Save the planet, turn off your electricity so you can't watch the bombings of Libya on television...
David Cameron has backed an hour-long blackout to raise awareness of environmental issues.
The Prime Minister recorded a YouTube message supporting Saturday's Earth Hour, when millions of people are expected to switch off lights for 60 minutes.
He said: "Sharing responsibility holds the key to fighting climate change."
Mr Cameron pledged to make the coalition Britain's "greenest-ever government" in the fight against climate change.
But he added: "It will be the choices we make as individuals which will mean the difference between success and failure.
"That's what Earth Hour is all about - millions of people all over the world coming together to switch off their lights, tackle climate change and protect our natural world.
"It is a huge symbol of global solidarity, an inspiring display of international commitment."
Homes, businesses and landmarks in 130 countries are expected to switch off lights for an hour from 8.30pm in Saturday.
Environmental pressure group WWF's head of campaigns, Colin Butfield, said: "It's great to hear the Prime Minister reiterate an ambition to lead the UK's greenest-ever government. There is substantial and serious work to do if this aspiration is to become a genuine reality.
"The millions of people taking part in Earth Hour are not only demonstrating their personal commitment, but also sending a strong message to government to call for urgent and sustainable action on climate change."