Sunlight Matters

What can a garden in the Arizona desert teach us about growing well with sunlight, shade and water? In this episode of Sunlight Matters, Dave talks to Jérémy Chevallier, a Phoenix-based permaculture designer, about planning landscapes around the conditions already there.

Jérémy explains why good design starts with observation: noticing how sunlight moves across a garden, where water collects, and which plants are already thriving. He shares how he uses sun and shade to create useful microclimates, and why choosing plants for their mature size can save years of maintenance.

The conversation also explores food forests, drought-tolerant planting, mulch and rainwater harvesting. Jérémy’s experience in a hot, dry climate has lessons for places like the UK, where water resources are under growing pressure. His central idea is simple: build healthy soil, use water thoughtfully, and design with the local environment in mind.

Dave and Jérémy also discuss using Shadowmap to understand seasonal sun and shadow, and how adding trees and other features can help landscape designers picture how a site may change over time.

In this episode:

• Why permaculture begins by observing the land
• How a garden’s sun and shade patterns change through the day and across the year
• Using microclimates to decide what to plant and where
• Food forests and the layers of a healthy landscape
• Choosing drought-tolerant plants and planning for their mature size
• How mulch, soil health and rainwater harvesting help gardens cope with heat
• Why trees and living ground cover can cool urban areas
• What desert water management can teach cities and gardeners elsewhere

This podcast does include a live demo — so video is best! 

Links

Instagram : https://www.instagram.com/permascaping/

Web : https://jeremychevallier.com/work and https://permascaping.com/

Sunlight Matters is a podcast that explores the Sun's role 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 how 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.

Please like and subscribe.

Disclaimer: Sunlight Matters is for information and general interest only. Nothing discussed on the podcast should be taken directly as medical, architectural or other professional advice.

Professor Pelle Lindqvist has followed 29,000 Swedish women for 34 years. His conclusion: in northern countries, avoiding the sun may be as risky as smoking.

About this episode

Almost every guest on Sunlight Matters has quoted Pelle Lindqvist's work. In this episode Dave finally talks to the man himself.

Pelle is a professor and senior consultant at Södersjukhuset, Stockholm's South General Hospital. An obstetrician who specialises in blood clots, he has spent the past 20 years researching a question most of medicine stopped asking in the 1980s: what are the benefits of sun exposure?

He explains how a hunting trip with an oncologist friend led to one of the field's most-cited studies. He shares new findings that melanoma risk linked to sunbeds is higher among people who also overexpose and burn. He also explains why, after 20 years, he still struggles to get funding for research on sunlight's benefits.

In this episode

• How a hunting trip started a 34-year study of 29,000 Swedish women
• New findings: why melanoma risk among sunbed users is driven by overexposure, not sunbed use itself
• Why sunbed users in the cohort had around 18% lower all-cause mortality
• How Pelle uses a sunbed for a couple of minutes a week through the Swedish winter, "not to get a tan, just to continue to be in good health"
• Beyond vitamin D: the roles of nitric oxide and endorphins
• Sun habits and blood clots, and why the problem in the north is winter, not summer
• How sun exposure made its way into Swedish guidelines for pregnant women at risk of blood clots
• Why non-smoking sun avoiders had a similar life expectancy to smokers who got the most sun
• The growing evidence on sunlight, blood sugar and type 2 diabetes
• Why research into the sun's benefits goes "against the wind", and the risk of a structural bias in the science

Sunlight Matters is a podcast that explores the Sun's role 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 how 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.

Please like and subscribe.

Disclaimer: Sunlight Matters is for information and general interest only. Nothing discussed on the podcast should be taken directly as medical, architectural or other professional advice.

What if sunlight deserves a place in the health conversation alongside sleep, exercise, and nutrition? And how do we weigh its potential benefits against the very real risks of too much exposure?

In this episode, Norwegian GP and author Torkil Færø joins Dave and Georg to discuss The Sun Cure, his latest book on sunlight, circadian rhythms and health. Torkil describes how his views changed after years of assuming sunlight had little benefit beyond vitamin D. He now believes its influence reaches much further, affecting a range of processes in the body, though many questions remain open to research and debate.

Georg shares what happened during his three-week sunrise experiment in Vienna. He used Shadowmap to find places to watch the sun rise, then tracked his light exposure and several health measures. He reports that his heart rate variability rose by 13%, his resting heart rate fell by 8%, and his Whoop recovery score improved by 25%. Torkil explains what HRV can tell us about the body’s response to stress and recovery, while the conversation considers what wearable data can—and cannot—show.

