Zero Genie

This Valentine’s Day, head outside and find Orion. Then participate in Globe at Night’s effort to measure — and stop — light pollution.

The night sky with all its thousands of stars is our natural and cultural heritage just as much as any mountains, lakes, monuments, or museums. Yet artificial lights threaten to outshine the stars — in many areas, streetlights, stadium lights, porch lights, and even the lights within buildings all combine to create a sky glow bright enough to blot out all but the brightest stars. The problem is bad enough that 78% of Americans can’t see the Milky Way.

The Milky Way over Patagonia, Argentina
Federico Viegener / S&T Online Photo Gallery

Will the problem continue? The introduction of LED lights to our streets has complicated the matter. On the one hand, most LED lights being installed are “full cutoff,” meaning they don’t emit any of their light upwards. On the other hand, many LEDs are rich in blue light, which basically turns night into day. More pernicious still is that because LEDs are so cheap, towns are more likely to use more of them.

There are many things we can do, as individuals, to counter the threat light pollution poses to our heritage — more on that in a minute. But to enact general policies that will protect the night sky, we first need to convince the powers that be that there’s a problem. So the first step to countering light pollution is to measure it.

Citizen Scientists of the Night

Orion stands over Sirius in this image by Akira Fujii.

That’s where Globe at Night comes in. This citizen-science project has been ongoing for many years now, providing data on how bright the night sky is at various locations around the world.

“The project doesn’t require detailed knowledge about constellations or astronomy,” explains Constance Walker (NSF’s National Optical-Infrared Astronomy Research Laboratory). “As long as you can find Orion, you can take part!”

In Globe at Night’s campaign, members of the public can find the Orion constellation in the sky and then use Globe at Night’s web application to report how many stars they can see. This enables astronomers to estimate the limiting magnitude, or the faintest thing that would visible from that location.

With thousands such measurements taken every year, Globe at Night campaigns provide crucial information about the changing visibility of the night sky during a time when we need it the most — we can assess how much LED lights are affecting our skies and then, using that data, we can help enact policies that will make a difference.

How to Measure Your Sky

When: Head out once it’s fully night (at least an hour past sunset) and at a time when moonlight won’t interfere. Participate this Valentine’s Day, or take part any time during the Globe at Night’s  campaigns: February 14–23 and March 14–24.

Where: Anywhere! Just head out to your backyard and find the constellation of the month. Right now, you can use either Orion or Gemini for measurements.

How: You can print out constellation sky charts to take outside with you, or — even easier — use Globe at Night’s web app to compare the star charts to your sky. Just select the chart that most closely matches your view.

Finally, note your sky conditions — clear or cloudy? — and then click submit.

Protecting Our Night Sky

Globe at Night collects information on the night sky for professionals to use, to make assessments or predictions of light pollution trends. But it’s also insightful as an outreach tool. Share the web app with your neighbors. If you’re a teacher, take your class outside (or ask parents to take them outside) in the evening. If you’re a parent, grandparent, or aunt/uncle, do this activity with the children. Teach them to think critically about their night sky is like — and what it could be like if we take steps to protect it.

Just one example of a handsome full cutoff design for outdoor lighting, available at Home Depot.

Once the conversation is started, it becomes easier to share the best practices for outdoor lighting.

First, use light where you need it. Direct light downward, toward the path or stairs that need to be illuminated, rather than up at the sky. Several retailers, including Home Depot, Volt, and Eagle Mountain, offer beautiful dark-sky friendly options for lighting fixtures.

Second, use light when you need it. Use timers or motion sensors to shut off light when it’s not being used.

Finally, use bulbs that cast a warm, white light. If you’re considering LEDs, use amber LEDs for outdoor lighting.

Find more information at the International Dark-Sky Association’s website.