Episode 6

Lights in the darkness:

Building a world where we can see the stars.


“More people than ever are becoming aware of light pollution, not only in how it causes harm to our world, but how easy the problem is to solve. When they make the choice to reduce light pollution, they'll see immediate results. It's the only environmental pollutant that leaves the scene at the speed of light, as soon as the pollution stops. In a world where we face big and serious problems that may take generations to fix, this one is a no-brainer in comparison.”

John Barentine, Principal Consultant, Dark Sky Consulting, Inc., astronomer and researcher

"When they make the choice to reduce light pollution, they'll see immediate results."

In this episode

The night sky, ever present, but have you looked up at it lately? What can you see when you do?

Depending on where you are in the world, the stars may shine bright for you, or you may be one of many finding night sky constellations obscured through a film of hazy light pollution.

As electric light spills from every asset in our built world, what can we do about its lasting impacts for both our natural world and every creature in it?

In this episode of Changing Places, host Mariam Sobh discusses the current state and future of the night sky with guests Gregory Francis, Director, Rights of Light at Avison Young, and John Barentine, Principal Consultant, astronomer and researcher with Dark Sky Consulting, Inc.


  • 10:38 Gregory Frances shares how London’s prepared to combat light pollution, and how common principles apply to other major cities in the UK as well.  
  • 22:41 John Barentine discusses Tucson’s light pollution reduction methods and how they’ve benefitted the city.
  • 24:21 John Barentine notes light pollution as an issue that can be solved quickly, compared to other pollutant issues.

Click here to expand transcript

Speaker 1 [00:03] I've come down to London's beautiful Hampstead Heath at the end of a very hot day, and I'm looking to talk to some people about the night sky.

Speaker 2 [00:11] You forget what stars look like when you don't leave London for a while.

Speaker 1 [00:14] Yeah.

Speaker 2 [00:14] And it's always a big shock when you leave the city. There's loads of stars. This is what you're supposed to see when you look up, but now I'm used to it. You forget it's part of life looking up and looking at stars in London a bit.

It makes me sad, but I also understand the realism of it. It does make me sad, but I understand this is the choice of living in the city with 10 million people. There's a lot of lights.

Speaker 3 [00:35] I really like the nice sky and I never see it because I live in London.

Speaker 1 [00:38] Yeah. Yeah.

Speaker 3 [00:39] So, when I'm on a holiday, it's an incredible experience to actually see the stars.

Speaker 1 [00:44] Yeah.

Speaker 3 [00:44] And yeah, I definitely regret that this is the case in London. Yeah, I don't think about the amazing glow of the city. I think about how the glow of the city is destroying the amazing glow of the universe.

Speaker 1 [00:54] Yeah.

Speaker 4 [00:56] I think something is lost when you can't see stars at night, because I think it's just such a simple joy in life is being able to look up at the night sky. And I don't think it's too much to ask, because even in our homes, I don't think people like harsh lighting. People enjoy warm and soft lighting, so why wouldn't we do the same out and about?

Mariam Sobh [01:16] When was the last time you looked up at the night sky? What did you see? The Big Dipper? The Little Dipper? Orion's Belt? Maybe even the blinking lights of the International Space Station just on the horizon. Or if you live in, near, or within close proximity to one of the major urban cores around the world, you may have seen a dull orange hue illuminating the night sky with only the clock to signify that, yes, it was the middle of the night. What is lost if we look to the stars, the very thing that led sailors home or provoked a million thoughts about our place in space, time and beyond, and we can't see them? Is light pollution from the built world at the price of star- filled nights, the ultimate buy in for our modern existence? Or are the issues and reasoning behind our illuminated night skies, more delicate than we realize?

In 2016, Science Advances noted that 99% of the US and Europe live under light polluted skies with 80% of North Americans and 60% of Europeans unable to see the Milky Way. National Geographic recounted in 2019 that, after the 1994 Northridge earthquake, the site of the Milky way hovering over Los Angeles startled residents who called emergency services about the mysterious cloud hanging over the city. Moreover, the BBC notes that exposure to artificial light at night has been linked to diabetes, certain cancers, and mood disorders. Lastly, in 2021 Ruskin Hartley, the CEO of the International Dark Sky Association, told the BBC every single creature that has been studied in terms of the relationship between light and those creatures habits has found detrimental impacts.