The discussion also examines skin cancer and how risk is communicated. Torkil questions how to interpret the gap between rising melanoma diagnoses and comparatively stable mortality, suggesting that changes in detection and diagnosis may be part of the picture. Georg brings a personal perspective, describing his diagnosis and how it changed his relationship with the sun. Together, they explore the tension between advice to avoid sun exposure and research into sunlight’s wider effects.

They discuss sunscreen, shade and sunburn, as well as the importance of distinguishing between different kinds of evidence. The episode does not offer a simple answer to the skin cancer debate; it asks how medical guidance is formed, how strongly it is supported, and how it might account for both the harms and possible benefits of sunlight.

In this episode

• Why Torkil began questioning what he had been taught about sunlight
• Georg’s sunrise routine in Vienna and the health measures he tracked
• What heart rate variability may reveal about recovery and physiological stress
• Sunlight, circadian rhythms and their possible effects across the body
• Why melanoma diagnoses have risen, and how that compares with mortality trends
• The role that screening, detection and overdiagnosis may play in those figures
• Georg’s experience of skin cancer and his changing relationship with sun exposure
• How to think about sunscreen, shade, sunburn and individual circumstances
• Why the sunlight debate can produce sharply different readings of the research
• Whether wearable technology and light-based products could bring more attention to sunlight

Sunlight Matters is a podcast that explores the Sun's role 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 how 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.

Please like and subscribe.

Disclaimer: Sunlight Matters is for information and general interest only. Nothing discussed on the podcast should be taken directly as medical, architectural or other professional advice.

What makes a house feel like home? It is not simply the number of bedrooms, the size of the kitchen or the asking price. It is also the light that comes through the windows, the way the rooms feel throughout the day and whether the morning sun reaches the places where we live, work and wake up.

In this episode of Sunlight Matters, Dave Wallace and Georg Molzer are joined by Ariel Dos Santos, Chief Product and Design Officer at Redfin — one of the largest property platforms in the United States, with around 50 million monthly active users.

Ariel explains how Redfin is moving beyond showing people what a property looks like to helping them understand what it might actually be like to live there. That means bringing together information about neighbourhoods, climate, environmental risks and, increasingly, sunlight.

We hear how the partnership between Redfin and Shadowmap led to the launch of Sunscore: a simple property-level measure that helps buyers understand a home’s access to sunlight, with the option to explore the detail at different times of day and throughout the year.

Ariel also shares Redfin research showing that 67% of US residents consider sunlight an important part of how satisfied they are with their home. The conversation explores whether sunlight could eventually influence property values, how better environmental data can give estate agents new “superpowers”, and why buyers need this information before they move in — not after.

The discussion also looks further ahead. Could we identify the best places in a neighbourhood to find the morning sun? Could property searches eventually show whether sunlight will reach a particular bedroom window? And might greater awareness encourage architects and developers to design brighter, healthier homes?

Along the way, Ariel talks candidly about Redfin’s culture of experimentation, what it means to be a genuine pioneer, and why companies cannot expect people to take risks if failure is punished.

And, on a more personal note, he explains why he will always choose sunrise over sunset — and describes the rare moments when sunlight, cooking and discovering a great piece of music come together perfectly.

In this episode:

• How Redfin serves buyers, renters, sellers and homeowners across the entire property journey
• Why property search must explain what a home is like to live in
• The research showing how much sunlight matters to homeowners
• How Redfin and Shadowmap developed Sunscore
• Why a simple score can make complex sunlight data understandable
• How people use property information differently as they get closer to buying
• The possible relationship between sunlight and property value
• Using sunlight data for gardens, renovation and solar energy decisions
• The idea of community “sunspots” for finding morning light
• How better data could help architects create brighter homes
• Redfin’s approach to innovation, collaboration and intelligent risk-taking
• Why Ariel is firmly on the side of sunrise

Sunlight Matters is a podcast that explores the Sun's role 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 how 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.

Please like and subscribe.

Disclaimer: Sunlight Matters is for information and general interest only. Nothing discussed on the podcast should be taken directly as medical, architectural or other professional advice.

In this episode of Sunlight Matters, Dave speaks with Professor Sean Cain, a leading researcher in circadian rhythms, light and mental health. His research points to a striking pattern: brighter days are associated with a lower risk of depression, while greater exposure to light at night is associated with a higher risk.

