Every year on March 29 Earth Hour is celebrated in Australia, US and worldwide.

Earth Hour began last year in Sydney, Australia, as a way to get an entire city to help do something about climate change. A symbolic act, it nevertheless managed to cut individual energy use by a fraction as people across the city shut off the lights.

More than 150,000 individuals and tens of thousands of schools, businesses and other organizations participated this year by shutting out all the lights for an hour between 8 and 9 p.m.

The benefits of the Earth Hour idea are also evident for backyard stargazers, whose view of the night sky is typically obscured by light pollution.