5 ms·

This is good; we've badly underestimated the cost of excess light pollution. Also good is using more LED street lamps that focus the light where we need it, ra

This is good; we've badly underestimated the cost of excess light pollution. Also good is using more LED street lamps that focus the light where we need it, rather than all over the place. Light pollution is bad, and street lights are very power hungry, with the old sodium lights consuming up to 0.25kWh per hour.

masswerk 6y ago
Actually, cold LED light is part of the problem. Better focusing only mitigates the problem they are posing.
- ashtonkem 6y ago
  We can and certainly should fiddle around with different LED colors, to balance our need for illumination against the risk of environmental harm.
- marviel 6y ago
  Can you explain what you mean about the risks of cold LED light? I'm unfamiliar with this problem
  - skrause 6y ago
    https://www.sciencemag.org/news/2014/10/leds-good-prizes-bad-insects https://www.sciencemag.org/news/2014/10/leds-good-prizes-bad...
  - masswerk 6y ago
    The basic light emitted by LEDs is generally quite cold (high color temperature). We can manufacture LEDs just in a few basic colors, where the blue ones are the most efficient. We haven't managed yet to produce something at scale like the light typically emitted by incandescent light bulbs. RGB light doesn't help here, since this is still emitting high temperature components, which are only mixed with lower energized ones. One way around this is using LEDs indirectly by energizing other light emitting materials, like phosphor, much like it is done in LED filaments, which, of course, comes at a cost. Simple filters don't help, since LEDs emit light only in a rather narrow spectrum (which is also, why they are more efficient compared to other light sources). The problem with cold light is that it is apparently attracting insects much more than broad spectrum incandescent light sources, even more than any potential breeding partners, which in turn affects mating.
    - LargoLasskhyfv 6y ago
      What cost? Looking back maybe 15 years all the experiments with CCFL and LEDs were more costly than the filaments i have now. They last longer, use less, AND make light which is pleasing and usable to me. Wheee! Almost candles! edit: Last longer as in have already outlasted anything I had before them, the filaments I mean. Also not really more expensive to buy. And their energy usage is ridiculously low.
      - masswerk 6y ago
        Cost as in efficiency. (Last time I looked, filaments were rated less efficient than direct light sources. However, they seem to become better.)
        LargoLasskhyfv 6y ago
        I'm using these [1] https://www.osram.com/ecat/PARATHOM%20Retrofit%20CLASSIC%20B-Professional%20LED%20lamps%20with%20filament-style%20LED%20technology-LED%20lamps-Lamps-Digital%20Systems/com/en/GPS01_1504753/PP_EUROPE_Europe_eCat/ https://www.osram.com/ecat/PARATHOM%20Retrofit%20CLASSIC%20B...
        BlueDingo 6y ago
        I'm not versed much in these filaments but from what I know, and your link, these are just phosphor-covered LEDs, right? What is it about your current bulbs or the filament design that makes you not classify them as LEDs? The power use looks the same and the listed CRI of >=80 doesn't inspire confidence.
        LargoLasskhyfv 6y ago
        I didn't say that, or did I? Anyways, indeed they are chains of tiny LEDs in series, and the substrate they are embedded in is treated somehow. As I understand it, that gives the embedded LEDs a "Nachleuchtzeit"/ after glow like in the CRTs of old TVs and computer screns, which can vary, as it did with that old screen stuff too. Then there is the spatial thing, as they are spread out in the filament, you can actually look at them without being "blinded". It's more like the light radiates from a volume, softer, not from one sharp point. Not that it would matter that much, who has naked bulbs? As a result of all that there is no https://en.wikipedia.org/wiki/Beat_(acoustics) https://en.wikipedia.org/wiki/Beat_(acoustics), no perceivable flickering at my power frequency of 50Hz. I think I'm sensitive to that, because the line/destination signs on public transportion do flicker for me when I and they both stand, not only when in motion. Ah yes, the CRI. What can I say? I now have them everywhere, except the cellar. I prefer warm white, which they are. I can't see 'wrong' colors with them. Crosschecked that with a cassette of about 40 Faber-Castell color pencils right now, during my local morning twilight. Full spectrum. Because "retro-fit" they fit in my old sockets. They just hit a sweet spot for me. I dim, or 'tune' them by using one to three circuits, the switches and my rooms are wired to allow for that. Old, but not obsolete ;-)
