Lights Out for Earth Hour Participants

People from around the world will celebrate Earth Hour on Saturday from 8:30 to 9:30 p.m.

Participation is easy: just flick off your lights. If you're feeling saucy, go ahead and turn off your TV and laptop, too.

Earth Hour began in 2007 in Sydney, Australia when 2.2 million people turned off their lights for one hour to combat climate change. Now the World Wildlife Foundation event has almost 5 million supporters and a global network of more than 100 countries. In 2010, 128 countries and territories participated.

Local landmarks participating in the event include the National Cathedral, Baltimore City Hall and the National Aquarium.