Physics is really nothing more than a search for ultimate simplicity, but so far all we have is a kind of elegant messiness.

Being a pessimist is just such a gloomy way of looking at things, so I have to hope for the best - life wouldn't be worth living if we didn't have hope. And I also do think that human beings often do do wonderful, correct, brilliant things. So, on balance, I'd like to be optimistic about the future.

Des Moines is like your typical American city; it's just these concentric circles of malls, built outward from the city.

Because time moves more slowly in Kid World ... it goes on for decades ... It is adult life that is over in a twinkling.

Every twenty minutes on the Appalachian Trail, Katz and I walked farther than the average American walks in a week. For 93 percent of all trips outside the home, for whatever distance or whatever purpose, Americans now get in a car. On average the total walking of an American these days - that's walking of all types: from car to office, from office to car, around the supermarket and shopping malls - adds up to 1.4 miles a week, barely 350 yards a day.

I was heading to Nebraska. Now there's a sentence you don't want to say too often if you can possibly help it.

There is no such thing, incidentally, as one kudo.