  - ip26 6y ago
    Cold means high blue content. Blue light is the one that most disrupts insects, nocturnal animals, your night vision, your own sleep cycle, and contributes the most to obscuring the stars.
    - Florin_Andrei 6y ago
      > and contributes the most to obscuring the stars That part is not actually true. Any light will obscure the stars; if you want to compare different colors, it's the middle of the spectrum that contributes most, but the difference is small. As an amateur astronomer, the LED lights are a big problem because their light pollution is hard to filter out. Sodium is easy, it's nearly monochromatic, so a simple filter will remove most of it. Mercury is not super-hard, the spectrum is not very broad and it's pretty uneven. But LEDs have a broad, even spectrum, which is impossible to filter out.
      - ip26 6y ago
        Take it up with IDA, I guess. My understanding is blue light scatters more in the atmosphere. https://www.darksky.org/why-is-blue-light-at-night-bad/ https://www.darksky.org/why-is-blue-light-at-night-bad/
tyho 6y ago
250W...
- ashtonkem 6y ago
  Which over an hour is 0.25kWh.
  - formerly_proven 6y ago
    Sodium lamps are actually pretty efficient at around 125 lm/W, SOX lamps do over 200 lm/W.
  - jtwaleson 6y ago
    Yes, but it's like saying: the distance he walked is 5km per hour for one hour. Easier to just say 5km.
bredren 6y ago
I think the impact of light and sound pollution is vastly underestimated. Sound and light pollution not only causes hidden environmental issues but also does damage to human health. Suffering sound and light pollution is a hidden additional burden placed on lower economic status people. Poor people experience health inequities due to increased exposure to light and sound, but more pressingly air pollution. [0] The status of enjoying quiet is even clear in the middle class. You can even see the emerging divide on transit in who has noise cancelling headphones and who does not. [0] https://ec.europa.eu/environment/integration/research/newsalert/pdf/air_noise_pollution_socioeconomic_status_links_IR13_en.pdf https://ec.europa.eu/environment/integration/research/newsal...
rokweom 6y ago
Sodium lamps are very efficient. Saying that they consume up to 250W doesn't mean anything. There are LED lamps that consume much more.
kibwen 6y ago
Here's a quite good video about the pros and cons of LED vs high/low-pressure sodium street lamps: https://youtube.com/watch?v=wIC-iGDTU40 https://youtube.com/watch?v=wIC-iGDTU40 . It goes into lamp efficiency, how our eyes see differently at night, response time under different sorts of light, color temperature, circadian rhythm disruption, and light pollution.
- teslabox 6y ago
  It's a good video, but it's also a case study in being 'almost right'. The almost-correct interpretations cascade and result in a faulty conclusion: that blue-white LED streetlights are better than orange-white streetlights. Various comments object to the faulty conclusion ([1], for example). At the end he at least addresses his ignorance: > [18:39] You may have noticed that I didn't talk about the blue light from LEDs, and how this is supposedly ruining our eyes. That's because the "science" behind this is questionable, at best. > [18:55] [discussion of chart with percentage blue light of various light sources] > [19:04] [...] but considering that our eyes can withstand the intensity of sunlight, which is far far greater than any normal artificial light source, and also has a lot of blue light, and ultraviolet, which definitely is harmful, I think the 'blue light' thing is just fear-mongering. If someone can point to some verified, peer-reviewed research supporting this, and not a dodgy website, I'll consider changing my stance. In any case, the high flexibility of LED technology means it can be tuned in pretty much any way we like. The research on the harm of blue light is out there -- For example, one of the comments links to "Effects of blue light on the circadian system and eye physiology" [0]. (only partially read at this point - I don't know if this paper gets into the mechanism of damage done by blue light, as I understand it...) The sun hangs high in the sky and casts light on everything. We never need to look at the sun directly, we use the sun's light indirectly, after it bounces off of things. The atmosphere scatters the sun's blue light before it gets to us [2]. Artificial lights hanging on poles emitting photons we can't avoid having beamed directly into our eyes... Blue photons have relatively higher energy levels, and different physiological effects, than orange photons... [note to self: expand on this.] The preceding video was about High Pressure Sodium