“A significant fraction of thru-hikers reach Katahdin, then turn around and start back to Georgia. They just can’t stop walking, which kind of makes you wonder.”

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

The one thing we have in common with all other living things is that for nearly four billions years our ancestors have managed to slip through a series of closing doors every time we needed them to.

Still, I never really mind bad service in a restaurant. It makes me feel better about not leaving a tip.

That’s the trouble with losing your mind; by the time it’s gone, it’s too late to get it back.

Australians are very unfair in this way. They spend half of any conversation insisting that the country’s dangers are vastly overrated and that there’s nothing to worry about.

Everywhere throughout New England you find old, tumbledown field walls, often in the middle of the deepest, most settled- looking woods- a reminder of just how swiftly nature reclaims the land in America.

When you consider it from a human perspective, and clearly it would be difficult for us to do otherwise, life is an odd thing. It couldn’t wait to get going, but then, having gotten going, it seemed in very little hurry to move on.

More than 300 million people in the world speak English and the rest, it sometimes seems, try to.

There is always a little more toothpaste in the tube. Think about it.

When I was growing up I used to think that the best thing about coming from Des Moines was that it meant you didn’t come from anywhere else in Iowa. By Iowa standards.

I became quietly seized with that nostalgia that overcomes you when you have reached the middle of your life and your father has recently died and it dawns on you that when he went he took some of you with him.

Tune your television to any channel it doesn’t receive and about 1 percent of the dancing static you see is accounted for by this ancient remnant of the Big Bang. The next time you complain that there is nothing on, remember that you can always watch the birth of the universe.

You don’t have to know anything about baseball to respond to Babe Ruth because he’s just this magnificent human being.

So here I am, my affections torn between a postal service that never feeds me but can tackle a challenge and one that gives me free tape and prompt service but won’t help me out when I can’t remember a street name.

We may be all there is. It’s an unnerving thought that we may be the living universe’s supreme achievement and its worst nightmare simultaneously.

Physicists are atoms’ way of thinking about atoms.