Once upon a time, it was easy to fall off the map. You saved your money. You bought a ticket. You told your parents you’d be checking in, gave them a hug, and off you went. A few weeks later, you scribbled a postcard if you remembered. If you were feeling verbose, you bought a tissue-thin aerogram and wrote a letter in your tiniest handwriting. If weeks turned into months, you went to an underlit, Dickensian place full of grimy booths called a telephone center and sat down for a brief, expensive, shouted phone call to the folks back home. But at no point did you feel compelled or obliged to let anyone know where you were all the time, or even most of the time. I started writing this piece on a cross-country flight a few weeks ago. We are still generally unreachable when in mid-air, although 1) this may change and/or is already changing and 2) your nearest and dearest tend to know where you are when you’re on that plane, even if you can’t text, email or actually call one another. I wrote a bit more when I was on a Megabus trip from New York City to Syracuse. The wi-fi worked pretty well, with the occasional slow patch as we skirted the Catskills. Most of the other passengers appeared to be college students, heading back upstate after a weekend in the city. Most of them wore ear buds connected to smartphones; tethered even as they slept to music, to friends, to news. [...]