lights, which I thought was good too: https://www.youtube.com/watch?v=U1dMlVwUsrA https://www.youtube.com/watch?v=U1dMlVwUsrA My transcription of the video's faulty conclusion (italics added): > To conclude: although the High Pressure Sodium light is very efficient, its primary output color is misaligned with our nighttime visibility. Only about 1/4 of its light is actually effective at stimulating the cells in our eyes. Although the cool color temperatures of many LED replacements is harsh and aesthetically displeasing, studies have shown that it is not only more efficient, but also makes driving at night safer. There is, however, the potential for greater circadian rhythm disruption and larger amounts of skyglow, using these bluer light sources. > Still, it seems clear that the High Pressure Sodium is on its way out. Advancements in LED technology are happening at a breakneck pace. Just 10 years ago, they weren't seen as viable, but today even the least efficient of LED replacements ends up emitting the efficiency of High Pressure Sodium once scotopic light output is considered. > As it stands in 2018, we are faced with the choice of efficiency over aesthetics. I'm pretty sure I'd enjoy roadways lit with relatively-warm 3000K LEDS, and these also wouldn't disrupt sleep much. But you can save a lot more energy, and potentially have safer roadways, with 5700K lighting. > Either way, it seems clear that LED technology will very soon overtake the tried-and-true High Pressure Sodium lamp, just as the High Pressure Sodium itself replaced the mercury-vapor lamp. And in 40 or 50 years, who knows what technology might light our roadways. [0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734149/pdf/mv-v22-61.pdf https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734149/pdf/mv-... - "The radically different power spectrums can look similar when viewed directly by the eye, irrespective of how much blue emission is present." [1] https://www.youtube.com/watch?v=wIC-iGDTU40&lc=Ugx6MYdsMY6I_G2rbU94AaABAg https://www.youtube.com/watch?v=wIC-iGDTU40&lc=Ugx6MYdsMY6I_... [2] https://en.wikipedia.org/wiki/Rayleigh_scattering#Cause_of_the_blue_color_of_the_sky https://en.wikipedia.org/wiki/Rayleigh_scattering#Cause_of_t... edit: this page has a discussion of drop-sag lights vs. proper fully-shielded lights: http://www.skykeepers.org/good-bad-lights-cv.html http://www.skykeepers.org/good-bad-lights-cv.html
efa 6y ago
North Korea must be swimming in insects. https://i.imgur.com/S1mrMKN.jpg https://i.imgur.com/S1mrMKN.jpg
- DocTomoe 6y ago
  They also use pesticides pretty liberally. But there is a somewhat interesting paper on North Korean entomology: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3554493/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3554493/
emptybits 6y ago
> Also good is using more LED street lamps that focus the light where we need it, Focusing light where needed is good. Using LEDs, as we do now, has downsides though. LED lighting in cities is making astronomy and astrophotography and even animal life worse in some cases.[1] Traditional sodium vapour lights pollute around a wavelength of 589 nm.[2] That's the yellow/orange sky you used to see in the sky around cities. In theory, if you filtered out that wavelength 10 years ago, you'd be able to eliminate a lot of light pollution. But today, with more LED lighting, the pollution tends toward white/blue. This is "nicer" in some objective and subjective ways. e.g. colour accuracy. But it's a bitch to filter out, without also removing all the white and broad spectrum we want to see in the features of the night sky. Animals are also sensitive to white and blue light emitted by modern LEDs, and the NatGeo link and others go into why this can be a bad thing, compared to "old fashioned" lighting methods, inefficient as they are. [1] https://www.nationalgeographic.com/news/2017/11/light-pollution-energy-LED-bulbs-spd/ https://www.nationalgeographic.com/news/2017/11/light-pollut... [2] https://www.peterzelinka.com/blog/2019/8/light-pollution-filters-for-astrophotography https://www.peterzelinka.com/blog/2019/8/light-pollution-fil...
- mrpopo 6y ago
  We made LED lighting white because we wanted it. We can make yellow LED lighting as well. This should be suggested to city councils, if changing the wavelength would be beneficial to insects with no downsides.
  - TACIXAT 6y ago
    I'd be so stoked for red street lights. They don't mess up your vision at night.
    - emptybits 6y ago
      Indeed. Nor does red light mess as much with animal (incl. human) physiology and behaviour and waking cued by white/blue/daylight. Potential small (safety?) downside: red light illumination does greatly reduce colour discrimination at night versus white light.

