
What are the mysterious light sources on light pollution maps? - landfish
https://altairspace.com/2020/03/02/mysterious-light-sources/
======
amatecha
Ah yeah, in the post's first "unknown light pollution" example, I figured it
must be a greenhouse. I was driving through a relatively small town one time
and was a bit freaked out by this ominous yellow glow off in the distance.
Like, the whole sky was glowing [0]. I ended up driving out to try to find the
source, and discovered it was a huge greenhouse/farm. Luckily not an
extraterrestrial landing zone or so on ;)

[0] looked like this
[https://i.cbc.ca/1.4925044.1543460834!/fileImage/httpImage/i...](https://i.cbc.ca/1.4925044.1543460834!/fileImage/httpImage/image.JPG_gen/derivatives/original_1180/night-
sky.JPG)

~~~
yread
Yellow glow is understandable, but check out this purple one

[https://www.cbc.ca/news/canada/windsor/not-northern-
lights-g...](https://www.cbc.ca/news/canada/windsor/not-northern-lights-
greenhouse-glows-1.4924468)

~~~
LargoLasskhyfv
Photo caption says LED. That color is common for them, or even a mix of blue
and red. When going LED they only use ones with the wavelengths the plants
actually use. You also see this in articles covering vertical farming
prototypes. And when i think about it, this is nothing new, because i remember
people growing exotic plants in their windows in not so exotic germany, often
had 'plant-lights' with that purple sheen to support growth. That was decades
ago, done with flourescent tubes. Nowadays it looks like this:

[https://en.wikipedia.org/wiki/File:LED_panel_and_plants.jpg](https://en.wikipedia.org/wiki/File:LED_panel_and_plants.jpg)
[https://en.wikipedia.org/wiki/File:Led_grown_lights_useful.j...](https://en.wikipedia.org/wiki/File:Led_grown_lights_useful.jpg)

~~~
dylan604
I bought some of these dedicated wave length LED grow lights once winter. The
color is so off-putting that I built a grow tent around them. Event the cats
quit using that part of the house before I made the tent. However, the plants
sure loved them. I had a couple of potted citrus trees that started blossoming
after a couple of weeks inside under these lights. The house smelled amazing.
Wasn't worth the loss of square footage in the house though.

~~~
kjs3
I would have changed the lights.

~~~
dylan604
There you go again using logic. Besides, I had to at least let the lights work
long enough to see if they worked. In the end they did. They're just not
friendly for home living aesthetics.

------
twic
I flew through the night to Singapore once. I remember two very striking light
sources.

Firstly, oil well flares in the Middle East. The oil fields are in the middle
of nowhere, so they're these huge orange-red blooms set in utter darkness.

Secondly, Delhi. The city is brightly lit with streetlights. But there's a
suburb (?) to the south, Faridabad, that's as brightly lit, but with a
different, whiter, kind of lights. So you had these two huge blotches of
yellow and blue light projecting into each other. There are also some
extremely bright areas to the south of the city - after some investigation, I
decided they were probably rock-crushing plants.

~~~
3JPLW
Chicago has been slowly replacing its yellow sodium streetlamps with efficient
LEDs that project down instead of up. They've been working block-by-block in a
systematic way that you can see when you fly into the city at night. It's
quite dramatic.

~~~
maxerickson
My town replaced the sodium light across the street with a LED. A lot more
light comes in the windows now. It sucks.

~~~
astura
You can't use blackout curtains?

~~~
maxerickson
Not the point. The light is far enough away from the windows that there is
zero reason for it to shining on them.

------
zsellera
As someone working in the greenhouse lighting industry, I might have some
insight on this:

1\. there is an existing technology called energy screen/curtain, with the
primary function of retaining heat, but can also reduce light pollution by an
order of magnitude.

2\. light that escapes is essentially money lost, however it alone does not
justify the use of energy screens.

3\. as long as farmers have access to (relatively) cheap heat and electricity,
they won't invest into this technology.

4\. for the time being, it's a regulatory issue, just like water use (a single
plant use 2-2.5 l/day), supplemental co2 use and nitrate recirculation from
runoff water.

~~~
mrmuagi
> 4\. for the time being, it's a regulatory issue, just like water use (a
> single plant use 2-2.5 l/day)

Is the 'plant' there a, say, tree or is it referring to the whole building?

~~~
zsellera
that's per a single tomato plant, summer time. I guess it's the same for any
greenhouse crop, see the reasoning here:

water use is necessary to manage internal climate. the greenhouse was designed
to keep heat inside. the plants have to cool themselves (hence the
environment) by evaporation. the farmer manages evaporation rate by watering,
temperature and humidity. there are many feedback loops, both negative and
positive, balancing it is a non-trivial task.

btw. there's an average of 1.2-1.3 plant/m2 in most tomato greenhouses I've
seen.