Drawing on data from nearly 89,000 people, Sean explains why the timing of light matters as much as its brightness. He also shares remarkable early results from a simple intervention involving brighter days and dimmer evenings, which helped participants move from severe to mild depression in just four weeks.

The conversation explores why depression may genuinely feel like darkness; how antidepressants could change our sensitivity to light; and why modern life leaves us spending our days in dim indoor “caves”, followed by nights bathed in bright, blue-enriched light.

Dave and Sean also put the MiEye wearable light sensor to the test, uncover the near-infrared benefits of old windows, and challenge one of the most common pieces of jet-lag advice: getting outside as soon as you land.

Because when it comes to light, the right advice at the wrong time can make things worse.

In this episode:

• Why light at night may increase the risk of depression
• How bright daytime light strengthens the body’s circadian rhythms
• The fascinating connection between depression and metaphors of darkness
• Why antidepressants may alter the way the circadian system responds to light
• How a simple home-lighting intervention produced potentially life-changing results
• Why morning light matters — but missing sunrise does not mean you have missed your chance
• What nearly 89,000 UK Biobank participants revealed about light and mental health
• How MiEye measures the biological effects of visible and near-infrared light
• Why modern windows and LEDs may be changing our light environment
• How citizen science could transform our understanding of light and health
• Why “get natural light when you land” can be terrible jet-lag advice
• How the time of your flight could determine how badly jet lag affects you

This is a conversation that may permanently change how you think about the light around you — not simply as something that allows us to see, but as a fundamental biological signal telling every part of the body what time it is and what it should be doing.

Sunlight Matters is a podcast that explores the Sun's role 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 how 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.

Please like and subscribe.

Disclaimer: Sunlight Matters is for information and general interest only. Nothing discussed on the podcast should be taken directly as medical, architectural or other professional advice.

What if sunlight is one of the most overlooked influences on our mental health?

In this episode of Sunlight Matters, Dave speaks with Kristen, a registered occupational therapist, trauma practitioner and quantum biology health coach. Drawing on her clinical work in mental health and her own experience of improving her sleep and energy, Kristen explains why morning light, daytime outdoor exposure and darkness at night may all play an important role in supporting our circadian rhythm and emotional wellbeing.

They discuss practical ways to build a healthier relationship with light, from stepping outside soon after waking and taking short outdoor breaks during the day to reducing artificial light in the evening.

The conversation also explores the relationship between circadian disruption and conditions such as anxiety, depression, ADHD and bipolar disorder, including emerging research into dark therapy and blue-blocking glasses. Kristen describes why supporting people to get outdoors can be difficult when they are already struggling, and why small, achievable changes are often the best place to begin.

But this episode is about more than biology. Dave and Kristen reflect on the joy of sunrise, the calming sound of birdsong and the unexpected encounters with wildlife that happen when we slow down and pay attention. Reconnecting with light, they argue, can also reconnect us with our bodies, the natural world and a sense of belonging.

As Kristen puts it:

In this episode

• Kristen’s work as an occupational therapist in mental health
• How her own experience of poor sleep led her to explore circadian health
• Why morning light is the foundation of her approach
• The importance of darkness and reducing artificial light at night
• Research into dark therapy and blue-blocking glasses for bipolar mania
• Light sensitivity, ADHD, dopamine and anxiety
• Why getting outdoors throughout the day matters
• The different roles of morning light, UVA and UVB
• Building outdoor time into a busy working day
• Why modern indoor lifestyles can leave us disconnected
• The mental health benefits of nature, birdsong and moments of wonder
• How small changes can help people rebuild a healthier daily rhythm

Chapter guide

01:09 — Meet Kristen
Kristen introduces her work in occupational therapy, trauma therapy and mental health.

03:42 — A personal journey into circadian health
How disrupted sleep during perimenopause led Kristen to explore morning light and daily rhythms.

06:09 — Using light in mental health practice
Practical ways Kristen encourages clients to spend more time outdoors.

07:00 — Darkness, bipolar disorder and mania
A discussion of dark therapy, blue-blocking glasses and emerging clinical research.

10:29 — Are some people more sensitive to light?
Kristen explores light sensitivity, ADHD and the effects of artificial blue light.

14:04 — Why one dose of morning light may not be enough
Dave shares what he has learnt from tracking his light exposure throughout the day.

