Heads Up, Lights Out Saturday for Earth Hour

Millions of people around the world are expected to go dark for an hour on Saturday, March 29, as part of the World Wildlife Fund’s annual Earth hour. Want to join in? Flip the switch and turn off your lights at 8:30 p.m. Saturday, local time.

"For us the symbolism or turning your lights off will always be important," Earth Hour's executive director Andy Ridley told The Guardian. "But the big thing for us has always been how to push it beyond the hour. The stage we're at now is to make it really easy for people from their handset, tablet or laptop to be able to do something pretty immediate to make a difference. That's the holy grail for us -- building a global collective movement, far beyond the event, where the event becomes a kind of inspiration but the movement is really the essence of it."

This year the WWF launched Earth Hour Blue, a crowdsourcing project for environmental and conservation projects around the world.

Earth Hour was first launched in Sydney, Australia in 2007, as a way to promote conservation and bring attention to global warming. People in more than 150 countries now participate in the event. Here are some of the notable landmarks that plan to observe Earth Hour:

Seattle’s Space Needle, the St. Louis Arch, parts of the Vegas strip, the Empire State Building, Berlin’s Brandenburg Gate, Buckingham Palace, the Burj Khalifa in Dubai and the Kremlin and Red Square in Moscow.

The WWF has mounted a twitter campaign to urge sites including San Francisco’s Bay Bridge, the National Mall and the Alamo to join in.

Photo: Balinese men burn lanterns during Earth Hour at a hotel in Nusa dua on the resort island of Bali on March 23, 2013. Credit: Sonny Tumbelaka/AFP/Getty Images(Mar 28, 2014 02:08 PM ET // by Paul Heltzel)