Dr. James Lowenthal: Light pollution
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Eighty percent of Americans can’t see the Milky Way from their backyards due to light pollution caused by artificial lighting.
On March 18, 2025, SciLine interviewed: Dr. James Lowenthal, a professor of astronomy at Smith College. See the footage and transcript from the interview below, or select ‘Contents’ on the left to skip to specific questions.
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Introduction
[0:00:19]
JAMES LOWENTHAL: My name is James Lowenthal. I am Mary Elizabeth Moses professor of astronomy at Smith College in Northampton, Massachusetts. I study very distant galaxies in the early universe, and I also study exoplanets orbiting around stars in our own Milky Way. And I’m very active in helping to protect natural darkness at night for humans, for wildlife, for our quality of life, for being able to observe the sky, for our cultural connections to the sky.
Interview with SciLine
What is light pollution?
[0:00:57]
JAMES LOWENTHAL: Light pollution is artificial light at night that degrades the environment, that makes the sky artificially brighter, that shines into people’s windows, that blinds temporarily drivers and pedestrians and bicyclists on the street. It’s light that’s poorly designed. It’s light that’s excessive. It’s light that’s too blue. It’s light that’s on even when nobody’s using it. And light that maybe is, is there for some random, poor reason that’s not even a carefully thought out one.
How does light pollution affect people?
[0:01:44]
JAMES LOWENTHAL: Light pollution affects people negatively in several ways. First and foremost, their health. Light pollution is directly associated with serious health problems in humans, including elevated rates of some cancers like breast cancer and prostate cancer, as well as diabetes and obesity and sleep disruption and mood disorders in teens. It’s also a problem for humans because it causes light to shine in directions and in ways that are not only not helpful, but they can actually be dangerous, such as on our roadways, where it’s critical to be able to see well, and poorly designed lights do the opposite of helping you see well.
What is the impact of light pollution on wildlife?
[0:02:26]
JAMES LOWENTHAL: The impact of light pollution on wildlife is profound. There is practically no species studied that is not sensitive to light pollution in some way, and the vast majority of those are negative effects, deleterious, harmful effects. Practically every animal, every plant that you can imagine, that we know of, that we study, is hardwired to thrive in a world with bright daytime and dark nighttime, and when we disrupt that with light pollution at night, we disrupt entire ecosystems. There are species of fireflies that are threatened with extinction. In fact, most insects are very sensitive to light at night, and it is thought that light pollution is one of the major contributors to the insect apocalypse, the huge decline in insects we see. Birds migrate by the millions and millions every spring and fall in the United States—something like 80% of birds migrate, and something like 80% of those birds migrate at night, using the stars to navigate—at least it’s one of the ways. And in the presence of light pollution, their navigation systems are thrown off, and they circle over cities until they die from exhaustion, or they crash into brightly lit buildings, and when instead they should be flying unimpeded on their migration. It’s thought that up to a billion birds die every year due to light pollution in the United States alone. And it extends to fish in the ocean and our streams and rivers. It extends even to coral, and it extends to agricultural crops, which are shown to stay green too long in the presence of light pollution, and it actually results in lower yields, not higher yields. So, there’s no escaping that light pollution is bad for essentially all life on Earth.
What types of laws have been created to protect the night sky?
[0:04:45]
JAMES LOWENTHAL: Yeah, there’s a patchwork in the United States of laws protecting the night sky against light pollution, and they include from the very local, as local as homeowners’ associations, to cities and towns to states. There are roughly 17 states that currently regulate light pollution in some way or other statewide. And there are national efforts. There’s an international movement—the dark sky movement—with many, many thousands of people working on this internationally, worldwide, and there are some nations that actually do regulate light pollution. For example, Italy and France, and Germany and Chile, and the Czech Republic. The United States is currently not one of those. But there are efforts underway here, even in the United States, to bring national legislation to bear on light pollution.
What are some of the solutions to light pollution?
[0:05:21]
JAMES LOWENTHAL: The solutions to light pollution are the easiest of any major environmental problem. Air pollution and water pollution, climate change—those are all very difficult to deal with. In part because the pollution sticks around even after you cut off the source of the pollution. With light pollution, the problem goes away immediately. You just turn off the light switch. You flip the switch, the problem goes away immediately. It’s that easy. The hard part, of course, is that it’s a political and sociological and psychological issue at heart. We might say that the real cause of light pollution is fear of the dark, and maybe that’s hardwired into our DNA, just as our need for the dark is in our DNA, and that’s what makes it hard to deal with. Fortunately, there are great examples from all around the world of people getting together, changing their local culture, instead of fearing the dark, embracing the dark. And most of us in the dark sky advocacy world are not saying let’s get a get rid of all light at night. Let’s just use light responsibly at night. Let’s just be aware of the side effects and then make wise decisions. We can use light in our cities and towns, but let’s use it responsibly. Use only as much as you need. No more. Make sure that the light points down only, is carefully shielded against glare. Basically, the light should be in a can facing down, not out or up. Minimize blue light at night, because that’s the light that our eyes are looking for to trigger production—sorry, at night, our eyes look for the sun to go down, the blue light in the environment to drop dramatically, and that sends a signal to the brain to start producing melatonin, which resets our body clock, it’s a very important cancer-suppressing hormone, and it resets our 24-hour circadian rhythms. So, we should minimize the amount of blue light at night, which is kind of the opposite of what a lot of LEDs are doing these days. We should use controls most LED lights now, which is the majority of lights on the market are easily controlled with timers or dimmers, so that after hours—especially when nobody’s using the light—the lights dim or even turn off, and that’ll have multiple benefits. In addition to human health and protecting wildlife, it’ll save you energy. So these are some of the ways to fix lighting, starting on your own front porch but extending up to governmental controls as well.
Why should people care about the night sky?
[0:08:31]
JAMES LOWENTHAL: We should all care about the night sky because it belongs to all of us. It is part of our natural environment, and we have increasingly been cut off from it, and that’s to our detriment. There’s lots and lots written about how humans need nature, how they need it to thrive, how beneficial it is for our health, for our lower blood pressure, for peace of mind, to go for a walk in the woods. Going for a walk under the stars has the same effect. It provides a sense of awe, a sense of wonder. It helps ground us, ironically, because it’s the opposite of the ground in what it means to be human. Our stories, our histories, are literally written in the stars. There is no culture in human history that has not turned to the stars for its cosmology, its religion, its inspiration. It’s threaded inextricably through all parts of our culture. You can’t pick up a magazine or a book without reading about stars and seeing pictures of stars. And every flag has stars and moons, and we name our cars and our microwave ovens and our televisions after celestial objects and phenomena. Our days of the week—today is Tuesday, it’s named after the god Týr, who’s the god Mars. And in Italian, it’s martedì, literally Mars day. The seven days of the week all named after the planets and the sun and the moon. We just—there’s no place you can look in our culture that is not touched by astronomy and the stars, except modern life. Where we’re disconnected from it because of light pollution. The Milky Way is right over our heads every night. On a clear night, you should be able to see it, but 90% of Americans can’t see it from where they live, and that’s kind of like never seeing a rainbow in your life, or never seeing a tree, or never having seen the ocean. Our home includes the stars and the Milky Way, and everybody should be able to see it, and most people want to see it. People now make extensive plans to take vacations in places where they know the skies will be dark, the light pollution is low, and they can experience that sense of awe and wonder and joy of reconnecting with the night sky. And it’s something that’s right over our heads, if only we can fix light pollution in our own backyards.
