International Dark Sky Week & Light Pollution

Updated: Apr 30


A couple of years ago, I got a smartwatch for Christmas from my dad. When I was looking at the display options, I had a fleeting thought about how silly it was to be able to display the moon phases. Sure, it’s kind of cool to see what moon stage we’re in, but other than that, what was the point? Is this like the whole “Mercury in retrograde” phenomenon? I was dubious, but I kept it on the watch face regardless since like I said, it seemed cool. Now that I’m regularly attending Sammy’s stargazing classes—my first one was in March, and we just finished the April class this past Wednesday—it’s taken on a whole new meaning for me.


If you’ve attended one of these classes or if you know something about stargazing, you probably know that a dark sky makes it easier to stargaze. When the Moon is in the new moon phase, stargazing is going to be better since that is when the night sky should be at its darkest (more on this below). And now—this is where my trusty wristwatch and its moon phase display come in—I easily know when the new moon is (hint: it’s right now for the month of April). Of course, a new moon comes around every month, so what makes this month’s new moon so special? Well, it’s International Dark Sky Week!

What is International Dark Sky Week?

The first International Dark Sky Week (IDSW, though then it was simply National Dark Sky Week) was held during April 2003’s new moon. Founded by then-high school student Jennifer Barlow, IDSW is an effort to get people all over the world to dim the lights and marvel at the universe that surrounds us. No, seriously, it’s not a metaphor. Turn your lights off and head outside to take a look at the stars. That doesn’t seem like too much work, so why did a week out of the year get dedicated to dark night skies?


Before we get too far into it, a quick recap for those of us that haven’t had 8th-grade science in a while: the new moon phase is when the Moon is between the Sun and the Earth, so the brightest side of the Moon is facing away from Earth. This makes the moon appear completely dark, so we get the darkest skies all month during this week-long period.


The problem is the sky isn’t nearly as dark as it used to be, even during the new moon. Since urbanization has really taken off, light pollution—the presence of anthropogenic and artificial light in the night environment—has too. According to the National Park Service and a 2003 study done by Cinzano & Elvidge, “North American light emissions show a roughly six percent annual increase from 1947 to 2000”. To put that into perspective, that’s a 318% increase over 53 years. That is an enormous change. And that’s not considering the 20 years that have passed since 2000, so you can imagine that this number is even higher at this point. And that’s only North America.


But is light pollution really more than a mildly annoying problem you have with your neighbor and their motion sensor-triggered security lights? Unfortunately, yes.


How light counts as a pollutant

Even though it’s seemingly harmless, especially when compared to toxic emissions or garbage in natural environments, excess light does indeed pollute our natural environments in several ways.

  • Artificial light competes with starlight in the night sky, therefore hindering astronomical observation. If I can’t see the Big Dipper when I’m taking out the trash at night, it’s a real bummer. For me, at least.

  • Artificial light disrupts ecosystems that have not evolved fast enough to adapt to it, causing negative ecological implications for tons of organisms, like mammals (even you and me), bacteria, and more. According to Franz Holker of the Leibniz-Institute of Freshwater Ecology and Inland Fisheries, artificial light “may reshape entire social ecological systems”—though a vague statement, I can tell you that this is not a good thing. Many animals (especially nocturnal ones) depend on light signals from their natural environment to tell them when it is safe to hunt or when it is time to change habitat.

  • Excess light results in over-illumination, which is also quite wasteful, as it is responsible for approximately two million barrels of oil per day in energy wasted in the United States. This is not only bad for the environment, but it’s not very nice to our wallets, either. That is oil and money that we are throwing away (or maybe setting alight… get it?).

  • Glare, or light aimed directly into your eyes, can be a public health hazard. Mario Motta of the Massachusetts Medical Society states that being partially blinded via glare can cause eye strain, which in turn may cause further damage. And have you ever had a headache caused by eye strain? Let me tell you, it is not a good time.


This is a complex topic, so there is a lot more to it, but you get the idea. Light pollution is pervasive in today’s society, and it’s not great for a variety of reasons. So, International Dark Sky Week was established and supported by organizations like the International Dark-Sky Association (IDA) in an effort to “temporarily reduce light pollution and raise awareness about its effects on the night sky, encourage the use of better lighting systems that direct light downward instead of into the sky, and promote the study of astronomy”. Dark sky advocates decided that it was necessary to dedicate this week in April to get ordinary folks like you and me to realize the issues that light pollution causes (and to check out the cosmos, which is super cool). That then begs the question...


What can you do about light pollution?

  • IDA provides some guidance on what sort of lighting is better for the environment, so you can look into what options might suit you and your budget.

  • You can become a citizen scientist and help IDA to measure light pollution in various parts of the country. Don’t knock it till you try it, either—data collection is a total blast, especially when you get to look at the stars!

  • You can also become an advocate for dark skies (yours truly just signed up the other day), become a member of IDA, or find a way to support IDA that works for you. They are doing some great work!


For as wild a ride as the COVID-19 pandemic has been, one perk is that it has helped reduce light pollution, at least in the UK. According to the BBC, “The annual star count [in the UK] shows a 10% drop in severe light pollution compared to 2020—meaning the UK saw the largest percentage of truly dark skies since 2013.” What’s more, Wales is spearheading the effort to decrease light pollution worldwide, having attained “exceptional dark sky conditions” in 68% of the country. I say we follow their lead.


As fans of good stargazing, it goes without saying that here at Friends of the Owyhee, we are adamant natural dark sky advocates. If you’d like to learn more about stargazing, you can sign up for our Introduction to Stargazing and Natural Night Skies class on May 19, or check out our YouTube channel for the classes from March and April. If you’d like to know more or just chat, feel free to give me a shout via email: katalinp@owyheefriends.org.

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