16:25 — UVA, UVB and vitamin D
The changing spectrum of sunlight and the importance of regular outdoor exposure.

24:53 — Why sunshine can feel so good
Dave describes the profound sense of wellbeing he experiences after swimming and warming up in the sun.

28:22 — The overlooked magic of sunrise
Why something so simple, free and widely available can still be difficult to incorporate into daily life.

33:29 — Sunset, metabolism and anxiety
The relationship between light timing, sleep, cortisol and metabolic health.

37:32 — Light, water and magnetism
Kristen explains the three pillars of quantum biology and the value of reconnecting with nature.

39:04 — From sunlight to environmental connection
How spending time outdoors can deepen our desire to protect the natural world.

41:59 — Why birdsong can calm us
Dave and Kristen discuss the Merlin Bird ID app and the evolutionary significance of hearing birds.

45:33 — Is circadian health about to become mainstream?
Kristen explains why she believes our understanding of light and physiology is approaching a turning point.

47:57 — Listening to the body
The episode concludes with a reflection on self-trust, belonging and honouring our natural desire for connection.

Find out more about Kristen:

Online: https://kristengilbert.ca/

Instagram: www.instagram.com/sunhunter_cv

YouTube: https://www.youtube.com/@Sunhunter_cv.

Subscribe on your preferred podcast platform and visit shadowmap.org to learn more about sunlight analysis, solar exposure and designing spaces around natural light.

This episode discusses personal experiences and emerging ideas about light and health. It is intended for general information and should not replace individual medical advice. People should follow appropriate clinical and public-health guidance, particularly in relation to mental health treatment, eye health, medication, sun exposure and skin-cancer prevention.

Sunlight Matters is a podcast that explores the Sun's role 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 how 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.

Please like and subscribe.

Disclaimer: Sunlight Matters is for information and general interest only. Nothing discussed on the podcast should be taken directly as medical, architectural or other professional advice.

What if better health begins not with another device, supplement or complicated routine, but with something far more fundamental: reconnecting with nature?

In this episode of Sunlight Matters, Dave Wallace speaks with Nathan Siles, a biophysics specialist focused on foundational health. Nathan’s interest in the subject is deeply personal. Legally blind following retinoblastoma as a baby, he later faced another cancer diagnosis at 24. Those experiences led him to explore the relationship between light, environment and human biology.

Nathan argues that sunlight is not simply a source of vitamin D. It is an environmental signal that helps regulate our circadian rhythm, hormones, mitochondrial function, mood and energy. Sunrise prepares the body for the day, while the timing and quality of the light we encounter can be as important as the amount we receive.

The conversation also explores Nathan’s experience of living in Melbourne, where significant lifestyle changes and greater sun exposure initially failed to improve his vitamin D levels. After moving much closer to the equator, he says those levels doubled within three months. This raises a wider discussion about latitude, altitude, urban environments and the many factors that may affect how our bodies respond to sunlight.

Nathan is sceptical of the increasingly complex wellness industry. While modern tools may have a place, he believes they are approximations of something nature already provides freely: sunlight, fresh air, contact with the Earth, natural food, movement and time in green spaces.

As he puts it: “Nothing will replace the Sun.”

In this episode

Dave and Nathan discuss:

• Nathan’s experience of childhood cancer, blindness and a second cancer diagnosis at 24
• Why his health journey led him towards biophysics and foundational health
• The difference between merely being in the Sun and being biologically able to use its energy
• Why sunrise acts as an important signal for the body
• The influence of latitude, altitude and season on sunlight exposure
• The relationship between light, mitochondria, dopamine and circadian rhythms
• Why changing your environment can sometimes be as important as changing your behaviour
• Nathan’s concerns about artificial light, Wi-Fi and electromagnetic fields
• Grounding, cold exposure and reconnecting physically with nature
• Why expensive wellness technology cannot fully reproduce the natural world
• The importance of food, movement, green space and everyday contact with the outdoors
• How simple environmental changes can form the foundations of a healthier life

A central idea

Throughout the conversation, Nathan returns to one compelling principle:

“You can’t get well in the same environment in which you became sick.”

His message is not that modern technology has no value, but that it should not distract us from the biological foundations on which human health was built. We evolved with sunrise, darkness, seasonal change, natural landscapes and direct contact with the Earth. A century spent increasingly indoors does not erase billions of years of evolution.

