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.

Deep walkability describes a city that is built in such a way that you can move from one area to another on foot, on bicycle, on transit and have an experience that remains a pleasant one, that you feel you are welcome not just in the neighborhood but moving between neighborhoods.

For most people, using the Internet broadens their sense of who 'we' is and actually ends up leaving us in a place of greater compassion and understanding. It leaves us more connected to a larger group of people and more at one with a lot more people in our community.

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

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.

By fundamentally changing how we design the places and systems that enable our daily lives, we can slash emissions way beyond the immediate carbon savings - because our own personal emissions are just the tip of a vast iceberg of energy and resources consumed far from our view.

Clean air and water, a diversity of animal and plant species, soil and mineral resources, and predictable weather are annuities that will pay dividends for as long as the human race survives – and may even extend our stay on Earth.