With our love for electric light, how has that dependency affected the natural world, which moves around us and lies within our circadian rhythms? Is there a way to have our light and keep it out of the night sky? Or are we too far gone into the void that changing one of the aspects which makes our built world possible, is one ask too much? I'm Mariam Sobh. This is Changing Places.

In order to understand how we got here, I'm going to chat with Gregory Francis, Director, Rights of Light and Daylight/ Sunlight, Avison Young, about how the built world is working to improve its relationship with the night sky. Throughout this episode, we'll hear from an expert in the field of dark sky research, Dr. John Barentine, Executive Director and Principal Consultant, Dark Sky Consulting, LLC, and we'll learn more about the state of the night sky and its future.

Gregory Francis, welcome to Changing Places. Gregory, if we look at modern cities, buildings, and most downtowns, they're illuminated at night. Places like Times Square come to mind. If we take a step back, how does light pollution affect not just that immediate area, but even towns 50 to 100 miles away?

Gregory Francis [04:16] That's a great question. So, taking your example of Times Square or a similar area in London, such as Piccadilly Circus, clearly any visitors in those areas know what to expect or are actively seeking to experience the bright lights of the city. As such, in terms of the immediate area, I would argue that the amount of lighting is intentionally high and therefore appropriate for that context. However, as you suggest, an issue can arise when this then unintentionally affects other areas of a very different character. So if unchecked, bright illumination from the immediate area can bounce off surfaces, such as nearby buildings and the ground with some, a light then reflected upwards, and therefore contributing to what is called sky glow. And this cumulative sky glow can be visible from many miles away from the actual source itself, particularly against a dark backdrop on a clear evening.

Mariam Sobh [05:10] That's disheartening a little bit to hear, I think, for folks who really care about the night sky. If we look even deeper into areas within places like London that have green spaces like Hampstead Heath, how do we separate the illumination from the city versus the village-like feel of Hampstead?

Gregory Francis [05:26] Yes, we've got these areas that are pretty much side by side. If anyone knows Hampstead, it's very much like a green oasis in the middle of a very dense, major world city. And keeping those two conflicting characteristics complete and intact is a challenge. How do you deal with Hampstead Heath and how do you deal with the surrounding areas?

Mariam Sobh [05:47] Greg, I'm curious about containing light pollution. Is there a way for a place like London or any other city to be able to contain light pollution into just its downtown or business district, versus it creeping out into more residential areas?

Gregory Francis [06:02] Yes, a good question. Again, this comes down to the local management, I think, of the environmental zones and then further ensuring a good lighting design as part of any new development through the policy or even installations.

For example, in the UK, we've got the Clean Neighborhoods and Environment Act of 2005, which officially made prejudicial artificial lighting a potential statutory nuisance, enforceable through the courts. And just as a general principle, good lighting design doesn't seek to eliminate artificial lighting, but seeks to aim to manage it effectively, whether it's in new designs or in existing installations.

Mariam Sobh [06:43] I guess what I'm wondering is people's homes, businesses, they have their lights on sometimes throughout the evening. Is there anything that would be able to contain that, whether it's, as you mentioned councils, but also is there any technology that could contain the light?

Gregory Francis [06:59] Yeah, absolutely. They say good luminaire normally has built in features to ensure that it only lights the area that's intended. The direction of the luminaire itself, ensuring that it only lights downwards and not upwards and outwards. There's things called cowls or baffling that you can add to lights and things such as timer switches on lights. And yeah, as I say, good lighting design should, in theory, mean that the light's only where it's needed and not spilling out to where it's unwanted and undesirable.

Mariam Sobh [07:29] Should we go back to using candles?