~~~
mrmuagi
Ah, thanks for the clarification. I was shocked at how large a number it
seemed, but I only factored in how much water the plant itself displaces in
its structure, not the maintenance water to maintain humidity, temperature,
etc.

------
robbrown451
You'd think they'd do better at containing the light from the grow houses, so
more ends up on the plants and less making it to space. Like, foil or
something?

~~~
crazygringo
Since these are greenhouses they have to be clear to let the light in during
the day, I assume.

Anything that's going to reflect light to prevent it from leaving at night
will also block the sun from hitting the leaves during the day, unless it's a
complicated mechanical system that can be folded up during the daytime.

I'm guessing such a reliable mechnical system together with maintenance is
much more expensive than the light leakage.

~~~
coderintherye
There are systems on the market that are not too complicated. We have an iGrow
system for instance for our greenhouse.

But yes, the covers do tend to snag and such when rolling up and that can be
problematic and require maintenance. Definitely though the industry does not
seem to have yet embraced automation much.

~~~
Moru
Greenhouses are early adopters of automation. But they only automate the stuff
that actually works reliably. This means watering schedule, fertilizer and
light. There are few things mechanical that can go wrong with them, especially
the light part. They don't have a hord of maintenance people that have time to
fix everything that goes wrong. They might have one person that is doing that
beside other things.

I live close to one of the bigger ones in north Sweden. They run some
accelerated daytime schedule in the darkess of the polar winter so at least
part of the nights has a yellow sky in the whole area. You see it for 10 km on
the way to the village nighttime. Could almost believe it's a 100 k town but
no :-)

~~~
coderintherye
Yes, good to note my perspective is on greenhouses in the US, I think
greenhouses in Europe are definitely more automated, especially in Amsterdam!

------
rabuse
I was looking at light pollution maps just the other day, trying to find
places to do astro-photography, and was blown away by how much light pollution
there is. Really sucks, because I'd have to drive about 90 minutes out to get
into a dark zone.

~~~
donkeyd
Only 90 minutes? For me it's at least 3 hours to get to Class 4 on the Bortle
scale. Class 2 is probably more than 5 hours. Only alternative is the sea.

I'm planning to take a trip to a Class 1 this summer, it'll be hard to find a
place that dark that is reasonably reachable though.

~~~
krick
Exactly, this almost sounds like humblebragging (I know it's not, but
still...) I mean, in the whole EU you literally couldn't find a place with
Class 1 _at all_ , unless going far-far North into Finland national parks or
Norwegian mountains. Makes you hate civilization.

~~~
bjelkeman-again
According to Darksitefinder northern Sweden seems better. There are som great
places to go up there in the winter that is well worth trying.

~~~
Moru
Yes, every time we go visit my mother we stop on the road and look up, it's
beautiful. No villages for 15 km and only darkness around. And a car passing
by with ten headlights blinding you every now and then...

------
hermitcrab
On [https://www.lightpollutionmap.info/](https://www.lightpollutionmap.info/)
there is a big pollution area in Russia, North of Khazakstan. There doesn't
seem to be a city. Is this an oil field? One of the patches is at 67 degrees
42' N, 83 degree 47' E.

~~~
uhnuhnuhn
[https://en.wikipedia.org/wiki/Vankor_Field](https://en.wikipedia.org/wiki/Vankor_Field)

~~~
hermitcrab
Mystery solved. Thanks!

------
TallGuyShort
A lot of fracking sites near me have exceptionally bright lights at night when
they're being actively worked on. I suspect the brightness shown might be
regular old electric lights, not just gas flares.

~~~
dylan604
Car parks are notorious light polluters as well. These are large parking lots
where car manufacturers off load cars by rail for their "last mile" delivery
to the area dealerships. The lights are meant to keep the thief away. On top
of the horrendous light pollution, they also cause massive* traffic headaches
where the trains can come to a complete park for 20-30 minutes while the train
cars with autos are connected/disconnected.

*The one I lived near was in a pretty small town, so the traffic might have been only 10-15 cars on either side of the tracks. Massive is directly proportional to your direct involvement of being stuck.

~~~
pbhjpbhj
You mean loading cars on to trains? Surely they have sidings?

~~~
dylan604
I don't know how they remove the automobiles from the train cars. This isn't
what makes the train stop. It is the disconnect of the train cars with
automobiles from the train so they can be moved to another set of rails that
lead into the car park.

------
derefr
One thing I'd like to see is a light-pollution map of the US overlaid with a
map of all US federal land. To answer the question: what's the brightest thing
the federal government is doing?

