No matter what else happens, this is the century in which we must learn to live without fossil fuel.

The key to teaching anything is to remember what it was like not to understand that thing. That's a very hard thing to do. Every time you come to understand something you didn't understand before, you are transformed. You become a different person from who you were before. The key to teaching someone else to understand that same thing is to remember your former, untransformed self. If you can do that, I think you can teach anything, even physics.

No matter what else happens, this is the century in which we must learn to live without fossil fuel.

Ludwig Boltzmann, who spent much of his life studying statistical mechanics, died in 1906 by his own hand. Paul Ehrenfest, carrying on the work, died similarly in 1933. Now it is our turn to study statistical mechanics.

Civilization as we know it will come to an end sometime in this century unless we can find a way to live without fossil fuels.