatments. So then by the twenties and thirties, the medical establishment was v like totally on board with light being essential to health. And, you know, surgeons in World War One noticed that wounds healed faster if patients were exposed to light.

Hemingway's character in Farewell to Arms actually is treat you know, the the Italian surgeons like stick him out in the light so that he'll heal better. ⁓ so so there's a sense, and it was very mainstream, that light was essential to health. And then I think what happened is you know, as humans do, we we went too far. We took it and ran with it. Like it's the classic human thing where

Well, if a little of this thing is good for me, maybe a lot is even better. So s by the thirties, b frying yourself in the sun became the the way to be healthy. So people were literally seeking sunburns for their health. And then of course we also invent products. So

these ultraviolet lamps became all the rage in the thirties and forties and even into the fifties, so that people could essentially irradiate themselves right at home without having to seek the actual sun. So i and and you know, there's you you can find these ads for, you know, for these lamps that you put over your baby's crib so you can like just like

zap your baby with yeah, blast with UV. So anyway, so then at that this was the same time that s that doctors were starting to discover that UV was connected with skin cancer. So they kinda went, like th everybody's gone overboard. They're gonna they're giving themselves skin cancer with this excessive UV exposure. So then the campaign beg began to convince people to stop and it didn't go very well because people like sunlight. ⁓ they like being tan. ⁓

Dave (10:02)
lost.

Rowan (10:32)
So it was this kind of classic dynamic where the more it didn't work and the more rates of skin cancer rose, the more strident the messaging became in a way to kind of scare people out of their sun habits. And then through the eighties and nineties, as skin cancer rates got really high, the establishment just decided but that basically it had to have some very, very ⁓ scary, strident messaging to get people out of the sun.

⁓ which which finally worked, right? It like it took a long time, but they did manage to drive that message home and to their credit, their goal was to reduce rates of skin cancer, ⁓ which hasn't quite worked yet, but for reasons we can talk about. But they did manage to get people to stay out of the sun and actually the average human's amount of sun exposure has been dropping for decades. ⁓ but so then when

maybe it was time for the pendulum to swing back and and to it was ti it's time for a more ⁓ commonsensical approach to sun exposure. That's been a hard sell because they finally got everyone thinking, sun bad, I should get out of it. So the you know, institutions are very hesitant to sort of undo some of that messaging, but they probably need to from a ⁓ an overall health perspective.

Dave (11:54)
I mean, that's fascinating. Thank you so much. mean, again, it makes me want to read the book even more because that history, ⁓ you know, it's great to have it demystified because I didn't realize that, you know, was until quite late in the 30s and 40s and 50s that, you know, people were still kind of embracing the sun as a curative. And, you know, it's interesting what you say that the message

it has kind of got through and it is really like the establishment, I guess the medical establishment is very ⁓ pro, you know, the message of sort of stay out the sun and, you know, it's taken people like, I think the forward of the book is by Richard Weller. ⁓ And, you know, I've looked at Richard's, some of Richard's studies and

Rowan (12:43)
Right.

Dave (12:47)
You know, actually, when you start digging into the data, like so much of what we're kind of faced with, the data tells a slightly different story, doesn't it, in terms of what's going on.

Rowan (12:57)
It does. And I now that a few dermatologists are starting to break ranks, I think you'll I think you'll see things shift in the next few years toward a more more balanced message. But it took a while. I I kind of it it almost ⁓ it it almost parallels the conversation around like psychedelics.

and and other drugs where, you know, you had that era with Timothy Leary and and others in the sixties and and even, you know, going way back, when people were quite interested in the use of psychedelics. And then because it kind of went out of out of hand, the the you know, the authorities ma made them all illegal. And if you s you sort of suggested that there was a place for psychedelics, you were ⁓

way, way out of the acceptable, you know, mainstream and to the point and then, you know, the all the messaging around, you know, if if you smoke one joint, you're gonna destroy your brain. Like and so then but then people started to break ranks, a a new generation sort of came in and said, Well, you know, maybe there's maybe there's there's, you know, a little truth on both sides. So I kind of feel like that's what's happening now with ⁓ with light.

