We’ve all seen this map. This is why if you’re reading this, chances are better than even that you can’t see the Milky Way at night. For the entirety of human history, everyone everywhere could see more than a thousand stars on a clear dark night. That’s wrecked now, for most of the developed world, thanks to light pollution. And it only took us a couple of generations to do it.
But it would be very easy to unwreck. Our natural heritage in the sky is being washed out by wasted light. Fighting light pollution isn’t about doing away with artificial lighting, it’s about doing away with stupid artificial lighting. Full cutoff bulbs that illuminate roads, sidewalks, parking lots, and front porches contribute very little to light pollution. The problem is unshielded bulbs, which send 50% of their photons up into space. All they’re doing is lighting up the bottoms of birds, bats, airplanes, and satellites. And, not coincidentally, washing out our starscapes.
The bottom line is that unshielded bulbs are wasteful; that’s an awful lot of kilowatt hours we’re sending out into space. Putting a full-cutoff hood on a light doesn’t make it use less energy, but it at least directs all the energy where it’s needed. Or you could use a reflective hood and a bulb that eats half as much power and still achieve the same illumination.
If you want to help fight pollution, there is a very cool project going on now called Globe at Night 2010. All you have to do is go outside, find the constellation Orion, compare your naked-eye view with the GaN magnitude charts, and report your observation using their online form. You can also compare your result with those of thousands of people around the world. If you’re an amateur astronomer, just using the magnitude charts should give you a better idea of how to assess the naked-eye limiting magnitude at your observing site.
Globe at Night 2010 is running from March 3-16, so even if it’s the rainy season where you are, you will hopefully get at least one clear night. It’s fun, it’s easy, you help the human endeavor, and you learn a little something. Go to it!