~~~
reaperducer
I'm not sure that's a way to find the answer you're looking for.

I expect that a lot of the brightest spots on federal land will be mining
operations conducted by private companies.

------
donatj
Several years ago I noticed that the northern edge of Alaska was lit up like
Vegas on one of these light pollution maps.

I was very curious what the heck this was and took to Google Maps. Found that
it was oil fields as well. I'd personally assumed lighting for workers however
and not gas flares.

\-
[https://www.lightpollutionmap.info/#zoom=5&lat=10294175&lon=...](https://www.lightpollutionmap.info/#zoom=5&lat=10294175&lon=-16288830&layers=B0FFFFFTFFFFFFFF)

------
flashman
You absolutely can (or could) see the Kīlauea's glow from Mauna Kea,
especially if there were clouds for it to refract through, as you can see from
the first photo in this article:
[https://www.nytimes.com/2016/10/04/science/hawaii-thirty-
met...](https://www.nytimes.com/2016/10/04/science/hawaii-thirty-meter-
telescope-mauna-kea.html)

------
tzs
The map of the United States raises an interesting question. There is a pretty
distinct line down the middle, with nearly opposite light/dark patterns on
different sides of the line.

To the east, it is mostly bright areas with islands of dark. To the west, it
is mostly dark areas with islands of bright.

If you look at a regular map, nothing really stands out to explain the
difference. It is not like there is, say, a mountain range or difficult to
cross river or something running down the boundary that made travel or
settlement westward much more difficult at that point.

So why did patterns change there?

I asked about this once before, and received a few answers. I'm not sure if
any of them are the actual explanation or not, though [1].

[1]
[https://news.ycombinator.com/item?id=12345439](https://news.ycombinator.com/item?id=12345439)

~~~
duderific
My guess would be that the land is not as conducive to farming west of that
line, both in terms of soil and weather. So early settlements didn't occur
there, and thus cities did not emerge from those areas.

The cities that did evolve in the West were based on different resources:
ports around the ocean, mining, oil, railroad stops etc.

~~~
Wald76
That’s correct, the US population density correlates fairly closely with the
average annual rainfall:
[https://en.wikipedia.org/wiki/United_States_rainfall_climato...](https://en.wikipedia.org/wiki/United_States_rainfall_climatology#/media/File:Average_precipitation_in_the_lower_48_states_of_the_USA.png)

------
deathanatos
> _Kiluaea_ (sic?), _as an active volcano, regularly has literal glowing lava
> occupying the caldera._

Not anymore, sadly:
[https://www.nps.gov/havo/planyourvisit/lava2.htm](https://www.nps.gov/havo/planyourvisit/lava2.htm)

> _Beginning in May, 2018, the lava lake that existed inside Halema‘uma‘u
> crater disappeared and lava flows from Puʻu ʻŌʻō crater have ceased. There
> is no molten lava or lava glow to see anywhere in or out of the park._

(I would still recommend visiting: the road that encircles the volcano is
destroyed, and parts of it are hike-able, and the destruction is fun. And the
caldera is even bigger now, and the sulfur vents are interesting, and the
landscape is beautiful. And Hawaiʻi is just breathtaking.)

~~~
krick
I wonder if there are some other places in the world I could visit reasonably
expecting to see molten lava and all that dramatic looking stuff.

~~~
jamiek88
Iceland is your best bet.

~~~
ComputerGuru
The list of permanent lava lakes posted by and onychomys includes none in
Iceland.
[https://en.m.wikipedia.org/wiki/Lava_lake](https://en.m.wikipedia.org/wiki/Lava_lake)

------
divbzero
Fascinating article!

Constellations of fishing boats can also be a significant source of light when
viewed from space. Here are examples from NASA of fishing boats off the coasts
of Argentina [1] and Thailand [2].

[1]:
[https://earthobservatory.nasa.gov/features/Malvinas](https://earthobservatory.nasa.gov/features/Malvinas)

[2]: [https://earthobservatory.nasa.gov/images/92152/fishing-in-
gr...](https://earthobservatory.nasa.gov/images/92152/fishing-in-green-living-
in-yellow)

------
batirch
We drive 2.5 - 3 hours to Abu Dhabi deserts to watch milky way.

It is nearly impossible to enjoy dark sky in Dubai.