Dave (14:11)
So in terms of the book itself, so you kind of cover the history, what are some of the other things that you're kind of looking to do with the book itself? Because I think, you one of the things that I've noticed in terms of the discussions ⁓ that I've been having with various people is, you know, you've got, obviously there's sunlight, there's, you know, indoor light, there's the built environment.

There's all these kind of factors which are out there, which, you know, it seems a conspiring against the sun. I mean, I think it's the instance COVID, you know, people have gone inside even more like that huge jump of, you know, I've spent my life trying to get my kids to go outside and, you know, I mean, one of them went into his room in COVID and it's sort of almost I have to literally drag him out now because of the way he sort of set. So I was just wondering if there's sort of other themes like

Rowan (14:45)
Yeah.

Yeah, yeah.

Yeah, yeah.

Dave (15:08)
you know, cultural themes that you're picking up in the book.

Rowan (15:12)
For sure. I think that's a big part of it. And yeah, it's the BBC just had a story recently about a new study that showed that yeah, the the average person is getting the average kid is getting less than three hours a week outdoors, which is a drastic, drastic change from you know, when we grew up or when and certainly when our grandparents or great grandparents grew up. ⁓ human beings used to get

a whole lot more light exposure than they do now. And I there's lots of signs that this basic l what's a light deficiency ⁓ is quite bad for us. So I think that yeah, the the the ⁓ the sort of like big picture is that w we clearly need to be outside more for our health. And it almost doesn't matter, you know, you can use sunscreen, you can be in the shade. It just it's essential to be outside. So

If the current messaging, the current scientific ⁓ messaging is sort of pushing us to be inside more or to at least avoid to have, you know, obstacles to just getting outside, then that's probably ⁓ not productive. So the yeah, d basically the book the book looks at the reasons we probably need to be outside more, built around light, but other things too, and goes into the science, ⁓

to like sort of examine w where where that's safe and you know w where we do need to w to worry about overexposure.

Dave (16:48)
Yeah, I mean, I think that's always going to be the balance, isn't it? But, you know, one of the things I sort of found very ⁓ revealing was just some pictures I think Bob Fosbury had taken of the IR of plants, infrared sort of profile of plants. And then I think ⁓ Dr. Roger Schvell did some sort of simple pictures as well where he sort of pointed at an infrared camera at a tree. You know, and I mean, I...

Rowan (17:11)
Yeah.

Dave (17:16)
had to go and get a filter. So I did the same and I was like, wow, trees are kind of glowing with infrared, you know, and it sort of, it kind of made a lot of sense to me that you kind of sitting under a cool tree in summer is why it's such an excellent thing to do.

Rowan (17:18)
Yeah.

Yes.

And that turns out to be one of the perfect human environments is under a cool tree in summer. So and it it all has to do with that infrared. So about fifty percent of the solar spectrum is infrared light, which we can't see with our eyes, and it is but it is pouring down on us and actually pouring into us. That particular those wavelengths aren't

absorbed by molecules in our skin or reflected, so they tend to enter the body and scatter. And Bob Fosbury has been one of the main people who's talked about this research. But anytime we're outside, all these infrared photons are, you know, diffusing through us like like light through a red wine glass or something. And eventually are being absorbed by molecules in it looks like in our mitochondria that just make us run a little more

efficiently with a little less wear and tear. So it's like oiling your car engine. ⁓ things just work a little better and and break down a little less. So but the the the catch is our artificial lighting now indoors produces zero infrared light. So, you know, if like that BBC study were indoors other than three hours a week, we are getting almost none of this

wavelength that we used to just be sucking in for twelve hours a day in, you know, our our ancient evolutionary past. So that's a profound change in the the the average inputs about for the average human going about their day and w you know, what's that doing to us? Almost certainly not nothing, right? Like so th so I think that that is gonna be a really interesting focus of research in the coming years.

David James Vaughan Wallace (19:22)


Dave (19:45)
So in terms of the book itself, are you just trying to kind of with science raise the notion that we've become disconnected from sunlight, reconnecting may not be a bad thing at all for us. Or is it more like, you trying to kind of get, I don't know, policymakers to start rethinking what's going on? I mean, I guess what's the audience, and in your head, what would be...

