Our complicated love affair with light

One by one, synchronised according to time zone, cities began to turn themselves off. Named the World Wildlife Foundation’s “Earth Hour ambassador”, the astronaut’s role was to document the annual, voluntary blackout. As city lights blinked out, entire swathes of urban life seemed to disappear altogether. Kuipers live-tweeted the images along with his commentary. 

Earth Hour had begun in 2007 in Sydney – the city in which I grew up – as a 60-minute, global protest against carbon dependence. It was largely directed at the then Prime Minister, John Howard, and a culture of climate-change denial that was rampant in the Australian parliament.

Two years earlier I had marched around Sydney’s central business district with my parents, who wielded me like a placard at the Walk Against Warming. I was excited to have my picture in the local paper: I still treasure the clipping, in which my best friend and I are 11 years old and beaming, holding up a sign that says, “Howard is a Fossil Fool”. Beyond that, I didn’t really care about whatever was happening in the atmosphere. 

Earth Hour was a symbolic gesture and not meant to be interpreted literally: nobody was advocating for all lights to be turned off for good. But for me, now aged 13, the connection seemed quite direct. Wherever there was light there was power, and wherever there was power there was carbon dioxide.

This simple idea made the complexity of climate change easy to grasp: suddenly, carbon emissions were something I could see with my very own eyes. I imagined light seeping out of my house and up into the atmosphere. I pictured it settling into a bright, noxious fog.

While my understanding of the greenhouse effect left a lot to be desired, it turns out that I wasn’t exactly wrong about the bright, noxious fog. Research has confirmed that artificial light at night – known in the literature as ‘ALAN’ – has detrimental impacts on invertebrates and other creatures, including sea turtles and birds. Excessive exposure is also thought to have a plethora of adverse effects on human bodies and minds, from mood disorders to higher rates of some types of cancer.

Enthusiasm for Earth Hour reached its zenith around the time Kuipers photographed it from space and began to wane shortly afterwards. As attention turned to the systemic roots of climate change, the gesture of turning off the lights to “save the environment” began to feel somewhat quaint.

Earth Hour died a slow and quiet death, rolling on through the years with reduced participation and minimal press coverage. And yet the idea behind it – that excessive illumination is symbolic of some of the more toxic aspects of modernity – continues to resurface.

Light as life-giver

Light is, of course, essential for life as we know it. Without the sun, life on Earth wouldn’t exist. In a wide range of ways, across diverse periods and cultures, natural light has deep-rooted associations with both planetary and bodily health.

Science journalist Linda Geddes, for example, has charted the role sunlight played in healing across different cultures and time periods, including in Ancient Greek and Roman medicine and traditional Chinese medicine. In the 19th century, heliotherapy (the therapeutic use of sunlight) was widely used as a treatment for tuberculosis. In the 1920s, ultraviolet light was found to kill bacteria and lead to the synthesis of vitamin D.

As the academic Margaret Campbell points out, the idea that light and air are essential to healthy living originated in the context of sanatoria, before becoming a tenet of modernist architecture.

Artificial light’s status is less clear cut. Not understood as straightforwardly health-giving, it is bound up with our understandings of technology more widely as an ambivalent force. But how can light be essential and a pollutant? How do we tell good light from bad?

Bright new world

In 19th-century Europe, the introduction of street lighting was seen as a manifestation of post-Enlightenment values. The historian Wolfgang Schivelbusch has pointed to Paris – the City of Light – as the origin of many current norms around street lighting. There, the implementation of public lighting accompanied new regimes of surveillance and the invention of a modern police force.

Not everyone benefited from or responded with enthusiasm to the general brightening of cities in the 1800s. The arc light that was adopted mid-century – a forerunner of the electric bulb – was widely seen as less desirable than the softer, warmer illumination of the gas lamp that had preceded it. Shivelbusch cites, for example, an 1885 piece in the Gazette de France responding to an experiment with arc light:

Concerns about over-illumination and its effects, then, have been around for a while. But it wasn’t until the 1980s that artificial light began to be framed explicitly in terms of ‘pollution’.

This is partly because the idea of pollution as we understand it today – as something that intrudes on the natural environment – didn’t really come into effect until well into the 20th century, as the legal philosopher John Nagle has pointed out. Before then, a ‘pollutant’ referred largely to a cultural phenomenon, a social evil.

A key shift in the meaning of ‘pollution’ came with the publication of Rachel Carson’s book ‘Silent Spring’ in 1962. Carson investigated the harmful effects of pesticides on both non-human and human health, and her work is widely credited with igniting the environmental movements of the 1960s and 1970s. She highlighted the extent to which human health was inseparable from ecological health and drew attention to the costs of unimpeded industrialism and economic growth.

As the concept of environmental pollution expanded in usage, it began to encompass more and more forms of ‘intrusion’ into the natural environment – including sensory phenomena like light, noise and unpleasant odours.