~~~
divbzero
I live on the other side of Earth but can fully sympathize with your long
drive. It’s a shame that the Milky Way is so difficult to see in most cities
around the world. It is truly majestic: not only visually stunning but also
awe-inspiring when you realize you’re gazing across the void at the next arm
of our galaxy.

~~~
Moru
And I complain about having to drive 20-30 minutes to get real darkness, puts
some perspective in there.

------
zhdc1
Light analysis is surprisingly noisy.If you want to do it right, you have to
screen out or control for cloud cover, reflections, moon light, oil well
fires, and also account for satellite position and the local time at night the
image was originally taken. The first four, particularly the first, are easier
said than done (e.g., still waiting for NASA to publicly release VNP46A2).

------
aasasd
> _At the time it wasn’t labeled on google maps_

That's exactly what OpenStreetMap is good for, at least where I am.

------
Raphmedia
Here in Canada, many tomato greenhouses have been converted to cannabis
greenhouses. Some areas have lost their night sky because of this, as they
have all grown quickly and use the same kinds of light arrays discussed in
this article.

------
perilunar
Since no one has mentioned them yet: a shout out to The International Dark-Sky
Association: [https://www.darksky.org](https://www.darksky.org)

------
dwd
It's a bit like this satellite image of Australia:

[https://eoimages.gsfc.nasa.gov/images/imagerecords/80000/800...](https://eoimages.gsfc.nasa.gov/images/imagerecords/80000/80030/australia_night_201204-10.jpg)

Some of what they have labelled as fires could be from mining but there is
literally nothing out there as far as human population.

------
deepsun
> with an enormous array of yellow lamps

Do they really need yellow? Plants do not really need green light (that's why
leaves usually reflect green they don't need), so they'd probably be ok with
red/blue lamps only. So why yellow?

[https://en.wikipedia.org/wiki/Grow_light](https://en.wikipedia.org/wiki/Grow_light)

~~~
detaro
I guess they use sodium-vapor lamps because they're common and quite
efficient, which happen to be yellow?

------
transect
My favorite mysterious light sources is a triplet off the coast of
Newfoundland:
[https://www.lightpollutionmap.info/#zoom=6&lat=5798060&lon=-...](https://www.lightpollutionmap.info/#zoom=6&lat=5798060&lon=-5275970&layers=B0FFFFFTFFFFFFFF)

I assume it's some sort of offshore rig.

------
macqm
I can't figure out one light pollution source in Poland in Sluchowo
(54.77550N, 17.94972E). The map from 2015 shows some factory of sorts, but it
disappears on the map from 2020, all you can see is an outline what it was. I
really wonder what kind of place this was and why it emitted relatively a lot
of light.

~~~
f1refly
Most likely some kind of military operation. It could be a storage site,
guarded 24/7 where light is important so the guards can see everything
clearly.

~~~
pbhjpbhj
Is this just tradition? Surely a computer system can see/hear, maybe using
night-vision (lidar? radar?), way better than guards can. Then lights can
activate and guards can shoot at anyone unwanted who crossed the perimeter ..
surely enough incentive?

~~~
zoonosis
I think that being well lit will help to deter intruders.

~~~
pbhjpbhj
How? Won't getting shot my soldiers be a deterrent?

~~~
zoonosis
How will they know if there are soldiers if they aren't lit?

------
eternalny1
I've been dealing with heatmaps on a personal pet project of mine:

[https://www.wingswatch.net/heat-map/2019](https://www.wingswatch.net/heat-
map/2019)

We are swimming in data these days, articles like this are fascinating.

------
ipqk
Darvaza Gas Crater:

[https://www.lightpollutionmap.info/#zoom=8.363333333333332&l...](https://www.lightpollutionmap.info/#zoom=8.363333333333332&lat=4902271&lon=6483116&layers=B0FFFFFTFFFFFFFF)

------
ncmncm
Used to be a huge bright spot _way_ the hell north in Canada, on one of the
islands. I finally IDed it as an enormous open-pit lead mine. The site was
finally mined out after producing millions of tons of lead.

------
mango7283
What are all the light sources in the ocean between Taiwan and South Korea?
I'd assume shipping, but what about the other shipping lanes, those don't look
so obvious compared to that piece of ocean

~~~
sandos
Squid fishing maybe?

"Fishing trials using LEDs (9 kW) and different numbers of MHs were carried
out in August and September 2009" from
[https://www.researchgate.net/publication/256998066_Catch_per...](https://www.researchgate.net/publication/256998066_Catch_performance_of_coastal_squid_jigging_boats_using_LED_panels_in_combination_with_metal_halide_lamps)

~~~
mango7283
Perhaps, that's a vast area for that though.. interesting.

( It's most obvious using the viirs 2019 overlay on lightpollutionmap.info )

------
gitgudnubs
Cool, it seems that US tomato farms produce as much light as North Korea.

------
AnimalMuppet
Some of it is burning off natural gas in oil-producing regions.