Rowan (20:13)
Right,

right. I ⁓ it's going it's direct for individuals for I sort of like try to hurdle right over the policymakers and go straight to the people. But I do hope policymakers will eventually fill in on some of these these topics. It it it wouldn't hurt. But yeah, it's for the it's for the you know, the person who's light curious who who

Dave (20:14)
I assume like in terms of the book.

Rowan (20:40)
Who has who who might be surprised, who's never been comfortable with this idea that that outdoor light is bad for them, and might be surprised to find that the science is quite different than what they've led to believe. So I I spend quite a bit of time going into the the science, establishing these health benefits that sunlight has. And also how how that came to be, because I think it's interesting. Science science doesn't work always the way we think it does. So

it it often reinforces its own biases. So in this case, no one was ever going to get funding. Almost all scientific studies require grants, right? You have to go out and get your grant to fund your study. and you apply to usually it's just a handful of of you know the big powers that be that hold the purse strings that disperse the grant money. So your first step, if you want to do a study, is your proposal to them

explaining what what you want to do and why you want to do it. And if they don't like it, they're not gonna fund it and you don't get to do it. So probably a lot of things in science never even get studied because they're gonna run counter to what these you know these people who are often late in their careers think is the truth.

So and and especially w if like if you want to stick somebody out in the sun, you're never gonna get funding for that because it's considered a health risk, right? Because of skin cancer. So there hasn't been so there's no way to for to do research directly on the benefits of light. So all the all the evidence that's come to light was generally accidental. Like people would be studying melanoma and sun exposure and to show that more sun equaled higher risk of melanoma.

And they'd sort of accidentally noticed that that same data set had lower rates of diseases for everything except melanoma. So i and or ⁓ people studying ⁓ MS or another autoimmune disease.

would accidentally notice that MS rates were way lower in kids who spent more time outside. So it it all sort of slowly accumulated, like in all these diverse fields, accidentally, all this evidence that light was good. And only r more recently have, you know, have all these scientists met each other and sort of compared notes and realized that there was something important going on.

Dave (23:04)
And I mean, I think it is interesting because there is a kind of a few of these scientists who are becoming more of a kind of centre of gravity, I think, for a lot of this. I mean, a question for you, which is, is there anything, any research that you would like to see happen ⁓ just on the back of what you've sort of discovered in the book? Where should they be going next, do you think, with some of the science?

Rowan (23:31)
Yeah,

that's such a good question. Well, the infrared I think is gonna be quite interesting to look at. ⁓ for ultraviolet ultraviolet is sort of like the more edgy one to talk about because the ultraviolet end of the spectrum is the highest energy part of the solar spectrum. It is the one that can raise your risk of skin cancer, but it's also the one because of that high energy.

it has a lot of beneficial effects on the body as well. Like it makes vitamin D, most obviously. It makes ⁓ it produces nitric oxide in the skin, which Richard Weller w did some of the main experiments on. It ⁓ it reduces inflammation throughout the body in there through this whole like complicated metabolic pathway. But it's basically it triggers all these signaling molecules in the skin that then s signal to the rest of the body, ⁓

to to sort of ⁓ move to a a ⁓ lower inf inflammation state to sort of quell that type of behavior. ⁓ so so it's it has pluses and negatives at the same time. And so I think one of the interesting ⁓ areas of research is going to be with UV, how how are there ways to get the good without the bad or most of the good without much of the bad? And and and for who?

Dave (24:55)
Exactly.

Yeah, I mean, because I think there's a sort of dosage element to all of this is like, and I know that would vary from people to people as well.

Rowan (24:56)
You know, be because we're all different.

Dave (25:08)
you know, if I stand out in the sun for in the midday sun for 10 minutes, is that good? I, you know, 15 minutes, you know, so I think it's interesting that you kind of say that because I think now the science is starting to establish that, you know, light is doing these incredible things. You know, I would agree with you. think the next step is to kind of go into more.

Rowan (25:16)
Exactly. Yeah. Yeah.

Right.