About Nathan Siles

Nathan Siles is a biophysics specialist whose work explores foundational health through the relationship between the body and its environment. His perspective brings together biophysics, biomechanics and psychological and spiritual wellbeing.

Nathan is also a co-author of Biotra, written with chiropractor Nick Dawr and psychotherapist Ryan Baracloff.

BioTra: An Approach to Healthy Living in a Modern World. A practical framework for understanding health through the lens of mitochondrial biology, circadian rhythms, light, water, nutrition and our relationship with the natural environment. https://biotra.com.au

Nathan is running an Immersion Session in Mexico

BioTra Immersion, Tulum, Mexico (27 October to 1 November): A six-day, five-night educational experience designed to help people reconnect with nature while exploring mitochondrial biophysics, biomechanics, psychospiritual wellbeing, circadian health and the foundations of a nature-aligned life. https://biotra.com.au/immersion

The takeaway

Health has become an enormous and often bewildering marketplace. Yet Nathan’s advice is refreshingly simple: spend more time outside, see the morning light, move through green spaces, reduce unnecessary technological exposure and allow the natural world to do what it has always done.

Nature is not an optional addition to human health. It is the foundation.

This episode discusses personal experiences and health-related ideas that may not reflect established medical consensus. It is intended for general information and should not replace professional medical advice.

Sunlight Matters is a podcast that explores the Sun's role 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 how 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.

Please like and subscribe.

Disclaimer: Sunlight Matters is for information and general interest only. Nothing discussed on the podcast should be taken directly as medical, architectural or other professional advice.

Hunting the Sunrise: What Happens When You Live by the Sun?

Most of us instinctively believe we know the difference between indoors and outdoors. But while a typical indoor space might provide 300 lux of light, even an overcast sky can expose us to around 10,000 lux. On a bright summer’s day, that figure can rise to 100,000 lux.

Our eyes adapt so effectively that the difference may not feel dramatic. Our bodies, however, know exactly where we are.

In this episode of Sunlight Matters, Shadowmap’s Georg puts his own body to the test. For three weeks, he is getting up before dawn, travelling across Vienna to watch and film the sunrise, and examining what happens when he begins living in closer alignment with the natural cycle of light and darkness.

Guiding the experiment is daylight and sleep researcher Nicholas Witton, whose work explores how visible and non-visible light affect human sleep, behaviour and biology.

The experiment

Georg has committed to watching the sunrise outdoors every morning for three weeks. Alongside a detailed personal diary, he is using:

•  A wearable light sensor recording different wavelengths of light every 30 seconds, including melanopic light and near-infrared exposure 
•  Salivary cortisol and melatonin testing 
•  Continuous monitoring of sleep, heart rate, heart rate variability, stress and physical activity 
•  Blood tests taken before and after the experiment 
•  Established sleep and chronotype assessments 

The experiment also coincides with a highly restricted diet that excludes meat, salt, sugar, heated oils, tobacco and stimulants. That makes this citizen-science project fascinating, although not a controlled clinical trial: any changes cannot necessarily be attributed to morning light alone.

What Georg has experienced so far

After an initially difficult adjustment, Georg describes noticeable changes in his energy, productivity and relationship with sleep.

On his best morning, after a particularly good night’s rest, he watched the sunrise, meditated, swam and cycled back into Vienna feeling almost “high” with energy. He is procrastinating less, working more efficiently and organising his day around protecting his bedtime.

Perhaps the most profound change is psychological. After years of unreliable sleep and sometimes dreading bedtime, Georg is beginning to look forward to it and trust that he will sleep well.

There are trade-offs. Rising at around 4.30 am makes evening socialising almost impossible, and the early days brought fatigue, sleep debt and the occasional need for a substantial nap. But after his first week, the routine is already beginning to feel more natural.

Are our cities designed to keep us from the Sun?

One of the experiment’s unexpected findings is just how difficult it can be to see the sunrise in a city.

Buildings obscure the horizon. Parks and cemeteries remain locked until long after sunrise. Rooftops are inaccessible, and many of the best views belong to people living in elevated apartments or on the outskirts.

Georg uses Shadowmap to identify the parts of Vienna that will receive direct sunlight shortly after dawn. He then works out whether he can physically reach them, sometimes successfully and sometimes not. One failed attempt involved a locked cemetery, climbing onto a hut and a characteristically Austrian encounter with a member of staff.

