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What are the mysterious light sources on light pollution maps?

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Re: What are the mysterious light sources on light pollution maps?

#131

Post by hedora »

solstice wrote: post #76
nine_k wrote: post #69

Earlier quoted context omitted.

I wonder why don't they use mirrors to reflect the light back at night time. Metallized PETF film is strong enough, very lightweight, and not expensive, while reflecting, say, 95% of the light. Could save them a lot in electric bills.

Maybe it's to do with having to peel it back during the day? Should be quite an increase of mechanical complexity compared to just switching the lights on and off

Pulling a shroud over the roof at night is standard practice in passive greenhouses in China. It dramatically reduces heating costs. I’d guess it would reduce lighting costs as well.

Anyway, the necessary mechanical systems exist and are produced/deployed at scale.

Maybe US regulators should step in and require light / heat shielding at night above a certain size.

Re: What are the mysterious light sources on light pollution maps?

#132

Post by Moru »

divbzero wrote: post #111
batirch wrote: post #110

We drive 2.5 - 3 hours to Abu Dhabi deserts to watch milky way. It is nearly impossible to enjoy dark sky in Dubai.

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.

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

Re: What are the mysterious light sources on light pollution maps?

#133

Post by hedora »

zsellera wrote: post #95

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 (relativel…

In addition to wasting energy, light pollution at night is killing off insects, which (along with other factors, like neonicotinoids and habitat loss) is leading to ecosystem collapse.

For instance, North America’s bird population has dropped by 25% since 1970. Insects fared significantly worse over that period, but exact numbers are harder to come by.

Re: What are the mysterious light sources on light pollution maps?

#134

Post by mango7283 »

sandos wrote: post #100
mango7283 wrote: post #98

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

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...

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

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

Re: What are the mysterious light sources on light pollution maps?

#135

Post by maxerickson »

astura wrote: post #89
maxerickson wrote: post #67

Earlier quoted context omitted.

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

You can't use blackout curtains?

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

Re: What are the mysterious light sources on light pollution maps?

#136

Post by kjs3 »

dylan604 wrote: post #68
LargoLasskhyfv wrote: post #53

Earlier quoted context omitted.

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…

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 squar…

I would have changed the lights.

Re: What are the mysterious light sources on light pollution maps?

#137

Post by zoonosis »

pbhjpbhj wrote: post #117
f1refly wrote: post #107

Earlier quoted context omitted.

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.

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?

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

Re: What are the mysterious light sources on light pollution maps?

#138

Post by mrmuagi »

zsellera wrote: post #95

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 (relativel…

> 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?

Re: What are the mysterious light sources on light pollution maps?

#139

Post by pbhjpbhj »

zoonosis wrote: post #137
pbhjpbhj wrote: post #117

Earlier quoted context omitted.

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?

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

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

Re: What are the mysterious light sources on light pollution maps?

#140

Post by dylan604 »

kjs3 wrote: post #136
dylan604 wrote: post #68

Earlier quoted context omitted.

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 squar…

I would have changed the lights.

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.
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