Dave (25:35)
about what that, I guess the line between good and bad basically isn't it.

Rowan (25:40)
Right. And I think you're gonna see light medicine become more of a of of a thing, ⁓ where, you know, there's natural sunlight, but then it it might start to get a little more customized where for this particular problem, maybe these wavelengths can help treat that, either through the eyes or through the skin. So I think I think you're gonna see a lot of exploration for ⁓ sort of like the more the medical uses of light, which you're we're starting to see already. Like re red light therapy has become a big thing in dermatologists' offices and even dentists' offices.

Or just beauty clinics. ⁓ and I think, you know, sometimes there's evidence for that, sometimes it's a little weak. But but there are green light is now being used to relieve anxiety in migraines, which is really interesting. ⁓ and I think the evolutionary reasons for that might be super interesting. ⁓ there's some there's a new ⁓ a new generation of UV producing lamps that are meant to be used for very, very short time frames. ⁓

And they're they're very particular wavelengths that don't really overlap with the skin cancer causing spectrum, so that you can actually maybe get some the vitamin D benefits without the skin cancer risk, which could be huge for people who live in places like you and I do where in winter we can't make any vitamin D. so I think yeah, I think it's gonna get I think it's gonna become a big a big field pretty soon.

Dave (27:00)
Yeah.

No, I agree with you. mean, and certainly what we're seeing is more and more people seem to be interested in it. just quickly returning to that sort of wavelengths of light and, you know, it's one of the things with Shadowmap, which we've sort of thought about is if you could kind of...

show people where to look or where to be at certain times of the day with different wavelengths of light. We could kind of match that with sort of some form of treatment for something or other. That could be something really, really useful to people. But I mean, guess there's a long way to go in terms of sort of getting that analysis through.

Rowan (27:37)
I agree, yeah.

But you do you you like I've noticed my own thinking has changed. I I start to think in terms of what I call lightscapes. You know, like we think of landscapes or soundscapes, but y you are every moment in a different lightscape and that lightscape will affect your physiology as well as your state of mind. ⁓ so it's worth ⁓ thinking more about

your lightscape than that we have traditionally and maybe seeking out particular lightscapes. Like particular lightscapes are just gonna be naturally good for humans or naturally good for you. You everyone's gonna have different ⁓ preferences. But it's not it's not just imaginary or illusory. Like there's something physical to those lightscapes. And I think, yeah, so ⁓ tools like Shadow Map are probably gonna play a role in that too. Like b you know, 'cause the lightscape is changing throughout the day. ⁓

So it's not just where you are, but when when you are in your in your day night cycle.

Dave (28:40)
No, think it's really, really, really interesting. I mean, one of the things I did read that you'd written was this article about trying to cure your insomnia by basically living in a desert for a little while. I mean, it's a really, really lovely article. So thank you. ⁓ But one of the things that was fascinating about that was sort of getting up at

Rowan (28:56)
Yeah.

Dave (29:07)
at dawn or just before dawn and seeing the kind of just that whole watching the arc of the sun across the day and you know so I mean I don't want to go into I just wondered if you could kind of just briefly outline what the article's about and then just sort of yeah if we could kind of zone in on sort of sunrise in the desert and what that kind of meant to you.

Rowan (29:32)
Yeah, sure. so yes. So I've I was starting in middle age I I began to get that classic form of insomnia where you wake up for a couple of hours, two, three hours in the middle of the night. It's very annoying. and w sin you know, once I was working on

light as my main subject to write about. I was in addition to, you know, the effect on the skin, I was ⁓ you know, obviously re reading a lot about the effect on circadian rhythms of light through the eyes mostly. And this is something that's gotten a lot of attention ⁓ in the mainstream press. We we know that light at night prevents your whole system from really

going into a full r sleep and relaxation mode and even small amounts of light at night are associated with worse sleep and ⁓ worse health outcomes in general. So I did I started and most of us do live in places where we've got light pollution at night. ⁓ and I d started an and and or we do it to ourselves, right? Like we know we keep the lights on till till late at night or or even medium late at night.

