It’s time to cast your vote! A planet-wide election is taking place. The two contenders are Earth and global warming. There are no debates to watch or ballots to fill out. Voters will make their choice with the simple flick of a switch—a light switch, that is. Turning lights off is a vote for Earth.

On Saturday, March 28, people and businesses across the world will take part in Earth Hour. The event started two years ago in Australia. At that time, about 2 million people turned off their lights. Last year, 50 million people switched off their lights for Earth Hour. Places such as the Golden Gate Bridge in California, the Colosseum in Rome, and the Opera House in Sydney, Australia, went dark. This year the sponsor, the World Wildlife Fund (WWF), hopes that 1 billion people will vote for Earth.

Turning off lights for one hour won’t fix global warming. Rather, Earth Hour is a symbolic event. It’s designed to send a message to political leaders around the world. Supporters want those officials to do something about the global warming that is causing climate change.

Earth Is Heating Up
Global warming is an increase in Earth’s average temperature. It is caused by greenhouse gases building up in Earth’s atmosphere. Those gases, such as carbon dioxide and methane, trap the sun’s energy in the atmosphere. That prevents Earth’s heat from escaping into space. Instead, the greenhouse gases act as a barrier in the atmosphere, and heat bounces back to Earth.

Greenhouse gases keep Earth warm enough to support life. But today most scientists think too much of those gases are building up in the atmosphere. Where are they coming from? Many come from nature. But some are produced by human-made things, such as cars and power plants, which burn fossil fuels. As Earth’s temperature rises, climate change occurs. Polar ice caps start to melt, sea levels rise, and weather and habitats around the world adjust.

Have Fun in the Dark
Earth Hour will take place from 8:30 to 9:30 p.m. local time. That means wherever you live, Earth Hour will start at 8:30 in the evening. During that time, people and businesses in over 80 countries will turn off all lights—except those needed for safety—in their homes and buildings. In December, people from the WWF will speak to world leaders at the Global Climate Change Conference in Copenhagen, Denmark. They hope to help leaders make decisions about how to fight global warming.

What will everyone do in the dark for an hour? Many people already have plans. Some plans include having candle-lit dinners, going on treasure hunts, taking a walk, or gazing at the stars.

“Turn off your lights, celebrate the planet, enjoy the moment, and cast your vote for Earth,” says Andy Ridley, the executive director of Earth Hour. (You wouldn’t want to vote for global warming, would you?) It’s not a secret ballot, so how will you vote?