In some cases, these “pollution claims” (as Nagle calls them) were evoked as part of an (often conservative) agenda to protest the expansion of urban environments into traditionally rural areas. In other cases, they were part of an effort to better understand how creatures with sensory worlds different from our own – such as insects and nocturnal mammals – might be impacted in previously unacknowledged ways by human activity.

A deluge of photons

When the first atomic bombs were dropped on the Japanese cities of Hiroshima and Nagasaki in 1945, the US government attempted to naturalise the devastation their nuclear weapons wrought by describing it as the “sun brought down to earth”. This metaphor had eerie resonances with survivor accounts of their world being inundated suddenly with a dazzling, unnatural light.

It is perhaps not coincidental that attitudes to artificial light began to change in the wake of these horrors. Visible light, after all, is a form of electromagnetic radiation, and radiation was now widely understood as something that could exert unknown changes within bodies and ecosystems.

As the Cold War progressed, many governments had an interest in how the body might fare in ‘timeless’, artificially lit environments, such as space capsules, submarines or bomb shelters. Michel Siffre, who performed some of the earliest experiments in caves on how humans respond to the absence of light, recalls that the Cold War was the reason he received “so much financial support”.

The impact of time on the body has played a role in non-Western medical traditions for millennia. In comparison, Western science lagged behind. The Cold Spring Harbour Symposia on Quantitative Biology met to discuss biological clocks in 1960, with the aim to bring together “leading investigators” and have a “unifying influence”. The meeting laid the groundwork for the contemporary scientific field of chronobiology: the study of how biological organisms respond to temporal factors.

Jürgen Aschoff, a scientist considered to be one of the founders of chronobiology, outlined an important discovery: the existence of endogenous circadian rhythms in humans, or a built-in body clock. The same mechanisms that existed in plants and smaller mammals also existed in humans.

Light plays a key role in these processes as a zeitgeber – a word that, translated literally from the German, means ‘time-giver’. In the absence of light, the human body clock tends to ‘freerun’ – to fall out of sync with the sun and the moon.

Tuning the body clock

Light is widely understood as the Earth’s own timekeeping mechanism: the sun’s rays pass over the spherical face of the earth, turning it into a giant clockface, and tuning all the tiny body clocks within its path to its rhythm. This idea has an almost divine sublimity to it; a sense of perfect, Gaia-like order.

Today, the idea of the circadian rhythm acts as a comforting reminder that humanity remains part of nature. A host of new technologies – like SAD lamps (to treat seasonal affective disorder) and filters that block blue light – have emerged in recent years, all of them promising to align the human body with the rhythms of the heavens.

The idea of a body responding to light is deeply organic. It recalls the process of photosynthesis in plants, which is probably the best-known example of chronobiology. Similarly, there is something almost viscerally troubling about the idea of this relationship going off-kilter.

Discussions of the changes that occur with excessive bright light tend to take on a gothic character. In an episode of ‘The Simpsons’ from 2003, Mayor Quimby’s decision to turn all the lights in Springfield to “perma-noon” results in a town gone haywire. Marge – unslept, her left eye twitching – starts ironing random objects. The birds fall out of the trees and begin tunnelling underground.

The role of light in regulating circadian rhythms is a key part of understanding the impacts of artificial light on both human and ecological health, but there’s a lot we do not know. Studies of the unconscious lives of human beings often emerge from the military ambition to reduce the need for sleep. Contemporary discussions around our relationship to light and sleep tend towards the idea of “hacking the body” in order to self-optimise.

Light impacts ecosystems in subtle and sometimes mysterious ways: it is not wholly understood, for example, why insects gravitate towards bright lights at night. Historically, the lives of nocturnal species have been grossly understudied compared to their diurnal counterparts.

The right kind of light

From the 1960s, then, there were discussions about light as a force that could harm both human and non-human bodies. The concept of “light pollution”, though, only really gained a popular foothold in the 1980s, when two astronomers – one amateur, one professional – teamed up to tackle ‘skyglow’, which is when light seeping up from urban areas obscures a view of the night sky.

The outcome of their meeting was the International Dark-Sky Association, or IDA – an organisation that would advocate for the reduction of light pollution worldwide and offer accreditation to “dark-sky areas” that met certain criteria.

In some contexts, and in some amounts, we need light to function. In others, we need darkness. Today, the dark-sky movement tends to promote the idea of balance as central to a healthy relationship to light. Their general guidance is to use only “the right light at the right place at the right time”. But as pollution scholars have noted, notions of what counts as ‘right’ (in substance, place, or in time) are very unstable, and tend to shift over time. We cannot take for granted a clear delineation between ‘necessary’ and ‘unnecessary’ light.

Discussions about reducing light pollution tend to focus on rural areas. The Campaign for Rural England, for example, has a programme called Night Blight, which researches the spread of light pollution across the British countryside as a consequence of urban sprawl.