And and those lights are different than they used to be. It used to be the old incandescent bulbs had very little light in the blue end of the spectrum, and much more in the red and infrared. And what one of the things we've discovered is that ⁓ the body's own internal clock for regulating circadian rhythms is particularly tuned to the to blue light, the the blue part of the spectrum.

Dave (30:53)
All right.

Rowan (31:10)
Which didn't used to be a big component of our indoor lighting, but now with LEDs, it they're almost entirely blue light. That is their big peak. So modern lighting has a much bigger impact on the body's ability to produce melatonin and regulate sleep than old lighting used to be. So that's that's part of the problem. So then I started to wonder, well, how much how much of my insomnia is related to artificial light? So I decided

to go cold turkey ⁓ and and find a place where I could live without artificial light for a month and see if it would make a difference. And so I picked the Ar the Arizona Desert, pretty close to Kit Kit Peak Observatory, 'cause they're you know, that's a really dark place. That's why they're there. So I thought that would be a good place. Found an old airstream trailer to rent, middle of nowhere, th thousands of acres of just empty desert. ⁓

So it was great. I love I love empty deserts. So that that it was nice to be there, but it was also just crazy dark at night. So a and and my rules were I could do whatever I want during the day when there's more more light around than you know what to do with. But once sunset came, no artificial lighting of any kind. and so there was some practical issues with it. Turns out

When it gets dark fast, suddenly y if you haven't planned ahead, you can't find anything. But but yeah, like the one of the big takeaways for me was ha that slow, gradual settling of night that happens. And then in the reverse in the morning when the light slowly rises, like a curtain being ever so slowly pulled up.

It's so different than what we tend to all do in our daily existence, which is, you know, we k the the light disappears at sunset, we keep it going with artificial light, so nothing has really changed, and then suddenly, you know, lights out at ten o'clock or eleven o'clock or or whatever. And that's that's something human beings never experienced until a hundred years ago, basically. So that

Dave (33:08)
interesting.

Rowan (33:18)
I I've found that it was incredibly therapeutic to have that, you know, what what basically is a two hour stretch where the light is slowly changing, the colors are are changing, going through that beautiful, you know, rainbow effect through the sunset colors, and then you're left with this deep blue of the sky that actually lasts for quite a while and the stars slowly come out. That's ⁓ I I f I think that is probably a really

Dave (33:33)
you

Rowan (33:46)
healthy signal to the body th compared to lights out at eleven or, you know, lights on in the morning, any of those harsh transitions are probably somewhat confusing to our cells on a sort of like our at a deep neuronal level.

Dave (34:03)
And I think in your article, you know, when you actually start kind of following that rhythm of sunrise, getting up before sunrise and then, you know, having your day and then basically going to sleep just after sunset, you found that your insomnia was a lot better, didn't you?

Rowan (34:22)
Yeah, it was not it like the the the easy version didn't work as well as I thought it would. I f I was I still had work to do, you know. I had my my freelance life to try to keep alive. So I was working normally on my laptop during the day in my little airstream. ⁓ so I wasn't actually getting a whole lot of light exposure during the day. ⁓ so I was getting the dark nights, but I was still experiencing the insomnia and then the second half of that month I'd kind of like

Delivered my assignments and I could really just go hiking during the day and climb mountains and be out in the desert. And that is an incredibly bright environment during the day. And what I found was that that change in amplitude where you had very bright days and very dark nights, my my insomnia did go away. And I slept the best I'd slept in years. and there's there's ⁓ a fair amount of research that supports that idea that it's not purely the amount of light, but it's that.

Amplitude. Like you you want to you wanna have when your when your brain registers daylight as like very, very bright, intense, lots of lux during the day, then that drop at night is probably more important than the absolute level. So as long as night feels like a big shift from day, then then your brain and your internal clock is probably gonna be able to work with that.

Dave (35:45)
Amazing, I was fascinated because one of the things I'm trying to do is sort following the sunrise ⁓ as the year goes on and it's sort of been interesting how, you know, we're almost at the middle of the year and I think I'm going to make it but it's actually... I mean now it's sort of like 4.30pm I've got to be up to... but you know we've got a beautiful field, I take the dogs up.

