Hey there, curious minds! Let’s dive into the fascinating world of the night sky and explore how light pollution affects our view of the stars.
For most of human history, nighttime meant it was time to rest. We used fire and some basic lights, but we weren’t really creatures of the night. That all changed with the invention of the light bulb. Imagine life without streetlights or lamps—it’s hard, right? But all this light has a downside.
On January 17, 1994, a big earthquake hit Los Angeles, causing a blackout. Suddenly, people could see the night sky clearly, and many were amazed by the sight of the Milky Way. It was so unusual that they called the Griffith Observatory to ask about it!
Today, over 80% of the world lives under skies that are too bright from artificial lights. In some places, like Singapore, it’s so bright that people’s eyes never fully adjust to the dark. This is called light pollution, and it hides the stars from us.
When it’s really dark, our eyes use something called scotopic vision. This is when rod cells in our eyes help us see in low light, but they can’t see colors. Because of all the artificial light, we rarely use this type of vision anymore.
Bill Wren, who works at the McDonald Observatory in Texas, is dedicated to keeping the skies dark for astronomy. He explains that places with naturally dark skies are disappearing, and we have to travel far from cities to see them.
An amateur astronomer named John Bortle created a scale to measure how bright the night sky is. In the darkest places (Bortle scale 1), you can see thousands of stars. But most people live in areas where they can see only a tiny fraction of these stars.
Seeing the Milky Way is awe-inspiring, but there are other reasons to protect dark skies. For astronomers, it’s crucial for research. Too much artificial light can also affect our health by disrupting our sleep and natural rhythms.
Light pollution is not just about losing the stars. It also wastes billions of dollars in electricity. Many lights are poorly designed and shine upwards, lighting the sky instead of the ground.
Some people worry that less light at night might make us less safe. However, studies show that more light doesn’t necessarily mean less crime. In fact, most crimes happen during the day or indoors.
Our bodies need darkness to produce melatonin, which helps us sleep and boosts our immune system. Too much light, especially blue light from screens, can disrupt this process. This is why it’s a good idea to reduce screen time at night or use apps that reduce blue light.
Light pollution affects animals too. For example, fireflies have trouble finding mates, and baby sea turtles can get confused and head towards roads instead of the sea. Even birds can be drawn to bright lights, disrupting their migrations.
The good news is that light pollution is the only type of pollution we can fix instantly. By simply turning off unnecessary lights, we can restore the night sky.
Experiencing a truly dark sky can make you feel connected to the universe. It’s a reminder of how vast and beautiful our world is.
Stay curious and keep exploring the wonders of the night sky!
If you’re interested in more space content, check out PBS’s “Summer of Space” series. A big thank you to McDonald Observatory for their efforts in preserving dark skies. They, along with the International Dark Sky Association, offer great resources on minimizing light pollution.
Grab a notebook and head outside on a clear night. Try to find a spot with minimal light pollution. Observe the night sky and write down what you see. Can you spot any constellations or planets? Note the differences in visibility compared to a night with more artificial light. This will help you understand the impact of light pollution on star visibility.
Conduct a simple experiment to see how light affects your ability to see in the dark. In a dark room, use a flashlight to simulate artificial light. Observe how your eyes adjust when the light is turned off. Discuss how this relates to scotopic vision and the challenges posed by light pollution.
Design a poster that highlights the importance of dark skies. Include facts about light pollution, its effects on wildlife and human health, and tips for reducing light pollution. Share your poster with classmates to raise awareness about preserving our night skies.
Create a model or a series of drawings that represent the different levels of the Bortle scale. Use materials like cardboard, paper, and markers to illustrate how the night sky looks at each level. This will help you visualize the impact of light pollution on star visibility.
Reach out to a local astronomer or visit an observatory to learn more about their work and the importance of dark skies for astronomical research. Prepare a list of questions about how light pollution affects their observations and what can be done to mitigate it. Share your findings with the class.
Here’s a sanitized version of the transcript:
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Hey smart people, Joe here.
For much of human history, nighttime signaled the end of our day. While we harnessed fire and some artificial light, we are not naturally creatures of the night. However, we can now experience the night like never before, thanks to the invention of the light bulb. Imagine modern life without artificial lighting—it’s hard to conceive. But all that light comes with a downside.
On January 17, 1994, a powerful earthquake struck the Los Angeles area, causing a massive blackout. Nearby Griffith Observatory received calls from residents asking about the strange sky they were seeing. What they saw was the Milky Way. Without artificial light, the night sky was so unfamiliar that they didn’t recognize it.
Today, over 80% of the world, and more than 99% of the U.S. and Europe, live under light-polluted skies. A third of humans on Earth can never see the Milky Way. In places like Singapore, light pollution is so severe that people’s eyes never fully adjust to the dark.
While researching light pollution, I learned a new term: scotopic vision. This is the type of vision we use in very low light levels. Our normal, bright-light vision is produced by color-sensitive cone cells, while scotopic vision is produced by rod cells, which are good at sensing brightness but cannot distinguish colors. Most of us don’t experience scotopic vision much because night has been taken over by artificial light.
