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.

Cities generate most of the global economy, and most of its energy use, resource demands and climate emissions. How we build cities over the next decades will largely determine whether we can deliver a bright green future.

I think there's a gigantic generation gap in terms of how people understand the Internet and how much they think technology is an important factor in social change.

In almost all city governments in America, the small group of people who don't want change are able to block change.

Cabbies in particular seem to like discussing the fate the Earth.

We get so little news about the developing world that we often forget that there are literally millions of people out there struggling to change things to be fairer, freer, more democratic, less corrupt.

Copenhagen has done a remarkable job creating streets that are focused on bicycles and pedestrians.