masswerk 6y ago

Actually, cold LED light is part of the problem. Better focusing only mitigates the problem they are posing.

ashtonkem 6y ago
We can and certainly should fiddle around with different LED colors, to balance our need for illumination against the risk of environmental harm.
marviel 6y ago
Can you explain what you mean about the risks of cold LED light? I'm unfamiliar with this problem
- skrause 6y ago
  https://www.sciencemag.org/news/2014/10/leds-good-prizes-bad-insects https://www.sciencemag.org/news/2014/10/leds-good-prizes-bad...
- masswerk 6y ago
  The basic light emitted by LEDs is generally quite cold (high color temperature). We can manufacture LEDs just in a few basic colors, where the blue ones are the most efficient. We haven't managed yet to produce something at scale like the light typically emitted by incandescent light bulbs. RGB light doesn't help here, since this is still emitting high temperature components, which are only mixed with lower energized ones. One way around this is using LEDs indirectly by energizing other light emitting materials, like phosphor, much like it is done in LED filaments, which, of course, comes at a cost. Simple filters don't help, since LEDs emit light only in a rather narrow spectrum (which is also, why they are more efficient compared to other light sources). The problem with cold light is that it is apparently attracting insects much more than broad spectrum incandescent light sources, even more than any potential breeding partners, which in turn affects mating.
  - LargoLasskhyfv 6y ago
    What cost? Looking back maybe 15 years all the experiments with CCFL and LEDs were more costly than the filaments i have now. They last longer, use less, AND make light which is pleasing and usable to me. Wheee! Almost candles! edit: Last longer as in have already outlasted anything I had before them, the filaments I mean. Also not really more expensive to buy. And their energy usage is ridiculously low.
    - masswerk 6y ago
      Cost as in efficiency. (Last time I looked, filaments were rated less efficient than direct light sources. However, they seem to become better.)
      - LargoLasskhyfv 6y ago
        I'm using these [1] https://www.osram.com/ecat/PARATHOM%20Retrofit%20CLASSIC%20B-Professional%20LED%20lamps%20with%20filament-style%20LED%20technology-LED%20lamps-Lamps-Digital%20Systems/com/en/GPS01_1504753/PP_EUROPE_Europe_eCat/ https://www.osram.com/ecat/PARATHOM%20Retrofit%20CLASSIC%20B...
        BlueDingo 6y ago
        I'm not versed much in these filaments but from what I know, and your link, these are just phosphor-covered LEDs, right? What is it about your current bulbs or the filament design that makes you not classify them as LEDs? The power use looks the same and the listed CRI of >=80 doesn't inspire confidence.
        LargoLasskhyfv 6y ago
        I didn't say that, or did I? Anyways, indeed they are chains of tiny LEDs in series, and the substrate they are embedded in is treated somehow. As I understand it, that gives the embedded LEDs a "Nachleuchtzeit"/ after glow like in the CRTs of old TVs and computer screns, which can vary, as it did with that old screen stuff too. Then there is the spatial thing, as they are spread out in the filament, you can actually look at them without being "blinded". It's more like the light radiates from a volume, softer, not from one sharp point. Not that it would matter that much, who has naked bulbs? As a result of all that there is no https://en.wikipedia.org/wiki/Beat_(acoustics) https://en.wikipedia.org/wiki/Beat_(acoustics), no perceivable flickering at my power frequency of 50Hz. I think I'm sensitive to that, because the line/destination signs on public transportion do flicker for me when I and they both stand, not only when in motion. Ah yes, the CRI. What can I say? I now have them everywhere, except the cellar. I prefer warm white, which they are. I can't see 'wrong' colors with them. Crosschecked that with a cassette of about 40 Faber-Castell color pencils right now, during my local morning twilight. Full spectrum. Because "retro-fit" they fit in my old sockets. They just hit a sweet spot for me. I dim, or 'tune' them by using one to three circuits, the switches and my rooms are wired to allow for that. Old, but not obsolete ;-)
- ip26 6y ago
  Cold means high blue content. Blue light is the one that most disrupts insects, nocturnal animals, your night vision, your own sleep cycle, and contributes the most to obscuring the stars.
  - Florin_Andrei 6y ago
    > and contributes the most to obscuring the stars That part is not actually true. Any light will obscure the stars; if you want to compare different colors, it's the middle of the spectrum that contributes most, but the difference is small. As an amateur astronomer, the LED lights are a big problem because their light pollution is hard to filter out. Sodium is easy, it's nearly monochromatic, so a simple filter will remove most of it. Mercury is not super-hard, the spectrum is not very broad and it's pretty uneven. But LEDs have a broad, even spectrum, which is impossible to filter out.
    - ip26 6y ago
      Take it up with IDA, I guess. My understanding is blue light scatters more in the atmosphere. https://www.darksky.org/why-is-blue-light-at-night-bad/ https://www.darksky.org/why-is-blue-light-at-night-bad/