So, what is real darkness? It’s challenging to describe the absence of something, but perhaps we should focus on what is hidden when light is absent.
I’m not a professional astrophotographer, but I’ve been fortunate to take pictures in some of the darkest places left in North America: Big Bend National Park, the Grand Canyon in Arizona, and McDonald Observatory in West Texas. While there, I met someone dedicated to preserving darkness.
I’m Bill Wren, special assistant to the superintendent at the University of Texas McDonald Observatory. My job is to keep the skies dark for ongoing astronomical research here. “The places where you can see a naturally starry sky are vanishing. You have to travel great distances from cities to see a naturally dark sky.”
An amateur astronomer named John Bortle developed a scale to measure night sky brightness based on visible celestial objects. In perfectly dark skies (Bortle scale 1), there are about four to five thousand stars visible to the naked eye. Most Americans live at Bortle scale 5 or higher, meaning they miss 98% of the stars.
We often see people at our public star parties who have never seen the Milky Way, and they are in awe. The beauty of the night sky is one reason to protect dark skies, but there are many others. For astronomy, it’s straightforward—we need to see the stars for research. Additionally, exposure to too much artificial light at night can negatively impact health and disrupt the biorhythms of all living creatures.
There’s also a cost-efficiency aspect; billions of dollars in electricity are wasted on poorly designed light fixtures that shine light into the night sky. “This is about dark skies, not dark ground… there’s no reason to waste light above the horizon.”
We’ve illuminated streets, parking lots, and buildings to make the night safer. When people hear we should use less light at night, their first reaction might be, “That’ll make us less safe!” However, no study has shown that more light leads to less crime. Most property crimes occur during the day, and even serious crimes are more likely to happen indoors.
Excessive light at night can also harm our health. For thousands of years, humans evolved with the rhythms of night and day. Our bodies produce melatonin in darkness, which helps us sleep and boosts our immune system. Light at night, especially blue light, can disrupt this process. LED lighting, while energy-efficient, often peaks in the blue spectrum, exacerbating the issue. Night work has even been classified as a risk factor for various cancers.
Consider reducing screen time at night, and if you must use a screen, switch to night mode or use apps that minimize blue light. Research increasingly suggests that we’ve underestimated the negative effects of light pollution on humans and wildlife.
Many species are adversely affected by light pollution, whether they are nocturnal or crepuscular. From fireflies unable to find mates to baby sea turtles heading toward roads instead of the sea, the consequences are significant. Each September 11th in lower Manhattan, 88 searchlights shine into the night sky as a “Tribute in Light.” Despite being a one-night event, over a million birds have been drawn to these lights, disrupting their migrations and leading to fatalities. Fortunately, scientists have collaborated with the Tribute in Light organizers to mitigate this issue.
Light pollution is unique because it’s the only type of pollution we can clean up instantly. Unlike polluted water and air, which take decades to recover, we can simply turn off the lights to restore the night sky.
Experiencing a naturally dark sky can evoke a sense of awe and perspective about our place in the universe. It’s a reminder of the vastness surrounding us and our connection to it.
Many of the stunning night sky shots in this video are time-lapses made with long-exposure photos. I wanted to give you a glimpse of what you can truly see with the naked eye under those rare dark skies. It’s hard to put into words, but it’s something you have to experience. It makes you feel both small and significant, distant yet connected. And ultimately, it’s good for you.
Stay curious.
If you want more space content, PBS is offering a “Summer of Space,” featuring new science and history shows streaming on PBS.org and the PBS Video app. Follow me over to “America From Scratch” for their episode on whether we should colonize Mars.
A big thank you to McDonald Observatory for allowing me to experience their dark skies. They, along with the International Dark Sky Association, provide excellent resources on minimizing wasted light while maximizing useful light without unintended effects on wildlife and plants. Links to these resources will be in the description.
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This version maintains the core message while removing any informal language or unnecessary details.
Night – The time between sunset and sunrise when the sky is dark and stars are visible – During the night, astronomers use telescopes to observe distant galaxies.
Sky – The expanse of air over the Earth where clouds, the sun, moon, and stars can be seen – On a clear night, the sky is filled with countless stars twinkling brightly.
Pollution – Harmful substances introduced into the environment, often affecting air and water quality – Light pollution from cities makes it difficult to see stars in the night sky.
Stars – Massive, luminous celestial bodies made of gas that emit light and heat – The stars in the Milky Way galaxy form beautiful patterns known as constellations.
Darkness – The absence of light, often occurring at night – In complete darkness, astronomers can better observe faint celestial objects.
Astronomy – The scientific study of celestial bodies like stars, planets, and galaxies – Astronomy helps us understand the universe and our place within it.
Wildlife – Animals and plants that live and grow in natural environments – Light pollution can disrupt the natural behaviors of nocturnal wildlife.
Light – Visible energy that makes things visible and allows us to see – The light from distant stars takes millions of years to reach Earth.
Health – The state of being free from illness or injury, often influenced by environmental factors – Reducing pollution is important for the health of both humans and the planet.
Vision – The ability to see, which can be affected by light conditions – Good vision is essential for astronomers when observing the night sky through telescopes.
