There's no law of physics that says we have to be an unsustainable society - in fact, quite the opposite. The planet's ready to work with us if we're ready to think differently, but we do have to make that jump and start to do things in new ways.

At its very heart, Worldchanging is about using the best of people's new ideas, bringing them together and applying them to the massive problems that we all face.

The planet's biggest problems have to do with sustainability, environmental decline, global poverty, disease, conflict and so forth. Really, they're all interconnected - it's one big problem, which is that the way we're doing things can't go on.

You don't change the world by hiding in the woods, wearing a hair shirt, or buying indulgences in the form of 'Save the Earth' bumper stickers. You do it by articulating a vision for the future and pursuing it with all the ingenuity humanity can muster.

Optimism is a political act. Those who benefit from the status quo are perfectly happy for us to think nothing is going to get any better. In fact, these days, cynicism is obedience.

If mass media, social isolation in the suburbs, alienating workplaces and long car commutes create a bunker mentality, the Internet does the opposite.

Carbon zero simply means that the emissions you are releasing either are zero or balance out to zero.