tyho 6y ago

250W...

ashtonkem 6y ago
Which over an hour is 0.25kWh.
- formerly_proven 6y ago
  Sodium lamps are actually pretty efficient at around 125 lm/W, SOX lamps do over 200 lm/W.
- jtwaleson 6y ago
  Yes, but it's like saying: the distance he walked is 5km per hour for one hour. Easier to just say 5km.

bredren 6y ago

I think the impact of light and sound pollution is vastly underestimated. Sound and light pollution not only causes hidden environmental issues but also does damage to human health. Suffering sound and light pollution is a hidden additional burden placed on lower economic status people. Poor people experience health inequities due to increased exposure to light and sound, but more pressingly air pollution. [0] The status of enjoying quiet is even clear in the middle class. You can even see the emerging divide on transit in who has noise cancelling headphones and who does not. [0] https://ec.europa.eu/environment/integration/research/newsalert/pdf/air_noise_pollution_socioeconomic_status_links_IR13_en.pdf https://ec.europa.eu/environment/integration/research/newsal...

rokweom 6y ago

Sodium lamps are very efficient. Saying that they consume up to 250W doesn't mean anything. There are LED lamps that consume much more.

kibwen 6y ago

Here's a quite good video about the pros and cons of LED vs high/low-pressure sodium street lamps: https://youtube.com/watch?v=wIC-iGDTU40 https://youtube.com/watch?v=wIC-iGDTU40 . It goes into lamp efficiency, how our eyes see differently at night, response time under different sorts of light, color temperature, circadian rhythm disruption, and light pollution.

