And lit some candles:
Here is some information on Earth Hour, care of the Bigpond News site:
Sydney's Opera House and Harbour Bridge fell into darkness on Saturday night as millions of lights were switched off across the city, kicking off a global energy-saving marathon. A swathe of homes and businesses also killed the lights at 8.30pm (AEDT) for 'Earth Hour' in an effort to lower the planet's carbon footprint and raise awareness of the environment.
Harbour ferry horns blared to signal the rolling event, which began in New Zealand, Fiji and Australia, and will wrap up 25 hours later in Apia, Samoa, at 6.30pm (AEDT) on Sunday. Supporters clasping candles gathered at city viewpoints to watch the spectacle and photograph Sydney's CBD before and after.
Earth Hour is supported by 4,000 cities in a record 125 countries and includes 1,200 famous landmarks. Egypt's Pyramids and Sphinx, the Trevi Fountain and Tower of Pisa in Italy will also take part, led by a five-minute blackout of the Eiffel Tower. For the first time this year, the Forbidden city in Beijing will also be taking part, along with 20 cities across China, despite the country's resistance at Copenhagen.
Now run by the WWF, Earth Hour began in Sydney in 2007 when 2.2 million people switched off the lights in their homes, offices and businesses for 60 minutes to make a point about electricity consumption and carbon pollution. The campaign went global the following year, and it has now harnessed support from a raft of multinational companies including Google, Coca-Cola, Hilton, McDonalds, Canon, HSBC and IKEA.