For 12 nights, across a wintry desert, a brilliant star was said to have guided three Eastern kings to a little town in Judea.
Good thing it happened 2,000 years ago because today the hazy glow over most metropolitan areas would make a clear star sighting a little less certain. Over Chicago, it would be nearly impossible.
On a very good winter night, in a dark rural area, about 2,500 stars should be visible to the naked eye.
I asked astronomer Mark Hammergren at the Adler Planetarium how many stars can usually be seen over downtown Chicago.
“About 10 or 12,” he said.
The cause is “light pollution”–the excessive amount of light that is thrown into the skies by street lamps and commercial lighting plus (at this time of year) a few thousand lawn Santas and rooftop angels.
According to the International Dark-Sky Association–an educational organization with members from more than 70 countries–an estimated $1 billion worth of light in the U.S. is annually misdirected upwards. The result is that nine out of 10 Americans can’t see much more than the Big Dipper or Orion’s belt.
Astronomers aren’t alone in needing dark skies.
Turn the season back to fall or forward to spring, when tens of thousands of migratory birds fly nightly over Chicago and Lake Michigan.
Before dawn, they search for land and flock from the lake into the city seeking shelter.
Some shelter. As they approach, their normal guiding system of the moon and stars gets literally jammed by the decorative lights on downtown skyscrapers. According to Doug Stotz, an ornithologist at the Field Museum, thousands of birds can die in one night thudding against the walls or exhausting themselves by circling the buildings.
But in an urban environment, we just can’t turn the lights off for the sake of birds or stars. Or can we?
For the birds, at least, there’s already a solution. It’s called, simply enough, the “Lights Out” program and has been in effect for about three years, under the umbrella of Mayor Richard Daley’s nature and wildlife committee. Working through the Audubon Society and the Building Owners and Managers Association of Chicago, the committee asks that the upper-floor lights be turned off voluntarily in buildings of 40 floors or more after 11 p.m. during the two migration seasons.
Although firm statistics are hard to come by (migration numbers vary year to year, and those pesky gulls and vermin remove lots of fallen birds), there is no question, according to Stotz, that the effort is working. In fact, through other more localized studies, he has found that four times fewer birds will fly into a dark wall than one drenched with light.
But what about darkening the entire sky? The problem is that the glow overhead is created by diffuse sources and many more lights than on a few central tall buildings. Just Chicago streetlights alone number over 175,000.
Reducing light pollution is unfortunately not a priority for a town that believes bright lights equal a big city. But to be fair, City Hall is not unaware of the issue. Brian Murphy, the deputy commissioner for electricity, said his department has already retrofitted most of the lighting over arterial roads with new fixtures and covers that keep much of the light down on the ground, where it belongs.
However, at the same time, the city has embarked on a pilot program to install new residential lighting that hangs over the street and sidewalk. Although aesthetically pleasing and nice for pedestrians, the lighting is also twice as bright (at 250 watts plus an extra 50 watts over the sidewalks) as the old 150-watt bulbs.
Compare that with a city that is moving in the opposite direction–Calgary, in Alberta Canada. There, 47,000 150-watt bulbs are being replaced by 100-watts–saving $1.5 million a year in electricity in the process.
But one small change in Chicago’s light has made local astronomers a little happier. The city has retrofitted and reduced the lighting near the Doane Observatory, situated between the Planetarium and Lake Michigan.
For the rest of the city, though, it will take some serious rethinking to bring back the night. It would be nice to have more than one spot in Chicago to catch a glimpse of an Eastern star.
