With Light Pollution, Perseids Meteors Less Spectacular

The weekend meteor shower will not be fully visible in most parts of the U.S and Europe.

Take a look up in the sky tonight. Do you see the Milky Way?

If not, you're not alone.

It is estimated that two-thirds of Americans cannot see the Milky Way from where they live, says Scott Kardel, managing director of the International Dark-Sky Association (IDA.)

The IDA uses the Milky Way's visibility as a barometer of how much light pollution exists in the sky. Nearly all Americans and Europeans have some degree of light pollution where they live, with the worst offenders being large cities, where it's just about impossible to see anything other than the brightest stars. And in places like New York City or Shanghai, even those usually aren't visible. (Related: "Our Vanishing Night" from the November 2008 National Geographic magazine.)

So is there any hope for city-dwellers around the world who are looking to enjoy the upcoming annual Perseid meteor shower, which will peak from early Sunday morning to Tuesday morning, sending as many as 100 meteors per hour streaking across the night sky? (Related: "Opinion: Bright Lights. Big Problem.")

Kardel says it'll be tough.

"If you can get out of town, you should," he said. "And if you can't, look for dark open spaces. You're looking for shaded environments without bright lights near your eyes. But in the brighter cities, it's going to be challenging." (Use the IDA's Dark Sky Finder to help.)

Kardel spoke to National Geographic about light pollution, why he wants to regain the darkness, and tips for viewing the Perseids.

If I'm in a city, how does the sky look different, compared with a place where there's little to no light pollution?

Everything that you can see in the night sky in a city is magnified more than a thousand times over in a dark environment. This time of year, the summer Milky Way arches overhead in the early evening, and it is absolutely brilliant and detailed. But you're going to have trouble seeing it like that in a city. It's a hugely dramatic difference.

What about the Perseids? How would they look different if I were in one of the darkest spots in the United States instead of where I live, in Washington, D.C.?

For the meteor shower, when you have a darker sky, you'll be able to see different meteors. The big ones are visible everywhere. The fainter ones will only be visible from darker spots.

Where are the best spots in the U.S. to see the meteor shower?

You want to go someplace really dark. We're in the process of working with people around the world on what we call international dark sky places -- these are places that have been rated as having extraordinary nighttime skies. There are communities, parks, and reserves included.

Why is it important to make sure the sky is dark?

It's important to remember that a night sky was accessible to everyone through human history, and now that's gone. The night sky influenced art and science and religion for thousands of years—and it did something that we're now cutting ourselves off from. The night sky is a resource that belongs to all of us.

What does a community or park or reserve have to do to become a dark sky place?

For parks and reserves, they have to meet a certain threshold of darkness or minimum sky brightness. For communities, they also have to have lighting of the proper type in terms of making sure lights are fully shielded and downward pointing, instead of pointing up or putting glare in your face. They also have a plan to make sure it's going to stay that way and provide some kind of educational outreach.

I live in a major city that's not going to ever fully get rid of light pollution. Is there anything I can do to improve the quality of light in my city?

Anyone has control over lights of their own. It's important that lights are on only when they need to be on. You can have an off switch or a motion sensor. It's also important to know that you're only using the amount of light you need. And you should make sure that [outside] lights are pointed downward, not into someone else's yard.

What more could larger cities do?

There's the ability to use motion sensors for streetlights. We're now to the point where there are solid-state lights like LEDs that can be turned on and off so that after hours they can go down to 50 percent brightness or be turned off entirely. But if someone's walking down the path, the lights would come back up to full brightness. That offers tremendous potential for cities.

Santa Rosa, California, for example, removed one-third of their streetlights and then took another third and dimmed them in brightness. Their goal wasn't to restore the night sky but to cut down on greenhouse gas emissions. As a result, the sky is darker and they're saving hundreds of thousands a year.

What about safety?

More light makes people feel safer. That's been established. But whether more light actually makes people safer is a different question. In many places, it seems like adding light at night doesn't achieve the desired results.

Does light pollution affect animals or the ecology of an area?

It certainly affects nocturnal animals. Migratory birds fly at night, and there are tremendous problems when there are illuminated structures because they fly right into them. If buildings are not illuminated, those collisions actually go down.

There's also a problem with searchlights—bugs get caught in them and have a hard time breaking out. We've all seen moths and other insects drawn to light. That is a disruption to the ecosystem as well. Things that want to eat them are drawn to the light.

We've also noticed that because of light pollution, the birds that typically wake up before dawn and start singing in the sunrise start earlier, so they're getting less rest.

Switching gears a bit now: Does the color of the light make a difference in terms of damage to the night sky?

The color of the light does make a difference. Most of what we see when we see ordinary white light is a mixture of what we see in a rainbow. In a streetlight, there's a variety of different types. But an excess amount of blue is most damaging to night sky.

Blue scatters the most for the same reason the sun makes the sky blue in the daytime. It makes the sky proportionately brighter, and it also triggers our sense of glare. Blue is also what helps our internal clocks know what's day and what's night, so blue light—whether from a streetlight or a computer screen—can throw off circadian rhythms.

What about cell phones? I've been to outdoor nighttime events where it seems everyone has a cell phone out.

Cell phones have a high level of light pollution for you personally but low for the night sky. Unless, of course, you're out with friends and you've gotten used to the dark and then they turn on their cell phones. You would lose your dark adaptation. In terms of affecting our own circadian rhythms, light at night from a cell phone right in front of your face can certainly throw you out of whack.

One last question: What's the darkest place you've ever been?

I was a teenager camping with friends in the mountains in New Mexico, and I remember seeing so many stars that I couldn't tell what constellations were what. I was overwhelmed in a good way. There were more stars than I was used to seeing, and the familiar stuff was entirely lost.

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