Rowan (35:53)
Right.

You w what time are you waking up? You must be waking up at three thirty or four.

Yeah, yeah.

Nice. Yeah, I did the same. I was up at four thirty this morning 'cause because the light was was there, you know.

Dave (36:15)
I've got lots.

Well,

and that's that, you know, we've had a few cloudy days and I've like, OK, I'm just going to lie in. But, you know, tomorrow is going to be a blue sky morning. So I'll be up at four thirty. And but there's something which does happen around that, as you say, it's very kind of calming and meditative. And the quality of light in those first few minutes when the sun just sort of comes up is just exceptional. And you're right. I think now I think about it.

Rowan (36:24)
Yeah.

Yeah.

Dave (36:47)
Like when I then spend more time just sort of outside in the brightest sun I Think probably if I kind of analyzed it that's when I'm sleeping better at nights myself so It's it's really interesting all of this So I mean is there anything in your book that you you want people to take away in particular?

Rowan (36:53)
Mm-hmm.

I think I think one of the important things is that yeah, just like we were talking about, it's it's not like you need to lie out on the beach, right? D to to reap a lot of these rewards. You you just need to be out. You can be in the shade, you can be ⁓ in the that early morning light. Like that is all anything that ⁓ that helps your body sort of register this these natural shifts in light that happen over the course of every day on Earth.

is gonna sort of put you back on track to what, you know closer to what the the human physiology evolved under. Like a regime that's closer to that is gonna anything that gets you more in that direction is going to help. So a the the big takeaway is just make sure you don't get none. Like most mo it's not that you have to get a ton of light to get these health benefits. The the issue is we're now in this weird place in civilization where most of us

th almost literally get zero ⁓ during the course of an average day. And that's where the real health problems happen. So it's not it's not going from a little to a lot, it's going from zero to a little that will help for most people.

Dave (38:24)
I think it's a really clear and good message. I just wanted to touch on green light actually because you talked about when you were in the desert you then suddenly were like ⁓ gosh I'm hankering for the green light of New England in terms of the sort of light coming through the trees and it's something which I'm fascinated by.

Rowan (38:34)
Yeah.

Dave (38:48)
I think the Guy Foundation did a talk and they had a gentleman from Arizona University has done some work on green light. And so we put my wife, she really suffers from migraine. So we put a therapeutic green light in our kitchen and just had it on over winter. She didn't get migraine. So, you know, it's really that.

Rowan (38:53)
Mm-hmm.

⁓

And did it work? Did it help? interesting.

Dave (39:14)
I mean, you're right from an evolutionary point of view, it kind of makes perfect sense because, you know, at some point our species spend a lot more time up in the trees and under under trees. But it's for me is sort of so indicative of that intricate relationship between between light and us. And I think, you know, I talk about the green light is interesting because you can see it.

Rowan (39:39)
Right.

Dave (39:39)
One

of the problems with infrared light and UV light is you can't see it. you know, we've got used to being kind of very visual about light and its impacts. so green light is fascinating because if it sort of therapeutically works, it's a kind of good evidence for the other things that might be going on from a light point of view as well.

Rowan (39:45)
Right.

I think that's exactly right. And it's actually a perfect stand-in for infrared because ⁓ th those are the two wavelengths that plants tend to reflect, like green leaves reflect. ⁓ they don't want green or infrared for photosynthesis. They want blue and red, basically. ⁓ and they absorb UV as well. So anytime you're you're seeing green around you

you you're getting a a you know, a big shot of green photons, but you're also getting infrared. ⁓ anytime anytime it's natural green, anytime it's a green from a plant, you're you're getting ⁓ a high rate of infrared as well. And so we've talked about the benefits of infrared. The green green photons are really interesting. There's two groups studying this in the US, one at University of Arizona ⁓ and one at Harvard. And ⁓ it started with a discovery accidentally again.

years ago that of all the different wavelengths, green made migraines better. Most of the other wavelengths made them worse. Because often like no light is is what people with migraines look for, cause the light can can, you know, set off the migraine. Not green. And it turns out ⁓ you know, we have three different types of cones in our eyes to detect color. ⁓ one that goes that is focused on red, one on green and one on blue.

