Don’t be alarmed if your city, town, or neighborhood, goes dark from 8:30 - 9:30 PM local time tonight (March 24). The blackout is not due to a sudden electricity outage, but a voluntary gesture to celebrate Earth Hour, which will be observed worldwide and include iconic landmarks like the Eiffel Tower, the Empire State Building, and the Sydney Opera House. The simple action, designed to demonstrate what can be achieved if we all unite to help reverse climate change, is the brainchild of the Australian chapter of the World Wildlife Fund (WWF).