In some ways, there are good reasons for this emphasis: rural areas in Britain tend to be havens for wildlife that are adversely affected by bright light at night. But it also has the effect of focusing attention on places that already enjoy darker nights, advancing the common narrative that urban areas, by contrast, are meant to be polluted.

In ‘The Country and the City’, the cultural theorist Raymond Williams draws attention to how the urban and the rural are locked into a mutually defined dichotomy: the rural is understood as an environment of physical and moral purity (a static landscape of rest), while the urban is understood as one of corruption (a bustling and necessarily polluted landscape of activity). The presence of bright light at night in the countryside is seen as ‘unnatural’. In the city, by contrast, it is seen as perfectly natural, coexisting with a plethora of other pollutants.

Light as a form of control

Like other forms of pollution, light pollution is distributed unevenly within urban areas, too, discriminating along lines of race and class. The authors of ‘Tackling Social Inequalities in Public Lighting’ note that working-class neighbourhoods tend to be more brightly lit than more affluent ones. While some places benefit from lighting designed to “emphasise heritage, identity and aesthetics”, social housing estates are “characterised by substantial over-illumination” in which lighting’s purpose is “order, safety and policing”.

The most common argument for brighter street lighting revolves around protecting people – especially women – from non-domestic sexual assault. But the evidence that light reduces crime and sexual violence is inconclusive. A 2022 paper revealed that a car parked under a streetlight is more likely to be stolen than one parked in the shadows. A meta-analysis from the same year showed that brighter street lighting decreased property crime but had no effect on incidences of violent crime.

The longest study to examine the impact of street lighting on incidences of sexual assault in particular – in residential and commercial areas in New Orleans in the late 1970s – found that brighter street lights resulted in no change over a 29-month period. Light’s relationship to safety remains murky and badly understood.

Still, areas that are deemed “high crime” tend to be more brightly lit. In 2014, the New York Police Department unleashed Project Omnipresence, using bright light to deter ‘anti-social’ behaviour. Here, over-illumination is a tool of intimidation, and is deployed – like other policing tactics – in ways that are often violent and discriminatory.

Given light’s intimate relationship with surveillance, this is especially true for those who inhabit a body that is deemed as suspect by racist institutions, as Canadian academic Simone Browne has detailed at length. At various points throughout history, darkness has functioned as a refuge for those seeking to escape the eyes of power.

Increasingly, smart streetlights containing inbuilt CCTV are being rolled out across cities. Most of these streetlights also have new remote dimming options, so they slip through under the guise of being the environmentally friendly option. What does it mean if the goal of abating light pollution suddenly corresponds with the agendas of police departments?

Inhabiting darkness

The proliferation of streetlights is in part driven by a deeply rooted nyctophobia – fear of the night – which, as the novelist Jun’ichirō Tanizaki famously noted, is endemic to the Western world in particular. As a child, I had an intense fear of the dark. It seemed to me that the room would come alive when the light went out; a familiar space was suddenly intensely unfamiliar and – I presumed – teeming with monsters.

I never really grew out of this fear. Once, I got lost on a hike and found myself in a forest after the sun had set. I spent the few hours before I found the road again in a state of extreme terror. In every tangle of branches I saw little signs the Blair Witch had left hanging there for me.

A key turning point for my nyctophobia came in 2017, when I found myself at a festival called Sanctuary Lab. It’s held deep in the Galloway Dark Skies Park in Scotland once every two years. As well as being literally dark, Sanctuary Lab is “electronically dark” – phone lights and torches are covered with little red stickers to soften their incisiveness, and any electricity is produced on-site, off-grid.

Deprived of the light I rely on to see, I stumbled around the forest. Occasionally something small and winged would land on my leg. I heard owls in the trees, little rustlings in the bushes. If I took the red sticker off my torch it would catch on the bright eyes of spiders in the grass. For those creatures, night was not just a refuge, it was their home. “Darkness is a habitat,” Bob Mizon, a prominent Dark Skies Campaigner, once told me. “It is a temporal habitat that sweeps each night across the globe.”

The following year, in London, I lived close to a particularly dark portion of the River Lea. Before my trip to Galloway, the towpath – along which I had to cycle on my way home from work at a river-barge restaurant – would have terrified me; I would have imagined only human presences lurking in the bushes, men who would jump out and spear-tackle me into the river or pull me into the darkness with them.

I still feared these men, but now I also thought of the wood mice and the red foxes, the pipistrelle bats with their squat little faces, and the moths they plucked from the air.

In ‘Purity and Danger’, the anthropologist Mary Douglas famously defined dirt as “matter out of place”. One person’s refuge is another person’s exposure; one creature’s pollution is another creature’s necessity.

The concept of light pollution doesn’t really bring us any closer to resolving the deeply complex ways in which light transforms space and time in different ways for different beings. But it might help us understand the way in which, as journalist Ed Yong writes, every animal – including the human animal – “is enclosed within its own sensory bubble, perceiving but a tiny sliver of an immense world”.