teslabox 6y ago
It's a good video, but it's also a case study in being 'almost right'. The almost-correct interpretations cascade and result in a faulty conclusion: that blue-white LED streetlights are better than orange-white streetlights. Various comments object to the faulty conclusion ([1], for example). At the end he at least addresses his ignorance: > [18:39] You may have noticed that I didn't talk about the blue light from LEDs, and how this is supposedly ruining our eyes. That's because the "science" behind this is questionable, at best. > [18:55] [discussion of chart with percentage blue light of various light sources] > [19:04] [...] but considering that our eyes can withstand the intensity of sunlight, which is far far greater than any normal artificial light source, and also has a lot of blue light, and ultraviolet, which definitely is harmful, I think the 'blue light' thing is just fear-mongering. If someone can point to some verified, peer-reviewed research supporting this, and not a dodgy website, I'll consider changing my stance. In any case, the high flexibility of LED technology means it can be tuned in pretty much any way we like. The research on the harm of blue light is out there -- For example, one of the comments links to "Effects of blue light on the circadian system and eye physiology" [0]. (only partially read at this point - I don't know if this paper gets into the mechanism of damage done by blue light, as I understand it...) The sun hangs high in the sky and casts light on everything. We never need to look at the sun directly, we use the sun's light indirectly, after it bounces off of things. The atmosphere scatters the sun's blue light before it gets to us [2]. Artificial lights hanging on poles emitting photons we can't avoid having beamed directly into our eyes... Blue photons have relatively higher energy levels, and different physiological effects, than orange photons... [note to self: expand on this.] The preceding video was about High Pressure Sodium lights, which I thought was good too: https://www.youtube.com/watch?v=U1dMlVwUsrA https://www.youtube.com/watch?v=U1dMlVwUsrA My transcription of the video's faulty conclusion (italics added): > To conclude: although the High Pressure Sodium light is very efficient, its primary output color is misaligned with our nighttime visibility. Only about 1/4 of its light is actually effective at stimulating the cells in our eyes. Although the cool color temperatures of many LED replacements is harsh and aesthetically displeasing, studies have shown that it is not only more efficient, but also makes driving at night safer. There is, however, the potential for greater circadian rhythm disruption and larger amounts of skyglow, using these bluer light sources. > Still, it seems clear that the High Pressure Sodium is on its way out. Advancements in LED technology are happening at a breakneck pace. Just 10 years ago, they weren't seen as viable, but today even the least efficient of LED replacements ends up emitting the efficiency of High Pressure Sodium once scotopic light output is considered. > As it stands in 2018, we are faced with the choice of efficiency over aesthetics. I'm pretty sure I'd enjoy roadways lit with relatively-warm 3000K LEDS, and these also wouldn't disrupt sleep much. But you can save a lot more energy, and potentially have safer roadways, with 5700K lighting. > Either way, it seems clear that LED technology will very soon overtake the tried-and-true High Pressure Sodium lamp, just as the High Pressure Sodium itself replaced the mercury-vapor lamp. And in 40 or 50 years, who knows what technology might light our roadways. [0] https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734149/pdf/mv-v22-61.pdf https://www.ncbi.nlm.nih.gov/pmc/articles/PMC4734149/pdf/mv-... - "The radically different power spectrums can look similar when viewed directly by the eye, irrespective of how much blue emission is present." [1] https://www.youtube.com/watch?v=wIC-iGDTU40&lc=Ugx6MYdsMY6I_G2rbU94AaABAg https://www.youtube.com/watch?v=wIC-iGDTU40&lc=Ugx6MYdsMY6I_... [2] https://en.wikipedia.org/wiki/Rayleigh_scattering#Cause_of_the_blue_color_of_the_sky https://en.wikipedia.org/wiki/Rayleigh_scattering#Cause_of_t... edit: this page has a discussion of drop-sag lights vs. proper fully-shielded lights: http://www.skykeepers.org/good-bad-lights-cv.html http://www.skykeepers.org/good-bad-lights-cv.html

efa 6y ago

North Korea must be swimming in insects. https://i.imgur.com/S1mrMKN.jpg https://i.imgur.com/S1mrMKN.jpg

DocTomoe 6y ago
They also use pesticides pretty liberally. But there is a somewhat interesting paper on North Korean entomology: https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3554493/ https://www.ncbi.nlm.nih.gov/pmc/articles/PMC3554493/

emptybits 6y ago

> Also good is using more LED street lamps that focus the light where we need it, Focusing light where needed is good. Using LEDs, as we do now, has downsides though. LED lighting in cities is making astronomy and astrophotography and even animal life worse in some cases.[1] Traditional sodium vapour lights pollute around a wavelength of 589 nm.[2] That's the yellow/orange sky you used to see in the sky around cities. In theory, if you filtered out that wavelength 10 years ago, you'd be able to eliminate a lot of light pollution. But today, with more LED lighting, the pollution tends toward white/blue. This is "nicer" in some objective and subjective ways. e.g. colour accuracy. But it's a bitch to filter out, without also removing all the white and broad spectrum we want to see in the features of the night sky. Animals are also sensitive to white and blue light emitted by modern LEDs, and the NatGeo link and others go into why this can be a bad thing, compared to "old fashioned" lighting methods, inefficient as they are. [1] https://www.nationalgeographic.com/news/2017/11/light-pollution-energy-LED-bulbs-spd/ https://www.nationalgeographic.com/news/2017/11/light-pollut... [2] https://www.peterzelinka.com/blog/2019/8/light-pollution-filters-for-astrophotography https://www.peterzelinka.com/blog/2019/8/light-pollution-fil...

mrpopo 6y ago
We made LED lighting white because we wanted it. We can make yellow LED lighting as well. This should be suggested to city councils, if changing the wavelength would be beneficial to insects with no downsides.
- TACIXAT 6y ago
  I'd be so stoked for red street lights. They don't mess up your vision at night.
  - emptybits 6y ago
    Indeed. Nor does red light mess as much with animal (incl. human) physiology and behaviour and waking cued by white/blue/daylight. Potential small (safety?) downside: red light illumination does greatly reduce colour discrimination at night versus white light.