For the past three years, people all over the world have been observing Earth Hour
on one Saturday evening in March. For one hour, beginning at 8:30PM local time in each time zone, governments, businesses and individuals turn off as many electrical appliances as possible. The Boston Globe has collected some of the most interesting photographs of some major cities before and during Earth Hour.
Check out the Globe's collection of Earth Hour photographs
. With the exception of the first photograph, you can compare the "before" and "during" photographs (all taken at night!) by clicking on the photographs.
(Overview of Hong Kong Island and Kowloon with lights on and off to mark Earth Hour 2010. Photo by Ringo Ma, via WWF)