Did you know that Earth Hour fell on the 24th March this year? This movement, which began in Sydney in 2007 as a 'lights out' movement, has since become the world's largest grassroots environmental campaign. Coordinated by the WWF and other charities, the event encourages all non essential lights to be turned off for one hour, from 8:30pm to 9:30pm. The impressive diffusion of the event can be attributed to the use of social media promotion, and this year 187 countries took part, with 3,000 landmarks and monuments observing the rules of the campaign. Specifically speaking, the Earth Hour twitter account posted 105 posts, which achieved 23,800 interactions and received 3,200 mentions from across Twitter. Importantly, other organisers and influencers also helped the event gain traction, with the likes of Maroon 5 and the Champions League also encouraging fans tosupport the cause.