This is awesome. Our skies will get better over our lifetime

[Charles Dunlop]

http://www.bbc.co.uk/news/technology-22292129

[Harry Armstrong]

I read a really interesting section of the VDOT street lighting code. Basically they try really hard to eliminate glare and light pollution. However, that goal competes with the goal to use fewer fixtures. If you have full-cutoff lamps on a traditional HPS ballast, they only illuminate a small portion of road instead of an entire interchange, for example. That is why they end up with quite a bit of LP.

If this LED stuff is used properly it could be really good. However LEDs are also bad because they tend to produce light across the entire spectrum. At least with sodium lamps the maximum output is only at certain wavelengths.

Ironically, I suspect if we could all live 200 years we would see a very different, very much darker planet. Energy is going to be the main problem of the next few hundred years. I suspect people will be forced to think hard about energy usage someday, and the skies will get dark again. I doubt I will be around to see it though.

[Charles Dunlop]

There is no doubt we will have to stop wasting energy by shooting it into the sky and space.

Not sure I understand the point about wavelenght spectrum. If LED use less energy to produce a certain luminance available to the human eye, then what difference does that make?

[Harry Armstrong]

What I meant is that LED lamps tend to produce light across the visual spectrum. If the lighting is not carefully cut off so that it does not go into the atmosphere, it is impossible to filter out. It produces light pollution at every wavelength.

By contrast, certain lamp types like low pressure sodium produce light at only a particular wavelength. This is trivial to filter out of our images.

http://www.lamptech.co.uk/Documents/SO%20Spectral.htm

[Ian G]

That's a long-long time away. Right now, I was driving on the Interstate. Bright Sun, all the flood lights are still on at 8:30 in the morning. I suspect they'll stay on all day long. So much for cutting light pollution because of the high energy cost...