Why we can only track global changes in skyglow using citizen science. A tweetstorm by @skyglowberlin, submitted for publication on Twitter.— Christopher Kyba (@skyglowberlin) March 8, 2017
First: what is skyglow? It's the artificial brightening of the night sky, due to artificial light. (Image from: https://t.co/6Yb1dzj7gv) pic.twitter.com/Lgsd2YWbbr
— Christopher Kyba (@skyglowberlin) March 8, 2017
On clear nights the scatter is from aerosols (dust, smoke, haze) and molecules (N2, O2). So more haze often means more skyglow.
— Christopher Kyba (@skyglowberlin) March 8, 2017
Because of this, the cloudy night sky can be hundreds of times brighter than a starlit sky far from cities. https://t.co/zl7LIIh1yT
— Christopher Kyba (@skyglowberlin) March 8, 2017
Before we had artificial light, clouds made the sky darker, just like they do in daytime.
— Christopher Kyba (@skyglowberlin) March 8, 2017
The amount of light on an overcast night is astounding. In my smallish German town that's not brightly lit, I can read books by it.
— Christopher Kyba (@skyglowberlin) March 8, 2017
Predators can use the extra light to hunt, prey are way more exposed when trying to forage or mate.
— Christopher Kyba (@skyglowberlin) March 8, 2017
IF skyglow has an ecological effect it will be most dramatic on overcast nights. https://t.co/1kE5Or5JE8
— Christopher Kyba (@skyglowberlin) March 8, 2017
Why "IF"? We don't know?
For example, we know that there are all kinds of behavioral changes near lights. But do these result in ecological changes?
— Christopher Kyba (@skyglowberlin) March 8, 2017
Even that's hard, because you must track individuals over several years. Thankfully, there are some experiments now: https://t.co/GtrlryQ269
— Christopher Kyba (@skyglowberlin) March 8, 2017
We are currently performing the first-ever controlled experiment on ecological impact of skyglow: https://t.co/6U0K2yG3bc pic.twitter.com/oCJWEeedAb
— Christopher Kyba (@skyglowberlin) March 8, 2017
@skyglowberlin Incidentally, phys/eng @AndreasJechow designed and led the implementation of the system, you probably want to follow him.
— Christopher Kyba (@skyglowberlin) March 8, 2017
We've documented how a large fraction of the Earth's land surface is affected by skyglow on clear nights: https://t.co/Ta0Rqb4MeC
— Christopher Kyba (@skyglowberlin) March 8, 2017
So that's the end of the introduction. Now we come to how we measure skyglow.
— Christopher Kyba (@skyglowberlin) March 8, 2017
Pretty much everyone should be familiar with the famous satellite images of Earth at night. pic.twitter.com/l0Yasi7chg
— Christopher Kyba (@skyglowberlin) March 8, 2017
First: the satellite sees light heading up into space, not down to the ground. That's kind of an important difference...
— Christopher Kyba (@skyglowberlin) March 8, 2017
This is because the distance to the top of the atmosphere is way larger if you travel horizontally than if you head straight upward.
— Christopher Kyba (@skyglowberlin) March 8, 2017
This is huge, because a change in lamp design (for example to LED) can nearly completely eliminate horizontal light.
— Christopher Kyba (@skyglowberlin) March 8, 2017
But ONLY if you buy good LEDs & install correctly. There are plenty of crappy LEDs that still direct light upwards, and many are glaring. pic.twitter.com/vqt37z0msA
— Christopher Kyba (@skyglowberlin) March 8, 2017
The only satellite that observes night light globally (@NASANPP ) is COMPLETELY BLIND to blue light (<500 nm).
— Christopher Kyba (@skyglowberlin) March 8, 2017
That's a disaster for two reasons:
— Christopher Kyba (@skyglowberlin) March 8, 2017
1) "White" LEDs have a lot of blue
2) The clear sky scatters blue light the best (i.e. the sky is blue) pic.twitter.com/8yQH019Mu1
So we need to measure skyglow from the ground. Lots of scientists are doing this. The most common device is the "Sky Quality Meter" pic.twitter.com/irDoaag8UJ
— Christopher Kyba (@skyglowberlin) March 8, 2017
The SQM has spectral problems as well, particularly for LED switch as recently detailed by @pmisson et al.: https://t.co/0luP5fRQWV
— Christopher Kyba (@skyglowberlin) March 8, 2017
One problem is the color switch with LEDs, but let's leave that aside (eventually color stabilizes, and you can track changes again).
— Christopher Kyba (@skyglowberlin) March 8, 2017
Imagine if every single lamp in Berlin were changed (or turned off). I'd notice almost no difference in nearby Potsdam (~20 km distant)...
— Christopher Kyba (@skyglowberlin) March 8, 2017
So while records from professionally maintained stations are great, they only tell us about changes in a handful of places (say ~200).
— Christopher Kyba (@skyglowberlin) March 8, 2017
If we want to understand how skyglow is changing GLOBALLY, we need globally distributed observations. Here's where #citizenscience comes in.
— Christopher Kyba (@skyglowberlin) March 8, 2017
You don't need expensive instruments to take part, you just need eyes and an Internet connection to take part in @GLOBEatNight.
— Christopher Kyba (@skyglowberlin) March 8, 2017
.@GLOBEatNight works by getting people to say how many stars they can see, compared to several star charts. pic.twitter.com/st34VYvZzY
— Christopher Kyba (@skyglowberlin) March 8, 2017
Tens of thousands of people have taken part, but unfortunately participation is dropping right as we are switching globally to LEDs! pic.twitter.com/ffGe8dG2kP
— Christopher Kyba (@skyglowberlin) March 8, 2017
Each given individual @GLOBEatNight observation isn't very accurate. But the data are highly accurate in aggregate: https://t.co/g7ge6h9pAo pic.twitter.com/Knk2hRT2RD
— Christopher Kyba (@skyglowberlin) March 8, 2017
1) Make cities track #lightpollution as part of environmental monitoring.
— Christopher Kyba (@skyglowberlin) March 8, 2017
2) Massive global monitoring by citizen scientists.
It's also possible to improve accuracy of visual observations by using the Loss of the Night app, but only in cities https://t.co/kt14p5r0sf pic.twitter.com/QI0OjXP2Ap
— Christopher Kyba (@skyglowberlin) March 8, 2017
Thank you editors of Twitter for reading my submission. I hope it will be accepted for publication
— Christopher Kyba (@skyglowberlin) March 8, 2017
(RT #FirstTweet https://t.co/hnEcFSCJHg)
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