And s interestingly, the green one sends a smaller electrical signal to the brain. So there's literally less electricity going to the brain from green photons than from red or blue. And so the theory is that this is part of the reason it's less you know, energizing to the brain. It's it it sets off the brain a little less, the green light. It's more calming. ⁓ and what they found in the experiments is that, yeah, like green light reduces

Migraines but also reduces pain, sensations of pain and generally reduces anxiety.

And I it was it's interesting. I got to sort of play around with this. One of the other things I did while I was in Arizona was I I checked myself into the sleep lab at the University of Arizona just for curiosity. worked with a researcher there named Kat Kennedy. And she ⁓ put me through this twenty four hour light regime that kept changing. They have these very fancy lights that can do any color you want second by second. So they had programmed this whole like sort of a a light roller coaster for me to experience over the course of

The day and night. ⁓ and part of it, ⁓ I didn't I didn't know what was coming. They it was all kind of a surprise as it came. part of it was this stretch of a few hours of pure green light. ⁓ and it was it was like at first it was you know off-putting because it was unexpected. And I was like, ooh, this feels weird. ⁓ it was like kind of like the color of a margarita. ⁓ so it I was it got me thinking about margaritas, but

Dave (42:47)
you

I'm here.

Rowan (42:55)
Then I noticed I kind of I was kind of enjoying it. I I did not work as successfully with the green light as I had with the bright white light, but it didn't matter. I was like fine. ⁓ and then they were, you know, they were checking my brain waves ⁓ throughout the day. And you can see on the charts later on, ⁓ during that green phase, I had a little spike in brain waves that tend to spike during like meditation or or inner creative work.

Dave (43:24)
Okay.

Rowan (43:24)
So

it it may be that green is good for that type of of mental process.

Dave (43:31)
So the Japanese with their forest bathing know what they're talking about.

Rowan (43:36)
Exactly, I

do. I think that it's probably like people tend to look for certain molecules that are coming out of the trees to explain the forest bathing thing. And that might be part of it. ⁓ but I think th the actual light is probably part of the explanation as well.

Dave (43:51)
I mean, isn't it wonderful that here we are in this very complex world where technology and all these things can happen and none of us really understand it. Simple things like going and standing under a tree might be one of the best things for us. We don't need to go and doom scroll through social media to see what the latest biohack might be. Just go and stand under a tree and read a book, maybe.

Rowan (44:21)
Exactly. And you can, you know, you can think of a million reasons why that might ⁓ be the case, but it it is the case, right? So it's the the solution is pretty simple in this case.

Dave (44:33)
Yeah, I think it's wonderful. Anyway, well, listen, good luck with the book launch. I'm hoping you'll come to the UK and you know, we...

Rowan (44:41)
I am

too. There's ⁓ the UK is i there's a ton of interest there. Like I it's I think my US publisher has been surprised by the surge of of interest coming out of, you know, your high latitude island. So I I'm hoping to come over.

Dave (44:56)
Well,

it's what we obsess about the weather here in the UK. I think it's because, you know, as one of my theories around why we sort of decided to create this thing called the British Empire is we wanted to go and find places with better sunshine. Ours was so terrible. But no, I mean, we're very fortunate here in the UK because we've got some really

Rowan (45:01)
Yeah.

Yeah.

Dave (45:23)
really good thinking which has been done around the subject and you know I mean I was overjoyed to see the news that a couple of hospitals in London are now putting ICU patients on rooftops so the medical establishment is picking up with the program so you know I think it's great I mean I would love it if we could get more children outside you know get the message across

Rowan (45:39)
Yeah. Yeah.

Dave (45:51)
I always think more people had dogs and were able to look after them, but took them for walks. That would probably cure a lot of things as well.

Rowan (45:52)
Yeah.

Dogs are definitely, you

know, d pr doing their share here. They're for for health.

Dave (46:08)
Absolutely. Well listen, thank you so much for joining us. It's been such a lovely conversation.

Rowan (46:14)
Thank you, Dave. It's a real pleasure.

David James Vaughan Wallace (46:15)
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