Recently I read a blog post about a couple who had sold their sprawling empty nest and car after retirement and moved into downtown Seattle. They extoll the joys of urban living and their solicitous neighborhood shopkeepers. They exchange "good mornings" with the people we pass everyday on our way to work.

That seems to be true of every city I've spent time in other than New York.

New York City is chock full of human beings. A tiny thing like leaving the lobby at work means walking past one construction worker, three security guards, four jaded women standing in a gaggle at the front door, one wan and skinny-jeaned drama queen on a cell phone, and a confused babushka wondering what the hell happened to her dear old Chelsea. I've a theory that transportation time can be measured by people-distance: walking a block past a dozen brownstones with a hundred swaming denizens takes the same effort as driving or biking past the same number in lawn-bordered colonials.

Officially, we have 8.2 million people in New York. C(8.2 million, 2) is about 672 trillion possible encounters. It's too many people to make human contact with everyone whose path I cross. And so I glare my way through most of my days.