His experience raises a serious question for architects and urban planners: if access to morning light is important for our health, should cities provide places where everyone can experience it?

As Georg puts it, sunlight should not become a privilege reserved for those living on the upper floors.

What we discuss

•  Why modern humans spend roughly 90% of their lives indoors 
•  The enormous difference between indoor and outdoor light 
•  How artificial lighting disrupted our relationship with the solar day 
•  Why morning light helps synchronise our biological clock 
•  Cortisol, melatonin and the body’s transition between sleep and wakefulness 
•  Whether morning people and night owls once helped protect early human communities 
•  How industrialisation imposed standard working and sleeping times 
•  The effects of “social jet lag” 
•  Why sleep is usually the first thing we sacrifice 
•  The value of short power naps and complete 90-minute sleep cycles 
•  Georg’s changing mood, energy, productivity and attitude towards sleep 
•  Why viewing the sunrise may offer something beyond simply being outdoors 
•  The difficulty of finding direct morning sunlight in a modern city 
•  How Shadowmap can help people hunt for accessible sunrise locations 
•  The responsibility of architects and planners to design more sunlight-conscious cities 
•  What the team hopes to discover when Georg’s biological and light-exposure data arrive 

A tomato plant under the stairs

Nicholas offers a memorable description of modern life: we have become like tomato plants kept beneath the stairs rather than beside the window.

We can alter what we eat, how much we exercise and when we go to bed. What we cannot change is the body’s fundamental relationship with light. Yet through artificial illumination, indoor living and urban design, we have created environments that allow us to behave as if that relationship no longer matters.

This experiment asks what might happen if we begin paying attention to it again.

This is the first instalment documenting Georg’s three-week experiment. In the follow-up episode, we will examine the light data, sleep records, hormone measurements, blood results and personal diary to see whether the biological evidence matches his lived experience.

Sunlight Matters is a podcast that explores the Sun's role 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 how 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.

Please like and subscribe.

Disclaimer: Sunlight Matters is for information and general interest only. Nothing discussed on the podcast should be taken directly as medical, architectural or other professional advice.

If you've ever seen a photo of the Sun that stopped you in your tracks, there's a very good chance Andrew McCarthy took it. His image of our star is the first thing you see when you open the Shadowmap story, and it's the artwork behind Sunlight Matters itself. So this one is personal.

Andrew is the Arizona-based astrophotographer behind some of the most iconic space images of recent years, including Icarus, his jaw-dropping shot of a skydiver falling in front of the sun, named one of the photos of the year. In this episode, he tells the full story of how it was pulled off: an ultralight plane, a dry lake bed in the Arizona desert, months of maths, and one last-chance jump.

We also get into:

• How a cheap Dobsonian telescope and a blurry photo of the Orion Nebula changed his life
• Why space isn't grey, and the misconceptions that almost everyone (including Andrew) starts with
• What you can actually see with a pair of binoculars, from the Andromeda galaxy to the Large Magellanic Cloud
• How he photographs the sun in hydrogen alpha to reveal the chromosphere, convection cells the size of Texas, and plasma jets thousands of miles long
• The moon photo that went viral, ended up on the side of NASA's Artemis I rocket, and led to an extraordinary collaboration with Artemis II commander Reid Wiseman, which showed the hidden colours of the moon, revealed for the first time from photos taken in lunar orbit, and the print release that raised $40,000 for cancer research at MD Anderson
• Why watching a Starship launch hits you like a ton of bricks (literally), and his advice for anyone who wants to see a rocket launch for themselves
• His plans for the 2026 total solar eclipse over Iceland and Spain, which he intends to shoot from a boat
• And a few tips for my own 4 am sunrise photography habit

Andrew's mission is simple: to show you the universe as if you had superhuman vision, and to inspire the next generation of astronauts, engineers and stargazers. Job done, frankly.

Follow Andrew

• Instagram: @cosmic_background
• Website: cosmicbackground.io
• X: @AJamesMcCarthy

Sunlight Matters is a podcast that explores the Sun's role 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 how 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.

Please like and subscribe.

Disclaimer: Sunlight Matters is for information and general interest only. Nothing discussed on the podcast should be taken directly as medical, architectural or other professional advice.

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 that explores the Sun's role 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 how 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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Disclaimer: Sunlight Matters is for information and general interest only. Nothing discussed on the podcast should be taken directly as medical, architectural or other professional advice.