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posted by hubie on Monday January 23, @07:06PM   Printer-friendly
from the point-the-lights-down dept.

Observations from citizen scientists show the sky is getting about 10 percent brighter each year:

The night sky has been brightening faster than researchers realized, thanks to the use of artificial lights at night. A study of more than 50,000 observations of stars by citizen scientists reveals that the night sky grew about 10 percent brighter, on average, every year from 2011 to 2022.

In other words, a baby born in a region where roughly 250 stars were visible every night would see only 100 stars on their 18th birthday, researchers report in the Jan. 20 Science.

[...] "In a way, this is a call to action," says astronomer Connie Walker of the National Optical-Infrared Astronomy Research Laboratory in Tucson. "People should consider that this does have an impact on our lives. It's not just astronomy. It impacts our health. It impacts other animals who cannot speak for themselves."

Walker works with the Globe at Night campaign, which began in the mid-2000s as an outreach project to connect students in Arizona and Chile and now has thousands of participants worldwide. Contributors compare the stars they can see with maps of what stars would be visible at different levels of light pollution, and enter the results on an app.

"I'd been quite skeptical of Globe at Night" as a tool for precision research, admits physicist Christopher Kyba of the GFZ German Research Centre for Geosciences in Potsdam. But the power is in the sheer numbers: Kyba and colleagues analyzed 51,351 individual data points collected from 2011 to 2022.

"The individual data are not precise, but there's a whole lot of them," he says. "This Globe at Night project is not just a game; it's really useful data. And the more people participate, the more powerful it gets."

[...] The good news is that no major technological breakthroughs are needed to help fix the problem. Scientists and policy makers just need to convince people to change how they use light at night — easier said than done.

"People sometimes say light pollution is the easiest pollution to solve, because you just have to turn a switch and it goes away," Kyba says. "That's true. But it's ignoring the social problem — that this overall problem of light pollution is made by billions of individual decisions."

Some simple solutions include dimming or turning off lights overnight, especially floodlighting or lights in empty parking lots.

Kyba shared a story about a church in Slovenia that switched from four 400-watt floodlights to a single 58-watt LED, shining behind a cutout of the church to focus the light on its facade. The result was a 96 percent reduction in energy use and much less wasted light , Kyba reported in the International Journal of Sustainable Lighting in 2018. The church was still lit up, but the grass, trees and sky around it remained dark.

"If it was possible to replicate that story over and over again throughout our society, it would suggest you could really drastically reduce the light in the sky, still have a lit environment and have better vision and consume a lot less energy," he says. "This is kind of the dream."

Journal Reference:
Fabio Falchi and Salvador Bará, Light pollution is skyrocketing, Science, 379, 6629, 2023. (DOI: 10.1126/science.adf4952)


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  • (Score: 0) by Anonymous Coward on Wednesday January 25, @02:33AM (3 children)

    by Anonymous Coward on Wednesday January 25, @02:33AM (#1288471)

    They're saying that the data are noisy, but since there is so much of it, the errors average out.

    If you want to contribute in a more quantitative manner, you can take photographs of the sky or get a Sky Quality Meter and make measurements [darksky.org].

  • (Score: 1, Informative) by Anonymous Coward on Wednesday January 25, @04:21AM

    by Anonymous Coward on Wednesday January 25, @04:21AM (#1288486)

    Average grows SNR as sqrt, i.e. slowly. Your 12 hour exposure became 144 hours planned over multiple days.

  • (Score: 2) by driverless on Wednesday January 25, @09:32AM (1 child)

    by driverless (4770) on Wednesday January 25, @09:32AM (#1288510)

    Had a look at those (that is, the SQMs) a few years ago, they're crazy expensive for what you're getting. I already feed in data to various collectors for rainfall, wind, temperature, UV levels, PM10 levels, seismic activity, AIS, ADS-B, lightning strikes, rains of frogs, and zombies, and paying that much for a glorified light meter just seems excessive.

    • (Score: 0) by Anonymous Coward on Thursday January 26, @02:05PM

      by Anonymous Coward on Thursday January 26, @02:05PM (#1288698)

      I have a couple of them because of an old project at work. They are basically a calibrated photodiode that gives back the radiance of the sky when you press the button. The fancier model has a USB interface where you can set it logging and walk away. If you are smart with photodiodes (understanding how to bias them, etc.) it wouldn't be hard to do it yourself, but you'll want to make sure you know how to apply the calibration. I think they might give you the parts list and stuff to build your own. The important things that would go into it if they give you a calibration file would be to make sure you give it the proper supply and bias voltage, and use the exact same photodiode part. They worked out all the spectral relationships as well because the I love the units it gives you: stellar magnitude per square arc-second (which is a log scale). It would make for a fun hobby project to build your own, but if you want to skip all of those subtle details, it is easier to just buy one if all you want to do is measure the sky brightness in physical units.

      If you don't care what the physical units are and you just want to look at the sky brightness and how it changes for yourself, then you can quickly throw together a photodiode and data logger (after futzing with your bias/gain settings to get it optimized for night light levels and maybe adding a lens to make sure you are focusing on a patch of the sky and not getting light coming in from the side, etc.) and look at the output voltage of the photodiode.