Remember when you could see stars? Have your kids ever seen the Milky Way? For some reason we have, as a society, decided we need to keep the bulbs burning in our stores and offices when they're empty, and illuminate things that don't really need to be seen at night - like tall buildings. Too many of our outdoor lights waste energy lighting up dust in the air and the underside of the clouds.

That's what causes the skyglow captured in the photo at left, and erases the stars. It is costing us billions in wasted energy, contributing to climate change and divorcing us from our heritage in the night sky (right).

For one hour beginning at 8:30 local time Saturday night, from Baltimore's City Hall to the Pyramids of Egypt, the lights will go out in a global expression of concern for our planet.

"Not only does it help reduce carbon emissions, but [it] encourages citizens to reflect on ways they can help save on energy costs and make Baltimore and their environment even greener," said Khalil Zaied, head of Baltimore's Bureau of General Services.

In addition to City Hall, the lights will go out for an hour downtown at the city's Abel Wolman Municipal Building, the MECU Building, the Charles Benton Building, the People's Court, the War Memorial Building and Fire Department Headquarters.

The global event is called Earth Hour, and it's being organized by the World Wildlife Fund. This will be the third year of its observance, and it continues to grow. This year, 2,400 cities in 82 countries are participating, up from 400 cities in 35 countries last year. In addition to Baltimore, U.S. cities taking part include Washington DC, Las Vegas, Los Angeles, New York City and Nashville, Tenn.

Also going dark for an hour will be the Acropolis in Athens, Rockefeller Center and the Chrysler Building in New York, and the Gateway Arch in St. Louis. In London, the bright lights of Piccadilly Circus will go out for an hour, and Marriott Hotels around the world will also switch off their outdoor lights.

Of course, everyone is invited to take part, switching off their porch lights and other unneeded illumination for an hour wherever they are. But one hour of darkness at a relative handful of locations won't be much more than a symbolic vote in favor of more sensible energy use and more rational illumination ordinances.

What the Dark Sky movement has been about for many years has been a campaign to educate the public and their policy makers about the needless waste of energy for illumination, which has the added effect of erasing the night sky by allowing unnecessary light to shine sideways, or up into the sky where it's not needed.

Dark sky advocates agree that some nighttime illumination is needed for safety and security. But they argue that too much of that lighting is badly designed, shining on things that don't need to be illuminated, instead of being concentrated on the things that do.

For example, light from a streetlight that beams into your upstairs bedroom window is not helping anyone see the street (left). That light is wasted and intrusive. Such lights should be aimed and shielded (right) so that the light goes only where it's needed. That would not only prevent light intrusion into your bedroom; the proper engineering of the light fixture would also require less energy, since less light would be needed to do the job. 

In Baltimore County, the owners of Bengies Drive-In Theater argue that unnecessary light intrusion from a neighboring business is causing problems for their movie-going customers. Better lighting design could have avoided the problems and saved money and energy.

Likewise, a spotlight shining onto a billboard from below the sign sends much of its light into space, lighting up the bellies of migrating birds and washing out the night sky. Mount that light on the top of the billboard, and shine it down onto the ad only, and you have a cheaper, more sensible plan.

Many cities have enacted good, strong outdoor lighting ordinances, some with the help of the International Dark Sky Association. What's needed is for more local governments to do the same, and for all those who enforce these ordinances to do their jobs.