Gregory Francis [07:31] Candles have got their place. I like a candlelit dinner as much as anyone else. But yeah, they have their own issues. For example, fires and public spaces can't be lit by candles, that sort of thing. So, candles are always going to have their place. I think they're great. They have a soft glow, but it's lovely. I think artificial lighting is relatively young. I think we can tend to forget that. It's not that old a technology. It's come on leaps and bounds. And I think as we go forward, we're going to learn more about lighting. It's probably more energy efficient, but we've got dimmer switches, that sort of thing. So yeah, I think candles still got their place, but the artificial lights was here to stay. Not in this current form, but in an evolved format, I think.

Mariam Sobh [08:13] Speaking about lighting for homes, what is the optimal night lighting for a home that everyday people can implement today?

Gregory Francis [08:19] Most issues with regards to domestic lighting tend to occur with outdoor installations. So if you've got lighting in your backyards or security lighting, which is an important aspect of external lighting, it's just making sure that they point downwards as much as possible. That you adjust it, look at it. Is it lighting the area you intended it to light? If not, it should be adjustable either in terms of intensity or perhaps the angle at which it faces to make sure it only really lights the area that you want it to.

Things like the surfaces that it reflects off or have a role to play. But it's really just being the general common sense and consideration, really, about making sure that the light is only as strong as it needs to be and only light's the area that it needs to. I think that's a good, simple approach that pretty much everybody can apply, I hope.

Mariam Sobh [09:08] Greg, I'm curious what you think about how London is taking a proactive stance towards its relationship with light pollution, after we hear from Dr. John Barentine.

John Barentine [09:18] It's just after midnight, and I'm speaking to you from the backyard of my home at the edge of Tucson, Arizona. When I look up towards the east, I faintly see the Milky Way arcing high overhead. To the west is what we call a light dome, a semi- circular glow in the night sky. The sky is much darker. Or the Santa Catalina and Rincon Mountains halted the city's growth in those directions.

On a clear night in the fall when I look to the northeast, I can just make out the Andromeda Galaxy, whose visibility is an indicator of the quality of my sky. Compared to most other cities at size, Tucson is much more conscientious about the impact of its lights on the night sky. Tucson has sought to keep conditions in the area favorable for astronomy and space science, and it has one of the best outdoor lighting ordinances among mid- sized cities in all the United States.

By carefully dealing with outdoor lighting, it has managed to decrease light pollution a little, even as the city's population continues to grow at just under 1% per year.

Mariam Sobh [10:21] Greg, if we take a step back, do you think London's prepared to reign in light pollution from new entertainment venues, airports, office buildings, et cetera, to curb this issue? Or is that some kind of progress that would be too great to make a difference now?

Gregory Francis [10:38] London and other world cities, they've always been progressive, exciting, and dynamic. That's not going to change, I don't think. What I do think is that all these world cities, particularly London, tries to be responsible alongside being progressive, exciting, and dynamic.And the approach in London that I've seen as part of my work here is to really try to find the sensible middle ground where the potential negative effects of light pollution are identified and effectively managed, while still also allowing the city to evolve and maintain its edge. You mentioned London, but I just should say that we have lots of large cities in the UK, such as Manchester, Birmingham, Liverpool, and Bristol. And all of those same principles apply very much so to them, as well.

Mariam Sobh [11:19] Greg, for folks who aren't in the industry, what is a light pollution assessment and what are some of the attributes you are trying to understand when you undertake this assessment?

Gregory Francis [11:27] We're fortunate in the UK to have a whole range of best practice guidance notes for lighting design, underpinned by a rigorous town planning system and wider legislation. So these best practice guidance notes help us to identify when poor lighting design spills beyond the boundary of the area being lit, which is something in the industry we call obtrusive lights, which is also interchangeably referred to as light pollution.

In a nutshell, the two main, potentially problematic, types of intrusive light are light intrusion, which is the uncontrolled spillage of artificial light to nearby dwellings and premises. And secondly, sky glow, which is the brightening of the night sky. There are lots of other different types of obtrusive light, but those are the two main ones that have arguably the biggest effect and need to be managed most effectively.

So for light intrusion, simply the assessment's aim is to first appropriately categorize the environmental zone and context, so that's going back to what we were saying about making sure we categorize the zone itself. So, that's the first stage.And then secondly, considering whether the lighting installation's effect would be appropriate or within acceptable limits for that particular environmental zone context. If the installation is a proposed one, so it just exists on paper or computer screen, we'd undertake that by computer modeling and assessment simulation. Or if the installation is actually existing and is a cause for concern, then, of course, we can use direct measurements using light meters for those to measure how much light is being projected onto windows nearby.

