Lights go out around the world for Earth Hour

For one hour on Saturday starting at 8:30 p.m, local time, cities around the world will send a collective message about conservation and climate change.

Called Earth Hour, the event encourages participants to turn off all non-essential lights for 60 minutes. This year, 7,000 cities in 162 countries are participating.

Organized by the World Wide Fund for Nature, Earth Hour began in Australia in 2007, and has grown exponentially ever since