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posted by hubie on Monday January 23 2023, @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: 2, Interesting) by BlueCoffee on Tuesday January 24 2023, @03:02PM (1 child)

    by BlueCoffee (18257) on Tuesday January 24 2023, @03:02PM (#1288369)

    Light pollution due to urban sprawl became a newsworthy issue in the 1980s, mostly through professional and amateur astronomers pressuring cities to do something about it.

    It was even starting to affect the Palomar observatory in California. Cities listened and across NA outdoor lighting was gradually switch to low presure sodium bulbs because they emit light in a very narrow spectrum and can easily be filtered out with a $50 astronomical filter.

    Unfortunately LEDs emit light across the visible spectrum and cannot be easily filtered. Narrow spectrum LEDs exist but for some reason most cities did not install them-maybe they didn't exist until very recently.

    LEDs, especially unshielded ones, set the world back 50 years in combatting light pollution. That's not progress!

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  • (Score: 0) by Anonymous Coward on Tuesday January 24 2023, @08:30PM

    by Anonymous Coward on Tuesday January 24 2023, @08:30PM (#1288418)

    Most of the street lighting is/was high pressure sodium bulbs, but it wasn't about light pollution but rather with the efficiencies of the bulbs. Light pollution is the result of the light fixture and the baffling (or lack thereof), and you get plenty of light pollution with high pressure sodium bulbs. There are low pressure sodium bulbs, and you can find those installed around observatories. The advantage there, as you allude to, is that they put out light in a very narrow wavelength band, almost monochromatic. High pressure sodium has additional spectral lines that pop up, and though they put out most of their light around a certain wavelength, the high pressure of the gas causes additional emission lines, so they aren't quite as yellow looking as the low pressure ones.

    The nice thing about the sodium bulbs is that they put out yellowish light, which is easy on the eyes at night. A lot of the replacement LED bulbs they are using are the "white" bulbs which can have a lot of light put out in the blue. Not only does that scatter easier than longer wavelengths, but it is hard on the eyes at night.

    An easy fix, and what would go a long way towards addressing light pollution would be to require dark-sky friendly light fixtures []. These are just lamp fixtures where the shade or baffle around it doesn't allow direct light to be sent above the horizontal, so think of a simple downward-pointing cone, you just need the entire bulb to be housed where it doesn't stick out under the cone shade. You'll see places want to have an "old timey" look and put in lamps that look like the old gas lamps where the entire bulb is exposed to the sky. All you're doing in that case is throwing almost all of your light upwards where it doesn't do you any good, so you have to keep adding more lamps until you get the brightness on the ground you desire. That is a lot of wasted light, meaning wasted electricity, meaning wasted money. If you want that old-timey Coach style lamp, get one with the bulb mounted in the top [] so that all the light shines down. The lamp outside our house was that coach style and the bulb would shine directly on our bedroom windows. I've replaced our outside lamps with dark-sky friendly ones, and it is wonderful. All the light shines down on the ground and not up on our windows.