For sky glow, the aim is to assess the what's called the upward light ratio. And that's just a fancy term for the percentage of light from an installation, which goes directly into the sky and therefore cumulatively contributing to the sky glow. Again, this is usually modeled by computer analysis for proposed installations and direct measurement for existing ones. And those are the standard basic methods, but there are variety of other approaches that we can take if a more bespoke or tailored assessment is required in addition to those, to make sure it's adequately considered.

Mariam Sobh [13:43] Stay tuned for the next part. And just a reminder, Changing Places is a podcast brought to you by Avison Young that continues to explore and question our complex relationship with the built world around us. I'm your host, Mariam Sobh, I hope you're liking the show so far. If so, please share Changing Places with your friends.

Welcome back to Changing Places. Before we get back to my conversation with Gregory Francis, let's go back to London's Hampstead Heath to hear what folks think about light pollution in their hamlet.

Speaker 5 [14:17] I think I do think about light pollution, because lying out in a field like Hampstead Heath and looking up at the stars, there's something so magical about it. And it's just taken, because of all the light pollution that's affecting your view.

Speaker 6 [14:31] There's so many skyscrapers, huge buildings, that keep their lights on at night that don't really have to. But at the same time, it's part of London, which personally I like the view at night of the city. I think there's so many office buildings, so many huge, huge buildings that just don't need to have their lights on. I personally would like to see the stars more, but it's also a treat going into the countryside and appreciating them more.It's a sad sign that by choosing to live here, we just know that we won't see the stars. Because it's something that I love. I love being in nature.

Speaker 7 [15:05] I guess light pollution is a byproduct of modernity. It's innovation and urbanization is just always going to lead to such a thing, so I think it does have to be taken into consideration when living in such an urbanized city.

Mariam Sobh [15:17] Now back to my conversation with Gregory Francis, Director, Rights of Light and Daylight/ Sunlight from Avison Young. Greg, I know you've dealt with the new project, Madison Square Garden Sphere, which is slated to open in London in 2023. It's said that the sphere will require 36 million LED lights, which may be unlike anything ever seen before in Europe.

Gregory Francis [15:38] Yeah.

Mariam Sobh [15:38] That's a lot of lighting. How is London handling the potential sky glow light pollution from this project along with the already existing light pollution in the city?

Gregory Francis [15:47] Yeah. Yes. So, like we don't have an issue already. Yes, part of my work at Avison Young, I've had the privilege to be involved with this project. This will be a 21,500 capacity venue in London with the joint largest and highest resolution programmable LED screen in the world, measuring two hectares or five acres of surface area, which is absolutely enormous. And I say joint, because it's a direct twin of the MSG Sphere at the Venetian in Las Vegas. In answer to your question, Mariam, London handled this via a very long and detailed consultation and planning process. The applicants Madison Square Garden had to undertake a very detailed environmental impact assessment, which considered all the potential environmental effects of the proposal, including, of course, light intrusion and sky glow.

Mariam Sobh [16:36] When it comes to this project, this sphere, it's in the flight path of London City Airport.

Gregory Francis [16:42] Yeah.

Mariam Sobh [16:42] Is that going to cause any issues surrounding light pollution at night? And how can it remain unobtrusive to the air traffic controllers?

Gregory Francis [16:49] Yeah. Another great question. In the UK, we have a rigorous set of procedures under the banner of aviation safeguarding and also as part of the planning process, I think, the airport, what we call statutory consultees, so they have to be consulted where it's deemed that there could be an issue that's less obvious, let's say, to people who don't work in aviation to enable the aviation authorities who are specialists in this field to pose whatever questions they need to, to make sure that all concerns are adequately addressed and informed. I know that the sphere development is bound by limits on its maximum output capacity. For example, you've just said, it's got so many LEDs. It's got 36 million LED lights. Can you imagine if that's switched up to maximum, fully white? It's going to be a real... I've had it described as a beast, a real beast of an installation.

