The northern lights (aurora borealis). The southern lights (aurora australis). Shooting stars. Dark Sky tourism is gaining popularity as light pollution has increased globally. People travel to dark places to experience the magic of the night sky. Gazing up at the Milky Way glowing across a dark sky is breathtaking.
Darkness is not inherently bad or dangerous. Darkness can be beautiful, restful, inspiring and healthy, an antidote to our overlit and overstimulating environments.
As Wendell Berry, a farmer, naturalist, and writer from rural Kentucky has said,
“In some situations, we may also miss out of realizing that we can navigate in the light of the stars and the moon, we just need to allow our eyes to adapt to the dark, pay more attention, and slow down.
If we instead go dark, we get to experience a whole different side of nature. We get to experience and know the night as it is, with its own life and animals and activities. And we may realize we don’t need to bring a light to function and navigate in the dark, we just need to adapt, pay attention, and slow down.”
Humans evolved in tight synchrony with natural rhythms, including the cycles of day and night. Natural light/dark cycles regulated many human behaviors, including acquiring and consuming food, reproduction, and sleep.
We have multiple internal “clocks” within our cells. These circadian rhythms (from the Latin “circa” meaning “around” and “dies” for “day”) run on cycles of roughly 24 hours. They regulate a variety of biological processes: hormone release (such as melatonin and growth hormone), metabolism, and body temperature. A “master clock” in our brains, the suprachiasmatic nucleus (SCN), acts to synchronize these various circadian rhythms.
The SCN responds to external cues, called “zeitgebers,” to help regulate our biological rhythms. The SCN is connected to our eyes, and the primary zeitgebers are light/dark signals. In the past, these signals correlated with the earth’s day/night cycles.
With the advent of artificial light and other more recent technologies (including our ubiquitous “screens”), our “nights” are no longer dark, and we are increasingly disconnected from the natural rhythms with which we evolved. Our SCN interprets blue light and bright lighting as “daytime,” and our circadian rhythms are thrown into disarray.
Messing with our circadian rhythm has important negative impacts on many aspects of our overall health and wellbeing.
Melatonin
At night, darkness stimulates the release of melatonin (the “vampire hormone”). Melatonin promotes sleep. It also acts as a potent natural antioxidant, removing free radicals, compounds which cause cell damage and are linked to cancer, heart disease and diabetes. Even 15 minutes of bright light/blue light can inhibit melatonin release. Chronic melatonin suppression is bad for our health! It can increase vulnerability to heart failure, metabolic disorders (diabetes type 2, obesity), mood instability and sleep disorders.
With this background, we can see how light pollution and artificial light at night (“ALAN”) might harm our health. While more research is needed, ALAN has been correlated with higher rates of cancer, including thyroid, breast, colon and prostate cancer. It may also make us more prone to depression and dementia.
Light pollution also harms wildlife by disturbing behaviors vital to their health and survival. For example, nocturnal animals evolved to depend on darkness for key activities such as avoiding predators, hunting and mating. And Monarch butterflies, whose population is precipitously declining for a variety of human-caused reasons (including pesticides, climate change, and loss of habitat), have a finely calibrated internal compass that allows them to follow an extraordinary migratory route. They migrate several thousand miles from the northern U.S. and Canada to Mexico and California for the winter and then return north in the spring; it may take 2-3 generations to complete the round trip. Their light-sensitive compass is thrown off by nighttime light, leading to disorientation and interfering with the migration that is crucial to their long-term survival.
Outdoor lighting
Our planet is growing ever brighter as light pollution increases each year. The explosive growth of data centers, with their extensive round-the-clock lighting, will only exacerbate this problem. A significant percentage of our outdoor lighting is unnecessary.
There are steps we can take to reduce light pollution while ensuring safety. In fact, some types of outdoor lighting make it more difficult to see in the dark. Too much glare can decrease visibility by blinding us and causing our pupils to constrict. And excessive light creates unintended shadows where people can hide. To quote the John C. Wells Planetarium at James Madison University, “dark sky does not mean dark ground.”
Improving the design of our most ubiquitous external light sources (such as streetlamps, home exterior lights and parking lot/business lighting) can improve visibility and safety while decreasing pollution. Some strategies include light shields which direct the light down (vs. up into the sky) and reduce glare, turning off lights when not needed, motion detectors and timers, and using softer lights.
Indoor lighting
Exposure to bright light indoors at night can also suppress our melatonin, disrupting our circadian rhythms and interfering with sleep. We want to aim for a strong contrast between night and daytime light exposure. At night, dim the lights and minimize screen time (screens emit blue light and keep us awake!). In the morning, seek out bright light, ideally sunlight; indoor lighting is less effective. A morning walk outdoors, even a short one, goes a long way in boosting mood, energy, and improving sleep quality!
Bottom line: we don’t need as much light as we think we do; our eyes have evolved to adjust to the dark gradually over a few minutes. And reducing excessive lighting and light pollution has a multitude of benefits.
A resource for more information: DarkSky International, darksky.org