So, there's been... Necessarily needs to be limits on its maximum output capacity. And there's been lots and lots of detailed assessments with regards to its ability to interfere with the pilot's visibility, taking assessments at certain altitudes, and the flight path angles into London. And modeling all of those to take those into account and then any mitigation was applied as necessary. For example, as I say, the maximum output and there's effectively strict limits on that. And those have been produced in conjunction with the aviation authorities and the operators of London City Airport, and also probably Heathrow and Gatwick as well, which are slightly outside the city but probably also consulted, just in case.

Mariam Sobh [18:31] One thing that we touched upon earlier in the conversation was about Earth Day and how we shut off our lights for a day or an hour in the evening. I can't remember exactly what the rules are for that, but do you think we need more Earth Hours? Maybe an Earth week where these big metropolitan cities around the world turn off their lights for a whole week instead of just a night?

Gregory Francis [18:51] Humans, we;re odd, aren't we? I think the Earth Hour is intentional, but for example, I don't know if this happened this year, but a few years ago there was a major power outage in New York, I believe. And I think some people in those situations would've appreciated the sudden abundance of night sky visibility in the absence of night glow. But on the other end of the scale, I imagine there's others who are hardcore urban dwellers that can't wait to get back to feeling like they're in a city.

I think generally, again, similar to the zoning principle, most people know what to expect from living in an urban center. I think it's expected that there will be a certain level of background noise and buzz about the urban center. It's really more the responsibility of designers and planners to ensure that good lighting design avoids unintended potential negative effects, but based on the fair expectations of a given area. I think Earth Hour personally is a great respectful gesture or time to collectively stop and reflect. Earth week, wow. That's a big one. Yeah, who knows. Could be societal change. It could really reframe our relationship with the night sky.

Who knows, who knows. There'd probably be unintended or unpredictable consequences or side effects of that, I imagine, if it were ever to happen.

Mariam Sobh [20:06] When you were mentioning some of the places where they had blackouts, there are countries where they have regular blackouts where they turn off the electricity for certain hours-

Gregory Francis [20:13] Yeah.

Mariam Sobh [20:13] In the day and the night, and people seem to adjust, so I just wonder sometimes if we're just really spoiled and privileged.

Gregory Francis [20:20] Yeah, absolutely. It's something... Especially yeah, in the UK and the US, we just expect constant access to electricity, WiFi, that sort of thing, and to have a consistent supply of those luxuries. But yes, we take it for granted. We are spoiled in some ways and maybe Earth hour reminds us of that, going without something for a period of time, certainly in my case anyway, makes me appreciate it all the more when it returns.

Mariam Sobh [20:45] Absolutely. And I wonder with regards to educating the public, is there more education needed to catch up with science for folks to understand the benefits to their health and their sleep when you have a dark night sky?

Gregory Francis [21:01] There's actually already an ever- growing body of research into these links between health and quality of sleep, including the significant contribution of light to organisms. And I say that purposely. It's not just humans here. Natural sleep, wake cycles, which is also to scientific term, circadian rhythms. The circadian rhythm is proven to have a significant effect on important areas of medical concern, such as mental health, diabetes, and obesity. And in a simple, non- medical way of explaining it, essentially the body's clock, the body clock, knowing when it's time to sleep, to switch off to regenerate. If the body's getting thrown out by the wrong type of lighting at the wrong time of day, it's not going to know when it has time to reboot itself properly. And policy design guys, legislation, are all starting to take this on board in varying degrees and a really good example of that, for example, we have seen the widespread introduction of what I call time responsive color shifting on mobile phone screens late in the evening because of this research about certain colors triggering negative responses into circadian rhythms. And these color shiftings on the phones try to lower the potential negative impact to our circadian rhythms. But the aim is to reduce and get your body ready for a good night's sleep.

Mariam Sobh [22:31] Greg, if we look ahead to the next decade or two, what does the future hold in store for light pollution in the night sky? We'll dig into that after we hear from Dr. John Barentine.

John Barentine [22:41] When it modernized its street lighting in the middle of the last decade, Tucson decreased its overall nighttime light emissions by up to 20%. Despite the changes here, we don't find any evidence that there was a negative impact on public safety or crime during overnight hours. Tucson is an example of how cities can grow and thrive while lowering energy consumption and costs to taxpayers, but without harming the night sky in the process. But as I am quick to point out, Tucson is very unusual in that regard. Most cities don't share its concern about the integrity of the night sky, and the past decade has seen cities all over the world growing brighter at an alarming rate. Averaged over all the countries of the world, light pollution appears to be growing at about double the rate of population growth.

Mariam Sobh [23:27] Greg, if we look ahead to the next decade or two, how do you see the built world evolving to become less of a burden on the night sky through light pollution?

Gregory Francis [23:37] In short, I think it's through the process of scientific research finding its way into our build and design guides, policies, and legislation. That's effectively how we're going to evolve. The academics progress their research, make it intelligible to us in the real estate community, and pressure gets put on the policies, design guidance, and legislation around these matters to make sure that we are adequately, effectively, responding to these findings.

Mariam Sobh [24:11] Well, I want to thank you so much, Greg. It's been a pleasure speaking with you. Thank you so much for taking the time.

Gregory Francis [24:14] No, likewise. Thank you for having me. It's been a real pleasure.

Mariam Sobh [24:17] Let's hear from John Barentine before we go back to London's Hampstead Heath.

John Barentine [24:22] The world didn't set out to have bad lighting and light pollution. We got there slowly without knowing what was happening, and we could change the situation in just the same way. But in order to do that, we have to choose a different outcome. I sense great cause for hope. More people than ever are becoming aware of light pollution, not only in how it causes harm to our world, but how easy the problem is to solve. When they make the choice to reduce light pollution, they'll see immediate results. It's the only environmental pollutant that leaves the scene at the speed of light, as soon as the pollution stops. In a world where we face big and serious problems that may take generations to fix, this one is a no brainer in comparison. And I am hopeful that solving this problem is a choice that many people will be willing to make.

Speaker 2 [25:12] We’re at a precipice point between modernization and the natural world. And I feel like we've started the ball rolling and have destroyed the natural world and will continue to destroy it. I think losing the stars is probably the first step in a long chain of destruction that is beginning.

Speaker 5 [25:27] The planet is, what? 4. 5 billion years old? And we've created this problem. If it's something that's important, and it is, light pollution affects ecosystems. iit affects a lot more than just looking up at the night sky – that's such a benign reason to want to change light pollution. We should be making more of an effort for the other creatures that live on this planet as well, that are affected by what we put out there.

Speaker 7 [25:55] I think detachment from nature is a part of the affliction of the modern age. Detachment from nature is one of the reasons we're all so depressed and anxious. So yeah, I don't know if we could ever really get away from that.

Mariam Sobh [26:12] As far away as the cosmos may seem, they do play an active role in our daily lives. Our addiction to artificial light may be the greatest and most misunderstood thing to ever happen to humankind. Yes, being able to read all night, watch that new series as soon as it drops, and navigate our way down an unfamiliar street are benefits, but at what cost? When it comes to lighting, nothing is free. Carbon emissions are a product of having electricity. The disruption to our natural sleep patterns is also at stake.

Meantime, wildlife, which has evolved for billions of years now, must alter their migratory patterns and natural rhythms to hue to the demands of our built world. The answer isn't as simple as turning off the light, going into caves, and remembering the good old days. For every Times Square, should there be a certified dark sky site where people can go to marvel at the brilliance of our entire natural world? Maybe I sound like a romantic, but marveling at the Milky Way or pondering what lies beyond that distant star could inspire the next generation of poets, thinkers, philosophers, and artists. And yet, if they can't see it, does it exist beyond a mere abstraction or an image online? Maybe it's time we turned off the lights for a bit and let our eyes adjust to the wonder of darkness. Who knows? We may see things clearly for the very first time.

I'm Mariam Sobh. This is Changing Places. Changing Places is brought to you by Avison Young. Our producer is Andrew Pemberton-Fowler. Our sound engineer is Patrick Emile. Our producer assistant is Hugh Perkic. Additional production support is provided by JAR Audio.

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